AU2016273905B2

AU2016273905B2 - Drive control device of semiconductor light emitting elements, droplet drying device, and image forming device

Info

Publication number: AU2016273905B2
Application number: AU2016273905A
Authority: AU
Inventors: Takashi Fujimoto; Chikaho Ikeda; Jun Isozaki; Akira Sakamoto
Original assignee: Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2016-02-05
Filing date: 2016-12-14
Publication date: 2018-05-17
Anticipated expiration: 2036-12-14
Also published as: JP6972521B2; AU2016273905A1; JP2017143240A

Abstract

A drive control device (60) of semiconductor light emitting elements (72) is provided and include: plural current generation units (106) that respectively supply drive currents to plural semiconductor light emitting element groups (74), respectively include reception portions (NI-N4) that receive switching signals (Ss), and control the drive currents according to the switching signals (Ss), each of the semiconductor light emitting element group (74) including at least one semiconductor light emitting element (72); a switching signal generation unit (100) that generates the switching signals (Ss) according to target values of the drive currents and supplies the switching signals (Ss) to the respective reception portions (N1-N4); and a voltage source (112) that is in a serial relationship with the current generation unit (106) and the semiconductor light emitting element group (74). cc o o 1I 0) sD -o rhc DC QIWW 0 W1 cI: I Cl) I A 1 0 IL _j o u I -;A I 0 cc o o LO oC0

Description

COMPLETE SPECIFICATION

FOR A STANDARD PATENT

Name of Applicant: Fuji Xerox Co., Ltd.

Actual Inventors: Takashi Fujimoto and Chikaho Ikeda and Jun Isozaki and Akira

Sakamoto

Address for Service is:
Shelston IP Pty Ltd
60 Margaret Street	Telephone No:	(02) 9777 1111
SYDNEY NSW 2000 CCN: 3710000352 Attorney Code: SW	Facsimile No.	(02) 9241 4666

Invention Title:

Drive control device of semiconductor light emitting elements, droplet drying device, and image forming device

The following statement is a full description of this invention, including the best method of performing it known to us:File: 94701AUP00

DRIVE CONTROL DEVICE OF SEMICONDUCTOR LIGHT EMITTING ELEMENTS,

DROPLET DRYING DEVICE, AND IMAGE FORMING DEVICE

BACKGROUND

2016273905 20 Apr 2018 (i) Technical Field [0001] The present invention relates to a drive control device of semiconductor light emitting elements, a droplet drying device, and an image forming device.

(ii) Related Art [0002] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

[0003] Patent Document 1 (Japanese Patent No. 4461576) discloses an LED light source device including an LED load that includes two or more LED series circuits connected in parallel, each having a plurality of LEDs connected in series, or two or more LED anti-parallel circuits connected in parallel, each having a plurality of LEDs connected in anti-parallel, a power supply unit that supplies power so as to be able to light the LED load, circuit elements that are connected in series to each of the LED series circuits or each of the LED anti-parallel circuits, a comparison unit that detects burden voltages of each of the circuit elements and detects a minimum voltage of the burden voltages of each of the circuit elements, and a control unit that controls the power supply unit such that the minimum voltage of the burden voltages of the circuit elements which is detected by the comparison unit is lower than a forward voltage of an LED array of the LED series circuits or the LED anti-parallel circuits.

SUMMARY [0004] An object of an exemplary embodiment of the invention is to provide a drive control device of semiconductor light emitting elements, a droplet drying device, and an image forming device, which reduce a circuit size, further increase power efficiency, and can supply a drive current more stably even if a load varies, as compared to a case where a current source for drive is provided to each of the semiconductor light emitting elements.

[0005] [1] An aspect of the invention provides a drive control device of semiconductor light emitting elements, including:

a plurality of current generation units that respectively supply drive currents to a plurality of semiconductor light emitting element groups, respectively include reception portions that receive switching signals, and control the drive currents according to the switching signals, each of the plurality of semiconductor light emitting element group including at least one semiconductor light emitting element;

2016273905 20 Apr 2018 a switching signal generation unit that generates the plurality of switching signals according to target values of the drive currents and supplies the plurality of switching signals to the plurality of reception portions, respectively; and a voltage source that is in a serial relationship with the current generation unit and the semiconductor light emitting element group.

[0006] [2] The drive control device according to [1] may have a configuration in which each of the switching signals are a binary digital signal, and the switching signal generation unit generates each of the switching signals by changing at least one of a pulse width and a pulse cycle of the digital signal according to a target value of a drive current for a semiconductor light emitting element group when the semiconductor light emitting element group extinguishes light and emits the light.

[0007] [3] The drive control device according to [2] may further include:

a switching time calculation unit that calculates at least one of the pulse width and the pulse cycle according to the target value.

[0008] [4] The drive control device according to [3] may further include:

a correction unit that corrects at least one of the pulse width and the cycle with characteristics of at least one of: the semiconductor light emitting element groups; the voltage source; the current generation unit; and the switching signal generation unit, which are required for calculating at least one of the pulse width and the cycle by switching time calculation unit.

[0009] [5] The drive control device according to [4] may further include:

a monitoring unit that monitors electro-optical characteristics of the plurality of semiconductor light emitting element groups, in which the correction unit corrects at least one of the pulse width and the cycle according to a monitoring result of the monitoring unit.

[0010] [6] The drive control device according to any one of [1] to [5] may have a configuration in which:

each of the plurality of semiconductor light emitting element groups includes a plurality of semiconductor light emitting elements connected in series, and for each one of the plurality of semiconductor light emitting element groups, the current generation unit includes a switching element having a control terminal in the reception portion, an inductor that is connected to an output terminal of the switching element and is in a parallel relationship with the one of the plurality of the semiconductor light emitting element groups, and a capacitor that is connected in parallel with the one of the plurality of the semiconductor light emitting element groups.

[0011] [7] The drive control device according to any one of [1] to ]5] may have a configuration in which:

2016273905 20 Apr 2018 each of the plurality of semiconductor light emitting element groups includes a plurality of semiconductor light emitting elements connected in series, and for each one of the plurality of semiconductor light emitting element groups, the current generation unit includes a switching element having a control terminal in the reception portion, an inductor that is connected between the switching element and the one ofthe plurality of the semiconductor light emitting element groups, and has an equivalent inductance component of a wire from the switching element to the one of the plurality of the semiconductor light emitting element groups, and a diode which is connected in parallel with the one of the plurality of the semiconductor light emitting element groups.

[0012] [8] The drive control device according to [6] or [7] may further include:

at least one of a current detection unit that is connected between a cathode side of each one of the plurality of the semiconductor light emitting element groups and a ground and detects a current flowing through the one of the plurality of the semiconductor light emitting element groups, and a voltage detection unit that is connected between an anode side of the one of the plurality of semiconductor light emitting element groups and a ground and detects a voltage between both terminals of the one of the plurality of the semiconductor light emitting element groups.

[0013] [9] The drive control device according to any one of [6] to [8] may further include: a clamp unit that clamps a voltage of an output terminal of the switching element.

[0014] [10] The drive control device according to [9] may have a configuration in which the clamp unit includes a detection unit that detects a current flowing through the clamp unit, and in a case where a current detected by the detection unit is more than a given value, operations ofthe plurality of current generation units are stopped.

[0015] [11] The drive control device according to any one of [6] to [10] may further include:

an input current detection unit that detects a current flowing through an input terminal of the switching element, in which, in a case where a current detected by the input current detection unit is more than a given value, operations of the plurality of current generation units are stopped. [0016] [12] The drive control device according to any one of [1] to [11] may have a configuration in which the switching signal generation unit makes timings of each of the plurality of switching signals different among each other and supplies the plurality of switching signals with different timings to the reception portions, respectively.

[0017] [13] The drive control device according to any one of [1] to [12] may have a configuration in which the semiconductor light emitting element is a semiconductor laser, and

2016273905 20 Apr 2018 the switching signal generation unit generates a switching signal such that a drive current that is defined to a current less than a threshold current of the semiconductor laser during a defined period flows before a timing in which the semiconductor laser is changed from an extinguished state to a light emitting state in order for the drive current not to oscillate or not to be delayed at the timing.

[0018] [14] The drive control device according to any one of [1] to [13] may have a configuration in which the semiconductor light emitting element is a light emitting diode.

[0019] [15] Another aspect of the invention provides a droplet drying device including:

a plurality of semiconductor light emitting elements; and a drive control device according to any one of [1] to [14].

[0020] [16] Still another aspect of the invention provides an image forming device including:

an image forming unit that ejects droplets in accordance with image information and forms an image according to the image information on a recording medium; and a droplet drying device according to [15], in which the droplet drying device dries droplets ejected on the recording medium by the image forming unit.

[0021] With the configuration of [1], [15], and [16], it is possible to obtain effects in which a drive control device of semiconductor light emitting elements, a droplet drying device, and an image forming device can be provided, which reduce a circuit size, further increase power efficiency, and can supply a drive current more stably even if a load varies, as compared to a case where a current source for drive is provided to each of the semiconductor light emitting elements.

[0022] With the configuration of [2], it is possible to obtain effects in which control of the drive current is easier since the control can be performed by a digital signal, as compared to a configuration in which a switching signal is an analog signal.

[0023] With the configuration of [3], it is possible to obtain effects in which load of a circuit due to overshoot or the like caused by a negative feedback control is not generated, as compared to a constant current source which uses negative feedback control. The “overshoot” generally means that a signal level (voltage, current) goes to a level higher than a temporarily defined signal level. In contrast to this, falling of the signal level to a level lower than the temporarily defined signal level is called undershoot.

[0024] With the configuration of [4], it is possible to obtain effects in which an initial value of the drive current is determined more correctly, as compared to a case where a pulse width and a cycle are corrected in a state where an individual difference is ignored.

2016273905 20 Apr 2018 [0025] With the configuration of [5], it is possible to obtain effects in which a change of temporal characteristics is reflected, as compared to a case where a pulse width is corrected by using initial characteristics.

[0026] With the configuration of [6], it is possible to obtain effects in which high efficiency is achieved, as compared to a case where the current generation unit is configured without using a switching element.

[0027] With the configuration of [7], it is possible to significantly reduce noise by an operation of shifting a phase using the current generation unit, as compared with a case where the current generation unit includes an inductance element.

[0028] With the configuration of [8], it is possible to obtain effects in which a temporal change of characteristics of the semiconductor light emitting element is reflected to the control of the drive current, as compared to a case where none of the light emitting element current detection unit and the light emitting element voltage detection unit is included.

[0029] With the configuration of [9], it is possible to obtain effects in which a circuit is protected even in a case where the semiconductor light emitting element is short-circuited, as compared to a case where the clamp unit is not included.

[0030] With the configuration of [10], it is possible to obtain effects in which a circuit is protected more reliably even in a case where the semiconductor light emitting element is short-circuited, is compared to a case where the detection unit is not included.

[0031] With the configuration of [11], it is possible to obtain effects in which a circuit is protected even in a case where the inductor is short-circuited, as compared to a case where the input current detection unit is not included.

[0032] With the configuration of [12], it is possible to obtain effects in which a potential variation of a voltage source, a potential variation of the ground, or electromagnetic noise is reduced, as compared to a case where each of the switching signals is supplied to each of the plurality of reception portions in the same timing.

[0033] With the configuration of [13], it is possible to obtain effects in which ringing or delay of a waveform of the drive current of the semiconductor laser is reduced, as compared to a case where the drive current is directly set to a value exceeding a threshold current of the semiconductor laser.

[0034] With the configuration of [14], it is possible to obtain effects in which cost is reduced, as compared to a case where the semiconductor laser is used as the semiconductor light emitting element.

[0035] According to a further aspect of the invention, there is provided a drive control device of semiconductor light emitting elements, comprising:

a plurality of current generation units that respectively supply separate drive currents to a plurality of semiconductor light emitting element groups, respectively include reception

2016273905 20 Apr 2018

Ί portions that receive switching signals, and control the drive currents according to the switching signals, each of the plurality of semiconductor light emitting element group including at least one semiconductor light emitting element;

a switching signal generation unit that generates the plurality of switching signals according to target values of the drive currents and supplies the plurality of switching signals to the plurality of reception portions, respectively; and a voltage source that is in a serial relationship with the current generation unit and the semiconductor light emitting element groups.

[0036] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

BRIEF DESCRIPTION OF THE DRAWINGS [0037] Exemplary embodiment(s) ofthe present invention will be described in detail based on the following figures, wherein [0038] Fig. 1 is a schematic configuration diagram illustrating an example of a main configuration unit of an inkjet recording device according to an exemplary embodiment;

[0039] Fig. 2 is a plan view illustrating an example of a light irradiation surface of a droplet drying device according to the exemplary embodiment;

[0040] Fig. 3 is a block diagram illustrating an example of a configuration of a drive control device of semiconductor light emitting elements according to a first exemplary embodiment; [0041] Fig. 4 is a timing chart illustrating an output of a counter in the drive control device of semiconductor light emitting elements according to the first exemplary embodiment;

[0042] Fig. 5 is a circuit diagram illustrating an example of a switching power supply in the drive control device of semiconductor light emitting elements according to the first exemplary embodiment;

[0043] Fig. 6 is a circuit diagram illustrating an example of a switching power supply in a drive control device of semiconductor light emitting elements according to a second exemplary embodiment;

[0044] Fig. 7 is a block diagram illustrating an example of a configuration of a drive control device of semiconductor light emitting elements according to a fourth exemplary embodiment; [0045] Fig. 8 is a timing chart illustrating an output of a counter in the drive control device of semiconductor light emitting elements according to the fourth exemplary embodiment; [0046] Fig. 9 is a circuit diagram illustrating an example of a switching power supply in a semiconductor light emitting element drive control device according to a modification example of the fourth exemplary embodiment;

2016273905 20 Apr 2018 [0047] Fig. 10 is a block diagram illustrating an example of a configuration of a drive control device of semiconductor light emitting elements according to a fifth exemplary embodiment; and [0048] Fig. 11 is a circuit diagram illustrating a configuration of a drive control device of semiconductor light emitting elements according to a comparative example.

DETAILED DESCRIPTION [0049] Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings. In the exemplary embodiments, a form in which an image forming device according to an exemplary embodiment of the invention is employed in a recording device of an inkjet method will be described as an example.

(First Exemplary Embodiment) [0050] A drive control device of semiconductor light emitting elements (hereinafter sometimes referred to “semiconductor light emitting element drive control device”), an inkjet drying device, and an image forming device will be described with reference to Fig. 1 to Fig.

5.

[0051] First, an inkjet recording device 12 according to the present exemplary embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram illustrating an example of a main configuration unit of the inkjet recording device 12 according to the present exemplary embodiment.

[0052] The inkjet recording device 12 includes, for example, two sets of image forming units 20A and 20B, a control unit 22, a storage unit 30, a paper feed roll 80, an exit roll 90, and a transport roller 99.

[0053] In addition, the image forming unit 20A includes, for example, a head drive unit 40A, a printing head 50A, and a droplet drying device 70A.

[0054] In the same manner, the image forming unit 20B includes, for example, a head drive unit 40B, a printing head 50B, and a droplet drying device 70B.

[0055] Hereinafter, in a case where it is not necessary to distinguish common members included in the image forming unit 20A and the image forming unit 20B from the image forming unit 20A and the image forming unit 20B, a sign “A” and a sign “B” at the end of the symbols are omitted. The sign “A” and the sign “B” indicate the members having the same configuration, but are attached to distinguish positions thereof in the inkjet recording device 12.

[0056] The control unit 22 controls rotation of the transport roller 99 coupled to, for example, a paper transporting motor (not illustrated) through a mechanism such as a gear, by driving the paper transporting motor. An elongated paper (continuous paper) P is wound

2016273905 20 Apr 2018 around the paper feed roll 80 in a paper transporting direction as a recording medium, and the paper P is transported in the paper transporting direction illustrated in Fig. 1 according to the rotation of the transport roller 99. Hereinafter, the image forming device which uses the continuous paper can be referred to as a “continuous paper machine”.

[0057] The control unit 22 acquires image information stored in the storage unit 30, and controls the image forming unit 20A, based on color information of an image included in image information for each pixel. Accordingly, an image corresponding to the image information is formed on an image formation surface on one side of the paper P.

[0058] Specifically, the control unit 22 controls the head drive unit 40A. In addition, the head drive unit 40A causes ink droplets to be ejected from the printing head 50A by driving the printing head 50A coupled to the head drive unit 40A, at an ejection timing of ink droplets instructed by the control unit 22. Accordingly, an image corresponding to the image information is formed on the image formation surface on one side of the paper P.

[0059] In addition, the control unit 22 generates an external control value which is a signal for controlling light emission of a semiconductor light emitting element of the droplet drying device 70A and 70B which will be described below, by using image information of an image which is formed in the inkjet recording device 12.

[0060] The color information of the image included in the image information for each pixel includes information uniquely showing the color of the pixel. In the present exemplary embodiment, the information of the image for each pixel is displayed according to a concentration of each of yellow (Y), magenta (M), cyan (C), and black (K) as an example, but other representation methods uniquely showing the color of an image may be used.

[0061] The printing head 50A includes four printing heads 50AY, 50AM, 50AC, and 50AK respectively corresponding to four colors of a Y color, an M color, a C color, and a K color, and ink droplets which are droplets of a corresponding color are ejected from the printing head 50A. A drive method for ejecting ink droplets in the printing head 50A is not limited in particular, but a known method, such as a so-called thermal method or a piezoelectric method is applied.

[0062] The droplet drying device 70A is configured to include a semiconductor light emitting element drive control device 60A and a semiconductor light emitting element array 76A. The semiconductor light emitting element array 76A includes multiple semiconductor light emitting elements 72, and generates irradiation light which is a thermal source for drying an image formed on the paper P. The semiconductor light emitting element drive control device 60A controls the amount of emitted light of the droplet drying device 70A by turning on or off light emission of each semiconductor light emitting element which configures the semiconductor light emitting element array 76A, based on instruction from the control unit 22. A semiconductor light emitting element which is used as a thermal source according to the

2016273905 20 Apr 2018 present exemplary embodiment is not limited in particular to using, for example, a semiconductor laser or a light emitting diode (LED), but the semiconductor laser is used in the present exemplary embodiment. The semiconductor laser according to the present exemplary embodiment is not limited in particular to using an edge emitting type semiconductor laser, vertical cavity surface emitting laser (VCSEL), or the like. In addition, in a case where the semiconductor laser is used, a wavelength band is selected such that ink droplets are efficiently absorbed.

[0063] In addition, the control unit 22 controls the semiconductor light emitting element drive control device 60A such that an image formation surface on one side of the paper P is irradiated with irradiation light from the droplet drying device 70A, and thereby, ink droplets of an image formed on the paper P are dried by heating (amount of applied heat) of the irradiated light, and the image is fixed on the paper P. In addition, the control unit 22 controls ON or OFF of irradiation of the laser so as to maintain a drive current of, for example, a semiconductor light emitting element, based on the image information. By controlling the quantity of the drive current, light output of the semiconductor light emitting element can be adjusted.

[0064] A distance between the droplet drying device 70A to the paper P is set on the basis of a width of a radiation angle and a radiation region of a semiconductor light emitting element 72 (refer to Fig. 2).

[0065] Thereafter, the paper P is transported to a position facing the image forming unit 20B in accordance with rotation of the transport roller 99. At this time, the paper P is transported such that the other image formation surface different from the image formation surface on which an image is formed by the image forming unit 20A faces the image forming unit 20B.

[0066] The control unit 22 controls the image forming unit 20B in the same manner as the aforementioned image forming unit 20A, and thus, an image corresponding to the image information is formed on the other image formation surface of the paper P. In this way, the inkjet recording device 12 includes two sets of the image forming unit 20A and the image forming unit 20B so as to correspond to two-sided printing of the paper P. Of course, in a case where the two-sided printing is not required, the inkjet recording device 12 may have a form in which only the image forming unit 20A is provided, without the image forming unit 20B.

[0067] In addition, the paper P is transported to the exit roll 90 in accordance with the rotation of the transport roller 99, and is wound around the exit roll 90.

[0068] In addition, the ink includes water-based ink, oil-based ink whose solvent evaporates, and the like, but the present exemplary embodiment is not limited in particular, and any type of ink may be used.

2016273905 20 Apr 2018 [0069] Next, a droplet drying device 70 according to the present exemplary embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram illustrating an example of a light irradiation surface of the droplet drying device 70. The light irradiation surface of the droplet drying device 70 indicates a surface facing the image formation surface of the paper P.

[0070] As illustrated in Fig. 2, multiple semiconductor light emitting elements 72 are arranged in a lattice pattern on the light irradiation surface of the droplet drying device 70, in a paper transporting direction and in a paper width direction orthogonal to (crossing) the paper transporting direction, and are thermally coupled. The number and a disposition shape of the semiconductor light emitting elements 72 which are disposed on the light irradiation surface of the droplet drying device 70 illustrated in Fig. 2 are just examples, and the present exemplary embodiment is not limited to this.

[0071] In addition, in the present exemplary embodiment, a unit of the amount of light which is controlled by the semiconductor light emitting element drive control device the semiconductor light emitting element drive control devices 60A and 60B (refer to Fig. 1, hereinafter, in a case where the semiconductor light emitting element drive control devices 60A and 60B are collectively referred to as a “semiconductor light emitting element drive control device 60”) is set to a semiconductor light emitting element block (semiconductor light emitting element group) 74 in which multiple semiconductor light emitting elements 72 are arranged in a paper width direction. Of course, the present exemplary embodiment is not limited to this, and the amount of light may be controlled by a unit of the semiconductor light emitting element 72. In addition, the arrangement direction of the multiple semiconductor light emitting elements 72 in the semiconductor light emitting element block 74 is not limited to the paper width direction, and may be the paper transporting direction. The semiconductor light emitting elements 72 may be arranged in both directions of the paper width direction and the paper transporting direction.

[0072] In order to secure a total amount of emitted light required for drying, a semiconductor light emitting element array 76 may have a configuration in which multiple semiconductor light emitting element blocks 74, each having the semiconductor light emitting elements 72 arranged in the paper width direction, are arranged in the paper transporting direction, as illustrated in Fig. 2. Fig. 2 illustrates a form in which one semiconductor light emitting element block 74 covers the entire region in the paper width direction, but the present exemplary embodiment is not limited to this, and multiple semiconductor light emitting element blocks 74 may cover the entire region in the paper width direction in a state of being arranged in series. As the amount of emitted light of the semiconductor light emitting element 72 or the multiple semiconductor light emitting element blocks 74 is controlled in accordance with the amount of coating of ink according to the image information, it is possible to perform efficient drying and to prevent energy from being consumed.

2016273905 20 Apr 2018 [0073] As an image is formed and light is emitted toward the paper P which is transported, the droplet drying device 70 dries the ink, using the amount of heat (amount of applied heat) generated by irradiation light. At this time, for example, the control unit 22 calculates the amount of emitted light of the semiconductor light emitting element block 74 in accordance with the amount of ejected ink based on the image information at the time of image formation, sets the drive current (set current value Iset which will be described below) of the semiconductor light emitting element block 74, and controls the semiconductor light emitting element drive control device 60 such that the set drive current basically flows. As a result, drying processing is performed in accordance with the amount of heat proper for the amount of ejected ink.

[0074] Here, the main purpose of the continuous paper machine which uses an aforementioned inkjet print head (printing head 50) is to reduce energy consumption, and a method of intermittently applying drying energy using a droplet drying device around the printed region only when necessary is studied. Hereinafter, there is a case where intermittently applying the drying energy using the droplet drying device in accordance with an instruction of the control unit 22 is referred to as “on-demand irradiation.

[0075] In a case where semiconductor laser is used for drying ink, semiconductor lasers are arranged in the paper width direction, and each semiconductor laser needs to be controlled in accordance with an ink ejection region with power according to the amount of ejected ink, such that the laser supplies drying energy required for the continuous paper machine which quickly feeds paper per unit area in particular. For example, in a case where the semiconductor lasers are arranged at an interval of 1.25 mm in the paper width direction, it is necessary for 400 semiconductor lasers to be individually driven in a paper width of 500 mm.

[0076] Meanwhile, the semiconductor laser is generally driven by a current with a high correlation (in linear relationship) with light output. Thus, a method in which, even in a case of the semiconductor lasers for drying ink, a current source is connected in series to each semiconductor laser, only a predetermined number of series circuits of the semiconductor laser and the current source are connected in parallel to each other and are further connected to the current source, and each semiconductor laser is independently on-demand-controlled at an instructed timing under conditions of a predetermined current, is studied. According to the method, even if there are 400 semiconductor lasers, the semiconductor lasers are divided into groups and each group is connected to one voltage source. Accordingly, a current flowing through each semiconductor laser is adjusted, and thus, the number of necessary voltage sources is decreased. The current source indicates a circuit which makes a designated constant current flow.

2016273905 20 Apr 2018 [0077] Fig. 11 is an example of the semiconductor light emitting element drive control device described above, and illustrated a semiconductor light emitting element drive control device 910 according to a comparative example. As illustrated in Fig. 11, the semiconductor light emitting element drive control device 910 includes a semiconductor light emitting element array in which n semiconductor light emitting element blocks 900-1 to 900-n (in a case of being collectively referred to, simply referred to as “semiconductor light emitting element block 900”, and hereinafter, the same as in other configurations), each having multiple semiconductor light emitting elements 902 connected in series, are connected in parallel to each other. In addition, cathode sides of the semiconductor light emitting element blocks 900-1 to 900-n are respectively connected in series to current sources 906-1 to 906-n which are grounded (connected to ground (GND)) through resistors 904-1 to 904-n. In addition, anode sides of the semiconductor light emitting element blocks 900-1 to 900-n are connected in common to a power supplying unit 908 (voltage source) whose output is variable.

[0078] Furthermore, the semiconductor light emitting element drive control device 910 has a function of measuring a voltage Vd between both terminals of the semiconductor light emitting element block 900 and a voltage Vi between both terminals of the resistor 904, that is, currents 11 to In flowing through the semiconductor light emitting element block 900. The voltage Vd and the voltage Vi are transmitted to a control unit (not illustrated) of the semiconductor light emitting element drive control device 910.

[0079] The control unit of the semiconductor light emitting element drive control device 910 controls the power supplying unit 908 using a control signal Sv, based on the measured value of the voltage Vd, thereby controlling voltages which are applied to the semiconductor light emitting element block 900, the current source 906 connected in series to the semiconductor light emitting element block, and the resistor 904 connected in series to the semiconductor light emitting element block. In addition, the control unit controls the current source 906 using a control signal Si, based on the measured value of the voltage Vi, such that the drive currents 11 to In flowing through the semiconductor light emitting element block 900 have predetermined values. That is, the semiconductor light emitting element drive control device 910 basically controls the semiconductor light emitting element block 900 using feedback (negative feedback) control.

[0080] However, there is room for improvement in the semiconductor light emitting element drive control device 910 from a viewpoint of heating generated by the current source 906 and efficiency reduction. That is, since the multiple semiconductor light emitting element blocks 900 are connected to the same power supplying unit 908, the drive currents of the semiconductor light emitting element blocks 900 which will be set in accordance with the amount of ink that is dried differ from each other between the semiconductor light emitting

2016273905 20 Apr 2018 element blocks 900, characteristics of the semiconductor light emitting element block 900 differ from each other even in the same set current, or the voltages Vd between both terminals of the semiconductor light emitting element blocks 900 become individually different values even in the same drive current, if at least one of the semiconductor light emitting elements 902 which configure the semiconductor light emitting element block 900 and are connected in series is short-circuited.

[0081] Meanwhile, the voltage of the power supplying unit 908 is set such that the current source 906 outputs a current by a set current even in the semiconductor light emitting element block 900 with the highest voltage Vd. For this reason, the current source 906 connected in series to the semiconductor light emitting element block burdens a differential voltage such that the set current flows, and the burden causes the current source 906 to be heated, in the semiconductor light emitting element block 900 with a low voltage Vd among the semiconductor light emitting element blocks 900 connected to the same power supplying unit 908.

[0082] The amount of heat generated in the current source 906 is approximately 10 W in the current source 906 connected to one semiconductor light emitting element block 900 depending on conditions. In this case, a heat sink with a wide heat dissipation area or a water-cooling mechanism is required, and not only is there a great limit in mounting, but also efficiency is reduced, and effects of on-demand irradiation which reduces energy consumption by drying only a portion in which ink exists can be impaired a lot.

[0083] As one method of solving the aforementioned problem, connecting the power supplying unit 908 to each semiconductor light emitting element block 900 is also considered. In this case, the power supplying units 908 have to be arranged by the number of the semiconductor light emitting element blocks 900. In addition, current sources and voltage sources also have to be respectively provided for the multiple power supplying units 908. In this case, control circuits are individually included in each of the current source and the voltage source included in the power supplying units 908, and in addition, a control unit is further required to control all the power supplying units 908 in accordance with printing. Accordingly, a circuit size and cost increase and a mounting problem occurs.

[0084] In addition, as another room for improvement, there is a problem that responsiveness of the power supplying units 908 connected in parallel to the multiple semiconductor light emitting element block 900 is reduced. In a case where the on-demand control of the multiple semiconductor light emitting element blocks 900 arranged in the paper width direction so as to dry ink is performed, for example, if a blank region without ink is changed to a region having ink ejected on the entire surface thereof, a light output of the semiconductor light emitting element block 900 is changed from zero or an output close to zero to a maximum output or an output close to the maximum output. Accordingly, a load

2016273905 20 Apr 2018 current of the power supplying unit 908 is also changed from zero or a current close to zero to a maximum current or a current close to the maximum current.

[0085] While the load current of the power supplying unit 908 is increased from approximately zero to approximately a maximum current, the power supplying unit 908 stabilizes an output voltage using feedback control, that is, a current of the current source 906 also reaches a target value by increasing or decreasing the output of the power supplying unit 908 in accordance with an increase or a decrease of the voltage Vd. However, at this time, ringing, a rising delay, overshoot, or the like is generated, and thus, a burden of the current source 906 increases. In contrast to this, a problem can occur in which a constant current is not able to be maintained due to a decrease of a voltage between both terminals of the current source 906.

[0086] If a voltage is slightly excessive, only a voltage that the current source 906 handles is temporarily increased, and thus, there is no problem for driving the semiconductor light emitting element block 900. However, if a voltage is excessively insufficient, the current source 906 is not able to maintain a current, and, for example, in the head of ink ejection region of the paper P, a light output of the semiconductor light emitting element block 900 does not increase to a predetermined value and dry energy can be insufficient.

[0087] In order to solve the aforementioned problem, a method of stabilizing transient characteristics by increasing decoupling capacitance of an output of the power supplying unit 908 is used. However, if the decoupling capacitance increases, a phase margin is reduced, and in contrast to this, control can be destabilized due to negative feedback control. In this way, as long as the power supplying unit 908 is controlled by using the negative feedback control, an excessive voltage change is difficult to avoid.

[0088] As described above, there is room for improvement of the semiconductor light emitting element drive control device 910 from a viewpoint in which it is necessary that loss of the current source 906 is reduced, a drive current of each of the semiconductor light emitting element blocks 900 (semiconductor light emitting elements 902) can be controlled, and a predetermined current flows through each of the semiconductor light emitting element blocks 900 even though a load current changes.

[0089] Thus, the present invention employs a configuration in which only a power supply component is disposed in each semiconductor light emitting element block without a control unit, a control unit is concentrated on one unit, and multiple power supplies are arranged at a high density and furthermore individually controlled. At this time, the power supply is configured by a switching regulator, and thus, hereinafter, the power supply is referred to as a “switching power supply”. The switching regulator can control one power supply using only a switching signal of a switching transistor, all control signals are disposed in the switching

2016273905 20 Apr 2018 power supply from the control unit, and the control unit is concentrated on one unit or several units, and thus, the control unit is simplified.

[0090] That is, since control is concentrated and only the power supply component is disposed in each semiconductor light emitting element block without a control unit, the switching power supplies are arranged by the number of semiconductor light emitting element blocks. Accordingly, even if terminal voltages of the semiconductor light emitting element blocks are different from each other, each semiconductor light emitting element block is driven at an optimum condition, and thus, a burden of the power supply can be reduced. In addition, a control unit of the switching power supply is not only provided in each switching power supply, but also intensively disposed, and thus, control is simplified, and the power supply is disposed in each semiconductor light emitting element block.

[0091] Furthermore, in the present invention, components, such as, an inductor, a switching transistor, and the like, other than the control unit are disposed in each switching power supply, instead of individual negative feedback control in each power supply circuit. A switching signal corresponding to the drive current of a semiconductor light emitting element which is a target is intensively generated by a control unit, using a control parameter such as, a set inductance value of an inductor of the switching power supply, a maximum value of a transistor, electro-optical characteristics of a semiconductor light emitting element, or the like, and is supplied to the switching transistors of each switching power supply.

[0092] A control signal of the switching power supply is generated on the basis of the target drive current and the control parameter of the semiconductor light emitting element block. In addition, control accuracy is maintained by reflecting an actual measurement value of characteristics which can be concentrated before variation of the component, variation of the semiconductor light emitting element, or the like is generated at the time of maintenance, to a correction unit.

[0093] In addition, by reflecting variation over time such as, characteristics of a semiconductor light emitting element, degradation of a component being used, failure, or the like, to the correction unit, for example, by monitoring and correcting a terminal voltage of a resistor connected in series to the semiconductor light emitting element, the control accuracy is also maintained with respect to the variation over time, and furthermore, processing such as, warning on parameter abnormality or stopping can also be performed if necessary.

[0094] In this way, in the present invention, a load or a used component is determined in advance, and thus, feedforward control is performed by using the control parameter. Since a negative feedback control is not used, an excessive variation is suppressed, and even in a case where a load current is increased from a minimum to a maximum, the control is performed by using a predetermined control parameter, and thus, an excessive variation is reduced to a minimum.

2016273905 20 Apr 2018 [0095] Next, the semiconductor light emitting element drive control device 60 according to the present exemplary embodiment will be described in more detail with reference to Fig. 3 to Fig. 5.

[0096] Fig. 3 is a block diagram of the semiconductor light emitting element drive control device 60 according to the present exemplary embodiment. As illustrated in Fig. 3, the semiconductor light emitting element drive control device 60 is configured to include a switching signal generation unit 100, n semiconductor light emitting element blocks 74-1 to 74-n, switching power supplies 106-1 to 106-n which are provided in correspondence with each semiconductor light emitting element block 74, a coefficient calculation unit 108 (correction unit), a switching time calculation unit 110, a drive power supply 112 (voltage source), and a control power supply 114.

[0097] The semiconductor light emitting element block 74 is a module configured with multiple semiconductor light emitting elements (semiconductor lasers in the present exemplary embodiment) 72 connected in series to each other in the paper width direction, and generates irradiation light as a heat energy source for drying an image formed on the paper P, as described in relation to Fig. 2.

[0098] The switching power supplies 106-1 to 106-n are switched on or off by switching signals Ss1 to Ssn which are transmitted from the switching signal generation unit 100, and furthermore, output drive currents with magnitudes according to the switching signals Ss1 to Ssn to corresponding semiconductor light emitting element blocks 74. The switching power supplies 106 will be described below in detail.

[0099] The switching signal generation unit 100 is configured to include n shift registers (referred to as “SR” in Fig. 3) 102-1 to 102-n corresponding to each semiconductor light emitting element block 74, and n counters 104-1 to 104-n.

[00100] The shift registers 102 are buffers which temporarily store a switching time signal St indicating switching times ts1 to tsn which are calculated by the switching time calculation unit 110 and are times in which the respective switching power supplies 106 corresponding to the respective semiconductor light emitting element blocks 74 are switched on. The switching time signal St includes digital data indicating n switching times ts1 to tsn, and is transmitted in a serial form from the switching time calculation unit 110 to shift registers 102-1 to 102-n together with a transmission clock (denoted by “transmission CK” in Fig. 3). In the present exemplary embodiment, the switching times ts1 to tsn are represented by a form of the number of counts of the corresponding counters 104-1 to 104-n.

[0100] The switching time signal St which is transmitted to the shift register 102-1 is sequentially shifted from the shift register 102-1 to 102-n according to the transmission clock, and information of the times ts1 to tsn corresponding to the shift registers 102-1 to 102-n is retained. If the signal is shifted from the shift register 102-1 to the shift register 102-n by the

2016273905 20 Apr 2018 transmission clock of the shift register 102, setting is completed and the counter waits for preset.

[0101] By doing so, each shift register 102 is set to have a preset value of the counter according to the switching times ts (ts1 to tsn). That is, in the present exemplary embodiment, when the drive current flowing through the respective semiconductor light emitting element blocks 74 or the amount of light of the respective semiconductor light emitting element blocks 74 is set, the switching time ts is set to the shift register in advance, and as switching is performed by using the set value, the semiconductor light emitting element blocks 74 are driven by a predetermined drive current or the amount of light.

[0102] The counter 104-1 to 104-n receive a counter preset signal (referred to as “preset” in Fig. 3) and a counter clock (referred to as “counter CK” in Fig. 3), and generate each of the switching signals Ss1 to Ssn. A reset signal Reset illustrated in Fig. 3 forcibly resets the counter 104.

[0103] Generation of the switching signals Ss1 to Ssn will be described in more detail with reference to Fig. 3. That is, a counter preset value from the corresponding shift register 102 is loaded in the counter 104 at a period of the counter preset signal. If the counter preset value is loaded in each counter 104, an internal decrement value of the counter corresponding to the counter preset value is set, and the internal decrement value decreases from an initial value to zero in accordance with the count clock. The counter 104 outputs a signal of a low level when the decrement value is zero, and outputs a signal of a high level when the decrement value is not zero. That is, if the counter preset value is loaded to the counter 104, the decrement value becomes a value other than zero, the counter 104 outputs a signal of a high level, maintains the signal of a high level during the switching time ts corresponding to the counter preset value, and the counter 104 outputs a signal of a zero level after the switching time ts passes. Referring to Fig. 4, the counter 104 outputs a signal of a high level if the counter preset value is loaded (times t1, t3, and t5 in Fig. 4), and maintains the signal of a high level by the counter preset value while counting the counter clock input to the counter 104. Then, the decrement value becomes zero, and thus, the counter 104 outputs a signal of a low level (times t2 and t4 in Fig. 4), and waits for the next counter preset value. That is, the switching signals Ss1 to Ssn are generated as signals which are switched on by a period of the value that is set to the shift register 102, at a cycle of the counter preset signal (preset), and are supplied to switching elements T of the switching power supplies 106 as switching signals (refer to Fig. 5).

[0104] The switching time calculation unit 110 calculates the switching times ts1 to tsn, and calculates the switching times, using a polynomial function (switching time calculation expression) in which a set current value Iset that is inputted from the outside as an external control value is used as a variable, as illustrated in Fig. 3 in the present exemplary

2016273905 20 Apr 2018 embodiment. The set current value Iset is a value of the current which is calculated on the basis of image information (the amount of ink or the like in each pixel) of an image that is formed, a paper transport speed, or the like by the control unit 22, and drives each of the semiconductor light emitting element blocks 74.

[0105] Coefficients of the switching time calculation expression are calculated by using a parameter (referred to as “semiconductor light emitting element parameter” in Fig. 3) which is input as a control parameter and is related to characteristics of the semiconductor light emitting element, a parameter (“referred to as “power supply circuit parameter” in Fig. 3) relating to a power supply circuit, and a parameter (referred to as “drive parameter” in Fig. 3) relating to drive. The coefficient calculation unit 108 calculates coefficients of the switching time calculation expression from each of the semiconductor light emitting element parameter, the power supply circuit parameter, and the drive parameter.

[0106] Here, specifically, the semiconductor light emitting element parameters represent characteristics of a semiconductor light emitting element, and are parameters of a forward voltage, an internal resistor, and the like as an example, in the case of a semiconductor laser. The power supply circuit parameter relates to a drive power supply 112 or the like which will be described below, and is an input and output voltage of a power supply circuit as an example. The drive parameter relates to a PWM signal which is a standard of the switching signals Ss1 to Ssn, and is a cycle and pulse width of a PWM pulse of the supply source of the PWM signal as an example. The parameters represent characteristics (initial characteristics) in an initial stage of the semiconductor light emitting element, the power supply circuit, and the drive circuit.

[0107] In the present exemplary embodiment, the switching time calculation expression is used as a second-order polynomial relating to the variable Iset. That is, the following (Expression 1) is used as the calculation expression of switching time tsi (Iset) corresponding to the semiconductor light emitting element blocks 74-i (i = 1 to n).

(tsi (Iset))² = tOi + a»lset + p*lset² (Expression 1) [0108] Here, tOi is a constant. The coefficient calculation unit 108 calculates coefficients tOi, a, and β in correspondence with the semiconductor light emitting element blocks 74-i. [0109] Here, the present exemplary embodiment describes the reason why the switching time ts is calculated by using a polynomial function. In the present exemplary embodiment, the switching regulator such as the switching power supplies 106 of Fig. 5 applies energy from the drive power supply 112 to the inductor when the transistor is on, and applies the energy from the inductor to the semiconductor light emitting element when the transistor is off. In addition, when the transistor is on, a current flowing into the inductor increases in proportion to time, and thus, a current flowing through the inductor is proportional to switching time tsi when the switching time tsi passes. At this time, the energy which is applied to the

2016273905 20 Apr 2018 inductor is proportional to the square of the current flowing through the transistor, that is, proportional to the square of the switching time tsi, and thus, energy which is applied to the semiconductor light emitting element in a state of being off is also proportional to the square of the switching time tsi. In addition, energy of the semiconductor light emitting element is obtained by multiplying a voltage between terminals of the semiconductor light emitting element by a flowing current, and the voltage between terminals has a linear relationship (relationship can be approximated to (a + p»lset)) with the current, and thus, the square of tsi is proportional to (a»lset + p*lset²). As a result, if an external control value is the drive current (Iset) of the semiconductor light emitting element block 74, the drive current of the semiconductor light emitting element block 74 is controlled by the counter preset value which is set to the shift register 102, if the parameters are fit.

[0110] The external control value may use the amount of set light emission instead of the set current value, and in a case where the amount of set light emission is used as a variable, the amount of predetermined light emission may be converted into a corresponding set current value. In more detail, in a case where a target is set by the amount of set light emission, a relationship between the drive current which uses a polynomial and the amount of emitted light is set. The drive current with respect to the amount of emitted light given as the external control value is calculated on the basis of the relationship, and thereafter, the switching time ts is calculated from the drive current and may be used as a value which is set to the shift register 102.

[0111] In the present exemplary embodiment, a form in which the switching time ts is calculated by using the second-order function including three control parameters is described as an example, but the present exemplary embodiment is not limited to this, and a form in which the switching time ts is calculated by using the second-order function including one or two parameters among the three control parameters may be used. Furthermore, it is not necessary for the control parameters to necessarily be used, and in this case, the set current value Iset may be converted into the directly corresponding switching time ts.

[0112] In addition, the drive power supply 112 illustrated in Fig. 3 is mainly a voltage source (voltage -Vp) for driving each of the switching power supplies 106, and the control power supply 114 drives portions of the circuit other than the switching power supplies 106. [0113] Furthermore, the semiconductor light emitting element drive control device 60 according to the present exemplary embodiment includes a control unit (light emitting control unit) which is not illustrated, and controls each portion of the switching signal generation unit 100, the semiconductor light emitting element blocks 74, the switching power supplies 106, the coefficient calculation unit 108, the switching time calculation unit 110, the drive power supply (voltage source) 112, and the control power supply 114.

2016273905 20 Apr 2018 [0114] Next, the switching power supply 106 (current generation unit) according to the present exemplary embodiment will be described with reference to Fig. 5. Fig. 5 illustrates an example in which the semiconductor light emitting element blocks 74 are configured by four semiconductor light emitting element blocks 74-1 to 74-4. In each semiconductor light emitting element block 74, multiple (Fig. 5 illustrates 12 semiconductor light emitting element blocks) semiconductor light emitting elements 72 are connected in series, and Furthermore, the respective semiconductor light emitting element blocks 74 are connected in parallel to each other. In the present exemplary embodiment, cathode sides of the semiconductor light emitting element blocks 74 are connected to GND. Furthermore, in the present exemplary embodiment, a semiconductor laser is used as the semiconductor light emitting elements 72, but an LED may be used as described above.

[0115] As illustrated in Fig. 5, each of the four switching power supplies 106-1 to 106-4 is configured to include inductors L1 to L4, smoothing capacitors C1 to C4, reverse current blocking diodes D1 to D4, and switching elements T1 to T4, and one terminal of each of the switching power supplies is connected to each of the semiconductor light emitting element blocks 74. In addition, the other terminal of each of the switching power supplies 106 is connected to the drive power supply 112. The drive power supply 112 receives an alternating current (AC) voltage as an example, and uses the known direct current (DC) power supply including a power factor correction circuit, and thus, detailed description thereof will be omitted.

[0116] The switching signals Ss1 to Ss4 are input to control terminals N1 to N4 (reception portions) of each of switching elements T1 to T4 (Fig. 5 illustrates only the switching signal Ss1 as a representative). The control terminals N1 to N4 are gates if the switching elements are metal oxide semiconductor (MOS) transistors, bases if the switching elements are bipolar transistors, and gates if the switching elements are insulated gate bipolar transistors (IGBTs). [0117] Here, characteristics of the switching power supply 106 according to the present exemplary embodiment will be described. To begin with, according to the switching power supply 106, in a case where the semiconductor light emitting element 72 is short-circuited, the effects of the semiconductor light emitting element blocks 74 on the entire amount of light is reduced. Hereinafter, the present characteristics will be described in more detail.

[0118] According to a simulation result of the switching power supply 106 according to the present exemplary embodiment including the semiconductor light emitting element blocks 74 having 12 semiconductor lasers 72 connected in series, a current flowing through each of the semiconductor light emitting elements 72 is approximately 1.4 A normally, but in a case where two semiconductor light emitting elements are short-circuited, the current increases to approximately 1.68 A which is 1.2 times the current. Here, in a case where the drive current is 1.4 Awhile 12 semiconductor light emitting elements 72 connected in series are normally

2016273905 20 Apr 2018 lighted, a threshold current ofthe semiconductor light emitting element 72 is ignored, but, if the amount of light per the semiconductor light emitting element 72 without a short-circuit is set as a unit, 1.4 A corresponds to the amount of light of 12 semiconductor light emitting elements 72. Then, even in a case where two semiconductor light emitting elements 72 among the semiconductor light emitting element blocks 74 are short-circuited, if the drive current increases to 1.2 times, the amount of light ofthe 10 semiconductor light emitting elements 72 increases to 1.2 times and becomes the amount of light of the 12 semiconductor light emitting elements 72, and the same amount of light as the amount before being shortcircuited is maintained. Actually, it is unlikely that short-circuits simultaneously occur the semiconductor light emitting elements 72, and if one semiconductor light emitting element is short-circuited, a difference between the amounts of light is further reduced before and after the short-circuiting.

[0119] As described above, even in a case where short-circuiting occurs in the semiconductor light emitting elements 72 which configure the semiconductor light emitting element block 74, in the switching power supply 106 according to the present exemplary embodiment, the total variation of drive power of the semiconductor light emitting elements 72 is prevented from being generated for the following reason. That is, when a current flowing through an inductor L (L1 to L4 in Fig. 5) increases, a voltage which is applied to the inductor L is maintained to be constant regardless of the number of short-circuits of the semiconductor light emitting elements 72. Accordingly, energy accumulated in the inductor L is constant, and while the current flowing through the inductor L decreases when the semiconductor light emitting elements 72 are driven, the energy accumulated in the inductor L is released by a current corresponding to a terminal voltage. In other words, in the switching power supply 106 according to the present exemplary embodiment, the energy accumulated in the inductor is maintained to be constant and thereby control is stabilized.

[0120] Particularly, if a disposition direction of the semiconductor light emitting elements 72 of the semiconductor light emitting element block 74 which are connected in series coincides with a paper transport direction, even in a case where one of the 12 semiconductor light emitting elements is short-circuited thereby not being lighted, a drying operation ofthe semiconductor light emitting element blocks 74 is performed by the accumulated energy, if current of the other 11 semiconductor light emitting elements 72 increase and thereby the amount of light is compensated. Accordingly, drying is not affected (for example, occurrence of uneven drying or the like).

[0121] Particularly, in the continuous paper machine, the printed paper P is transported quickly, and thus, in a case where a method of sequentially sensing the current or the voltage ofthe multiple semiconductor light emitting elements on a timesharing process and reflecting the sensed current or voltage to a pulse cycle or a pulse width of the switching power supply

2016273905 20 Apr 2018 is used, the current of the voltage of the semiconductor light emitting elements is abnormal. Accordingly, the paper is transported as drying is abnormal, until the abnormal current or voltage is reflected to the pulse cycle or the pulse width of the switching power supply, and thus, the abnormal portion becomes a loss.

[0122] In contrast to this, in the switching power supply 106 according to the present exemplary embodiment, while control is performed, the drive current is increased by an operation of the inductor L of the switching power supply 106, and the insufficient amount of light is compensated. Thus, loss due to abnormal drying is prevented.

[0123] Furthermore, the switching power supply 106 according to the present exemplary embodiment has characteristics in which a protection function is provided in a case where there is a short-circuit in the semiconductor light emitting elements 72 connected in series. That is, in a case where the switching elements T (T1 to T4) are switched on, the energy which is applied to the inductors L in the switching power supply 106 is constant because terminal voltages thereof are constant. Hence, when the switching elements T are turned off thereafter the currents flow into the semiconductor light emitting element blocks 74, and thereby the energy is released, only the energy accumulated in the inductors is supplied to the semiconductor light emitting element blocks 74 at the maximum amount. Accordingly, in order to select the inductor L, a current is limited by determining a maximum saturation current, based on the conditions at the time of a normal operation. As a result, since a current is limited in a case where there is a short-circuit in the semiconductor light emitting elements 72, a protection function for the semiconductor light emitting elements 72 other than the short-circuited semiconductor light emitting elements 72 is provided.

Second Exemplary Embodiment) [0124] A switching power supply 106a according to the present exemplary embodiment will be described with reference to Fig. 6. Fig. 6 illustrates a circuit diagram of the switching power supply 106a. The switching power supply 106a has a form in which a protection unit against an over-current and a detection unit of a voltage and a current are provided in the switching power supply 106. Fig. 6 illustrates one ofthe multiple switching power supplies 106a which are connected in parallel, and one ofthe semiconductor light emitting element blocks 74 which are connected in parallel, as a representative.

[0125] As illustrated in Fig. 6, the switching power supply 106a includes a protection unit 304 and a protection unit 306. Furthermore, the switching power supply 106a a current detection unit 308 (light emitting element current detection unit) which detects a current flowing through the semiconductor light emitting element block 74-1, and a voltage detection unit 310 (light emitting element voltage detection unit) which detects a voltage between both

2016273905 20 Apr 2018 terminals of the semiconductor light emitting element block 74-1, but the current detection unit 308 and the voltage detection unit 310 will be described below.

[0126] The protection unit 304 is a circuit which protects the semiconductor light emitting elements 72 from an increase of an output voltage of the switching element T1 by clamping the output voltage, in a case where any one of the semiconductor light emitting elements 72 has an open failure. As illustrated in Fig. 6, the protection unit 304 is configured to include a reverse current blocking diode D5, a MOS transistor T5, a Zener diode D6, and a resistor R5. [0127] The switching power supply (106 or 106a) according to an exemplary embodiment of the invention does not perform a constant voltage control or a constant current control according to feedback differently from a general switching regulator, and momentarily performs a constant pulse control (frequency and pulse width is constant). Accordingly, in a case where the semiconductor light emitting elements 72 are opened, or in a case where the semiconductor light emitting element blocks 74 are not connected and the switching power supply is driven, it is assumed a case where a voltage higher than a rated voltage is generated between an input and an output (VCE of a bipolar transistor or VDS of a MOS transistor) of the switching element T1 and thereby a transistor breaks down. Accordingly, in the switching power supply 106a, the reverse current blocking diode D5 of the protection unit 304 clamps an output of the switching element T1 and thus, the switching element is prevented from breaking down due to an application of the voltage higher than the rated voltage to the switching element. Hereinafter, this configuration is referred to as a “clamp circuit” (clamp unit).

[0128] Furthermore, the present exemplary embodiment includes a detection unit which is configured to include the MOS transistor T5, the Zener diode D6, and the resistor R5 and detects a current. In addition, the detection unit detects a current higher than a current with a predetermined value flowing through the clamp circuit, transmits the detected signal (not illustrated) to a light emission control unit (not illustrated), and stops an operation of the switching power supply 106a. In this way, since the clamp circuit may have only power dissipation characteristics during a period until the operation of the switching power supply 106a stops, the switching power supply 106a can be miniaturized or can prevent useless loss from occurring.

[0129] The protection unit 306 is configured to include a drive 300, a comparator 302, and a resistor R4. The drive 300 mainly has a function of driving the switching element T1 using a signal (referred to as “VPWM” in Fig. 6) such as the switching signal Ss1, and stopping the operation of the switching element T1 after receiving a signal indicating abnormality of a current flowing through an input side of the switching element T1.

[0130] As illustrated in Fig. 6, the switching power supply 106a according to the present exemplary embodiment includes the current detection unit 308 which detects the current

2016273905 20 Apr 2018 flowing through the semiconductor light emitting element block 74-1, but the current detection unit 308 is not able to detect a short-circuit of the inductor while detecting the drive current. [0131] Hence, an input of the switching element T1 is connected in series to a resistor R4 (input current detection unit) for current measurement, and the comparator 302 compares a voltage between both terminals of the resistor R4 with a reference voltage Vref which is a threshold of presence or absence of abnormality of a current. In a case where a measured value of a current flowing through the resistor R4 is abnormal, an output voltage of the comparator 302 is maintained in a high level (or maintained in a low level), and the comparator 302 notifies that a current on a primary side of the switching element T1 is abnormal. If the drive 300 receives a signal indicating the abnormality of a current, the driver stops a signal to the switching element T1, and stops an operation of the switching power supply 106a.

[0132] In this case, if software is interposed in a process until the operation of the switching power supply 106a stops after the abnormality of a current is detected, there is a possibility that an excessive current continuously flows for a predetermined time after the inductor is short-circuited. Accordingly, in the present exemplary embodiment, the switching signal Ss1 is stopped by a current abnormality detecting signal using a hardware method.

(Third Exemplary Embodiment) [0133] The present exemplary embodiment is a form relating to control of drive currents flowing through the semiconductor light emitting element blocks 74-1 to 74-n, and a configuration of a switching power supply is the same as that of the switching power supply 106a illustrated in Fig. 6. Accordingly, illustration of the present exemplary embodiment is omitted.

[0134] In a case where a semiconductor light emitting element is a semiconductor laser, a so-called threshold current Ith which outputs light from a certain current exists in current-light output characteristics. Hence, in a case where the semiconductor light emitting element 72 emits light, a drive current is normally set to a current greater than the threshold current Ith when the semiconductor light emitting element block 74 is lighted. The present exemplary embodiment is a form which prevents overshooting of the drive current flowing through the semiconductor light emitting element block 74 that can occur in a configuration according to the present exemplary embodiment.

[0135] In contrast to a general drive method described above, the present exemplary embodiment starts switching of the switching elements T1 to Tn before lighting is performed. In more detail, cycles and widths of the switching signals Ss1 to Ssn are set such that a peak current flowing through the semiconductor light emitting element block 74 is equal to or lower than the threshold current Ith of the semiconductor light emitting element 72 even in a normal

2016273905 20 Apr 2018 state. The cycles and widths of the switching signals Ss1 to Ssn, or whether or not switching is performed before lighting is performed, is controlled in accordance with time from end of lighting to start of next lighting. Specifically, pulse widths of the signals which are input to the switching elements T1 to Tn are reduced, and thus, the current is limited to a current less than or equal to an oscillation threshold of the semiconductor laser.

[0136] In the switching power supply (106 or 106a) according to the present exemplary embodiment, a current which significantly exceeds a normal current flows through inductors L (L1 to Ln), so as to superimpose a charging current which charges smoothing capacitors C (C1 to Cn) at a normal time. That is, overshoot can be generated immediately after the switching signals Ss (Ss1 to Ssn) are applied to the switching elements T (T1 to Tn), in the drive current of the semiconductor light emitting element blocks 74, so as to generate a voltage higher than a normal voltage when energy is released after the energy greater than normal energy is accumulated in the inductors L.

[0137] In contrast to this, in the present exemplary embodiment, the switching element T stars up in advance, such that the drive current of the semiconductor light emitting element 72 is equal to or less than a threshold current by reducing a pulse width of the switching signal Ss before the semiconductor light emitting element block 74 starts lighting. At this time, rising can be made quickly by providing multiple types of pulse widths so as to perform quickly startup and by driving the switching elements T while the pulse widths are switched according to predetermined schedule based on image information.

[0138] Meanwhile, if a period in which the semiconductor light emitting element block 74 is extinguished is short, a terminal voltage of the smoothing capacitor C is not changed by discharge. In this case, overshoot does not occur, and thus, in a case where a period in which the semiconductor light emitting element block 74 is turned off is within a predetermined time, the switching element T does not start up in advance. Accordingly, it is possible to reduce waste. The aforementioned control is performed on the basis of predetermined schedule based on image information, and thus, it is possible to avoid complex control such as feedback control.

[0139] Furthermore, it is also possible to prevent overshoot by clamping a current flowing through the switching element T, such that the switching element T operates at a linear region by controlling a gate voltage (base voltage in a case a bipolar transistor) of the switching element T. In this case, the amount of heat increases at the time of a linear region, but the transistor does not break down only immediately after power is applied.

(Fourth Exemplary Embodiment) [0140] A semiconductor light emitting element drive control device 62 according to the present exemplary embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is

2016273905 20 Apr 2018 a block diagram of the semiconductor light emitting element drive control device 62, and Fig.

is a timing chart illustrating a time relationship between a counter preset signal and a counter output. The semiconductor light emitting element drive control device 60 uses the counter preset signal of one phase, but the present exemplary embodiment is a form which uses the counter preset signals of four phases.

[0141] As illustrated in Fig. 7, the semiconductor light emitting element drive control device 62 includes a switching signal generation unit 200 which is replaced with the switching signal generation unit 100 (refer to Fig. 3) of the semiconductor light emitting element drive control device 60. The other configuration, that is, the semiconductor light emitting element block 74, the switching power supply 106, the coefficient calculation unit 108, the switching time calculation unit 110, the drive power supply (voltage source) 112, and the control power supply 114 are the same as those of the semiconductor light emitting element drive control device 60, and thus, detailed description thereof will be omitted.

[0142] As illustrated in Fig. 7, the switching signal generation unit 200 also includes transistors 202-1 to 202-n which respectively correspond to the semiconductor light emitting element blocks 74-1 to 74-n, and counters 204-1 to 204-n. In addition, the switching time signal St and a transmission clock are input to a shift register 202, in the same manner as the switching signal generation unit 100.

[0143] Meanwhile, counter preset signals PresetO, Presetl, Preset2, and Preset3 of four phases are inputted to the switching signal generation unit 200. Each of counter preset 0 to counter preset 3 is inputted to counters 204 as described below. That is, the counter preset 0 is inputted to the counter 204-1, the counter preset 1 is inputted to the counter 204-2, the counter preset 2 is inputted to the counter 204-3, and the counter preset 3 is inputted to the counter 204-4, respectively. Hereinafter, in the same manner, the counter preset 0 is inputted to the counter 204-5, the counter preset 1 is inputted to the counter 204-6, the counter preset 2 is inputted to the counter 204-7, and the counter preset 3 is inputted to the counter 204-8. If the number n of the semiconductor light emitting element blocks 74 is a multiple of four, the counter preset 3 is inputted to the counter 204-n, but in the present exemplary embodiment, n may not be a multiple of four, and thus, a counter preset signal of any phase may be inputted to the counter 204-n.

[0144] If signals indicating the switching times ts1 to tsn included in the switching time signal St are sequentially shifted by the transmission clock and are set to the shift transistor 202-1 to 202-n, the counter presets 0 to 4 with four phases are inputted to the respective counters 204-1 to 204-n in a state where timing thereof is shifted. As a result, the switching signals Ss1 to SSn are transmitted to switching power supplies 106-1 to 106-n from the counters 204-1 to 204-n in accordance with timing of each counter preset. The switching power supplies 106-1 to 106-n are driven by the switching signals Ss1 to Ssn whose timings

2016273905 20 Apr 2018 are shifted, and thereby the switching currents whose timings are shifted flows through each switching power supply 106. However, in the present exemplary embodiment, counter presets of four phases are used and thus, the counter presets have the same timing in each fourth counter preset.

[0145] Here, the number 4 of phases of the counter presets according to the present exemplary embodiment is an example, and if there are multiple counter presets, the effects according to the present exemplary embodiment are obtained, in light of the spirit of the present exemplary embodiment. In addition, the present exemplary embodiment may be a form which uses counter presets corresponding to the number of the semiconductor light emitting element blocks 74-1 to 74-n, that is, counter presets with n phases.

[0146] An operation of the switching signal generation unit 200 will be described in detail with reference to Fig. 8. A method of generating the counter preset signals with four phases is not limited in particular, but in the present exemplary embodiment, the counter preset signals with four phases are generated with a time interval which is obtained by dividing a pulse interval T of the counter preset signal illustrated in Fig. 8 into four pieces. In other words, the present exemplary embodiment generates the counter preset signals whose phases are different from each other by 90° by setting the pulse interval T as one cycle.

[0147] As illustrated in Fig. 8, the counter preset 0 is inputted to the counter 204-1 at time t5, and thereby an output of the counter 204-1 is changed from a low level to a high level.

Only during a period of the switching time ts 1 in the counter 204-1, a counter output 0 having a high level is outputted to the switching power supply 106-1 from the counter 204-1 as the switching signal Ss1 ((a) to (c) in Fig. 8).

[0148] In the same manner, the counter preset 1 is inputted to the counter 204-2 at time t6, and thereby a counter output 1 of the counter 204-2 is outputted to the switching power supply 106-2 as the switching signal Ss2. The counter preset 2 is inputted to the counter 204-3 at time t7, and thereby a counter output 2 of the counter 204-3 is outputted to the switching power supply 106-3 as the switching signal Ss3. The counter preset 3 is inputted to the counter 204-4 at time t8, and thereby a counter output 3 of the counter 204-4 is outputted to the switching power supply 106-4 as the switching signal Ss4 ((d) to (i) in Fig. 8).

[0149] As illustrated in Fig. 8, timings (phases) of the counter output 0 to the counter output 3 are shifted by the operation of the aforementioned switching signal generation unit 200. By doing so, load of the drive power supply 112 is not concentrated but equalized (distributed), and thus, ripple or noise in a waveform of a voltage Vp of the drive power supply 112 is prevented from occurring, and a potential of ground is stabilized.

(Modification Example of Fourth Exemplary Embodiment)

2016273905 20 Apr 2018 [0150] The present example will be described with reference to Fig. 9. The present example has a form in which switching power supplies 106 (generic numeral of the switching power supplies 106-1, 106-2, 106-3, and 106-4) of the semiconductor light emitting element drive control device 62 are replaced with switching power supplies 107 (generic numeral of switching powersupplies 107-1, 107-2, 107-3, and 107-4). Hence, configurations other than the switching power supplies 107 are the same as the semiconductor light emitting element drive control device 62, and thus, description on the semiconductor light emitting element drive control device including the switching power supplies 107 will be made with reference to Fig. 7 and Fig. 8.

[0151] As illustrated in Fig. 9, each of the switching powersupplies 107-1 to 107-4 according to the present example is configured to include parasitic inductors Ls1 to Ls4, regenerative diodes Dpi to Dp4, and the switching elements T1 to T4. One terminals of the switching power supplies 107 are connected to the semiconductor light emitting element block 74, and the other terminals thereof are connected to the drive power supply 112.

[0152] The parasitic inductors Ls1 to Ls4 are respectively equivalent elements representing inductance components of wires from the switching elements T1 to T4 to the semiconductor light emitting element blocks 74-1 to 74-4 as inductors. The semiconductor light emitting element block 74-1 to 74-4 are generally disposed to be separated from the semiconductor light emitting element drive control device 62 for power dissipation or the like. In this case, the inductance components of the wires from the switching elements T1 to T4 to the semiconductor light emitting element blocks 74-1 to 74-4 also depend upon widths of the wires, but cannot be ignored in driving the semiconductor light emitting element blocks 74-1 to 74-4. Accordingly, in the present example, the parasitic inductors Ls1 to Ls4 are provided as circuit elements.

[0153] As illustrated in Fig. 9, the switching power supplies 107 do not include inductors (inductors L1 to L4 of Fig. 5) as elements, and the switching elements T1 to T4 are arranged between the power supply 112 and the semiconductor light emitting element blocks 74-1 to 74-4 which are loads, in a manner different from the switching power supplies 106. In addition, an average value of currents flowing through the semiconductor light emitting element blocks 74-1 to 74-4 by the switching signals Ss1 to Ss4 which are input to the control terminals N1 to N4 of the switching elements T1 to T4 is controlled without shifting the phase. The semiconductor light emitting element drive control device according to the present example is effective under such conditions particularly.

[0154] That is, as described in the present example, a method of equalizing loads by shifting a phase is more effective for the switching power supplies which do not include the inductors L1 to L4 as illustrated in Fig. 9. That is, the circuit illustrated in Fig. 9 does not include the inductors L1 to L4, and thus, when the switching elements T1 to T4 are switched,

2016273905 20 Apr 2018 a differential coefficient dl/dt of a current I flowing through the load is significantly large. Accordingly, if timings when all the semiconductor light emitting element blocks 74-1 to 74-4 are turned on overlap each other, excessive noises may be superimposed on each other and the semiconductor light emitting element drive control device may perform an abnormal operation or the like. At this point, according to the semiconductor light emitting element drive control device of the present example in which switching phases of each of the semiconductor light emitting element blocks 74-1 to 74-4 are different from each other, noise is effectively prevented from occurring.

(Fifth Exemplary Embodiment) [0155] A semiconductor light emitting element drive control device 64 according to the present exemplary embodiment will be described with reference to Fig. 10. The semiconductor light emitting element drive control device 64 has a form in which a monitoring unit that acquires various types of monitoring values for correcting the coefficients tOi, a, and β of the switching time calculation expression (Expression 1) is provided in the semiconductor light emitting element drive control device 60 illustrated in Fig. 3.

[0156] As illustrated in Fig. 10, the semiconductor light emitting element drive control device 64 includes monitoring units 78-1 to 78-n for monitoring characteristics of each of the semiconductor light emitting element blocks 74-1 to 74-n, as an example. Results which are monitored by the monitoring units 78-1 to 78-n are input to the switching time calculation unit 110. The other configurations are the same as those of the semiconductor light emitting element drive control device 60, and thus, detailed description thereof will be omitted.

[0157] The monitoring unit 78 according to the present exemplary embodiment monitors electrical characteristics, optical characteristics, or the like of the semiconductor light emitting element 72. The monitored results are input to the switching time calculation unit 110, and are compared with an external control value (Iset). In a case where there is a shift as the compared results, the coefficients tOi, a, and β of the switching time calculation expression (Expression 1) are corrected, and thereby degradation over time or characteristics variation of the semiconductor light emitting element, characteristics variation of a component of the power supply circuit, and the like are incorporated into the coefficients. Accordingly, accuracy of the switching signals Ss1 to Ssn increases.

[0158] The current detection unit (light emitting element current detection unit) 308 of the semiconductor light emitting element block 74, and the voltage detection unit (light emitting element voltage detection unit) 310 will be described as an example of the monitoring unit 78 according to the present exemplary embodiment with reference to Fig. 6. As illustrated in Fig. 6, the current detection unit 308 is configured by the resistor R1 connected between a cathode side of the semiconductor light emitting element block 74 and GND. In addition, a

2016273905 20 Apr 2018 terminal voltage of the resistor R1 is inputted to the switching time calculation unit 110 as a monitoring current value IM. In addition, as illustrated in Fig. 6, the voltage detection unit 310 is configured by a resistor R2 and a resistor R3 which are connected between an anode side of the semiconductor light emitting element block 74 and GND. In addition, voltages divided by the resistor R2 and the resistor R3 are inputted to the switching time calculation unit 110 as a monitoring voltage value VM.

[0159] For example, in a case where characteristics of the semiconductor light emitting element 72 are changed over time, the monitoring current value IM and the monitoring voltage value VM change with respect to initial values, and thus, the switching time calculation unit 110 detects a difference therebetween, reflects the difference to switching time calculation expression (Expression 1), and corrects the coefficients tOi, a, and β.

[0160] The current detection unit 308 and the voltage detection unit 310 according to the present exemplary embodiment perform measurement more accurately than the comparative example. Hereinafter, the reason will be described.

[0161] In a case where a voltage and a current are measured, a terminal which is a reference, for example, if GND does not match GND of a measurement system, an extra circuit such as a differential amplifier is required. In contrast to this, in the semiconductor light emitting element drive control device according to the present exemplary embodiment, a cathode side of the semiconductor light emitting element block 74 is connected to GND, and thus, direct current measurement is made by inserting a resistor for current measurement between the cathode and GND.

[0162] A resistance value of the resistor R1 for current measurement is set to a value of, for example, approximately 0.01 Ω to 0.1 Ω by taking effects on voltage measurement, loss, and measurement accuracy into account. Since a value of a current flowing through the semiconductor light emitting element block 74 is generally large, if effects of a potential change of GND on measurement accuracy are taken into account, both terminals of the resistor R1 for current measurement are simultaneously measured, and thereby a current value is calculated from a potential and a resistance value of the resistor R1. Meanwhile, also in the voltage detection unit 310 which measures a drive voltage of the semiconductor light emitting element block 74, a cathode side of the semiconductor light emitting element block 74 is GND at all times, and thus, a potential on an anode side is also measured by using GND of a measurement system as a reference.

[0163] The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the

2016273905 20 Apr 2018 invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

2016273905 20 Apr 2018

Claims

CLAIMS:

1. A drive control device of semiconductor light emitting elements, comprising:

a plurality of current generation units that respectively supply separate drive currents to a plurality of semiconductor light emitting element groups, respectively include reception portions that receive switching signals, and control the drive currents according to the switching signals, each of the plurality of semiconductor light emitting element group including at least one semiconductor light emitting element;

a switching signal generation unit that generates the plurality of switching signals according to target values of the drive currents and supplies the plurality of switching signals to the plurality of reception portions, respectively; and a voltage source that is in a serial relationship with the current generation unit and the semiconductor light emitting element groups.
2. The drive control device according to claim 1, wherein each ofthe switching signals are a binary digital signal, and wherein the switching signal generation unit generates each ofthe switching signals by changing at least one of a pulse width and a pulse cycle of the digital signal according to a target value of a drive current for a semiconductor light emitting element group when the semiconductor light emitting element group extinguishes light and emits the light.
3. The drive control device according to claim 2, further comprising:

a switching time calculation unit that calculates at least one of the pulse width and the pulse cycle according to the target value.
4. The drive control device according to claim 3, further comprising:

a correction unit that corrects at least one of the pulse width and the cycle with characteristics of at least one of: the semiconductor light emitting element groups; the voltage source; the current generation unit; and the switching signal generation unit, which are required for calculating at least one of the pulse width and the cycle by switching time calculation unit.
5. The drive control device according to claim 4, further comprising:

a monitoring unit that monitors electro-optical characteristics of the plurality of semiconductor light emitting element groups, wherein the correction unit corrects at least one of the pulse width and the cycle according to a monitoring result ofthe monitoring unit.

2016273905 20 Apr 2018
6. The drive control device according to any one of claims 1 to 5, wherein each of the plurality of semiconductor light emitting element groups includes a plurality of semiconductor light emitting elements connected in series, and wherein for each one of the plurality of semiconductor light emitting element groups, the current generation unit includes a switching element having a control terminal in the reception portion, an inductor that is connected to an output terminal of the switching element and is in a parallel relationship with the one of the plurality of the semiconductor light emitting element groups, and a capacitor that is connected in parallel with the one of the plurality of the semiconductor light emitting element groups.
7. The drive control device according to any one of claims 1 to 5, wherein each of the plurality of semiconductor light emitting element groups includes a plurality of semiconductor light emitting elements connected in series, and wherein for each one of the plurality of semiconductor light emitting element groups, the current generation unit includes a switching element having a control terminal in the reception portion, an inductor that is connected between the switching element and the one of the plurality of the semiconductor light emitting element groups, and has an equivalent inductance component of a wire from the switching element to the one of the plurality of the semiconductor light emitting element groups, and a diode which is connected in parallel with the one of the plurality of the semiconductor light emitting element groups.
8. The drive control device according to claim 6 or 7, further comprising:

at least one of a current detection unit that is connected between a cathode side of each one of the plurality of the semiconductor light emitting element groups and a ground and detects a current flowing through the one of the plurality of the semiconductor light emitting element groups, and a voltage detection unit that is connected between an anode side of the one of the plurality of semiconductor light emitting element groups and a ground and detects a voltage between both terminals of the one of the plurality of the semiconductor light emitting element groups.
9. The drive control device according to any one of claims 6 to 8, further comprising: a clamp unit that clamps a voltage of an output terminal of the switching element.
10. The drive control device according to claim 9, wherein the clamp unit includes a detection unit that detects a current flowing through the clamp unit, and in a case where a current detected by the detection unit is more than a given value, operations of the plurality of current generation units are stopped.

2016273905 20 Apr 2018
11. The drive control device according to any one of claims 6 to 10, further comprising: an input current detection unit that detects a current flowing through an input terminal of the switching element, wherein, in a case where a current detected by the input current detection unit is more than a given value, operations of the plurality of current generation units are stopped.
12. The drive control device according to any one of claims 1 to 11, wherein the switching signal generation unit makes timings of each of the plurality of switching signals different among each other and supplies the plurality of switching signals with different timings to the reception portions, respectively.
13. The drive control device according to any one of claims 1 to 12, wherein the semiconductor light emitting element is a semiconductor laser, and wherein the switching signal generation unit generates a switching signal such that a drive current that is defined to a current less than a threshold current of the semiconductor laser during a defined period flows before a timing in which the semiconductor laser is changed from an extinguished state to a light emitting state in order for the drive current not to oscillate or not to be delayed at the timing.
14. The drive control device according to any one of claims 1 to 12, wherein the semiconductor light emitting element is a light emitting diode.
15. A droplet drying device comprising:

a plurality of semiconductor light emitting elements; and a drive control device according to any one of claims 1 to 14.

16. An image forming device comprising:

an image forming unit that ejects droplets in accordance with image information and forms an image according to the image information on a recording medium; and a droplet drying device according to claim 15, wherein the droplet drying device dries droplets ejected on the recording medium by the image forming unit.

2016273905 14 Dec 2016

2/11

F/G, 2

DIRECTION

2016273905 14 Dec 2016

CO

LU LU ± L· O tz LU ZZ> >coz

5¾ LU 03 _o

oi CM Qi ex oi e M·-. θ \ LU j 'M . g y UJ e θξ LU ZZ 7?* 1 Z3 ZQ O o O o o O

<c <c fV' 'V'

LJL— i-J-<c <c -¾

Q„ Ω..

H; LU Q zz> > oi ϋ a: h C£ Q '/?

O Qi >Ί CZ L!·: n Sod

LJ CL· CO

Ld Eu -%-» > bs Q- o. oi zc 9_ z>

CG —3 Q„ CO

03 Φ 03 w 03 <D oi ... n

o

QZ

LU

ZEE o

o .3“

CM

2016273905 14 Dec 2016

LU

2»

1— J—“ LU Ί GO Q_ LU LL QC z> o CL o a: QC cc LU LU LU AZ EZ o Z3 Z5 o o o o o o ra 'o' 'C

2016273905 14 Dec 2016

2016273905 14 Dec 2016 co o

V' <o a:

2016273905 14 Dec 2016

o o x- 'S— ;..... [—— j__ H” UJ o UJ —Xj co CL <75 CL UJ [—— LU H“ XL Qi ~3 oi ZD o CL o CL o oi oi Qi oi oi LU UJ LU LU LU I— J—“ H— J—“ s' ~Z. Z5 ΖΣ5 —j Ό —Xj o o o o o o o o o o S' S' S' S' s

CXi

UJ <75

UJ

C£

a.

Qi

UJ

O o

CM co j- Z5 LU CL CO j—- LU Z5 CL o CL CL oi LU LU - 1-- ID Z5 o o o o S5

co

Ξ3

CL

O oi

UJ

O o

2016273905 14 Dec 2016 fr............................

CM

2016273905 14 Dec 2016 ο

ο ο

2016273905 14 Dec 2016