JP3276161B2 - Fluorescent light dimmer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial application] Dimming method in copier, especially
The present invention relates to a dimming method for a fluorescent lamp.

[0002]

2. Description of the Related Art Conventionally, a dimming method for a fluorescent lamp has been entirely performed by hardware as shown in FIG.

For example, when a copy key of a copying machine is depressed, a preheating current control signal 14 shown in FIG.
Is sent to the high-frequency inverter 2, the fluorescent lamp 1 is turned on, and the full lighting is started as shown by b to c in FIG.
After the PWM start signal 17 is input to the gate element 13 at c of B, a PWM control signal 12 of a rectangular wave whose duty is controlled is sent to the high-frequency inverter 2 through the gate element 13 and the fluorescent lamp 1 is dimmed. Is done. In order to obtain a PWM control signal 12 for this, a PWM generation circuit 4 and a PUT (programmable unifunction transistor) transmission circuit 9 for generating a PWM cycle are provided, and the latter output signal 16 (A in FIG. 9) and the optical fiber 10 capture the signal. The light from the fluorescent lamp 1 is subjected to photoelectric conversion by the photodiode 5 and a signal output through a circuit including a buffer and an operational amplifier for signal integration 7 is input to a comparator 8 so that a PWM control signal 12 shown in FIG. Has become.

[0004]

However, in this system, the cost of hardware such as the operational amplifier 7, the comparator 8, the transmitting circuit 9 and the like is increased, and the variation of the waveform of the transmitting circuit 9 and the offset of the operational amplifier 7 cause the fluorescent light. Light control varies.

[0005]

According to the present invention, when applied to a copying machine, the sequence control of the copying machine and the dimming control of the fluorescent lamp are performed by one one-chip microcomputer.
The cost reduction by removing the hardware described above and the stable dimming of the fluorescent lamp are realized.
By the analog signal output of the photoelectric conversion circuit at the time of full lighting (100% lighting) in the initial sequence of dimming, P
By predicting the duty ratio of the WM control, the dimming control is quickly performed, and the speed of the copy sequence is increased.

The first invention of the present invention has a fluorescent lamp as a light source for reading an original, a high-frequency inverter for lighting the fluorescent lamp, and a photoelectric conversion circuit for detecting a light amount of the fluorescent lamp. Controlling the high-frequency inverter and controlling a fluorescent lamp by processing an analog signal output of the photoelectric conversion circuit by a one-chip microprocessor with a built-in analog / digital converter. Means for determining an initial value of the duty ratio based on the value of the analog signal output when the fluorescent lamp is fully lit. If the initial value does not reach the first target illuminance range, the target illuminance range is again converted to analog / digital. The first means to obtain by setting data in the control unit of the converter built-in one-chip microprocessor Upon reaching the first target illumination range, second means for determining the manner duty ratio reaches the second target illumination, a fluorescent lamp light modulation apparatus characterized by having a.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a copying machine according to the present invention. FIG. 1 is a fluorescent lamp dimming circuit according to the present invention, FIG. 2 is an analog output voltage graph representing the analog output signal 19 of FIG. 1 with respect to the illuminance of the fluorescent lamp input to the photodiode 5, and FIG. FIG. 4 is a block diagram of a copying machine according to the present invention, and FIGS. 5 and 6 are external views of the copying machine according to the present invention.

Reference numeral 1 denotes a fluorescent lamp, 2 denotes a high-frequency inverter for energizing the fluorescent lamp, and 3 denotes the light of the fluorescent lamp 1 received by the optical fiber 10 and its input to an analog output signal 19.
A photodiode 5, which receives light from an optical fiber 10 for detecting the amount of light of a fluorescent lamp and photoelectrically converts the light, a photocurrent / voltage conversion operational amplifier 6 for converting a photocurrent into a voltage, and Has the required resistance.

Reference numeral 11 denotes an analog output signal from the photoelectric conversion circuit 3, reference numeral 14 denotes a preheating current control signal (hereinafter, PRH) for supplying a preheating current to the fluorescent lamp 1, and reference numeral 15 denotes an output from the high-frequency inverter 2. Reference numeral 18 denotes a control current for the fluorescent lamp 1, reference numeral 18 denotes a microprocessor with a built-in analog / digital converter (hereinafter, MPU), and reference numeral 19 denotes a photoelectric conversion circuit 3.
, An analog output signal (hereinafter, APD: see FIG. 2, analog output signal 11 is converted to a signal that can be input to the MPU), 20 is a central control unit, and 21 is a central control unit.
Denotes a document table control unit, 22 denotes an operation and display unit, 23 denotes a conveyance control unit, 24 denotes a high voltage control unit, 25 (FIGS. 4 and 5) denotes a copy key, and 26 denotes a copy key. 5 is a jam display LED, 27 is a paper-out display LED, 28 is an error display LED, 29 is a ready display LED, 30 is a power supply unit, and 31 in FIG.
Denotes a platen for setting a document, 32 denotes a pressure plate, 33 denotes a cassette for setting copy paper, 34 denotes a power cord, and 35 denotes a discharge for discharging the copied paper. It is a paper section.

Next, the basic operation of a copying machine according to the present invention will be described. By pressing the copy key 25,
In order to copy the original placed on the platen 31, the MPU 18
Controls the respective control units to move the document table 31 to the copy start position, and at the same time, performs dimming of the fluorescent lamp by the circuit configuration of FIG. 1 and the dimming sequence of FIG. Next, after dimming is completed, the document table control unit 21, the conveyance control unit 23, and the high voltage control unit 2
4 operates, the image of the document is copied onto the copy sheet, and the copied sheet is discharged from the sheet discharge unit 35.

Next, the fluorescent lamp control according to the present invention will be described in detail with reference to FIG. 9 and FIGS.

First, a preheating current control signal (PRH) 14
Is asserted low, and a preheating current flows through the fluorescent lamp 1 for about 3 seconds (step (1)). Next, PRH is h
At the same time as being negated to high, the PWM is asserted low for 0.5 seconds at the gate element 13 and (0.
Lights 100% for 5 seconds (at the same time as step (2), the dimming time detection timer FT starts in step (3) and
Operate for 0 seconds. )). The analog output signal A at that time
The PD 19 is converted into 8-bit digital data by the analog / digital converter of the microprocessor MPU 18 and recorded in a register (now referred to as AD). AD ≧ 128 is compared in step (4). Return to the sequence (10) and set the lighting retry FN to 3
Repeat as many times as necessary. Here, when AD ≦ 10 is true, it is determined that no lighting has been performed, and FN for storing the number of lighting sequences is incremented by one. Then, the lighting sequence is restarted again, and the light control is started again (1). Then, when FN becomes 4, (when counting up from the initial value 0, and AD ≦ 10 even at the fourth time), it is determined that the lighting is abnormal, the main body is stopped, and the error display LED 28 is turned on. Here, values such as FN, FT, AD, and DUTY are stored in MP.
Obviously, it can be realized by a register in the U, a memory, or a memory provided outside the MPU. If YES, proceed to step (5).

The duty ratio of PWM (currently Duty
Is calculated by Duty = Duty-{(AD-128) XK} (1). Here, the initial data of Duty is 100
(100% lighting) K is a feedback constant, which is set to 100/256. That is, the expression (1) expresses an appropriate Du by the value of AD.
The value of ty is predicted, and the value of step (5) in FIG.
(6) The number of loops is reduced as much as possible to provide a fluorescent light control in a short time. The output of the PWM cycle and the duty ratio calculated by the equation (1) is performed by setting data in a timer control unit in the MPU 18. Then, in this step (5), (AD-12
8) If <8, AD = 128 is targeted, and finer dimming is performed in steps (12 to 15). If 125 <AD <131 in step (16), the process proceeds to step (17) to adjust. The light is completed, and the process proceeds to the copy sequence.

Here, if the dimming is not successful and it is not possible to shift to the dimming OK (17) within 60 seconds, it is determined that the lighting is abnormal, the main body is stopped, and the error display LED 28 is turned on.

In this embodiment, the fluorescent lamp dimming circuit in the copying machine has been described. However, application to an imaging apparatus using a fluorescent lamp, such as a facsimile and a printer, is considered.

[0016]

According to the fluorescent lamp dimming circuit of the present invention,
Compared with the conventional fluorescent lamp dimming circuit shown in FIG. 7, the PWM generation circuit 4 can be omitted, and stable dimming of the fluorescent lamp can be realized.
By the analog signal output of the photoelectric conversion circuit at the time of full lighting (100% lighting) in the initial sequence of dimming, P
An appropriate duty ratio of the WM is predicted, and even if the characteristics of the fluorescent lamp are changed (deteriorated), dimming control can be performed appropriately and quickly, and the cost is low because a one-chip microprocessor is used.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fluorescent lamp dimming circuit showing an embodiment of the present invention.

FIG. 2 is a graph of analog output power with respect to illuminance of a fluorescent lamp input to a photodiode.

FIG. 3 is a flowchart of a dimming sequence according to the present invention.

FIG. 4 is a block diagram of a copying machine according to the present invention.

FIG. 5 is a front view of the copying machine.

FIG. 6 is a side view of the copying machine.

FIG. 7 is a circuit diagram of a fluorescent lamp dimming circuit using conventional hardware.

FIG. 8 is a time chart showing a dimming sequence.

FIG. 9 is a diagram showing an output waveform and a PWM output waveform of a transmission circuit.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 fluorescent lamp 2 high frequency inverter 3 photoelectric conversion circuit 18 microprocessor with built-in analog / digital converter 19 analog output signal from photoelectric conversion circuit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuyuki Suzuki 6-3-3 Shimorenjaku, Mitaka-shi, Tokyo Copier Co., Ltd. (56) References JP-A-58-142795 (JP, A) 2-174092 (JP, A) JP-A-2-15599 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 41/392 G03B 27/72

Claims (1)

(57) [Claims] 1. A fluorescent lamp as a light source for reading a document, a high-frequency inverter for lighting the fluorescent lamp, and a photoelectric conversion circuit for detecting a light amount of the fluorescent lamp, and a built-in analog / digital converter. In a fluorescent light dimmer, a one-chip microprocessor controls the high-frequency inverter by processing an analog signal output of the photoelectric conversion circuit, thereby controlling a fluorescent lamp. Means for determining an initial value of the duty ratio based on the value of the analog signal output at the time when the first target illuminance range is not reached due to the initial value. The first means to obtain by setting data in the control unit of the first, reach the first target illuminance range When, second means for determining the manner duty ratio reaches the second target illumination, a fluorescent lamp light modulation apparatus characterized by having a.