JP7060562B2 - Drive circuit - Google Patents

Description

The present invention relates to a load drive circuit driven by a current that takes an on or off value (hereinafter referred to as "current on / off drive type").

The current on / off drive type load is, for example, a light emitting element. For example, the drive circuit of the light emitting element controls lighting and extinguishing of the light emitting element. The drive circuit of the light emitting element is used, for example, in an illumination light communication device or the like that communicates using illumination light. The illumination optical communication device transmits a digital signal by modulating the intensity of the illumination light with a digital signal.

Patent Document 1 discloses an example of a drive circuit for a current on / off drive type load. Referring to FIG. 1 of Patent Document 1, the illumination optical communication device of Patent Document 1 has a current-driven semiconductor light emitting device LED1 and an N-channel type MOS (Metal Oxide Semiconductor) between the output terminals of the DC constant voltage source 10. Transistors (hereinafter referred to as “NMOS”) Q1 and Q2 and resistors r are connected in series. Further, the output terminal of the buffer IC1 is connected to the gate of the NaCl Q1. Further, a signal for switching the NaCl Q1 is input to the input terminal of the buffer IC1. Further, the output terminal of the operational amplifier IC2 is connected to the gate of the MIMO Q2.

As a result of the above configuration, in the illumination optical communication device of Patent Document 1, the voltage between the MIMO Q2 and the resistor r is input to the negative input terminal of the operational amplifier IC2 (comparator). Further, the reference voltage Vr is input to the positive input terminal of the operational amplifier IC2, and when the semiconductor light emitting device LED1 is lit, the operational amplifier IC2 operates so that the voltage between the nanotube Q2 and the resistor _r and the reference voltage Vr match _. .. That is, the constant current circuit is composed of the operational amplifier IC2, the reference voltage Vr connected to the positive input terminal of the operational amplifier IC2, the NaCl Q2, and the resistance _r . Then, a constant current of I1 = Vr / _r flows in the constant current circuit when the semiconductor light emitting device LED1 is lit.

That is, in the illumination optical communication device of Patent Document 1, the lighting state and the extinguishing state of the semiconductor light emitting element LED1 are switched by switching the nanotube Q1 by the input signal to the buffer IC1. When the semiconductor light emitting device LED1 is turned on, a constant current I1 flows through the semiconductor light emitting device LED1, and when the semiconductor light emitting device LED1 is turned off, a current I1 = 0 flows through the semiconductor light emitting device LED1.

Another example of a drive circuit for a current on / off drive type load is disclosed in Patent Document 2. With reference to FIGS. 1 and 2 of Patent Document 2, in the switching constant current power supply device of Patent Document 2, when a current flows through the load 6 that repeats interruption and discontinuity, the feedback path (path 1: transistor Q1, diode D1, load 6). , The detection circuit 5, the feedback circuit 7, and the control circuit 4) function. Here, the feedback circuit 7 includes a selection circuit 9 and a fixed signal generation circuit 8. Then, in the path 1, the selection circuit 9 selects the signal from the detection circuit 5 included in the feedback path. Further, the control circuit 4 includes an operational amplifier EA1. Then, a fixed voltage VR is applied to the inverting input terminal of the operational amplifier EA1. Further, a voltage level determined by the detection circuit 5 included in the feedback path is applied to the normal rotation input terminal of the operational amplifier EA1 so as to stabilize the current flowing through the load. On the other hand, in the switching constant current power supply device of Patent Document 2, the non-feedback path (path 2) functions when no current flows through the load 6. Here, the path 2 includes the feedback circuit 7 and the control circuit 4. In the path 2, the selection circuit 9 selects the signal from the fixed signal generation circuit 8. That is, a constant level voltage VC is applied to the operational amplifier EA1 from the fixed signal generation circuit 8. In Patent Document 2, a voltage VC having a constant level from the fixed signal generation circuit 8 is referred to as a "second feedback signal", but the voltage VC is not actually a signal from which the output of the operational amplifier EA1 is fed back. .. That is, in the technique of Patent Document 2, when a current is flowing through the load 6, the current flowing through the load 6 is controlled by using the signal from the feedback path. However, in the technique of Patent Document 2, when no current is flowing through the load 6, the current flowing through the load 6 is controlled by using a preset fixed voltage VC.

Japanese Unexamined Patent Publication No. 2010-283616 Japanese Unexamined Patent Publication No. 2004-328949

Generally, an operational amplifier having a very high gain is used. When the operational amplifier is used alone without a feedback path, the output sticks to the upper limit value or the lower limit value with a slight differential input voltage. That is, in order to use it in the normal operating range (effective output range not including the upper limit value or the lower limit value), it is necessary to strictly adjust the differential input voltage. Further, if the power supply voltage or the environmental temperature fluctuates, it is necessary to readjust the differential input voltage.

However, in the technique of Patent Document 1, when the semiconductor light emitting device LED1 is turned off, no current flows through the NaCl Q2 constituting the negative feedback path to the operational amplifier IC2, so that the negative feedback path becomes invalid and the operation of the operational amplifier IC2 is performed. The point deviates from the normal operating range.

When the light emitting element is switched from this state to the lighting state, the negative feedback path becomes effective, so that the operating point of the operational amplifier IC2 that has deviated from the normal operating range returns to the normal operating range, and the semiconductor emits light at a constant current. The element LED1 is driven. That is, the time for the semiconductor light emitting device LED1 to transition from the extinguished state to the lit state by the constant current is increased by the time (delay time) for the operating point of the arithmetic amplifier IC2 to return from the normal operating range to the normal operating range.

That is, the technique of Patent Document 1 has a problem that the transition (switching) time between the on state and the off state when the load is driven is long.

The technique of Patent Document 2 has the same problems as the technique of Patent Document 1.

The present invention has been made in view of the above problems, and the main object of the present invention is to suppress the transition time between the on state and the off state when the current on / off drive type load is driven.

In one aspect of the invention, the drive circuit comprises at least one first resistor connected in series with the corresponding load, a second resistor, and at least one first resistor depending on the input selection signal. A first switching means that selects one of a device and a second resistor as a selection resistor and outputs a signal having a magnitude corresponding to the current flowing through the selection resistor as a feedback signal, and a predetermined target signal of the feedback signal. It is provided with a negative feedback means for outputting a signal having a magnitude corresponding to the difference as an adjustment signal and a current control means for supplying a current having a magnitude corresponding to the adjustment signal only to the selection resistor.

According to the present invention, there is an effect that the transition time between the on state and the off state can be suppressed when the current on / off drive type load is driven.

It is a block diagram which shows an example of the structure of the drive circuit in 1st Embodiment of this invention. It is a block diagram which shows an example of the structure of the drive circuit in 2nd Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the drive circuit in 3rd Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the drive circuit in 4th Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the drive circuit in 5th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, the same components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.
(First Embodiment)
The first embodiment of the present invention, which is the basis of each embodiment of the present invention, will be described.

The configuration in this embodiment will be described.

FIG. 1 is a schematic diagram showing an example of a configuration of a drive circuit according to the first embodiment of the present invention.

The drive circuit 109 in the present embodiment includes at least one resistor 140 (first resistor), a resistor 150 (second resistor), a switching unit 170 (first switching means), and a negative feedback unit 120. , And a current control unit 139.

Each resistor 140 is connected in series with the corresponding load 200. The load 200 is a current on / off drive type.

The switching unit 170 selects at least one of the resistor 140 and the resistor 150 as the selection resistor according to the input selection signal Sig, and selects a signal having a magnitude corresponding to the current flowing through the selection resistor. Output as a feedback signal.

The negative feedback unit 120 outputs as an adjustment signal a signal that strongly suppresses the current as the difference between the feedback signal and the predetermined reference signal is larger. Here, the reference signal is a feedback signal having a magnitude corresponding to the target value of the current when the target value of the current flowing through the selective resistance is determined. For example, if the target value of the current flowing through the resistor 140 (resistance value R1) is I10 and the magnitude of the feedback signal S1 at that time is voltage V1 = R1 × I10, the reference signal is R1 × I10. However, the internal resistance (resistance value r) of the load 200 is included in R1 or is negligibly smaller than that of R1.

The current control unit 139 supplies only the current of the magnitude corresponding to the adjustment signal to the selective resistance.

The operation in this embodiment will be described.

When the resistor 140 having the selection signal Sig is selected as the selection resistor, the switching unit 170 selects the resistor 140 as the selection resistor according to the input selection signal Sig, and the current flowing through the selection resistor. A signal S1 having a magnitude corresponding to the above is output as a feedback signal.

When the selection signal Sig selects the resistor 150 as the selection resistor, the switching unit 170 selects the resistor 150 as the selection resistor according to the input selection signal Sig, and corresponds to the current flowing through the selection resistor. The magnitude signal S2 is output as a feedback signal.

Regardless of the value of the selection signal Sig, the negative feedback unit 120 outputs a signal having a magnitude corresponding to the difference between the feedback signal and the predetermined target signal as an adjustment signal.

Depending on the value of the selection signal Sig, the current control unit 139 supplies only the current of the magnitude corresponding to the adjustment signal to the selection resistance.

As described above, in the drive circuit 109 in the present embodiment, the switching unit 170 outputs a feedback signal having a magnitude corresponding to the current flowing through the selection resistance, regardless of the value of the selection signal Sig. Then, the negative feedback unit 120 outputs a signal having a size corresponding to the difference of the feedback signal with respect to the predetermined target signal as an adjustment signal. Then, the current control unit 139 supplies a current having a magnitude corresponding to the adjustment signal only to the selective resistance. That is, regardless of the value of the selection signal Sig, the current flowing through the selection resistance maintains the state of being negatively fed back by the negative feedback unit 120. Therefore, the drive circuit 109 in the present embodiment has an effect that the transition time between the on state and the off state can be suppressed when the current on / off drive type load is driven.
(Second Embodiment)
A second embodiment of the present invention based on the first embodiment of the present invention will be described. Here, the current control unit 139 in the first embodiment corresponds to the current adjustment unit 130 and the switching unit 160, which will be described later, in the present embodiment.

The configuration in this embodiment will be described.

FIG. 2 is a block diagram showing an example of the configuration of the drive circuit according to the second embodiment of the present invention.

The drive circuit 100 of the present embodiment drives one or more loads 200 according to the selection signal Sigma. The drive circuit 100 includes the same number of resistors 140 (first resistor) as the load 200, the resistor 150 (second resistor), the constant current conversion unit 110, and the same number of first feedback paths 510 as the load 200. , A second return path 520, a switching unit 160 (second switching means), and a switching unit 170 (first switching means). In FIG. 2, one load 200, one resistor 140 corresponding to the load 200, and one first feedback path 510 are exemplified as representatives.

The load 200 is a current on / off drive type load, and is, for example, a current drive type light emitting element such as an LED (Light Emitting Diode), a laser diode, or an organic electroluminescence.

Each resistor 140 corresponds one-to-one with each load 200. Each resistor 140 may include the internal resistance of each load 200.

The constant current conversion unit 110 converts each of the first current I1 and the second current I2 into a constant current based on the first signal S1 and the second signal S2, respectively.

Each first current I1 takes an on or off value and flows through each load 200 and each resistor 140 corresponding to each load 200 on a one-to-one basis. Each first signal S1 represents the magnitude of each first current I1. Each first signal S1 is, for example, each voltage V1 (potential difference) generated in each resistor 140 by each first current I1 flowing through each resistor 140.

The second current I2 flows through the resistor 150. The second signal S2 represents the magnitude of the second current I2. The second signal S2 is, for example, a voltage V2 (potential difference) generated in the resistor 150 by the second current I2 flowing through the resistor 150.

The constant current conversion unit 110 includes a current adjustment unit 130 and a negative feedback unit 120.

The current adjusting unit 130 adjusts each of the first current I1 and the second current I2. The current adjusting unit 130 includes, for example, a transistor or a vacuum tube amplifier. The current adjusting unit 130 is supplied with power from the DC constant voltage source 300.

The negative feedback unit 120 negatively feeds back each of the first signal S1 and the second signal S2 for the adjustment of the first current I1 and the second current I2. The negative feedback unit 120 includes, for example, an operational amplifier (operational amplifier).

Each first feedback path 510 feeds back each first signal S1 to the negative feedback section 120 of the constant current conversion section 110.

The second feedback path 520 feeds back the second signal S2 to the negative feedback section 120 of the constant current conversion section 110.

The switching unit 160 switches on or off of each of the first current I1 and the second current I2 according to the selection signal Sig. The selection signal Sig is a signal instructing either one of the first currents I1 to be on or all the first currents I1 to be off. That is, when the switching unit 160 is instructed to turn on one first current I1, the first current I1 is turned on, and all the first currents I1 and the second current I2 except the first current are turned on. Turn off. Further, when all the first currents I1 are instructed to be turned off, the switching unit 160 turns off all the first currents I1 and turns on the second current I2.

The switching unit 170 switches between enabling and disabling each of the first feedback path 510 and the second feedback path 520 according to the selection signal Sig. That is, when the switching unit 170 is instructed to turn on one first current I1, the switching unit 170 activates the first feedback path 510 that feeds back the first signal S1 representing the magnitude of the first current I1. The first feedback path 510 and the second feedback path 520 that feed back the first signal S1 representing the magnitude of each first current I1 excluding the first current I1 are invalidated. Further, when all the first currents I1 are instructed to be turned off, the switching unit 170 invalidates all the first feedback paths 510 and enables the second feedback path 520.

The other configurations in this embodiment are the same as the configurations in the first embodiment.

The operation in this embodiment will be described. Here, one load 200 and one resistor 140, a first feedback path 510, a first current I1, and a first signal S1 corresponding to the load 200 will be described.

When the selection signal Sig instructs the switching unit 160 to turn on the first current I1, the first current I1 is turned on by the switching unit 160, and the first current I1 and the second current I2 excluding the first current I1 are turned off. be. Further, at this time, the first feedback path 510 corresponding to the first current I1 is valid by the switching unit 170, and the first feedback path 510 and the second feedback path 520 excluding the first feedback path 510 are invalid. Is. That is, when the selection signal Sig instructs the first current I1 to be turned on, the constant current conversion unit 110 uses the first feedback path 510 to generate the first current I1 based on the first signal S1. Make it a constant current.

Further, when the selection signal Sig indicates that all the first currents I1 are turned off, all the first currents I1 are turned off and the second currents I2 are turned on by the switching unit 160. Further, at this time, all the first return paths 510 are invalid and the second return paths 520 are valid due to the switching unit 170. That is, when the selection signal Sig instructs to turn off all the first currents I1, the constant current conversion unit 110 uses the second feedback path 520 to make the second current I2 a constant current based on the second signal S2. To become.

The other operations in this embodiment are the same as the operations in the first embodiment.

As described above, in the drive circuit 100 of the present embodiment, the constant current conversion unit 110 utilizes either the first feedback path 510 or the second feedback path 520 regardless of the value of the selection signal Sig. By negatively feeding back either the first signal S1 or the second signal S2 to the constant current conversion unit 110, either the first current I1 or the second current I2 is converted to a constant current. As a result, the operating point of the negative feedback unit 120 of the constant current conversion unit 110 is within the normal operating range regardless of the value of the selection signal Sig. That is, in the negative feedback unit 120, there is no delay time for the operating point to return from outside the normal operating range to within the normal operating range. Therefore, the drive circuit 100 in the present embodiment has an effect that the transition time between the on state and the off state can be suppressed when the current on / off drive type load is driven.

The arrangement of the load 200, the resistor 140, and the resistor 150 in FIG. 2 is an example, and is not limited to the arrangement in FIG. In the drive circuit 100 of the present embodiment, the first current I1 may flow through each load 200 and the resistor 140 corresponding to the load 200, and the second current I2 may flow through the resistor 150.
(Third Embodiment)
A third embodiment of the present invention based on the second embodiment of the present invention will be described. In the drive circuit of the present embodiment, the constant current conversion unit is realized by an operational amplifier and one IGMP (Metal Oxide Semiconductor) transistor (hereinafter, also simply referred to as “NMOS”).

The configuration in this embodiment will be described.

FIG. 3 is a circuit diagram showing an example of the configuration of the drive circuit according to the third embodiment of the present invention.

The drive circuit 101 of the present embodiment has the same number of resistors 140 (first resistor) as the load 200, the resistor 150 (second resistor), the constant current conversion unit 111, and the same number of first resistors as the load 200. It includes a return path 510, a second return path 520, a switching unit 160 (second switching means), and a switching unit 170 (first switching means).

The constant current conversion unit 111 includes an MOSFET 131 (first N-channel type MOS transistor) which is an example of the current adjustment unit 130, and an operational amplifier 121 which is an example of the negative feedback unit 120.

The nanotube 131 regulates each of the first current I1 and the second current I2.

The operational amplifier 121 inputs a reference voltage V _ref (reference signal), and adjusts each first voltage V1 which is the first signal S1 and the second voltage V2 which is the second signal S2 to adjust the gate voltage of the nanotube 131. Negative feedback for. The reference voltage V _ref is a predetermined voltage. The reference voltage V _ref is input to the forward rotation input terminal of the operational amplifier 121. The first voltage V1 and the second voltage V2 are input to the inverting input terminal of the operational amplifier 121.

Each first feedback path 510 inputs each first current I1 from the output of the constant current conversion unit 111 via the switching unit 160, and inputs each first voltage V1 via the switching unit 170 to the operational amplifier 121. Output to the inverting input terminal of. It is assumed that the resistance value of each resistor 140 is R1. It is assumed that each internal resistance value r of each load 200 is sufficiently smaller than each resistance value R1 so as to be negligible, or is included in each resistance value R1.

In the second feedback path 520, the second current I2 is input from the output of the constant current conversion unit 111 via the switching unit 160, and the second voltage V2 is input to the inverting input of the operational amplifier 121 via the switching unit 170. Output to the terminal. It is assumed that the resistance value of the resistor 150 is R2.

The other configurations in the present embodiment are the same as the configurations in the second embodiment.

The operation in this embodiment will be described.

In the drive circuit 101 in this embodiment,
● When the selection signal Sig indicates that one first current I1 is turned on:
I1 = V _ref / R1 (for the first current I1),
I1 (for the first current I1 excluding the first current I1) = I2 = 0,
● When the selection signal Sig indicates that all the first currents I1 are turned off:
I1 = 0 (for all first currents I1),
I2 = V _ref / R2
Is.

The other operations in the present embodiment are the same as the operations in the second embodiment.

As described above, in the drive circuit 101 of the present embodiment, the constant current conversion unit 111 is realized by the operational amplifier 121 and one IGMP 131. Therefore, the drive circuit 101 in the present embodiment has the effect that the constant current conversion unit can be easily realized with an inexpensive and simple configuration, in addition to the effect in the drive circuit 100 in the second embodiment.
(Fourth Embodiment)
A fourth embodiment of the present invention based on the third embodiment of the present invention will be described. In the drive circuit of this embodiment, the number of each of the load 200, the resistor 140, and the first feedback path 510 is 1. Further, the switching unit 160 is realized by two inverters and two IGMPs (NMOS165 and 166 described later). Further, the switching unit 170 is realized by the same two inverters and two different nanotubes (NMOS 175 and 176 described later).

The configuration in this embodiment will be described.

FIG. 4 is a circuit diagram showing an example of the configuration of the drive circuit according to the fourth embodiment of the present invention.

In the drive circuit 103 of the present embodiment, the load 200 is one light emitting element 203. The drive circuit 103 includes one resistor 140 (first resistor), a resistor 150 (second resistor), a constant current conversion unit 111, one first feedback path 513, and a second feedback path 523. , Inverter 163 (first inverter), inverter 164 (second inverter), msgid 165 (third N-channel type MOS transistor), msgid 166 (fifth N-channel type MOS transistor), and NaCl 175 (second N-channel type MOS transistor). ) And the NaCl 176 (4th N channel type MOS transistor). The first switching means corresponds to the inverter 163 (first inverter), the inverter 164 (second inverter), the MOSFET 175 (the second N channel type MOS transistor), and the MOSFET 176 (the fourth N channel type MOS transistor). .. Further, the second switching means corresponds to the inverter 163 (first inverter), the inverter 164 (second inverter), the MOSFET 165 (third N channel type MOS transistor), and the MOSFET 166 (fifth N channel type MOS transistor). ..

In the present embodiment, the selection signal Sig is a signal instructing on or off of the first current I1.

The inverter 163 outputs an inverting signal V _off in which the selection signal Sigma is turned on and off.

The inverter 164 inputs an inverting signal V _off and outputs a forward rotation signal V _on in which the on and off of the inverting signal V _off are inverted.

The nanotube ₁₆₅ inputs a forward rotation signal Von to the gate and operates as a make contact of the switching unit 160.

The nanotube 166 inputs an inverting signal V _off to the gate and operates as a break contact of the switching unit 160.

The nanotube ₁₇₅ inputs a forward rotation signal Von to the gate and operates as a make contact of the switching unit 170.

The nanotube 176 inputs an inverting signal V _off to the gate and operates as a break contact of the switching unit 170.

The other configurations in the present embodiment are the same as the configurations in the third embodiment.

The operation in the present embodiment is the same as the operation in the third embodiment.

As described above, in the drive circuit 103 of the present embodiment, the switching unit 160 and the switching unit 170 are realized by two inverters and four MIMOs. Therefore, the drive circuit 103 in the present embodiment has an effect that it can operate at a higher speed in addition to the effect in the drive circuit 101 in the third embodiment.
(Fifth Embodiment)
Next, a fifth embodiment of the present invention based on the fourth embodiment of the present invention will be described. In the drive circuit of the present embodiment, the constant current conversion unit is arranged at a position different from that of the fourth embodiment, and has an independent N-channel type MOS transistor for each feedback path. Further, in the drive circuit of the present embodiment, the light emitting element is arranged at a position different from that of the fourth embodiment.

The configuration in this embodiment will be described.

FIG. 5 is a circuit diagram showing an example of the configuration of the drive circuit according to the fifth embodiment of the present invention.

In the drive circuit 107 of the present embodiment, when the selection signal Sigma for driving the light emitting element 203 (load) is at a high level (for lighting), the MOSFET 165 (third N channel type MOS transistor) and the MOSFET 175 (second N channel type MOS transistor) ) Is on and the MOSFET 166 (fifth N-channel type MOS transistor) and the MOSFET 176 (fourth N-channel type MOS transistor) are turned off to enable the feedback path 517 (the first feedback path that is effective when the light emitting element is lit). In addition, the feedback path 527 (the second feedback path that becomes effective when the light emitting element is turned off) is disabled. Further, when the selection signal Sig for driving the light emitting element 203 is at a low level (for turning off), the drive circuit 107 invalidates the feedback path 517 by turning off the nanotubes 165 and 175 and turning on the nanotubes 166 and 176. Moreover, the return path 527 is enabled and operates.

When the light emitting element 203 is lit, the return path 517 is activated. The return path 517 includes the nanotube 131 and the nanotube 175. The anode of the light emitting element 203 is connected to the high voltage output terminal of the DC constant voltage source 300. Further, the cathode of the light emitting element 203 is connected to the drain side of the nanotube 131. Further, the gate of the MFP 131 is connected to the output terminal of the operational amplifier 121. Further, the source of the nanotube 131 is connected between the nanotube 175 and the resistor 140 (first resistor). Further, the source of the NaCl 131 is connected to the low voltage output terminal of the DC constant voltage source 300 via the resistor 140. Further, the nanotube 131 and the resistor 140 are connected to the inverting input terminal of the operational amplifier 121 via the source and drain of the nanotube 175. Further, a reference voltage V _ref is given to the forward rotation input terminal of the operational amplifier 121.

When the light emitting element 203 is turned off, the return path 527 is activated. The feedback path 527 includes an MOSFET 137 (sixth N-channel type MOS transistor) and a MOSFET 176. The drain of the nanotube 166 is connected to the high voltage output terminal of the DC constant voltage source 300. Also, the source of the nanotube 166 is connected to the drain of the nanotube 137. The gate of the MFP 137 is connected to the output terminal of the operational amplifier 121. Further, the source of the nanotube 137 is connected between the nanotube 176 and the resistor 150 (second resistor), and is also connected to the low voltage output terminal of the DC constant voltage source 300 via the resistor 150. Also, the source of the nanotube 176 is connected between the nanotube 137 and the resistor 150. Further, the drain of the nanotube 176 is connected to the inverting input terminal of the operational amplifier 121.

The other configurations in the present embodiment are the same as the configurations in the fourth embodiment.

The operation in this embodiment will be described.

Each of µ By this switching operation, either the feedback path 517 or the feedback path 527 is enabled.

Since the forward rotation signal Von is at a high level when the light emitting element 203 is lit, the feedback path 517 becomes effective when the nanotube 175 is turned _on . Further, when the nanotube 165 is also turned on, the first current I1 flows through the path of the high voltage output terminal of the DC constant voltage source 300-NMOS1655-NMOS131-resistor 140-the low voltage output terminal of the DC constant voltage source 300.

On the other hand, when the light emitting element 203 is lit, the inverting signal V _off is at a low level, so that the feedback path 527 becomes invalid (blocked) when the nanotube 176 is turned off. Further, since the NaCl 166 is also turned off, the path of the second current I2 is cut off, and I2 = 0.

In the above state, due to the principle of virtual short circuit of the operational amplifier having a negative feedback path, the voltage of the inverting input terminal of the operational amplifier 121 (that is, the voltage applied to the resistor 140) becomes the voltage of the forward rotation input terminal (that is, V _ref ). Become equal. Therefore, assuming that the resistance value of the resistor 140 is R1, the first current I1 flowing through the light emitting element 203 is V _ref / R1.

When the light emitting element 203 is turned off, the forward rotation signal _Von is at a low level, so that the feedback path 517 becomes invalid (blocked) by turning off the nanotube 175. Further, since the NaCl 165 is also turned off, the path of the first current I1 is cut off, and I1 = 0.

On the other hand, when the light emitting element 203 is turned off, the inverting signal V _off is at a high level, so that the feedback path 527 becomes effective when the nanotube 176 is turned on. Further, when the nanotube 166 is also turned on, the second current I2 flows through the path of the high voltage output terminal of the DC constant voltage source 300-NMOS166-NMOS137-resistor 150-the low voltage output terminal of the DC constant voltage source 300.

In the above state, due to the principle of virtual short circuit of the operational amplifier having a negative feedback path, the voltage of the inverting input terminal of the operational amplifier 121 (that is, the voltage applied to the resistor 150) becomes the voltage of the forward rotation input terminal (that is, V _ref ). Become equal. Therefore, assuming that the resistance value of the resistor 150 is R2, the second current I2 is V _ref / R2.

Here, since the second current I2 may be the minimum current at which the negative feedback of the feedback path 527 functions effectively, it is generally set to I1 >> I2 by setting R1 << R2. Is possible.

The other operations in the present embodiment are the same as the operations in the fourth embodiment.

The drive circuit 107 in the present embodiment is not limited to the above-described configuration and operation, and can be modified as follows, for example.

In the above description, an example of driving one light emitting element 203 has been shown, but the drive circuit 107 may drive any number of light emitting elements 203 in parallel. In that case, the drive circuit 107 may include as many portions as the number of light emitting elements 203 in parallel, which are composed of the nanotubes 165, the nanotubes 131, the nanotubes 175, and the resistors 140. In this case, by enabling only one of the plurality of parallel feedback paths 517, it is possible to control the individual lighting or individual extinguishing state of each light emitting element 203.

Alternatively, the light emitting element 203 may be one in which a plurality of light emitting elements are connected in series.

The light emitting element 203 may be a current-driven light emitting element such as an LED, a laser diode, or an organic electroluminescence.

INDUSTRIAL APPLICABILITY The present invention can be used in an application for controlling a lighting / extinguishing state of a light emitting element. Further, the present invention can be used in an application for driving a current on / off drive type load.

100, 101, 103, 107, 109 Drive circuit 110, 111 Constant current conversion unit 120 Negative feedback unit 130 Current adjustment unit 139 Current control unit 200 Load 300 DC constant voltage source 203 Light emitting element 121 Operational amplifier 160, 170 Switching unit 131, 166, 165, 175, 137, 176 DBMS
140, 150 Resistor 163, 164 Inverter 300 DC constant voltage source 510, 513 1st feedback path 520, 523 2nd feedback path 517 Feedback path 527 Feedback path I1, I2 Current S1, S2 signal V1, V2 Voltage Sign selection signal V _ref reference voltage V _off inverting signal V _on forward rotation signal

Claims (5)

With at least one first resistor connected in series with each corresponding load,
The second resistor and
At least one of the first resistor and the second resistor is selected as the selection resistor according to the selection signal input from the outside, and a signal having a magnitude corresponding to the current flowing through the selection resistor is selected. As a feedback signal, the first switching means and
A negative feedback means that outputs a signal having a magnitude corresponding to the difference of the feedback signal with respect to a predetermined reference signal as an adjustment signal, and
It is provided with a current control means that supplies a current of a magnitude corresponding to the adjustment signal only to the selection resistor .
The current control means is
A current adjusting means for adjusting the current flowing through the selective resistance, and
A second that turns on the current flowing through the selection resistor in response to the selection signal and turns off the current flowing through all of the at least one first resistor and the second resistor except the selection resistor. With switching means
With,
Drive circuit. The current adjusting means includes a first N-channel type MOS (Metal Oxide Semiconductor) transistor that adjusts the current flowing through the selective resistance.
The negative feedback means inputs a reference voltage to the forward rotation input terminal, and adjusts a voltage proportional to the current flowing through the selective resistor input to the inverting input terminal to adjust the gate voltage of the first N channel type MOS transistor. The drive circuit according to claim 1 , further comprising a negative feedback operational amplifier. The first switching means outputs a voltage proportional to the current flowing through the selective resistance to the inverting input terminal of the operational amplifier.
The drive circuit according to claim 2 , wherein the second switching means outputs a current output from the current adjusting means to the selective resistance. The at least one first resistor is one.
The first switching means and the second switching means are
A first inverter that outputs an inverted signal obtained by inverting the on and off of the selection signal, and
It includes a second inverter that outputs a forward rotation signal in which the on and off of the inverted signal are inverted.
The first switching means is
A second N-channel type MOS transistor that inputs the forward rotation signal to the gate and operates as a make contact of the first switching means.
A fourth N-channel type MOS transistor that inputs the inverted signal to the gate and operates as a break contact of the first switching means is included.
The second switching means is
A third N-channel type MOS transistor that inputs the forward rotation signal to the gate and operates as a make contact of the second switching means.
A fifth N-channel type MOS transistor that inputs the inverting signal to the gate and operates as a break contact of the second switching means.
including,
The drive circuit according to claim 3 . The current adjusting means further includes a sixth N-channel type MOS transistor that adjusts the current flowing through the second resistor.
Each of the first N-channel type MOS transistors controls the current flowing through each of the at least one first resistor.
The operational amplifier
The gate voltage of the first N-channel type MOS transistor is controlled and the gate voltage of the first N-channel type MOS transistor is controlled based on either the reference voltage and a voltage proportional to the current flowing through each of the at least one first resistor.
The drive circuit according to any one of claims 2 to 4 , wherein the gate voltage of the 6N channel type MOS transistor is controlled based on the reference voltage and the voltage proportional to the current flowing through the second resistor.

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