JP2001308384A - Light emitting element drive control device - Google Patents

Abstract

(57) Abstract: In a light-emitting element drive control device that drives a plurality of LEDs such as a backlight by pulse driving, it is intended to reduce switching noise and the like. SOLUTION: A first pulse signal Sa generated by a first pulse signal generation unit 4a and a second pulse signal Sb generated by a second pulse signal generation unit 4b are converted into a first AND gate 1, The signal is input to a driving unit including the second AND gate 2 and the inverter 3. Further, the cycle of the second pulse signal Sb is set to be twice as long as the first pulse signal Sa. As a result, a pulse signal having a phase shift is output from the first AND gate 1 and the second AND gate 2, and the switching transistors TR1 and TR2 are alternately turned on and off, thereby generating switching noise. Disperse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a light emitting device, and more particularly, to drive control of an LED (light emitting diode) used for a backlight of a liquid crystal display device (LCD).

[0002]

2. Description of the Related Art FIG. 10 shows an example of a conventional light emitting element drive control device comprising a plurality of LEDs. As shown, in this example, one LED circuit including three LEDs (LEDs 21, 22, and 23), a switching transistor TR21, and a resistor R22, and three LEDs (LEDs 24,
25, 26) and another LED circuit including a switching transistor TR22 and a resistor R23 are connected in parallel, and one end of the parallel-connected LED circuit is connected to a DC power supply Vcc (DC) of a predetermined voltage via a resistor R21. ). A drive control signal generating means mainly composed of a microcomputer is provided on the other end side of the LED circuit connected in parallel.
The drive control signal S11 in the form of a pulse is input from the
22 or a resistor R23 to the base of the transistor TR21 or the transistor TR22, respectively.
Is turned on and off.

[0003]

However, in the conventional light emitting element drive control device, a plurality of LEDs are required.
There is a disadvantage that the switching noise of the transistors TR21 and TR22 is concentrated because the (LED21 to LED26) are turned on and off all at once. Further, under the conventional configuration, when the voltage of the DC power supply Vcc fluctuates, it is directly affected by the fluctuation and the brightness of the LED light emission fluctuates, or some of the LEDs fail and no longer light up. In this case, the LED connected in series with the LED also does not turn on, and the overall brightness decreases.In addition, even if the surrounding brightness changes, the brightness of the LED light emission is constant, and the surrounding brightness decreases. There was a drawback that the brightness could not be adjusted according to the brightness. SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting element drive control device which improves the above-mentioned disadvantages.

[0004]

According to the present invention, a plurality of LEDs (light emitting diodes) are connected in series to the collector of a first transistor for switching, and the other end of the plurality of LEDs connected in series is connected via a resistor. A plurality of LEDs are connected in series to a first LED circuit to which a DC power is applied and a collector of a second transistor for switching. A second LED circuit to which power is applied, a first pulse signal having a predetermined pulse width, and a first pulse signal for ON / OFF control of the first transistor or the second transistor; A drive control signal generating means for generating, as a drive control signal, a second pulse signal having a preset pulse width twice as long as the signal, and driving by the drive control signal generating means And a drive unit for outputting a drive signal for alternately turning on or off the first transistor and the second transistor to the base of the first transistor or the base of the second transistor based on the control signal. The LED of the first LED circuit and the LE of the second LED circuit
The present invention provides a light-emitting element drive control device that turns on and off D alternately.

Further, the drive control signal generating means includes a first pulse signal generating section for generating the first pulse signal, a second pulse signal generating section for generating the second pulse signal, A control unit controls the first pulse signal generation unit and the second pulse signal generation unit.

In addition, a DC power is applied to the first LED circuit via a first resistor, and a DC power is applied to the second LED circuit via a second resistor. An A / D conversion section and a determination section are provided below the control section of the control signal generation means, while the first resistor and the first LE are provided.
The voltage at each of the connection point with the D circuit and the connection point between the second resistor and the second LED circuit is input to the drive control signal generation means as a failure detection voltage, and in the drive control signal generation means, The A / D converter converts each of the failure detection voltages into digital data, and the converted data is compared with a reference value by the determination unit to determine the failure detection voltage of one of the LED circuits. Is determined to exceed the reference value, the pulse width of the first pulse signal is increased, and the lighting period of the other LED circuit is lengthened.

[0007] The driving unit may further include an inverter for inverting the second pulse signal, and a signal obtained by calculating a logical product of the signal from the inverter and the first pulse signal. And a second AND gate for sending a logical product of the first pulse signal and the second pulse signal to the base of the second transistor. Constitute.

Further, the pulse width of the second pulse signal is set to one half of one cycle.

The present invention also provides an LED circuit in which a plurality of LEDs are connected in series to the collector of a switching transistor, and a DC power is applied from the other end of the plurality of LEDs connected in series via a resistor; Drive control signal generating means for generating a sawtooth drive control signal with a variable upper limit,
A drive unit that outputs a drive signal to turn on or off the transistor to the base of the transistor based on a drive control signal from the drive control signal generation unit, and an upper limit value of the sawtooth drive control signal. The present invention provides a light-emitting element drive control device that controls the brightness of light emission of the plurality of LEDs by varying the light emitting element driving power.

The drive control signal generating means comprises a sawtooth wave generator for generating the sawtooth drive control signal, and a controller for controlling the sawtooth wave generator.

An A / D conversion section and a comparison section are provided below the control section of the drive control signal generating means, and a resistance division circuit for dividing the DC power supplies for the plurality of LEDs by resistance is provided. The divided voltage by the dividing circuit is input to the drive control signal generating means. In the drive control signal generating means, the divided voltage is converted into digital data by the A / D converter, and the converted data is converted into the digital data. The comparison unit compares the reference value with the reference value, changes the upper limit value of the sawtooth-shaped drive control signal in accordance with the fluctuation in the comparison, and controls the brightness of the light emission of the plurality of LEDs to be constant.

An A / D conversion section and a comparison section are provided below the control section of the drive control signal generating means, and an optical sensor for detecting the brightness of ambient light is provided. Is input to the drive control signal generation means. In the drive control signal generation means, the detection signal is converted into digital data by the A / D conversion unit, and the converted data is compared with a reference value by the comparison unit. And varying the upper limit value of the sawtooth drive control signal according to the variation in the comparison,
The brightness of the light emitted from the plurality of LEDs is controlled according to the brightness of the ambient light.

Further, the drive section receives a sawtooth-shaped drive control signal from the drive control signal generating means at a positive-phase input terminal and a negative-phase input terminal based on the DC power supply for the plurality of LEDs. And an operational amplifier that applies a stabilized DC voltage to the transistor and sends a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage to the base of the transistor.

The DC voltage applied to the negative-phase input terminal is a voltage across a Zener diode connected to the DC power supply for the plurality of LEDs via a resistor.

Alternatively, a sawtooth drive control signal from the drive control signal generating means is input to a positive-phase input terminal, and the plurality of LED DC power supplies are resistance-divided to a negative-phase input terminal. An operational amplifier that applies a predetermined DC voltage and sends a pulse signal having a pulse width during a period when the drive control signal exceeds the DC voltage to a base of the transistor.

Also, a sawtooth-shaped drive control signal from the drive control signal generating means is input to a positive-phase input terminal of the drive unit, and an optical sensor for detecting the brightness of ambient light is provided at a negative-phase input terminal of the drive unit. And an operational amplifier for transmitting a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage related to the detection signal to the base of the transistor, according to the detection signal. The plurality of LEDs
To control the brightness of the light emission.

Further, according to the present invention, a plurality of LEDs are connected in series to the collector of the first transistor for switching, and a DC power is applied from the other end of the plurality of LEDs connected in series via a resistor. One LED circuit and a plurality of LEDs connected to a collector of a second transistor for switching.
Are connected in series, and a second LED to which DC power is applied from the other end of the plurality of LEDs connected in series via the resistor
A circuit and a signal for on / off control of the first transistor or the second transistor, the signal being a sawtooth first signal.
And a second signal, which is a pulse signal having a predetermined pulse width of the same period as the sawtooth signal, as a drive control signal; and a drive control signal generating means. A drive unit for outputting a drive signal for alternately turning on or off the first transistor and the second transistor to the base of the first transistor or the base of the second transistor based on the drive control signal of And the LED of the first LED circuit and the second LE
An object of the present invention is to provide a light emitting element drive control device for alternately turning on or off LEDs of a D circuit.

Further, the driving control signal generating means includes a sawtooth wave generating section for generating the first signal, a pulse signal generating section for generating the second signal, the sawtooth wave generating section and the pulse signal generating section. And a control unit that controls the unit.

In addition, DC power is applied to the first LED circuit via a first resistor, DC power is applied to the second LED circuit via a second resistor, and the An A / D conversion section and a determination section are provided below the control section of the control signal generation means, while the first resistor and the first LE are provided.
The voltage at each of the connection point with the D circuit and the connection point between the second resistor and the second LED circuit is input to the drive control signal generation means as a failure detection voltage, and in the drive control signal generation means, The A / D converter converts each of the failure detection voltages into digital data, and the converted data is compared with a reference value by the determination unit to determine the failure detection voltage of one of the LED circuits. Is determined to exceed the reference value, the upper limit value of the sawtooth-shaped first signal is increased, and the lighting period of the other LED circuit is extended.

Further, the driving section receives the sawtooth-shaped first signal from the drive control signal generating means at a positive-phase input terminal and a DC power supply for the plurality of LEDs at a negative-phase input terminal. An operational amplifier that applies a preset DC voltage stabilized to the above, outputs a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage, and an inverter that inverts the second signal. A first AND gate for transmitting a logical product of the signal from the inverter and the signal from the operational amplifier to the base of the first transistor; A second AND gate for transmitting a signal obtained by ANDing the signal with the signal to the base of the second transistor.

[0021]

Embodiments of the present invention will be described below with reference to the drawings based on embodiments. FIG. 1 is a block diagram of a main part of a first embodiment of a light emitting element drive control device according to the present invention for reducing switching noise, and FIG. 2 is a time chart for explaining FIG. FIG. 3 is a block diagram of a main part of a second embodiment of a light emitting element drive control device according to the present invention, showing a basic configuration of controlling the brightness (hereinafter, referred to as illuminance) of LED light emission.
Is a time chart for explaining FIG. Also,
FIG. 5 is a main block diagram showing a basic configuration of illuminance control with respect to a voltage change of a DC power supply Vcc according to a third embodiment of the light emitting element drive control device according to the present invention.

FIG. 6 is a block diagram of a main part of a fourth embodiment of the light emitting element drive control device according to the present invention, showing a basic configuration of illuminance control with respect to fluctuation of ambient light. Also,
FIG. 7 is a block diagram of a main part of a fifth embodiment of the light emitting element drive control device according to the present invention, which is another method of FIG. Also,
FIG. 8 is a block diagram of a main part of a sixth embodiment of the light emitting element drive control device according to the present invention, which is based on the configuration of FIG. 1 and partially copes with LED failure. FIG.
Is a seventh embodiment of the light emitting element drive control device according to the present invention, which incorporates the configuration of FIG. 3 into the configuration of FIG. 8, and has a configuration for reducing switching noise or partially coping with LED failure. It is a principal part block diagram.

Hereinafter, each operation of the present invention will be described.
First, a basic configuration and operation for reducing switching noise will be described. In FIG. 1, a DC power supply Vcc, a resistor
R1 to R3, the light emitting diodes LED1 to LED6, and the switching transistors TR1 and TR2 are conventional (FIG. 1).
0). For this circuit, as shown in the figure, a drive unit including a first AND gate 1 (hereinafter, AND gate 1), a second AND gate 2 (hereinafter, AND gate 2), and an inverter 3 is provided. , AND gate 1
A first pulse signal Sa and a second pulse signal Sb, which are drive control signals generated by the drive control signal generating means 4, are applied to one input ends of the AND gate 2 and the input terminal. The drive control signal generating means 4 is mainly composed of a microcomputer (hereinafter, referred to as a microcomputer).
A first pulse signal generator 4a for generating the first pulse signal Sa as shown in FIG.
A second pulse signal generator 4b for generating the pulse signal Sb, and a controller 4c for controlling these generators.

FIG. 2 shows the waveforms of the first pulse signal Sa and the second pulse signal Sb. As shown in the drawing, the period Tb of the second pulse signal Sb is twice the period Ta of the first pulse signal Sa, and the pulse width of the second pulse signal Sb is one half of the period Tb. It is set to 1. This allows
A control signal obtained by inverting the first pulse signal Sa and the second pulse signal Sb by the inverter 3 is applied to the AND gate 1, and the first pulse signal Sa and the second pulse signal Sb are applied to the AND gate 2. Is applied. As a result, the transistor
A pulse signal having the waveform shown in FIG. 2 is applied to the bases of TR1 and TR2, and each of them is turned on in a positive pulse period. As shown in the figure, the ON timing of the pulse signal applied to the base of TR1 or TR2 is shifted. Thereby, the LED group A (LED1 to LED3) or the LED group B (LED4 to LED4)
LED 6) alternately turns on (lights up) or turns off (lights out),
Since all the LEDs are not turned on and off at the same time as in the related art, the generation of the switching noise of TR1 and TR2 is dispersed, and the influence of the noise can be reduced.

Next, control of brightness (illuminance) of LED light emission will be described. FIG. 3 shows a basic configuration of the illuminance control. FIG. 3 shows an example of an LED circuit having three LEDs. The collector of the switching transistor TRa includes resistors Ra and LE.
Da, LEDb and LEDc are provided in series, and the resistance Ra
Is supplied with a DC power supply Vcc. Further, an operational amplifier 5 as a driving unit for driving the TRa is provided as shown in the figure,
Its positive-phase input terminal (+ end) type drive control signal Sc from the drive control signal generating means 6, the reverse phase input terminal - min and the DC power source Vcc resistor Rc and the Zener diode Da is the (end) The compressed predetermined voltage Va is applied. Its output signal is a resistor Rb
Is applied to the base of TRa. If it is not necessary to stabilize the voltage Va at the negative-phase input terminal, a resistor (resistance division—not shown) may be used instead of the Zener diode Da. The drive control signal generating means 6 is mainly formed of a microcomputer, and generates a sawtooth-shaped drive control signal Sc as shown in the figure, and a control unit for controlling the sawtooth wave generator 6a.
6b.

FIG. 4 shows the waveforms of the drive control signal Sc, the divided DC voltage Va at the negative-phase input terminal (-terminal), and the base voltage of TRa. As shown in the figure, the drive control signal Sc output by the sawtooth wave generator 6a is a sawtooth wave with a constant cycle Ta, and the lower limit is fixed and the upper limit is variable as shown in FIGS. Signal. The relationship between the drive control signal Sc and the divided DC voltage Va is as illustrated. As a result, the operational amplifier 5 outputs a pulse (saturated output) for a period in which the drive control signal Sc exceeds the divided DC voltage Va. Therefore, if the upper limit changes as shown in a, b, and c, the pulse width of this pulse output will be different. The variable pulse width signal is applied as the base voltage of TRa, and during the period of the same pulse width, LEDa to LEDc are turned on. In this case, if the pulse width is widened, the on-period of TRa becomes longer and the illuminance rises. Conversely, if the pulse width is made narrower, the on-period of TRa becomes shorter and the illuminance lowers. As described above, the illuminance is controlled by changing the upper limit value of the drive control signal Sc.

Next, the illuminance control for the fluctuation of the DC power supply Vcc utilizing the configuration of the illuminance control (FIG. 3) will be described with reference to FIG. FIG. 5 shows the configuration of FIG. 3 in which resistors Rd and Re for dividing the DC power supply Vcc are provided, and the divided voltage is input to the drive control signal generating means 7 as power supply voltage fluctuation data. The same components as those in FIG. 3 are denoted by the same reference numerals. The drive control signal generating means 7 is mainly formed by a microcomputer, and includes an A / D converter 7a, a comparator 7b, a sawtooth wave generator 7c for generating a sawtooth drive control signal Sc having the same function as in FIG. Control unit 7d that controls each function block
And In the drive control signal generating means 7,
The power supply voltage fluctuation data input by the A / D conversion unit 7a is converted into digital data, and the comparison unit 7b compares the digital data with a preset reference value. The drive control signal Sc set in FIG. 4)
Is generated by the sawtooth wave generator 7c and output to the positive-phase input terminal (+ terminal) of the operational amplifier 5. In this case, when the DC power supply Vcc decreases, and therefore the divided voltage also decreases, the drive control signal Sc in which the upper limit is higher than the standard value by a required value is output. When the voltage also rises, a drive control signal Sc in which the upper limit is lower than the standard value by a required value is output. Thus, the on-period of TRa is adjusted by the amount of change in DC power supply Vcc, and the illuminance of the LED is stabilized.

Next, the illuminance control that follows the ambient light using the configuration of the illuminance control (FIG. 3) will be described with reference to FIG. FIG. 6 shows the configuration of FIG. 3 in which an optical sensor 8 for detecting ambient light is provided, and the voltage output of the optical sensor 8 is input to the drive control signal generating means 9 as ambient light data. The same components as those in FIG. 3 are denoted by the same reference numerals. The drive control signal generating means 9 is mainly formed by a microcomputer, and includes an A / D converter 9a, a comparator 9b, a sawtooth wave generator 9c for generating a sawtooth drive control signal Sc having the same function as in FIG. A control unit 9d for controlling each functional block. The drive control signal generating means 9 converts the ambient light data input by the A / D converter 9a into digital data, and compares the digital data with a preset reference value in a comparator 9b. The drive control signal Sc set to the upper limit value according to the comparison is generated by the sawtooth wave generator 9c and output to the positive-phase input terminal (+ terminal) of the operational amplifier 5. In this case, when the ambient light decreases (darkens) and the voltage output of the optical sensor 8 decreases, the drive control signal Sc in which the upper limit is higher than the standard value by a required value is output, and conversely, the ambient light increases (brightens). Then, when the voltage output of the optical sensor 8 increases, the drive control signal in which the upper limit is lower than the standard value by a required value.
Output Sc. Thereby, the ON period of TRa is adjusted by the amount of fluctuation of the ambient light, and the illuminance of the LED is stabilized.

Alternatively, as an alternative to the configuration of FIG.
It is good also as composition of. FIG. 7 shows a configuration in which the voltage output of the optical sensor 8 is input to the negative-phase input terminal (-terminal) of the operational amplifier 5 in the configuration of FIG. The same components as those in FIG. 3 or FIG. 6 are denoted by the same reference numerals. With this configuration, the potential at the negative-phase input terminal (−terminal) fluctuates according to the ambient light, and the same potential decreases when the ambient light decreases (darkens), and increases when the ambient light increases (brightens). . When this variation is applied to FIG. 4, the divided DC voltage Va becomes the voltage output of the optical sensor 8. Therefore, if the voltage output of the optical sensor 8 increases, the pulse width of the pulse voltage applied to TRa becomes narrower, whereby the illuminance decreases. If the voltage output of the optical sensor 8 decreases, the pulse width of the pulse voltage applied to TRa decreases. Wider, which increases the illuminance. Thereby, the illuminance of the LED is stabilized even if the ambient light fluctuates.

Next, illuminance control for some LED failures will be described with reference to FIG. FIG. 8 is based on the configuration of FIG. 1 and has a function of detecting an LED failure.
Specifically, a first resistor R1 and a second resistor R2 are provided as shown in the figure, and an anode of LED1 which is a connection point with the same resistor R1 and an anode of LED4 which is a connection point with the same resistor R2 are respectively provided. The voltage fluctuation is input to the drive control signal generator 10 as failure detection data. The same components as those in FIG. 1 are denoted by the same reference numerals. The drive control signal generating means 10 is mainly formed by a microcomputer, and includes an A / D converter 10.
a, a determination unit 10b, a first pulse signal generation unit 10c for generating the first pulse signal Sa, a second pulse signal generation unit 10d for generating the second pulse signal Sb, and control of these functional blocks And a control unit 10e for performing the operation.

In the drive control signal generating means 10,
The A / D converter 10a converts each of the input failure detection data into digital data, and the determination unit 10b compares each of the digital data with a preset reference value. If any one of the LEDs fails and enters an open state, no current flows, so the voltage at the anode of each of the LEDs 1 or 4 rises and exceeds the reference value. The determination unit 10b determines that the reference value has been exceeded. In accordance with the determination, the pulse width of the first pulse signal Sa generated by the first pulse signal generator 10c under the control of the controller 10e is expanded to a predetermined width. Thereby, the illuminance of the LED group on the normal side increases, and the decrease in illuminance due to the failure is compensated. Other operations are the same as those in FIG.

Next, another method of reducing the switching noise or controlling the illuminance for the failure of some LEDs will be described with reference to FIG. FIG. 9 is a configuration obtained by incorporating the configuration of FIG. 3 into the configuration of FIG. 8. Specifically, the configuration of the drive control signal generating means 11 and the drive unit are different. The same components as those in FIG. 8 or FIG. 3 are denoted by the same reference numerals. As shown in the drawing, the drive control signal generating means 11 is replaced with the first pulse signal generating section 10c in the configuration of FIG.
Is provided with a sawtooth wave generator 11c for generating the signal Sd of FIG. The pulse signal generator 11d generates a second signal Se which is the same pulse signal as the second pulse signal Sb.
Other A / D conversion unit 11a, determination unit 11b, and control unit 11e
Is the same as that of FIG. In addition, the drive unit
An AND gate 1, an AND gate 2, an inverter 3, and an operational amplifier 5 are connected and configured as shown in the figure. Also,
The negative-phase input terminal (-terminal) of the operational amplifier 5 is stabilized to a predetermined voltage Va by the Zener diode Da and the resistor R5 as in FIG.

The sawtooth-wave-shaped first signal Sd of the sawtooth-wave generator 11c is input to the positive-phase input terminal (+ end) of the operational amplifier 5, and the second signal Se, which is a pulse signal, is supplied to the AND gate 2 and Input to the inverter 3. The operational amplifier 5 outputs the same pulse signal as the first pulse signal Sa by the operation of FIG. Therefore, after the output of the operational amplifier 5, the operation is the same as that of FIG. 8 (that is, FIG. 1), whereby
The LED group A (LED1 to LED3) or the LED group B (LED4 to LED6) are alternately turned on (lit) or turned off (extinguished), dispersing the generation of switching noise of TR1 and TR2 as in FIG. Reduce the effect of the noise. The A / D of the drive control signal generating means 11 uses the voltage fluctuations of the anode of the LED 1 as a connection point with the first resistor R1 and the anode of the LED 4 as a connection point with the second resistor R2 as failure detection data. It is input to the conversion unit 11a. As a result, the same operation as in FIG.
When the ED fails, the illuminance of the LED group on the normal side increases and compensates for the decrease in illuminance due to the failure. Other operations are the same as those in FIG. 1, FIG. 3, or FIG.

[0034]

As described above, according to the present invention, a plurality of LEDs are turned on and off alternately for each LED block without turning on and off all at once, so that switching noise generated by the switching transistors does not concentrate. Also, when the DC power supply fluctuates in voltage, L
Automatically corrects and stabilizes the brightness of ED emission. In addition, even if the surrounding brightness changes, the LED emission is controlled to follow the brightness. In addition, when some of the LEDs fail to stop lighting due to a failure, it is detected, and the LED on the normal side is detected.
Increase the brightness of the ED to compensate for the decrease in overall brightness.
Thus, it can be said that the present invention can contribute to the performance improvement of the light emitting element drive control device.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing a first embodiment of a light emitting element drive control device according to the present invention.

FIG. 2 is a time chart for explaining FIG. 1;

FIG. 3 is a main part block diagram showing a second embodiment of the light emitting element drive control device according to the present invention.

FIG. 4 is a time chart for explaining FIG. 3;

FIG. 5 is a main part block diagram showing a third embodiment of the light emitting element drive control device according to the present invention.

FIG. 6 is a main part block diagram showing a fourth embodiment of the light emitting element drive control device according to the present invention.

FIG. 7 is a main part block diagram showing a fifth embodiment of the light emitting element drive control device according to the present invention.

FIG. 8 is a main part block diagram showing a sixth embodiment of the light emitting element drive control device according to the present invention.

FIG. 9 is a main part block diagram showing a light emitting element drive control device according to a seventh embodiment of the present invention.

FIG. 10 is a main block diagram showing an example of a conventional light emitting element drive control device.

[Explanation of symbols]

1, 2 AND gate 3 Inverter 4, 6, 7, 9, 10, 11, 21 Drive control signal generating means 4a, 4b, 10c, 10d, 11d Pulse signal generating sections 6a, 7c, 9c, 11c Saw wave generating section 7a , 9a, 10a, 11a A / D conversion unit 7b, 9b Comparison unit 10b, 11b Judgment unit 4c, 6b, 7d, 9d, 10e, 11e Control unit 5 Operational amplifier 8 Optical sensor TR1, TR2, TRa, TR21, TR22 Transistor R1 ~ R4, Ra ~ Re, R21 ~ R23 Resistance LED1 ~ LED6, LEDa ~ LEDc, LED21 ~ LED26 Light emitting diode Da Zener diode

Claims (17)

[Claims] A plurality of LEDs (light emitting diodes) are connected in series to the collector of a first transistor for switching, and a DC power supply is applied from the other end of the plurality of LEDs connected in series via a resistor. One LED circuit and a plurality of L
EDs are connected in series, and a second LED to which a DC power is applied from the other end of the plurality of LEDs connected in series via the resistor.
An ED circuit, a signal for ON / OFF control of the first transistor or the second transistor, a first pulse signal having a preset pulse width, and a first pulse signal having a cycle twice as long as the first pulse signal. A drive control signal generating means for generating a second pulse signal having a set pulse width as a drive control signal; and the first transistor and the second transistor based on a drive control signal from the drive control signal generating means. And a drive unit for outputting a drive signal for alternately turning on or off the transistor to the base of the first transistor or the base of the second transistor.
A light emitting element drive control device, wherein D and the LED of the second LED circuit are alternately turned on or off. 2. The driving control signal generating means according to claim 1,
A first pulse signal generator for generating a pulse signal of the following, a second pulse signal generator for generating the second pulse signal, a first pulse signal generator and a second pulse signal generator. 2. The light emitting element drive control device according to claim 1, further comprising a control unit for controlling the light emitting element driving. 3. A DC power supply is applied to the first LED circuit via a first resistor, and a DC power supply is applied to the second LED circuit via a second resistor. An A / D conversion section and a determination section are provided below the control section of the control signal generation means, while a connection point between the first resistor and the first LED circuit and the second resistor and a second LED circuit are provided. The voltage at each of the connection points is input to the drive control signal generation means as a failure detection voltage. In the drive control signal generation means, the A / D converter converts each of the failure detection voltages into digital data. Then, each of the converted data is compared and determined by the determination unit with a reference value, and when it is determined that the failure detection voltage of one of the LED circuits exceeds the reference value, the first pulse signal is output. The pulse width of The light emitting element drive control device according to claim 1 or 2, wherein a lighting period of the LED circuit is extended. 4. A driving circuit comprising: an inverter for inverting the second pulse signal; and a signal obtained by calculating a logical product of the signal from the inverter and the first pulse signal. And a second AND gate for sending a logical product of the first pulse signal and the second pulse signal to the base of the second transistor. The light-emitting element drive control device according to claim 1, wherein the control device is configured. 5. The pulse width of the second pulse signal is 1
4. The light emitting element drive control device according to claim 1, wherein the period is set to a half of the period. 6. An LED circuit in which a plurality of LEDs are connected in series to a collector of a switching transistor, and a DC power is applied from the other end of the plurality of LEDs connected in series via a resistor, and an upper limit value is variable. Drive control signal generating means for generating a sawtooth-shaped drive control signal, and a drive signal for turning on or off the transistor is output to the base of the transistor based on the drive control signal from the drive control signal generating means. And a driving unit, and the upper limit value of the sawtooth-shaped drive control signal is changed to thereby control the plurality of LEDs.
A light-emitting element drive control device for controlling the brightness of light emission of a light-emitting element. 7. The drive control signal generating means comprises a sawtooth wave generating section for generating the sawtooth drive control signal, and a control section for controlling the sawtooth wave generating section. 7. The light emitting element drive control device according to 6. 8. An A / D conversion section and a comparison section are provided below a control section of the drive control signal generation means, and a resistance division circuit for dividing the DC power supplies for the plurality of LEDs by resistance is provided. The divided voltage by the dividing circuit is input to the drive control signal generating means. In the drive control signal generating means, the divided voltage is converted into digital data by the A / D converter, and the converted data is converted into the digital data. A comparison unit compares the reference value with the reference value, and varies an upper limit value of the sawtooth-shaped drive control signal in accordance with a change in the comparison to control the brightness of the plurality of LEDs to be constant. The light-emitting element drive control device according to claim 6 or 7, wherein: 9. An A / D conversion section and a comparison section are provided under a control section of the drive control signal generation means, and an optical sensor for detecting brightness of ambient light is provided, and a detection signal from the optical sensor is provided. Is input to the drive control signal generation means. In the drive control signal generation means, the detection signal is converted into digital data by the A / D conversion unit, and the converted data is compared with a reference value by the comparison unit. An upper limit value of the sawtooth drive control signal is varied according to a variation in the comparison, and brightness of the plurality of LEDs is controlled according to brightness of the ambient light. The light-emitting element drive control device according to claim 6 or 7. 10. The driving unit receives a sawtooth-shaped drive control signal from the drive control signal generation means at a positive-phase input terminal and a negative-phase input terminal based on a DC power supply for the plurality of LEDs. A stable DC voltage is applied to the transistor, and the operational control amplifier is configured to transmit a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage to a base of the transistor. Claims 6 and 8
A light-emitting element drive control device according to claim 9. 11. The DC voltage applied to the negative-phase input terminal is a voltage across a Zener diode connected to a DC power supply for the plurality of LEDs via a resistor. Light emitting element drive control device. 12. The driving section, wherein a sawtooth drive control signal from the drive control signal generating means is input to a positive-phase input terminal, and a DC power supply for the plurality of LEDs is resistance-divided at a negative-phase input terminal. 7. An operational amplifier for applying a predetermined DC voltage and sending a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage to a base of the transistor. A light-emitting element drive control device according to claim 1. 13. An optical sensor for inputting a sawtooth-shaped drive control signal from the drive control signal generating means to a positive-phase input terminal and detecting a brightness of ambient light at a negative-phase input terminal. And an operational amplifier for transmitting a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage related to the detection signal to the base of the transistor, according to the detection signal. The plurality of LEDs
7. The light emitting element drive control device according to claim 6, wherein the light emission brightness is controlled. 14. A first LED circuit in which a plurality of LEDs are connected in series to a collector of a first transistor for switching, and a DC power is applied from the other end of the plurality of LEDs connected in series via a resistor. And a second for switching
A second LED circuit in which a plurality of LEDs are connected in series to the collector of the transistor, and DC power is applied from the other end of the plurality of LEDs connected in series via the resistor; and the first transistor or the second transistor. And a second signal which is a pulse signal having a predetermined pulse width of the same period as the sawtooth signal, which is a signal for on / off control of the second transistor. A driving control signal generating means for generating a signal, and a driving signal for turning on or off the first transistor and the second transistor alternately based on the driving control signal from the driving control signal generating means. A driving unit for outputting to the base of the first transistor or the base of the second transistor, and the LED of the first LED circuit and the LE of the second LED circuit.
A light emitting element drive control device characterized in that D and D are alternately turned on or off. 15. The driving control signal generating means includes a sawtooth wave generating section for generating the first signal, a pulse signal generating section for generating the second signal, the sawtooth wave generating section, and a pulse signal generating section. 15. The light emitting element drive control device according to claim 14, wherein the control unit controls the light emitting element. 16. A DC power supply is applied to the first LED circuit via a first resistor, and a DC power supply is applied to the second LED circuit via a second resistor. An A / D converter and a determination unit are provided below the control unit of the control signal generation unit, while the first resistor and the first LED are provided.
A voltage at each of a connection point with a circuit and a connection point between the second resistor and the second LED circuit is input to the drive control signal generation means as a failure detection voltage, and in the drive control signal generation means, The A / D converter converts each of the failure detection voltages into digital data, and the converted data is compared with a reference value by the determination unit to determine whether the failure detection voltage of one of the LED circuits is higher than the reference value. 16. The method according to claim 14, wherein when it is determined that the reference value has been exceeded, an upper limit value of the sawtooth-shaped first signal is increased, and a lighting period of the other LED circuit is lengthened. Light emitting element drive control device. 17. The driving section, wherein a sawtooth-shaped first signal from the drive control signal generating means is input to a positive-phase input terminal,
A predetermined DC voltage stabilized based on the DC power supplies for the plurality of LEDs is applied to the negative phase input terminal, and a pulse signal having a pulse width in a period in which the drive control signal exceeds the DC voltage is applied. An operational amplifier for outputting, an inverter for inverting the second signal, and a first signal for transmitting a logical product of a signal from the inverter and a signal from the operational amplifier to a base of the first transistor. And a second AND gate for transmitting a signal obtained by ANDing the signal from the operational amplifier and the second signal to the base of the second transistor. The light-emitting element drive control device according to claim 14 or 16, wherein: