JP2016024931A - Led array driving circuit - Google Patents

Led array driving circuit Download PDF

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JP2016024931A
JP2016024931A JP2014147578A JP2014147578A JP2016024931A JP 2016024931 A JP2016024931 A JP 2016024931A JP 2014147578 A JP2014147578 A JP 2014147578A JP 2014147578 A JP2014147578 A JP 2014147578A JP 2016024931 A JP2016024931 A JP 2016024931A
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circuit
led array
voltage
led
temperature
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藤原　宗
So Fujiwara
宗 藤原
堅次 武渕
Kenji Takebuchi
堅次 武渕
祥正 稗田
Yoshimasa Hieda
祥正 稗田
洋明 山田
Hiroaki Yamada
洋明 山田
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Kyushu Institute of Technology NUC
New Japan Radio Co Ltd
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Kyushu Institute of Technology NUC
New Japan Radio Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide an LED driving circuit in which power loss can be reduced.SOLUTION: An LED array driving circuit 20 to which plural LEDs are connected in series, an LED driving circuit 40 for simultaneously executing lighting control driving on the respective LEDs of the LED array circuit 20 according to an input lighting control signal, a DC voltage source circuit 10 for applying an output voltage VOUT to the series circuit of the LED array circuit 20 and the driving circuit 40, and an output voltage control circuit 50 for controlling the output voltage of the DC voltage source circuit 10 are provided. A temperature sensor 30 for detecting the temperature of the LEDs of the LED array circuit 20 is provided, and the DC voltage control circuit 50 controls the output voltage VOUT of the DC voltage source circuit 10 according to the temperature detected by the temperature sensor 30.SELECTED DRAWING: Figure 1

Description

本発明は、ＬＥＤアレイ回路とＬＥＤ駆動回路の直列回路に供給する電圧を必要最小電圧に制御することで電力消費の最適制御を行うようにしたＬＥＤアレイ駆動回路に関する。   The present invention relates to an LED array drive circuit that performs optimal control of power consumption by controlling a voltage supplied to a series circuit of an LED array circuit and an LED drive circuit to a necessary minimum voltage.

ＬＥＤアレイ駆動回路として、従来から、直流電圧源回路１０Ａを用いた図７に示すような構成の回路と、直流電流源回路１０Ｂを用いた図８に示すような構成の回路（特許文献１）が提案されている。いずれの回路構成においても、ｎ個のＬＥＤの直列接続回路を複数並列接続したＬＥＤアレイ回路２０Ａ，２０Ｂの発する光の強さを制御するためには、そのＬＥＤアレイ回路２０Ａ，２０Ｂに供給する電流をＰＷＭ制御する必要がある。   Conventionally, as an LED array driving circuit, a circuit having a configuration as shown in FIG. 7 using a DC voltage source circuit 10A and a circuit having a configuration as shown in FIG. 8 using a DC current source circuit 10B (Patent Document 1). Has been proposed. In any circuit configuration, in order to control the intensity of light emitted from the LED array circuits 20A and 20B in which a plurality of n LED series-connected circuits are connected in parallel, the current supplied to the LED array circuits 20A and 20B Need to be PWM controlled.

図７に示すＬＥＤアレイ駆動回路は、ＬＥＤアレイ回路２０ＡとＬＥＤ駆動回路４０Ａを備える。ＬＥＤ駆動回路４０Ａは、ＮＰＮトランジスタＱ０と、そのトランジスタＱ０を制御するオペアンプＯＰ１と、電流検出用の抵抗Ｒ０を有する。ＬＥＤアレイ回路２０ＡとＬＥＤ駆動回路４０Ａの直列回路には、直流電圧源回路１０Ａの出力電圧ＶＯＵＴが印加される。ＬＥＤ駆動回路４０ＡのトランジスタＱ０はオペアンプＯＰ１によって制御される。このオペアンプＯＰ１は、非反転入力端子に電流を決める電圧ＶＲＥＦが印加され、反転入力端子に抵抗Ｒ０に発生する電圧が入力する。よって、トランジスタＱ０は、抵抗Ｒ０に発生する電圧が電圧ＶＲＥＦに一致する電圧となるように、オペアンプＯＰ１により制御されることで、ＬＥＤアレイ回路２０Ａには電圧ＶＲＥＦに相当する一定の電流が流れる。オペアンプＯＰ１を調光信号ＰＷＭ２によってオン／オフ制御することで、ＬＥＤアレイ回路２０Ａは各ＬＥＤが同時に点滅し、調光信号ＰＷＭ２のデューティ比に応じた明るさを実現できる。   The LED array drive circuit shown in FIG. 7 includes an LED array circuit 20A and an LED drive circuit 40A. The LED drive circuit 40A includes an NPN transistor Q0, an operational amplifier OP1 that controls the transistor Q0, and a current detection resistor R0. The output voltage VOUT of the DC voltage source circuit 10A is applied to the series circuit of the LED array circuit 20A and the LED drive circuit 40A. The transistor Q0 of the LED drive circuit 40A is controlled by the operational amplifier OP1. In the operational amplifier OP1, the voltage VREF that determines the current is applied to the non-inverting input terminal, and the voltage generated in the resistor R0 is input to the inverting input terminal. Therefore, the transistor Q0 is controlled by the operational amplifier OP1 so that the voltage generated in the resistor R0 matches the voltage VREF, so that a constant current corresponding to the voltage VREF flows through the LED array circuit 20A. By turning on / off the operational amplifier OP1 by the dimming signal PWM2, the LED array circuit 20A can simultaneously flash the respective LEDs, and can realize brightness according to the duty ratio of the dimming signal PWM2.

図８に示すＬＥＤアレイ駆動回路の直流電流源回路１０Ｂには、ＬＥＤアレイ回路２０Ｂの合計順方向電圧ｎ・Ｖｆよりも十分に高い出力電圧範囲をもつものが使用される。このように、ＬＥＤアレイ回路２０Ｂを駆動する構成において直流電流源回路１０Ｂを用いると、回路構成が簡単になる。   As the DC current source circuit 10B of the LED array driving circuit shown in FIG. 8, a circuit having an output voltage range sufficiently higher than the total forward voltage n · Vf of the LED array circuit 20B is used. Thus, when the DC current source circuit 10B is used in the configuration for driving the LED array circuit 20B, the circuit configuration is simplified.

特開２００７−２１４１１１号公報JP 2007-214111 A

しかしながら、図７に示す構成のＬＥＤアレイ駆動回路では、トランジスタＱ０を制御することでＬＥＤアレイ回路２０Ａに流れる電流が一定値に制御されるが、直流電圧源回路１０Ａの出力電圧ＶＯＵＴの制御は行われない。   However, in the LED array drive circuit having the configuration shown in FIG. 7, the current flowing through the LED array circuit 20A is controlled to a constant value by controlling the transistor Q0, but the output voltage VOUT of the DC voltage source circuit 10A is controlled. I will not.

このため、例えば、自己発熱によってＬＥＤアレイ回路２０Ａの各ＬＥＤの順方向電圧Ｖｆが低下した場合は、ＬＥＤアレイ回路２０Ａに印加するｎ・Ｖｆ電圧が低下する。よって、その低下した分だけ、ＬＥＤ駆動回路４０ＡのトランジスタＱ０のコレクタ・エミッタ間に印加する電圧Ｖｃｅが大きくなるため、そのトランジスタＱ０における電力損失が大きくなる。   For this reason, for example, when the forward voltage Vf of each LED of the LED array circuit 20A decreases due to self-heating, the n · Vf voltage applied to the LED array circuit 20A decreases. Therefore, the voltage Vce applied between the collector and the emitter of the transistor Q0 of the LED drive circuit 40A is increased by the reduced amount, so that the power loss in the transistor Q0 is increased.

また、図８に示したＬＥＤアレイ駆動回路では、直流電流源回路１０Ｂによる微小な電流量の制御が難しく、細かい調光制御を行うことが困難である。   Further, in the LED array driving circuit shown in FIG. 8, it is difficult to control a minute amount of current by the DC current source circuit 10B, and it is difficult to perform fine dimming control.

本発明の目的は、上記したＬＥＤ駆動回路における電力損失を少なくし、また細かい調光制御を可能にしたＬＥＤアレイ駆動回路を提供することである。   An object of the present invention is to provide an LED array driving circuit that reduces power loss in the LED driving circuit described above and enables fine dimming control.

上記目的を達成するために、請求項１にかかる発明のＬＥＤアレイ駆動回路は、複数のＬＥＤが直列接続されたＬＥＤアレイ回路と、該ＬＥＤアレイ回路の各ＬＥＤを入力する調光信号に応じて同時に調光駆動するＬＥＤ駆動回路と、出力電圧を前記ＬＥＤアレイ回路と前記ＬＥＤ駆動回路の直列回路に印加する直流電圧源回路と、該直流電圧源回路の前記出力電圧を制御する出力電圧制御回路とを有するＬＥＤアレイ駆動回路において、前記ＬＥＤアレイ回路の前記ＬＥＤの温度を検出する温度センサを備え、前記直流電圧制御回路は前記温度センサで検出された温度に応じて前記直流電圧源回路の出力電圧を制御することを特徴とする。   In order to achieve the above object, an LED array driving circuit according to a first aspect of the present invention includes an LED array circuit in which a plurality of LEDs are connected in series, and a dimming signal input to each LED of the LED array circuit. LED driving circuit for dimming driving simultaneously, DC voltage source circuit for applying an output voltage to a series circuit of the LED array circuit and the LED driving circuit, and an output voltage control circuit for controlling the output voltage of the DC voltage source circuit The LED array driving circuit includes: a temperature sensor that detects a temperature of the LED of the LED array circuit, wherein the DC voltage control circuit outputs an output of the DC voltage source circuit according to the temperature detected by the temperature sensor. The voltage is controlled.

請求項２にかかる発明は、請求項１に記載のＬＥＤアレイ駆動回路において、前記直流電圧制御回路は、前記温度センサの検知温度が異常温度となったとき、制御駆動回路を制御して、前記ＬＥＤ駆動回路を動作停止させることを特徴とする。   According to a second aspect of the present invention, in the LED array driving circuit according to the first aspect, the DC voltage control circuit controls the control driving circuit when the temperature detected by the temperature sensor becomes an abnormal temperature. The operation of the LED drive circuit is stopped.

請求項３にかかる発明は、請求項１又は２に記載のＬＥＤアレイ駆動回路において、前記直流電圧制御回路は、前記温度センサの検知温度が異常温度となったとき、前記直流電圧源回路を動作停止させることを特徴とする。   The invention according to claim 3 is the LED array drive circuit according to claim 1 or 2, wherein the DC voltage control circuit operates the DC voltage source circuit when the temperature detected by the temperature sensor becomes an abnormal temperature. It is characterized by being stopped.

請求項４にかかる発明は、請求項１、２又は３に記載のＬＥＤアレイ駆動回路において、前記直流電圧制御回路は、前記直流電圧源回路の出力電圧が異常電圧となったとき、前記直流電圧源回路を動作停止させることを特徴とする。   According to a fourth aspect of the present invention, in the LED array driving circuit according to the first, second, or third aspect, the direct current voltage control circuit is configured such that when the output voltage of the direct current voltage source circuit becomes an abnormal voltage, the direct current voltage control circuit The operation of the source circuit is stopped.

請求項５にかかる発明は、請求項１、２、３又は４に記載のＬＥＤアレイ駆動回路において、前記温度センサとして、前記ＬＥＤアレイ回路のＬＥＤと熱的に結合された熱電対、ダイオード、又はトランジスタを使用することを特徴とする。   The invention according to claim 5 is the LED array drive circuit according to claim 1, 2, 3 or 4, wherein the temperature sensor is a thermocouple, a diode, or a thermocouple thermally coupled to an LED of the LED array circuit. A transistor is used.

本発明によれば、ＬＥＤアレイ回路とＬＥＤ駆動回路の直列回路に印加される直流電圧源回路の出力電圧が、ＬＥＤアレイ回路の温度に応じて制御されるので、ＬＥＤ駆動回路における電力損失を最小値に制御することができる。また、ＬＥＤアレイに流れる電流をＬＥＤ駆動回路により調光制御できるので、細かい制御が可能となる。   According to the present invention, since the output voltage of the DC voltage source circuit applied to the series circuit of the LED array circuit and the LED drive circuit is controlled according to the temperature of the LED array circuit, the power loss in the LED drive circuit is minimized. The value can be controlled. In addition, since the current flowing through the LED array can be dimmed and controlled by the LED drive circuit, fine control is possible.

本発明の実施例のＬＥＤアレイ駆動回路のブロック図である。It is a block diagram of the LED array drive circuit of the Example of this invention. 図１のＬＥＤ駆動回路の直流電圧源回路の回路図である。FIG. 2 is a circuit diagram of a DC voltage source circuit of the LED drive circuit of FIG. 1. 図１のＬＥＤ駆動回路のＬＥＤアレイ回路の回路図である。It is a circuit diagram of the LED array circuit of the LED drive circuit of FIG. 図１のＬＥＤ駆動回路のＬＥＤ駆動回路の回路図である。It is a circuit diagram of the LED drive circuit of the LED drive circuit of FIG. 図１のＬＥＤ駆動回路の直流電圧制御回路の回路図である。FIG. 2 is a circuit diagram of a DC voltage control circuit of the LED drive circuit of FIG. 1. 図１のＬＥＤ駆動回路の駆動制御回路の回路図である。It is a circuit diagram of the drive control circuit of the LED drive circuit of FIG. 従来のＬＥＤアレイ駆動回路の回路図である。It is a circuit diagram of the conventional LED array drive circuit. 別の従来のＬＥＤアレイ駆動回路の回路図である。It is a circuit diagram of another conventional LED array drive circuit.

図１に本発明の１つの実施例のＬＥＤアレイ駆動回路を示す。１０は直流電圧源回路であり、電源端子７０に入力する電圧ＶＩＮを昇圧あるいは降圧処理して出力電圧ＶＯＵＴとして出力する。２０はＬＥＤアレイ回路であり、ｎ個のＬＥＤ２１が直列接続されたＬＥＤアレイを複数個並列接続して構成されている。３０は温度センサであり、ＬＥＤアレイ回路２０のＬＥＤの発熱温度を検出するよう、ＬＥＤアレイ回路２０の基板にＬＥＤと熱的結合状態で搭載されている。４０はＬＥＤ駆動回路であり、ＬＥＤアレイ回路２０のＬＥＤに流れる電流を一定値に制御し且つ入力する調光信号ＰＷＭ２に応じてその電流をオン／オフしてＬＥＤの調光駆動を行なう。５０は直流電圧源回路１０を制御する直流電圧制御回路であり、温度センサ３０で検出された温度信号ＶＴに応じて直流電圧源回路１０の出力電圧ＶＯＵＴを制御する。６０は駆動制御回路であり、調光制御端子８０から入力する調光信号ＰＷＭ１をそのまま調光信号ＰＷＭ２としてＬＥＤ駆動回路４０に伝達させるが、直流電圧制御回路５０から調光停止制御信号ＶＣが入力すると、その調光信号ＰＷＭ２を“Ｌ”に固定する。   FIG. 1 shows an LED array driving circuit according to one embodiment of the present invention. Reference numeral 10 denotes a DC voltage source circuit which boosts or steps down the voltage VIN input to the power supply terminal 70 and outputs it as an output voltage VOUT. Reference numeral 20 denotes an LED array circuit, which is configured by connecting a plurality of LED arrays in which n LEDs 21 are connected in series. Reference numeral 30 denotes a temperature sensor which is mounted on the substrate of the LED array circuit 20 in a thermally coupled state so as to detect the heat generation temperature of the LEDs of the LED array circuit 20. Reference numeral 40 denotes an LED drive circuit which controls the current flowing through the LEDs of the LED array circuit 20 to a constant value and turns the current on / off in accordance with the input dimming signal PWM2 to perform dimming driving of the LEDs. A DC voltage control circuit 50 controls the DC voltage source circuit 10 and controls the output voltage VOUT of the DC voltage source circuit 10 according to the temperature signal VT detected by the temperature sensor 30. A drive control circuit 60 transmits the dimming signal PWM1 input from the dimming control terminal 80 as it is to the LED drive circuit 40 as the dimming signal PWM2, but receives the dimming stop control signal VC from the DC voltage control circuit 50. Then, the dimming signal PWM2 is fixed to “L”.

ＬＥＤアレイ回路２０に印加する電圧ＶＡは、直列接続されているＬＥＤの数ｎとその順方向電圧Ｖｆの積の電圧ＶＡ（＝ｎ・Ｖｆ）によって決まり、その電圧ＶＡは温度が高くなるほど、低下する。このとき、直流電圧源回路１０から出力する電圧ＶＯＵＴが一定電圧の場合は、ＬＥＤ駆動回路４０に印加する電圧ＶＰは、ＶＰ＝ＶＯＵＴ−ＶＡとなる。よって、ＬＥＤアレイ回路２０の温度が高くなるほど、ＬＥＤ駆動回路４０に印加する電圧ＶＰは高くなり、駆動トランジスタのＶｃｅが増大して、その分だけ電力消費量が増大する。   The voltage VA applied to the LED array circuit 20 is determined by the voltage VA (= n · Vf) of the product of the number n of LEDs connected in series and the forward voltage Vf, and the voltage VA decreases as the temperature increases. To do. At this time, when the voltage VOUT output from the DC voltage source circuit 10 is a constant voltage, the voltage VP applied to the LED drive circuit 40 is VP = VOUT−VA. Therefore, the higher the temperature of the LED array circuit 20, the higher the voltage VP applied to the LED drive circuit 40, and the Vce of the drive transistor increases, and the power consumption increases accordingly.

そこで、本実施例では、ＬＥＤアレイ回路２０のＬＥＤの発熱温度を温度センサ３０で検出し温度信号ＶＴとして直流電圧制御回路５０に取り込む。そして、温度センサ３０で検出される温度が高くなるほど、直流電圧制御回路５０から直流電圧源回路１０に出力する制御信号ＰＷＭ０のデューティ比を低下させ、直流電圧源回路１０の出力電圧ＶＯＵＴを低下させて、ＬＥＤ駆動回路４０に印加される電圧ＶＰが必要以上に高くならないようにする。これにより、ＬＥＤ駆動回路４０に印加する電圧ＶＰは温度変化にかかわらずほぼ一定に保持され、ＬＥＤ駆動回路４０における無駄な電力消費を回避することができる。   Therefore, in the present embodiment, the heat generation temperature of the LEDs of the LED array circuit 20 is detected by the temperature sensor 30 and is taken into the DC voltage control circuit 50 as the temperature signal VT. As the temperature detected by the temperature sensor 30 increases, the duty ratio of the control signal PWM0 output from the DC voltage control circuit 50 to the DC voltage source circuit 10 is decreased, and the output voltage VOUT of the DC voltage source circuit 10 is decreased. Thus, the voltage VP applied to the LED drive circuit 40 is prevented from becoming higher than necessary. Thereby, the voltage VP applied to the LED drive circuit 40 is kept substantially constant regardless of the temperature change, and wasteful power consumption in the LED drive circuit 40 can be avoided.

また、温度センサ３０が検出した温度が異常に高いときは、直流電圧制御回路５０から調光停止制御信号ＶＣが出力して駆動制御回路６０を制御し、調光制御端子８０に入力している調光信号ＰＷＭ１を遮断して、駆動制御回路６０から出力する調光信号ＰＷＭ２を“Ｌ”に設定し、ＬＥＤ駆動回路４０を動作停止させ、ＬＥＤアレイ回路２０に電流を流さないようにする。   When the temperature detected by the temperature sensor 30 is abnormally high, a dimming stop control signal VC is output from the DC voltage control circuit 50 to control the drive control circuit 60 and input to the dimming control terminal 80. The dimming signal PWM1 is cut off, the dimming signal PWM2 output from the drive control circuit 60 is set to “L”, the operation of the LED drive circuit 40 is stopped, and no current flows through the LED array circuit 20.

また、直流電圧源回路１０の出力電圧ＶＯＵＴが異常に高い電圧になったときも、直流電圧制御回路５０がその出力電圧監視信号ＶＦを取り込んで、駆動制御回路６０に対して調光停止制御信号ＶＣを出力し、上記と同様に、ＬＥＤ駆動回路４０を動作停止させ、ＬＥＤアレイ回路２０に電流を流さないようにする。   Further, also when the output voltage VOUT of the DC voltage source circuit 10 becomes an abnormally high voltage, the DC voltage control circuit 50 takes in the output voltage monitoring signal VF and sends a dimming stop control signal to the drive control circuit 60. VC is output, and the LED drive circuit 40 is stopped in the same manner as described above, so that no current flows through the LED array circuit 20.

このとき、必要に応じて、直流電圧制御回路５０から直流電圧源回路１０に出力する制御信号ＰＷＭ０を停止して、直流電圧源回路１０の出力電圧ＶＯＵＴを停止させることもできる。   At this time, if necessary, the control signal PWM0 output from the DC voltage control circuit 50 to the DC voltage source circuit 10 can be stopped to stop the output voltage VOUT of the DC voltage source circuit 10.

図２に直流電圧源回路１０の回路構成を示す。ＭＰ１はＰＭＯＳのスイッチングトランジスタであり、直流電圧制御回路５０から入力する出力電圧制御用のＰＷＭ信号ＰＷＭ０によって入力電圧ＶＩＮをスイッチングする。Ｌ１はインダクタであり、トランジスタＭＰ１がオンしたときに流れる電流でエネルギーを蓄積する。Ｄ１はダイオードであり、トランジスタＭＰ１がオフしたときにインダクタＬ１から流れる電流を整流する。Ｃ１は出力コンデンサであり、スイッチングによる電圧を平滑化して出力電圧ＶＯＵＴとして出力する。Ｒ１，Ｒ２は出力電圧ＶＯＵＴを分圧する抵抗であり、分圧された電圧は出力電圧監視信号ＶＦとして直流電圧制御回路５０に入力する。   FIG. 2 shows a circuit configuration of the DC voltage source circuit 10. MP1 is a PMOS switching transistor, and switches the input voltage VIN by a PWM signal PWM0 for output voltage control input from the DC voltage control circuit 50. L1 is an inductor that accumulates energy with a current that flows when the transistor MP1 is turned on. D1 is a diode that rectifies the current flowing from the inductor L1 when the transistor MP1 is turned off. C1 is an output capacitor, which smoothes the voltage due to switching and outputs it as an output voltage VOUT. R1 and R2 are resistors for dividing the output voltage VOUT, and the divided voltage is input to the DC voltage control circuit 50 as the output voltage monitoring signal VF.

図３にＬＥＤアレイ回路２０と温度センサ３０の回路構成を示す。ＬＥＤアレイ回路２０は、ｎ個のＬＥＤ２１が直列接続されたＬＥＤアレイを複数個並列接続して構成されている。温度センサ３０は、例えばバイアス電圧ＶＣＣが印加された熱電対で構成されている。   FIG. 3 shows a circuit configuration of the LED array circuit 20 and the temperature sensor 30. The LED array circuit 20 is configured by connecting in parallel a plurality of LED arrays in which n LEDs 21 are connected in series. The temperature sensor 30 is composed of a thermocouple to which a bias voltage VCC is applied, for example.

図４にＬＥＤ駆動回路４０の回路構成を示す。このＬＥＤアレイ駆動回路４０は、ＮＰＮの駆動トランジスタＱ０と、その駆動トランジスタＱ０を制御するオペアンプＯＰ１と、電流検出用の抵抗Ｒ０を有する。オペアンプＯＰ１は、非反転入力端子に電流を決める一定の電圧ＶＲＥＦが印加され、反転入力端子に抵抗Ｒ０に発生する電圧が入力する。よって、トランジスタＱ０は、抵抗Ｒ０に発生する電圧が電圧ＶＲＥＦに一致する電圧となるように、オペアンプＯＰ１により制御されることで、トランジスタＱ０には電圧ＶＲＥＦに相当する一定電流が流れる。オペアンプＯＰ１は調光信号ＰＷＭ２によってオン／オフ制御されることで、トランジスタＱ０のコレクタ電流が流れるＬＥＤアレイ回路２０の各ＬＥＤ２１が同時に点滅し、調光信号ＰＷＭ２のデューティ比に応じた調光制御が行われる。   FIG. 4 shows a circuit configuration of the LED drive circuit 40. The LED array drive circuit 40 includes an NPN drive transistor Q0, an operational amplifier OP1 that controls the drive transistor Q0, and a current detection resistor R0. In the operational amplifier OP1, a constant voltage VREF that determines a current is applied to the non-inverting input terminal, and a voltage generated in the resistor R0 is input to the inverting input terminal. Therefore, the transistor Q0 is controlled by the operational amplifier OP1 so that the voltage generated in the resistor R0 matches the voltage VREF, so that a constant current corresponding to the voltage VREF flows through the transistor Q0. The operational amplifier OP1 is turned on / off by the dimming signal PWM2, so that the LEDs 21 of the LED array circuit 20 through which the collector current of the transistor Q0 flows simultaneously flash, and dimming control according to the duty ratio of the dimming signal PWM2 is performed. Done.

図５に直流電圧制御回路５０の回路構成を示す。４１はディジタル演算回路（ＣＰＵ）であり、処理プログラムやデータの格納用のメモリ４２を有する。そして、Ａ/Ｄ変換器４３によって直流電圧源回路１０から出力する出力電圧監視信号ＶＦをディジタル信号に変換して取り込み、Ａ/Ｄ変換器４４によって温度センサ３０から出力するＬＥＤアレイ回路２０の温度信号ＶＴをディジタル信号に変換して取り込んで、内部処理を行う。そして、内部処理により得た出力電圧制御用信号ＰＷＭ０をＤ/Ａ変換器４５によってアナログ信号に変換して出力し、内部処理により得た調光停止制御信号ＶＣをＤ/Ａ変換器４６によってアナログ信号に変換して出力する。温度信号ＶＴと出力電圧制御用信号ＰＷＭ０との関係を示すテーブルがメモリ４２に格納され、そのテーブルから、温度信号ＶＴに応じて出力電圧制御信号ＰＷＭ０が読み出される。すなわち、温度信号ＶＴが低い温度を示すほど読み出される出力電圧制御信号ＰＷＭ０のデューティ比は低下する。これにより、温度信号ＶＴが低い温度を示すほど直流電圧源回路１０の出力電圧ＶＯＵＴが低下する。また、調光停止制御信号ＶＣは、温度信号ＶＴが予め設定した異常に高い温度を示すとき、あるいは出力電圧監視信号ＶＦが予め設定した異常に高い出力電圧ＶＯＵＴを示すときに、“Ｌ”の信号として出力する。   FIG. 5 shows a circuit configuration of the DC voltage control circuit 50. A digital arithmetic circuit (CPU) 41 has a memory 42 for storing processing programs and data. Then, the A / D converter 43 converts the output voltage monitoring signal VF output from the DC voltage source circuit 10 into a digital signal and takes it in, and the A / D converter 44 outputs the temperature of the LED array circuit 20 from the temperature sensor 30. The signal VT is converted into a digital signal and taken in for internal processing. The output voltage control signal PWM0 obtained by the internal processing is converted into an analog signal by the D / A converter 45 and output, and the dimming stop control signal VC obtained by the internal processing is converted by the D / A converter 46 to the analog signal. Convert to signal and output. A table indicating the relationship between the temperature signal VT and the output voltage control signal PWM0 is stored in the memory 42, and the output voltage control signal PWM0 is read from the table in accordance with the temperature signal VT. That is, the duty ratio of the output voltage control signal PWM0 that is read decreases as the temperature signal VT indicates a lower temperature. Thereby, the output voltage VOUT of the DC voltage source circuit 10 decreases as the temperature signal VT indicates a lower temperature. The dimming stop control signal VC is “L” when the temperature signal VT indicates a preset abnormally high temperature or when the output voltage monitoring signal VF indicates a preset abnormally high output voltage VOUT. Output as a signal.

図６に駆動制御回路６０の回路構成を示す。この駆動制御回路６０はアンドゲートＡＮＤ１により構成され、調光停止制御信号ＶＣが“Ｌ”の信号となることにより、入力する調光信号ＰＷＭ１に対して出力する調光信号ＰＷＭ２を“Ｌ”に固定する。これにより、図４で説明したＬＥＤ駆動回路４０のオペアンプＯＰ１がディセーブルに制御され、その出力電圧が“Ｌ”になることで、トランジスタＱ０がオフに制御され、ＬＥＤアレイ回路２０に流れる電流が零に制御される。   FIG. 6 shows a circuit configuration of the drive control circuit 60. The drive control circuit 60 is configured by an AND gate AND1. When the dimming stop control signal VC becomes “L”, the dimming signal PWM2 output to the input dimming signal PWM1 is set to “L”. Fix it. As a result, the operational amplifier OP1 of the LED drive circuit 40 described in FIG. 4 is controlled to be disabled, and the output voltage thereof becomes “L”, whereby the transistor Q0 is controlled to be off, and the current flowing through the LED array circuit 20 is reduced. Controlled to zero.

なお、以上では温度センサ３０として熱電対を例にして説明したが、ダイオードを使用することもできる。この場合は、所定のバイアスをかけたダイオードをＬＥＤアレイ回路２０のＬＥＤに熱的に結合しておき、その順方向電圧を温度信号ＶＴとすればよい。また、トランジスタを使用することもできる。この場合は、所定のバイアスをかけたトランジスタをＬＥＤアレイ回路２０のＬＥＤに熱的に結合しておき、そのエミッタ電流あるいはコレクタ電流を電圧変換して温度信号ＶＴとして使用すればよい。また、調光用としてＬＥＤアレイ回路２０に装備されているＬＥＤそのものを利用して、その順方向電圧Ｖｆを温度信号として使用するこもできる。この場合は、ＬＥＤアレイ回路２０の入力端子と出力端子との間の電圧ｎ・Ｖｆを温度信号ＶＴとして採取すれば、個々のＬＥＤの順方向電圧Ｖｆのばらつきの影響を少なくすることができる。また、ＬＥＤ駆動回路４０のトランジスタＱ０は、バイポーラトランジスタに限られるものではなく、ＦＥＴトランジスタを使用することもできる。   Although the thermocouple has been described as an example of the temperature sensor 30 in the above, a diode can also be used. In this case, a diode to which a predetermined bias is applied may be thermally coupled to the LED of the LED array circuit 20, and the forward voltage thereof may be used as the temperature signal VT. A transistor can also be used. In this case, a transistor to which a predetermined bias is applied may be thermally coupled to the LED of the LED array circuit 20, and the emitter current or collector current may be converted into voltage and used as the temperature signal VT. Further, by using the LED itself provided in the LED array circuit 20 for dimming, the forward voltage Vf can be used as a temperature signal. In this case, if the voltage n · Vf between the input terminal and the output terminal of the LED array circuit 20 is taken as the temperature signal VT, the influence of variations in the forward voltage Vf of each LED can be reduced. Further, the transistor Q0 of the LED drive circuit 40 is not limited to a bipolar transistor, and an FET transistor can also be used.

１０，１０Ａ：直流電圧源回路、１０Ｂ：直流電流源回路、２０，２０Ａ，２０Ｂ：ＬＥＤアレイ回路、３０：温度センサ、４０，４０Ａ：ＬＥＤ駆動回路、５０：直流電圧制御回路、６０：駆動制御回路、７０：電源端子、８０：調光制御端子   10, 10A: DC voltage source circuit, 10B: DC current source circuit, 20, 20A, 20B: LED array circuit, 30: Temperature sensor, 40, 40A: LED drive circuit, 50: DC voltage control circuit, 60: Drive control Circuit, 70: power supply terminal, 80: dimming control terminal

Claims (5)

複数のＬＥＤが直列接続されたＬＥＤアレイ回路と、該ＬＥＤアレイ回路の各ＬＥＤを入力する調光信号に応じて同時に調光駆動するＬＥＤ駆動回路と、出力電圧を前記ＬＥＤアレイ回路と前記ＬＥＤ駆動回路の直列回路に印加する直流電圧源回路と、該直流電圧源回路の前記出力電圧を制御する出力電圧制御回路とを有するＬＥＤアレイ駆動回路において、
前記ＬＥＤアレイ回路の前記ＬＥＤの温度を検出する温度センサを備え、前記直流電圧制御回路は前記温度センサで検出された温度に応じて前記直流電圧源回路の出力電圧を制御することを特徴とするＬＥＤアレイ駆動回路。 An LED array circuit in which a plurality of LEDs are connected in series, an LED drive circuit that simultaneously performs dimming driving according to a dimming signal that inputs each LED of the LED array circuit, and an output voltage that is the LED array circuit and the LED driving In an LED array driving circuit having a DC voltage source circuit to be applied to a series circuit of circuits, and an output voltage control circuit for controlling the output voltage of the DC voltage source circuit,
A temperature sensor for detecting a temperature of the LED of the LED array circuit is provided, and the DC voltage control circuit controls an output voltage of the DC voltage source circuit according to a temperature detected by the temperature sensor. LED array drive circuit. 請求項１に記載のＬＥＤアレイ駆動回路において、
前記直流電圧制御回路は、前記温度センサの検知温度が異常温度となったとき、制御駆動回路を制御して、前記ＬＥＤ駆動回路を動作停止させることを特徴とするＬＥＤアレイ駆動回路。 The LED array driving circuit according to claim 1,
The direct current voltage control circuit controls the control drive circuit to stop the operation of the LED drive circuit when the temperature detected by the temperature sensor becomes an abnormal temperature. 請求項１又は２に記載のＬＥＤアレイ駆動回路において、
前記直流電圧制御回路は、前記温度センサの検知温度が異常温度となったとき、前記直流電圧源回路を動作停止させることを特徴とするＬＥＤアレイ駆動回路。 The LED array driving circuit according to claim 1 or 2,
The LED array driving circuit, wherein the DC voltage control circuit stops the operation of the DC voltage source circuit when the temperature detected by the temperature sensor becomes an abnormal temperature. 請求項１、２又は３に記載のＬＥＤアレイ駆動回路において、
前記直流電圧制御回路は、前記直流電圧源回路の出力電圧が異常電圧となったとき、前記直流電圧源回路を動作停止させることを特徴とするＬＥＤアレイ駆動回路。 In the LED array drive circuit according to claim 1, 2, or 3,
The LED array drive circuit, wherein the DC voltage control circuit stops the operation of the DC voltage source circuit when the output voltage of the DC voltage source circuit becomes an abnormal voltage. 請求項１、２、３又は４に記載のＬＥＤアレイ駆動回路において、
前記温度センサとして、前記ＬＥＤアレイ回路のＬＥＤと熱的に結合された熱電対、ダイオード、又はトランジスタを使用することを特徴とするＬＥＤアレイ駆動回路。

In the LED array drive circuit according to claim 1, 2, 3, or 4,
A thermocouple, a diode, or a transistor that is thermally coupled to the LEDs of the LED array circuit is used as the temperature sensor.

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JP2008186668A (en) * 2007-01-29 2008-08-14 Sharp Corp Led drive circuit and video image display device using it
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