JP2006222376A - Power supply device and illuminator - Google Patents

Power supply device and illuminator Download PDF

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JP2006222376A
JP2006222376A JP2005036271A JP2005036271A JP2006222376A JP 2006222376 A JP2006222376 A JP 2006222376A JP 2005036271 A JP2005036271 A JP 2005036271A JP 2005036271 A JP2005036271 A JP 2005036271A JP 2006222376 A JP2006222376 A JP 2006222376A
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voltage
current
led
power supply
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JP4199201B2 (en
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Masahiro Ogawa
雅弘 小川
Takehiko Saito
武彦 斉藤
Yasuo Kawano
安夫 川野
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KYOSHIN DENKI SEISAKUSHO KK
Seiwa Electric Mfg Co Ltd
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KYOSHIN DENKI SEISAKUSHO KK
Seiwa Electric Mfg Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device in which an increase in heat generation and lowering in efficiency can be prevented by suppressing a variation in the brightness of an LED regardless of the number of LEDs connected in series, and to provide an illuminator equipped with that power supply device. <P>SOLUTION: A current flowing through a plurality of LEDs 9, 9, ... is detected by a resistor 61 and converted into a voltage before being outputted to an operational amplifier 71. The operational amplifier 71 outputs a voltage Vo corresponding to the inputted voltage and a current Io outputted from the operational amplifier 71 depending on the voltage Vo is compared with a set current Ir flowing through resistors 74, 75. When the current Io exceeds the set current Ir, a surplus current Ie (Io-Ir) is fed through the series circuit of a resistor 77, a photodiode 76b and a shunt regulator 78, and a PWM control section 51 stops a drive signal outputted to the gate of an FET 53 and lowers the output voltage from a converter circuit 5, thus decreasing the current If. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、ＬＥＤに電流を供給する電源装置及び該電源装置を備える照明装置に関する。   The present invention relates to a power supply device that supplies current to an LED and a lighting device including the power supply device.

従来から光源として用いられてきた蛍光灯に比べて、省電力又は長寿命であるという理由で、ＬＥＤ（Light Emitting Diode）が光源として注目を浴びており、数十ｍＡから数百ｍＡ程度の比較的大きな電流を流すことができるＬＥＤが、屋内用の照明機器のみならず、道路用照明機器、産業用照明機器などに幅広く使用されるようになった。   Compared to fluorescent lamps that have been used as light sources, LEDs (Light Emitting Diodes) are attracting attention as light sources because of their low power consumption and long life. Comparisons of tens to hundreds of mA LEDs capable of flowing a large current have been widely used not only for indoor lighting equipment but also for road lighting equipment, industrial lighting equipment, and the like.

このようなＬＥＤを照明機器用の光源として用いる場合、照明機器からの発光量を確保するために、複数のＬＥＤを集合体として接続して機器内に配置し（例えば、複数のＬＥＤを直列に接続し）、集合体としてのＬＥＤに定電圧電源を接続して、一定の電圧をＬＥＤに印加するとともに、ＬＥＤに流れる電流を所定の値にするために、ＬＥＤに直列に制限抵抗を接続して電流を制限する電源装置が用いられている。   When such an LED is used as a light source for a lighting device, a plurality of LEDs are connected as an aggregate and arranged in the device in order to ensure the amount of light emitted from the lighting device (for example, a plurality of LEDs are connected in series). Connect a constant voltage power supply to the LED as an assembly, apply a constant voltage to the LED, and connect a limiting resistor in series with the LED to set the current flowing through the LED to a predetermined value. Therefore, a power supply device that limits current is used.

図４は従来のＬＥＤ用の電源装置の構成を示すブロック図である。図において、１は電源装置に交流電圧を入力するための商用電源である。フィルタ回路２は、商用電源１から流入するノイズを除去する。整流回路３は、入力された交流電圧を全波整流する。コンデンサ４は、整流回路３で全波整流された電圧波形を平滑し、ほぼ一定な直流電圧をコンバータ回路１０へ出力する。コンバータ回路１０は、定電圧制御部を内蔵し、所定の定電圧を出力する。コンバータ回路１０の出力側には、電流制限用の抵抗２０を介して、直列接続されたＬＥＤ９、９、…を接続してある。   FIG. 4 is a block diagram showing the configuration of a conventional LED power supply device. In the figure, reference numeral 1 denotes a commercial power source for inputting an AC voltage to the power supply device. The filter circuit 2 removes noise flowing from the commercial power source 1. The rectifier circuit 3 performs full-wave rectification on the input AC voltage. Capacitor 4 smoothes the voltage waveform that has been full-wave rectified by rectifier circuit 3, and outputs a substantially constant DC voltage to converter circuit 10. The converter circuit 10 includes a constant voltage control unit and outputs a predetermined constant voltage. The LEDs 9, 9,... Connected in series are connected to the output side of the converter circuit 10 through a current limiting resistor 20.

これにより、各ＬＥＤには、コンバータ回路１０の出力電圧から、各ＬＥＤの順方向電圧降下分の電圧を差し引いた電圧を、制限抵抗値で割った値の電流が流れ、各ＬＥＤは所定の明るさで点灯する。   As a result, a current obtained by dividing a voltage obtained by subtracting a voltage corresponding to a forward voltage drop of each LED from the output voltage of the converter circuit 10 by each LED flows through each LED, and each LED has a predetermined brightness. It lights up.

しかしながら、従来の電源装置にあっては、コンバータ回路１０の出力電圧は、常に一定となるように制御される。一方、ＬＥＤの順方向電圧は、ＬＥＤの点灯経過時間、周囲温度などにより変化する。このため、例えば、ＬＥＤの周囲温度が上昇した場合には、直列接続されたＬＥＤ夫々の順方向電圧の低下が重畳されるため、制限抵抗に印加される電圧が上昇し、ＬＥＤに流れる電流が増加する。このため、周囲温度が変化した場合に、ＬＥＤの明るさが変化するとともに、制限抵抗が消費する電力が増加して、電源装置の発熱が大きくなり、また、電源装置の効率が低下するという問題があった。また、かかる問題は、直列接続されるＬＥＤの数が増えるに応じて顕著になる。   However, in the conventional power supply apparatus, the output voltage of the converter circuit 10 is controlled so as to be always constant. On the other hand, the forward voltage of the LED varies depending on the elapsed lighting time of the LED, the ambient temperature, and the like. For this reason, for example, when the ambient temperature of the LED rises, a drop in the forward voltage of each of the LEDs connected in series is superimposed, so the voltage applied to the limiting resistor rises and the current flowing through the LED To increase. For this reason, when the ambient temperature changes, the brightness of the LED changes, the power consumed by the limiting resistor increases, the heat generated by the power supply increases, and the efficiency of the power supply decreases. was there. Such a problem becomes more prominent as the number of LEDs connected in series increases.

本発明は斯かる事情に鑑みてなされたものであり、ＬＥＤに供給される電流を検出し、検出した電流と閾値電流とを比較する比較部を備えることにより、比較した結果に基づいて、出力電圧を変化させて、ＬＥＤに供給される電流を略一定にすることにより、直列接続されるＬＥＤの数に拘わらず、点灯時間又は周囲温度などが変化した場合であっても、ＬＥＤの明るさのばらつきを抑制し、発熱量の増加及び効率の低下を防止することができる電源装置及び該電源装置を備える照明装置を提供することを目的とする。   The present invention has been made in view of such circumstances, and by providing a comparison unit that detects a current supplied to the LED and compares the detected current with a threshold current, the output is based on the comparison result. By changing the voltage to make the current supplied to the LED substantially constant, the brightness of the LED even when the lighting time or ambient temperature changes, regardless of the number of LEDs connected in series. It is an object of the present invention to provide a power supply device that can suppress variations in the amount of heat and prevent an increase in heat generation and a decrease in efficiency, and a lighting device including the power supply device.

本発明の他の目的は、出力電圧を検出する電圧検出部を備えることにより、ＬＥＤが接続されていない無負荷の状態において、出力電圧が異常に上昇することを防止することができる電源装置及び該電源装置を備える照明装置を提供することにある。   Another object of the present invention is to provide a power supply apparatus capable of preventing an output voltage from rising abnormally in a no-load state in which an LED is not connected by providing a voltage detection unit that detects an output voltage. It is providing the illuminating device provided with this power supply device.

第１発明に係る電源装置は、ＬＥＤに電流を供給する電源装置において、出力電圧可変の電圧供給部と、前記ＬＥＤに供給する電流を検出する電流検出部と、閾値電流を設定する閾値設定部と、前記電流検出部が検出した電流と前記閾値電流とを比較する比較部とを備え、該比較部が比較した結果に基づいて、前記電圧供給部の出力電圧を変更して前記ＬＥＤに流れる電流を略一定にするようにしてあることを特徴とする。   According to a first aspect of the present invention, there is provided a power supply apparatus for supplying current to an LED, wherein the output voltage variable voltage supply section, a current detection section for detecting current supplied to the LED, and a threshold setting section for setting a threshold current And a comparison unit that compares the current detected by the current detection unit with the threshold current, and changes the output voltage of the voltage supply unit based on the result of comparison by the comparison unit and flows to the LED. The current is made substantially constant.

第２発明に係る電源装置は、第１発明において、前記電流検出部は、前記ＬＥＤに直列に接続される第１の抵抗素子を有し、前記閾値設定部は、カソード端子、アノード端子、及び基準電圧端子を有する基準電圧設定素子の基準電圧端子に、第２の抵抗素子及び第３の抵抗素子夫々の一端を接続してあり、前記比較部は、前記第２の抵抗素子及び第３の抵抗素子夫々の他端間に接続され、前記基準電圧設定素子と、該基準電圧設定素子のカソード端子又はアノード端子に一端を接続した第４の抵抗素子との直列回路を有しており、前記ＬＥＤに供給される電流を前記第１の抵抗素子で変換して得られる電圧を前記第２の抵抗素子の他端へ出力するようにしてあり、前記直列回路を流れる電流に基づいて、前記電圧供給部の出力電圧を変更するようにしてあることを特徴とする。   A power supply device according to a second invention is the power supply device according to the first invention, wherein the current detection unit includes a first resistance element connected in series to the LED, and the threshold setting unit includes a cathode terminal, an anode terminal, and One end of each of the second resistance element and the third resistance element is connected to a reference voltage terminal of a reference voltage setting element having a reference voltage terminal, and the comparison unit includes the second resistance element and the third resistance element. Connected between the other ends of each of the resistance elements, and having a series circuit of the reference voltage setting element and a fourth resistance element having one end connected to a cathode terminal or an anode terminal of the reference voltage setting element, A voltage obtained by converting the current supplied to the LED with the first resistance element is output to the other end of the second resistance element, and the voltage is based on the current flowing through the series circuit. Changing the output voltage of the supply unit Unishi wherein the are.

第３発明に係る電源装置は、第１発明又は第２発明において、前記出力電圧を検出する電圧検出部を備え、該電圧検出部が検出した電圧が、所定の閾値電圧を超えた場合に、前記電圧供給部の出力電圧を下げるようにしてあることを特徴とする。   A power supply device according to a third aspect of the invention comprises the voltage detection unit for detecting the output voltage in the first or second aspect, and when the voltage detected by the voltage detection unit exceeds a predetermined threshold voltage, The output voltage of the voltage supply unit is lowered.

第４発明に係る照明装置は、ＬＥＤと、該ＬＥＤに電流を供給する第１発明乃至第３発明のいずれかに記載の電源装置とを備えることを特徴とする。   A lighting device according to a fourth aspect of the invention includes an LED and the power supply device according to any one of the first to third aspects of the invention that supplies current to the LED.

第１発明及び第４発明にあっては、電流検出部は、電圧供給部が供給した電圧によりＬＥＤに供給する電流を検出する。比較部は、前記電流検出部が検出した電流と、閾値設定部が設定した閾値電流とを比較する。前記比較部が比較した結果、検出した電流が前記閾値電流より大きい場合には、ＬＥＤに供給する電流を小さくするように前記電圧供給部の出力電圧を下げる。一方、検出した電流が前記閾値電流より小さい場合には、ＬＥＤに供給する電流を大きくするように前記電圧供給部の出力電圧を上げる。   In the first invention and the fourth invention, the current detection unit detects the current supplied to the LED by the voltage supplied by the voltage supply unit. The comparison unit compares the current detected by the current detection unit with the threshold current set by the threshold setting unit. If the detected current is larger than the threshold current as a result of the comparison by the comparison unit, the output voltage of the voltage supply unit is lowered so as to reduce the current supplied to the LED. On the other hand, when the detected current is smaller than the threshold current, the output voltage of the voltage supply unit is increased so as to increase the current supplied to the LED.

第２発明にあっては、ＬＥＤに供給する電流を第１の抵抗素子で変換して得られた電圧（例えば、増幅された電圧）を第２の抵抗素子の他端へ出力する。前記第２の抵抗素子の一端は、第３の抵抗素子の一端に接続してあるとともに、基準電圧設定素子の基準電圧端子に接続してあるため、前記第２の抵抗素子及び第３の抵抗素子に流れる電流は、前記基準電圧設定素子の基準電圧を第３の抵抗素子の抵抗値で割った値（ＬＥＤに流れる電流の目標値に対応する閾値電流）に設定される。また、前記第２の抵抗素子及び第３の抵抗素子夫々の他端間には、前記基準電圧設定素子と、該基準電圧設定素子のアノード端子又はカソード端子に一端を接続した第４の抵抗素子との直列回路を接続してある。   In the second invention, a voltage (for example, an amplified voltage) obtained by converting the current supplied to the LED with the first resistance element is output to the other end of the second resistance element. Since one end of the second resistance element is connected to one end of the third resistance element and to the reference voltage terminal of the reference voltage setting element, the second resistance element and the third resistance The current flowing through the element is set to a value obtained by dividing the reference voltage of the reference voltage setting element by the resistance value of the third resistance element (threshold current corresponding to the target value of the current flowing through the LED). Between the other ends of the second resistor element and the third resistor element, the reference voltage setting element and a fourth resistor element having one end connected to the anode terminal or the cathode terminal of the reference voltage setting element And connected in series.

ＬＥＤに供給する電流が増加した場合、前記増幅された電圧は大きくなり、前記第２の抵抗素子の他端における電圧が上昇する。前記第２の抵抗素子及び第３の抵抗素子には閾値電流以上の電流が流れないため、前記基準電圧設定素子と第４の抵抗素子との直列回路に、前記閾値電流を超えた電流が流れる。前記直列回路に流れる電流により、前記電圧供給部の出力電圧を下げ、ＬＥＤに供給する電流を小さくする。   When the current supplied to the LED increases, the amplified voltage increases and the voltage at the other end of the second resistance element increases. Since the current exceeding the threshold current does not flow through the second resistance element and the third resistance element, a current exceeding the threshold current flows through a series circuit of the reference voltage setting element and the fourth resistance element. . Due to the current flowing through the series circuit, the output voltage of the voltage supply unit is lowered to reduce the current supplied to the LED.

一方、ＬＥＤに供給する電流が減少した場合、前記増幅された電圧は小さくなり、前記第２の抵抗素子の他端における電圧が低下する。前記電圧による電流が前記閾値電流を下回った場合、前記基準電圧設定素子と第４の抵抗素子との直列回路には電流が流れない。前記直列回路に電流が流れないことにより、前記電圧供給部の出力電圧を上げ、ＬＥＤに供給する電流を大きくする。これにより、ＬＥＤに供給する電流を、目標値にほぼ等しい値にする。   On the other hand, when the current supplied to the LED decreases, the amplified voltage decreases and the voltage at the other end of the second resistance element decreases. When the current due to the voltage falls below the threshold current, no current flows through the series circuit of the reference voltage setting element and the fourth resistance element. Since no current flows through the series circuit, the output voltage of the voltage supply unit is increased, and the current supplied to the LED is increased. Thereby, the current supplied to the LED is set to a value substantially equal to the target value.

第３発明にあっては、電圧検出部が検出した出力電圧が、所定の閾値電圧を越えた場合、電圧供給部の出力電圧を所定の閾値電圧まで下げる。   In the third aspect of the invention, when the output voltage detected by the voltage detector exceeds a predetermined threshold voltage, the output voltage of the voltage supply unit is lowered to the predetermined threshold voltage.

第１発明及び第４発明にあっては、ＬＥＤに供給する電流を検出し、検出した電流と、閾値設定部で設定された閾値電流とを比較する比較部を備え、比較した結果に基づいて、電圧供給部の出力電圧を変更するようにしてあることにより、直列接続したＬＥＤの数に拘わらず、常に略一定の電流をＬＥＤに供給することができるため、時間変化、温度変化などに基づいて生じるＬＥＤの明るさ変動を抑制することができる。また、ＬＥＤに短絡破損が生じて負荷が大きく変動した場合であっても、常に略一定の電流をＬＥＤに供給することができ、ＬＥＤに過剰電流が流れることを防止でき、信頼性が向上する。また、制限抵抗を用いる必要がないため、制限抵抗で生じた発熱、電力消費を無くすことができ、無駄な消費電力を低減して効率を上げることができる。   In the 1st invention and the 4th invention, it has the comparison part which detects the electric current supplied to LED, and compares the detected electric current with the threshold current set by the threshold setting part, and based on the comparison result By changing the output voltage of the voltage supply unit, it is possible to always supply a substantially constant current to the LED regardless of the number of LEDs connected in series. LED brightness fluctuations that occur can be suppressed. Further, even when a short circuit breakage occurs in the LED and the load greatly fluctuates, it is possible to always supply a substantially constant current to the LED, prevent an excessive current from flowing through the LED, and improve reliability. . Further, since it is not necessary to use a limiting resistor, heat generation and power consumption caused by the limiting resistor can be eliminated, and wasteful power consumption can be reduced to increase efficiency.

第２発明にあっては、第２の抵抗素子の一端と他端を接地した第３の抵抗素子の一端とを接続し、前記一端に基準電圧設定素子の基準電圧端子を接続した閾値設定部と、前記基準電圧設定素子と該基準電圧設定素子のアノード端又はカソード端に一端を接続した第４の抵抗素子との直列回路を有する比較部とを備え、前記直列回路に流れる電流の有無に応じて、電圧供給部の出力電圧を変更するようにしてあることにより、比較的簡便な構成で電流制御をして、ＬＥＤに常に略一定の電流を供給することができ、直列接続したＬＥＤの数に拘わらず、時間変化、温度変化などに基づいて生じるＬＥＤの明るさ変動を抑制することができる。また、ＬＥＤに短絡破損が生じて負荷が大きく変動した場合であっても、常に略一定の電流をＬＥＤに供給することができ、ＬＥＤに過剰電流が流れることを防止でき、信頼性が向上する。また、制限抵抗を用いる必要がないため、制限抵抗で生じた発熱、電力消費を無くすことができ、無駄な消費電力を低減して効率を上げることができる。   In the second invention, one end of the second resistance element is connected to one end of the third resistance element with the other end grounded, and the threshold setting unit is connected to the reference voltage terminal of the reference voltage setting element at the one end. And a comparison unit having a series circuit of the reference voltage setting element and a fourth resistance element having one end connected to the anode end or the cathode end of the reference voltage setting element, and the presence or absence of a current flowing through the series circuit. Accordingly, by changing the output voltage of the voltage supply unit, it is possible to control the current with a relatively simple configuration and always supply a substantially constant current to the LED. Regardless of the number, it is possible to suppress the brightness variation of the LED that occurs based on time change, temperature change, and the like. Further, even when a short circuit breakage occurs in the LED and the load greatly fluctuates, it is possible to always supply a substantially constant current to the LED, prevent an excessive current from flowing through the LED, and improve reliability. . Further, since it is not necessary to use a limiting resistor, heat generation and power consumption caused by the limiting resistor can be eliminated, and wasteful power consumption can be reduced to increase efficiency.

第３発明にあっては、電圧検出部が検出した出力電圧が、所定の閾値電圧を越えた場合、電圧供給部の出力電圧を下げることにより、無負荷時などに出力電圧が異常に上昇することを防止できる。   In the third aspect of the invention, when the output voltage detected by the voltage detection unit exceeds a predetermined threshold voltage, the output voltage is abnormally increased when there is no load by reducing the output voltage of the voltage supply unit. Can be prevented.

以下、本発明をその実施の形態を示す図面に基づいて説明する。図１は本発明に係る照明装置の構成を示すブロック図であり、図２は本発明に係る電源装置の構成を示す回路図である。照明装置は、電源装置及び該電源装置の出力側に複数直列に接続されたＬＥＤ９、９、…を有する。電源装置の入力側には、商用電源１を接続してある。   Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is a block diagram showing a configuration of a lighting device according to the present invention, and FIG. 2 is a circuit diagram showing a configuration of a power supply device according to the present invention. The lighting device includes a power supply device and a plurality of LEDs 9, 9,... Connected in series on the output side of the power supply device. A commercial power source 1 is connected to the input side of the power supply device.

図において、２はフィルタ回路である。フィルタ回路２は、商用電源１から流入するノイズを遮断する。整流回路３は、ダイオードブリッジで構成される全波整流回路であり、入力された交流電圧を全波整流し、全波整流した直流電圧をコンデンサ４へ出力する。コンデンサ４は、整流回路３から入力された直流電圧を平滑し、ほぼ一定の直流電圧をコンバータ回路５へ出力する。   In the figure, 2 is a filter circuit. The filter circuit 2 blocks noise flowing from the commercial power source 1. The rectifier circuit 3 is a full-wave rectifier circuit composed of a diode bridge, and full-wave rectifies the input AC voltage, and outputs the full-wave rectified DC voltage to the capacitor 4. The capacitor 4 smoothes the DC voltage input from the rectifier circuit 3 and outputs a substantially constant DC voltage to the converter circuit 5.

コンバータ回路５は、一次巻線及び二次巻線を有し、入力された直流電圧を所定の直流電圧に降圧するためのトランス部５２と、トランス部５２の一次巻線の一端にドレインを接続してあり、所定の発振周波数（例えば、４０ｋＨｚ）でスイッチング動作をするＦＥＴ５３と、ＦＥＴ５３のスイッチング動作を制御するため、ＦＥＴ５３のゲートにドライブ信号を、出力端ＤＲを介して出力するＰＷＭ制御部５１と、ＦＥＴ５３のドレイン・ソース間を流れる電流を検出し、検出した電流を電圧に変換してＰＷＭ制御部５１のセンス端ＩＳへ出力し、ＰＷＭ制御部５１の各周期毎の電流制御をするために一端をＦＥＴ５３のソースに接続し、他端を接地してある抵抗５４と、ＦＥＴ５３の発振を停止させ間欠発振モードに移行するための制御信号を、フィードバック端ＦＢを介してＰＷＭ制御部５１へ出力するフォトトランジスタ５５ａ、５５ｂとを備える。すなわち、ＰＷＭ制御部５１は、フォトトランジスタ５５ａ、又はフォトトランジスタ５５ｂのいずれかがオンになっている間、ＦＥＴ５３のスイッチング動作をドライブするドライブ信号の出力を停止する。   The converter circuit 5 includes a primary winding and a secondary winding, and a drain is connected to one end of the primary winding of the transformer 52 and a transformer 52 for stepping down the input DC voltage to a predetermined DC voltage. The FET 53 that performs a switching operation at a predetermined oscillation frequency (for example, 40 kHz) and the PWM control unit 51 that outputs a drive signal to the gate of the FET 53 via the output terminal DR in order to control the switching operation of the FET 53. The current flowing between the drain and the source of the FET 53 is detected, the detected current is converted into a voltage and output to the sense terminal IS of the PWM controller 51, and the current of each period of the PWM controller 51 is controlled. And a resistor 54 having one end connected to the source of the FET 53 and the other end grounded, and a control for stopping the oscillation of the FET 53 and shifting to the intermittent oscillation mode. Comprising Nos a phototransistor 55a to be outputted to the PWM control unit 51 via the feedback end FB, and 55b. That is, the PWM control unit 51 stops outputting the drive signal that drives the switching operation of the FET 53 while either the phototransistor 55a or the phototransistor 55b is on.

電流検出回路６は、抵抗６１を備え、抵抗６１は、ＬＥＤ９、９、…に直列に接続するようにしてあり、抵抗６１の一端は定電流制御回路７へ接続してあり、他端はコンバータ回路５の二次巻線の一端に接続してある。また、二次巻線の前記一端は接地してある。これにより、ＬＥＤ９、９、…に流れる電流Ｉｆに抵抗６１の抵抗値を積算して得られる電圧を定電流制御回路７へ出力する。   The current detection circuit 6 includes a resistor 61. The resistor 61 is connected in series to the LEDs 9, 9,..., One end of the resistor 61 is connected to the constant current control circuit 7, and the other end is a converter. It is connected to one end of the secondary winding of the circuit 5. The one end of the secondary winding is grounded. As a result, a voltage obtained by integrating the resistance value of the resistor 61 to the current If flowing through the LEDs 9, 9... Is output to the constant current control circuit 7.

定電流制御回路７は、演算増幅器７１を備え、電流検出回路６の抵抗６１の前記一端を、抵抗７９を介して演算増幅器７１の非反転入力端に接続してある。また、演算増幅器７１の反転入力端と出力端との間には抵抗７２を接続してあり、演算増幅器７１の反転入力端と接地との間には抵抗７３を接続してある。これにより、抵抗６１で検出された電流Ｉｆは、電圧に変換され、演算増幅器７１の非反転入力端に入力され、抵抗７２、７３の抵抗値で決定される増幅度に応じて、演算増幅器７１は正相増幅器として動作して出力端に電圧Ｖｏを出力する。   The constant current control circuit 7 includes an operational amplifier 71, and the one end of the resistor 61 of the current detection circuit 6 is connected to the non-inverting input terminal of the operational amplifier 71 through a resistor 79. A resistor 72 is connected between the inverting input terminal and the output terminal of the operational amplifier 71, and a resistor 73 is connected between the inverting input terminal of the operational amplifier 71 and the ground. As a result, the current If detected by the resistor 61 is converted into a voltage, input to the non-inverting input terminal of the operational amplifier 71, and the operational amplifier 71 according to the amplification degree determined by the resistance values of the resistors 72 and 73. Operates as a positive phase amplifier and outputs a voltage Vo to the output terminal.

また、定電流制御回路７は、演算増幅器７１の出力端と接地との間に直列に接続した抵抗７４及び抵抗７５と、抵抗７４及び抵抗７５の接続点に基準電圧端子を接続し、アノード端子を接地したシャントレギュレータ７８（基準電圧設定素子）と、演算増幅器７１の出力端とシャントレギュレータ７８のカソード端子との間に直列に接続した抵抗７７及びフォトダイオード７６ｂとを備える。これにより、抵抗７４、７５には、シャントレギュレータ７８の基準電圧端子の電圧Ｖｒを抵抗７５の抵抗値で割った値の設定電流Ｉｒ（閾値電流）を常に流すように設定することができる。   The constant current control circuit 7 has a resistor 74 and a resistor 75 connected in series between the output terminal of the operational amplifier 71 and the ground, and a reference voltage terminal connected to a connection point between the resistor 74 and the resistor 75, and an anode terminal. A ground shunt regulator 78 (reference voltage setting element), a resistor 77 and a photodiode 76b connected in series between the output terminal of the operational amplifier 71 and the cathode terminal of the shunt regulator 78. As a result, the resistors 74 and 75 can be set so that a set current Ir (threshold current) having a value obtained by dividing the voltage Vr of the reference voltage terminal of the shunt regulator 78 by the resistance value of the resistor 75 is always supplied.

演算増幅器７１の出力端の電圧Ｖｏが上昇し、前記出力端から出力される電流Ｉｏが設定電流Ｉｒを超えた場合、設定電流Ｉｒを超えた分の余剰電流Ｉｅ（Ｉｏ−Ｉｒ）は、抵抗７７、フォトダイオード７６ｂ、及びシャントレギュレータ７８の直列回路に流れ、フォトダイオード７６ｂに電流が流れることにより、フォトトランジスタ５５ｂはオンとなる。一方、演算増幅器７１の出力端の電圧Ｖｏが低下し、前記出力端から出力される電流Ｉｏが設定電流Ｉｒ以下になった場合、抵抗７７とシャントレギュレータ７８との直列回路には余剰電流Ｉｅが流れず、フォトダイオード７６ｂに電流が流れないことにより、フォトトランジスタ５５ｂはオフとなる。   When the voltage Vo at the output terminal of the operational amplifier 71 rises and the current Io output from the output terminal exceeds the set current Ir, the surplus current Ie (Io−Ir) that exceeds the set current Ir 77, the photodiode 76b, and the shunt regulator 78 flow through a series circuit. When a current flows through the photodiode 76b, the phototransistor 55b is turned on. On the other hand, when the voltage Vo at the output terminal of the operational amplifier 71 decreases and the current Io output from the output terminal becomes equal to or lower than the set current Ir, the surplus current Ie is present in the series circuit of the resistor 77 and the shunt regulator 78. Since the current does not flow and the current does not flow to the photodiode 76b, the phototransistor 55b is turned off.

コンバータ回路５の出力端間には、抵抗８１、フォトダイオード８２ａ、及びツェナーダイオード８３を直列に接続してある。コンバータ回路５の出力電圧が、ツェナーダイオード８３で設定される閾値電圧を超えた場合、フォトダイオード８２ａに電流が流れ、フォトトランジスタ５５ａをオンにする。また、コンバータ回路５の出力電圧が、前記閾値電圧以下になった場合、フォトダイオード８２ａには電流が流れず、フォトトランジスタ５５ａをオフにする。これにより、無負荷状態などにおいて、コンバータ回路５の出力電圧が異常に上昇した場合、ＦＥＴ５３の発振動作を停止して、コンバータ回路の出力電圧を低下させることができる。   Between the output terminals of the converter circuit 5, a resistor 81, a photodiode 82a, and a Zener diode 83 are connected in series. When the output voltage of the converter circuit 5 exceeds the threshold voltage set by the Zener diode 83, a current flows through the photodiode 82a, turning on the phototransistor 55a. Further, when the output voltage of the converter circuit 5 becomes equal to or lower than the threshold voltage, no current flows through the photodiode 82a, and the phototransistor 55a is turned off. Thereby, when the output voltage of the converter circuit 5 rises abnormally in a no-load state or the like, the oscillation operation of the FET 53 can be stopped and the output voltage of the converter circuit can be lowered.

次に本発明の電源装置の動作について説明する。電源装置の入力端に交流電圧を印加することにより、ＰＷＭ制御部５１は、所定の発振周波数（例えば、４０ｋＨｚ）、パルス幅（例えば、デューティ比５０％）を有するドライブ信号を出力端ＤＲからＦＥＴ５３のゲートへ出力し、ＦＥＴ５３はスイッチング動作を行う。これにより、コンバータ回路５は所定の出力電圧を出力し、直列接続したＬＥＤ９、９、…に直流電流を供給する。   Next, the operation of the power supply device of the present invention will be described. By applying an AC voltage to the input terminal of the power supply device, the PWM control unit 51 causes a drive signal having a predetermined oscillation frequency (for example, 40 kHz) and pulse width (for example, a duty ratio of 50%) to be output from the output terminal DR to the FET 53. The FET 53 performs a switching operation. As a result, the converter circuit 5 outputs a predetermined output voltage and supplies a direct current to the LEDs 9, 9,... Connected in series.

ＰＷＭ制御部５１は、ＦＥＴ５３のドレイン・ソース間を流れる電流を抵抗５４で電圧に変換し、変換した電圧をセンス端ＩＳで取得し、取得した電圧に応じて電流制御を行う。これにより、各周期毎に過電流保護回路を設定することができる。   The PWM control unit 51 converts the current flowing between the drain and source of the FET 53 into a voltage by the resistor 54, acquires the converted voltage at the sense terminal IS, and performs current control according to the acquired voltage. Thereby, an overcurrent protection circuit can be set for each period.

電流検出回路６の抵抗６１は、ＬＥＤ９、９、…を流れる電流Ｉｆを検出し、検出した電流Ｉｆを電圧に変換して、演算増幅器７１の非反転入力端へ出力する。演算増幅器７１は、入力された電圧を、所定の増幅率で増幅した電圧Ｖｏを出力端から出力する。   The resistor 61 of the current detection circuit 6 detects the current If flowing through the LEDs 9, 9,..., Converts the detected current If into a voltage, and outputs the voltage to the non-inverting input terminal of the operational amplifier 71. The operational amplifier 71 outputs a voltage Vo obtained by amplifying the input voltage with a predetermined amplification factor from the output terminal.

ＬＥＤ９、９、…の周囲温度が上昇することにより、ＬＥＤ９、９、…夫々の順方向電圧Ｖｆが、例えば、３．５Ｖから３．０Ｖに低下した場合、コンバータ回路５の出力電圧は一定のままであるから、ＬＥＤ９、９、…に流れる電流Ｉｆは増加する。電流Ｉｆが増加した場合、演算増幅器７１の非反転入力端に入力される電圧も増加し、演算増幅器７１の出力端の電圧Ｖｏは上昇する。   When the ambient voltage of the LEDs 9, 9,... Rises, the forward voltage Vf of each of the LEDs 9, 9,... Decreases, for example, from 3.5V to 3.0V, the output voltage of the converter circuit 5 is constant. Therefore, the current If flowing through the LEDs 9, 9,... Increases. When the current If increases, the voltage input to the non-inverting input terminal of the operational amplifier 71 also increases, and the voltage Vo at the output terminal of the operational amplifier 71 increases.

出力端の電圧Ｖｏが上昇すると、出力端から出力される電流Ｉｏも増加し、電流Ｉｏが設定電流Ｉｒを超えた場合、余剰電流Ｉｅ（Ｉｏ−Ｉｒ）が抵抗７７、フォトダイオード７６ｂ、シャントレギュレータ７８を流れ、フォトダイオード７６ｂを流れる電流Ｉｅにより、フォトトランジスタ５５ｂがオンとなる。これにより、ＰＷＭ制御部５１のフィードバック端ＦＢがＬＯＷレベルになり、ＦＥＴ５３のゲートへ出力するドライブ信号を停止して、ＦＥＴ５３の発振動作が一旦停止する間欠発振モードに移行する。   When the voltage Vo at the output end rises, the current Io output from the output end also increases. When the current Io exceeds the set current Ir, the surplus current Ie (Io-Ir) becomes the resistor 77, the photodiode 76b, the shunt regulator. The phototransistor 55b is turned on by the current Ie flowing through 78 and flowing through the photodiode 76b. As a result, the feedback terminal FB of the PWM control unit 51 becomes the LOW level, the drive signal output to the gate of the FET 53 is stopped, and the mode is shifted to the intermittent oscillation mode in which the oscillation operation of the FET 53 is temporarily stopped.

ＦＥＴ５３の発振動作が停止することにより、コンバータ回路５の出力電圧は低下し、ＬＥＤ９、９、…に流れる電流Ｉｆは減少する。これにより、周囲温度の変化などにより、ＬＥＤ９、９、…の順方向電圧Ｖｆが低下した場合であっても、電流Ｉｆの増加を抑制することができる。   When the oscillation operation of the FET 53 is stopped, the output voltage of the converter circuit 5 is lowered, and the current If flowing through the LEDs 9, 9,. Thereby, even if it is a case where forward voltage Vf of LED9, ... is reduced by change of ambient temperature etc., the increase in the current If can be suppressed.

一方、電流Ｉｆが減少した場合、演算増幅器７１の非反転入力端に入力される電圧も減少し、演算増幅器７１の出力端の電圧Ｖｏは低下する。出力端の電圧Ｖｏが低下すると、出力端から出力される電流Ｉｏが減少し、電流Ｉｏが設定電流Ｉｒ以下になった場合、余剰電流Ｉｅはゼロとなり、フォトダイオード７６ｂには電流Ｉｅが流れない。このため、フォトトランジスタ５５ｂがオフとなる。これにより、ＰＷＭ制御部５１のフィードバック端ＦＢがＨＩＧＨレベルになり、停止していたドライブ信号をＦＥＴ５３のゲートへ出力し、コンバータ回路５は間欠発振モードから通常発振モードに移行する。   On the other hand, when the current If decreases, the voltage input to the non-inverting input terminal of the operational amplifier 71 also decreases, and the voltage Vo at the output terminal of the operational amplifier 71 decreases. When the voltage Vo at the output terminal decreases, the current Io output from the output terminal decreases, and when the current Io becomes equal to or less than the set current Ir, the surplus current Ie becomes zero and the current Ie does not flow through the photodiode 76b. . For this reason, the phototransistor 55b is turned off. As a result, the feedback terminal FB of the PWM control unit 51 becomes HIGH level, and the stopped drive signal is output to the gate of the FET 53, and the converter circuit 5 shifts from the intermittent oscillation mode to the normal oscillation mode.

ＦＥＴ５３の発振動作が行われることにより、コンバータ回路５の出力電圧は上昇し、ＬＥＤ９、９、…に流れる電流Ｉｆは上昇する。これにより、電流Ｉｆの減少を抑制し、周囲温度の変化、負荷変動などが生じた場合であっても、略一定の電流ＩｆをＬＥＤ９、９、…に供給することができる。   When the oscillation operation of the FET 53 is performed, the output voltage of the converter circuit 5 increases, and the current If flowing through the LEDs 9, 9,. Thereby, it is possible to suppress a decrease in the current If and to supply a substantially constant current If to the LEDs 9, 9,.

図３はＬＥＤ９、９、…に流れる電流Ｉｆの変化を示すタイムチャートである。図に示すように、当初、目標値であった電流Ｉｆは、温度変化、負荷変動などにより時点ｔ１で上昇し始めたとする。時点ｔ１までは、ＦＥＴ５３は通常発振モードで動作している。   FIG. 3 is a time chart showing changes in the current If flowing in the LEDs 9, 9,. As shown in the figure, it is assumed that the current If, which was the target value at the beginning, starts to increase at a time point t1 due to a temperature change, a load change, and the like. Until the time t1, the FET 53 operates in the normal oscillation mode.

時点ｔ１で電流Ｉｆの上昇を検出した電流検出回路６は、検出した電流から変換した電圧を定電流制御回路７の演算増幅器７１へ出力する。演算増幅器７１は入力された電圧に応じた電圧Ｖｏを出力する。電圧Ｖｏにより余剰電流Ｉｅがフォトダイオード７６ｂに流れることにより、ＦＥＴ５３は一旦発振動作を停止し、間欠発振モードに移行する。   The current detection circuit 6 that has detected an increase in the current If at time t1 outputs a voltage converted from the detected current to the operational amplifier 71 of the constant current control circuit 7. The operational amplifier 71 outputs a voltage Vo corresponding to the input voltage. When the surplus current Ie flows to the photodiode 76b by the voltage Vo, the FET 53 temporarily stops the oscillation operation and shifts to the intermittent oscillation mode.

ＦＥＴ５３の発振動作を停止することにより、コンバータ回路５の出力電圧は低下し、上昇していた電流Ｉｆも減少し始める。電流Ｉｆの減少を検出した電流検出回路６は、検出した電流から変換した電圧を定電流制御回路７の演算増幅器７１へ出力する。演算増幅器７１は入力された電圧に応じた電圧Ｖｏを出力する。電圧Ｖｏが低下して余剰電流Ｉｅがフォトダイオード７６ｂに流れなくなった場合（時点ｔ２）、ＦＥＴ５３は発振動作を開始し、通常発振モードに移行する。コンバータ回路５の出力電圧は上昇し、電流Ｉｆは増加し始め、所定の目標値になる。   By stopping the oscillating operation of the FET 53, the output voltage of the converter circuit 5 decreases, and the current If that has increased starts to decrease. The current detection circuit 6 that detects the decrease in the current If outputs a voltage converted from the detected current to the operational amplifier 71 of the constant current control circuit 7. The operational amplifier 71 outputs a voltage Vo corresponding to the input voltage. When the voltage Vo decreases and the surplus current Ie does not flow to the photodiode 76b (time t2), the FET 53 starts an oscillation operation and shifts to the normal oscillation mode. The output voltage of the converter circuit 5 rises, the current If starts to increase, and reaches a predetermined target value.

このように、周囲温度の変化によるＬＥＤ９、９、…の順方向電圧の変動、負荷変動などが生じた場合であっても、ＬＥＤ９、９、…に流れる電流Ｉｆを略一定の目標値に保つことができる。   As described above, even when forward voltage fluctuations or load fluctuations of the LEDs 9, 9,... Occur due to changes in the ambient temperature, the current If flowing through the LEDs 9, 9,. be able to.

以上説明したように、本発明にあっては、ＬＥＤ９、９、…に流れる電流を抵抗６１で検出し、検出した電流を電圧に変換して演算増幅器７１へ出力し、入力された電圧に応じた電圧Ｖｏを演算増幅器７１で出力し、電圧Ｖｏに応じて演算増幅器７１から出力される電流Ｉｏと、抵抗７４、７５を流れる設定電流Ｉｒとを比較する。電流Ｉｏが設定電流Ｉｒを超える場合には、余剰電流Ｉｅ（Ｉｏ−Ｉｒ）を抵抗７７、フォトダイオード７６ｂ、シャントレギュレータ７８の直列回路に流し、ＰＷＭ制御部５１がＦＥＴ５３のゲートへ出力するドライブ信号を停止することにより、コンバータ回路５の出力電圧を下げ、電流Ｉｆを小さくする。   As described above, in the present invention, the current flowing through the LEDs 9, 9,... Is detected by the resistor 61, the detected current is converted into a voltage and output to the operational amplifier 71 according to the input voltage. The voltage Vo is output by the operational amplifier 71, and the current Io output from the operational amplifier 71 according to the voltage Vo is compared with the set current Ir flowing through the resistors 74 and 75. When the current Io exceeds the set current Ir, the surplus current Ie (Io−Ir) is passed through the series circuit of the resistor 77, the photodiode 76b, and the shunt regulator 78, and the drive signal that the PWM control unit 51 outputs to the gate of the FET 53 Is stopped, the output voltage of the converter circuit 5 is lowered and the current If is reduced.

一方、電流Ｉｏが設定電流Ｉｒ以下である場合には、余剰電流Ｉｅがフォトダイオード７６ｂを流れず、ＰＷＭ制御部５１がＦＥＴ５３のゲートへ出力するドライブ信号を出力することにより、コンバータ回路５の出力電圧を上げ、電流Ｉｆを大きくする。これにより、周囲温度の変化によるＬＥＤ９、９、…の順方向電圧の変動、負荷変動などが生じた場合であっても、ＬＥＤ９、９、…に流れる電流Ｉｆを略一定の目標値に保つことができる。   On the other hand, when the current Io is equal to or less than the set current Ir, the surplus current Ie does not flow through the photodiode 76b, and the PWM control unit 51 outputs a drive signal output to the gate of the FET 53, whereby the output of the converter circuit 5 is output. Increase the voltage and increase the current If. This maintains the current If flowing in the LEDs 9, 9, etc. at a substantially constant target value even when forward voltage fluctuations or load fluctuations of the LEDs 9, 9, etc. occur due to changes in the ambient temperature. Can do.

これにより、比較的簡便な構成で、直列接続したＬＥＤの数に拘わらず、常に略一定の電流をＬＥＤに流すことができるため、時間変化、温度変化に基づいて生じるＬＥＤの明るさ、輝度の変動を抑制することができる。また、ＬＥＤに短絡破損が生じて負荷が大きく変動した場合であっても、常に略一定の電流をＬＥＤに流すことができ、ＬＥＤに過剰電流が流れることを防止でき、信頼性が向上する。また、従来のように制限抵抗を用いる必要がないため、制限抵抗で生じた発熱、電力消費を無くすことができ、無駄な消費電力を低減して効率を上げることができる。   As a result, it is possible to pass a substantially constant current to the LED regardless of the number of LEDs connected in series with a relatively simple configuration. Therefore, the brightness and brightness of the LED generated based on time change and temperature change can be reduced. Variations can be suppressed. Further, even when a short circuit breakage occurs in the LED and the load greatly fluctuates, a substantially constant current can always flow through the LED, and an excessive current can be prevented from flowing through the LED, improving reliability. Further, since it is not necessary to use a limiting resistor as in the prior art, heat generation and power consumption caused by the limiting resistor can be eliminated, and wasteful power consumption can be reduced to increase efficiency.

また、本発明にあっては、コンバータ回路５の出力電圧が、ツェナーダイオード８３で設定される閾値電圧を超えた場合、フォトダイオード８２ａに電流が流れ、フォトトランジスタ５５ａをオンにする。これにより、無負荷状態などにおいて、コンバータ回路５の出力電圧が異常に上昇した場合、ＦＥＴ５３の発振動作を停止して、コンバータ回路５の出力電圧を低下させることができる。   In the present invention, when the output voltage of the converter circuit 5 exceeds the threshold voltage set by the Zener diode 83, a current flows through the photodiode 82a, and the phototransistor 55a is turned on. Thereby, when the output voltage of the converter circuit 5 rises abnormally in a no-load state or the like, the oscillation operation of the FET 53 can be stopped and the output voltage of the converter circuit 5 can be lowered.

上述の実施の形態においては、電源装置は、整流回路３を備える構成であったが、これに限定されるものではなく、入力電圧として交流電圧に代えて、電池により供給される直流電圧を入力する構成であってもよい。この場合は、整流回路３、コンデンサ４は不要になる。また、コンバータ回路５は、降圧型に限定されるものではなく、昇圧型、昇降圧型であってもよい。   In the above-described embodiment, the power supply device is configured to include the rectifier circuit 3. However, the power supply device is not limited to this, and a DC voltage supplied by a battery is input instead of an AC voltage as an input voltage. It may be configured to. In this case, the rectifier circuit 3 and the capacitor 4 are not necessary. The converter circuit 5 is not limited to the step-down type, and may be a step-up type or a step-up / down type.

上述の実施の形態においては、コンバータ回路５は、ＰＷＭ方式のパルス幅を変更して出力電圧を可変とする構成であったが、これに限定されるものではなく、例えば、ＶＣＯ（Voltage Controlled Oscillator、電圧制御発振器）など、出力電圧を可変できるものであれば、どのような構成であってもよい。   In the above-described embodiment, the converter circuit 5 is configured to change the output voltage by changing the pulse width of the PWM method. However, the present invention is not limited to this. For example, the converter circuit 5 is a VCO (Voltage Controlled Oscillator). As long as the output voltage can be varied, such as a voltage-controlled oscillator), any configuration may be used.

上述の実施の形態では、ＬＥＤを複数個直列に接続する構成であったが、ＬＥＤの数は特に限定されるものではなく、１個であってもよい。なお、ＬＥＤの数は多いほど、各ＬＥＤの順方向電圧の変動が加算されるため、本発明による効果は、より顕著に現れるといえる。また、ＬＥＤに代えて有機ＥＬ素子などの電流駆動素子を負荷として用いることも可能である。   In the above-described embodiment, a plurality of LEDs are connected in series. However, the number of LEDs is not particularly limited, and may be one. In addition, since the fluctuation | variation of the forward voltage of each LED is added, so that there are many LED, it can be said that the effect by this invention appears more notably. In addition, a current driving element such as an organic EL element can be used as a load instead of the LED.

上述の実施の形態においては、抵抗６１で電流Ｉｆから変換された電圧を正相増幅器として作動する演算増幅器７１へ出力する構成であったが、演算増幅器７１を逆相増幅器として作動させる構成であってもよい。この場合は、フォトトランジスタ５５ｂの出力を反転させた信号をＰＷＭ制御部５１へ出力することができる。   In the above-described embodiment, the voltage converted from the current If by the resistor 61 is output to the operational amplifier 71 that operates as a positive phase amplifier. However, the operational amplifier 71 operates as a negative phase amplifier. May be. In this case, a signal obtained by inverting the output of the phototransistor 55 b can be output to the PWM control unit 51.

上述の実施の形態において、抵抗６１、７２、７３、７４、７５、７７は、１つの抵抗として構成してあるが、各抵抗は１つの抵抗に限定されるものではなく、複数の抵抗を直列又は並列に接続した抵抗群であってもよい。また、可変抵抗を用いる構成であってもよい。また、抵抗７７は、シャントレギュレータ７８のカソード側に代えてアノード側に接続する構成でもよい。   In the above-described embodiment, the resistors 61, 72, 73, 74, 75, and 77 are configured as one resistor. However, each resistor is not limited to one resistor, and a plurality of resistors are connected in series. Or it may be a group of resistors connected in parallel. Moreover, the structure using a variable resistance may be sufficient. The resistor 77 may be connected to the anode side instead of the cathode side of the shunt regulator 78.

本発明に係る照明装置の構成を示すブロック図である。It is a block diagram which shows the structure of the illuminating device which concerns on this invention. 本発明に係る電源装置の構成を示す回路図である。It is a circuit diagram which shows the structure of the power supply device which concerns on this invention. ＬＥＤに流れる電流の変化を示すタイムチャートである。It is a time chart which shows the change of the electric current which flows into LED. 従来のＬＥＤ用の電源装置の構成を示すブロック図である。It is a block diagram which shows the structure of the power supply device for conventional LED.

符号の説明Explanation of symbols

５ コンバータ回路
６ 電流検出回路
７ 定電流制御回路
８ 電圧検出回路
９ ＬＥＤ
５１ ＰＷＭ制御部
５３ ＦＥＴ
５５ａ、５５ｂ フォトトランジスタ
６１ 抵抗
７１ 演算増幅器
７２、７３、７４、７５、７７ 抵抗
７６ｂ フォトダイオード
７８ シャントレギュレータ
８１ 抵抗
８２ａ フォトダイオード
８３ ツェナーダイオード 5 Converter circuit 6 Current detection circuit 7 Constant current control circuit 8 Voltage detection circuit 9 LED
51 PWM controller 53 FET
55a, 55b Phototransistor 61 Resistor 71 Operational amplifier 72, 73, 74, 75, 77 Resistor 76b Photodiode 78 Shunt regulator 81 Resistor 82a Photodiode 83 Zener diode

Claims (4)

ＬＥＤに電流を供給する電源装置において、
出力電圧可変の電圧供給部と、
前記ＬＥＤに供給する電流を検出する電流検出部と、
閾値電流を設定する閾値設定部と、
前記電流検出部が検出した電流と前記閾値電流とを比較する比較部と
を備え、
該比較部が比較した結果に基づいて、前記電圧供給部の出力電圧を変更して前記ＬＥＤに流れる電流を略一定にするようにしてあることを特徴とする電源装置。 In a power supply for supplying current to an LED,
A voltage supply section with variable output voltage;
A current detector for detecting a current supplied to the LED;
A threshold setting unit for setting a threshold current;
A comparison unit that compares the current detected by the current detection unit with the threshold current;
A power supply apparatus characterized in that, based on a result of comparison by the comparison unit, an output voltage of the voltage supply unit is changed to make a current flowing through the LED substantially constant. 前記電流検出部は、
前記ＬＥＤに直列に接続される第１の抵抗素子を有し、
前記閾値設定部は、
カソード端子、アノード端子、及び基準電圧端子を有する基準電圧設定素子の基準電圧端子に、第２の抵抗素子及び第３の抵抗素子夫々の一端を接続してあり、
前記比較部は、
前記第２の抵抗素子及び第３の抵抗素子夫々の他端間に接続され、前記基準電圧設定素子と、該基準電圧設定素子のカソード端子又はアノード端子に一端を接続した第４の抵抗素子との直列回路を有しており、
前記ＬＥＤに供給される電流を前記第１の抵抗素子で変換して得られる電圧を前記第２の抵抗素子の他端へ出力するようにしてあり、前記直列回路を流れる電流に基づいて、前記電圧供給部の出力電圧を変更するようにしてあることを特徴とする請求項１に記載の電源装置。 The current detector is
A first resistance element connected in series to the LED;
The threshold setting unit includes:
One end of each of the second resistance element and the third resistance element is connected to a reference voltage terminal of a reference voltage setting element having a cathode terminal, an anode terminal, and a reference voltage terminal,
The comparison unit includes:
A reference voltage setting element connected between the other ends of the second resistance element and the third resistance element; a fourth resistance element having one end connected to the cathode terminal or the anode terminal of the reference voltage setting element; Has a series circuit of
A voltage obtained by converting the current supplied to the LED with the first resistance element is output to the other end of the second resistance element, and based on the current flowing through the series circuit, 2. The power supply device according to claim 1, wherein the output voltage of the voltage supply unit is changed. 前記出力電圧を検出する電圧検出部を備え、
該電圧検出部が検出した電圧が、所定の閾値電圧を超えた場合に、前記電圧供給部の出力電圧を下げるようにしてあることを特徴とする請求項１又は請求項２に記載の電源装置。 A voltage detection unit for detecting the output voltage;
The power supply device according to claim 1 or 2, wherein when the voltage detected by the voltage detection unit exceeds a predetermined threshold voltage, the output voltage of the voltage supply unit is lowered. . ＬＥＤと、該ＬＥＤに電流を供給する請求項１乃至請求項３のいずれかに記載の電源装置とを備えることを特徴とする照明装置。   An illumination device comprising: an LED; and the power supply device according to claim 1 for supplying a current to the LED.
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CN113178171A (en) * 2021-04-07 2021-07-27 深圳Tcl新技术有限公司 Backlight driving circuit, liquid crystal display device and backlight driving method
CN113178171B (en) * 2021-04-07 2022-09-02 深圳Tcl新技术有限公司 Backlight driving circuit, liquid crystal display device and backlight driving method

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