JP2006049423A - Constant-current driving circuit - Google Patents

Constant-current driving circuit Download PDF

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JP2006049423A
JP2006049423A JP2004225541A JP2004225541A JP2006049423A JP 2006049423 A JP2006049423 A JP 2006049423A JP 2004225541 A JP2004225541 A JP 2004225541A JP 2004225541 A JP2004225541 A JP 2004225541A JP 2006049423 A JP2006049423 A JP 2006049423A
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voltage
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constant current
led group
drive circuit
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JP2006049423A5 (en
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Taro Kimura
太郎 木村
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Sharp NEC Display Solutions Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant-current driving circuit that can always and stably drive all LEDs with a constant current while utilizing PWM control. <P>SOLUTION: The constant-current driving circuit applies a DC voltage generated by boosting the voltage supplied from a power source 13 by means of a boosting circuit 7 to the LEDs 6 in a pulse-like state by controlling the DC voltage by means of a constant-voltage control unit 8. When the operations of the LEDs 6 are controlled by means of a control unit 2 and a PWM 3 and currents flow to the LEDs 6, the constant-voltage control unit 8 controls the magnitude of the voltages applied to the LEDs 6 by acquiring the information about the values of the currents flowing to the LEDs 6 from the potential difference between both ends of a resistor 4 and ON/OFF controlling the voltages applied to the LEDs 6 from the boosting circuit 7 to a high frequency based on the information. Consequently, the currents flowing to the LEDs 6 can be maintained constantly. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

この発明は、ＬＥＤ（発光ダイオード）等の発光素子を、目的とする輝度で安定して発光させるための定電流駆動回路に関する。   The present invention relates to a constant current driving circuit for causing a light emitting element such as an LED (light emitting diode) to emit light stably at a target luminance.

ＲＧＢ各色のＬＥＤを利用して様々な色を表示するには、各色のＬＥＤを同様の輝度で安定して発光させることが必要となる。ＬＥＤによるカラー表示は、携帯電話等の電子機器で利用されるバックライトの他、自動車のスピードメータ等の照明や、ディスプレイ等の表示装置など、様々な分野で利用が進んでおり、ＬＥＤを安定して発光させることを目的として定電流で駆動するための様々な技術が存在する。例えば、特許文献１は、ＰＷＭ（Pulse Width Modulation）制御によって、ＲＧＢ各色のＬＥＤを安定駆動するための技術である。   In order to display various colors using the RGB LEDs, it is necessary to cause the LEDs of each color to emit light stably with the same luminance. LED color display is used in various fields such as backlights used in electronic devices such as mobile phones, lighting for automobile speedometers, and display devices such as displays. There are various techniques for driving at a constant current for the purpose of emitting light. For example, Patent Document 1 is a technique for stably driving RGB LEDs by PWM (Pulse Width Modulation) control.

特開２０００−２１４８２５号公報JP 2000-214825 A

特許文献１は、ＲＧＢ各色のＬＥＤ毎に定電圧を印加して、各ＬＥＤにおける順方向降下電圧の差異を各ＬＥＤ毎に設けた調整用抵抗で調節することで、定電流での安定した発光を可能とする技術である。携帯電話のような比較的小規模な回路に利用する場合は、このような技術でも十分対応が可能であるが、例えばディスプレイ等の大型の電子機器など、多数のＬＥＤをバックライトとして利用して高輝度を実現する必要がある大規模な回路においては、順方向電圧のバラツキを個別に調整用抵抗で調節することは困難であり、その結果、定電流駆動によりＬＥＤの輝度を均一に保つことができず、輝度ムラ等のディスプレイの画質劣化が発生するという問題があった。   In Patent Document 1, a constant voltage is applied to each LED of each RGB color, and a difference in forward voltage drop in each LED is adjusted by an adjustment resistor provided for each LED, thereby stabilizing light emission at a constant current. This is a technology that enables When used in a relatively small circuit such as a cellular phone, such a technique can be adequately used. For example, a large number of LEDs such as a large electronic device such as a display are used as a backlight. In large-scale circuits that need to achieve high brightness, it is difficult to individually adjust the variation in forward voltage with an adjusting resistor. As a result, the LED brightness can be kept uniform by constant current drive. There is a problem that the image quality of the display such as luminance unevenness is deteriorated.

特許文献１では、アノード側にＤ／Ｄコンバータの発生する電圧を印加したＬＥＤのカソード側をスイッチングＦＥＴのドレインに接続し、制御部が、当該スイッチングＦＥＴのゲートにＰＷＭ制御（Pulse Width Modulation）によるパルス電圧を印加してスイッチング動作を制御することによってＬＥＤの駆動を行う。即ちＰＷＭによるパルス電圧のオン、オフにより、ＬＥＤの点灯と消灯を制御する。このとき、Ｄ／Ｄコンバータの制御も制御部が行っている。   In Patent Document 1, the cathode side of the LED to which the voltage generated by the D / D converter is applied on the anode side is connected to the drain of the switching FET, and the control unit applies PWM control (Pulse Width Modulation) to the gate of the switching FET. The LED is driven by controlling the switching operation by applying a pulse voltage. That is, the turning on and off of the LED is controlled by turning on and off the pulse voltage by PWM. At this time, the control unit also controls the D / D converter.

しかし、この方法では、ＬＥＤを消灯した状態から点灯するときに問題が生ずることがある。具体的には、ＬＥＤが消灯され電圧の印加もされていない状態から点灯する場合、制御部によりＬＥＤへの定電圧の印加を開始すると同時にスイッチングＦＥＴをオンに制御しても、その瞬間にはＤ／Ｄコンバータによる電圧の発生と印加が開始された状態であるため十分な電圧が得られなかったり、あるいは制御部とＤ／Ｄコンバータの間に残留する電荷の影響を受けてＤ／Ｄコンバータの発生電圧が正確に制御されないといったことがある。そのため、ＬＥＤに流れる電流波形で見た場合、消灯から点灯へ、パルス波形で急峻に立ち上がるように制御しているにも拘わらず、実際には、意図した電流値に至るまでにタイムラグが生じ、その間は徐々に電流値が上昇する電流波形のなまりが生じてしまうことがあった。この場合、所定の電流値に至るまでの間は、ＬＥＤを本来意図した輝度で発光させることができない。ＲＧＢの各色１個ずつのＬＥＤを利用する携帯電話のような小規模回路や、高速な動作を必要としない装置で利用する場合であれば、このような現象が発生しても問題はない。しかし、多数のＬＥＤを直列接続したり大電流駆動型の高輝度ＬＥＤを利用して実現するディスプレイ等の電子機器においては、電流の立ち上がりにつれて輝度が変化する症状が顕著なものとなる。そのため、例えば動画像等を表示する場合など高速な動作を必要とするディスプレイには利用できないという問題があった。   However, this method may cause a problem when the LED is turned on from an unlit state. Specifically, when the LED is turned off and no light is applied, even if the switching FET is turned on at the same time as the controller starts applying a constant voltage to the LED, at that moment Since the generation and application of the voltage by the D / D converter are started, a sufficient voltage cannot be obtained, or the D / D converter is affected by the electric charge remaining between the control unit and the D / D converter. The generated voltage may not be accurately controlled. Therefore, in terms of the current waveform that flows through the LED, in spite of the fact that it is controlled to rise sharply with a pulse waveform from off to on, a time lag occurs until the intended current value is reached, During that time, the current waveform gradually increased, and the current waveform was sometimes rounded. In this case, the LED cannot emit light with originally intended luminance until the predetermined current value is reached. There is no problem even if such a phenomenon occurs if it is used in a small-scale circuit such as a mobile phone that uses one LED for each color of RGB or a device that does not require high-speed operation. However, in an electronic device such as a display realized by connecting a large number of LEDs in series or using a high-intensity LED driven at high current, a symptom in which luminance changes as the current rises becomes significant. Therefore, there is a problem that it cannot be used for a display that requires a high-speed operation, for example, when displaying a moving image or the like.

スイッチングＦＥＴによりＬＥＤを消灯しているときにもＬＥＤへ定電圧を印加し続ければ、このような現象を回避することはできる。しかし、この場合、スイッチングＦＥＴをオンにした瞬間に過大なインラッシュ電流が流れ、ＬＥＤ等の回路の構成素子を破壊するおそれがあるという問題があった。   Such a phenomenon can be avoided if a constant voltage is continuously applied to the LED even when the LED is turned off by the switching FET. However, in this case, there is a problem that an excessive inrush current flows at the moment when the switching FET is turned on, and there is a possibility that a component of a circuit such as an LED may be destroyed.

そこで、この発明の課題は、ＰＷＭ制御を利用しながら、全てのＬＥＤを常に定電流で安定して駆動することができる定電流駆動回路を提供することにある。   Accordingly, an object of the present invention is to provide a constant current driving circuit that can stably drive all LEDs with a constant current while utilizing PWM control.

上記課題を解決すべく、請求項１の発明は、素子を所定の電流値で駆動するための定電流駆動回路であって、供給される電源電圧から前記素子に印加するパルス状の電圧を発生する電圧発生手段と、前記パルス状の電圧を印加したときに前記素子に流れる電流値を検出する電流検出手段と、前記電流検出手段の検出した電流値に従って、前記電圧供給手段の前記素子への断続的な電圧印加の開始および停止を制御する電圧制御手段とを備えることを特徴とする。   In order to solve the above problems, the invention of claim 1 is a constant current driving circuit for driving an element with a predetermined current value, and generates a pulsed voltage to be applied to the element from a supplied power supply voltage. Voltage generating means, current detecting means for detecting a current value flowing through the element when the pulsed voltage is applied, and current supply detected by the current detecting means according to the current value detected by the voltage supply means to the element. Voltage control means for controlling the start and stop of intermittent voltage application.

また、請求項２の発明は、請求項１の発明に係る定電流駆動回路であって、さらに、前記素子の動作をパルス状に周期的にオンオフ制御するＰＷＭ制御手段、を備え、前記電圧制御手段は、前記ＰＷＭ制御手段が前記素子の動作をオンオフする周期に従って、前記電圧供給手段の前記素子への断続的な電圧印加の開始および停止を制御する手段、を含むことを特徴とする。   Further, the invention of claim 2 is a constant current drive circuit according to the invention of claim 1, further comprising PWM control means for periodically turning on and off the operation of the element in a pulse form, the voltage control The means includes means for controlling the start and stop of intermittent voltage application to the element by the voltage supply means in accordance with a cycle in which the PWM control means turns on and off the operation of the element.

また、請求項３の発明は、請求項１または請求項２の発明に係る定電流駆動回路であって、前記電圧供給手段が前記素子へ印加するパルス状の電圧の周波数は、前記ＰＷＭ制御手段が前記素子の動作をオンオフする周波数に比べて高周波数であることを特徴とする。   A third aspect of the present invention is the constant current drive circuit according to the first or second aspect of the present invention, wherein the frequency of the pulse voltage applied to the element by the voltage supply means is the PWM control means. Is higher than the frequency at which the operation of the element is turned on and off.

また、請求項４の発明は、請求項１ないし請求項３のいずれかの発明に係る定電流駆動回路であって、前記電源電圧の電圧値は、前記素子に印加したときに前記素子が破損する電圧値よりも低いことを特徴とする。   According to a fourth aspect of the present invention, there is provided a constant current driving circuit according to any one of the first to third aspects of the present invention, wherein the voltage value of the power supply voltage is damaged when applied to the element. It is characterized by being lower than the voltage value to be.

また、請求項５の発明は、請求項１ないし請求項４のいずれかの発明に係る定電流駆動回路であって、前記素子は発光素子であることを特徴とする。   A fifth aspect of the invention is a constant current driving circuit according to any one of the first to fourth aspects of the invention, wherein the element is a light emitting element.

供給される電源電圧から発生した電圧を、素子に対してパルス状に周期的に印加し、このとき素子に流れる電流値を監視しながら、電圧印加の開始または停止を制御することで、素子への印加電圧を制御することができ、その結果、素子に流れる電流を目的とする所定の電流値に維持することができる。   A voltage generated from the supplied power supply voltage is periodically applied to the element in a pulsed manner, and the current value flowing through the element is monitored while controlling the start or stop of voltage application. As a result, the current flowing through the element can be maintained at a predetermined value.

＜定電流駆動回路の構成＞
図１は、この発明の一の実施の形態に係る定電流駆動回路１を示す構成図である。このように、定電流駆動回路１は、電源１３に接続された昇圧回路部７と、昇圧回路部７に接続されたＬＥＤ群６と、ＬＥＤ群６がドレインに接続されたスイッチングＦＥＴ５と、スイッチングＦＥＴ５のゲートに接続されたＰＷＭ部３と、ソースに接続された抵抗４と、ＰＷＭ部３に接続された制御部２と、ＰＷＭ部３，スイッチングＦＥＴ５のソース，昇圧回路部７および電源１３に接続された定電圧制御部８と、から構成されている。また、昇圧回路部７は、電源１３に接続されたコイル１１と、コイルに接続された整流ダイオード９と、整流ダイオード９に接続されたコンデンサ１０と、コイル１１および定電圧制御部８にドレインおよびゲートが接続されたスイッチングＦＥＴ１２と、から構成される。 <Configuration of constant current drive circuit>
FIG. 1 is a configuration diagram showing a constant current drive circuit 1 according to one embodiment of the present invention. As described above, the constant current driving circuit 1 includes the booster circuit unit 7 connected to the power supply 13, the LED group 6 connected to the booster circuit unit 7, the switching FET 5 in which the LED group 6 is connected to the drain, The PWM unit 3 connected to the gate of the FET 5, the resistor 4 connected to the source, the control unit 2 connected to the PWM unit 3, the source of the PWM unit 3, the switching FET 5, the booster circuit unit 7 and the power supply 13. And a constant voltage control unit 8 connected thereto. The booster circuit unit 7 includes a coil 11 connected to the power source 13, a rectifier diode 9 connected to the coil, a capacitor 10 connected to the rectifier diode 9, a drain and a coil 11 and a constant voltage control unit 8. And a switching FET 12 to which a gate is connected.

電源１３は、ＬＥＤ群６の駆動に利用する直流電圧を得る元になる電源電圧を発生する機能を有する。電源電圧は、これをＬＥＤ群６等の素子に直接印加しても、これらの素子が破壊されることのない電圧値を有している。   The power supply 13 has a function of generating a power supply voltage from which a DC voltage used for driving the LED group 6 is obtained. The power supply voltage has a voltage value that does not destroy these elements even if they are directly applied to the elements such as the LED group 6.

昇圧回路部（電圧発生手段）７は、電源１３から供給される電源電圧を昇圧して、ＬＥＤ群６を駆動するのに必要な直流電圧を発生する機能を有する。昇圧回路部７は、内部にコイル７およびスイッチングＦＥＴ１２を有しており、スイッチングＦＥＴ１２のスイッチング動作によりコイル７に発生する誘導電圧を利用して、昇圧したパルス状の直流電圧を得る。このスイッチングＦＥＴ１２は、後述するように、発生した直流電圧のＬＥＤ群６への印加の制御にも利用される。その他の整流ダイオード９およびコンデンサ１０は、安定した所定の直流電圧を発生するための素子である。尚、ここで利用する昇圧回路部７は、供給される電圧を昇圧して所定の直流電圧を発生する機能と、当該直流電圧の印加を制御する機能と、を有するものであれば、図１に示した態様に限らず、他の態様であっても構わない。例えば、図２に示した昇圧回路部１５のような構成であってもよい。   The booster circuit unit (voltage generating means) 7 has a function of boosting the power supply voltage supplied from the power supply 13 and generating a DC voltage necessary for driving the LED group 6. The booster circuit unit 7 includes a coil 7 and a switching FET 12 inside, and obtains a boosted pulsed DC voltage by using an induced voltage generated in the coil 7 by the switching operation of the switching FET 12. As will be described later, the switching FET 12 is also used to control application of the generated DC voltage to the LED group 6. The other rectifier diode 9 and capacitor 10 are elements for generating a stable predetermined DC voltage. Note that the booster circuit unit 7 used here has the function of boosting the supplied voltage to generate a predetermined DC voltage and the function of controlling the application of the DC voltage, as shown in FIG. It is not limited to the mode shown in the above, and other modes may be used. For example, the booster circuit unit 15 shown in FIG. 2 may be used.

このように、ＬＥＤ群６等の各素子に直接印加されても破損することのない電圧値を有する電源１３を利用することで、昇圧回路部７により定電流駆動回路１の動作を可能としながら、内部に故障があっても、過大な電流が流れて各部が破損するような問題を回避することができる。例えば、昇圧回路部７が破損しても各素子が破損することはないし、スイッチングＦＥＴ５が破損してドレイン−ソース間が短絡してもＬＥＤ群６に電流が流れ続けるだけで、その電流値は後述するように抵抗４を利用して制御されるため、ＬＥＤ群６が破損することはない。また、抵抗４は、後述するように、ＬＥＤ群６へ印加する電圧を制御するために利用されるが、これについてもヒューズ等の素子を利用することで、その破損を容易に確認することができ、他の素子の破損や定電流駆動回路１の誤動作等に至ることはない。   In this way, by using the power supply 13 having a voltage value that does not break even when directly applied to each element such as the LED group 6, the booster circuit unit 7 can operate the constant current drive circuit 1. Even if there is a failure inside, it is possible to avoid a problem that an excessive current flows and each part is damaged. For example, even if the booster circuit unit 7 is damaged, each element is not damaged, and even if the switching FET 5 is damaged and the drain-source is short-circuited, the current continues to flow through the LED group 6, and the current value is As will be described later, since the resistor 4 is used for control, the LED group 6 is not damaged. As will be described later, the resistor 4 is used to control the voltage applied to the LED group 6, and this can also be easily confirmed by using an element such as a fuse. In other words, no damage to other elements or malfunction of the constant current drive circuit 1 will occur.

ＬＥＤ群６は、定電流駆動回路１が定電流での駆動を目的とする素子であれば、例えば、同色の複数個のＬＥＤを直列接続して利用する態様のほか、所定の割合で混合したＲＧＢ各色等のＬＥＤを複数個直列接続して利用する態様であっても構わない。また、ＬＥＤ群６として示しているが、ＬＥＤの個数を制限するものではなく、１個のＬＥＤのみを利用する態様であっても構わない。また、ＬＥＤ等の発光素子ではなく、他の素子を利用する態様であっても構わない。   If the constant current drive circuit 1 is an element intended for driving at a constant current, the LED group 6 is, for example, a mode in which a plurality of LEDs of the same color are connected in series and mixed at a predetermined ratio. A mode in which a plurality of LEDs of RGB colors or the like are connected in series may be used. Moreover, although shown as the LED group 6, it does not restrict | limit the number of LEDs and the aspect using only one LED may be sufficient. Moreover, you may be the aspect using other elements instead of light emitting elements, such as LED.

スイッチングＦＥＴ５は、ＰＷＭ部３からゲートに印加されるパルス電圧に従ってドレイン−ソース間の電流をパルス状に周期的にオン、オフ制御する機能を有する。具体的には、パルス電圧がオンのときはドレイン−ソース間のスイッチング動作をオンにし電流を流すことでＬＥＤ群６を点灯させ、パルス電圧がオフのときはスイッチング動作をオフとし電流を遮断することでＬＥＤ群６を消灯させるよう動作する。   The switching FET 5 has a function of periodically turning on and off the current between the drain and the source in a pulsed manner in accordance with the pulse voltage applied from the PWM unit 3 to the gate. Specifically, when the pulse voltage is on, the drain-source switching operation is turned on and a current is supplied to light the LED group 6, and when the pulse voltage is off, the switching operation is turned off and the current is cut off. Thus, the LED group 6 operates to be extinguished.

ＰＷＭ部３は、制御部２による制御に従ってパルス電圧を発生し、スイッチングＦＥＴ５にゲート電圧として印加する機能を有する。   The PWM unit 3 has a function of generating a pulse voltage according to control by the control unit 2 and applying the pulse voltage to the switching FET 5 as a gate voltage.

制御部２は、ＰＷＭ部３の発生するパルス電圧を制御する機能を有する。具体的には、ＰＷＭ部３の発生するパルス波形のデューティ比を制御する。この制御部２およびＰＷＭ部３が、ＰＷＭ制御手段を構成している。   The control unit 2 has a function of controlling the pulse voltage generated by the PWM unit 3. Specifically, the duty ratio of the pulse waveform generated by the PWM unit 3 is controlled. The control unit 2 and the PWM unit 3 constitute PWM control means.

上記の制御部２、ＰＷＭ部３およびスイッチングＦＥＴ５の動作によって、ＬＥＤ群６の点灯および消灯の動作と、発光時の輝度と、が制御される。具体的には、制御部２により制御されたデューティ比のパルス電圧がＰＷＭ部３で生成され、これがスイッチングＦＥＴ５のゲート電圧として印加されることで、ＬＥＤ群６のカソード側の接地がオン、オフ制御され、これに従ってＬＥＤ群６が点灯または消灯する。デューティ比が１００％であれば、ＬＥＤ群６は点灯し続け、デューティ比が０であればＬＥＤ群６は消灯し続ける。また、デューティ比を変更することで、ＬＥＤ群６の点灯時間と消灯時間の割合や回数を変更し、その結果、ＬＥＤ群６の輝度を制御することができる。   The operation of the control unit 2, the PWM unit 3, and the switching FET 5 controls the operation of turning on and off the LED group 6 and the luminance during light emission. Specifically, a pulse voltage having a duty ratio controlled by the control unit 2 is generated by the PWM unit 3 and applied as a gate voltage of the switching FET 5, thereby grounding the cathode side of the LED group 6 on and off. The LED group 6 is turned on or off according to this control. If the duty ratio is 100%, the LED group 6 continues to be lit, and if the duty ratio is 0, the LED group 6 continues to be turned off. Further, by changing the duty ratio, the ratio and the number of turn-on times and turn-off times of the LED group 6 can be changed, and as a result, the luminance of the LED group 6 can be controlled.

そして、定電流駆動回路１では、これに加えてさらに、制御部２およびＰＷＭ制御部３によりＬＥＤ群６が点灯している状態にあるときに、ＬＥＤ群６に流れる電流値を一定にするよう制御するために、抵抗４および定電圧制御部８が設けられている。   In addition, in the constant current drive circuit 1, in addition to this, when the LED group 6 is lit by the control unit 2 and the PWM control unit 3, the current value flowing through the LED group 6 is made constant. In order to control, the resistor 4 and the constant voltage control part 8 are provided.

抵抗４は、ＬＥＤ群６に流れる電流値の検出用に設けられたもので、抵抗４両端の電位差と、抵抗４の抵抗値、とから電流値を得ることができる。ただし、実際には、電流値に換算して利用するのではなく、抵抗４の両端の電位差をそのまま利用して、その電圧値の大小によって、ＬＥＤ群６に流れる電流値の大小を判断する。   The resistor 4 is provided for detecting the current value flowing through the LED group 6, and a current value can be obtained from the potential difference between both ends of the resistor 4 and the resistance value of the resistor 4. However, in actuality, it is not used by converting into a current value, but the potential difference between both ends of the resistor 4 is used as it is, and the magnitude of the current value flowing through the LED group 6 is determined based on the magnitude of the voltage value.

定電圧制御部（電圧制御手段）８は、上述の昇圧回路部７で電源電圧を昇圧したパルス状の直流電圧を得るためにスイッチングＦＥＴ１２のスイッチング動作を制御する機能と、抵抗４の両端の電位差からＬＥＤ群６に流れる電流値を検知し、その値が目標とする所定の電流値となるように、昇圧回路部７からＬＥＤ群６に印加する電圧を制御する機能を有する。その動作については、詳細を後述するが、ここでは定電圧制御部８を実現するための構成例を図３を用いて説明する。   The constant voltage control unit (voltage control means) 8 has a function of controlling the switching operation of the switching FET 12 in order to obtain a pulsed DC voltage obtained by boosting the power supply voltage by the boosting circuit unit 7 and a potential difference between both ends of the resistor 4. The voltage value applied to the LED group 6 from the booster circuit unit 7 is controlled so that the current value flowing from the LED group 6 to the LED group 6 is detected and the value becomes a target predetermined current value. Although details of the operation will be described later, a configuration example for realizing the constant voltage control unit 8 will be described with reference to FIG.

定電圧制御部８は、例えば、図３に示すように、抵抗４に接続される電流検出部１７と、電流検出部１７に接続される基準電圧発生部１６と、電流検出部１７，昇圧回路７内部のスイッチングＦＥＴ１２およびＰＷＭ部３に接続されるＦＥＴ駆動部１８と、ＦＥＴ駆動部１８に接続される同期信号発生部１９と、から構成することができる。   For example, as shown in FIG. 3, the constant voltage control unit 8 includes a current detection unit 17 connected to the resistor 4, a reference voltage generation unit 16 connected to the current detection unit 17, a current detection unit 17, and a booster circuit. 7 includes an FET driving unit 18 connected to the internal switching FET 12 and the PWM unit 3, and a synchronization signal generating unit 19 connected to the FET driving unit 18.

基準電圧発生部１６は、実際に抵抗４の両端に生じた電位差と比較するために利用する、定電流駆動回路１が目的とする所定の定電流でＬＥＤ群６を駆動するときに抵抗４の両端に生ずる電位差を、基準電圧として発生する機能を有する。基準電圧となる電圧値は、予め、所定の値に固定される態様であってもよいし、変更可能であって、利用するＬＥＤ群６等の素子に従って変更する態様であっても構わない。   The reference voltage generator 16 is used to compare with the potential difference actually generated at both ends of the resistor 4, and the constant current driving circuit 1 drives the LED group 6 with a predetermined constant current intended. It has a function of generating a potential difference generated at both ends as a reference voltage. The voltage value serving as the reference voltage may be fixed in advance to a predetermined value, or may be changed and may be changed according to an element such as the LED group 6 to be used.

電流検出部１７は、上述したように抵抗４の両端の電位差からＬＥＤ群６に流れる電流値を検知するための機能部である。実際には、電流値を直接検出するのではなく、抵抗４の両端の電位差を検出し、基準電圧発生部１６の発生する基準電圧と比較して、その比較結果から、ＬＥＤ群６を流れる電流値が定電流駆動回路１の目的とする所定の電流値よりも大きいか小さいかを判定する。そして、その判定結果をＦＥＴ駆動部１８に通知する機能を有する。   The current detection unit 17 is a functional unit for detecting the value of the current flowing through the LED group 6 from the potential difference between both ends of the resistor 4 as described above. Actually, the current value is not directly detected, but the potential difference between both ends of the resistor 4 is detected, compared with the reference voltage generated by the reference voltage generator 16, and the current flowing through the LED group 6 is determined based on the comparison result. It is determined whether the value is larger or smaller than a predetermined current value intended for the constant current drive circuit 1. The determination result is notified to the FET drive unit 18.

ＦＥＴ駆動部１８は、電流検出部１７から通知される判定結果と、ＰＷＭ部３から取得するスイッチングＦＥＴ５のスイッチング動作を制御するパルス電圧にかかる情報と、から、昇圧回路部７内のスイッチングＦＥＴ１２のスイッチング動作を制御する機能を有する。具体的には、ＰＷＭ部３が発生するパルス電圧に従って、昇圧回路部７の発生した電圧のＬＥＤ群６への印加の開始および停止を制御する。そして、さらに、実際にＬＥＤ群６に流れる電流値に係る情報を得て、これをＬＥＤ群６への電圧の印加制御にフィードバックすることで、ＬＥＤ群６へ印可する電圧値を制御する。その結果、ＬＥＤ群６に流れる電流値が制御されることとなる。   The FET drive unit 18 uses the determination result notified from the current detection unit 17 and the information on the pulse voltage for controlling the switching operation of the switching FET 5 acquired from the PWM unit 3, to determine the switching FET 12 in the boost circuit unit 7. It has a function of controlling the switching operation. Specifically, the start and stop of application of the voltage generated by the booster circuit unit 7 to the LED group 6 is controlled according to the pulse voltage generated by the PWM unit 3. Further, the voltage value applied to the LED group 6 is controlled by obtaining information related to the current value actually flowing in the LED group 6 and feeding back the information to the application control of the voltage to the LED group 6. As a result, the current value flowing through the LED group 6 is controlled.

同期信号発生部１９は、ＰＷＭ部３で発生されるスイッチングＦＥＴ５のスイッチング動作を制御するパルス電圧に比して十分に高周波なパルス波形を、同期信号として発生する機能を有する。この同期信号を利用して、ＦＥＴ駆動部１８が、スイッチングＦＥＴ１２のスイッチング動作を高速に制御することで、昇圧回路部７で昇圧したパルス状の直流電圧を発生すると共に、この直流電圧のＬＥＤ群６への印加を、制御部２がＬＥＤ群６の点灯および輝度を制御する動作に比して非常に高速に制御することが可能となる。   The synchronization signal generation unit 19 has a function of generating a pulse waveform having a sufficiently high frequency as a synchronization signal as compared with the pulse voltage for controlling the switching operation of the switching FET 5 generated by the PWM unit 3. Using this synchronization signal, the FET drive unit 18 controls the switching operation of the switching FET 12 at a high speed, thereby generating a pulsed DC voltage boosted by the booster circuit unit 7 and a group of LEDs having this DC voltage. 6 can be controlled at a very high speed as compared with the operation in which the control unit 2 controls the lighting and luminance of the LED group 6.

尚、後述の定電流駆動回路１の動作に係る説明においては、定電圧制御部８を一の制御部として説明するが、実際には、上述した各部の機能および動作によりその動作を実現している。   In the description relating to the operation of the constant current drive circuit 1 described later, the constant voltage control unit 8 will be described as one control unit. However, in practice, the operation is realized by the function and operation of each unit described above. Yes.

また、図１では、ＬＥＤ群６および昇圧回路部７のスイッチング動作に、スイッチングＦＥＴ５，１２を利用しているが、本発明はこれに限らず、ゲート電圧等の制御信号によって、電流のオン、オフを制御できる機能を有するものであれば、他の態様であっても構わない。例えば、図４に示すように、スイッチングＦＥＴ５，１２の代わりに、トランジスタ２０，２１を利用する態様であっても構わない。   In FIG. 1, the switching FETs 5 and 12 are used for the switching operation of the LED group 6 and the booster circuit unit 7, but the present invention is not limited thereto, and the current is turned on by a control signal such as a gate voltage. Other modes may be used as long as they have a function capable of controlling off. For example, as shown in FIG. 4, a mode in which transistors 20 and 21 are used instead of the switching FETs 5 and 12 may be used.

また、図１では、一の定電流駆動回路１を示しているが、実際には、例えば各色のＬＥＤを駆動するため、定電流駆動回路１を複数個動作させる場合も多い。このような場合、複数個の定電流駆動回路１をそれぞれ独立して動作させる態様の他、例えば、制御部２を共通にして、図１に示すその他の素子群１４が、制御部２と電源１３との間に並列となるように、図５に示すように接続した態様であっても構わない。   FIG. 1 shows one constant current drive circuit 1, but actually, in many cases, a plurality of constant current drive circuits 1 are operated in order to drive, for example, each color LED. In such a case, in addition to a mode in which the plurality of constant current driving circuits 1 are independently operated, for example, the control unit 2 is shared, and the other element group 14 shown in FIG. As shown in FIG. 5, it may be connected as shown in FIG.

次に、図１を参照しながら、定電流駆動回路１の動作について説明する。   Next, the operation of the constant current drive circuit 1 will be described with reference to FIG.

＜定電流駆動回路の動作＞
ＬＥＤ群６を所定の輝度で点灯させるため、制御部２が、ＰＷＭ部３から、図６（ａ）に示すようなパルス電圧を発生し、スイッチングＦＥＴ５を制御するものとする。図６（ａ）の上部に示したように、図６の横方向は時間を表し、図６（ａ）は、ＰＷＭ部３の発生するパルス電圧が、時刻ｔ0からｔ1まではオンの状態であり、ｔ1からｔ2まではオフの状態であることを示す。 <Operation of constant current drive circuit>
In order to light the LED group 6 with a predetermined luminance, the control unit 2 generates a pulse voltage as shown in FIG. 6A from the PWM unit 3 and controls the switching FET 5. As shown in the upper part of FIG. 6A, the horizontal direction of FIG. 6 represents time, and FIG. 6A shows that the pulse voltage generated by the PWM unit 3 is on from time t 0 to t 1 . a state, indicates that from t 1 to t 2 is in an off state.

理想的には、ＬＥＤ群６に流れる電流値が図６（ａ）と完全に同一の波形を示しながら、ＬＥＤ群６が点灯すればよい。しかし、従来の技術では、上述したように、回路内に残留する電荷の影響等によって、時刻ｔ0に０であった電流が徐々に上昇する電流波形のなまりが生じたり、時刻ｔ0で目標とする所定の電流値を大きく超えるインラッシュ電流が流れてしまうといった現象が起きることがあった。そのため、定電流駆動回路１では、制御部２、ＰＷＭ部３およびスイッチングＦＥＴ５によって、ＬＥＤ群６の点灯動作を図６（ａ）に示すように制御しながら、時刻ｔ0からｔ1に至るＬＥＤ群６の点灯している間のＬＥＤ群６に流れる電流値を、さらに細かく制御する。 Ideally, the LED group 6 may be lit while the value of the current flowing through the LED group 6 shows the same waveform as in FIG. However, in the conventional technique, as described above, due to the influence of the electric charge remaining in the circuit, the current waveform that gradually increases from 0 at time t 0 is gradually rounded, or at the time t 0 In some cases, an inrush current that greatly exceeds a predetermined current value flows. Therefore, in the constant current drive circuit 1, the LEDs from time t 0 to time t 1 are controlled while the lighting operation of the LED group 6 is controlled by the control unit 2, the PWM unit 3, and the switching FET 5 as shown in FIG. The current value flowing through the LED group 6 while the group 6 is lit is further controlled.

定電圧制御部８内では、図６（ｂ）に示すように、ＰＷＭ部３で発生する図６（ａ）のパルス波形に比べて十分に高周波なパルス波を発生している。そして、定電圧制御部８は、このパルス波形に基づいて昇圧回路部７内のスイッチングＦＥＴ１２のスイッチング動作を制御する。これにより、定電圧制御部８は、図６（ｂ）と同様の波形を示すパルス状の直流電圧を昇圧回路部７で発生させることが可能である。   In the constant voltage control unit 8, as shown in FIG. 6B, a sufficiently high-frequency pulse wave is generated as compared with the pulse waveform shown in FIG. 6A generated in the PWM unit 3. Then, the constant voltage control unit 8 controls the switching operation of the switching FET 12 in the booster circuit unit 7 based on this pulse waveform. Thereby, the constant voltage control unit 8 can generate a pulsed DC voltage having a waveform similar to that shown in FIG.

時刻ｔ0において、ＰＷＭ部３の発生する電圧のパルス波形がオンになると、これを受けた定電圧制御部８は、昇圧回路部７内部のスイッチングＦＥＴ１２を制御して、ＬＥＤ群６への直流電圧の印加を開始する。このとき印加される直流電圧は、電源部１３により供給された電圧を昇圧回路部７で昇圧したものである。このときの昇圧後の電圧値は、パルス状に周期的に印加することで、ＬＥＤ群６にかかる実際の電圧値を後述するように制御することができるため、目的とする所定の定電流で動作するときにＬＥＤ群６で必要となる電圧値よりも若干高い電圧値であっても構わない。 At time t 0 , when the pulse waveform of the voltage generated by the PWM unit 3 is turned on, the constant voltage control unit 8 that has received this controls the switching FET 12 in the booster circuit unit 7 to direct the LED to the LED group 6. Start applying voltage. The DC voltage applied at this time is obtained by boosting the voltage supplied from the power supply unit 13 by the boosting circuit unit 7. The voltage value after boosting at this time can be controlled as will be described later by applying the pulses periodically in the form of pulses, so that the voltage value at the target is a predetermined constant current. The voltage value may be slightly higher than the voltage value required for the LED group 6 when operating.

図６（ｃ）は、昇圧回路部７がＬＥＤ群６に印加する直流電圧を示している。このように、定電圧制御部８は、スイッチングＦＥＴ１２を制御して、図６（ｂ）と同様の波形を示すパルス状の昇圧後の直流電圧をＬＥＤ群６に印可する。   FIG. 6C shows the DC voltage applied to the LED group 6 by the booster circuit unit 7. As described above, the constant voltage control unit 8 controls the switching FET 12 to apply a pulsed boosted DC voltage having the same waveform as in FIG. 6B to the LED group 6.

定電圧制御部８は、ＬＥＤ群６に流れる電流値が定電流駆動回路１の目的とする電流値に一致したときに抵抗４の両端に生じる基準電圧Ｖ0と、抵抗４の両端で計測した実際の電位差と、を比較監視している。そのときの抵抗４の両端の電位差である電圧値の波形を図６（ｄ）に示している。図６（ｄ）に示すように、時刻ｔ0で電圧値がＶLであったものが、時間の経過に従って徐々に上昇し基準電圧Ｖ0に達すると、図６（ｃ）に示すように、定電圧制御部８は、スイッチングＦＥＴ１２を制御して昇圧回路部７からのＬＥＤ群６への電圧の印加を停止する。しかし、実際には各素子の時間的な動作限界等の影響から、電圧値がＶ0に達した瞬間ではなく、ｔ0から時間ａだけ経過した時刻ｔaに、電圧値がＶ0を超えてＶUに達して電圧値の上昇が停止する。そして、ここから電圧値が徐々に低下し、電圧値が基準電圧Ｖ0に達すると、図６（ｃ）に示すように、定電圧制御部８は、再びスイッチングＦＥＴ１２を制御して昇圧回路部７からＬＥＤ群６への電圧の印加を開始する。このときも同様に、図６（ｄ）に示すように、時刻ｔaから時間ｂだけ経過した時刻ｔbに電圧値Ｖ0より低いＶLに達した後、再び電圧値が上昇し始める。ただし、実際の各素子の動作は非常に高速であるため、電圧印加を開始または停止する時刻と、電圧値がＶLまたはＶUに達する時刻との時間差は非常に小さいものであるし、基準電圧Ｖ0と電圧値ＶUまたはＶLの電位差も非常に小さく、実用上問題となることはない。 The constant voltage control unit 8 measures the reference voltage V 0 generated at both ends of the resistor 4 and the both ends of the resistor 4 when the current value flowing through the LED group 6 matches the target current value of the constant current driving circuit 1. The actual potential difference is compared and monitored. A waveform of a voltage value which is a potential difference between both ends of the resistor 4 at that time is shown in FIG. As shown in FIG. 6D, when the voltage value is V L at time t 0 and gradually rises as time passes and reaches the reference voltage V 0 , as shown in FIG. 6C. The constant voltage control unit 8 controls the switching FET 12 to stop the application of voltage from the booster circuit unit 7 to the LED group 6. However, in actuality, the voltage value exceeds V 0 not at the moment when the voltage value reaches V 0 but at time ta when time a has elapsed from t 0 due to the influence of the temporal operation limit of each element. Then, the voltage value rises when V U is reached. When the voltage value gradually decreases from this point and reaches the reference voltage V 0 , as shown in FIG. 6C, the constant voltage control unit 8 controls the switching FET 12 again to boost the boost circuit unit. Application of a voltage from 7 to the LED group 6 is started. Similarly this time, as shown in FIG. 6 (d), after reaching the lower V L than the voltage value V 0 to the time t b from the time t a has passed by time b, again the voltage value starts to increase. However, since the actual operation of each element is very fast, the time difference between the time when the voltage application is started or stopped and the time when the voltage value reaches V L or V U is very small. The potential difference between the voltage V 0 and the voltage value V U or V L is also very small and does not cause a problem in practice.

このように、定電圧制御部８は、昇圧回路部７で昇圧した直流電圧を、図６（ｂ）に示す非常に高い周波数でパルス状に周期的に印加する。そして、さらにその印加の開始および停止を図６（ｃ）に示すように制御することで、ＬＥＤ群６へ印加する電圧値を制御し、その結果、ＬＥＤ群６へ流れる電流値を制御しているのである。   As described above, the constant voltage control unit 8 periodically applies the DC voltage boosted by the boosting circuit unit 7 in a pulse shape at a very high frequency shown in FIG. Further, by controlling the start and stop of the application as shown in FIG. 6C, the voltage value applied to the LED group 6 is controlled, and as a result, the current value flowing to the LED group 6 is controlled. It is.

図６（ａ）の時刻ｔ1で、パルス電圧に従ってＬＥＤ群６が消灯されたとき、上述の抵抗４の両端に生ずる電位差情報のみでは、電圧値の低下に伴い、定電圧制御部８が、ＬＥＤ群６への印加電圧値を上昇させようとする。しかし、定電圧制御部８には、ＰＷＭ部３が発生する図６（ａ）に示すパルス波形に係る情報も入力されているため、このような現象を回避し、図６（ｃ）に示すように、ＰＷＭ部３からのパルス波形が次に時刻ｔ2でオンになるまでの時間ｃの間は、昇圧回路部７からのＬＥＤ群６への電圧の印加は停止される。そして、時刻ｔ2に至った瞬間から、上述と同様の電圧の制御を開始する。 When the LED group 6 is turned off according to the pulse voltage at time t 1 in FIG. 6A, only the potential difference information generated at both ends of the resistor 4 described above causes the constant voltage control unit 8 to An attempt is made to increase the voltage applied to the LED group 6. However, since information related to the pulse waveform shown in FIG. 6A generated by the PWM unit 3 is also input to the constant voltage control unit 8, such a phenomenon is avoided and shown in FIG. 6C. As described above, during the time period c until the pulse waveform from the PWM unit 3 is turned on next time t 2 , the voltage application from the booster circuit unit 7 to the LED group 6 is stopped. Then, the voltage control similar to that described above is started from the moment when time t 2 is reached.

このように、抵抗４の両端に生ずる電位差を監視しながら、ＬＥＤ群６に印加する電圧値を詳細に制御することで、ＬＥＤ群６に流れる電流値は、図６（ｅ）のような波形を示す。図６（ｄ）に示したように、抵抗４の両端の電位差が上限となる電圧値ＶUと下限となる電圧値ＶLの間を変動するため、ＬＥＤ群６に流れる電流値も、これに従ってＶUに対応する電流値とＶLに対応する電流値との間を変動することとなる。しかし、上述したように実際にはその変動幅は小さく、ＬＥＤ群６の輝度が変化するほどのものではないため、その動作に影響はない。よって、定電流駆動回路１は、上述の動作により、ＬＥＤ群６を、所定の電流が流れたときの輝度で点灯させることができる。 As described above, the voltage value applied to the LED group 6 is controlled in detail while monitoring the potential difference generated at both ends of the resistor 4, so that the current value flowing through the LED group 6 has a waveform as shown in FIG. Indicates. As shown in FIG. 6D, since the potential difference between both ends of the resistor 4 varies between the upper limit voltage value V U and the lower limit voltage value V L , the current value flowing through the LED group 6 is also Accordingly, the current value corresponding to V U and the current value corresponding to V L vary. However, as described above, the fluctuation range is actually small and is not so large that the luminance of the LED group 6 changes, so that the operation is not affected. Therefore, the constant current drive circuit 1 can light the LED group 6 with the brightness when a predetermined current flows by the above-described operation.

ＰＷＭ部３の発生するパルス波形に従って、パルス波形がオフのときには、定電圧制御部８および昇圧回路部７は動作を停止し、ＬＥＤ群６および抵抗４を流れる電流値は完全に０となる。このとき、昇圧回路部７では、昇圧したパルス状の直流電圧を発生し続けていたとしても、ＬＥＤ群６の点灯を開始した瞬間に、ＬＥＤ群６に流れる電流値に対応する抵抗４両端の電位差を監視しながら印可する直流電圧を上述のように制御するため、従来問題となっていたインラッシュ電流の発生といった問題を回避することができる。   According to the pulse waveform generated by the PWM unit 3, when the pulse waveform is off, the constant voltage control unit 8 and the booster circuit unit 7 stop operating, and the current value flowing through the LED group 6 and the resistor 4 becomes completely zero. At this time, even if the boosting circuit unit 7 continues to generate a boosted pulsed DC voltage, at the moment when the lighting of the LED group 6 is started, both ends of the resistor 4 corresponding to the current value flowing through the LED group 6 are detected. Since the DC voltage to be applied is controlled as described above while monitoring the potential difference, it is possible to avoid a problem such as generation of an inrush current which has been a problem in the past.

ＬＥＤ群６に印可する電圧は、上述したように高い周波数でパルス状に印加しながら制御しているため、昇圧回路部７において、ＬＥＤ群６に所定の電流値が得られるときに必要となる所定の電圧値よりも若干高い電圧値を有する直流電圧を発生し、これを利用することが可能である。この所定の電圧値よりも高い電圧値を有する直流電圧を、上述したように制御しながらＬＥＤ群６に印加することで、ＬＥＤ群６を点灯した直後からＬＥＤ群６を目的の輝度で点灯させるのに十分な電流を得ることが可能である。   Since the voltage applied to the LED group 6 is controlled while being applied in pulses at a high frequency as described above, it is necessary when a predetermined current value is obtained in the LED group 6 in the booster circuit unit 7. A DC voltage having a voltage value slightly higher than a predetermined voltage value can be generated and used. By applying a DC voltage having a voltage value higher than the predetermined voltage value to the LED group 6 while controlling as described above, the LED group 6 is turned on at a target luminance immediately after the LED group 6 is turned on. It is possible to obtain a sufficient current.

あるいは、ＬＥＤ群６が消灯している間も昇圧回路部７において昇圧したパルス状の直流電圧を発生しておけば、ＬＥＤ群６を点灯した直後からＬＥＤ群６を目的の輝度で点灯させるのに十分な電流を得ることができ、上述したようにインラッシュ電流の発生を回避することもできる。   Alternatively, if a boosted DC voltage is generated in the booster circuit section 7 while the LED group 6 is turned off, the LED group 6 is turned on at a desired luminance immediately after the LED group 6 is turned on. Sufficient current can be obtained, and generation of inrush current can be avoided as described above.

また、定電圧制御部８は、ＬＥＤ群６の電流値を検知するために設けられた抵抗値４の両端の電位差を検出し利用しているが、この抵抗４は接地されているため、ここに電荷が残留して検出する電位差が影響を受けることもない。そのため、制御部２およびＰＷＭ部３によってＬＥＤ群６が点灯されると、定電圧制御部８は、ＬＥＤ群６に流れる電流値に対応する抵抗４の両端に生ずる電圧値を、瞬時にかつ正確に得ることができる。   Further, the constant voltage control unit 8 detects and uses the potential difference between both ends of the resistance value 4 provided to detect the current value of the LED group 6, but this resistance 4 is grounded. Therefore, the potential difference detected by the remaining charge is not affected. Therefore, when the LED group 6 is turned on by the control unit 2 and the PWM unit 3, the constant voltage control unit 8 instantaneously and accurately determines the voltage value generated at both ends of the resistor 4 corresponding to the current value flowing through the LED group 6. Can get to.

これらにより、ＬＥＤ群６を消灯した状態から点灯させた場合にも、図６（ａ）に示すＰＷＭ部３の発生するパルス波形の立ち上がりに準じて、ＬＥＤ群６の電流値も図６（ｅ）に示すように急峻な立ち上がりを示し、従来のように、徐々に上昇して目的の電流値に達する電流波形のなまりといった現象を回避することができる。   As a result, even when the LED group 6 is turned on from the extinguished state, the current value of the LED group 6 is also in accordance with the rise of the pulse waveform generated by the PWM unit 3 shown in FIG. ), A steep rise is exhibited, and a phenomenon such as a curling of a current waveform that gradually increases and reaches a target current value as in the prior art can be avoided.

さらに、ＬＥＤ群６に流れる電流値に対応する情報を抵抗４の両端の電位差から得て利用しているため、ＬＥＤ群６の順方向降下電圧値等のＬＥＤ群６に固有の値に基づいて調整用抵抗を設けるといった作業を必要としない。また、ＬＥＤ群６を含む各素子の周囲温度の変化や、経時変化にも、特別な調整をすることなく対応することが可能である。   Further, since information corresponding to the value of the current flowing through the LED group 6 is obtained from the potential difference between both ends of the resistor 4, the information is based on values unique to the LED group 6 such as the forward voltage drop value of the LED group 6. There is no need to provide adjustment resistors. In addition, it is possible to cope with changes in ambient temperature of each element including the LED group 6 and changes with time without special adjustment.

さらにまた、上述の態様によれば、ＬＥＤを直列接続してＬＥＤ群６として利用できる数が制限されることがなく、図５に示すように、定電流駆動回路１を並列接続して利用したり、図３に示す定電圧制御部８内の基準電圧発生部１６の値を調節することで各定電流駆動回路１毎にＬＥＤの輝度を変更することも可能であり、ＬＥＤ等の素子を様々な態様で利用する装置を実現することが可能である。   Furthermore, according to the above-described aspect, the number of LEDs that can be connected in series and used as the LED group 6 is not limited, and the constant current drive circuit 1 is connected in parallel and used as shown in FIG. Or by adjusting the value of the reference voltage generator 16 in the constant voltage controller 8 shown in FIG. 3, it is possible to change the brightness of the LED for each constant current drive circuit 1. It is possible to realize an apparatus used in various modes.

この発明の一の実施の形態に係る定電流駆動回路の構成を示す図である。It is a figure which shows the structure of the constant current drive circuit which concerns on one embodiment of this invention. この発明の一の実施の形態に係る昇圧回路部の別の構成を示す図である。It is a figure which shows another structure of the booster circuit part which concerns on one embodiment of this invention. この発明の一の実施の形態に係る定電圧制御部の構成例を示す図ある。It is a figure which shows the structural example of the constant voltage control part which concerns on one embodiment of this invention. この発明の一の実施の形態に係る定電流駆動回路をトランジスタを利用して実現したときの構成を示す図である。It is a figure which shows a structure when the constant current drive circuit which concerns on one embodiment of this invention is implement | achieved using the transistor. この発明の一の実施の形態に係る定電流駆動回路を並列接続して利用するときの構成を示す図である。It is a figure which shows a structure when using the constant current drive circuit which concerns on one embodiment of this invention connected in parallel. この発明の一の実施の形態に係る定電流駆動回路の動作を説明する図である。It is a figure explaining operation | movement of the constant current drive circuit which concerns on one embodiment of this invention.

符号の説明Explanation of symbols

１ 定電流駆動回路、２ 制御部、３ ＰＷＭ部、４ 抵抗、５,１２ スイッチングＦＥＴ、６ ＬＥＤ群、７,１５ 昇圧回路部、８ 定電圧制御部、９ 整流ダイオード
、１０ コンデンサ、１１ コイル、１３ 電源。
DESCRIPTION OF SYMBOLS 1 Constant current drive circuit, 2 Control part, 3 PWM part, 4 resistance, 5,12 switching FET, 6 LED group, 7,15 Boosting circuit part, 8 Constant voltage control part, 9 Rectifier diode, 10 Capacitor, 11 Coil, 13 Power supply.

Claims (5)

素子を所定の電流値で駆動するための定電流駆動回路であって、
供給される電源電圧から前記素子に印加するパルス状の電圧を発生する電圧発生手段と、
前記パルス状の電圧を印加したときに前記素子に流れる電流値を検出する電流検出手段と、
前記電流検出手段の検出した電流値に従って、前記電圧供給手段の前記素子への断続的な電圧印加の開始および停止を制御する電圧制御手段と、
を備えることを特徴とする定電流駆動回路。 A constant current drive circuit for driving an element with a predetermined current value,
Voltage generating means for generating a pulsed voltage to be applied to the element from a supplied power supply voltage;
Current detecting means for detecting a current value flowing through the element when the pulsed voltage is applied;
Voltage control means for controlling start and stop of intermittent voltage application to the element of the voltage supply means according to the current value detected by the current detection means;
A constant current drive circuit comprising: 請求項１に記載の定電流駆動回路であって、さらに、
前記素子の動作をパルス状に周期的にオンオフ制御するＰＷＭ制御手段、
を備え、
前記電圧制御手段は、
前記ＰＷＭ制御手段が前記素子の動作をオンオフする周期に従って、前記電圧供給手段の前記素子への断続的な電圧印加の開始および停止を制御する手段、
を含むことを特徴とする定電流駆動回路。 The constant current drive circuit according to claim 1, further comprising:
PWM control means for periodically turning on and off the operation of the element in a pulsed manner;
With
The voltage control means includes
Means for controlling the start and stop of intermittent voltage application to the element of the voltage supply means in accordance with a period in which the PWM control means turns on and off the operation of the element;
A constant current drive circuit comprising: 請求項１または請求項２に記載の定電流駆動回路であって、
前記電圧供給手段が前記素子へ印加するパルス状の電圧の周波数は、前記ＰＷＭ制御手段が前記素子の動作をオンオフする周波数に比べて高周波数であることを特徴とする定電流駆動回路。 A constant current driving circuit according to claim 1 or 2, wherein
The constant current drive circuit according to claim 1, wherein the frequency of the pulse voltage applied to the element by the voltage supply means is higher than the frequency at which the PWM control means turns on and off the operation of the element. 請求項１ないし請求項３のいずれかに記載の定電流駆動回路であって、
前記電源電圧の電圧値は、前記素子に印加したときに前記素子が破損する電圧値よりも低いことを特徴とする定電流駆動回路。 A constant current drive circuit according to any one of claims 1 to 3,
The constant current drive circuit according to claim 1, wherein a voltage value of the power supply voltage is lower than a voltage value at which the element is damaged when applied to the element. 請求項１ないし請求項４のいずれかに記載の定電流駆動回路であって、
前記素子は発光素子であることを特徴とする定電流駆動回路。
A constant current drive circuit according to any one of claims 1 to 4,
The constant current driving circuit, wherein the element is a light emitting element.
JP2004225541A 2004-08-02 2004-08-02 Constant current drive circuit Expired - Fee Related JP4642406B2 (en)

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007005450A (en) * 2005-06-22 2007-01-11 Fdk Corp Light-emitting diode dimming circuit and lighting device
JP2008042148A (en) * 2006-08-10 2008-02-21 Hayashi Kagaku Kogyo Kk Light emitting device
JP2008140884A (en) * 2006-11-30 2008-06-19 Seiko Instruments Inc Led driving circuit
JP2008283033A (en) * 2007-05-11 2008-11-20 Ricoh Co Ltd Drive circuit, and electronic equipment having the drive circuit
US7456584B2 (en) 2006-03-15 2008-11-25 Casio Computer Co., Ltd. Light emitting element driving apparatus, method of driving a light emitting element and computer readable recording medium
WO2009094379A1 (en) * 2008-01-25 2009-07-30 Eveready Battery Company, Inc. Lighting device having boost circuitry
JP2009541988A (en) * 2006-06-22 2009-11-26 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Drive circuit that drives a load using pulse current
US7755297B2 (en) 2006-06-28 2010-07-13 Samsung Electronics Co., Ltd. Display apparatus and control method thereof
KR101243144B1 (en) * 2006-04-28 2013-03-13 엘지이노텍 주식회사 driving circuit of LED driver for LCD panel
JPWO2011055533A1 (en) * 2009-11-04 2013-03-28 ローム株式会社 Driving circuit and driving method for backlight LED string, and backlight and display device using the same
KR101563208B1 (en) 2009-02-04 2015-10-28 삼성디스플레이 주식회사 Apparatus for driving a light source and light source apparatus having the same

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004057921A1 (en) * 2002-12-19 2004-07-08 Koninklijke Philips Electronics N.V. Supply assembly for a led lighting module

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004057921A1 (en) * 2002-12-19 2004-07-08 Koninklijke Philips Electronics N.V. Supply assembly for a led lighting module

Cited By (13)

* Cited by examiner, † Cited by third party
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JP2007005450A (en) * 2005-06-22 2007-01-11 Fdk Corp Light-emitting diode dimming circuit and lighting device
US7456584B2 (en) 2006-03-15 2008-11-25 Casio Computer Co., Ltd. Light emitting element driving apparatus, method of driving a light emitting element and computer readable recording medium
KR101243144B1 (en) * 2006-04-28 2013-03-13 엘지이노텍 주식회사 driving circuit of LED driver for LCD panel
JP2009541988A (en) * 2006-06-22 2009-11-26 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Drive circuit that drives a load using pulse current
US7755297B2 (en) 2006-06-28 2010-07-13 Samsung Electronics Co., Ltd. Display apparatus and control method thereof
US7777421B2 (en) 2006-08-10 2010-08-17 Kazuharu Mishimagi Light emitting device
JP2008042148A (en) * 2006-08-10 2008-02-21 Hayashi Kagaku Kogyo Kk Light emitting device
JP2008140884A (en) * 2006-11-30 2008-06-19 Seiko Instruments Inc Led driving circuit
JP2008283033A (en) * 2007-05-11 2008-11-20 Ricoh Co Ltd Drive circuit, and electronic equipment having the drive circuit
WO2009094379A1 (en) * 2008-01-25 2009-07-30 Eveready Battery Company, Inc. Lighting device having boost circuitry
US9101022B2 (en) 2008-01-25 2015-08-04 Eveready Battery Company, Inc. Lighting device having boost circuitry
KR101563208B1 (en) 2009-02-04 2015-10-28 삼성디스플레이 주식회사 Apparatus for driving a light source and light source apparatus having the same
JPWO2011055533A1 (en) * 2009-11-04 2013-03-28 ローム株式会社 Driving circuit and driving method for backlight LED string, and backlight and display device using the same

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