JP6511322B2 - LED drive circuit - Google Patents

LED drive circuit Download PDF

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JP6511322B2
JP6511322B2 JP2015082675A JP2015082675A JP6511322B2 JP 6511322 B2 JP6511322 B2 JP 6511322B2 JP 2015082675 A JP2015082675 A JP 2015082675A JP 2015082675 A JP2015082675 A JP 2015082675A JP 6511322 B2 JP6511322 B2 JP 6511322B2
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led
led circuit
drive circuit
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JP2016201514A (en
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藤原　宗
宗 藤原
堅次 武渕
堅次 武渕
王義 山崎
王義 山崎
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New Japan Radio Co Ltd
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本発明はＬＥＤを駆動するＬＥＤ駆動回路に係り、特に、発光色が異なり異なる電流が流れる複数のＬＥＤを駆動する際に、各ＬＥＤが要求する電流を正確に供給しつつ低消費電流化を実現したＬＥＤ駆動回路に関する。
The present invention relates to an LED drive circuit for driving an LED, and in particular, when driving a plurality of LEDs having different emission colors and different currents flowing, the current consumption required is realized while accurately supplying the current required by each LED. It relates to the LED drive circuitry.

図３に従来のＬＥＤ駆動回路を示す。１１は複数個のＬＥＤを直列接続した第１ＬＥＤ回路、１２は第１ＬＥＤ回路１１とは異なる発光色の複数個のＬＥＤを直列接続した第２ＬＥＤ回路、１３は両ＬＥＤ回路１１，１２を駆動する駆動回路である。特許文献１の図４にはＬＥＤの直列回路を複数並列接続した構成が記載されている。   FIG. 3 shows a conventional LED drive circuit. 11 is a first LED circuit in which a plurality of LEDs are connected in series, 12 is a second LED circuit in which a plurality of LEDs of different emission colors are connected in series with the first LED circuit 11, and 13 is a drive for driving both LED circuits 11 and 12 It is a circuit. FIG. 4 of Patent Document 1 describes a configuration in which a plurality of LED series circuits are connected in parallel.

図４に別の従来のＬＥＤ駆動回路を示す。２１は複数個のＬＥＤを直列接続した第１ＬＥＤ回路、２２はＬＥＤ回路２１とは異なる発光色の複数個のＬＥＤを直列接続した第２ＬＥＤ回路、２３は両ＬＥＤ回路２１，２２を駆動する駆動回路、Ｓ１〜Ｓ３はスイッチである。   FIG. 4 shows another conventional LED drive circuit. 21 is a first LED circuit in which a plurality of LEDs are connected in series, 22 is a second LED circuit in which a plurality of LEDs of different emission colors are connected in series with each other, and 23 is a drive circuit for driving both LED circuits 21 and 22 , S1 to S3 are switches.

図４のＬＥＤ駆動回路では、入力電圧ＶＩＮが低いときは、スイッチＳ１，Ｓ２をＯＮさせスイッチＳ３をＯＦＦさせることで、第１ＬＥＤ回路２１と第２ＬＥＤ回路２２を並列接続して、各ＬＥＤに必要な順方向電圧を印加することができる。また、入力電圧ＶＩＮが高いときは、スイッチＳ１，Ｓ２をＯＦＦさせスイッチＳ３をＯＮさせることで、第１ＬＥＤ回路２１と第２ＬＥＤ回路２２を直列接続して、各ＬＥＤに必要な順方向電圧を印加しながら、第１ＬＥＤ回路２１と第２ＬＥＤ回路２２に共通の電流を流して消費電流を小さくすることができる。   In the LED drive circuit of FIG. 4, when the input voltage VIN is low, the switches S1 and S2 are turned on and the switch S3 is turned off, thereby connecting the first LED circuit 21 and the second LED circuit 22 in parallel and necessary for each LED Forward voltage can be applied. When the input voltage VIN is high, the switches S1 and S2 are turned off and the switch S3 is turned on to connect the first LED circuit 21 and the second LED circuit 22 in series and apply a forward voltage necessary for each LED At the same time, a current common to the first LED circuit 21 and the second LED circuit 22 can be supplied to reduce the current consumption.

特開２００９−２５２９３９号公報JP, 2009-252939, A

しかし、図３の従来例のＬＥＤ駆動回路では、第１ＬＥＤ回路１１に流れる電流と第２ＬＥＤ回路１２に流れる電流が、駆動回路１３の回路バラツキの影響を受ける問題がある。また、第１ＬＥＤ回路１１と第２ＬＥＤ回路１２に個々に電流を流す必要があるので、消費電流の低減を図ることが困難である。   However, in the LED drive circuit of the conventional example of FIG. 3, there is a problem that the current flowing through the first LED circuit 11 and the current flowing through the second LED circuit 12 are affected by the circuit variation of the drive circuit 13. In addition, it is difficult to reduce the consumption current because it is necessary to flow current individually to the first LED circuit 11 and the second LED circuit 12.

また、図４に示すＬＥＤ駆動回路では、第１ＬＥＤ回路２１と第２ＬＥＤ回路２２を並列接続した際は図３のＬＥＤ駆動回路と同様の問題がある。また、直列接続した際には、それら第１ＬＥＤ回路２１と第２ＬＥＤ回路２２に要求される電流の値が異なるときは、一方のＬＥＤ回路については、その電流を要求される値に一致させることはできるが、他方のＬＥＤ回路については、その電流を要求される電流に一致させることができず、所定の輝度を得ることができない問題があった。   Further, in the LED drive circuit shown in FIG. 4, when the first LED circuit 21 and the second LED circuit 22 are connected in parallel, there is a problem similar to that of the LED drive circuit of FIG. 3. In addition, when the series connection is performed, when the values of the currents required for the first LED circuit 21 and the second LED circuit 22 are different, for one of the LED circuits, the current may be made to match the required value. Although it is possible for the other LED circuit, there is a problem that the current can not be matched with the required current, and a predetermined luminance can not be obtained.

本発明の目的は、消費電流の低減を図り、且つ発光色の異なるそれぞれのＬＥＤに対して要求される電流を正確に供給し、それぞれのＬＥＤについて最適な輝度を実現できるようにしたＬＥＤ駆動回路を提供することである。   It is an object of the present invention to provide an LED drive circuit which reduces current consumption and accurately supplies the current required for each LED of different light emission colors so as to realize optimum brightness for each LED. To provide.

上記目的を達成するため、請求項１にかかる発明のＬＥＤ駆動回路は、第１ＬＥＤ回路と第２ＬＥＤ回路の直列回路の該第２ＬＥＤ回路の側に駆動回路を直列接続した回路を第１電源端子と第２電源端子の間に接続し、前記第２ＬＥＤ回路に要求される電流を前記駆動回路により設定し、前記第１ＬＥＤ回路に要求される電流と前記第２ＬＥＤ回路に要求される電流の差分に基づき、前記第１ＬＥＤ回路と前記第２ＬＥＤ回路の共通接続のノードに正又は負の電流を供給するＬＥＤ駆動回路において、前記第１ＬＥＤ回路に流れる電流を検知する第１電流検知回路と、前記第２ＬＥＤ回路に流れる電流を検知する第２電流検知回路と、前記第１電流検知回路で検知された電流と前記第２電流検知回路で検知された電流を比較する電流比較回路と、該電流比較回路で得られた比較結果に基づき前記ノードに電流を吐き出し又は前記ノードから電流を吸い込む電流増減回路と、を設けたことを特徴とする。
In order to achieve the above object, the LED drive circuit of the invention according to claim 1 comprises a first power supply terminal and a circuit in which a drive circuit is connected in series on the second LED circuit side of a series circuit of a first LED circuit and a second LED circuit. Connected between the second power supply terminals, the current required for the second LED circuit is set by the drive circuit, and the difference between the current required for the first LED circuit and the current required for the second LED circuit is set. A first current detection circuit for detecting a current flowing through the first LED circuit in an LED drive circuit for supplying a positive or negative current to a node of common connection between the first LED circuit and the second LED circuit, and the second LED circuit Current detection circuit that detects the current flowing in the current detection circuit, and a current comparison circuit that compares the current detected by the first current detection circuit with the current detected by the second current detection circuit , Characterized by comprising a current adjusting circuit for drawing a current from the node source current or the node based on the comparison result obtained in said current comparator circuit.

請求項２にかかる発明は、第１ＬＥＤ回路と第２ＬＥＤ回路の直列回路の該第２ＬＥＤ回路の側に駆動回路を直列接続した回路を第１電源端子と第２電源端子の間に接続し、前記第２ＬＥＤ回路に要求される電流を示す第２基準値に基づき前記駆動回路の電流を設定し、前記第１ＬＥＤ回路に要求される電流を示す第１基準値に基づき前記第１ＬＥＤ回路と前記第２ＬＥＤ回路の共通接続のノードに正又は負の電流を供給するＬＥＤ駆動回路において、前記第１ＬＥＤ回路に流れる電流を検知する第１電流検知回路と、前記第２ＬＥＤ回路に流れる電流を検知する第２電流検知回路と、前記第１電流検知回路で検知された電流を前記第１基準値と比較する第１電流比較回路と、該第１電流比較回路の比較結果に基づき前記ノードに電流を吐き出し又は前記ノードから電流を吸い込む電流増減回路と、前記第２電流検知回路で検知された電流を前記第２基準値と比較する第２電流比較回路とを備え、前記駆動回路は前記第２電流比較回路の比較結果に基づき駆動電流が制御されることを特徴とする。
In the invention according to claim 2, a circuit in which a drive circuit is connected in series on the side of the second LED circuit of the series circuit of the first LED circuit and the second LED circuit is connected between the first power supply terminal and the second power supply terminal, The current of the drive circuit is set based on a second reference value indicating the current required for the second LED circuit, and the first LED circuit and the second LED are based on the first reference value indicating the current required for the first LED circuit. In an LED drive circuit for supplying a positive or negative current to a node of a common connection of circuits, a first current detection circuit for detecting a current flowing in the first LED circuit, and a second current for detecting a current flowing in the second LED circuit A detection circuit, a first current comparison circuit comparing a current detected by the first current detection circuit with the first reference value, and a current discharge to the node based on a comparison result of the first current comparison circuit Or a current increase / decrease circuit for drawing current from the node, and a second current comparison circuit for comparing the current detected by the second current detection circuit with the second reference value, and the drive circuit includes the second current The drive current is controlled based on the comparison result of the comparison circuit .

本発明によれば、第１ＬＥＤ回路と第２ＬＥＤ回路を直列接続し、しかも第１ＬＥＤ回路と第２ＬＥＤ回路にそれぞれ要求される異なる正確な電流を流すことができるので、第１ＬＥＤ回路のＬＥＤと第２ＬＥＤ回路のＬＥＤについて、それぞれ最適な輝度を実現しながら、消費電流の削減を達成することができる。   According to the present invention, since the first LED circuit and the second LED circuit can be connected in series and different accurate currents respectively required for the first LED circuit and the second LED circuit can be supplied, the LEDs and the second LED of the first LED circuit can be provided. A reduction in current consumption can be achieved while achieving optimum brightness for each of the circuit's LEDs.

本発明の第１の実施例のＬＥＤ駆動回路のブロック図である。It is a block diagram of the LED drive circuit of the 1st Example of this invention. 本発明の第２の実施例のＬＥＤ駆動回路のブロック図である。It is a block diagram of the LED drive circuit of the 2nd Example of this invention. 従来のＬＥＤ駆動回路のブロック図である。It is a block diagram of the conventional LED drive circuit. 従来の別のＬＥＤ駆動回路のブロック図である。It is a block diagram of another conventional LED drive circuit.

＜第１の実施例＞
図１に本発明の実施例のＬＥＤ駆動回路を示す。１は複数個のＬＥＤを直列接続した第１ＬＥＤ回路、２は第１ＬＥＤ回路１とは異なる発光色の複数個のＬＥＤを直列接続した第２ＬＥＤ回路、３は両ＬＥＤ回路１，２を駆動する駆動回路である。この駆動回路３には両ＬＥＤ回路１，２を調光するＰＷＭ信号が入力される。ＶＩＮは入力電圧（電源端子）、ＧＮＤは接地（電源端子）である。なお、駆動回路３にＰＷＭ信号を入力する代わりに、駆動回路３を常時オンさせておき、ＰＷＭノイズの低減を図る構成としても良い。 First Embodiment
FIG. 1 shows an LED drive circuit according to an embodiment of the present invention. 1 is a first LED circuit in which a plurality of LEDs are connected in series, 2 is a second LED circuit in which a plurality of LEDs of different emission colors are connected in series with the first LED circuit 1, 3 is a drive for driving both LED circuits 1 and 2 It is a circuit. A PWM signal for dimming both LED circuits 1 and 2 is input to the drive circuit 3. VIN is an input voltage (power supply terminal), GND is a ground (power supply terminal). Here, instead of inputting the PWM signal to the drive circuit 3, the drive circuit 3 may be always turned on to reduce PWM noise.

４は第１ＬＥＤ回路１に流れる電流Ｉ１を検知する第１電流検知回路、５は第２ＬＥＤ回路２に流れる電流Ｉ２を検知する第２電流検知回路、６は第１電流検知回路４で検知された電流Ｉ１と第２電流検知回路５で検知された電流Ｉ２との差分に応じた制御信号を出力する電流比較回路である。   A first current detection circuit 4 detects a current I1 flowing through the first LED circuit 1, a second current detection circuit 5 detects a current I2 flowing through the second LED circuit 2, and a second current detection circuit 6 detects the first current detection circuit 4. This current comparison circuit outputs a control signal according to the difference between the current I1 and the current I2 detected by the second current detection circuit 5.

７は電流増減回路であり、電流比較回路６から出力する制御信号に基づいて、第１電流検知回路４と第２電流検知回路の共通接続点のノードＮ１からの吸込電流Ｉ３あるいはノードＮ１への吐出電流Ｉ４の値を調整する。   Reference numeral 7 denotes a current increasing / decreasing circuit, which receives a suction current I3 from the node N1 at the common connection point of the first current detection circuit 4 and the second current detection circuit or the node N1 based on the control signal output from the current comparison circuit 6. Adjust the value of the discharge current I4.

さて、第１ＬＥＤ回路１に要求される電流Ｉ１と第２ＬＥＤ回路２に要求される電流Ｉ２が異なる場合は、電流比較回路６において、その電流の差分に応じて、電流増減回路７からに吸い込む電流Ｉ３によって電流Ｉ１を増大させ、あるいは電流増減回路７から供給する電流Ｉ４によって電流Ｉ２を増大させる。   Now, when the current I1 required for the first LED circuit 1 and the current I2 required for the second LED circuit 2 are different, in the current comparison circuit 6, the current absorbed from the current increase / decrease circuit 7 according to the difference of the current The current I1 is increased by I3 or the current I2 is increased by the current I4 supplied from the current adjusting circuit 7.

まず、例えば、Ｉ１＝５０ｍＡ、Ｉ２＝１５０ｍＡに設定する場合は、駆動回路３によってＬＥＤ回路２の電流Ｉ２を１５０ｍＡに設定する。これにより当初はＬＥＤ回路１にも電流Ｉ１＝１５０ｍＡが流れる。しかし、このときの電流比較回路６はＩ２−Ｉ１＝１００ｍＡとなるような制御信号を電流増減回路７に対して出力するので、負帰還制御が行われ、その電流増減回路７はその差分の電流Ｉ４（＝１００ｍＡ）をノードＮ１に吐き出す。このとき、電流Ｉ２は駆動回路３によって１５０ｍＡに制限されているので、そのうちの残りの電流５０ｍＡは電流Ｉ１としてＬＥＤ回路１から流れる。つまり、Ｉ２＝Ｉ１＋Ｉ４となる。以上により、ＬＥＤ回路１の電流Ｉ１は５０ｍＡに、ＬＥＤ回路２の電流Ｉ２は１５０ｍＡにそれぞれ設定される。   First, for example, when setting I1 = 50 mA and I2 = 150 mA, the current I2 of the LED circuit 2 is set by the driving circuit 3 to 150 mA. As a result, a current I1 = 150 mA flows through the LED circuit 1 at the beginning. However, since the current comparison circuit 6 at this time outputs a control signal to the current increase / decrease circuit 7 such that I2−I1 = 100 mA, negative feedback control is performed, and the current increase / decrease circuit 7 generates the difference current Discharge I4 (= 100 mA) to the node N1. At this time, since the current I2 is limited to 150 mA by the drive circuit 3, the remaining current of 50 mA flows from the LED circuit 1 as the current I1. That is, I2 = I1 + I4. As described above, the current I1 of the LED circuit 1 is set to 50 mA, and the current I2 of the LED circuit 2 is set to 150 mA.

次に、上記と逆に、Ｉ１＝１５０ｍＡ、Ｉ２＝５０ｍＡに設定する場合は、駆動回路３によってＬＥＤ回路２の電流Ｉ２を５０ｍＡに設定する。これにより当初はＬＥＤ回路１にも電流Ｉ１＝５０ｍＡが流れる。しかし、このときの電流比較回路６ではＩ２−Ｉ１＝−１００ｍＡとなるような制御信号を電流増減回路７に対して出力するので、負帰還制御が行われ、その電流増減回路７はその差分の電流Ｉ３（＝−１００ｍＡ）をノードＮ１から吸い込む。このとき、電流Ｉ２は駆動回路３によって５０ｍＡに制限されているので、ＬＥＤ回路１の電流はＩ１＝Ｉ２＋Ｉ３となる。以上により、ＬＥＤ回路１の電流Ｉ１は１５０ｍＡに、ＬＥＤ回路２の電流Ｉ２は５０ｍＡにそれぞれ設定される。   Next, contrary to the above, when setting I1 = 150 mA and I2 = 50 mA, the current I2 of the LED circuit 2 is set to 50 mA by the drive circuit 3. As a result, a current I1 = 50 mA flows through the LED circuit 1 at first. However, since the current comparison circuit 6 at this time outputs a control signal to the current increase / decrease circuit 7 such that I2−I1 = −100 mA, negative feedback control is performed, and the current increase / decrease circuit 7 A current I3 (= −100 mA) is drawn from node N1. At this time, since the current I2 is limited to 50 mA by the drive circuit 3, the current of the LED circuit 1 is I1 = I2 + I3. Thus, the current I1 of the LED circuit 1 is set to 150 mA, and the current I2 of the LED circuit 2 is set to 50 mA.

このように、第１の実施例によれは、ＬＥＤ回路１、２に要求される電流が異なる場合であっても、それぞれに要求される正確な電流を流すことができる。しかもＬＥＤ回路１、２は直列接続されているので、並列接続した場合と比較して消費電流を低減することもできる。   As described above, according to the first embodiment, even when the currents required for the LED circuits 1 and 2 are different, it is possible to flow the exact current required for each. Moreover, since the LED circuits 1 and 2 are connected in series, current consumption can be reduced as compared with the case where they are connected in parallel.

＜第２の実施例＞
図２に本発明の第２の実施例のＬＥＤ駆動回路を示す。本実施例では、第１電流検知回路４で検知された第１ＬＥＤ回路１の電流Ｉ１と定電流源回路８から与えられる基準値Ｉｒｅｆ１とを第１電流比較回路６Ａで比較して、電流増減回路７を制御する。また、第２電流検知回路５で検知された第２ＬＥＤ回路２の電流Ｉ２と定電流源回路８から与えられる基準値Ｉｒｅｆ２とを第２電流比較回路６Ｂで比較して、駆動回路３Ａでその電流Ｉ２を制御する。 Second Embodiment
FIG. 2 shows an LED drive circuit according to a second embodiment of the present invention. In the present embodiment, the current increasing / decreasing circuit compares the current I1 of the first LED circuit 1 detected by the first current detection circuit 4 with the reference value Iref1 given from the constant current source circuit 8 by the first current comparison circuit 6A. Control 7 Further, the current I2 of the second LED circuit 2 detected by the second current detection circuit 5 and the reference value Iref2 given from the constant current source circuit 8 are compared by the second current comparison circuit 6B, and the current is measured by the drive circuit 3A. Control I2.

まず、例えば、Ｉ１＝５０ｍＡ、Ｉ２＝１５０ｍＡに設定する場合は、定電流発生回路８によって、基準値Ｉｒｅｆ１を５０ｍＡに、基準値Ｉｒｅｆ２を１５０ｍＡに設定する。これにより、第２電流比較回路６Ｂと駆動回路３Ａによって、ＬＥＤ回路２に流れる電流Ｉ２は１５０ｍＡに設定される。ＬＥＤ回路１にも当初は電流Ｉ１＝１５０ｍＡが流れる。しかし、このときの電流比較回路６ではＩ１−Ｉｒｅｆ１＝Ｉ４＝１００ｍＡとなるような制御信号を電流増減回路７に対して出力するので、負帰還制御が行われ、その電流増減回路７はその電流Ｉ４（＝１００ｍＡ）をノードＮ１に吐き出す。このとき、電流Ｉ２は駆動回路３Ａによって１５０ｍＡに制限されているので、そのうちの残りの電流５０ｍＡは電流Ｉ１としてＬＥＤ回路１から流れる。つまり、Ｉ２＝Ｉ１＋Ｉ４となる。以上により、ＬＥＤ回路１の電流Ｉ１は５０ｍＡに、ＬＥＤ回路２の電流Ｉ２は１５０ｍＡにそれぞれ設定される。   First, for example, when setting I1 = 50 mA and I2 = 150 mA, the constant current generating circuit 8 sets the reference value Iref1 to 50 mA and the reference value Iref2 to 150 mA. As a result, the current I2 flowing through the LED circuit 2 is set to 150 mA by the second current comparison circuit 6B and the drive circuit 3A. The current I1 = 150 mA initially flows in the LED circuit 1 as well. However, in the current comparison circuit 6 at this time, a control signal such that I1-Iref1 = I4 = 100 mA is output to the current increase / decrease circuit 7, so negative feedback control is performed. Discharge I4 (= 100 mA) to the node N1. At this time, since the current I2 is limited to 150 mA by the drive circuit 3A, the remaining current of 50 mA flows from the LED circuit 1 as the current I1. That is, I2 = I1 + I4. As described above, the current I1 of the LED circuit 1 is set to 50 mA, and the current I2 of the LED circuit 2 is set to 150 mA.

なお、本実施例では、基準値Ｉｒｅｆ１，Ｉｒｅｆ２を電流Ｉ１，Ｉ２と同じ値に設定したが、それぞれＩ１／ｎ、Ｉ２/ｍとし、第１電流検知回路４、第２電流検知回路６から第１電流比較回路６Ａ、第２電流比較回路６Ｂに入力する電流をそれぞれＩ１／ｎ、Ｉ２/ｍとして比較しても良い。   In the present embodiment, the reference values Iref1 and Iref2 are set to the same values as the currents I1 and I2, but with I1 / n and I2 / m, respectively, the first current detection circuit 4 and the second current detection circuit 6 The currents input to the one-current comparison circuit 6A and the second current comparison circuit 6B may be compared as I1 / n and I2 / m, respectively.

次に、上記と逆に、Ｉ１＝１５０ｍＡ、Ｉ２＝５０ｍＡに設定する場合は、定電流発生回路８によって、基準値Ｉｒｅｆ１を１５０ｍＡに、基準値Ｉｒｅｆ２を５０ｍＡに設定する。これにより、第２電流比較回路６Ｂと駆動回路３Ａによって、ＬＥＤ回路２の電流Ｉ２は５０ｍＡに設定される。ＬＥＤ回路１にも当初は電流Ｉ１＝５０ｍＡが流れる。しかし、このときの第１電流比較回路６Ａでは、Ｉ１−Ｉｒｅｆ１＝Ｉ３＝−１００ｍＡとなるような制御信号を、電流増減回路７に対して出力するので、負帰還制御が行われ、その電流増減回路７はその電流Ｉ３（＝１００ｍＡ）をノードＮ１から吸い込む。このとき、電流Ｉ２は駆動回路３Ａによって５０ｍＡに制限されているので、Ｉ１＝Ｉ２＋Ｉ３となる。以上により、ＬＥＤ回路１の電流Ｉ１はＩ１＝１５０ｍＡに、ＬＥＤ回路２の電流Ｉ２は５０ｍＡにそれぞれ設定される。   Next, conversely to the above, when setting I1 = 150 mA and I2 = 50 mA, the constant current generation circuit 8 sets the reference value Iref1 to 150 mA and the reference value Iref2 to 50 mA. Thus, the current I2 of the LED circuit 2 is set to 50 mA by the second current comparison circuit 6B and the drive circuit 3A. The current I1 = 50 mA initially flows in the LED circuit 1 as well. However, in this case, in the first current comparison circuit 6A at this time, a control signal such that I1-Iref1 = I3 = -100 mA is output to the current increase / decrease circuit 7, so negative feedback control is performed. Circuit 7 sinks its current I3 (= 100 mA) from node N1. At this time, since the current I2 is limited to 50 mA by the drive circuit 3A, I1 = I2 + I3. Thus, the current I1 of the LED circuit 1 is set to I1 = 150 mA, and the current I2 of the LED circuit 2 is set to 50 mA.

この場合も上記同様、基準値Ｉｒｅｆ１，Ｉｒｅｆ２を電流Ｉ１，Ｉ２と同じ値に設定する代わりに、それぞれＩ１／ｎ、Ｉ２/ｍとし、第１電流検知回路４、第２電流検知回路６から第１電流比較回路６Ａ、第２電流比較回路６Ｂに入力する電流をそれぞれＩ１／ｎ、Ｉ２/ｍとして比較しても良い。   Also in this case, the reference values Iref1 and Iref2 are set to I1 / n and I2 / m, respectively, instead of setting the reference values Iref1 and Iref2 to the same values as the currents I1 and I2, respectively, and the first current detection circuit 4 and the second current detection circuit 6 The currents input to the one-current comparison circuit 6A and the second current comparison circuit 6B may be compared as I1 / n and I2 / m, respectively.

以上から、第２の実施例によれば、ＬＥＤ回路１の電流Ｉ１、ＬＥＤ回路２の電流Ｉ２を個々に精度高く設定することができる。第１の実施例では、電流Ｉ１とＩ２の差分により電流Ｉ１あるいはＩ２を制御する相対的制御であったが、第２の実施例では電流Ｉ１はＩｒｅｆ１となるように制御し、電流Ｉ２はＩｒｅｆ２となるように制御するので、絶対的な制御となり、それぞれの電流Ｉ１，Ｉ２を精度を高く設定することができる利点がある。   As described above, according to the second embodiment, the current I1 of the LED circuit 1 and the current I2 of the LED circuit 2 can be set with high accuracy. In the first embodiment, relative control is performed to control the current I1 or I2 by the difference between the currents I1 and I2. However, in the second embodiment, the current I1 is controlled to be Iref1 and the current I2 is Iref2 Since the control is performed as follows, there is an advantage that absolute control can be performed, and the respective currents I1 and I2 can be set with high accuracy.

１，１１，２１，２，１２，２２：ＬＥＤ回路
３，３Ａ，１３，２３：駆動回路
４：第１電流検出回路
５：第２電流検出回路
６：電流比較回路、６Ａ：第１電流比較回路、６Ｂ：第２電流比較回路
７：電流増減回路
８：定電流源回路 1, 11, 21, 2, 12, 22: LED circuit 3, 3A, 13, 23: Drive circuit 4: first current detection circuit 5: second current detection circuit 6: current comparison circuit, 6A: first current comparison Circuit 6B: second current comparison circuit 7: current increase / decrease circuit 8: constant current source circuit

Claims (2)

第１ＬＥＤ回路と第２ＬＥＤ回路の直列回路の該第２ＬＥＤ回路の側に駆動回路を直列接続した回路を第１電源端子と第２電源端子の間に接続し、前記第２ＬＥＤ回路に要求される電流を前記駆動回路により設定し、前記第１ＬＥＤ回路に要求される電流と前記第２ＬＥＤ回路に要求される電流の差分に基づき、前記第１ＬＥＤ回路と前記第２ＬＥＤ回路の共通接続のノードに正又は負の電流を供給するＬＥＤ駆動回路において、
前記第１ＬＥＤ回路に流れる電流を検知する第１電流検知回路と、前記第２ＬＥＤ回路に流れる電流を検知する第２電流検知回路と、前記第１電流検知回路で検知された電流と前記第２電流検知回路で検知された電流を比較する電流比較回路と、該電流比較回路で得られた比較結果に基づき前記ノードに電流を吐き出し又は前記ノードから電流を吸い込む電流増減回路と、を設けたことを特徴とするＬＥＤ駆動回路。 A circuit in which a drive circuit is connected in series on the side of the second LED circuit of the series circuit of the first LED circuit and the second LED circuit is connected between the first power supply terminal and the second power supply terminal, and the current required for the second LED circuit Are set by the drive circuit, and a positive or negative node is commonly connected to the first LED circuit and the second LED circuit based on the difference between the current required for the first LED circuit and the current required for the second LED circuit. In the LED drive circuit that supplies
A first current detection circuit detecting a current flowing through the first LED circuit, a second current detection circuit detecting a current flowing through the second LED circuit, a current detected by the first current detection circuit, and the second current Providing a current comparison circuit for comparing the current detected by the detection circuit, and a current increase / decrease circuit for discharging current to the node based on the comparison result obtained by the current comparison circuit or for absorbing current from the node Characteristic LED drive circuit. 第１ＬＥＤ回路と第２ＬＥＤ回路の直列回路の該第２ＬＥＤ回路の側に駆動回路を直列接続した回路を第１電源端子と第２電源端子の間に接続し、前記第２ＬＥＤ回路に要求される電流を示す第２基準値に基づき前記駆動回路の電流を設定し、前記第１ＬＥＤ回路に要求される電流を示す第１基準値に基づき前記第１ＬＥＤ回路と前記第２ＬＥＤ回路の共通接続のノードに正又は負の電流を供給するＬＥＤ駆動回路において、
前記第１ＬＥＤ回路に流れる電流を検知する第１電流検知回路と、前記第２ＬＥＤ回路に流れる電流を検知する第２電流検知回路と、前記第１電流検知回路で検知された電流を前記第１基準値と比較する第１電流比較回路と、該第１電流比較回路の比較結果に基づき前記ノードに電流を吐き出し又は前記ノードから電流を吸い込む電流増減回路と、前記第２電流検知回路で検知された電流を前記第２基準値と比較する第２電流比較回路とを備え、前記駆動回路は前記第２電流比較回路の比較結果に基づき駆動電流が制御されることを特徴とするＬＥＤ駆動回路。
 A circuit in which a drive circuit is connected in series on the side of the second LED circuit of the series circuit of the first LED circuit and the second LED circuit is connected between the first power supply terminal and the second power supply terminal, and the current required for the second LED circuit The current of the drive circuit is set based on a second reference value indicating a positive value, and the node connected in common to the first LED circuit and the second LED circuit is positive based on a first reference value indicating a current required for the first LED circuit. Or in an LED drive circuit that provides a negative current,
A first current detection circuit detecting a current flowing through the first LED circuit, a second current detection circuit detecting a current flowing through the second LED circuit, and a current detected by the first current detection circuit as the first reference A first current comparison circuit to be compared with a value, a current increase / decrease circuit for discharging current to the node based on the comparison result of the first current comparison circuit, or absorbing current from the node, and detected by the second current detection circuit An LED drive circuit comprising: a second current comparison circuit comparing current with the second reference value, wherein the drive circuit is controlled based on the comparison result of the second current comparison circuit.
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