JP2007318881A - Power supply unit for lighting of led - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional system such as that power consumption increases and wiring complicates since it is one for matching with the voltage of a power source by connecting LEDs in series or in parallel and lighting them when the lighting of so many LEDs as to go higher than the power source voltage is required as the light source of a vehicle lamp fitting. <P>SOLUTION: This is a power supply unit 1 for lighting of LED which uses a dual output type DC-DC converter control IC2 and constitutes a step-up circuit 3 with one output and constitutes a polarity-inverted step-up circuit 4 with the other output and connects and lights so many LEDs 8 as to fit the voltage between both electrodes. The power unit for lighting of LED includes a current detecting circuit 4 and a voltage detecting circuit 5 on the side of the step-up circuit and a shut down circuit 7 which breaks power when the wire breaking of the load including the LED is detected, on the side of the voltage detecting circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power supply device for lighting an LED. For example, a light emitting area is large like a tail / stop lamp for a vehicle, and a large number of LEDs are required to uniformly shine the entire surface. When all the LEDs are connected as a single circuit in series, the present invention relates to a power supply device used when the vehicle power supply voltage is exceeded.

  2. Description of the Related Art Conventionally, for example, as a power supply circuit 90 for lighting a plurality of LEDs 80 connected in series with a battery having a lower output voltage, a booster circuit controlled by a control circuit 91 as shown in FIG. 92 and the charge pump type inversion voltage generation circuit 93 are driven so that a prescribed voltage is obtained between the positive side of the booster circuit 92 and the negative side of the inversion voltage generation circuit 93. There was something that turned on.

In this case, the voltage divided by the resistors 94 and 95 is fed back to the output of the booster circuit 92 to the control circuit 91 so that the voltage does not rise too much, and the output voltage is controlled. Further, a constant current unit 96 as shown in a circuit diagram in FIG. 3 is inserted in series with the LED 80, and the LED 80 is controlled to emit light with stable brightness.
JP 2005-136157 A

  However, in the above-described conventional power supply device, the negative-side power supply generally employs a charge pump type or the like for simplification of the configuration. For example, a high-power, high-power LED for a vehicle headlight or the like For example, the FET 96a and the resistor 96b used in the constant current unit 96 flow from several hundred mA to several A, resulting in problems such as an increase in size or heat generation. Will be produced.

  Therefore, when driving a high-power LED such as for a vehicle headlight using a power supply device having a conventional configuration, for example, a plurality of medium-sized power supply devices are prepared, and each of the plurality of power supply devices has an LED. It is necessary to take measures such as lighting up the required number of LEDs as a whole, which causes problems such as complicated wiring and maintenance, and inevitable cost increase problems. It becomes.

  The present invention uses a dual output type DC-DC converter control IC as a specific means for solving the above-described problems in the conventional power supply apparatus, and outputs one of the dual output type DC-DC converter control ICs. A booster circuit is configured with the other output, and a polarity inversion booster circuit is configured with the other output, and a number of LEDs corresponding to the voltage between the two electrodes are connected in series between the positive electrode of the booster circuit and the negative electrode of the polarity invertor booster circuit. LED lighting power supply device to be turned on, a current detection circuit and a voltage detection circuit are provided on the booster circuit side, the voltage of the polarity inversion booster circuit by the current detection circuit and the voltage detection circuit And a current are controlled, and when a short circuit of a load including the LED is detected on the current detection circuit side, and the LED is included on the voltage detection circuit side. The present invention solves the problem by providing an LED lighting power supply device that is provided with a shutdown circuit that shuts off the power applied to the LED lighting power supply device when a load disconnection is detected. Is.

  According to the present invention, using a dual output type DC-DC converter control IC, both the positive boost side and the negative boost side are performed by the DC-DC converter, the positive boost side positive electrode and the negative boost side negative electrode With the configuration in which the LED is connected between the power supply voltage, it is possible to supply necessary and sufficient voltage and power even for a lighting voltage higher than the power supply voltage, and it is possible to reduce both size and cost. There is an effect.

  Below, this invention is demonstrated in detail based on embodiment shown in a figure. 1 is an LED lighting power supply device according to the present invention, and this LED lighting power supply device 1 is abbreviated as a dual output type DC-DC converter control IC 2 (hereinafter abbreviated as a dual output converter IC2). For example, by using TL 1451A) manufactured by TI as a pair of outputs forming a constant current control unit and a constant voltage control unit, wiring to the LED 8 forms a simpler control circuit and protection circuit than before, and Thus, it is possible to turn on and control the LEDs 8 in which a number equal to or higher than the power supply voltage of the vehicle or the like is connected in series without unnecessarily increasing the voltage rating of the parts.

  Here, the dual output converter IC2 will be briefly described. The dual output converter IC2 has two channels of output and a control function thereof, and each output is fed back independently and individually. PWM control is performed by a built-in error amplifier and a comparator to which negative feedback is applied. As a result, the output also operates independently and stably.

  The step-up DC-DC converter 3 comprising a coil 3a, FET 3b, diode 3c, and capacitor 3d controlled by one channel 2a of the dual output converter IC2 is a DC-DC converter having the same operating principle as a conventional one. It is composed.

  The output of the DC-DC converter 3 is detected by the current detection resistor 4a of the current detection circuit 4, and feedback is performed to the feedback terminal 2c of the dual output converter IC2 in the same manner as before, and the voltage drop at both ends is constant. Thus, the forward current of the LED 8 is controlled to be a constant current. The current detection resistor 4a is also used for output short-circuit detection, as in the prior art.

  The voltage detector 5 divides the voltage by an appropriate ratio between the resistor 5a and the resistor 5b, and feedback is performed to the feedback terminal 2d of the dual output converter IC2 to control the output voltage. When is open, a protection signal is output so that the output voltage does not rise rapidly.

  When an output short circuit signal is output from the current detection circuit 4 or when an output open signal is output from the voltage detection circuit, it is applied to the LED lighting power supply device 1 by the FET 7a of the shutdown circuit 7. The power supply is shut down and protected.

  In the other channel 2b of the dual output converter IC2, an FET 6a, a coil 6b, a diode 6c, and a capacitor 6d controlled by the channel 2b constitute a polarity inversion type DC-DC converter 6. When the FET 6a is on, the current flows to the GND through the coil 6b because the diode 6c is reverse biased, and at this time, energy is stored in the coil 6b.

  Next, when the FET 6a is turned off, the back electromotive force corresponding to the energy is generated to keep the current in the coil 6b, the diode 6c is conducted, and the capacitor 6d is charged. At this time, the polarity charged to the capacitor 6d is positive on the GND side and negative on the anode side of the diode 6c from the direction of the flowing current. Therefore, if the anode side of the diode 6c is taken out as a DC output, the polarity is inverted with respect to the power supply voltage. DC-DC converter.

  The LED 8 as a load is connected by connecting the anode side of the LED 8 to the positive side output of the DC-DC converter 3 and the negative side of the polarity inversion type DC-DC converter 6 biased to the negative potential on the cathode side. When connected to the output, the potential difference can be connected to a high voltage having a potential approximately twice that of the DC-DC converter 3. In this case, the forward current applied to the LED 8 is made constant by adjusting the voltage on the DC-DC converter 3 side as is clear from FIG.

  By configuring as described above according to the present invention, it is only necessary to provide the current detection and short protection part in one place as compared with the conventional one, and the number of parts is halved. This is because all the numbers of LEDs 8 used are connected in series. In the circuit of the present invention, the positive and negative voltages are prorated according to GND, so that the FET (3b, 6a), diode (3c, 6c), capacitor (3d, 6d), etc. As compared with the DC-DC converter of the conventional example, a particularly high voltage is not applied and a high-rated one is not required.

It is a circuit diagram which shows the Example of the power supply device for LED lighting which concerns on this invention. It is a circuit diagram which shows a prior art example. It is a circuit diagram which shows the principal part of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... LED lighting power supply device 2 ... Dual output type DC-DC converter control IC
2a ... one output terminal 2b ... the other output terminal 2c ... feedback terminal 2d ... feedback terminal 3 ... DC-DC converter 3a ... coil 3b ... FET
DESCRIPTION OF SYMBOLS 3c ... Diode 3d ... Capacitor 4 ... Current detection circuit 4a ... Current detection resistance 5 ... Voltage detection circuit 5a, 5b ... Resistor 6 ... Polarity inversion type DC-DC converter 6a ... FET
6b ... Coil 6c ... Diode 6d ... Capacitor 7 ... Shutdown circuit 7a ... FET
7b ... NAND gate 8 ... LED
9 ... Power supply

Claims (1)

  Using a dual output type DC-DC converter control IC, one output of the dual output type DC-DC converter control IC constitutes a booster circuit, and the other output constitutes a polarity inversion booster circuit. An LED lighting power supply device in which a number of LEDs corresponding to the voltage between the two electrodes are connected in series between a positive electrode and a negative electrode of the polarity inversion booster circuit to be lit, and a current detection circuit and a voltage are provided on the booster circuit side. A detection circuit, and the current detection circuit and the voltage detection circuit control the voltage and current of the polarity inversion booster circuit, and the LED is connected to the current detection circuit side. When a short circuit of the load including the LED is detected and when a disconnection of the load including the LED is detected on the voltage detection circuit side, the power applied to the LED lighting power supply device LED lighting power supply apparatus characterized by shutdown circuit for interrupting is provided.

Images