CN204191002U - Can the LED drive circuit of anti-2KV surge voltage - Google Patents

Abstract

The utility model provide a kind of can the LED drive circuit of anti-2KV surge voltage, comprise power input, power input L connects fuse to bridge heap input 1, power input N is connected to bridge heap input 3, bridge heap input (1,3) connects electric capacity, bridge heap exports positive and negative electrode and connects electric capacity, bridge heap positive pole access inductance, contact resistance is held to power supply chip ST, ST holds contact resistance to Q1, chip ST holds connection electric capacity and TVS pipe to GND, and positive pole inductance connection electric capacity and piezo-resistance are to GND, and bridge heap negative pole connects inductance to GND.The utility model combinationally uses the unidirectional TVS pipe of piezo-resistance, differential mode inductance and low pressure, effectively improves the defect that single-stage PFC+FLYBACK isolated LED drive power antisurge is weak, antisurge grade is promoted to 2KV from 0.5KV.

Description

LED drive circuit that can resist 2KV surge voltage

technical field

The utility model relates to the field of LED driving power supply, in particular to an LED driving circuit capable of resisting 2KV surge voltage.

Background technique

At present, the single-stage PFC+FLYBACK isolated power supply is widely used in LED driving, and the LED driving power supply below 25W is mostly used. This kind of circuit has high power factor, simple structure and easy miniaturization. Due to the single-stage PFC+FLYBACK structure, there is no large-capacity capacitor at the input end of the power supply, so that the surge voltage can easily enter the circuit control system and cause damage to the power supply.

Usually, a varistor is added at the input end to protect against surge voltage. Although it can meet the 0.5KV surge voltage test specified by the certification agency for a power supply within 25W, in practical applications, power grids in many countries and regions fluctuate frequently. The voltage fluctuation is abnormal, and the surge voltage limit of only 0.5KV cannot meet the use requirements. There are two ways to improve the anti-surge level: 1. Increase the anti-surge energy level of the varistor, so that the volume of the varistor will be large, which will affect the original design structure; 2. Choose to increase the high voltage at the power input end Although the bidirectional TVS tube can improve the anti-surge level, the cost is relatively high, and it is generally not used.

Contents of the invention

The utility model aims at improving the difficulty of anti-surge of the existing single-stage PFC+FLYBACK isolated LED drive circuit, conducts research and improvement, and provides an LED drive circuit capable of resisting 2KV surge voltage.

The technical scheme of the utility model is as follows:

An LED drive circuit capable of resisting 2KV surge voltage, characterized in that it includes power input terminals (L, N), the power input terminal L is connected to the fuse (F1) to pin 1 of the bridge stack (BD1), and the power input terminal N is connected to To the 3 pins of the bridge stack (BD1), the 1 and 3 pins of the bridge stack (BD1) are connected to the safety capacitor (CX1) and the varistor (VR1) to form the input circuit of the AC terminal of the power supply; the 2 and 4 pins of the bridge stack (BD1) are connected to Capacitor (C1), bridge pile (BD1) 2 pins are connected to differential mode inductor (L1), differential mode inductor (L1) is connected to varistor (VR2) and capacitor (C2) to GND, bridge stack (BD1) 4 pins are connected poorly The mode inductor (L2) to GND forms the power supply circuit of the high voltage end of the power supply; the differential mode inductor (L1) connects the resistor (R6) to the ST terminal of the chip, and the ST terminal of the chip connects the TVS tube (D5) and the capacitor (C5) to GND, and connects the resistor ( R7) to the MOS tube Q1 G terminal to form a power supply control terminal power supply return circuit. the

The beneficial technical effects of the utility model are: connect the same type of varistor to the AC and DC ends of the LED power supply respectively, connect the positive and negative poles of the DC end of the bridge to the differential mode inductor and then connect the varistor, and the ST terminal of the power chip Connect the TVS tube to GND. The role of the varistor and the TVS tube is to suppress the surge voltage, and the use of the differential mode inductor in series in the circuit can also effectively suppress the surge voltage. When the surge voltage enters the power supply, it first attenuates through the varistor at the AC end, passes through the rectifier bridge, passes through the differential mode inductor and the varistor at the DC end for the second attenuation, and the residual surge voltage attenuates again through the resistor and the TVS tube. , to ensure that the voltage entering the power chip and MOS tube is the normal working voltage. The method of blocking the surge voltage in sections is not only low in cost, but also can effectively increase the surge resistance level of the power supply from 0.5KV to 2KV, which greatly improves the grid adaptability of the single-stage PFC+FLYBACK isolated LED drive power supply in different regions. It solves the problem of damage caused by excessive surge voltage.

Description of drawings

Fig. 1 is a kind of preferred circuit schematic diagram of the present utility model.

detailed description

The specific embodiment of the utility model will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, the utility model includes power input terminals (L, N). The power input terminal L is connected to the fuse (F1) to pin 1 of the bridge stack (BD1), and the power input terminal N is connected to the bridge stack (BD1) pin 3. The 1st and 3rd pins of the bridge stack (BD1) are connected to the safety capacitor (CX1) and the varistor (VR1) to form the input circuit of the AC terminal of the power supply; the 2nd and 4th pins of the bridge stack (BD1) are connected to the capacitor (C1), and the bridge stack ( BD1) Pin 2 is connected to differential mode inductor (L1), differential mode inductor (L1) is connected to piezoresistor (VR2) and capacitor (C2) to GND, bridge stack (BD1) pin 4 is connected to differential mode inductor (L2) to GND The power supply circuit of the high-voltage end of the power supply; the differential mode inductor (L1) is connected to the resistor (R6) to the ST terminal of the chip, the ST terminal of the chip is connected to the TVS tube (D5) and the capacitor (C5) to GND, and the resistor (R7) is connected to the G terminal of the MOS tube Q1 , forming the power control terminal to supply power back to the circuit.

The working principle of the utility model is as follows:

When the surge voltage of the grid is attenuated once by the varistor VR1 at the AC end, it passes through the bridge stack and passes through the combined resistance of L1, L2 differential mode inductors and VR2 varistors, and the surge voltage has been mostly attenuated. With the re-attenuation of the unidirectional TVS tube, the surge voltage entering the ST terminal of the power chip and the MOS tube Q1 has basically disappeared, and the circuit will not be damaged due to the impact of the surge voltage, ensuring the long life of the LED lamp.

The main components list in Figure 1:

The above are only preferred implementations of the utility model, and the utility model is not limited to the above examples. It can be understood that other improvements and changes directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present utility model shall be considered to be included in the protection scope of the present utility model.

Claims (1)

1. An LED drive circuit capable of resisting 2KV surge voltage, characterized in that it includes power input terminals (L, N), the power input terminal L is connected to the fuse (F1) to pin 1 of the bridge stack (BD1), and the power input terminal N is connected to the 3 pins of the bridge stack (BD1), and the 1 and 3 pins of the bridge stack (BD1) are connected to the safety capacitor (CX1) and the varistor (VR1) to form the input circuit of the AC terminal of the power supply; the bridge stack (BD1) 2, 4 The pin is connected to the capacitor (C1), the 2 pins of the bridge stack (BD1) are connected to the differential mode inductor (L1), the differential mode inductor (L1) is connected to the varistor (VR2) and the capacitor (C2) to GND, and the 4 pins of the bridge stack (BD1) Connect the differential mode inductor (L2) to GND to form the power supply circuit at the high voltage end of the power supply; the differential mode inductor (L1) connects the resistor (R6) to the ST terminal of the chip, and the ST terminal of the chip connects the one-way TVS tube (D5) and capacitor (C5) to GND , Connect the resistor (R7) to the G terminal of the MOS tube Q1 to form the power supply control terminal and return the circuit.