Overvoltage protection self-recovery energy-saving LED drive power source

Specific embodiment one

[0032] See figure 1 As shown, the present invention is an overvoltage protection self-recovery energy-saving LED drive power supply, including: mains input circuit, rectifier bridge, overvoltage protection circuit, drive chip U1, NPN transistor Q2, power switch Q1, switch transformer T2 And power output;

[0033] The mains input circuit is connected to the drive chip U1 through the rectifier bridge and the overvoltage protection circuit in turn; the drive chip U1 is connected to the power output terminal through the power switch tube Q1 and the switching transformer T2 in turn; the drive chip U1 controls the load output of the power output terminal; among them, The driving chip U1 is connected to the switching transformer T2 through the NPN transistor Q2; one side of the switching transformer T2 is provided with coil 1 and coil 2, and the other side of the switching transformer T2 is provided with coil 3; among them, the coil 1 is connected in parallel with a pulse absorption circuit; one end of the coil 1 Connect to the output terminal of the rectifier bridge; the other end of coil 1 is connected to the drain of the power switch tube Q1; one end of coil 2 is connected to the internal grounding module; the other end of coil 2 is connected to the base of the NPN transistor Q2 through a resistor R12; One end of the coil 3 is connected to the positive LED+ of the power output terminal through the rectifier diode D7; the other end of the coil 3 is connected to the negative LED- of the power output terminal; the positive and negative terminals of the power output are directly connected in parallel with a discharge resistor R13 and a filter capacitor C9; the coil 3 and the coil 2 Directly set up an isolation capacitor C8;

[0034] The overvoltage protection circuit includes resistors R14, R15, voltage regulator tube D8 and unidirectional thyristor VS1; resistor R14 is connected in series with resistor R15, the other end of resistor R14 is connected to the positive pole of the rectified DC power supply, and the other end of resistor R15 is connected with The cathode of the one-way thyristor VS1 is connected to the negative electrode of the rectified DC power supply, the negative electrode of the voltage regulator tube D8 is connected between the resistor R14 and the resistor R15; the positive electrode of the voltage regulator tube D8 is connected to the control electrode of the one-way thyristor VS1; Connect pin 1 of the drive chip U1 to the anode of the thyristor VS1; the coil 2 of the switching transformer T2 supplies power to pin 1 of the drive chip U1 through the bc junction of the NPN transistor Q2; the coil 2 of the switching transformer T2 passes through the be junction of the NPN transistor Q2 Send a zero current detection signal to pin 5 of the drive chip U1;

[0035] Pin 1 of the drive chip U1 is the power supply pin, pin 2 of the drive chip U1 is the input terminal for the attenuation signal of the input voltage, pin 3 of the drive chip U1 is the loop compensation point pin, and pin 4 of the drive chip U1 is the ground pin , Pin 5 of the drive chip U1 is the primary side sampling and zero-crossing detection pin, and pin 6 of the drive chip U1 is the switch gate drive pin. Among them, there is also a filter capacitor C3 and a filter capacitor C3 between the 1 pin and the power supply resistor R2. Voltage regulator tube D5; one end of the filter capacitor C3 and the reverse input end of the voltage regulator tube D5 are connected to the internal grounding module; the other end of the filter capacitor C3 and the positive input end of the voltage regulator tube D5 are connected to pin 1; among them, pin 2 The attenuation sampling resistor R3 and the attenuation sampling resistor R4 are connected to the output end of the rectifier bridge, and pin 2 is connected to the internal grounding module through the attenuation sampling resistor R7; among them, the attenuation sampling resistor R7 is connected in parallel with a filter capacitor C5, and the filter capacitor C5 is input to pin 2. The attenuated signal is filtered; among them, pin 3 is connected to one end of the loop compensation capacitor C6; the other end of the loop compensation capacitor C6 is connected to the internal grounding module; among them, pin 4 is connected to the internal grounding module; among them, pin 5 is connected to the Current resistor R11 is connected to the emitter of NPN transistor Q2; pin 5 is connected between resistor R3 and resistor R4 through voltage sampling resistor R5; pin 5 is connected to resistor R10 and the source of N-channel field effect Q1 through resistor R9; The other end of the resistor R10 is connected to the internal grounding module; pin 5 is also connected to a filter capacitor C7; the filter capacitor C7 is connected in parallel with the resistor R9 and the resistor R10; among them, pin 6 is connected to the gate of the power switch Q1 through a current limiting resistor.

[0036] In this embodiment, the mains input circuit is connected to the rectifier bridge through the choke coil T1 and the AC filter capacitor C1; the rectifier bridge rectifies the alternating current to output direct current; the output end of the rectifier bridge is connected to the drive chip U1 through the filter circuit and the overvoltage protection circuit Connect with switching transformer T2.

[0037] In this embodiment, the filter circuit includes an inductor L1, a resistor R1, and a capacitor C2; wherein the inductor L1 and the resistor R1 are connected in parallel and then connected in series to the output end of the rectifier bridge.

[0038] In this embodiment, the pulse absorption circuit includes a capacitor C4, a resistor R6 and a diode D6; one end of the capacitor C4 and the resistor R6 are both connected to one end of the coil 1; the other end of the capacitor C4 and the resistor R6 are both connected to the reverse input end of the diode D6 Connection; the forward input end of diode D6 is connected to the other end of coil 1.

[0039] In this embodiment, the collector of the NPN transistor Q2 is connected to pin 1 of the driver chip U1 and one end of the filter capacitor C3; the emitter of the NPN transistor Q2 is connected to pin 5 of the driver chip through a current limiting resistor R11.

[0040] In this embodiment, the driving chip is an MP4026 primary-side feedback driving chip; the power switch Q1 adopts an N-channel field effect transistor.

Specific embodiment two

[0041] In this embodiment, the working process of the driving chip U1 is as follows, including two working states:

[0042] When the power switch Q1 is turned on: the drive chip U1 starts to work, and outputs the drive signal from pin 6 to the gate of the power switch Q1. After the power switch Q1 is turned on, the switching transformer T2 is stored, and the 5 pin of the drive chip U1 is detected at this time It is the current signal sent by R10. When the current signal voltage is greater than the output voltage of the internal multiplier of the drive chip U1, pin 6 stops outputting the drive signal and turns off the power switch Q1;

[0043] When the power switch Q1 is turned off: After the power switch Q1 is turned off, the switching transformer T2 begins to discharge the load, and the 5 pin of the driving chip U1 detects the zero current detection signal sent by the NPN transistor Q2, when the zero current detection signal voltage When it drops to 0.35V, the 6 pin of the driving chip U1 starts to output the driving signal again, and the power switch Q1 is turned on again.

[0044] Among them, after the power switch Q1 is turned off, when the induced current of the switching transformer T2 coil 2 is large, the voltage of the switching transformer T2 coil 2 supplies power to the pin 1 of the driving chip U1 through the bc junction of the NPN transistor Q2, and at the same time through the NPN transistor Q2 The be junction of the drive chip delivers a zero current detection signal to pin 5 of the driver chip U1. When the induced current of the coil 2 of the switching transformer T2 becomes smaller, the NPN transistor Q2 will control the voltage in the filter capacitor C3, and the NPN transistor Q2 will continue to deliver the zero current detection signal to the 5 pin of the driving chip U1. At this time, the induced current of the coil 2 of the switching transformer T2 only drives the NPN transistor Q2, not directly sent to the 5 pin of the driving chip U1. When the induced current of the coil 2 of the switching transformer T2 drops to almost equal to 0, the zero current detection signal voltage delivered by the filter capacitor C3 to the 5 pin of the driving chip U1 through the NPN transistor Q2 can be equal to 0.35V. In this way, the magnetic energy in the switching transformer T2 is fully utilized, and the power saving effect is obtained.

Specific embodiment three

[0045] In this embodiment, the working process of the overvoltage protection circuit is as follows:

[0046] Resistors R14, R15, voltage regulator tube D8 and unidirectional thyristor VS1 form an overvoltage protection self-recovery circuit;

[0047] When the input mains voltage is normal, the DC voltage after the rectifier bridge is divided by the resistor R14 and the resistor R15, which is not enough to reverse the conduction of the zener tube D8, and the zener tube D8 is in the off state. The thyristor VS1 is also in the disconnected state, which has no effect on the operation of the driving chip U1.

[0048] When the input mains voltage is as high as 280V, the voltage divided by the resistor R14 and the resistor R15 will make the Zener tube D8 reversely conduct, and the Zener tube D8 will short-circuit the drive chip U1 after reverse conduction. When U1 loses power supply voltage, it stops the work of the drive circuit. When the mains voltage returns to normal, the voltage divided by resistors R14 and R15 returns to normal to disconnect the unidirectional thyristor VS1 and drive the 1 of the chip U1 The working voltage of the pin returns to normal, so that the drive circuit resumes normal operation.