Synchronous rectifier buck converter help.

warchiefl

Synchronous rectifier buck converter help. [Copy link]

I recently encountered a problem while doing an experiment in the laboratory. The circuit topology is a synchronous buck circuit. IR2110 is used as the driver IC, and STM32 outputs complementary PWM waves. I drew the schematic diagram and PCB by myself. When debugging, the IR2110 module and the stm32 module are intact. When the IR2110 is powered on and the drive signal (open loop) of the stm32 is input (the IR2110 is currently directly supplied by a DC power supply), the input voltage will be pulled down to 1v (it should have reached the input current limit value), but the output voltage is still there, and it feels like the tube is still working. May I ask what is going on, guys? P.S.: When IR2110 and Vin share a DC power supply, (15V input) VCC will be pulled down to the minimum IR2110 operating voltage of 9V, and the output voltage is also there at this time. The parameters of the circuit are: Vin=10V Vo=5V R=5 ohms (sliding resistor) fsw=200k L=100u fush Attached schematic diagram

maychang

Without going into the details of the circuit, the OP uses 7805 to power IR2110. I'm afraid the voltage is not enough?

warchiefl

maychang posted on 2018-10-24 10:26 Let’s not talk about the details of the circuit. The OP uses 7805 to power the IR2110. I’m afraid the voltage is not enough?

7085 is used to power the digital part. The analog part uses LDO, but it is too easy to burn out. So I just use a DC power supply of 15V.

maychang

warchiefl posted on 2018-10-24 20:30 7085 is used to power the digital part. The analog part uses LDO, but it is too easy to burn out, so we just use a direct DC power supply of 15V

Your Vi is 10V, and Vcc is obviously less than 10V. What is Vcc? Do you have an oscilloscope? It is not enough to rely on a multimeter to make a switching power supply.

warchiefl

maychang posted on 2018-10-24 20:48 Your Vi is 10V, and Vcc is obviously less than 10V. What is Vcc? Do you have an oscilloscope? It is not enough to rely on a multimeter to work with switching power supplies.

Another DC power supply was used to power VCC. Before the main circuit was powered on, the driver was checked with an oscilloscope and they were all good. The bootstrap circuit was also powered up.

maychang

warchiefl posted on 2018-10-24 21:18 Another DC power supply is used to power VCC. Before the main circuit is powered on, the driver is checked with an oscilloscope and all are good. The bootstrap circuit is also lifted.

(1) What is the voltage of Vcc when it is powered by another power supply? (2) The driver waveform is good when the oscilloscope is used before the main circuit is powered on, but the bootstrap circuit cannot be "lifted" before the main circuit is powered on. (3) After powering IR2110, "the input voltage will be pulled down to 1V", what is the input current? What is the output current?