Other Parts Discussed in Thread: UCC24636
Tool/software:
Hello, I am using UCC28740 and UCC24636 in my desing. I used WEBENCH power designer tool as starting point. You can find my schematic at below.
After several testing, I added RC between primary MOSFETs drain- source nodes. I used 1000pF and 100R and It does help to reduce ringing at MOSFETs turn-off. However the ringing at turn-on time is still too high.
I removed D1 TVS as snubber and place RC snubber there also. And I add another 100R befor the D6 diode. Then added the 2R resistor at drive signal. But the ringing is still there. Have tried different values for RCD snubber. Also added some ceramic caps at output.
The Output ringing at turn-on is slightly changing. I wonder that the issue may cause from someting else. Maybe the feedback circuit or secondar side switching.
You can see the Vgs voltage and Output voltage waveforms at below. (Vgs probe is in 10X mode). When MOSFET is turning on, the voltage at drain is too high ? (approximately 370v)
My nominal input Voltage is 230Vac/50Hz. I desired output is 5V/1A. As you can see, It is quite stable except for the switching moments.
Need help to improve this output. Any waveform you need to know ? Please inform me thanks.
Regards.
