UCC27282: ucc27282 HO is not operation

Hi

I have more tested as follow.

1. connect to FET and Rload

2. I found to HO wave is abnormal

  1) Input PWM HI and LI is  different timing , but U8,U11 HO wave is same timing

Please checking to problem and inform to me

refer to attached xls file( test data)

Thanks and BR

PJ

  ucc27282_HO_problem_report.xlsx

Hi Pil,

Looking at the waveforms, this indeed seems like a very odd problem. To get the obvious out the way, can you make sure your PWM lines are connected to their respective inputs? PWM_HI should be connected to U8 HI and U11 LI, and PWM_LO should be connected to U8 LI and U11 HI. Can you also confirm if R69, R70, R71, and R72 are truly open? If they were open, then the antiparallel diode would prevent the FETs from receiving the output signal to turn them on.

Can you also confirm if you are measuring HO signal by referencing it with HS, not VSS? To measure HO-HS, you need a differential probe. Also, if HS is floating or has a heavy load (high resistance), the bootstrap capacitor may not charge well.

I also cannot see the waveforms clearly on the "HO_Problem" sheet of the excel file, so can you reupload them?

Thanks,
Rubas