LM5039: About LM5039 control question

Hi Jimmy

The red line is for HO or LO? And what condition does the issue occur (load current)?  The output voltage can be regulated correctly?

BR

Jerry Xu

Hi Jerry,

Red line is HO and No any load. Due to Hi and Lo side gate asymmetry. the system can not be working. the output voltage will crash. 

Could you let the customer test waveforms of RAMP, COMP, HO, LO at the same time?

Hi Jerry,

The PWM is IC output. But i think gate driver and vcc, ground has some problem.

Could you help check the gate to photocoupler of supply power and ground is okay or not?

If you think that the gate driver may cause this problem, you can recommend customer to remove resistor R122B and R125B. Then test the PWM output waveform.

Hi Jerry,

After I checked, the schematic is okay.

Could you give me some suggestions? Which problem will cause the issue? thx for your help.

First, you need to ensure that IC work normally. You can recommend customer to remove resistor R122B and R125B. Then test the PWM output waveform.

Second, if the IC work normally, you can suggest customer to check gate drive circuit step by step.