LM5034: IC pulse issue

Hi AM,

Please provide schematic to provide better understanding and support.

Thanks

7183.SCHEMATIC1 _ PAGE2.pdf7183.SCHEMATIC1 _ PAGE4.pdf

Hi AM,

I will reply back to you tomorrow morning.

Thank you.

Hi AM,

I reached to an expert on this part number for a better support. We are workign on it. Thanks

Hi,

Please provide your power stage circuit together with LM5034. I need to see how your power stage connected to LM5034 including secondary side circuit and feedback circuit, protection circuit. Only LM5034 is not enough.

dc.pdf

Total circuit is given. Only one section is connected.

Rgds

AM

Hi, 

Where U3 pin 8 connected?

It looks you are using high side clamping which requires low side and high side complimentary drive. LM5034 is for low side clamping which low and high side driver are in phase. You need to make inverse of high side drive signal from LM5034.

Your clamping capacitance is very large (C14, 15, 23, 24). How did you get such large clamping capacitance?

You mentioned you used UCC2897A and it works ok. Can you show your UCC2897A circuit to me also please compare LM5034 circuit to UCC2897A circuit - I do not think your UCC2897A circuit connected like your LM5034 circuit you show.

U3 pin 8 is connected to U4 pin 4 . U4 is for inverting the signal. 

ucc2897A circuit is same but both these controllers clamp drive signals are different when pulse skipping as can be seen in datasheet of UCC2897A page 22 pulse skipping. I have observed the waveform of clamp signals of both controllers when there is no pulses.

In ucc2897A aux is  high hence gate drive out is low

In LM5034  aux is low hence gate drive out is high, I think LM5034 shouldn't be used for active clamp flyback. I will try decreasing clamping capacitors.

Rgds

AM

Hi,

Ok, I see the difference. It looks LM5034 does not have a pulse skipping feature like UCC2897A which has the dedicated such a feature. So LM5034 would have to have a minimum load to keep always with duty cycle > 0.