having voltage spike problem

Thread Starter

Milad R

Joined May 11, 2019
1
Hi,
I am designing a push-pull converter.
I attached the schematic, PCB layout, Vgs, Vds and ICs voltage supply.

my problem is that I have got voltage spikes on MOSFETs.
- I have used 2 PCB layers and top layer as a GND plane.
- I have used decoupling capacitors across the ICs.
- I have used RC snubber.
but the problem still exists.
 

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Janis59

Joined Aug 21, 2017
970
Simply dU=L*di/dt where L=10 nH per cm. Thatswhy feed filter caps must be as close as possible to mosfets and must be shunted with proper fast smaller caps. If any length larger that millimeters is needed, it must be scrupulously bifillary and never longer than inch. I see the latest high-power apparatuses mostly use a two-sheet system for mounting a cap battery, its for sure better than previous star into ring mounting system or no system at all. Two sheets of copper or brass plates distanced on proper pcb or getinax in the manner, that one feet is solder on first plate via larger hole and other to next plate. As both plates are extremely near (the aim is about 0,15-0,20 mm near (as much the dielectric permit), then both plates are near-ideal bifillary lines. And this composition allows to mount mosfet "brick" straight next to the solder side, what makes those one centimeter distance realistic.
 
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