Input capacitor gets very hot

Ian0

Joined Aug 7, 2020
9,668
22Ω is a bit high. A good first choice is the same value as the load, about 1Ω.
The drain waveform should be a squarewave, amplitude 24V, if the transformer is correct.
 

Janis59

Joined Aug 21, 2017
1,834
1) You should check the ESR factor of this cap. Thermal flux in Watts is i^2*ESR.
2) You should parallel it with few 0.1 mkF fast caps to avoid the rapid pulses overstressing it by the di/dt
 

Thread Starter

myil

Joined May 2, 2020
145
1) You should check the ESR factor of this cap. Thermal flux in Watts is i^2*ESR.
2) You should parallel it with few 0.1 mkF fast caps to avoid the rapid pulses overstressing it by the di/dt
Can I also add a choke to avoid back emf to battery?
 

Ian0

Joined Aug 7, 2020
9,668
I don’t think it will help. The battery will get rid of the back emf!
the problem is elsewhere. Is the off-load transformer waveform clean?
 

DickCappels

Joined Aug 21, 2008
10,153
You had the wrong capacitor but that capacitor is gone now. I hope you have an idea of the ripple current so you can select a good replacement.
 

Lyes

Joined Nov 25, 2019
12
I have applied a snubber network across the mosfets according the steps in the link down below. It reduced the ringing a lot but the amplitude of the peaks still remain the same. Have any idea how to reduce the amplitude as well?

https://e2e.ti.com/blogs_/b/powerhouse/archive/2016/05/05/calculate-an-r-c-snubber-in-seven-steps
overvoltages are due to a parasitic inductance in the transformer, so it is normal to have these spikes however you must not add more with the layout

to cope you need to oversize the mosfet voltage VDss, (for 24V input a 80V mosfets should be ok)
you can increase the gate resistances but you will have more losses (heat)

using a snuber through the primary mosfets is difficult because the current is high,

the solution is perhaps to put it @ the second.
 
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