Hi,

Here is a schematic :


The question is the following :
This is the output stage of a foward converter and as you can see there is an electrolytic capacitor for filtering the output voltage. Nevertheless, it usually recommanded to use a capacitor with a low ESR (equivalent serie resistance). In my mind, an electrolytic capacitor has a high equivalent series resistance and this is pretty bad for having low output ripple. So why there is an electrolytic capacitor ?

Thank you and have a nice day !

Léo

 

Hi,

What is the purpose of the components circled in red ?



Thank you and have a nice day !

Léo

 

Because only the electrolytic capacitor can provide 1000μF = 1mF of capacity. Also, notice that they use four 33μF capacitors in parallel for lowering ESR.

 

What is the purpose of the components circled in red ?

I'm not a power converter specialist but it looks like some "strange" version of an RCD clamp circuit to protect the output synchronous rectifier MOSFET (Q2,Q3 , Q8).

 

Thank you for your reply.

You mean that the voltage accros the inductor could be very high during switching off time of the two MOSFET and break the MOSFET. It seems to make sense ! There is actually a certain time which is programmed during which the two MOSFET are OFF