Capacitorless snubber circuit

Thread Starter

Blue_Electronx

Joined Jun 10, 2019
105
Hi,

Looking into the reference design below, I notice the snubber for the flyback transformer only has two diodes and a resistor. I always had seen snubbers with a capacitor. How do I design this kind of snubber and what tells me when to include a capacitor or not?
 

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ericgibbs

Joined Jan 29, 2010
10,054
hi BE,
Note one of those diodes is a 110V Zener, when used in this circuit, it slows the inductors back emf current decay.
E
 

AlbertHall

Joined Jun 4, 2014
9,875
hi BE,
Note one of those diodes is a 110V Zener, when used in this circuit, it slows the inductors back emf current decay.
E
It slows the decay compared to just a reverse diode to limit the reverse voltage to 1V, but the zener means the back emf will be allowed to reach 110V and the decay will be faster.
 

ericgibbs

Joined Jan 29, 2010
10,054
hi A,
You are correct.
I was casting my mind back to punched paper tape days, we added zener diodes to the punch pin solenoids in order to decrease the pin release/extraction time, so that tape transport could increment the tape without the pins snagging the tape.

E
 
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