Ir2153

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Hi.
I want ti build small half-bridge smps ( offline ) based on IR2153. I saw few schematics here on the forum ( and here, and here ) and have some questions:
- Oscillator frequency for IR2153 is Fosc ~ 1/(1.4xRtxCt). But, what is switching frequency ? Is it equal to Fosc, or is it 1/2Fosc ?
- Do I need small inductor in series with primary of output transformer ? What is the value of this inductor ? It probably depends on primary leakage inductance of transformer, but need to know how to choose proper value. Do I need snubber for it ?
- I never saw somebody using fast diodes in gates of switching transistor ( parallel with gate resistors ) - for faster turn off. Can I add them, or there is some reason because nobody using them ?
 
In this case Osc Freq is same as SW Freq.......

Using diodes anitiparallel with gate resistors is a good approach....for fast turn-off

The inductor is used for quasi resonance mode for low emi generation i.e. soft switching.....
 
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