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Questions about flyback smps

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saurav_sdpl

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I have a question for flyback smps.
1.What exactly the dots indicate in transformer, and their significance.

Secondly if i see the voltage at the secondary terminal during switch on time, whether it will be zero or be having some value.
 

Re: flyback

Dots indicate the starting point of the windings in transformer.Its used to identify the primary-secondary phase differences in the ckt.
Normally output wont be zero when you turn on.You cud find some voltage.
 

Re: flyback

Dot indicate the starting point or ending point of a winding.

The secondary output wont be zero. Normally will connect a diode on the secondary to block the voltage when the switch is on.
 

Re: flyback

If the switch is continuous ON without turn off, then secondary output will be zero. Tranformer will act as inductor only.
 

Re: flyback

if the switch is contnously ON,then the tranformer wont be left out to act even as an inductor.Primary is short!
 

Re: flyback

Off course we know that if apply DC across inductor like a short circuit....because very resistance of the coil.
 

Re: flyback

During the switch on time you will see a voltage at the secondary windings, which will be simply the input voltage times the turns ratio, but the polarity will be reversed compared to that during the off time.
This happens because transormer action exists always, you cannot cancel it. The same applies during the off time: the voltage you see across the secondary winding will be reflected to the promary with the reverse of the turns ratio and will appear on the transistor' s collector/ drain as a pulse higher than the input voltage.
 

flyback

dot indicates that current enter in that way i e starting point of current in that winding
 

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