hi everyone

I am designing a switching powersupply using TNY268 to convert AC220v to DC5v

the datasheet says to use a safety capacitor bitween +HV (primary) and GND (secondary) pins of bobbin in order to satisfy EMI standard.

but I am confused, it sounds to be dangerous bacause the DC5v would be no longer isolated.

could anyone clarify me?
what would happen if I dont use this capacitor?

 

but I am confused, it sounds to be dangerous bacause the DC5v would be no longer isolated.

This is not my field of work but searching on the NET I do find this piece of article telling you why it is needed in the circuit. More information is presented in the source.

Source for image below: primary-secondary bridging capacitor

It is there to block/reduce capacitive coupled switching noise from primary to secondary.

 

This is not my field of work but searching on the NET I do find this piece of article telling you why it is needed in the circuit. More information is presented in the source.

Source for image below: primary-secondary bridging capacitor

It is there to block/reduce capacitive coupled switching noise from primary to secondary.

Dear L.Chung

I get all info I needed about bridging capacitor from your attachment.

thanks so much