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HiperTFS used in non PFC applications

Posted by: treez on Tue, 05/04/2021


We need 140W , 100-265vac and isolated and 24v 5A. No PFC

Please show DERs that do this? (using HiperTFS)

Also, please show this using Flyback in Topswitch.

Please also show HiperTFS used without the flyback bit, and without the ">0.5 duty cycle" thing

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Submitted by PI-MrScott on Fri, 05/07/2021


Thank you for showing interest in Power Integrations' products.

While we currently do not have design example reports that meet your exact requirements, you may use the following designs as a starting point.

For HiperTFS, please check out DER-483 (

For TOPSwitch, please check out DER-204 (

You may also utilize our design tool PI Expert Online ( to further customize your designs using HiperTFS and TOPSwitch to meet your specifications.

Submitted by treez on Sun, 05/09/2021

Thanks, i see that the hi side drive of HiperTFS demands that the flyback is operating  , or that the magnetising current is redirected into the bootstrap capacitor, otherwise the hi side drive has no drive voltage.

Relying on the magnetising current to charge the bootstrap cap is ok once the converter is in steady state , but not very useful at startup......the flyback primary clamp capacitor is thus needed to initialy charge up the bootstrap capacitor for the 2TFC.

I wonder, if i dont want to use the flyback, can i just put in like a buck   bost inductor in there , with some additional circuitry ,

and charge up the bootstrap cap like that?


You may use other topologies/circuits to provide power for the bootstrap capacitor on the high-side of the HiperTFS.

The design example serves as a guide and may be revised as long as it meets the bias requirements of the HiperTFS for proper operation.

Thank you.