PMP10098: PMP10098

Hi,

Thanks for your input.

While considering calculations, do we need to consider CCM for low voltage and DCM for high voltage as it mentioned in note.

Can you provide the reference calculations for wide range input?

Thanks!

Hi Anurag,

Yes, for such a wide input voltage range the converter will have to operate in CCM for low VIN, and enter DCM at higher VIN in order to keep the magnetizing inductance in a reasonable range.

There are is no documentation for the calculations available, but you can use TI Power Stage Designer to do these calculations very easily. It will also help you adjust the specification for the new transformer.

Hi,

Thanks!

I could not understand the increasing inductance relation with change of duty cycle.

If the converter is supposed to work only in DCCM, the duty cycle is in a range from 70% down to 4% (turns ratio 3.58: 1,750µH primary inductance). To reduce component stress, you should increase the minimum duty cycle by keeping the turns ratio constant and changing the primary inductance to 4mH. The converter is now running in CCM for low-input voltages and in DCCM for high-input voltages

Reference: Power Tips: How to manage an ultrawide-input low-power flyback

Regards,

Hi Anurag,

My recommendation is to use the Power Stage Designer Tool, that I linked in my earlier reply and just use these values from the paper. You can observe how the duty cycle and current levels change based on the magnetizing inductance (1.75mH vs 4mH). By clicking on the yellow highlighted components in the topology schematic you can see the individual voltage and current waveforms.

Operating at very high and very low duty cycles can be problematic especially if transients can occur under these conditions.

Thanks!

It's useful and easy. 

I do want to know the transformer's exact turns and wire gauge at primary and secondary mentioned in EVM. Thats not mentioned in

www.we-online.com/.../750370271.pdf

Can you please help to get the details.