UCC28780: About EVM Inductor Spec & SW Frequency

Kazuki Kitajima

Part Number: UCC28780

Hello team!

I got questions from the customer. Could you please check those below?

1: In UCC28780EVM-002, If your team has a spec for the trans(Precision Incorporated / 019-8916-00R) could you please share it?

Especially we would like to know the number of turns on trans.

2: Switching frequency would change by Vin / Vout / Iout(control mode) / N(turns)?

Is there any other factor involving the switching frequency change of this device?

BR,

Kazuki Kitajima

over 4 years ago

0 Ulrich Goerke over 4 years ago

TI__Mastermind 31670 points

Hello Kazuki-san,

Thank you for your interest in the UCC28780 ACF controller.

The only transformer information that I am able to provide to you is that shown on page 19 of this document: https://www.ti.com/lit/ug/sluubo8a/sluubo8a.pdf?ts=1602211952158&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FUCC28780EVM-002

The UCC28780 operates in Transition Mode, so in AAM there is no dead-time between switching pulses.
The switching frequency is variable and is primarily influenced by Lm (not turns), Vin, Vout, and Ipk. Ipk (primary peak current) is indirectly influenced by Iout.
Ipk is regulated by current-mode control. Extended demagnetization time used to achieve ZVS also affects switching frequency, mostly at high line.

Regards,
Ulrich

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UCC28780: About EVM Inductor Spec & SW Frequency