PFCLLCSREVM034: 24V/10A/240W

Hi Suman,

1. The PFC stage is basically a boost converter that creates a 400VDC bus that is typically followed by an isolated conversion stage.

2. The LLC is a very efficient isolated power conversion topology. Here is a reference design that supports your exact requirements PMP40281. This is using an older LLC and I would recommend looking at the newer LLC the UCC25661. 

3. For your 240W design, I would recommend the UCC28056 as the PFC followed by the UCC256612. Here is a WEBENCH design based for the LLC stage.

I hope this answers your questions. 

HI Suman,

To adjust the output voltage from 12V to 24V it is best to use the online excel calculators. 

Just raising the voltage is straightforward as you just need to set the divider for the TL431 to support 24Vout. Changing R24 to 310kΩ would accomplish this. However, this will double the voltage on the aux winding power powering the IC. Without clamping this, you would see an over-voltage protection (OVP) fault and the controller would shut down. If you do clamp it with a zener, you have an efficiency hit and lose the output OVP feature. 

For this reason you would need to modify the transformer. The excel calculator tools will give the parameters needed to work with a magnetics company to optimize the windings. 

I hope this helps you get started.

You're most welcome!