UCC256302: Dead time inquiry

Hi James,

Thanks for your interest in UCC256302. This controller uses adaptive dead time where the total dead time is dependent on the slew rate of the switch node voltage. What is the resonant frequency your customer is trying to achieve?

Best Regards,
Ben Lough

Hi Benjiamin,

Thanks for the explanation. My customer is using 500k right now, and they want to achieve a higher frequency.
By the way, do you have the details of how UCC256302 adaptively change the dead time according to the slew rate of the SW voltage.

Thanks.
James

Hi James,

The controller looks at the slew rate of the switch node. When one gate is turned off, the switch node begins to slew to the other rail (either to Vin or to gnd). It looks for a slew rate of at least 1V/ns. Once the switch node finishes "slewing" to the other rail, the controller turns on the next gate. There is some propagation delay between the controller sensing the switch node has finished slewing and the actual turn on of the next gate. Typically we recommend a max resonant frequency of ~350kHz for this controller.

There are a couple things you can try:

1. speed up the turn off of each MOSFET

2. Remove any snubbers connected to the switch node and use MOSFETs with low Coss.

3. Use a lower magnetizing inductance.

Best Regards,

Ben Lough