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UCC24624: No drive waveform, from no load to full load

Jack Deng
Expert 1090 points
Part Number: UCC24624
Other Parts Discussed in Thread: UCC24612

Hi Tiers:
I'm using the UCC24624 in my 24V10A AC/DC power supply project,

but i find UCC24624 has a samll issue:

when the load change form no load(24V0A) to full load(24V10A), the SR controller UCC24624  VG1/2 don't have the driver waveform, and the power supply into the diode rectifier mode,

I have to restart the AC input,  UCC24624 can work properly,

below is the SCH, could you please give me some advice, thx

BTW:1.  I have a AUX, the VCC is normal.

2, the LLC controller is L6599, Can UCC24624 match with ST solutions?

I look forward to receiving your reply soon, thanks.

  • 0
    TI__Guru* 86236 points

    Hello Jack,

    The UCC24624 works on sensing the Vds of the output rectifiers with an LLC and senses body diode conduction and voltage developed across the FETs Rdson while they are conducting.  So this device should be able to work with any LCC controller.

    I reviewed the schematic and see that VSS has 470 ohm to ground (R411) which is meant to be used to prevent premature turnoff the FETs.  If this is not setup correctly it can cause the UCC24612 to misbehave.  The customer could try replacing R411 with a short.

    The data sheet application section recommends that the resistors between the FET drains to VD1 and VD2 pins be 1K ohm.  Your design has 10 ohms, you might want to increase these to 1k ohm improve noise immunity.

    The secondary FETs are switched into zero current I believe.  You should not need fast turnoff circuits formed by R403, D401 and R406 and D402.  So you might remove these from the design to save money.

    Some times ringing on the drain pins can cause misbehavior of the SR driver.  This ringing can be dampened with and RC snubber across the drain and sources of the FETs.  The User's guide for the UCC24624 EVM describes how setup this RC snubber on page 6 of the user's guide.  The following link will get you to the UCC24624 EVM user's guide.

    Regards,

  • 0 in reply to Mike O'
    Expert 1090 points

    thanks for your support,