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UCC256301: UCC25630 Function check

Kuo John
Expert 1075 points
Part Number: UCC256301
Other Parts Discussed in Thread: UCC25600, UCC28056

Hi Team

Looks 25630 has good feature about no add external standby power?
1. mean UCC25630 optimise burst mode, so UCC25630 allow not shut down LLC and PFC to meet power saving, right?
2. May I know why Apapter/TV monitor usually need external Flyback provide standby power?
3. Compare UCC25600 and UCC25630 VCC bias method. May I know UC25600 use external auxiliary winding can have same performance?

  • 0
    TI__Expert 7260 points

    Hi Kuo,

    1, With UCC25630 and its partner UCC28056 (PFC controller, coming soon), they can meet the extreme low standby power requirement without shutting down.

    2, When PFC+LLC shut down, you still need to provide power to some standby circuit, for example, the remote control (infrared) receiver, this is done by a flyback converter.

    3, UCC25600 has no internal high voltage start up circuit, an external bias is a must.

    Regards,

    Bosheng

     

  • 0 in reply to Bosheng Sun
    Expert 1075 points

    Hi Sir,

    I have question about TI 28056 and 25630.

    1. May I know 28056 with 25630 start up sequence? Looks TI's LLC first up than provide VCC for 28056 by RVCC.
    2. May I know 25630 can High Voltage start up at input 90VAC? And how make sure LLC output stable than provide RVCC for 28056?
    As tradition PFC with LLC. Usually PFC already 380VDC - 420VDC Bulk voltage than LCC start work. avoid capacitive region and wide VIN cause LLC unstable.

    3. May I know 25630 can setting minimum switch frequency avoid control mode into capacitive region?
    Compare our competitor L6599 and HR1001 have.
    a. L6599 f(min) setting.
    b. HR1001B f(min) can setting and has I Polarity protection.
    c. 256301 has I Polarity protection, but not f(min) setting, Why?

    Regards,
    John

  • 0 in reply to Kuo John
    TI__Expert 7260 points
    Hi Kuo,

    1, The start up sequence is: When AC is plugged in, UCC25630 internal JFET is turned on and starts to charge the VCC capacitor. Once the VCC pin voltage exceeds its threshold, UCC25630 internal LDO turns on and generates 12V on RVCC, this will turn on the UCC28056 and PFC. When PFC output voltage reaches a certain level, LLC is turned on. When LLC is operating, the LLC transformer bias winding will supply bias current for both UCC28056 and UCC25630
    2, Yes, UCC25630 can start up at 90VAC, then PFC start up, and last LLC start up.
    3, The minimum switching frequency of UCC25630 is 35KHz. UCC25630 has capacitive region avoidance scheme to prevent ZCS, please check section 7.3.14.1 in the datasheet for more details. There is no need to set f(min) for this purpose.

    Regards,
    Bosheng