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UCC29950: UCC29950

herry ran
Prodigy 10 points
Part Number: UCC29950
Other Parts Discussed in Thread: UCC28180, UCC256403

The PFC part has been debugged separately in recent days, but other parts have not been welded.

When the PFC is started for the first time, the PFCGD can also see 100kHz waveform, and there is no response when it is opened again.

The multimeter tests that the PFCGD is short circuited to GND (Pin1) of power ground, but not to AGND (pin6) of signal ground; Later, when the PFCMOS was removed and replaced with a new UCC29950, the PFCGD waveform did not respond. After the power off and discharge, the PFCGD was still short circuited to GND (Pin1). When the PFCGD was measured again after a period of time, it was normal, but there was no PFCGD waveform.

At present, the GND of AGND is connected by a 0R resistor.My current sufs and MD_ SEL/PS_ On is directly connected to VCC, and VCC is provided by a separate small board, sufg and AD_ Det is not connected with any components, and the small power supply board is not used for power supply in the debugging process. It is an external DC power supply.In addition, what are the layout requirements of IC signal ground and power ground?

At present, I use a 0r resistor to connect, is GND (Pin1) to the electrolytic capacitor ground first or agnd (pin6) to the electrolytic capacitor ground first?

  • +1
    TI__Genius 9790 points

    Hi, Harry

    Could you share the waveform of PFCGD when it is normal? did you see over voltage on PFCGD pin?

    Regarding to UCC29950, it doesn't have drive capability on PFCGD pin and LLC drive pin, you need to add external driver which increase system cost. TI has upgraded PFC and LLC controller than UCC29950, Could you list your spec? Then I can recommend the suitable solution based on your spec. 

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Prodigy 10 points

    Vin: 90~277Vac, Vo max.: 56Vdc, Io: 12.5A（constant current）, and the output has dimming function.thanks very much!

  • 0 in reply to herry ran
    TI__Genius 9790 points

    Hi, Herry

    I recommend UCC28180+UCC256403 for PFC+LLC stage, you can keep the auxiliary power unchanged.

    Below is 500W reference design for CC/CV application. You can start to use UCC28180+UCC256403 with this reference design.

    https://www.ti.com/tool/PMP40766

    Yunsheng

  • 0 in reply to HY yang
    TI__Genius 9790 points

    Hi, Herry

    The switching frequency is 100kHz, but the waveform of PFC drive signal has very long pulse which is abnormal, since the maximum duty is 92%. Can you see the waveform with different UCC29950?

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Prodigy 10 points

     I can't see other waveform.I can see that the PFC frequency is about 100kHz, but the PFC is not boosted to 400V.Or is there something wrong with the parameters around my ucc29950?

  • 0 in reply to herry ran
    TI__Genius 9790 points

    Herry,

    have you tested VCC of UCC29950? Is the VCC stable?

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Prodigy 10 points

    My VCC is from DC source!

  • 0 in reply to Yunsheng Qu
    Expert 1980 points

    At present, VCC is powered by external DC power supply of 16V, which is a stable voltage.

  • 0 in reply to HY yang
    TI__Genius 9790 points

    Hi，HY

    Could you check the schematic of PIN 4,5,7 which is critical to UCC29950?

    I want to highlight the solution I recommended at the beginning of this thread? We have better solution than UCC29950 and we can support that solution better than UCC29950 since UCC29950 is very old part.

    Yunsheng

  • 0 in reply to Yunsheng Qu
    Prodigy 10 points

    We will consider your plan for the next 800W project, but we have 3K ucc29950 in stock. We need to debug this project first. Thank you!

    The 2, 4 and 7-pin circuits you mentioned are shown in the figure above. Please help. Thank you!

  • 0 in reply to Yunsheng Qu
    Prodigy 10 points

    This IC support 300 ~ 400VAC input voltage?

  • 0 in reply to herry ran
    TI__Genius 9790 points

    Hi, Herry

    UCC29950 doesn't support 300~400VAC input voltage, it only support 85V~264Vac, there are many parameters are fixed inside, like the resistance of AC1/AC2 pin.

    Yunsheng