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UCC21520: H-Brige PWM DC to DC converter using UC2526 and Driver UCC21520 IC

Jaya kumar
Prodigy 140 points
Part Number: UCC21520
Other Parts Discussed in Thread: UC2526, UCC20225

Hi 

I am Using UC25256 for PWM generation and Ucc21520 for PWM driver for my H-bridge Topolgy it is fully anolog control i can get PWM variation by varying E+ pin of UC2526, by Giving Resistive Load i get PWM variation by adjusting thr Voltage at E+ Pin of UC2526 (pin no 1), But if we connect the transformer at H-bridge the PWM goes directly to maximum by adjusting E+ Volatge PWM variies in input side but not reflected in transformer PRimary and secondary side kindly provide your guidence to resolve it.

Jayakumar.N

  • 0
    TI__Intellectual 2061 points
    Hello Jayakumar,
    Thanks very much for your information.
    Are you referring the OUTA/B is not following the INA/B. Could you please help me on your schematic design and some critical waveforms? so that I could digest and help you more.
    I look forward to your feedback.
    Wei
  • 0 in reply to Jaya kumar
    Prodigy 140 points
    Hi Wei

    Thanks for reply,I Have done testing with with voltage for the H-Bridge (30V to 400V), the PWM variation is not happening when transformer is connected to H-bridge, if any inputs required let me know

    Regards

    Jayakumar n
  • 0 in reply to Jaya kumar
    Prodigy 140 points

    Hi Wei,

    Any Updates Please,

    I have tested further but the results reamins same can please help to resolve

  • 0 in reply to Jaya kumar
    Prodigy 140 points
    I have Tested the Ckt again and Observed PWM Variation when the transformer is connected as PWM amplitude is 12V, a small step of 2V from the top the Amplidute is varying not the Entire 12 Amplitude, i.e PWM variation noticed only 2V amplitide only

    Kindly helps us to resolve this issue
  • 0 in reply to Jaya kumar
    TI__Intellectual 2061 points

    Hello Jaya, Thanks very much for your patience. and sorry for the late reply due to US holiday.

    Appreciate a lot for your kind information. There are quite a lot of information in the slides. and I would like to ask a few questions to confirm my understanding.

    1. UC2526 is sending correct information as you programmed, and the waveform looks clean (Page 6 in the slides). Could you please confirm?

    1.1  is this waveform shown in Page 6 tested when the high voltage is 0V?

    1.2 Do you mean the max dutycycle works fine, I see the wavefrom in page 5, at lower right, seems good.

    2. Is your question majorly focusing the Min PWM, the waveform shown in upper right on page 5?

    3. Are you floating DT and DIS pin of UCC21520? if so I would recommend. For better noise immunity, please ground DIS and parallel a >2.2nF capacitor close to the DT pin.

    I look forward to your feedback.

    Wei

  • 0 in reply to Wei Zhang
    Prodigy 140 points
    Hi Wei,
    Thanks for the reply.

    i have few doubts on my schematics, which i have send already,can please check it once again.

    i have PWM problem only when transformer is connected i.e gate PWM varies but PWM at drain remains always 44 to 49%(Gate signal dost control Drain)

    This might be due to open condition of each switchs in OFF time as well as in dead time am i right ?

    can please check the topology is correct or not ?

    Thanks
    Jayakumar.N
  • 0 in reply to Jaya kumar
    TI__Intellectual 2061 points
    Hello Jay,

    As what you said, I also believe it is related with deadtime, zero voltage switching, etc. with resistive load, the VAB (mid point of the half bridge) is zero with you switch the fets off. However, when you switching with the transformer, then the leakage energy and magnetizing current kicks in which may leading to diode freewheeling, and small dutycycle will very likely have hardswitching, which means there will be capacitor charge/discharge and reverse recovery (SiC MOSFET body diode performance is not good).

    Therefore, I suggest we shall understand the power stage and the gate driver first.

    For understanding gate driver, i suggest we run open loop with monitoring the gate driver input and output and I would like to see whether the driver works properly or not. Please make sure your DIS is grounded if not used.

    A few suggestions on waveform: 1) INA/INB-GND; 2) OUTA-VSSA (Differential probe); 3)OUB-PWR_GND (for function test, you can short GND and PWR_GND); 4) ISO +12_V (VDDB) ; 5) VDDA-VSSA (Differential probe).

    I look forward to your reply.

    Wei
  • 0 in reply to Wei Zhang
    Prodigy 140 points
    Hello Wei,

    Sorry for my delay response, actually i have checked the whole setup only in open loop, For your information please, if we take Invert er A-PWM and B-PWM means the ckt function properly, but when signal is stopped by UC 2526 means the bottom 2 switch always ON due to inversion added before UCC21520 driver IC.i tried to sync 2, UC2526 IC , initially its happening but frequent ON /OFF the PWM goes out of phase which cause Switch failures.Kindly suggest how to sync 2 nos IC UC2526 ( i did as per datasheet info but not happening properly) or how make invert er A -PWM and B-PWM or else whether pulse transformer will work well ?

    Thanks
    Jayakumar.N
  • 0 in reply to Jaya kumar
    Prodigy 140 points
    Hi Wei,

    Can you give any reference ckt using UC2526 in full bridge topopgy (not using MCU)
  • 0 in reply to Jaya kumar
    TI__Intellectual 2061 points

    Hello Jaya, Thanks very much for your information. I will loop in UC2526 experts to help you more.

    Wei

  • 0
    TI__Intellectual 1550 points
    Hi Jaya,

    Sorry that we don't have reference design for UC2526.

    I see in the slides that the PWM control signals look correct. How about the gate driver outputs? Can you share the waveforms?

    Can you clarify the following statement which is a bit confusing,

    "
    When transformer is connected to H-bridge the PWM go Maximum at minimum PWM the waveform goes as sine wave 50Khz

    "


    Regards,
    Wangxin
  • 0 in reply to Wangxin Huang
    Prodigy 140 points

    Hi WangXin,

    I have used PWM-A and PWM-B from UC2526 to drive UCC21520, hence UC2526 do not have complementary PWM-A and PWM-B, i.e PWM A and PWB are equal in duty, so this unable to drive when a transformer is connected i am right ?, if any invert er is used for Bottom drive Switch its works fine.

    Kindly suggest your though, if you have PWM driver similar to UC21520 with Single Input slimier to  UCC20225 4-A, 6-A, 2.5-kVRMS Isolated Dual-Channel Gate Driver with Single Input in LGA, but Working voltage is 700V only we required 1200V same ratings of ucc21520

    Thanks

    jayakumar.N

     

     

  • 0 in reply to Jaya kumar
    TI__Intellectual 1550 points
    Hi Jayakumar,

    Can you run you board in open loop and capture the waveforms for PWM-A, PWM-B and outputs of the UCC21520? That would help us troubleshoot the issue.

    Regards,
    Wangxin