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High Voltage DC - DC Buck Converter Chip

Hao Qin1
Prodigy 90 points

Hi All,

I want to build a DC - DC Buck converter. The input voltage is between 400v and 500v. The output voltage is 24v. I cannot find a Buck converter chip which can accept so high an input voltage (400v - 500v). Can you recommend me a chip which can accept an input voltage (400v - 500v) from TI? If TI can't provide a chip like this, can you recommend a chip from other manufacturer?

Best,

Hao

  • 0
    TI__Expert 7900 points

    Hello Hao,

    I think the reason you can't find a Buck chip to convert 400V - 500V down to 24V is because it is the wrong topology.  At 400V - 500V the switching losses (proportional to Vin) are going to be too high.  Also, 400V - 500V should probably be isolated from the 24V output for safety.  I recommend using TI's WebBench designer:  https://webench.ti.com/power-designer/switching-regulator

    I entered your Vin and Vout requirements and WeBench recommended either a Flyback or an LLC topology.  WebBench will recommend an IC and provide a complete schematic.

    Regards,

    Eric

  • 0 in reply to Eric Reicher
    Prodigy 90 points

    Hi Eric,

    Can you let me know how much output current, Iout, I can choose when I use WeBench?

    Thanks,

    Hao

  • 0 in reply to Hao Qin1
    TI__Expert 7900 points

    Hi Hao,

    I went back into WebBench and Iout range is shown at "(0A - 180A)" below the place you enter current.

    How much current do you need?  Usually, a flyback is good for up to 100W.  So, 100W / 24V would be 4A.

    Do you need that much current?  Components get much larger as current increases.  Enter whatever you need, 1A, 2A, etc.

    Regards,

    Eric

  • 0 in reply to Eric Reicher
    Prodigy 90 points

    Hi Eric,

    I use the driver ISO5852. From the similar driver from Infineon, it recommends the external gate resistor Rg = 10Ohm. The total resister is around 13.85Ohm (including internal resistor from IGBT and driver). So the current is (15V-(-8V))/13.85 = 1.66A. I need 6 ISO5852 to drive 6 IGBTs for a 3 phase PMSM. So the total current is 6x1.66A = 10.0A. I will enter the output current, Iout, as 10A. Also I observe the power is 10^2x13.85 = 1385W. It is pretty large. If I calculate a wrong result, please let me know.

    Thanks,

    Hao

  • 0 in reply to Hao Qin1
    TI__Expert 7900 points

    You are calculating DC currents, but the gate only takes current for a very short time during the switching interval.  Search the web to find references on gate charge, gate voltage, switching time, and switching frequency.  Then you can calculate a much more accurate current.  I think you probably only need 1-3A.