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PMP30440: Can the design of PMP30440 be used to output variable 10V to 100V?

Calvin Khoo
Prodigy 40 points
Part Number: PMP30440
Other Parts Discussed in Thread: SN6501, SN6507

Tool/software:

Dear Texas Instruments,

I'm Calvin and my team is interested in a design that provides a variable voltage of 10V to 100V, and found the design of PMP30440. In the reference design, it's used to input 24V and output 12V. With the same components, can it be used to input 200V (from a power supply) and output 100V? And input 20V and output 10V?

If there is any component change needed, my team is open to suggestions.

We look forward to your reply.

Thank you.

Best regards,

Calvin

  • 0
    TI__Expert 6005 points

    Hello Kalvin,

    What is the output current (or power) needed in your case?

    Please consider that the PMP30440, based on SN6501, is an unregulated push-pull converter.

    For example, if Vin is variable in a  range 10V - 100V, then if the transformer turns ratio is 1:1, you get ideally the same voltage that you have at the input, therefore a variable 10V - 100V output.

    If your input voltage is constant or in different voltage range, you get constant Vout.

    Please let me know some more information about the output current and the input voltage range.

    Best regards,

    Roberto

  • 0 in reply to Roberto S.
    Prodigy 40 points

    Dear Roberto,

    The output current required is at least 20mA. Allow me to clarify variable Vin, it means a power supply providing Vin, which can be tuned from 20V - 200V. An example, Vin = 20V (to achieve 10V output), it will be constant 20V until the circuit stops running, then it may be tuned Vin = 200V (to achieve 100V output) which will be for another run. It doesn't mean that the Vin changes when the circuit is running.

    If you can advise on how to control the current limit, that will be helpful too. I'm planning to use 750317331 so to get the turns ratio of almost 2:1, hopefully to help in terms of increasing the output current, does this work?

    Thank you.

    Looking forward to your reply.

    Best regards,
    Calvin

  • 0 in reply to Calvin Khoo
    TI__Expert 6005 points

    Dear Calvin,

    I understand your point about variable Vin, where the value is not changing dynamically but by applying a different voltage on the input of the power supply.

    In theory the PMP30440 can work in these conditions but the transformer 750317331 is not suitable, mainly because of too low magnetizing inductance. 

    The magnetizing inductance of a transformer, selected to work at 24Vin, will be too low for 200Vin.

    So, if you want to use PMP30440 as starting point for your design I suggest to follow these steps:

    1) Use SN6505 or SN6507 instead of SN6501; the -05 has integrated peak current limit, protecting better both internal and external FETs, and the SN6507 can be supplied at higher voltage, for example 12V; this way the VGS of Q1 and Q2 will be higher and both will be fully enhanced while being driven. With only 5V on VGS, it will be difficult to find high voltage FET that are fully enhanced.

    2) Replace Q1 and Q2 with higher voltage MOSFETs; these MOSFETs should have a voltage rating > of twice Vin_max + spike, so you will end up using FETs with 500V or 600V rating. For more choice on the selection of these FETs, I suggest to use SN6507.

    3) Supply the VCC of SN650x with a linear regulator. Of course, having Vin = 200V and supplying 5V on VCC will be lossy, so I suggest to calculate properly the losses

    4) Most important: calculate the magnetizing current according to the guidelines described in SN650x parts; probably you will end up a transformer with 5mH...10mH inductance, which will have high RDC resistance and high conduction loss, unless you use a pretty big transformer.

    I hope my description helps.

    Best regards,

    Roberto