Help with Voltage Regulation

Power Power Supplies (off-board)
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HELP!
I have a 240 VAC Rectification Module (Switched Mode Power Supply-PSU) that outputs 53.5 VDC at up to 3000W and 56 AMPS.
My requirement is to buck down the 53 VDC “variably” to about 15-20 VDC “and anywhere in between”. I cannot use a Linear Voltage Regulator because of their practical inefficiencies, and I have not identified a ready-made Buck Voltage Regulator that “I believe” to work with the high currents involved. I’m also concerned about PWM ripple. The regulator circuity would have to control the ripple or come up with yet another module to condition the voltage after it has been bucked.
My preference is an off-the-shelf purchase, but like I said above, I was not able to identify anything already made. The Voltage Regulators, DC to DC Converters, or DC Motor Speed Controllers I see on Amazon and Ebay in the $35 range describe products that sound good, like: 60 AMPs current, 12-48VDC but their picture shows a product with very small gage wires that don’t look like they could handle the current my PSU would throw at it. Hopefully I’m wrong, and someone with more experience would say it could work, but I don’t want to waste $35 on “Magic Smoke”.
If I have to build a Voltage Regulator myself, I am game, but I would need a lot of coaching and hand-holding to overcome my lack of electronics experience.
Thanking you in advance for any and all help you provide—Thanks!
Stan

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Hi stan,

I would be very wary of $35 solutions for what you are trying to do. It is not an easy design. The odds of you successfully building your own is also exceedingly low, as this would be a challenge for people with years of experience. I’ll look into this, but no promises of a solution at this point.

Questions:

  1. Do you need to be able to adjust the voltage on the fly anywhere between 15V and 20V, or do you just need to be somewhere in that voltage range?

  2. What is your max output current requirement?

  3. You mentioned ripple; what is the maximum ripple you can tolerate?

  4. If we can’t find a solution for your input conditions, are you willing to consider an alternate solution replacing your rectification module?

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David,
Thank you so very much for your speedy reply!
In reply to your questions:

  1. Do you need to be able to adjust the voltage on the fly anywhere between 15V and 20V, or do you just need to be somewhere in that voltage range?
    A: Actually, I would like to dial the DC voltage down starting from my 53 VDC down to about 15-20VDC. A “Dial” like a POT would be ideal, but Taps at 48v, 36v, 24v, or more granular could work if I had to.

  2. What is your max output current requirement?
    A: Ideally, I would like to retain the max current of the PSU. Therefore, as I decrease the Voltage, my Amperage value should increase. I suppose that means the 3000 watts should be a constant. If that’s practically impossible, that forget I mentioned the watts part. I was talking “Ideal” and you asked.

  3. You mentioned ripple; what is the maximum ripple you can tolerate?
    A: I don’t really know. My project is not audio, but I’m not sure how excessive ripple will affect it either. I have MOSFETS flipping at a very high frequency and I can imagine ripple jacking things up.

  4. If we can’t find a solution for your input conditions, are you willing to consider an alternate solution replacing your rectification module?
    A: As a last resort. The frustrating part is the rectification module I have is designed to fit in a master cabinet that has circuitry to control the DC voltage down to 40V, but I’m using it as a stand-alone unit and it’s defaulted to 53.5VDC. I have another unit, a MeanWell 1000W that has a POT to adjust and when I got this unit I was hoping it had something similar. I even looked inside and no adjusting POTS. If I do end up replacing this unit, I think I would go for a lab power supply if I can get one with the current I need. Up to 60A is good. In the end, after I figure out what voltage works best, the plan is to wind a transformer for the exact voltage, then rectify and condition as needed. (or buy something ready made).

Thank you again, I look forward to your reply.
Stan

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Hi @stanhorvat,

Being able to output the range from 48V on down to under 20V makes it even worse than I thought. I found no DC-DC converters that can deliver anywhere near 3000W at 20V or under.

The best I have found is the Recom RBBA3000-50, which is a board-mount DC-DC that will output up to 50A anywhere from 0V to 60V. This requires very careful circuit board design and many external components must be added. Additionally, the heat produced must be dealt with, which is not a trivial matter. The output voltage it adjusted with a resistor, so a potentiometer might work. This part would require a multi-layer board with lots of copper and probably a heatsink.

A much nicer solution is to use a bench supply. Your requirements are on the upper end of what we offer, but the B&K Precision BK9117-ND comes close to meeting your needs. It can output 3000W down to 25V. Its max current is 120A, so below 25V the power is reduced. At 15V, it still delivers 1800W. This thing isn’t cheap, but it would give you a much better chance of success.

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Hi David,

Thank you for all your research. I really appreciate the effort. I think I am sufficiently convinced that strapping a Voltage Regulator onto my PSU is not a feasible option for me at this time.

Thanks again,

Stan