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Some info on "150W" DC-DC Step up converters from ebay — Parallax Forums

Some info on "150W" DC-DC Step up converters from ebay

CuriousOneCuriousOne Posts: 928
edited 2015-06-28 13:16 in General Discussion
I'm talking about these:

(mine came from different seller, they are currently out of stock, but appear to be the same).

Some warnings again:

1. Forget about "150W", more realistic are up to 20W without cooling and up to 60W with forced air cooling.
2. There are some errors in circuitry that prevent proper operation at low output currents.
3. Theres "oversensitive" soft start that limits usability
4. Output has high transient spikes.
5. There's no short circuit protection.

Some of these issues can be user fixed to some extent:

1. Remove silicone pads from MOSFET and diode heatsinks, use some thermal grease and insulate heatsink from base.
2. Remove the 100n capacitor between pin 1 & 2 and replace it with 220pf capacitor with 47k resistor in parallel
3. Add 470pf capacitor from #3 pin to GND.
4. Add 0.1uf ceramic capacitors to output and input capacitors in parallel.
5. Sorry no idea about that.

The good idea is that this step-up converter has "built-in" current limiter, so it can be used as LED driver, motor driver, etc. To implement this feature, you will need to play with values of 100k and 1k resistors, connected to pin #3. I'm currently analyzing this "feature", so will post updated info ASAP.

I've heavily modified the circuit, added flyback transformer, snubber circuit, etc. Currently it outputs 310VDC @ 0.2A, consuming 7.5A @ 12VDC, which is not bad. It also offers good voltage stability - rapidly changing consumed power from 0.01A to 0.2A gives only momentary voltage sag by 5V, not more.


  • Duane DegnDuane Degn Posts: 10,543
    edited 2015-06-27 15:46
    Is the boost regulator you linked to the same kind you're using to output 310VDC?

    The listing states the maximum output is 35V. Is this a different regulator?

    Thanks for the information.
  • Heater.Heater. Posts: 21,233
    edited 2015-06-27 16:21
    CuriousOne said "I've heavily modified the circuit, added flyback transformer, snubber circuit, etc." That is how he got 310v

    Actually CuriousOne, could you show us details of those additions? I need to get up to 1000v at a few milliamps.
  • User NameUser Name Posts: 1,451
    edited 2015-06-27 21:26
    What would you be doing with 310 VDC @ 200mA? An old-school audio amplifier?
  • CuriousOneCuriousOne Posts: 928
    edited 2015-06-27 22:41
    OK, here's the original circuit (drawn not by me, found by googling). Actual builds might differ slightly - mine has different mosfet and output diodes.


    I'll draw my modification circuit and upload it later.

    Getting 1000VDC @ few milliamps does not require such a big circuit, you can easily go with LM2586 or LM2588, will occupy less space and use far less external components.
  • CuriousOneCuriousOne Posts: 928
    edited 2015-06-27 22:45
    And for proposed usage - my modified circuit, using 4 pcs high current IMR18650 Li-Ion batteries, recharges a bank of 350v 5800uf capacitors just under 3 seconds :)
  • ercoerco Posts: 20,158
    edited 2015-06-28 06:25
    Nicely done, CuriousOne! Really like your proactive mod & share approach with updates. You're walking the walk, IMO exactly as it should be in this forum. Seems like there's been more talking than doing here lately and I for one appreciate your efforts and experiments. It's a plus if you burn up or blow up some stuff along the way. :)

    Edit: Matt, where's the contest you promised? Time to liven up this joint. Make it something hardware related. People have to SOLDER something together. Even if its blowing up capacitors for July 4.
  • tonyp12tonyp12 Posts: 1,950
    edited 2015-06-28 12:58
    What do you need the 100v to do?, pwm it?
    Here is a 3-5V to 100V Boost chip with pwm control:
  • CuriousOneCuriousOne Posts: 928
    edited 2015-06-28 13:16

    Here's complete circuit with modifications:


    The transformer used is 1:10 turns ratio, so in theory, it shoud allow up to 1200VDC output. I haven't tried above 750v, since my multimeter can't measure higher voltages.
    It also should be noted that output diode used is overkill for that circuit, I just used what I had on hands, you can use any other ultrafast diode, 3A should be enough.
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