Dual Adjustable 180V 1000W power supply

Discussion in 'General Electronics Chat' started by TheComet, Aug 22, 2013.

  1. TheComet

    Thread Starter Member

    Mar 11, 2013
    I'm baffled by some of the ludicrous requests I get...

    I need to design an isolated power supply with two output channels. The requested output voltage per channel was specified to be adjustable between 0V and 180V with 1V increments, and each channel needs to deliver 500W of power (total power would be 1000W for both channels). Total tolerance should be no more than +/-1V

    My first thought was to buy two of these suckers to isolate the circuitry from the mains:

    From there I figure the best approach would be to use some form of a PWM step-down circuitry with a PID feedback loop.

    Has anyone got any experience with high voltage/high power supplies?

    Does a complete solution in form of an IC already exist, or am I going to have to design this by myself? I searched but couldn't find anything with the specifications I need.

  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    My feeling is that your proposed transformers are about 25% underpowered for your application.

    Further their outputs are not close enough to your needs

    If you go for series secondary connection, the current rating is too low and the voltage output too high., ie your pass element would be wasting a lot of power.

    If you go for parallel secondaries the voltage output at just over 160 is too low.

    Page 398 of Gottleib gives a design for a switching regulator than can be implemented in 2 or 3 amp outputs at output voltages from 150 to 250 and powers from 300 to 750 watts, that might give you some ideas.
    Last edited: Aug 22, 2013
  3. TheComet

    Thread Starter Member

    Mar 11, 2013
    Hi studiot, thanks for the quick reply.

    If the step-down converter is efficient, this won't be an issue.

    Which book is this? I don't think I've heard of it before.

    I drew a small concept, is this the way to go?


    Small explanation: The TL494 generates a PWM signal based on the potentiometer on the very left. This signal is fed into a driver which drives a MOSFET half bridge, amplifying the PWM to 0V-315V. The resulting signal is fed through a low pass filter to provide the final output voltage. The output is fed back and stepped down again to a usable voltage by two resistors, then compared with the voltage on the potentiometer (subtraction). The result is an error, which is fed back to the PWM generator and so on.

    The PWM should regulate itself to match the required output voltage set by the potentiometer.

    The circuit is of course duplicated to provide the second output channel.

    Last edited: Aug 22, 2013
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
    My calculations suggest otherwise, or I wouldn't have mentioned it.

    You are asking for 500 watts per supply at 180 volts max.
    This implies an available current of 2.77 amps.

    So which is it 500 watts or 2 amps?

    So your transfomer is rated at 230 volts 2.17 amps.
    This will rectify and smooth to 325 volts and should be rated at 1.75 x DC current for RMS AC amps and a full bridge rectifier.

    DC amps = 2A , AC amps = 2*1.75 = 3.5A

    see here

    That is assuming a 100% efficient (switching) regulator.

    Power Supplies
    Switching Regulators, Invertors and Convertors
    Irving M Gottlieb
    Tab books

    my copy isbn 0-8306-1665-9
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009

    The smartest/most cost effective way to go is buy one (or two) power supplies that do the job.

    I spent about 30 years in power management and one thing I know to be a fact: most people think you can build a power supply for two bucks and slap an IC in it and you're done...... building a pair of 500W supplies is not trivial.
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Especially in the numbskull who ordered it expects it to be able to provide 500W at 180v AND 500W at 5v. ;)
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
  8. TheComet

    Thread Starter Member

    Mar 11, 2013
    Thanks for the help guys!