Current limiting 500 VDC supply

Discussion in 'The Projects Forum' started by dls01454, Feb 8, 2010.

  1. dls01454

    Thread Starter New Member

    Feb 8, 2010
    I have a regulated 500 VDC power supply (actually shows 545 V on voltmeter) that we wish to use to test a DC-to-AC inverter (designed for feeding dc from solar panels into the power grid). We need a minimum of 150 mA to get the inverter to activate. Without a current limiter, our power supply just pushes as much current as it can until the 1.5A fuse (on the ac side) blows. I would like to add an external circuit to limit the current to 200 mA. Most of what I have found searching around is for much lower voltage supplies. Could anyone point me to resource or suggest a circuit?
  2. SgtWookie


    Jul 17, 2007
    Not a surprise there; to get 150mA stepped down from 545V would require about 82W power dissipation from a linear solution.

    Sounds like you need a high voltage switching supply solution. Don't happen to have one in my back pocket at the moment.

    International Rectifier has a number of application notes on their website for HV switcher applications.

    National Semiconductor might have some resources for you.
  3. eblc1388

    Senior Member

    Nov 28, 2008
    The following is a quick and dirty setup to do just that. You first need to find a N-Ch MOSFET which is rated 800V or higher and has a power PW of over 100W. The current requirement is 1A or more.

    Two additional component are needed and they are a 9V battery(can be permanently connected between source & gate as there is no current drain) and a current sensing resistor.

    The MOSFET must be mounted properly on a heatsink as the worst case heat dissipation can be as high as 90W should the output load is shorted.

    Here is a simulation of the setup. Current is the same for load of 1Ω to 1000Ω.