HOWTO test the overvoltage protection of a power supply

Thread Starter


Joined Sep 2, 2011
how can I test the overvoltage protection of a power supply? What kind of instrumentation do I need?

Thank you in advance!!!


Joined May 11, 2009
Are we talking about input voltage protection or output protection. Also is this a comercial power or a non comercial.
If you are going to test the input protection. I think a hipot test must be what you are looking for. Look it up with Google (hipot test) and see if it fits your needs


Joined Oct 15, 2009
hipot test is different from an overvoltage test. A hipot test typically tests basic and functional insulation to ensure isolation between current carrying conductors and the chassis/enclosure ground. Hipot is typically required as a production line test (done on every unit you produce during manufacturing before it leaves your facility)

I'm assuming you are designing this power supply and not just testing someone elses.. If so your power supply is typically required to meet certain UL (IEC,EN,etc...) standards. Those standards include the procedure or the requirements that need to be met for over voltage protection. All you "might" need is a power supply capable of the required level of voltage. Read the applicable standards.


Joined Mar 14, 2008
If you are talking about the output OV crowbar protection setting of some commercial bench supplies then you just need a voltmeter to determine the point at which the OV trips as you increase the output voltage.


Joined Aug 16, 2010
I assume this is a power supply you designed or are modifying or working on, and that you fully understand its operation. To test the output overvoltage protection circuit you need to increase the output voltage, and you need to do it in a controlled manner so you don't damage anything like output caps. An easy way to do this is to find the feedback resistors and connect a potentiometer in parallel with the lower one (the one that connects to ground). Slowly and carefully reduce the resistance of the potentiometer while monitoring the increasing output voltage. Eventually you'll reach the overvoltage threshold and something will happen (depends on your overvoltage protection circuit, it may shut down or reduce the output voltage). BE CAREFUL and make sure you calculate the feedback resistor values with your potentiometer BEFORE connecting it. If you don't know what you're doing, and you accidentally open up the feedback loop, you may see fire and sparks from your power supply!