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Measure load regulation to ensure that power supplies meet specs

Posted by Bill Martin on Mar 31, 2015 9:49:26 AM

One of the most important specifications for a DC power supply is load regulation. Load regulation is a measure of how well a supply maintains its output voltage when the output current changes. Good load regulation will help ensure that the power supply will deliver the voltage your circuit or system needs.

When specifying or purchasing a DC power supply, you may want to not only read the data sheet for the particular power supplies that you are considering, but also run some tests to make sure that they meet spec.

Normally, this effect should be very small. The Sorensen HPD Series, for example has a load regulation of 0.01% of Vmax + 2 mV.

There are several ways to measure the load regulation of a DC power supply. Perhaps the simplest way is to select load resistors that will present the minimum load, the maximum current, and nominal load (half the maximum current) to the power supply. Connect them one at a time to the output terminals of the supply and measure the output voltage.

When measuring the voltage, connect your voltmeter to the SENSE terminals and not the output terminals, as shown in Figure 1. This is very important as it will eliminate the error that can be caused by the voltage drop between the power supply's output terminals and the load. This voltage drop can be significant when the load current is at the maximum.

Connecting the voltmeter to the sense terminals will prevent measurement errors caused voltage drops in the output leads. Connecting the voltmeter to the sense terminals will prevent measurement errors
caused voltage drops in the output leads.

Once you have made these measurements, you can calculate the load regulation:

%load regulation = V (full load) -V (minimum load) / V (nominal load) X 100%

Another way to provide a load for this test is by using an AMETEK Programmable Power electronic load. The use of an electronic load makes it very easy to check the load regulation across the entire output range of the power supply. Whichever method you use to provide a load, make sure that the load can handle the full output power of the power supply.

Topics: DC Power-Supplies

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