App note: Simulating fast transient loads for testing power supplies

Posted on Saturday, December 22nd, 2012 in app notes by DP


How to implement a fast load transient simulator for power supply testing. One of important factor of power supplies is how they react to fast changing loads. This article describes how to design a system that measures power supply performance under quickly changing loads.

To obtain fast load transients, we combine a power MOSFET and a couple of resistors right on the PC board of the device under test (DUT). Choosing the components is relatively easy. If the output voltage is positive, an n-channel MOSFET works great. The MOSFET is connected with a resistor from the source to ground (see Figure 1). The MOSFET’s gate is terminated with a 51Ω resistor to impedance-match the signal generator’s output.

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