A DC power supply is a device which transfers AC main power to a required DC output V/A/W rating. A good power supply should be reliable, meet all required functional specifications, full protection features, safety and Electromagnetic compatibility requirements. This application note is focusing on the testing of functional specifications and protection features.
Power supply testing methods for design, production, and quality verification require sophisticated electronic equipment. Different power supply configurations and output combinations also dictate the need for versatile test instruments that can accommodate a broad range of specifications.
Prodigit 3300 series Mainframe, 3310/3320 series Electronic Load Module, and 3600A power supply testers provides programmability, friendly operation, reliable test results, efficient testing and high testing quality at a minimal testing cost. Those instruments have been broad used to test the function of power supply by known manufacturer worldwide.
Following are functions typically tested when qualifying a switching power supply.
Hold on adjust
Ripple and Noise or PARD
Input Power and Efficiency
Dynamic load or Transient load
Power Good/Power Fail (Power Good Signal)
Over Voltage Protection (OVP)
Over Current Protection (OCP)
Short Circuit Protection
1.1 Hold on adjust/set output voltage
When manufacturing switching power supplies, the first test step is to adjust output voltage to within a specified range. This is done first to ensure further specifications are met. Normally, the AC line voltage is set to nominal and the Dc output current is set to a nominal or a maximum load current in the HOLD-ON adjust procedure. The DVM measures the power supply's output voltage, and adjusts the potentiometer until the voltage reading is within the required limit.
1.2 Line Regulation
Line regulation is defined as a power supply's ability to provide a stable output voltage under conditions of changing input line voltage.
To accurately measure line regulation, the following equipment is required:
a. A variable line source capable of providing at least the minimum to maximum input range of the power supply to be tested.
b. A true RMS voltmeter to monitor the input source voltage.
c. A precision DC voltmeter with an accuracy at least 10 times better than the regulation of the unit under test.
d. A variable load for output.
Typically, the equipment is set up as shown below: