How to measure several voltages in a switching power supply?
Voltages at key points of the switching power supply are.
AC input voltage, single-phase AC 220V.
DC bus voltage, single-phase AC 220V rectified and filtered to DC 310V voltage.
If the switching power supply is a power management chip class, such as the UC3844 power management chip pin voltage is also a key point voltage, such as its 7 feet 15-18V, 8 feet of the reference foot standard 5V, as well as its 1 foot, 3 feet, 4 feet, 6 feet are also key point voltage.
Switching power supply output voltage, this example output voltage is 5V and 16V.
How to identify and measure the key point voltage
AC single-phase power supply voltage 220V and DC bus 310V voltage of these two power supply voltage, AC input power supply voltage naturally needless to say, directly with the multimeter AC file to measure, DC bus voltage with the multimeter DC file, take the red table pen on the DC bus electrolytic capacitor positive, black pen on the negative side of it, so that you can measure the DC bus voltage.
Power management chip pin voltage is measured with the multimeter DC voltage gear, the black pen in the UC3844 5 feet, the red pen in order to measure the order of 7 feet, 5 feet, 4 feet, 6 feet, 3 feet, 1 foot of the voltage. Among them, 4 feet, 6 feet with an oscilloscope to measure the output waveform, unconditional pointer can be used to view the pointer swing into a certain pattern.
Switching power supply two output voltage 5V, 16V, switching power supply if there is an output voltage marking directly with the DC file measurement, if there is no marking on the secondary output circuit of the switching power supply electrolytic capacitance as the identification of the basis for the electrolytic capacitance of the high voltage is 16V output, low voltage for 5V output, such as 16V output circuit electrolytic capacitance of 35V470UF, 5V output circuit electrolytic capacitance of 16V1000UF, here is a good idea. 16V1000UF, here with a digital meter do not distinguish between positive and negative capacitance, and do not distinguish between red and black pens directly measured capacitance two feet is the output voltage.
How to identify the working state of the switching power supply
-If you measure the switching power supply two no voltage output, and then the multimeter DC file into the range of the smallest DC file and then measured, if the output voltage is very weak, that the switching power supply vibration, power supply failure or load failure. If disconnect the switching power supply load, the switching power supply output is still zero output, then the output circuit is seriously short-circuited. If the output circuit is seriously short-circuited, the switching power supply is not vibrating at all.
Disconnect the switching power supply and immediately measure the DC bus voltage of the switching power supply, and measure the DC bus filter capacitance with DC gear, if the voltage decreases slowly and linearly, it means that the switching power supply is vibrating, if the voltage decreases slowly and linearly, it means that the switching power supply is not vibrating. That switching power supply vibration, if it can maintain the 310V voltage for a long time can not be reduced is not in the power supply vibration state. Note! Do not vibrate the switching power supply After the power failure, there is still high voltage, the operation must wear gloves.
