Analysis Of 3 Reasons For Insufficient Output Voltage Of Switching Power Supply
Apr 21, 2023| In the power supply test or application, sometimes the phenomenon of insufficient output voltage of the switching power supply is encountered. In fact, it is more common in the process of power supply development. What are the reasons for the insufficient output voltage of the general switching power supply?
1. The load current is too large
It is possible that the heavy load carrying capacity exceeds the switching power supply due to the specific output power of the switching power supply. Such as 12V3A, only 36W output power, if the load current is greater than 3A, then its output voltage will be low.
Disconnect the load, and then measure the output voltage of the switching power supply. If the output is still abnormal, the switching power supply is likely to have an internal failure; if the output is normal, connect the ammeter to measure whether the load current is too large. If the load When the current is too large and part of the switching power supply causes insufficient output power, it is necessary to replace the output current of the switching power supply. If it is before the normal output, it describes a back-end load short-circuit fault, resulting in excessive load current.
2. Low input voltage
The input voltage range of the switching power supply is wide, usually about 100V ~ 240V, the AC input voltage is abnormally low to 100V or less, this case is rare, it can be measured at the input voltage end, it is possible to contact the line difference to cause the input voltage Low.
3. Internal failure of switching power supply
No load output voltage is low or when a load is connected to normal output voltage, the voltage is low.
Generally, it has an electromagnetic interference filter (EMI), a rectifier filter circuit, a power switch, a PWM control circuit, a secondary feedback circuit, an internal switching power supply circuit for overvoltage protection, and a short circuit overcurrent protection circuit. DC is converted into 220V AC, then the PWM pulse width modulation signal is converted into high frequency AC power driver chip, switch, etc., through the high frequency output transformer, then the rectified DC voltage, the output voltage of the rectified switching power supply will be monitored in real time, through complete Coupled feedback, time adjustment when the voltage is high or low.
The output voltage of the switching power supply is low, which may be a failure of the internal circuit.