Common faults of power adapters
Fuse blown
Generally, a blown fuse indicates that there is a problem with the internal circuit of the power supply. Since the power supply operates at high voltage and high current, the fluctuation and surge of the grid voltage will cause the current in the power supply to increase instantly and cause the fuse to blow. The focus should be on checking the rectifier diode, high-voltage filter electrolytic capacitor, inverter power switch tube, etc. at the input end of the power supply to check whether these components are broken down, open circuit, damaged, etc. If the fuse is indeed blown, you should first check the components on the circuit board to see if the appearance of these components is burnt or if there is any electrolyte overflow. If the above situation is not found, use a multimeter to measure whether the switch tube is broken down and short-circuited. It should be noted that: when a component is found to be damaged, it must not be directly turned on after replacement. In this way, it is very likely that other high-voltage components are still faulty and the replaced components will be damaged. All high-voltage components of the above circuits must be fully inspected and measured before the fuse failure can be completely eliminated.
No DC voltage output or unstable voltage output
If the fuse is intact, there is no DC voltage output at all levels under load. This situation is mainly caused by the following reasons: open circuit and short circuit in the power supply, failure of overvoltage and overcurrent protection circuits, failure of auxiliary power supply, failure of oscillation circuit, overload of power supply, breakdown of rectifier diode in high-frequency rectifier filter circuit, leakage of filter capacitor, etc. Then use a multimeter to measure the secondary components. After excluding the breakdown of high-frequency rectifier diode and load short circuit, if the output is zero at this time, it can be confirmed that there is a fault in the control circuit of the power supply. If there is partial voltage output, it means that the front-stage circuit is working normally, and the fault is in the high-frequency rectifier filter circuit. The high-frequency filter circuit mainly consists of a rectifier diode and a low-voltage filter capacitor to form a DC voltage output. The breakdown of the rectifier diode will cause the circuit to have no voltage output, and the leakage of the filter capacitor will cause faults such as unstable output voltage. Use a multimeter to statically measure the corresponding components to check the damaged components.
Poor power load capacity
Poor power load capacity is a common fault, which usually occurs in old power supplies or those with long working time. The main reasons are aging of components, unstable operation of switch tubes, and failure to dissipate heat in time. It is important to check whether the voltage regulator diode is heated and leaking, whether the rectifier diode is damaged, and whether the high-voltage filter capacitor is damaged.
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