Repair tips for switching power supply with no voltage output
The fault diagnosis methods and steps
The first task of troubleshooting this type of fault is to determine whether the fault is located at the collector of the switch tube, the base of the switch tube or the switch tube. The specific method is to measure the collector and base voltage of the switch tube. The following situations may occur:
(1) The collector voltage of the switch tube is 0v, which is 1.4 times lower than the mains power. The switch tube does not have normal operating voltage. If the voltage is 1.4 times, it means that the working voltage of the switch collector is normal, indicating that the AC220V and rectifier filter circuit are working normally.
(2) The base voltage of the switch tube is 0V (including the start-up time). This indicates that the starting circuit does not provide starting (conducting) voltage to the base of the switch tube, or the relevant components between the base and the emitter are damaged. The starting circuit, the switch tube emitter and related components should be inspected. If the voltage is between 0.6 and 0.7 (including the moment of power-on), it means that the starting circuit, emitter and components of the switch are normal. When the voltage is higher than 0.7V, it means that the starting circuit is normal, but the emitter junction of the switch tube or its components are open circuit or resistive. value increases.
(3) The switch tube has conduction conditions: the base voltage of the switch tube is 0.6~0.7V, and the collector voltage is greater than 250V, indicating that the switch tube has working conditions. The fault occurs in the positive feedback circuit, including the positive feedback resistor, capacitor, freewheeling diode and the positive feedback winding of the switching transformer and the connection board between them.
Maintenance tips for switching power supply with instantaneous voltage output
(1) False load method (2) Measure whether the protective component is damaged (3) Disconnect method (4) Voltage reduction method. The first point must be mentioned the strong load capacity of Minrong switching power supply, which can be said to be achieved based on safety and pursuit. It can be said that Minrong switching power supply has the advantages of high efficiency, high safety, low loss, etc., which are inseparable from strong contributions. Similarly, the high-quality load capacity of Minrong switching power supply is inseparable from Minrong Electric's insistence on safety and pursuit of users.
Voltage reduction detection method for each functional circuit. After judging which part of the switching power supply is faulty through the above methods, the inspection methods for each part are as follows:
(1) Check the pulse width modulation circuit and positive feedback circuit. There are two methods for replacing electrolytic capacitors in the positive feedback circuit of current switching power supplies. One is 0.016UF0.039uf capacitor. The failure rate is very low and can be eliminated through maintenance. The other is an electrolytic capacitor of about 10uF. This capacitor can be directly replaced during maintenance.
(2) In the absence of an AC voltage regulator, for overvoltage protection faults, for safety reasons, you can first replace the wearing parts in the circuit formed by the working voltage of the pulse width modulation circuit, that is, the filter capacitor (from a few microfarads) to a 100uF electrolytic capacitor) to see if the switching power supply returns to normal.
