Maintenance Techniques for Switching Power Supply Voltage Without Output
The primary task of troubleshooting this type of fault is to determine whether the fault is at the switch collector, switch base, or switch tube. The specific method is to measure the collector and base voltage of the switch tube. There may be several situations:
(1) The collector voltage of the switch tube is 0V, which is 1.4 times lower than the mains voltage. The switch tube does not have normal operating voltage. If the voltage is 1.4 times, it indicates that the working voltage of the switch tube collector is normal, and it indicates that the AC220V and rectifier filter circuit are working normally.
(2) The base voltage of the switch tube is 0V (including the starting time). This indicates that the starting circuit did not provide a starting (conductive) voltage to the base of the switch tube, or that the related components between the base and emitter were damaged. The starting circuit, switch tube emitter, and related components should be inspected. If the voltage is between 0.6 and 0.7 (including the moment of startup), it indicates that the starting circuit, emitter, and components of the switch are normal. When the voltage is higher than 0.7V, it indicates that the starting circuit is normal, but the switch tube emitter junction or its components are open or the resistance 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, as well as the connection between them.
Maintenance Techniques for Instantaneous Voltage Output of Switching Power Supply
(1) False load method (2) Measure whether the protective components are damaged (3) Disconnect method (4) Reduce voltage method. The first point that must be mentioned is the strong load capacity of the Minrong switching power supply, which can be said to be achieved based on safety and pursuit. It can be said that the civilian melting switch power supply has advantages such as high efficiency, high safety, and low loss, which cannot be separated from strong contributions. Similarly, the high-quality load capacity of Minrong Switching Power Supply is inseparable from Minrong Electric's adherence to safety and the pursuit of users.
Voltage drop detection method for each functional circuit. After determining 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 a current switching power supply, one is 0. 016UF0. The fault rate of 039uf capacitor is very low and can be eliminated through maintenance. The other type is an electrolytic capacitor of around 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, the vulnerable components in the circuit formed by the working voltage of the pulse width modulation circuit can be replaced first, that is, the filtering capacitor (electrolytic capacitor from a few micrometers to 100uF), to see if the switching power supply returns to normal.
