Maintenance method of inverter switching power supply
1. Check whether the rectification circuits D1-D4 have broken down or whether the capacitors of the filtering circuit are damaged, whether the balance resistors R1 and R2 are normal, and whether the voltage reducing resistor R3 has burned out or increased resistance value and failed (tested under power-off conditions).
2. Check whether there is a breakdown or short circuit in the b-e and c-e junctions of the switch tube, and measure whether there is a short circuit in each winding of the switch transformer to determine the quality of the switch tube and switch transformer (tested under power-off conditions).
3. Check the rectification and filtering components of the secondary output winding, with a focus on whether the filtering capacitor is bulging or damaged, to eliminate the possibility of a short circuit in the secondary circuit.
4. Check whether the absorption circuits D5, R11, and C9 are normal (test under power-off conditions).
5. After confirming that the above components are normal, we can remove the switching power board from the frequency converter and conduct a separate power test on it. Slowly adjust the rated voltage of the switch power supply with a voltage regulator. At this time, you should be able to hear the squeaking sound of the transformer when it starts to vibrate. If you do not hear the vibration sound, use a multimeter to check whether there is a DC voltage of about 12V-16V between the positive and negative stages of the UC3844 power supply.
6. After confirming that the voltage at the power supply terminal of UC3844 is normal, an oscilloscope can be used to check if there is a PWM wave output from pin 6 of UC3844 to the trigger terminal of the switch tube (depending on the circuit design, the frequency of the PWM wave is generally between 20KHZ-100KHZ).
7. If there is no PWM wave output, replace timing components C5, R8, C6, or UC3844. After the above steps of elimination, the switch power supply should be able to work normally. In frequency converters, there are many types of switching power supplies, but the basic principles are the same. For example, each PWM management chip has a power supply terminal, a timing element RC network, and ports for outputting PWM waves. As long as we understand their working principles and follow certain methods and steps, we can eliminate faults
