Switching power inverter supply has DC voltage output, but the output DC voltage is too low

For this kind of fault phenomenon, according to the maintenance experience, in addition to the voltage regulator control circuit will cause the output voltage to be too low, there are some reasons that will cause the output voltage to be too low, mainly the following:

1. The switching power inverter supply load has a short circuit fault. At this time, all the loads of the switching power supply circuit should be disconnected to distinguish whether the switching power supply circuit or the load circuit is faulty. If the voltage output of the load circuit is disconnected, it means that the load is too heavy; if it is still not normal, the switching power supply circuit is faulty.
2. The output voltage terminal rectifier diode, filter capacitor failure, etc., can be judged by the substitution method.
3. The performance of the switching power tube is degraded, which will inevitably lead to the switch tube not being able to conduct normally, which will increase the internal resistance of the power supply and reduce the load capacity.
4. The source (S pole) of the switching power tube is usually connected to a resistor with a small resistance but a large power. As an overcurrent protection detection resistor, the resistance of this resistor is generally between 0.2 and 0.8. If the resistor is changed or soldered, poor contact may cause the output voltage to be too low.
5. The high-frequency transformer is not good, which not only causes the output voltage to drop, but also causes the switching power tube to be insufficiently excited to damage the switch tube.
6. The high-voltage DC filter capacitor is poor, resulting in poor power supply load capacity, and the output voltage of the load will drop.
7. The power supply output line has poor contact and has a certain contact resistance, which causes the output voltage to be too low.
8. Is the grid voltage too low? Although the switching power supply can still output the rated voltage value under low voltage, when the grid voltage is lower than the minimum voltage limit of the switching power supply, the output voltage will be too low.
   Maintenance method: For this kind of failure, we can check one by one according to the above reasons. However, in actual maintenance, it can be checked according to the actual situation, and it is not necessary to check one by one. First, use a multimeter to check whether the high-voltage DC filter capacitor is degraded, whether the capacity is reduced, and whether it can be charged and discharged normally. If there is no such phenomenon, measure the current limiting resistance of the gate (G pole) of the switching power tube and the overcurrent protection detection resistance of the source (S pole) for deterioration, power inverter deterioration or open soldering, and poor contact. After the discrimination, if there is no problem, we will check whether the core of the high-frequency transformer is intact. Due to the inevitable heavy fall or heavy building in daily life, the core of the high-frequency transformer is damaged. The magnetic flux, magnetic induction, and magnetic circuit of the high-frequency transformer are greatly affected, resulting in transmission efficiency and greatly reduced energy. In order to reduce the eddy current and increase the transmission efficiency of high-frequency alternating current, the high-frequency transformer is made of soft ferrite. This magnetic material has high magnetic permeability but is brittle and brittle. Therefore, its damage rate is also very high. Therefore, don’t forget to check here during maintenance to avoid detours. In addition to this, there may be a decrease in the output filter capacitor capacity, or even loss of capacity or open soldering, virtual connection; power supply output current limiting resistor variable value or virtual connection, power supply output line virtual connection. In the actual maintenance, these factors should not be let go, should be checked to ensure that nothing is lost.