How are inverter switching power supply problems diagnosed and fixed?
Damage to the switching power supply is the most common failure of many inverters. It is usually due to the occurrence of the switching power supply. When there is no display, no voltage at the control terminals, and DC12V, DC24V fans do not turn, etc., you should first consider whether the switching power supply is damaged. An obvious feature of the damaged switching power supply is that there is no display after the inverter is powered on. For example, the Fuji G5S inverter uses a two-stage switching power supply. The principle is that the DC voltage of the main DC circuit drops from 500V to about 300V, and then outputs 5V and 24V multi-channel power supplies through a first-stage switch step-down. Common damages to switching power supplies include switch tube breakdown, pulse transformer burnout, and secondary output rectifier diode damage. The filter capacitor has been used for too long, resulting in changes in capacitance characteristics (capacity reduction or large leakage current), and voltage stabilization capabilities. , It is also easy to cause damage to the switching power supply. For example, the switching power supply of the MF series inverter adopts the relatively common flyback switching power supply control method. A short circuit in the output stage circuit of the switching power supply will also cause damage to the switching power supply, resulting in no display on the inverter. The reasons for the damage of the switching power supply are as follows:
(1) The environment is polluted, and the insulation is damaged due to dust, water vapor, etc. When the switching power supply has deeply yellowed and carbonized the printed board due to local high temperature or the printed line is damaged, and the insulation, copper clad foil and wire of the printed board can no longer be used, the printed board can only be replaced as a whole. After detecting the damaged components, replace them with new ones. The component model should be consistent with the original model. If it is not consistent, it is necessary to confirm whether the power switching frequency, withstand voltage and size of the component can be installed, and keep an insulating distance from the surrounding components.
(2) The life of the components themselves, especially the switching tube or switching integrated circuit, is more easily damaged due to the large current and voltage burden.
(3) The enameled wire of the switching transformer has been used for a long time at high temperature, and it has yellowing, scorched smell, breakdown between transformer windings, disconnection of transformer windings, especially high-voltage windings, deformation of the skeleton and traces of arc jumping. Transformer wires are broken over time due to oxidation and flux corrosion.
(4) The leakage inductance of the switching power supply transformer itself is large, and the leakage inductance of the primary winding during operation causes a large-energy overvoltage. When the energy is absorbed by the absorbed components (resistance-capacitance components, voltage regulator tubes, and instantaneous voltage suppression diodes), serious Overload, the absorbing element will be damaged over time.
