⑴ The input circuit for 220V AC voltage and the rectification and filtering circuit fail to provide sufficient working voltage to the switching tube, exceeding the control range of the pulse width modulation circuit. ⑵ The load circuit experiences overcurrent, causing the load on the switching power supply to increase, leading to a drop in output voltage. ⑶ The on/off interface circuit is in a standby state, causing the switching power supply to operate in a low-frequency oscillation state with an output voltage equivalent to the standby state. Such a fault should only occur in models that lack a backup power supply, where the working voltage for the CPU in standby mode is provided by the switching power supply. Aircraft ground power, 36V aircraft power supply, 400HZ variable frequency power supply, 115/200V power supply, 27V DC power supply, 400HZ power supply, aircraft power supply
④ The interface circuit at the end of the on/off switch operates between the on and standby states due to a fault, causing the switching power supply to work at a frequency between standby and on states, resulting in the output voltage of the switching power supply being higher than the standby value and lower than the on value. ⑸ The protection circuit operates in a conductive state due to a fault, leading to weak oscillation and narrow pulse power supply, which causes the output voltage of the switching power supply to drop. ⑹ The diodes and filter capacitors in the rectifier output circuit, as well as the damaged current-limiting resistors, lead to a decrease in output voltage. ⑺ The pulse width modulation circuit has an issue, failing to respond tangentially to changes in the output voltage of the switching power supply. The adjustment of the base voltage of the power switch is incorrect in direction and magnitude, thereby causing the output voltage of the switching power supply to be low.
