Abstract: A switching power supply control method includes the following: when a switching time interval of the second switching transistor being less than or equal to a first preset value after the high-voltage startup of the switching power supply, the secondary control module acquires a voltage waveform at a second connection point between the secondary winding and the second switching transistor; when the voltage waveform at the second connection point has not achieved zero voltage switching, the secondary control module adjusts the cut-off current of the second switching transistor until a voltage waveform at a first connection point between the primary winding and the first switching transistor just reaches zero; and when the voltage waveform at the first connection point just reaches zero, the primary control module controls the first switching transistor to be turned on.

Abstract: A switching power supply control method includes the following: after the high-voltage startup of the switching power supply, the secondary control module adjusts the cut-off current of the second switching transistor according to a voltage waveform at a second connection point until a voltage waveform at a first connection point just reaches zero, the primary control module controls the first switching transistor to be turned on; the primary control module adjusts the peak current of the first switching transistor until the peak current of the first switching transistor reaches a preset value, the primary control module controls the first switching transistor to be turned off; the secondary control module controls the second switching transistor to be turned on; and in case where the switching current of the second switching transistor is at a current zero-crossing point, the secondary control module controls the second switching transistor to be turned off.