1results about How to "Improve EMI characteristics" patented technology

The embodiment of the application discloses a control method and a switching power supply. The control method comprises the following steps: after the high-voltage starting of the switching power supply, and when the switching time interval of the second switch tube is equal to or smaller than the first preset value, the secondary side control module acquires the voltage waveform of the second connection point between the secondary side winding and the second switch tube; when the voltage waveform of the second connection point does not realize zero voltage switching, the secondary side control module adjusts the off current of the second switch tube until the voltage waveform of the first connection point between the primary side winding and the first switch tube is just zero; when the voltage waveform of the first connection point is just zero, the primary side control module controls the first switch tube to be turned on, so as to realize the zero voltage opening of the primary side. The embodiment reduces the switching loss of the switching power supply, and improves the EMI characteristics of the switching power supply.