Patent ID: 7242596
Filing Date: 2007-07-10
Classification: H02M,Y02B

Abstract:
1. A control method for controlling a switching power supply circuit comprising a transformer with a primary winding and a secondary winding, and a switching device connected in series to the primary winding of the transformer, a series circuit of the primary winding and the switching device being connected in parallel to a DC power supply so that when the switching device is switched on and off, a voltage across the secondary winding of the transformer is rectified and smoothened to obtain a stable DC output voltage, said control method comprising: amplifying a difference between the DC output voltage and a reference voltage to obtain a feedback signal; adjusting an ON-period of the switching device using the feedback signal to control the output voltage; continuously switching on and off the switching device in a state of normal load to conduct a normal mode of operation; intermittently switching on and off the switching device in a state of light load to conduct a waiting mode of operation comprising a switching period and a switching pause period; and setting a first setting value for limiting a peak exciting current of the transformer, wherein at a beginning of the switching period in the waiting mode of operation, when the first setting value is smaller than the feedback signal, the first setting value is used for a reference value for the peak exciting current of the transformer, and the first setting value is gradually raised.