Patent ID: 7880440
Filing Date: 2011-02-01
Classification: H02J,H02M

Abstract:
1. The switching power supply comprising: a high frequency transformer having a primary winding, a secondary winding, and an auxiliary winding; a primary side switching circuit connected to the primary winding of the high frequency transformer, and adapted to switch a current flowing through the primary winding to thereby generate predetermined voltages based on an input voltage, in the secondary winding and the auxiliary winding of the high frequency transformer; a secondary side rectifier connected to the secondary winding of the high frequency transformer, and adapted to rectify the voltage generated in the secondary winding to supply the rectified voltage to a load; a charging circuit connected to the auxiliary winding of the high frequency transformer, and adapted to rectify a current flowing through the auxiliary winding and to switch the rectified current to thereby charge the secondary battery at a constant current; a switch provided between the secondary battery and the load; and a control circuit adapted, when the voltage supplied to the load is interrupted, to supply the voltage of the secondary battery to the load by turning on the switch, wherein the secondary side rectifier, the charging circuit, the secondary battery, and the control circuit have a same reference potential, further comprising: a power factor improving circuit adapted to remove a high frequency component of an input current by switching the input current and by controlling the switching interval, and adapted to supply the input current to the primary side switching circuit, wherein the power factor improving circuit, the primary side switching circuit, and the charging circuit, each performs a switching operation on the basis of a PWM signal input as a control signal, and wherein the control circuit generates the PWM signal supplied to each of the power factor improving circuit, the primary side switching circuit, and the charging circuit, and supplies the generated PWM signal to each of the power factor improving circuit and the primary side switching circuit via an isolated circuit.