| 摘要 |
PROBLEM TO BE SOLVED: To reduce power consumption by the drive resistor of a switching power supply. SOLUTION: This switching power supply comprises a converter transformer having a pair of primary winding and a pair of secondary winding and a feedback winding, and a first and a second driving resistors for driving each of a first and a second NPN transistors which are connected to each primary winding in series and of which bases are connected to a corresponding feedback winding end. In the power supply, an auxiliary winding is provided on the primary side of the converter transformer, and an auxiliary power supply which consists of a first diode and a smoothing capacitor is connected. A cathode side of the first diode and the base of the first NPN transistor are connected to each other through a third driving resistor and a second diode, the cathode side of the first diode and the base of the second NPN transistor are connected to each other through a fourth driving resistor and a third diode. The auxiliary power supply set to the voltage lower than an input voltage to the first and the second driving resistors is connected to the third and the fourth driving resistors. COPYRIGHT: (C)2004,JPO
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