| 摘要 |
<P>PROBLEM TO BE SOLVED: To safely stop rectification-side and commutation-side switching elements driven by transformer winding at the time of stop of a main switching element while achieving high power supply efficiency regardless of the amount of a load. <P>SOLUTION: A switching power supply apparatus with a forward inverter circuit includes a rectification side switching element 32 and a diode 32a in an output rectifier, and a commutation-side switching element 34 and a diode 34a. A gate of the commutation-side switching element 34 has a commutation-side drive condenser 32c and a discharge resistor 54. A main transformer 16 has an auxiliary winding 16c. The switching power supply apparatus also includes a differential circuit 58 that observes a change of voltage of the auxiliary winding 16c at the time of turning off a main switching element 14; a driving transistor 60 that outputs a differential output through a source follower; a hold diode 62 that outputs the differential output to the gate of the commutation-side switching element 34; and a voltage drop circuit 66 that generates a voltage difference between the gate of the commutation-side switching element 34 and the auxiliary winding 16c. <P>COPYRIGHT: (C)2012,JPO&INPIT |
