| 摘要 |
PURPOSE:To improve the conversion efficiency by providing a discharge transistor for conducting both ends of a damper diode, and absorbing a spike pulse. CONSTITUTION:A switching power source circuit has a DC power source E, a transformer T, a switching transistor (Tr) Qs, and a switching pulse generator PG, and outputs a DC voltage from the secondary winding L2 through a rectifying diode D2 and a smoothing capacitor C2. To obtain the prescribe output voltage, it is detected by a detector DT to pulse-width modulate it. In this case, a series circuit of a damper diode Dd and a capacitor Cd is connected with both ends of the first winding L1 of the transistor, TrQd is connected in parallel with the diode Dd, and a pulse generated at the third winding L3 is rectified by a rectifier Dt and differentiated by Ct, Rt and applied to the base. Thus, a spike pulse when the TrQs is OFF is absorbed by the capacitor Cd, discharged by TrQd during the OFF period of the TrQs to completely absorb the pulse. |
