| 摘要 |
PURPOSE:To prevent the operation frequency of a series resonance converter from changing greatly while reducing its switching loss even when its output frequency has lowered. CONSTITUTION:A series resonance converter is provided with a current transformer 41 in a resonance current route. The secondary side of the current transformer is connected to input terminals 3, 5 through a rectifier circuit 43, auxiliary switching element FET 45, and diode 47. When the output voltage is normal, the auxiliary switching element FET 45 is turned on to perform ordinary operation. When the output voltage lowers and the resonance current I has a longer trailing, the auxiliary switching element FET 45 is turned off to feed back part of the energy of the resonance current I to an input DC power supply 1, to reduce the current to zero quickly, thereby softly turning off the main switching elements IGBT 17 and 19. |
