| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a switching power supply, reduce its weight, and improve power conversion efficiency by varying a switching frequency according to the level of a secondary side DC output voltage and hence compositively controlling the conduction angle between the resonance impedance and the switching element of a primary side parallel resonance circuit, and performing the constant-voltage control of the secondary side output voltage. SOLUTION: When a switching frequency is to be varied, a period when a switching element Q1 is turned off is set to constant and a period when it is turned on is controlled variably in a circuit. More specifically, by performing operation so that the switching frequency is controlled variably as a constant- voltage control operation, it is regarded that resonance impedance control for switching output is made and at the same time the conduction angle control of the switching element at the switching period is made. Then, this complex control operation is achieved by a set of control circuit systems. By forming a switching converter in a voltage resonance system, a power conversion efficiency can be improved and miniaturized and its weight can be reduced. |
