| 摘要 |
PURPOSE:To make it possible to perform zero-crossing turn-ON in the entire operating region and to reduce the deterioration of efficiency in the light-load state. CONSTITUTION:A first control circuit 9 turns ON a first switching means 2 after a second switching means 4 is turned OFF, receives the information from a voltage detecting means and determines the ON period of the first switching means 2 so as to stabilize the output DC voltage. The second switching means 4 is turned ON after the first switching means is turned OFF. A second control circuit 10, which receives the information from a current detecting means 8 and has the function for turning OFF the second switching means 4 when the current value reaches the specified value, is provided. Thus, the reverse exciting energy of a transformer 3 can be adjusted to the required amount for achieving zero-cross turn-ON in the entire operating conditions. Therefore, the changing width of the operating current becomes small under the light-load conditions, and the deterioration of efficiency can be prevented. |
