| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-cost life detecting circuit for detecting the life of a smoothing capacitor. SOLUTION: According to the life detecting circuit 11 of a switching power supply device, an inter-terminal voltage VDC of a smoothing capacitor 10 is divided to create a monitor voltage VM. When an instantaneous value of the monitor voltage VM drops below a threshold voltage VTH of a transistor 25, the transistor 25 is turn off and a voltage VO is set at "H"-level. When the output voltage VO becomes the "H"-level voltage, a report part 28 reports that the smoothing capacitor 10 has come to the end of life. Hence the circuit configuration is simplified to reduce costs, as compared with a conventional case where a life detecting capacitor is separately provided. COPYRIGHT: (C)2011,JPO&INPIT |
