| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching DC power supply comprising a power supply voltage detection circuit having hysteresis in which power consumption through a starting resistor for detecting DC voltage is minimized. SOLUTION: The switching DC power supply comprises a starting resistor R1 being connected to the DC positive electrode side of a bridge diode D1 for rectifying AC voltage, a capacitor C1 being connected to the other end of the starting resistor R1 through a start control transistor Q1, a starting voltage detection circuit for detecting the starting voltage and the stopping voltage from the voltage value for charging the capacitor C1, and a PWM control circuit IC1 starting operation when the starting voltage detection circuit detects the starting voltage and performing PWM control of a switching transistor Q5 to supply a load with a DC voltage. When the starting voltage detection circuit detects the starting voltage, charging of the capacitor C1 is stopped by interrupting current flow to the starting resistor R1 and when the starting voltage detection circuit detects the stopping voltage, the capacitor C1 is charged by supplying a current to the starting resistor R1 through the transistor Q1. COPYRIGHT: (C)2006,JPO&NCIPI
|
