INRUSH CURRENT SUPPRESSING CIRCUIT FOR POWER SUPPLY

摘要

An inrush current suppressing circuit for a power supply is provided to efficiently inhibit a second inrush current as well as an initial inrush current by using a resistor. An inrush current suppressing circuit for a power supply includes a normal power supply(1), a bridge diode rectifier(2), a smoothing capacitor(C0), a switching regulator(3), a resistor(R0), an MOSFET(Metal Oxide Semiconductor Field Effect Transistor)(Q1), and a driving circuit(4). The normal power supply supplies normal AC power. The bridge diode rectifier converts the normal AC power to DC power. The smoothing capacitor outputs smooth voltage. The switching regulator switches the smooth voltage by the smoothing capacitor. The resistor is connected between the bridge diode rectifier and the smoothing capacitor, and suppresses initial inrush current. The MOSFET receives a driving voltage through a gate and is connected to the resistor by a source(6) and a drain(7). The driving circuit outputs the driving voltage to the MOSFET in proportion to the voltage of the smoothing capacitor. Second inrush current is limited if the voltage of the smoothing capacitor is sufficient when the power supply is turned on and is inhibited if the voltage of the smoothing capacitor is not sufficient by flowing current only with the resistor.