Patent ID: 9742293
Date: 2017-08-22
CPC Classifications: H02M

Claim:
1. A power supply for converting an external alternating power into an output power, comprising: an input charging unit comprising a fuse, a first charging resistor, a second charging resistor and a charging capacitor, the first and second charging resistors connected in series and configured to receive the external alternating power, a connection point of the first and second charging resistors connected to one end of the charging capacitor, the other end of the charging capacitor grounded, the charging capacitor charged by a charging capacitor voltage through the connection point from the external alternating power at initially powering on; an input filtering unit connected to the first and second charging resistors for receiving and converting the external alternating power into an input power through a filtering process; a regulating unit connected to the input filtering unit and comprising a regulating capacitor and a regulator connected in series, one end of the regulator connected to the input filtering unit being grounded; a transformer comprising a primary coil, an auxiliary coil and a secondary coil, one end of the primary coil connected to the input filtering unit for receiving the input power, the auxiliary coil generating an auxiliary induced voltage through induction with a current flowing through the primary or secondary coil; a switching unit implemented by a transistor and having a drain, a gate and a source, the drain connected to the primary coil, the source connected to one end of a first sensing resistor and one end of a second sensing resistor, the other end of the first sensing resistor grounded, the other end of the second sensing resistor connected to one end of a sensing capacitor, the other end of the sensing capacitor being grounded; a controller having a controller power input port, a feedback signal port, a regulating control port, a driving port and a current sensing port, the controller power input port connected to the connection point of the first and second charging resistors, the auxiliary induced voltage of the auxiliary coil connected to the controller power input port through a rectifying resistor and a rectifying diode connected in series, the regulating control port connected to the regulator for controlling the regulator to perform one of working modes of initial open circuit, power on conduction, short circuit normal operation or over-voltage open circuit protection, the driving port directly connected to the gate of the switching unit or indirectly connected to the gate of the switching unit through a current limiting/rectifying element, the current sensing port connected to the other end of the second sensing resistor and the one end of the sensing capacitor; an output unit connected to the secondary coil for receiving and filtering a current flowing through the secondary coil to generate the output power; an output capacitor connected to the output unit for stabilizing the output power; and a feedback unit connected to the output unit for receiving the output power to generate and transmit a feedback signal to the feedback signal port of the controller so as to form a feedback loop for the controller to detect and control the output power.