Constant inrush current circuit for AC input power supply unit

摘要

A power supply circuit includes a rectifier module configured to rectify an input voltage and a capacitor including a first terminal coupled to the rectifier module. In addition, the power supply circuit includes first and second transistors. The first transistor couples to a second terminal of the capacitor, and the second transistor couples in series to the first transistor. The power supply circuit also includes a resistor, configured to set an inrush current value, in parallel with the second transistor. When coupled to a power supply, the power supply circuit is configured to turn-on the first transistor such that an inrush current flows, at the inrush current value, through the capacitor, first transistor, and resistor. After a delay time, the power supply circuit is configured to turn-on the second transistor such that the inrush current drops to around zero, thus maintaining a low impedance path during steady-state operation.

主权项

1. A power supply circuit, comprising:
a rectifier module including first and second input terminals and first and second output terminals, the rectifier module configured to rectify an input voltage; an output capacitor including a first terminal coupled to the first output terminal of the rectifier module; a first transistor including first and second current electrodes, the first current electrode coupled to a second terminal of the output capacitor; a second transistor including third and fourth current electrodes, the third current electrode coupled to the second current electrode of the first transistor, and the fourth current electrode coupled to the second output terminal of the rectifier module; and a resistor connected in parallel with the second transistor, the resistor configured to set an inrush current value; wherein the power supply circuit is configured, when the first and second input terminals of the rectifier module are coupled to a power supply, to turn-on the first transistor such that an inrush current flows, at the inrush current value, through the output capacitor, the first transistor, and the resistor; and wherein the power supply circuit is configured, after the rectifier module has been coupled to the power supply for a specified delay time, to ensure that the inrush current has dropped to a value of about zero amperes, to turn-on the second transistor.