US 5,087,871 A · Power supply with inrush current limiter

Abstract

A power supply circuit which includes a current limit circuit for limiting the inrush current when the power supply is switched on. The current limit circuit is coupled between a supply voltage at the input end of the power supply and a storage capacitor at the output end of the power supply. The current limit circuit includes a first semiconductor switch having a resistor in parallel with its switching path. In parallel with the control path of the first semiconductor switch is a parallel circuit that includes a first capacitor, a first resistor and the switching path of a second semiconductor switch. The control electrode of the second semiconductor switch is connected to a tap on a first voltage divider to which a second capacitor is connected in parallel. The switching path of a third semiconductor switch is connected parallel to the control path of the second semiconductor switch. The third semiconductor switch is cut off in response to a control current supplied by a threshold value circuit when the supply voltage is below a threshold value.

Claims20

Dependent claims

A power supply comprising, between an input terminal for a supply voltage and a storage capacitor at an output terminal, an inrush current limiting circuit including a first semiconductor switch with a switching path and a shunt resistor in parallel to said switching path, a first capacitor coupled to a source of charge current, means connecting a circuit in parallel to a control path of the first semiconductor switch, said parallel circuit comprising the first capacitor, a first resistor and a switching path of a second semiconductor switch, wherein a control electrode of the second semiconductor switch is connected to a tap on a first voltage divider to which a second capacitor is connected in parallel, a switching path of a third semiconductor switch being connected in parallel to a control path of the second semiconductor switch, and a threshold circuit which supplies a control current to cut off the third semiconductor switch below a threshold value of the supply voltage.

A power supply comprising:

a pair of input terminals for connection to a supply voltage,
a pair of output terminals for connection to a load,
a storage capacitor coupled to said output terminals, and
a current limit circuit which comprises;
a first controlled semiconductor switch coupled between a first of said input terminals and a first of said output terminals,
a current limit resistor connected in parallel arrangement with said first semiconductor switch,
means coupling a time delay unit to one of said input terminals and to a control electrode of the first semiconductor switch so as to delay turn-on of the first semiconductor switch when a supply voltage is initially applied to the input terminals,
means coupling a control circuit to said control electrode of the first semiconductor switch for controlling conduction thereof, and
a voltage threshold circuit coupled to said input terminals and with a control output coupled to said control circuit, said voltage threshold circuit being responsive to a supply voltage at the input terminals so as to provide a control signal via said control circuit that is operative to switch off the first semiconductor switch when the supply voltage is below a given voltage threshold value.

6 more elements

Dependencies are inferred from the claim text.

Power supply with inrush current limiter

Life of this patent

Power supply with inrush current limiter

Life of this patent

Abstract

Claims20