INRUSH CURRENT LIMITING CIRCUIT AND POWER SUPPLY DEVICE USING THE SAME

• US 20070252565A1
• Filed: 11/03/2006
• Published: 11/01/2007
• Est. Priority Date: 04/28/2006
• Status: Abandoned Application

• Current Assignee: Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hon Hai Precision Industry Co., Ltd.
• Inventors: Yang, Shun-Chen, Wang, Sin-Shong, Chiang, Kuo-Wei
• Application Number:
  US11/556,191
• Publication Number:
  US 20070252565A1
• Time in Patent Office: Days
• US Class Current: 323/277
• CPC Class Codes: G05F 1/573 with overcurrent detector

Abstract

An inrush current limiting circuit (12) includes a transistor (Q), a switch element (M), and a short-circuit protection circuit (121). An emitter of the transistor is as an input of the inrush current limiting circuit. An input of the switch element is connected to a collector of the transistor. A second output of the switch element is as an output of the inrush current limiting circuit. A first terminal of the short-circuit protection circuit is connected to a first output of the switch element. A second terminal of the short-circuit protection circuit is connected to a base of the transistor. A third terminal of the short-circuit protection circuit is connected to the second output of the switch element.

Claims

1. An inrush current limiting circuit, comprising:

a transistor, having an emitter as an input of the inrush current limiting circuit;

a switch element having an input, a first output, and a second output, wherein the input of the switch element is connected to a collector of the transistor, the second output of the switch element is as an output of the inrush current limiting circuit; and

a short-circuit protection circuit, having a first terminal, a second terminal, and a third terminal, wherein the first terminal of the short-circuit protection circuit is connected to the first output of the switch element, the second terminal of the short-circuit protection circuit is connected to a base of the transistor, and the third terminal of the short-circuit protection circuit is connected to the second output of the switch element.

2. The inrush current limiting circuit as claimed in claim 1, wherein the short-circuit protection circuit comprises:

a first resistor, connected between the first terminal and the second terminal of the short-circuit protection circuit; and

a second resistor, connected between the second terminal and the third terminal of the short-circuit protection circuit, wherein the first resistor and the second resistor form a dividing circuit, for accelerating turn-on time of the transistor.

3. The inrush current limiting circuit as claimed in claim 2, wherein the short-circuit protection circuit further comprises a capacitor, connected to the first resistor in parallel, and the capacitor and the second resistor form a delay circuit.

4. The inrush current limiting circuit as claimed in claim 1, further comprising a variable resistor, connected between the emitter of the transistor and the first output of the switch element, for providing a bias voltage between the base and the emitter of the transistor.

5. The inrush current limiting circuit as claimed in claim 1, further comprising a bias resistor, connected between the input of the switch element and ground, for providing another bias voltage to the switch element.

6. A power supply device, for converting received power signals to direct current signals to ensure a load to work normally, comprising:

a transformer circuit, for stepping down the received power signals;

a rectifier and filter circuit, connected to the transformer circuit, for converting the stepped down signals output from the transformer circuit to the direct current signals; and

an inrush current limiting circuit, connected to the rectifier and filter circuit, for limiting inrush current from the power supply device and providing short-circuit protection function to the load, comprising;

a transistor, having an emitter as an input of the inrush current limiting circuit;

a switch element having an input, a first output, and a second output, wherein the input of the switch element is connected to a collector of the transistor, the second output of the switch element is as an output of the inrush current limiting circuit; and

a short-circuit protection circuit, having a first terminal, a second terminal, and a third terminal, wherein the first terminal of the short-circuit protection circuit is connected to the first output of the switch element, the second terminal of the short-circuit protection circuit is connected to a base of the transistor, and the third terminal of the short-circuit protection circuit is connected to the second output of the switch element.

7. The power supply device as claimed in claim 6, wherein the transformer comprises a transformer comprising a primary winding and a secondary winding.

8. The power supply device as claimed in claim 7, wherein the rectifier and filter circuit comprises:

a first diode;

a second diode, wherein an anode of the second diode and a cathode of the first diode are jointly connected to a high voltage terminal of the secondary winding of the transformer;

a third diode, wherein a cathode of the third diode is connected to a cathode of the second diode; and

a fourth diode, wherein a cathode of the fourth diode and an anode of the third diode are jointly connected to a low voltage terminal of the secondary winding of the transformer, and an anode of the fourth diode is connected to an anode of the first diode.

9. The power supply device as claimed in claim 8, further comprising a filter capacitor connected between the anode of the first diode and the cathode of the second diode.

10. The power supply device as claimed in claim 6, wherein the short-circuit protection circuit comprises:

a first resistor, connected between the first terminal and the second terminal of the short-circuit protection circuit; and

a second resistor, connected between the second terminal and the third terminal of the short-circuit protection circuit, wherein the first resistor and the second resistor form a dividing circuit, for accelerating turn-on time of the transistor.

11. The power supply device as claimed in claim 10, wherein the short-circuit protection circuit further comprises a capacitor, connected to the first resistor in parallel, and the capacitor and the second resistor form a delay circuit.

12. The power supply device as claimed in claim 6, further comprising a variable resistor, connected between the emitter of the transistor and the first output of the switch element, for providing a bias voltage between the base and the emitter of the transistor.

13. The power supply device as claimed in claim 6, further comprising a bias resistor, connected between the input of the switch element and the ground, for providing another bias voltage to the switch element.

14. An inrush current limiting circuit, comprising:

a transistor, having an emitter as an input of the inrush current limiting circuit;

a switch element having an input, a first output, and a second output, wherein the input of the switch element is connected to a collector of the transistor, the second output of the switch element is as an output of the inrush current limiting circuit; and

a short-circuit protection circuit, having a dividing circuit and a delay circuit;

wherein the dividing circuit is for accelerating turn-on time of the transistor and the delay circuit is for delaying turn-on time of the transistor.

15. The inrush current limiting circuit as claimed in claim 14, wherein dividing circuit comprises:

a first resistor, connected to the first output of the switch element and a base of the transistor; and

a second resistor, connected between the base of the transistor and the second output of the switch element.

16. The inrush current limiting circuit as claimed in claim 15, wherein the delay circuit comprises a capacitor, connected to the first resistor in parallel, the capacitor and the second resistor form the delay circuit.

17. The inrush current limiting circuit as claimed in claim 14, further comprising a variable resistor, connected between the emitter of the transistor and the first output of the switch element, for providing a bias voltage between the base and the emitter of the transistor.

18. The inrush current limiting circuit as claimed in claim 14, further comprising a bias resistor, connected between the input of the switch element and ground, for providing another bias voltage to the switch element.