Overcurrent protection circuit for a switching power supply apparatus

Patent metadata

Field	Value
Publication number	US-9385617-B2
Application number	US-201414480998-A
Country	US
Kind code	B2
Filing date	Sep 9, 2014
Priority date	Mar 30, 2012
Publication date	Jul 5, 2016
Grant date	Jul 5, 2016

Abstract

In a switching power supply apparatus, when it is detected at time t1 that a voltage Vis has exceeded a first threshold Vth1, a timer counting a period of time T1 is started, and the number times the input voltage Vis does not exceed Vth1 is started to be counted. When the timer expires before the count reaches a predetermined number, a first overcurrent protection operation is performed. When it is detected at time t2 that Vis has exceeded a second threshold Vth2, a second overcurrent protection operation is immediately performed. As a result, appropriate overcurrent protection is performed in accordance with the operating state of a load.

First claim

What is claimed is:

1. A switching power supply apparatus comprising:
a power conversion circuit configured to convert an input voltage input from an input power supply into an output voltage supplied to a load;
a switch device configured to perform switching for the input voltage;
a switching control circuit configured to control the switch device; and
a current detection circuit configured to detect a current that flows through the switch device in each switching period;
a first overcurrent protection circuit configured to stop a switching operation without outputting an on signal to the switch device in a case where a current detection signal obtained by the current detection circuit has exceeded a first threshold, and thereafter, when it is determined by the switching control circuit that a number of consecutive switching operations, for which the first threshold is not exceeded, has not reached a predetermined number in a predetermined period.

2. The switching power supply apparatus according to claim 1 , wherein the switching power supply apparatus is configured to, after the switching operation has been stopped by the first overcurrent protection circuit, maintain a state in which the switching operation has been stopped.

3. The switching power supply apparatus according to claim 1 , further comprising a recovery circuit configured to start the switching a predetermined period after the switching operation has been stopped by the first overcurrent protection circuit.

4. The switching power supply apparatus according to claim 3 , further comprising a soft-start control unit configured or programmed to gradually increase an on-time width of the switch device at a time of starting the switching operation.

5. The switching power supply apparatus according to claim 1 , further comprising a second overcurrent protection circuit configured to stop the switching operation by making the switch device be in an off state when it has been detected that the current detection signal obtained by the current detection circuit has exceeded a second threshold that is larger than the first threshold.

6. The switching power supply apparatus according to claim 1 , wherein the power conversion circuit includes a current resonant converter.

7. The switching power supply apparatus according to claim 1 , wherein the switching control circuit includes a switching control IC.

8. The switching power supply apparatus according to claim 1 , further comprising a first series circuit including a resonant capacitor, a resonant inductor, a primary winding of a transformer, the switch device, and a current detection resistor.

9. The switching power supply apparatus according to claim 8 , wherein the switch device includes an n-type MOSFET including a drain terminal connected to the primary winding and a source terminal connected to the current detection resistor.

10. The switching power supply apparatus according to claim 1 , further comprising a second switch device defined by an n-type MOSFET connected to the switch device.

11. The switching power supply apparatus according to claim 1 , further comprising a center-tap full-wave rectifying and smoothing circuit including diodes and a capacitor provided at secondary windings of a transformer.

12. The switching power supply apparatus according to claim 1 , further comprising a transformer and a rectifying and smoothing circuit connected to the transformer.

13. The switching power supply apparatus according to claim 1 , further comprising a second switch element and a driving circuit configured to receive a signal from the switching control circuit and drive the switch device and the second switch element in a complementary manner.

14. The switching power supply apparatus according to claim 1 , further comprising a feedback circuit connected to the switching control circuit.

15. The switching power supply apparatus according to claim 1 , further comprising a transformer including a secondary side that is a forward type, and a rectifying and smoothing circuit on the secondary side of the transformer.

16. The switching power supply apparatus according to claim 15 , wherein the rectifying and smoothing circuit includes diodes, an inductor and a capacitor.

17. The switching power supply apparatus according to claim 15 , further comprising a capacitor provided on a primary side of the transformer.

18. The switching power supply apparatus according to claim 1 , further comprising a flyback transformer including a secondary side, and a rectifying and smoothing circuit on the secondary side of the flyback transformer.

19. The switching power supply apparatus according to claim 18 , wherein the rectifying and smoothing circuit includes a diode and a capacitor.

20. The switching power supply apparatus according to claim 18 , further comprising a capacitor provided on a primary side of the flyback transformer.

Assignees

• Murata Manufacturing Co

Inventors

• Hosotani Tatsuya
• Yamaguchi Naoki

Classifications

• H02H3/093 Primary

  with timing means {(in general H02H3/027; thermal delay H02H3/085; timing means for undervoltage protection H02H3/247)} · CPC title

• Y02B70/1491

  Cross-Sectional Technologies · mapped topic

• H02M3/33507

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M3/33546 Primary

  with automatic control of the output voltage or current (H02M3/33561 takes precedence) · CPC title

• H02M1/36

  Means for starting or stopping converters · CPC title