# US 7,609,038 B2 · Switching power supply with protection function

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- Number: US 7,609,038 B2
- Document ID: US7609038B2
- Status: Granted
- Kind: B2
- Application number: 11/831,971
- Filed: 2007-08-01
- Published: 2008-12-11
- Granted: 2009-10-27
- Earliest claimed: 2007-06-07
- Assignees: Hon Hai Precision Industry Co., Ltd.
- Inventors: Ming-Chih Hsieh
- Web page: https://patentgrep.com/patent/US7609038B2

## CPC

- H02M 1/36: Means for starting or stopping converters
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)

## Abstract

A switching power supply with protection function includes a transistor controlled to be on or off by a PWM signal from a PWM controller to convert a DC voltage into a square wave signal, a filter filtering the square wave signal into an output voltage signal, the output voltage signal being fed back to the PWM controller to be compared with a predetermined voltage, and a switch device having an input terminal for receiving the output voltage signal from the filter, an output terminal for connecting to a load, and a control terminal. If the voltage of the output voltage signal from the filter is not equal to the predetermined output voltage, the PWM controller will not output a signal to the control terminal of the switch device and the switch device will be in an off state. The PWM controller adjusts the duty ratio of the PWM signal until the voltage of the output voltage signal from the filter is equal to the predetermined output voltage such that the PWM controller outputs a control signal to turn on the switch device to allow the load receiving the output voltage signal via the switch device.

## Claims

### Claim 1

A switching power supply with protection function, comprising:
a transistor having an input terminal for receiving a direct current voltage, an output terminal, and a control terminal;
a switch device having an input terminal, an output terminal for connecting to a load, and a control terminal;
a pulse width modulation (PWM) controller having a PWM signal output terminal for outputting a PWM signal to the control terminal of the transistor to turn on or off the transistor so that a square wave signal is produced at the output terminal of the transistor, a feedback signal input terminal connected to the input terminal of the switch device, and a control signal output terminal connected to the control terminal of the switch device; and
a filter connected between the output terminal of the transistor and the input terminal of the switch device for filtering the square wave signal from the transistor and outputting an output voltage signal to the input terminal of the switch device, the output voltage signal being fed back to the PWM controller to be compared with a predetermined output voltage;
when the voltage of the output voltage signal from the filter is not equal to the predetermined output voltage, the PWM controller does not output a signal at the control signal output terminal thereof and the switch device is in an off state, the PWM controller adjusts the duty ratio of the PWM signal until the voltage of the output voltage signal from the filter is equal to the predetermined output voltage such that the PWM controller outputs a control signal to turn on the switch device.

### Claim 2 (depends on 1)

The switching power supply with protection function as described in claim 1, wherein the transistor is a MOS transistor.

### Claim 3 (depends on 1)

The switching power supply with protection function as described in claim 1, wherein the switch device is a MOS transistor.

### Claim 4 (depends on 1)

The switching power supply with protection function as described in claim 1, wherein the filter is an LC filter.

### Claim 5

A switching power supply with protection function, comprising:
a transistor being controlled on or off by a pulse width modulation (PWM) signal from a PWM controller to convert a direct current voltage into a square wave signal;
a filter filtering the square wave signal into an output voltage signal, the output voltage signal being fed back to the PWM controller to be compared with a predetermined voltage; and
a switch device having an input terminal for receiving the output voltage signal from the filter, an output terminal for connecting to a load, and a control terminal connected to the PWM controller;
when the output voltage signal from the filter is not equal to the predetermined output voltage, the PWM controller does not output a signal to the control terminal of the switch device and the switch device is in an off state, the PWM controller adjusts the duty ratio of the PWM signal until the voltage of the output voltage signal from the filter is equal to the predetermined output voltage such that the PWM controller outputs a control signal to turn on the switch device.

### Claim 6 (depends on 5)

The switching power supply with protection function as described in claim 5, wherein the transistor is a MOS transistor.

### Claim 7 (depends on 5)

The switching power supply with protection function as described in claim 5, wherein the switch device is a MOS transistor.

### Claim 8 (depends on 5)

The switching power supply with protection function as described in claim 5, wherein the filter is an LC filter.