# US 2014/0157015 A1 · Clamp circuits for power converters

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- Number: US 2014/0157015 A1
- Document ID: US20140157015A1
- Status: Published application
- Kind: A1
- Application number: 13/389,198
- Filed: 2011-08-12
- Published: 2014-06-05
- Earliest claimed: 2011-08-12
- Assignees: Intersil Americas Inc.
- Inventors: Xiaodong (David) Zhan; Long (Robin) Yu; Shijia (Billy) Yang
- Web page: https://patentgrep.com/patent/US20140157015A1

## CPC

- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- G06F 1/32: Means for saving power
- H02M 1/34: Snubber circuits
- H02M 3/33576: {having at least one active switching element at the secondary side of an isolation transformer}
- H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer}
- H02M 1/346: {Passive non-dissipative snubbers}
- Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
- 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)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A power converter comprises an input port configured to receive a source of power, an output port configured to provide output power, and a bridge circuit coupled to the input port. The bridge circuit comprises a first switch coupled in series with a second switch, and a third switch coupled in series with a fourth switch. A first clamp rectifier is coupled in series with a second clamp rectifier, and the first and second clamp rectifiers are coupled in parallel with the first and second switches. A first clamp capacitor is coupled between the first and second clamp rectifiers, with the first clamp capacitor operative to reduce power loss in the first and second clamp rectifiers. A first resonant inductor is coupled between the first and second switches. The power converter also includes a transformer operatively coupled to the bridge circuit, with the transformer comprising a primary winding and at least one secondary winding. A current rectifying circuit is operatively coupled to the secondary winding of the transformer and the output port.

## Claims

### Claim 1

A power converter, comprising:
an input port configured to receive a source of power;
an output port configured to provide output power;
a bridge circuit operatively coupled to the input port, the bridge circuit comprising:
a first switch coupled in series with a second switch;
a third switch coupled in series with a fourth switch;
a first clamp rectifier coupled in series with a second clamp rectifier, wherein the first and second clamp rectifiers are coupled in parallel with the first and second switches;
a first clamp capacitor coupled between the first and second clamp rectifiers, the first clamp capacitor operative to reduce power loss in the first and second clamp rectifiers; and
a first resonant inductor coupled between the first and second switches;
a transformer operatively coupled to the bridge circuit, the transformer comprising a primary winding and at least one secondary winding; and
a current rectifying circuit operatively coupled to the secondary winding of the transformer and the output port.

### Claim 2 (depends on 1)

The power converter of claim 1, wherein the first and second switches are coupled in parallel with the input port, and the third and fourth switches are coupled in parallel with the input port.

### Claim 3 (depends on 1)

The power converter of claim 1, wherein the switches each comprise a semiconductor switching device.

### Claim 4 (depends on 3)

The power converter of claim 3, wherein the semiconductor switching device comprises a transistor.

### Claim 5 (depends on 1)

The power converter of claim 1, wherein the first and second clamp rectifiers are coupled in parallel with the input port.

### Claim 6 (depends on 1)

The power converter of claim 1, further comprising an output inductor coupled between the secondary winding of the transformer and the output port.

### Claim 7 (depends on 1)

The power converter of claim 1, further comprising an output capacitor coupled in parallel with the output port, and a first resistor coupled in parallel with the output port.

### Claim 8 (depends on 1)

The power converter of claim 1, wherein the rectifying circuit comprises a first diode coupled between the secondary winding and the output port, and a second diode coupled between the secondary winding and the output port.

### Claim 9 (depends on 8)

The power converter of claim 8, wherein the rectifying circuit further comprises a fifth switch coupled between the secondary winding and the output port, and a sixth switch coupled between the secondary winding and the output port.

### Claim 10 (depends on 9)

The power converter of claim 9, wherein the rectifying circuit further comprises a first capacitor coupled between the first diode and the output port, and a second capacitor coupled between the second diode and the output port.

### Claim 11 (depends on 8)

The power converter of claim 8, further comprising a second resistor coupled between the first diode and the output port.

### Claim 12 (depends on 1)

The power converter of claim 1, further comprising a transformer leakage inductor coupled between the first resonant inductor and the primary winding of the transformer.

### Claim 13 (depends on 1)

The power converter of claim 1, wherein the transformer comprises a top secondary winding coupled to the current rectifying circuit, and a bottom secondary winding coupled to the current rectifying circuit.

### Claim 14 (depends on 1)

The power converter of claim 1, wherein the power converter is a zero voltage switching asymmetric full-bridge DC-output converter.

### Claim 15 (depends on 1)

The power converter of claim 1, wherein the bridge circuit further comprises
a third clamp rectifier coupled in series with a fourth clamp rectifier, wherein the third and fourth clamp rectifiers are coupled in parallel with the third and fourth switches;
a second clamp capacitor coupled between the third and fourth clamp rectifiers, the second clamp capacitor operative to reduce power loss in the third and fourth clamp rectifiers; and
a second resonant inductor coupled between the third and fourth switches.

### Claim 16 (depends on 1)

The power converter of claim 1, wherein the first and second clamp rectifiers comprise a clamp diode or a synchronous rectifier.

### Claim 17 (depends on 15)

The power converter of claim 15, wherein the first and second resonant inductors are configured to produce the same inductance values.

### Claim 18 (depends on 15)

The power converter of claim 15, wherein the power converter is a zero voltage switching symmetric full-bridge DC-output converter.

### Claim 19

A power converter, comprising:
an input port configured to receive a source of power;
an output port configured to provide output power;
a bridge circuit operatively coupled to the input port, the bridge circuit comprising:
a first transistor coupled in series with a second transistor;
a third transistor coupled in series with a fourth transistor;
a first clamp diode coupled in series with a second clamp diode, wherein the first and second clamp diodes are coupled in parallel with the first and second transistors;
a first clamp capacitor coupled between the first and second clamp diodes;
a third clamp diode coupled in series with a fourth clamp diode, wherein the third and fourth clamp diodes are coupled in parallel with the third and fourth transistors;
a second clamp capacitor coupled between the third and fourth clamp diodes; and
a first resonant inductor coupled between the first and second a first resonant inductor coupled between the first and second transistors; and
a second resonant inductor coupled between the third and fourth transistors;
a transformer operatively coupled to the bridge circuit;
a current rectifying circuit operatively coupled to the transformer and the output port;
an output inductor coupled between the transformer and the output port; and
a transformer leakage inductor coupled between the first resonant inductor and the transformer;
wherein the first and second resonant inductors are configured to produce the same inductance values.

### Claim 20 (depends on 19)

The power converter of claim 19, wherein the power converter is a zero voltage switching symmetric full-bridge DC-output converter.

### Claim 21

An electronic system comprising:
at least one processor;
at least on memory device operatively coupled to the processor; and
at least one power converter electrically coupled to the processor and the memory unit, the power converter comprising:
a bridge circuit comprising:
a first transistor coupled in series with a second transistor;
a third transistor coupled in series with a fourth transistor;
a first clamp rectifier coupled in series with a second clamp rectifier, wherein the first and second clamp rectifiers are coupled in parallel with the first and second transistors;
a first clamp capacitor coupled between the first and second clamp rectifiers, the first clamp capacitor operative to reduce power loss in the first and second clamp rectifiers; and
a first resonant inductor coupled between the first and second transistors;
a transformer operatively coupled to the bridge circuit; and
a current rectifying circuit operatively coupled to the transformer.

### Claim 22 (depends on 21)

The electronic system of claim 21, wherein the power converter is a zero voltage switching full-bridge DC-output converter.

### Claim 23 (depends on 21)

The electronic system of claim 21, wherein the bridge circuit further comprises:
a third clamp rectifier coupled in series with a fourth clamp rectifier, wherein the third and fourth clamp rectifiers are coupled in parallel with the third and fourth transistors;
a second clamp capacitor coupled between the third and fourth clamp rectifiers, the second clamp capacitor operative to reduce power loss in the third and fourth clamp rectifiers; and
a second resonant inductor coupled between the third and fourth transistors.

### Claim 24 (depends on 23)

The electronic system of claim 23, wherein the power converter is a zero voltage switching full-bridge DC-output converter.

### Claim 25

A method comprising:
receiving an input DC voltage at a resonant inductor, the resonant inductor coupled to a transformer and a clamp capacitor;
generating control signals for a first switch and a second switch coupled to the transformer;
storing energy in the resonant inductor from the input DC voltage when the control signals turn on both of the first and second switches; and
releasing energy from the resonant inductor through the transformer when the control signals turn on only one of the first and second switches;
wherein the clamp capacitor allows part of a current to flow to a third switch or a fourth switch to reduce power loss in one or more clamp rectifiers.