# US 2008/0186743 A1 · DC transformer with an output inductance integrated on a magnetic core thereof and a DC/DC converter employing the same

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- Number: US 2008/0186743 A1
- Document ID: US20080186743A1
- Status: Published application
- Kind: A1
- Application number: 12/080,672
- Filed: 2008-04-02
- Published: 2008-08-07
- Earliest claimed: 2004-09-30
- Assignees: Hon Hai Precision Industry Co., Ltd.
- Inventors: Chi-Hsiung Lee; Chau-Tung Fan-Chiang
- Web page: https://patentgrep.com/patent/US20080186743A1

## CPC

- H02M 3/28: using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
- H01F 30/04: having two or more secondary windings, each supplying a separate load, e.g. for radio set power supplies
- H01F 3/14: Constrictions; Gaps, e.g. air-gaps (in magnetic shunt paths H01F3/12)
- 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)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES

## Abstract

A DC/DC converter includes an input filter, a half-bridge converter without PWM (Pulse Width Modulation) control function, a synchronous rectifier, an output capacitor, and a DC transformer. The DC transformer includes a magnetic core, a primary winding, a first secondary winding, and a second secondary winding. The magnetic core of the DC transformer includes a first leg, a second leg having a first air gap, and a third leg having a second air gap. The first secondary winding is wound on the first leg and the second leg, and induces a first inductance by the first air gap. The second secondary winding is wound on the first leg and the third leg, and induces a second inductance by the second air gap.

## Claims

### Claim 1

A DC/DC converter comprising:
an input filter;
a half-bridge converter without PWM (Pulse Width Modulation) control function;
a DC transformer with an integrated output inductor, comprising:
a magnetic core having air gaps and comprising a first leg, a second leg having a first air gap, and a third leg having a second air gap;
a primary winding wound around the first leg;
a first secondary winding wound around the first leg and the second leg for generating a first inductance by the first air gap; and
a second secondary winding wound around the first leg and the third leg for generating a second inductance by the second air gap;
a synchronous rectifier; and
an output capacitor connected to the first secondary winding, a center tap of the second secondary winding, and the synchronous rectifier;
wherein the number of windings of the first secondary winding wound around the first leg is more than the number of winding of the first secondary winding wound around the second leg, and the number of windings of the second secondary winding wound around the first leg is more than the number of winding of the second secondary winding wound around the third leg.

### Claim 2 (depends on 1)

The DC/DC converter of claim 1, wherein the dimension of each air gap of the magnetic core is between 0.02 and 0.07 mm.

### Claim 3 (depends on 1)

The DC/DC converter of claim 1, wherein the magnetic core is of an EE, EI, EQ or RM type.

### Claim 4 (depends on 1)

The DC/DC converter of claim 1, wherein the first leg comprises a third gap.

### Claim 5 (depends on 1)

The DC/DC converter of claim 1, wherein the first leg has no air gap.

### Claim 6 (depends on 1)

The DC/DC converter of claim 1, wherein the first leg is located between the second leg and the third leg.

### Claim 7 (depends on 1)

The DC/DC converter of claim 1, further comprising two outputs from the first secondary winding and the second secondary winding.

### Claim 8 (depends on 1)

The DC/DC converter of claim 1, wherein the first secondary winding is wound half turn on the second leg, and the second secondary winding is wound half turn on the third leg.