# US 10,483,859 B2 · AC/DC converter including a bidirectional switch

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- Number: US 10,483,859 B2
- Document ID: US10483859B2
- Status: Granted
- Kind: B2
- Application number: 15/345,723
- Filed: 2016-11-08
- Published: 2017-05-18
- Granted: 2019-11-19
- Earliest claimed: 2015-11-12
- Assignees: Rohm Co., Ltd.
- Applicants: Rohm Co., Ltd.
- Inventors: Hiroyuki Hatano
- Web page: https://patentgrep.com/patent/US10483859B2

## CPC

- H02M 3/33546: {with automatic control of the output voltage or current (H02M3/33561 takes precedence)}
- H02M 1/4241: {using a resonant converter}
- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- H02M 3/33538: {of the forward type (H02M3/3353, H02M3/33569 take precedence)}
- H02M 3/33553: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- 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)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

An AC/DC converter includes a transformer including a primary winding connected to an AC power source and a secondary winding electromagnetically coupled to the primary winding, a bidirectional switch connected in series to the primary winding, a resonant capacitor connected in parallel or series to the bidirectional switch, a full-wave rectification circuit arranged to perform full-wave rectification of an induced voltage generated in the secondary winding, a smoothing capacitor arranged to smooth an output of the full-wave rectification circuit, and a control circuit arranged to turn on and off the bidirectional switch. The transformer is a leakage transformer or a resonant transformer having leakage inductance. The AC converter takes out both forward voltage and flyback voltage from the secondary winding, so as to directly convert an AC input voltage supplied from the AC power source into a DC output voltage.

## Claims

### Claim 1

An AC/DC converter comprising:
a transformer including a primary winding connected to an AC power source and a secondary winding electromagnetically coupled to the primary winding;
a bidirectional switch connected in series to the primary winding;
a resonant capacitor connected in parallel or series to the bidirectional switch;
a capacitor voltage divider circuit arranged to divide a voltage across both ends of the bidirectional switch so as to generate a divided voltage; and
a control circuit arranged to turn on the bidirectional switch at a timing when the divided voltage becomes zero.

### Claim 2 (depends on 1)

The AC/DC converter according to claim 1, wherein the capacitor voltage divider circuit includes a first capacitor connected in series to the resonant capacitor, so that the divided voltage is output from a connection node between the resonant capacitor and the first capacitor.

### Claim 3 (depends on 1)

The AC/DC converter according to claim 1, wherein the capacitor voltage divider circuit a first capacitor and a second capacitor connected in series to each other between both ends of the bidirectional switch, so that the divided voltage is output from a connection node between the first capacitor and the second capacitor.

### Claim 4 (depends on 2)

The AC/DC converter according to claim 2, wherein the first capacitor has an end connected to a reference potential terminal of the control circuit.

### Claim 5 (depends on 4)

The AC/DC converter according to claim 4, wherein the capacitor voltage divider circuit further includes a discharge switch connected in parallel to the first capacitor.

### Claim 6 (depends on 5)

The AC/DC converter according to claim 5, wherein the control circuit turns on and off the discharge switch in synchronization with the bidirectional switch.

### Claim 7 (depends on 1)

The AC/DC converter according to claim 1, wherein the transformer is a leakage transformer or a resonant transformer having leakage inductance, and the AC/DC converter takes out both forward voltage and flyback voltage from the secondary winding, so as to directly convert an AC input voltage supplied from the AC power source into a DC output voltage.

### Claim 8 (depends on 1)

The AC/DC converter according to claim 1, further comprising a coil connected to at least one of the primary winding and the secondary winding, wherein the AC/DC converter takes out both forward voltage and flyback voltage from the secondary winding, so as to directly convert an AC input voltage supplied from the AC power source into a DC output voltage.

### Claim 9 (depends on 1)

The AC/DC converter according to claim 1, wherein the control circuit drives the bidirectional switch so that power factor becomes close to one.

### Claim 10 (depends on 1)

The AC/DC converter according to claim 1, wherein the control circuit drives the bidirectional switch via a pulse transformer.