# US 11,121,634 B2 · Bidirectional DC-to-DC converter with inrush current suppression

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- Number: US 11,121,634 B2
- Document ID: US11121634B2
- Status: Granted
- Kind: B2
- Application number: 16/700,650
- Filed: 2019-12-02
- Published: 2020-06-11
- Granted: 2021-09-14
- Earliest claimed: 2018-12-07
- Assignees: Sharp Kabushiki Kaisha
- Applicants: Sharp Kabushiki Kaisha
- Inventors: Hiroki Tanaka
- Web page: https://patentgrep.com/patent/US11121634B2

## CPC

- H02M 3/33584: {Bidirectional converters}
- H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M 1/32: Means for protecting converters other than automatic disconnection
- H02M 1/36: Means for starting or stopping converters
- H02M 3/3353: {having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter}
- H02M 3/3376: {with automatic control of output voltage or current}
- 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 first full-bridge circuit, a transformer, a first reactor, a second full-bridge circuit, a second reactor, a capacitor, and a control unit are included. When activated, the control unit switches one or more of a combination of a first switching leg and a second switching leg and a combination of a third switching leg and a fourth switching leg with a certain second phase difference and drives first, third, fifth, and seventh switching devices or second, fourth, sixth, and eighth switching devices with a first duty ratio, which is lower than a duty ratio during normal operation.

## Claims

### Claim 1

A Direct Current (DC)-to-DC converter comprising:
a first switching leg including a first switching device and a second switching device connected to each other;
a second switching leg including a third switching device and a fourth switching device connected to each other;
a first full-bridge circuit in which the first switching leg and the second switching leg are connected in parallel with each other and that converts direct current voltage from a first input/output terminal into alternating current voltage;
a transformer;
a first reactor, having one end connected to a node between the first switching device and the second switching device and another end connected to an end of a primary winding of the transformer;
a third switching leg including a fifth switching device and a sixth switching device connected to each other;
a fourth switching leg including a seventh switching device and an eighth switching device connected to each other;
a second full-bridge circuit in which the third switching leg and the fourth switching leg are connected in parallel with each other and that converts direct current voltage from a second input/output terminal into alternating current voltage;
a second reactor, having one end connected to a node between the fifth switching device and the sixth switching device and another end connected to a secondary winding of the transformer,
wherein each of the switching devices has a respective capacitor connected in parallel; and
a control unit that:
controls power transmission by generating signals for driving the switching devices and adjusting a first phase difference between switching of the first full-bridge circuit and switching of the second full-bridge circuit, and
when activated at start-up, switches one or more of a combination of the first switching leg and the second switching leg and a combination of the third switching leg and the fourth switching leg with a certain second phase difference and drives the first, third, fifth, and seventh switching devices or the second, fourth, sixth, and eighth switching devices with a first duty ratio, is the first duty ratio lower than a duty ratio during normal operation.

### Claim 2 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the control unit, when activated at start-up, switches the first switching leg and the second switching leg with the certain second phase difference.

### Claim 3 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the control unit, when activated at start-up, switches the third switching leg and the fourth switching leg with the certain second phase difference.

### Claim 4 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the control unit, when activated at start-up, switches the combination of the first switching leg and the second switching leg and the combination of the third switching leg and the fourth switching leg with the certain second phase difference.

### Claim 5 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the control unit drives the second, fourth, sixth, and eighth switching devices using complementary signals of the signals for driving the first, third, fifth, and seventh switching devices or drives the first, third, fifth, and seventh switching devices using complementary signals of the signals for driving the second, fourth, sixth, and eighth switching devices.

### Claim 6 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the control unit performs:
a first step, in which one or more of duty ratios of the driving signals for the first, third, fifth, and seventh switching devices and duty ratios of the driving signals for the second, fourth, sixth, and eighth switching devices are increased to the first duty ratio; and
a second step, in which a third phase difference between switching of the first switching leg and switching of the second switching leg and a fourth phase difference between switching of the third switching leg and switching of the fourth switching leg are changed to 180°.

### Claim 7 (depends on 6)

The DC-to-DC converter according to claim 6, wherein, in the second step, the first phase difference between the switching of the first full-bridge circuit and the switching of the second full-bridge circuit is set such that input current becomes equal to or smaller than a certain value.

### Claim 8 (depends on 6)

The DC-to-DC converter according to claim 6, wherein the control unit performs a third step, in which output voltage is adjusted to a target voltage by controlling input current by changing the first phase difference between the switching of the first full-bridge circuit and the switching of the second full-bridge circuit.

### Claim 9 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the control unit drives the first, second, third, fourth, fifth, sixth, seventh, and eighth switching devices using signals having the first duty ratio.

### Claim 10 (depends on 9)

The DC-to-DC converter according to claim 9, wherein one or more of the driving signals for the second and fourth switching devices have same duty ratios as the driving signals for the first and third switching devices, respectively, but are out of phase with each other by 180° and the driving signals for the sixth and eighth switching devices have same duty ratios as the driving signals for the fifth and seventh switching devices, respectively, but are out of phase with each other by 180°.

### Claim 11 (depends on 9)

The DC-to-DC converter according to claim 9, wherein:
the certain second phase difference is equal to or smaller than (180°−(first duty ratio×360°)); and
the control unit performs a first step, in which one or more of duty ratios of the driving signals for the first, third, fifth, and seventh switching devices and duty ratios of the driving signals for the second, fourth, sixth, and eighth switching devices are increased to the first duty ratio, and a second step, in which the second phase difference is changed to 180°.

### Claim 12 (depends on 11)

The DC-to-DC converter according to claim 11,
wherein, in the second step, the control unit sets first phase difference between the switching of the first full-bridge circuit and the switching of the second full-bridge circuit such that input current becomes equal to or smaller than a certain value.

### Claim 13 (depends on 11)

The DC-to-DC converter according to claim 11, wherein the control unit performs a third step, in which output voltage is adjusted to a target voltage by controlling input current by changing the first phase difference between the switching of the first full-bridge circuit and the switching of the second full-bridge circuit.

### Claim 14 (depends on 13)

The DC-to-DC converter according to claim 13, wherein the control unit performs the third step by:
determining whether the output voltage has reached the target voltage within a certain period of time; and
increasing the first duty ratio if the output voltage has not reached the target voltage.

### Claim 15 (depends on 13)

The DC-to-DC converter according to claim 13, wherein the control unit performs a fourth step, in which:
the duty ratios of the driving signals for the first, third, fifth, and seventh switching devices are increased to a second duty ratio; and
the output voltage to the target voltage by changing the first phase difference between the switching of the first full-bridge circuit and the switching of the second full-bridge circuit.

### Claim 16 (depends on 1)

The DC-to-DC converter according to claim 1, wherein the certain second phase difference is 0°.

### Claim 17 (depends on 1)

The DC-to-DC converter according to claim 1, wherein, at a time of stopping, the control unit performs:
a first stopping step, in which one or more of duty ratios of the driving signals for the first, third, fifth, and seventh switching devices and duty ratios of the driving signals for the second, fourth, sixth, and eighth switching devices are decreased to a certain duty ratio; and
a second stopping step, in which a third phase difference between switching of the first switching leg and switching of the second switching leg and a fourth phase difference between switching of the third switching leg and switching of the fourth switching leg are changed to 0°.

### Claim 18 (depends on 1)

The DC-to-DC converter according to claim 1, further comprising:
a capacitor circuit including a first capacitor and a second capacitor connected in series with each other, wherein:
wherein the capacitor circuit is connected in parallel with the first full-bridge circuit, wherein a center tap is provided for the primary winding of the transformer, wherein the center tap is connected to a node between the first and second capacitors, and wherein a third reactor is connected to an end of the primary winding in which the first reactor is not connected to; or
wherein the capacitor circuit is connected in parallel with the second full-bridge circuit, wherein the center tap is provided for the secondary winding of the transformer, wherein the center tap is connected to the node between the first and second capacitors, and wherein the third reactor is connected to an end of the secondary winding in which the second reactor is not connected to.

### Claim 19 (depends on 1)

The DC-to-DC converter according to claim 1, wherein each of the switching devices has a respective diode connected in parallel.

### Claim 20 (depends on 1)

The DC-to-DC converter according to claim 1, wherein at least the first reactor or the second reactor comprises leakage inductance of the transformer.