# US 2019/0245455 A1 · Dc-dc converter and method for controlling a dc-dc converter

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- Number: US 2019/0245455 A1
- Document ID: US20190245455A1
- Status: Published application
- Kind: A1
- Application number: 16/342,661
- Filed: 2017-09-20
- Published: 2019-08-08
- Earliest claimed: 2016-10-18
- Assignees: Robert Bosch GmbH
- Applicants: Robert Bosch GmbH
- Inventors: Emiliano Gudino Carrizales
- Web page: https://patentgrep.com/patent/US20190245455A1

## CPC

- H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer}
- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H02M 3/3376: {with automatic control of output voltage or current}
- H02M 1/0051: {Diode reverse recovery losses}
- H02M 1/0058: {by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826)}
- H02M 1/0064: {Magnetic structures combining different functions, e.g. storage, filtering or transformation}
- 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

The present invention relates to a DC-DC converter and to a method for controlling a DC-DC converter with high dielectric strength and reduced power losses. An optimized control of a potential-isolating multi-level half-bridge converter according to a phase-shifted full-bridge configuration with a novel modulation method is proposed.

## Claims

### Claim 1

A DC-DC converter (1), comprising
a first input connection (E1);
a second input connection (E2);
a first switching element (S1) which is arranged between the first input connection (E1) and a first node point (K1);
a second switching element (S2) which is arranged between the first input connection (E1) and a second node point (K2);
a third switching element (S3) which is arranged between the first node point (K1) and the second input connection (E2);
a fourth switching element (S4) which is arranged between the second node point (K2) and the second input connection (E2),
freewheeling diodes (D1-D4) arranged parallel to each of the switching elements (S1-S4);
a transformer (T) with a primary side and a secondary side, wherein a first connection of the primary side is electrically coupled to the first node point (K1) and a second connection of the primary side is electrically coupled to the second node point (K2);
a first inductance (L1) positioned between a first connection of the secondary side of the transformer (T) and a third node point (K3);
a rectifier circuit (10) configured to rectify an electrical voltage which is applied between the third node point (K3) and a second connection of the secondary side of the transformer and to provide the rectified voltage between a first output connection (A1) and a second output connection (A2); and
a control device (20) configured
to open the second switching element (S2) and the third switching element (S3);
to close the first switching element (S1) and the fourth switching element (S4);
to subsequently open the fourth switching element (S4) after a predetermined first time period (t1);
to then open the first switching element (S1) once an electric current through the first switching element (S1) and/or an electric current through the secondary side of the transformer (T) fall/falls below a prespecified threshold value;
to subsequently close the second switching element (S2) and the third switching element (S3) after a predetermined second time period (t2);
to subsequently open the third switching element (S3) after the predetermined first time period (t1);
to then open the second switching element (S2) once an electric current through the second switching element (S2) and/or an electric current through the secondary side of the transformer (T) fall/falls below the prespecified threshold value.

### Claim 2 (depends on 1)

The DC-DC converter (1) as claimed in claim 1, wherein an input voltage (Uin) between the first input connection (E1) and the second input connection (E2) is smaller than the product of a transformation ratio between the primary side and the secondary side of the transformer (T) and a setpoint output voltage (Uout) which is to be output between the first output connection (A1) and the second output connection (A2).

### Claim 3 (depends on 1)

The DC-DC converter (1) as claimed in claim 1, wherein the predetermined first time period (t1) is adjusted depending on the input voltage (Uin) and the setpoint output voltage (Uout).

### Claim 4 (depends on 1)

The DC-DC converter (1) as claimed in claim 1, wherein the rectifier circuit (10) comprises an active synchronous rectifier circuit.

### Claim 5 (depends on 4)

The DC-DC converter (1) as claimed in claim 4, wherein the control device (20) is further configured to control additional switching elements (S5-S8) of the rectifier circuit depending on the switching states of the first switching element (S1) and of the second switching element (S2).

### Claim 6 (depends on 1)

The DC-DC converter (1) as claimed in claim 1, comprising a current sensor configured to detect an electric current through the secondary side of the transformer (T) and/or to detect an electric current through the first switching element (S1) and also through the second switching element (S2).

### Claim 7

A method (100) for controlling a DC-DC converter (1), comprising a first input connection (E1), a second input connection (E2), a first switching element (S1) which is arranged between the first input connection (E1) and a first node point (K1), a second switching element (S2) which is arranged between the first input connection (E1) and a second node point (K2), a third switching element (S3) which is arranged between the first node point (K1) and the second input connection (E2), a fourth switching element (S4) which is arranged between the second node point (K2) and the second input connection (E2), wherein a freewheeling diode (D1-D4) is arranged parallel in relation to each of the switching elements (S1-S4), a transformer (T) with a primary side and a secondary side, wherein a first connection of the primary side is electrically coupled to the first node point (K1) and a second connection of the primary side is electrically coupled to the second node point (K2), a first inductance (L1) which is arranged between a first connection of the secondary side of the transformer (T) and a third node point (K3), a rectifier circuit (10) which is designed to rectify an electrical voltage between the third node point (K3) and a second connection of the secondary side of the transformer (T), and to provide the rectified voltage between a first output connection (A1) and a second output connection (A2), wherein the method comprises:
opening (110) the second switching element (S2) and the third switching element (S3);
closing (120) the first switching element (S1) and the fourth switching element (S4);
opening (130) the fourth switching element (S4) once the fourth switching element (S4) has been closed for a predetermined first time period (t1);
monitoring (140) an electric current through the first switching element (S1) and/or an electric current through the secondary side of the transformer (T);
opening (150) the first switching element (S1) once the monitored electric current through the first switching element (S1) and/or through the secondary side of the transformer (T) is smaller than a prespecified threshold value;
closing (160) the second switching element (S2) and the third switching element (S3) once the first switching element (S1) has been open for a predetermined second time period (t2);
opening (170) the third switching element (S3) once the third switching element (S3) has been closed for the predetermined first time period (t1);
monitoring (180) an electric current through the second switching element (S2) and/or an electric current through the secondary side of the transformer (T); and
opening (190) the second switching element (S2) once the monitored electric current through the second switching element (S2) and/or through the secondary side of the transformer (T) is smaller than the prespecified threshold value.

### Claim 8 (depends on 7)

The method (100) as claimed in claim 7, wherein the second time period (t2) is adjusted depending on a dead time of the first switching element (S1) and a dead time of the second switching element (S2).

### Claim 9 (depends on 1)

The DC-DC converter (1) as claimed in claim 1, wherein the predetermined first time period (t1) is adjusted depending on the input voltage (Uin).

### Claim 10 (depends on 1)

The DC-DC converter (1) as claimed in claim 1, wherein the predetermined first time period (t1) is adjusted depending on the setpoint output voltage (Uout).

### Claim 11 (depends on 7)

The method (100) as claimed in claim 7, wherein the second time period (t2) is adjusted depending on a dead time of the first switching element (S1).

### Claim 12 (depends on 7)

The method (100) as claimed in claim 7, wherein the second time period (t2) is adjusted depending on a dead time of the second switching element (S2).