# US 10,873,254 B2 · Electrical circuit for zero-voltage soft-switching in DC-DC converter under all load conditions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,254 B2 - Document ID: US10873254B2 - Status: Granted - Kind: B2 - Application number: 16/456,219 - Filed: 2019-06-28 - Published: 2020-01-02 - Granted: 2020-12-22 - Earliest claimed: 2018-06-29 - Assignees: Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen - Applicants: Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen - Inventors: Rik W. De Doncker - Web page: https://patentgrep.com/patent/US10873254B2 ## CPC - H02M 1/34: Snubber circuits - H02M 3/33584: {Bidirectional converters} - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 3/3376: {with automatic control of output voltage or current} - H02M 7/4833: {Capacitor voltage balancing} - H02M 1/0048: {Circuits or arrangements for reducing losses (using snubbers H02M1/34)} - 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} - H02M 1/342: {Active 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) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract An electrical circuit comprising an n-port m-phase active bridge converter with n≥2 and m≥3, where each port can be operated as an input or an output port, wherein each of the n ports has m phase legs with multiple active switches with parallel connected snubber or resonant capacitors, whereby the ports can convert a DC-voltage into an AC voltage and vice versa, whereby the ports are connected via a m-phase transformer or over m separate transformers each connected to each of the m phase legs of each of the m ports to transfer power between the ports, wherein an auxiliary circuit is connected to a star point of the transformers to feedback a fraction of a transformer input voltage and energy into a DC mid-point capacitor of a DC-link of at least one of the n-port m-phase active bridge converters to charge the DC mid-point capacitor. ## Claims ### Claim 1 An electrical circuit for zero-voltage switching of a DC-DC converter under all load conditions, comprising: an n-port m-phase active bridge converter with n≥2 and m≥3, where each of the n ports can be operated as an input or an output port, wherein each of the n ports has m phase legs with multiple active switches with parallel connected snubber capacitors, wherein the n ports can convert a DC-voltage into an AC voltage and vice versa, wherein each of then ports are connected via corresponding m-phase transformers, each m-phase transformer connected to phase legs of each of the n ports to transfer power between the n ports, and wherein an auxiliary circuit is connected to a star point of the n m-phase transformers to feed back a fraction of a transformer input voltage into a DC mid-point capacitor of a DC-link of the n-port m-phase active bridge converter in such a way that the DC mid-point capacitor is charged at a corresponding port of the n ports with an offset voltage above and below a DC-link midpoint voltage enabling the auxiliary circuit to provide under all load conditions zero-voltage soft-switching operation of the multiple active switches of the phase legs. ### Claim 2 (depends on 1) The electrical circuit according to claim 1, wherein the auxiliary circuit comprises one or more single-phase diode rectifiers and auxiliary inductances, two auxiliary switches per phase leg and one or more auxiliary capacitors, and wherein the snubber capacitors and the auxiliary inductances form a resonant circuit when one auxiliary switch is turned on, which injects an additional current into the phase legs to provide zero-voltage soft-switching under all load conditions. ### Claim 3 (depends on 2) The electrical circuit according to claim 2, wherein the auxiliary switches are zero-current switching devices that are configured to turn on the auxiliary circuit. ### Claim 4 (depends on 1) The electrical circuit according to claim 1, wherein a number of phases m is 3. ### Claim 5 (depends on 1) The electrical circuit according to claim 1, wherein the n-port m-phase active bridge converter is a two-port m-phase active bridge converter. ### Claim 6 (depends on 4) The electrical circuit according to claim 4, wherein the n-port m-phase active bridge converter is a two-port three-phase active bridge converter. ### Claim 7 (depends on 1) The electrical circuit according to claim 1, wherein the fraction of the transformer input voltage fed back into the DC mid-point capacitor of the DC-link of any port of the n ports has a maximum value that is (m−2)/m of the DC voltage. ### Claim 8 (depends on 1) The electrical circuit according to claim 1, wherein each of the n ports is connected to the auxiliary circuit to feedback a fraction of a transformer voltage into each of the n ports. ### Claim 9 (depends on 1) The electrical circuit according to claim 1, wherein a number of phases m is larger than three. ### Claim 10 (depends on 1) The electrical circuit according to claim 1, wherein an auxiliary zero-current switching circuit is added to force commutate the snubber capacitors in the n-port m-phase active bridge converter. ### Claim 11 (depends on 6) The electrical circuit according to claim 6, wherein auxiliary inductors are placed behind auxiliary switches and the auxiliary inductors comprise 2 m separate inductors for the auxiliary circuit to spread losses in the auxiliary inductors and facilitate cooling. ### Claim 12 A method of operating an electrical circuit comprising an n-port m-phase active bridge converter with n≥2 and m≥3, where each of n ports can be operated as an input or an output port, wherein each of the n ports has m phase legs with multiple active switches with parallel connected snubber capacitors, whereby the n ports can convert a DC-voltage into an AC voltage and vice versa, whereby the n ports are connected via an m-phase transformer and are each connected to each of the m phase legs of each of the n ports to transfer power between the n ports, the method comprising: feeding back a fraction of a transformer input voltage into a mid-point capacitor of a DC-link of at least one of the n ports of the n-port m-phase active bridge converter via an auxiliary circuit connected to a star point of n m-phase transformers; and providing zero-voltage soft-switching of the multiple active switches of the m phase legs at zero voltage under all load conditions. ### Claim 13 (depends on 12) The method according to claim 12, wherein a number of phases m is a number≥3. ### Claim 14 (depends on 12) The method according to claim 12, wherein the n-port m-phase active bridge converter is a two-port m-phase active bridge converter. ### Claim 15 (depends on 12) The method according to claim 12, wherein the n-port m-phase active bridge converter is a two-port three-phase active bridge converter.