# US 12,603,582 B2 · Bidirectional low DC-DC converter including lossless snubber circuit, control method of bidirectional LDC and bidirectional LDC system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,603,582 B2 - Document ID: US12603582B2 - Status: Granted - Kind: B2 - Application number: 18/385,081 - Filed: 2023-10-30 - Published: 2024-06-20 - Granted: 2026-04-14 - Earliest claimed: 2022-12-16 - Assignees: Hl Mando Corporation - Applicants: Hl Mando Corporation - Inventors: AnYeol Jung; Minseuk Oh - Web page: https://patentgrep.com/patent/US12603582B2 ## CPC - H02M 3/33584: {Bidirectional converters} - H02M 1/342: {Active non-dissipative snubbers} - H02M 3/3353: {having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter} - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 1/34: Snubber circuits - 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 According to an embodiment of the present disclosure, provided is a bidirectional LDC (Low DC-DC Converter) having opposite ends connected to a high voltage battery and a low voltage battery, respectively, and including a lossless snubber circuit, wherein, when any one of a first synchronous rectifier and a second synchronous rectifier is turned on, a voltage of a low voltage side connected to the low voltage battery is stepped up and transmitted to a high voltage side connected to the high voltage battery. When the first synchronous rectifier and the second synchronous rectifier are turned off, a first switch of the lossless snubber circuit is turned on to perform a voltage clamping operation and a freewheeling operation. ## Claims ### Claim 1 A bidirectional LDC (Low DC-DC Converter) having opposite ends connected to a high voltage battery and a low voltage battery, respectively, and comprising a lossless snubber circuit, wherein the bidirectional LDC is configured to: when any one of a first synchronous rectifier and a second synchronous rectifier is turned on, boost a voltage of a low voltage side connected to the low voltage battery and transmit the voltage to a high voltage side connected to the high voltage battery; and when the first synchronous rectifier and the second synchronous rectifier are turned off, turn a first switch of the lossless snubber circuit on to perform a voltage clamping operation and a freewheeling operation. ### Claim 2 (depends on 1) The bidirectional LDC of claim 1, wherein the lossless snubber circuit comprises: the first switch; a voltage clamping circuit connected to a front end of the first switch and including two diodes and a first capacitor; and a freewheeling circuit connected to a rear end of the first switch and including one diode and an inductor. ### Claim 3 (depends on 2) The bidirectional LDC of claim 2 further comprising: a second capacitor connected in parallel with the high voltage side and configured to charge a supplied voltage; a first switching unit connected in parallel with the second capacitor and comprising a plurality of switches configured as a full-bridge; a second switching unit comprising the first synchronous rectifier and the second synchronous rectifier; a transformer comprising a primary coil connected to the first switching unit and a secondary coil connected to the second switching unit; and a third capacitor connected in parallel with the low voltage side and configured to charge a supplied voltage. ### Claim 4 (depends on 3) The bidirectional LDC of claim 3, wherein when the second switching unit is turned on in a step-up mode, a voltage charged to the third capacitor is stepped up by the transformer and transmitted to the second capacitor. ### Claim 5 (depends on 3) The bidirectional LDC of claim 3, wherein when the first switching unit performs a full-bridge operation in a step-down mode, a voltage charged to the second capacitor is stepped down by the transformer and transmitted to the third capacitor. ### Claim 6 (depends on 3) The bidirectional LDC of claim 3, wherein when the second switching unit is turned off, an induced voltage generated by the transformer is clamped by the voltage clamping circuit to a first voltage corresponding to the first capacitor as the first switch is turned on. ### Claim 7 (depends on 3) The bidirectional LDC of claim 3, wherein when the second switching unit is turned on, a residual current flows through a loop composed of the freewheeling circuit and the third capacitor. ### Claim 8 (depends on 1) The bidirectional LDC of claim 1, wherein the first synchronous rectifier, the second synchronous rectifier, and the first switch are turned on or off based on a control signal received from a processor. ### Claim 9 (depends on 8) The bidirectional LDC of claim 8, wherein when a switching duty of the first synchronous rectifier and the second synchronous rectifier is less than 0.5, the first switch is turned on based on a control signal received from the processor. ### Claim 10 A method for controlling a bidirectional LDC (Low DC-DC Converter) having opposite ends connected to a high voltage battery and a low voltage battery, respectively, and comprising a lossless snubber circuit, comprising: stepping up a voltage of a low voltage side connected to the low voltage battery and transmitting the voltage to a high voltage side connected to the high voltage battery when any one of a first synchronous rectifier and a second synchronous rectifier is turned on; and turning on a first switch of the lossless snubber circuit to perform a voltage clamping operation and a freewheeling operation when the first synchronous rectifier and the second synchronous rectifier are turned off. ### Claim 11 (depends on 10) The method for controlling a bidirectional LDC of claim 10, wherein the lossless snubber circuit comprises: the first switch; a voltage clamping circuit connected to a front end of the first switch and including two diodes and a first capacitor; and a freewheeling circuit connected to a rear end of the first switch and including one diode and an inductor. ### Claim 12 (depends on 11) The method for controlling a bidirectional LDC of claim 11, wherein the bidirectional LDC further comprises: a second capacitor connected in parallel with the high voltage side and configured to charge a supplied voltage; a first switching unit connected in parallel with the second capacitor and comprising a plurality of switches configured as a full-bridge; a second switching unit comprising the first synchronous rectifier and the second synchronous rectifier; a transformer comprising a primary coil connected to the first switching unit and a secondary coil connected to the second switching unit; and a third capacitor connected in parallel with the low voltage side and configured to charge a supplied voltage. ### Claim 13 (depends on 12) The method for controlling a bidirectional LDC of claim 12, wherein the step of transmitting to a high voltage side comprises stepping up, by the transformer, a voltage charged to the third capacitor and transmitting to the second capacitor when the second switching unit is turned on in a step-up mode. ### Claim 14 (depends on 12) The method for controlling a bidirectional LDC of claim 12, further comprising stepping down, by the transformer, a voltage charged to the second capacitor and transmitting to the third capacitor when the first switching unit performs a full-bridge operation in a step-down mode. ### Claim 15 (depends on 12) The method for controlling a bidirectional LDC of claim 12, wherein the step of performing a voltage clamping operation and a freewheeling operation comprises, when the second switching unit is turned off, clamping, by the voltage clamping circuit, an induced voltage generated by the transformer to a first voltage corresponding to the first capacitor as the first switch is turned on. ### Claim 16 (depends on 12) The method for controlling a bidirectional LDC of claim 12, wherein when the second switching unit is turned on, a residual current flows through a loop composed of the freewheeling circuit and the third capacitor. ### Claim 17 (depends on 10) The method for controlling a bidirectional LDC of claim 10, wherein the first synchronous rectifier, the second synchronous rectifier, and the first switch are turned on or off based on a control signal received from a processor control method. ### Claim 18 (depends on 17) The method for controlling a bidirectional LDC of claim 17, wherein when a switching duty of the first synchronous rectifier and the second synchronous rectifier is less than 0.5, the first switch is turned on based on a control signal received from the processor control method. ### Claim 19 A bidirectional LDC (Low DC-DC Converter) system, comprising: a bidirectional LDC configured to: step up a voltage of a low voltage side connected to a low voltage battery and transmit to a high voltage side connected to a high voltage battery when any one of a first synchronous rectifier and a second synchronous rectifier is turned on, and turn on a first switch of a lossless snubber circuit to perform a voltage clamping operation and a freewheeling operation when the first synchronous rectifier and the second synchronous rectifier are turned off; and a processor configured to control the first synchronous rectifier, the second synchronous rectifier, and the first switch to be turned on or off. ### Claim 20 (depends on 19) The bidirectional LDC system of claim 19, wherein the processor is configured to: identify a switching duty of the first synchronous rectifier and the second synchronous rectifier according to a voltage of the high voltage battery and the low voltage battery, respectively, and activate the lossless snubber circuit when the switching duty is less than 0.5.