# US 10,770,979 B2 · LLC resonant converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,770,979 B2 - Document ID: US10770979B2 - Status: Granted - Kind: B2 - Application number: 16/482,718 - Filed: 2017-11-20 - Published: 2020-01-02 - Granted: 2020-09-08 - Earliest claimed: 2017-03-31 - Assignees: OMRON Corporation - Applicants: OMRON Corporation - Inventors: Mitsuru Sato; Shingo Nagaoka; Hiroyuki Onishi - Web page: https://patentgrep.com/patent/US10770979B2 ## CPC - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters - H02M 1/36: Means for starting or stopping converters - H02M 3/01: {Resonant DC/DC converters} - H02M 3/33571: {Half-bridge at primary side of an isolation transformer} - H02M 1/0009: {Devices or circuits for detecting current in a converter} - 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 1/325: {with means for allowing continuous operation despite a fault, i.e. fault tolerant converters} - H02M 1/4208: {Arrangements for improving power factor of AC input} - H02M 7/4818: {with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuits} - 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 - Y02P 80/10: Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier - 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 - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The LLC resonant converter includes a bridge circuit configured to receive a DC input voltage, an LLC resonant circuit connected to the bridge circuit, a transformer connected to the LLC resonant circuit, a rectifier circuit connected to the transformer and configured to send out a converted DC voltage, a resonant capacitor changeover circuit, a bridge circuit control section, and a resonant capacitor changeover control section. When the input voltage exceeds a changeover voltage, the operating frequency is raised higher than the resonance frequency, and thereafter the switch is turned off. ## Claims ### Claim 1 An LLC resonant converter comprising: a bridge circuit configured to receive a DC input voltage and to send out a square-wave voltage by a switching operation of a switching element; an LLC resonant circuit having at least a first capacitor and configured to resonate on receiving the square-wave voltage; a transformer having a primary side connected to the LLC resonant circuit and a secondary side isolated from the primary side; a rectifier element configured to convert an output from the secondary side of the transformer into a DC output voltage; a smoothing capacitor configured to smooth the output voltage from the rectifier element; a resonant capacitor changeover circuit having a changeover switch and a second capacitor that are connected in series to each other and connected in parallel to the first capacitor; an input voltage detection circuit configured to detect the input voltage; an output voltage detection circuit configured to detect the output voltage; an output current detection circuit configured to detect an output current fed to a load; a resonant capacitor changeover control section configured to control a state of the changeover switch in the resonant capacitor changeover circuit, based on at least one of the input voltage detected by the input voltage detection circuit, the output voltage detected by the output voltage detection circuit, and the output current detected by the output current detection circuit; and a bridge circuit control section configured to control the switching operation of the switching element by pulse frequency modulation, and to control an operating frequency of the switching element such that the detected output voltage reaches a desired voltage or in response to a command from the resonant capacitor changeover control section, wherein the resonant capacitor changeover control section is configured: to turn on the changeover switch when the detected input voltage gets lower than a changeover voltage, wherein the resonant capacitor changeover control section is configured: when the detected input voltage exceeds the changeover voltage, to send a command to the bridge circuit control section to suspend control of the operating frequency for bringing the detected output voltage to the desired voltage and to raise the operating frequency to a changeover frequency; then, to turn off the changeover switch; and thereafter, to send a command to the bridge circuit control section to resume the operating frequency control for bringing the detected output voltage to the desired voltage, wherein the changeover frequency is higher than a first resonance frequency at which a gain of the LLC resonant circuit is maximum while the changeover switch is off, the first resonance frequency being obtained from the detected output voltage and the detected output current, and wherein a required time between the suspension and the resumption of the operating frequency control for bringing the detected output voltage to the desired voltage is shorter than at least a retention time during which an output of the LLC resonant converter can be maintained after supply of the input voltage has stopped. ### Claim 2 (depends on 1) The LLC resonant converter according to claim 1, wherein the changeover frequency is higher than a second resonance frequency at which the gain of the LLC resonant circuit is 1 while the changeover switch is off.