# US 10,374,520 B2 · Control circuit and method for controlling a resonant converter and power inverter comprising the resonant converter and the control circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,374,520 B2 - Document ID: US10374520B2 - Status: Granted - Kind: B2 - Application number: 16/062,276 - Filed: 2016-12-16 - Published: 2018-12-27 - Granted: 2019-08-06 - Earliest claimed: 2016-03-07 - Assignees: Koninklijke Philips N.V. - Applicants: Koninklijke Philips N.V. - Inventors: Bernhard Wagner; Yuhang Cui; Jilong Han - Web page: https://patentgrep.com/patent/US10374520B2 ## CPC - H02M 3/3376: {with automatic control of output voltage or current} - H02M 3/01: {Resonant DC/DC converters} - H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop} - H02M 3/33573: {Full-bridge at primary side of an isolation transformer} - H02M 7/5387: in a bridge configuration - H05G 1/20: with high-frequency AC; with pulse trains {(pulse generators in general H03K3/00, H03K4/00)} - H05G 1/32: Supply voltage of the X-ray apparatus or tube - H05G 1/34: Anode current, heater current or heater voltage of X-ray tube - 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 3/33571: {Half-bridge at primary side of an isolation transformer} - H02M 7/4815: {Resonant converters (H02M7/4811 and H02M7/4826 take precedence)} - 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) - H05G: X-RAY TECHNIQUE (investigating or analysing materials by the use of X-rays G01N23/00; apparatus for X-ray photography G03B42/02; X-ray tubes H01J35/00; TV systems having X-ray input H04N5/321) - 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 present invention proposes a control circuit and a method of controlling a resonant converter comprising a full-bridge configuration in the following manner: during each half period of a plurality of periods of a resonant current of the resonant converter, starting from an initial state (500) in which a diagonal pair are conductive, turning off (510) a first switch member of the diagonal pair on the basis of the voltage control signal; turning on (520), after the turn-off of the first switch member, a switch member in series connection with the first switch member prior to a zero crossing (E5) of the resonant current; turning off (530), after the turn-off of the first switch member, a second switch member of the diagonal pair prior to the zero crossing (ES); and turning on (540), after the turn-off of the second switch member, a switch member in series connection with the second switch member prior to the zero crossing event of the resonant current. ## Claims ### Claim 1 A control circuit for controlling a resonant converter that includes a full-bridge configuration having two parallel switching branches, each of the two switching branches comprising two series-connected switch members, such that a switch member of one switching branch and a respective member of the other switching branch form a diagonal pair, the control circuit comprising: an output voltage controller configured for providing a voltage control signal for controlling an output voltage of the resonant converter; a zero crossing predictor configured for providing a zero crossing-predicting signal indicating zero crossing-predicting events of a resonant current of the resonant converter, each zero crossing-predicting event leading a respective zero crossing of the resonant current by a predetermined advancing time interval; and a switch encoder configured for controlling switching events of the switch members, wherein the switch encoder is configured, during each half period of a plurality of periods of the resonant current, starting from an initial state in which a diagonal pair is conductive, to: turn off a first switch member of the diagonal pair based on the voltage control signal; turn on, after the turn-off of the first switch member, a switch member in series connection with the first switch member prior to a zero crossing of the resonant current in the half period; turn off, after the turn-off of the first switch member, a second switch member of the diagonal pair at a zero crossing-predicting event leading to the zero crossing, based on the zero crossing-predicting signal; and turn on, after the turn-off of the second switch member, a switch member in series connection with the second switch member prior to the zero crossing event. ### Claim 2 (depends on 1) The control circuit of claim 1, wherein the switch encoder is further configured to turn on the switch member in series connection with the first switch member based on the zero crossing-predicting signal. ### Claim 3 (depends on 1) The control circuit of claim 1, further comprising: a first delay unit for providing a first delayed signal indicating delayed zero crossing-predicting events, each delayed zero crossing-predicting event lagging a corresponding zero crossing-predicting event by a first predetermined delay time and being prior to a corresponding zero crossing of the resonant current; wherein the switch encoder is further configured to turn off the switch member in series connection with the second switch member at a delayed zero crossing-predicting event based on the first delayed signal. ### Claim 4 (depends on 3) The control circuit of claim 3, wherein the first delay unit is configured to provide the first delayed signal by delaying the zero crossing-predicting signal. ### Claim 5 (depends on 3) The control circuit of claim 3, wherein the switch encoder is further configured to turn on the switch member in series connection with the first switch member at a delayed zero crossing predicting event based on the first delayed signal. ### Claim 6 (depends on 1) The control circuit of claim 1, further comprising: a second delay unit for providing a second delayed signal indicating events which lag the turn-off of the first switch member by a second predetermined delay time and which are prior to the zero crossing event; wherein the switch encoder is further configured to turn on the switch member in series connection with the first switch member based on the second delayed signal. ### Claim 7 (depends on 6) The control circuit of claim 6, wherein the second delay unit is configured to provide the second delayed signal by delaying the voltage control signal. ### Claim 8 (depends on 1) The control circuit of claim 1, wherein the switch member turned off first on the basis of the voltage control signal in a first period of the resonant current is different from the switch member turned off first on the basis of the voltage control signal in a second period of the resonant current. ### Claim 9 (depends on 1) The control circuit of claim 1, wherein the switch encoder comprises: a synchronous sawtooth generator for providing a sawtooth signal based on the zero crossing-predicting signal; a comparator for providing a phase signal based on the voltage control signal and the sawtooth signal; and a digital encoder for providing a drive signal for each switch member based on of the phase signal. ### Claim 10 (depends on 1) The control circuit of claim 1, wherein the switch encoder comprises: a zero crossing predictor for providing a synchronizing signal based on the zero crossing-predicting signal and the zero crossings of the resonant current; a counter for providing a phase signal based on the voltage control signal and the synchronizing signal; and a digital encoder for providing a drive signal for each switch member based on of the phase signal. ### Claim 11 A method of controlling a resonant converter, comprising: providing a full-bridge configuration having two parallel switching branches, each of the two switching branches comprising two series-connected switch members, such that a switch member of one switching branch and a respective member of the other switching branch form a diagonal pair; providing a voltage control signal for controlling an output voltage of the resonant converter; providing a zero crossing-predicting signal indicating zero crossing-predicting events of a resonant current of the resonant converter, each zero crossing-predicting event leading a respective zero crossing of the resonant current by a predetermined advancing time interval; during each half period of a plurality of periods of the resonant current, starting from an initial state in which a diagonal pair is conductive, turning off a first switch member of the diagonal pair based on the voltage control signal; turning on, after the turn-off of the first switch member, a switch member in series connection with the first switch member prior to a zero crossing of the resonant current in the half period; turning off, after the turn-off of the first switch member, a second switch member of the diagonal pair at a zero crossing-redicting event leading to the zero crossing based on the zero crossing-predicting signal; and turning on, after the turn-off of the second switch member, a switch member in series connection with the second switch member prior to the zero crossing event. ### Claim 12 A power inverter, comprising: a resonant converter comprising: a full-bridge configuration having two parallel switching branches, each of the two switching branches comprising two series-connected switch members, such that a switch member of one switching branch and a respective member of the other switching branch form a diagonal pair; and a resonant circuit connected between junctions of the two series-connected switch members of each of the two switching branches; and a control circuit configured for controlling the resonant converter, comprising: an output voltage controller configured for providing a voltage control signal for controlling an output voltage of the resonant converter; a zero crossing predictor configured for providing a zero crossing-predicting signal indicating zero crossing-predicting events of a resonant current of the resonant converter, each zero crossing-predicting event leading a respective zero crossing of the resonant current by a predetermined advancing time interval; a switch encoder configured for controlling switching events of the switch members, wherein the switch encoder is configured, during each half period of a plurality of periods of the resonant current, starting from an initial state in which a diagonal pair is conductive, to: turn off a first switch member of the diagonal pair based on the voltage control signal; turn on, after the turn-off of the first switch member, a switch member in series connection with the first switch member prior to a zero crossing of the resonant current in the half period; turn off, after the turn-off of the first switch member, a second switch member of the diagonal pair at a zero crossing-predicting event leading to the zero crossing, based on the zero crossing-predicting signal; and turn on, after the turn-off of the second switch member, a switch member in series connection with the second switch member prior to the zero crossing event. ### Claim 13 (depends on 12) The power inverter of claim 12, wherein at least one of the switch members is connected in parallel to a snubber capacitor. ### Claim 14 An x-ray generator, comprising: a power inverter comprising: a resonant converter comprising: a full-bridge configuration having two parallel switching branches, each of the two switching branches comprising two series-connected switch members, such that a switch member of one switching branch and a respective member of the other switching branch form a diagonal pair; and a resonant circuit connected between junctions of the two series-connected switch members of each of the two switching branches; and a control circuit configured for controlling the resonant converter, comprising: an output voltage controller configured for providing a voltage control signal for controlling an output voltage of the resonant converter; a zero crossing predictor configured for providing a zero crossing-predicting signal indicating zero crossing-predicting events of a resonant current of the resonant converter, each zero crossing-predicting event leading a respective zero crossing of the resonant current by a predetermined advancing time interval; a switch encoder configured for controlling switching events of the switch members, wherein the switch encoder is configured, during each half period of a plurality of periods of the resonant current, starting from an initial state in which a diagonal pair is conductive, to: turn off a first switch member of the diagonal pair based on the voltage control signal; turn on, after the turn-off of the first switch member, a switch member in series connection with the first switch member prior to a zero crossing of the resonant current in the half period; turn off, after the turn-off of the first switch member, a second switch member of the diagonal pair at a zero crossing-predicting event leading to the zero crossing, based on the zero crossing-predicting signal; and turn on, after the turn-off of the second switch member, a switch member in series connection with the second switch member prior to the zero crossing event; a DC voltage source connected to an input of the power inverter; and an x-ray tube connected to an output of the power inverter.