# US 2014/0153288 A1 · Dc-dc converter with lc resonance circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153288 A1 - Document ID: US20140153288A1 - Status: Published application - Kind: A1 - Application number: 14/177,269 - Filed: 2014-02-11 - Published: 2014-06-05 - Earliest claimed: 2011-08-18 - Assignees: Fujitsu Limited - Applicants: Fujitsu Limited - Inventors: Yu Yonezawa; YOSHIYASU NAKASHIMA - Web page: https://patentgrep.com/patent/US20140153288A1 ## CPC - H02M 3/33569: {having several active switching elements (H02M3/3353 takes precedence)} - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - 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 3/01: {Resonant DC/DC converters} - 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 A DC-DC converter includes a capacitor configured to be charged for a predetermined period by an external voltage, an inductor configured to constitute an LC resonance circuit together with the capacitor, a closed-loop current path configured to release energy accumulated in the capacitor after the predetermined period to cause a current flowing in the LC resonance circuit to oscillate, a transformer configured to receive a current flowing in the closed-loop current path, and a rectifying circuit situated on an output side of the transformer. ## Claims ### Claim 1 A DC-DC converter, comprising: a capacitor configured to be charged for a predetermined period by an external voltage; an inductor configured to constitute an LC resonance circuit together with the capacitor; a closed-loop current path configured to release energy accumulated in the capacitor after the predetermined period to cause a current flowing in the LC resonance circuit to oscillate; a transformer configured to receive a current flowing in the closed-loop current path; and a rectifying circuit situated on an output side of the transformer. ### Claim 2 (depends on 1) The DC-DC converter as claimed in claim 1, further comprising: a first switch circuit situated in a path outside the closed-loop current path, the first switch circuit configured to be conductive during the predetermined period to supply a charge current to the capacitor and to be nonconductive outside the predetermined time period; and a second switch circuit situated in the closed-loop current path, the second switch circuit configured to alternate between a conductive state and a nonconductive state and to be nonconductive at least when the first switch circuit is conductive. ### Claim 3 (depends on 2) The DC-DC converter as claimed in claim 2, further comprising a second inductor situated in the path outside the closed-loop current path and series-connected with the first switch circuit, the charge current flowing through the second inductor. ### Claim 4 (depends on 3) The DC-DC converter as claimed in claim 3, further comprising: a second closed-loop current path including the second inductor and the capacitor; and a third switch circuit situated in the second closed-loop current path, the third switch circuit configured to alternate between a conductive state and a nonconductive state and to be nonconductive at least when the first switch circuit is conductive. ### Claim 5 (depends on 1) The DC-DC converter as claimed in claim 1, further comprising a control circuit configured to perform feedback control with respect to the predetermined period in response to a voltage responsive to an output of the rectifying circuit. ### Claim 6 (depends on 1) The DC-DC converter as claimed in claim 1, further comprising a control circuit configured to set the predetermined period equal to a length calculated in response to a target output voltage. ### Claim 7 (depends on 2) The DC-DC converter as claimed in claim 2, wherein the second switch circuit is changed from a conductive state to a nonconductive state at a moment at which the current flowing in the closed-loop current path including the second switch circuit becomes zero. ### Claim 8 (depends on 7) The DC-DC converter as claimed in claim 7, further comprising a current detector configured to detect a current flowing in the closed-loop current path including the second switch circuit, the second switch circuit being changed from a conductive state to a nonconductive state in response to a result of detection made by the current detector. ### Claim 9 (depends on 1) The DC-DC converter as claimed in claim 1, wherein the rectifying circuit further includes a rectification-purpose switch circuit, which is made conductive and nonconductive at such times as are calculated in response to a resonance frequency of the LC resonance circuit. ### Claim 10 (depends on 4) The DC-DC converter as claimed in claim 4, further comprising a diode situated in parallel to the third switch circuit, the third switch circuit being a transistor having no parasitic diode. ### Claim 11 A DC-DC conversion method, comprising: charging a capacitor with an external voltage for a predetermined period; releasing energy accumulated in the capacitor after the predetermined period to cause a current to flow and oscillate in a closed-loop current path inclusive of an LC resonance circuit that includes the capacitor and an inductor; supplying the current flowing in the closed-loop current path to a transformer; and rectifying an output of the transformer. ### Claim 12 An information apparatus, comprising: a DC-DC converter; a CPU; and a memory device, wherein the DC-DC converter includes: a capacitor configured to be charged for a predetermined period by an external voltage; an inductor configured to constitute an LC resonance circuit together with the capacitor; a closed-loop current path configured to release energy accumulated in the capacitor after the predetermined period to cause a current flowing in the LC resonance circuit to oscillate; a transformer configured to receive a current flowing in the closed-loop current path; and a rectifying circuit situated on an output side of the transformer.