# US 2006/0077700 A1 · High-efficiency adaptive DC/AC converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2006/0077700 A1 - Document ID: US20060077700A1 - Status: Published application - Kind: A1 - Application number: 11/282,873 - Filed: 2005-11-17 - Published: 2006-04-13 - Earliest claimed: 2002-04-24 - Assignees: O2 International Limited - Inventors: Yung-Lin Lin - Web page: https://patentgrep.com/patent/US20060077700A1 ## CPC - H02M 7/53871: {with automatic control of output voltage or current} - H05B 41/2828: {using control circuits for the switching elements (H05B41/2827 takes precedence)} - H05B 41/2855: {against abnormal lamp operating conditions} - H02M 1/0032: {Control circuits allowing low power mode operation, e.g. in standby mode} - H02M 7/4815: {Resonant converters (H02M7/4811 and H02M7/4826 take precedence)} - Y02B 20/00: Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps - 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) - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A CCFL power converter circuit is provided using a high-efficiency zero-voltage-switching technique that eliminates switching losses associated with the power MOSFETs. An optimal sweeping-frequency technique is used in the CCFL ignition by accounting for the parasitic capacitance in the resonant tank circuit. Additionally, the circuit is self-learning and is adapted to determine the optimum operating frequency for the circuit with a given load. An over-voltage protection circuit can also be provided to ensure that the circuit components are protected in the case of open-lamp condition. ## Claims ### Claim at position 1 1-60. (canceled) ### Claim 61 A DC to AC inverter circuit, comprising: an input voltage source; a plurality of switches being selectively coupled to said voltage source; a transformer having a primary side and a secondary side, said primary side being selectively coupled to said voltage source in an alternating fashion through said switches; a load coupled to said secondary side of said transformer; and a feedback control loop circuit receiving a feedback signal indicative of power being supplied to the load and adapted to control the conduction state of at least one of said switches so that said switches have a plurality of conduction states comprising a first state in which said switches deliver an amount of power to said load determined by said feedback signal, and a second state in which said switches deliver a predetermined minimum power to the load. ### Claim 62 (depends on 61) An inverter circuit as claimed in claim 61, wherein said feedback control loop circuit comprises: an error amplifier comparing said feedback signal to a predetermined reference signal and generating an error signal indicative of the difference between said feedback signal and said predetermined reference signal; and a flow-through switch coupled to said error amplifier and having a first conduction state wherein the output of said flow-through switch comprises a DC signal indicative of said first state of said switches, and a second conduction state wherein the output of said flow-through switch comprises a DC signal indicative of said second state of said switches. ### Claim 63 (depends on 62) An inverter circuit as claimed in claim 62, further comprising protection circuitry comprising a current sense comparator, said current sense comparator comparing said feedback signal to a second reference signal; wherein if the compared value of said feedback signal and said second reference signal is within a predetermined range said current sense comparator generates a first control signal to control the conduction state of said switch corresponding to said first conduction state; and wherein if the compared value of said feedback signal is outside a predetermined range said current sense comparator generates a second control signal to control the conduction state of said switch corresponding to said second conduction state. ### Claim 64 (depends on 61) An inverter circuit as claimed in claim 61, further comprising a sense resistor coupled between said load and said secondary side of said transformer, said sense resistor generating said feedback signal. ### Claim 65 (depends on 63) An inverter circuit as claimed in claim 63, wherein said protection circuitry further comprising an overvoltage protection circuit comprising a voltage comparator comparing a predetermined voltage reference to a voltage signal indicative of load voltage conditions and generating a voltage control signal. ### Claim 66 (depends on 62) An inverter circuit as claimed in claim 62, wherein said reference signal represents desired load conditions. ### Claim 67 (depends on 63) An inverter circuit as claimed in claim 63, wherein said second reference signal represents the minimum or maximum current permitted by said switches and/or said load. ### Claim 68 (depends on 65) An inverter circuit as claimed in claim 65, wherein said voltage control signal represents the maximum voltage at said secondary side of said transformer. ### Claim 69 An inverter circuit for converting a DC voltage source to an AC voltage source to power a load, comprising: a plurality of switches being selectively coupled to said DC voltage source; and a feedback control loop circuit receiving a feedback signal indicative of power being supplied to said load and adapted to control the conduction state of at least one of said switches so that said switches have a conduction state in which said switches deliver an amount of power to said load determined by said feedback signal when said feedback signal is greater than a predetermined threshold. ### Claim 70 (depends on 69) An inverter circuit as claimed in claim 69, wherein said conduction state of said switches further comprises a second state in which said switches are controlled to deliver a predetermined minimum power to the load. ### Claim 71 (depends on 70) An inverter circuit as claimed in claim 70, wherein said second state occurs if said feedback signal is below said predetermined threshold. ### Claim 72 A DC to AC inverter circuit comprising: a plurality of switches being controlled in an alternating fashion; and a feedback control loop circuit receiving a feedback signal indicative of power being supplied to a load and adapted to control the conduction state of at least one of said switches so that said switches have a conduction state to deliver a predetermined minimum power to the load. ### Claim 73 An inverter circuit comprising: a plurality of switches being controlled in an alternating fashion; and a feedback control loop circuit receiving a feedback signal indicative of power being supplied to a load and adapted to control the conduction state of at least one of said switches so that said switches have overlapping conduction states, said overlapping conduction states comprise a first state in which said switches deliver an amount of power to said load determined by said feedback signal when said feed back signal is greater than a predetermined threshold; and a second state in which said switches deliver a predetermined minimum power to the load.