# US 10,320,283 B1 · Resonant converter with pre-charging circuit for startup protection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,320,283 B1 - Document ID: US10320283B1 - Status: Granted - Kind: B1 - Application number: 16/032,145 - Filed: 2018-07-11 - Granted: 2019-06-11 - Earliest claimed: 2018-01-26 - Assignees: Universal Lighting Technologies, Inc. - Applicants: Universal Lighting Technologies, Inc. - Inventors: Wei Xiong - Web page: https://patentgrep.com/patent/US10320283B1 ## CPC - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 1/088: for the simultaneous control of series or parallel connected semiconductor devices - H02M 1/36: Means for starting or stopping converters - H02M 3/158: including plural semiconductor devices as final control devices for a single load - H05B 45/39: Circuits containing inverter bridges - H05B 47/10: Controlling the light source - 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)} - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - 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 power converter as disclosed herein includes circuitry to reduce switching current spikes as conventionally appear at startup, and control the current spikes in a predictable way, thereby improving reliability of the power converter. A controller generates drive signals to half-bridge switching elements, an output therefrom corresponding to a frequency of the gate drive signals. A resonant tank comprises a resonant capacitor, DC blocking capacitor, a resonant inductor, and a load. Pre-charge circuitry is coupled to the resonant tank and, after initially receiving power from the DC power source and prior to controller startup, pre-charges at least the DC blocking capacitor to a steady state operating value. By pre-charging the DC blocking capacitor to its steady state voltage even before startup of the controller, AC current is introduced into the resonant inductor after the low-side switching element is first turned on and soft switching is provided throughout. ## Claims ### Claim 1 A power converter comprising: first and second switching elements coupled in series between a positive rail of a DC power source and a circuit ground; a controller configured to generate drive signals to the switching elements, wherein an output from the switching elements corresponds to a frequency of the gate drive signals; a resonant circuit comprising first and second capacitors, a resonant inductor, and output terminals for receiving a load; and a pre-charge circuit coupled to the resonant tank and configured, after initially receiving power from the DC power source and prior to startup of the controller, to pre-charge at least one of the first and second capacitors in the resonant circuit to a steady state charge value for the at least one of the first and second capacitors, wherein the steady state charge value corresponds to one half of a voltage across the positive rail and the circuit ground. ### Claim 2 (depends on 1) The power converter of claim 1, wherein the at least one of the first and second capacitors is configured, after startup of the controller and an initial turning on of the second switching element, to discharge through the resonant inductor and the second switching element. ### Claim 3 (depends on 1) The power converter of claim 1, wherein: the resonant inductor and the first capacitor are coupled in series on a first end to a node between the first and second switching elements and on a second end to a circuit ground, the second capacitor and the load are coupled in series on a first end to a node between the resonant inductor and the first capacitor, and the pre-charge circuit comprises a first resistor coupled between a positive rail of the DC power source and the node between the resonant inductor and the first capacitor, and a second resistor coupled between the circuit ground and the node between the resonant inductor and the first capacitor. ### Claim 4 (depends on 3) The power converter of claim 3, wherein the pre-charge circuit is configured to pre-charge the second capacitor to a steady state charge value of one half a voltage across the positive rail and the circuit ground. ### Claim 5 (depends on 3) The power converter of claim 3, wherein the first and second resistors are provided with equivalent resistance values. ### Claim 6 (depends on 3) The power converter of claim 3, wherein the pre-charge circuit further comprises a third resistor coupled on a first end to a node between the second capacitor and the load, and on a second end to the circuit ground. ### Claim 7 (depends on 1) The power converter of claim 1, wherein: the second capacitor, the resonant inductor and the first capacitor are coupled in series on a first end to a node between the first and second switching elements and on a second end to a circuit ground, the load is coupled in parallel with the first capacitor, and the pre-charge circuit comprises a first resistor coupled between a positive rail of the DC power source and the node between the first and second switching elements, and a second resistor coupled between the circuit ground and the node between the first and second switching elements. ### Claim 8 (depends on 7) The power converter of claim 7, wherein the pre-charge circuit is configured to pre-charge the second capacitor to a steady state charge value of one half a voltage across the positive rail and the circuit ground. ### Claim 9 (depends on 7) The power converter of claim 7, wherein the first and second resistors are provided with equivalent resistance values. ### Claim 10 (depends on 7) The power converter of claim 7, wherein the pre-charge circuit further comprises a third resistor coupled on a first end to a node between the first capacitor and the resonant inductor, and on a second end to the circuit ground. ### Claim 11 (depends on 1) The power converter of claim 1, wherein the power converter comprises an LED driver provided in a light fixture and the load comprises one or more lighting elements. ### Claim 12 A power converter comprising: first and second switching elements coupled in series across a DC power source; a controller configured to generate drive signals to the switching elements, wherein an output from the switching elements corresponds to a frequency of the gate drive signals; a resonant circuit comprising first and second capacitors, a resonant inductor, and output terminals for receiving a load, wherein: the resonant inductor and the first capacitor are coupled in series on a first end to a node between the first and second switching elements and on a second end to a circuit ground, the second capacitor and the load are coupled in series on a first end to a node between the resonant inductor and the first capacitor; and a pre-charge circuit comprising: a first resistor coupled between a positive rail of the DC power source and the node between the resonant inductor and the first capacitor, and a second resistor coupled between the circuit ground and the node between the resonant inductor and the first capacitor, wherein the pre-charge circuit is configured, after initially receiving power from the DC power source and prior to startup of the controller, to pre-charge at least one of the first and second capacitors in the resonant circuit. ### Claim 13 (depends on 12) The power converter of claim 12, wherein the pre-charge circuit is configured to pre-charge the second capacitor to a steady state charge value of one half a voltage across the positive rail and the circuit ground. ### Claim 14 (depends on 12) The power converter of claim 12, wherein the first and second resistors are provided with equivalent resistance values. ### Claim 15 (depends on 12) The power converter of claim 12, wherein the pre-charge circuit further comprises a third resistor coupled on a first end to a node between the second capacitor and the load, and on a second end to the circuit ground. ### Claim 16 (depends on 12) The power converter of claim 12, wherein the power converter comprises an LED driver provided in a light fixture and the load comprises one or more lighting elements. ### Claim 17 A power converter comprising: first and second switching elements coupled in series across a DC power source; a controller configured to generate drive signals to the switching elements, wherein an output from the switching elements corresponds to a frequency of the gate drive signals; a resonant circuit comprising first and second capacitors, a resonant inductor, and output terminals for receiving a load, wherein: the second capacitor, the resonant inductor and the first capacitor are coupled in series on a first end to a node between the first and second switching elements and on a second end to a circuit ground, and the load is coupled in parallel with the first capacitor; and a pre-charge circuit comprising: a first resistor coupled between a positive rail of the DC power source and the node between the first and second switching elements, and a second resistor coupled between the circuit ground and the node between the first and second switching elements, wherein the pre-charge circuit is configured, after initially receiving power from the DC power source and prior to startup of the controller, to pre-charge at least one of the first and second capacitors in the resonant circuit. ### Claim 18 (depends on 17) The power converter of claim 17, wherein the pre-charge circuit is configured to pre-charge the second capacitor to a steady state charge value of one half a voltage across the positive rail and the circuit ground. ### Claim 19 (depends on 17) The power converter of claim 17, wherein the first and second resistors are provided with equivalent resistance values. ### Claim 20 (depends on 17) The power converter of claim 17, wherein the pre-charge circuit further comprises a third resistor coupled on a first end to a node between the first capacitor and the resonant inductor, and on a second end to the circuit ground.