# US 11,444,452 B2 · Current limiting circuits > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,444,452 B2 - Document ID: US11444452B2 - Status: Granted - Kind: B2 - Application number: 17/177,840 - Filed: 2021-02-17 - Published: 2021-06-03 - Granted: 2022-09-13 - Earliest claimed: 2021-02-17 - Assignees: Astec International Limited - Applicants: Astec International Limited - Inventors: Wei Ping Li; Wei Jia Yan; Wen Jian Liao; Xin Zhang - Web page: https://patentgrep.com/patent/US11444452B2 ## CPC - H02H 9/025: {Current limitation using field effect transistors} - H02M 3/158: including plural semiconductor devices as final control devices for a single load - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - 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) ## Abstract A current limiting circuit for controlling current from a power supply to a load having a capacitance includes an inductor, a transistor coupled in a current path with the inductor, and a control circuit. The transistor includes a control terminal. The control circuit is coupled to sense a voltage across the inductor and coupled to the control terminal of the transistor. The control circuit is configured to turn off the transistor when the voltage across the inductor is greater than a threshold to restrict current from a power supply, and turn on the transistor when a defined parameter is met to allow current from the power supply to charge the load capacitance. Other example current limiting circuits are also disclosed. ## Claims ### Claim 1 A method for controlling current from a power supply to a load having a load capacitance, the method comprising: sensing, via a control circuit, a voltage across an inductor coupled in a current path with a transistor, the transistor having a control terminal; controlling, via one or more control switching devices of the control circuit, the transistor into an off state via the control terminal in response to the voltage across the inductor being greater than a threshold to restrict current from a power supply; and controlling, via the one or more control switching devices, the transistor into an on state via the control terminal in response to a defined parameter being met to allow current from the power supply to charge the load capacitance. ### Claim 2 (depends on 1) The method of claim 1, wherein the transistor includes a metal-oxide-semiconductor field-effect transistor (MOSFET). ### Claim 3 (depends on 1) The method of claim 1, wherein the voltage across the inductor falls to zero after the transistor turns off. ### Claim 4 (depends on 1) The method of claim 1 further comprising clamping a voltage across the inductor via a clamping circuit in response to the transistor being off. ### Claim 5 (depends on 4) The method of claim 4, wherein the clamping circuit includes at least one diode. ### Claim 6 (depends on 1) The method of claim 1 further comprising adjusting the amount of current from the power supply to charge the load capacitance. ### Claim 7 (depends on 6) The method of claim 6, wherein the transistor includes a MOSFET; and wherein adjusting the amount of current comprises operating the transistor in its saturation mode. ### Claim 8 A current limiting circuit comprising: an input coupleable to a power converter of a power supply for receiving an output voltage from the power converter; an output for supplying current to a load having a capacitance; an inductor; a transistor coupled in a current path with the inductor, the transistor having a control terminal; and a control circuit coupled to the control terminal of the transistor and configured to sense a voltage across the inductor, the control circuit having one or more control switching devices configured to control the transistor including turning off the transistor in response to the voltage across the inductor being greater than a threshold to restrict current from a power supply, and turning on the transistor in response to a defined parameter being met to allow current from the power supply to charge the load capacitance. ### Claim 9 (depends on 8) The current limiting circuit of claim 8 wherein the transistor includes a metal-oxide-semiconductor field-effect transistor (MOSFET). ### Claim 10 (depends on 8) The current limiting circuit of claim 8 wherein the voltage across the inductor falls to zero after the transistor turns off. ### Claim 11 (depends on 8) The current limiting circuit of claim 8 wherein the current limiting circuit does not include a current sense resistor. ### Claim 12 (depends on 8) The current limiting circuit of claim 8 further comprising a clamping circuit configured to clamp a voltage across the inductor when the transistor is off. ### Claim 13 (depends on 12) The current limiting circuit of claim 12 wherein the clamping circuit includes at least one diode. ### Claim 14 (depends on 8) The current limiting circuit of claim 8 wherein the control circuit is configured to adjust the amount of current from the power supply to charge the load capacitance. ### Claim 15 (depends on 14) The current limiting circuit of claim 14 wherein the control circuit includes one or more electrical components configured to adjust the amount of current. ### Claim 16 (depends on 15) The current limiting circuit of claim 15 wherein the transistor includes a MOSFET operating in its saturation mode when the one or more electrical components adjust the amount of current from the power supply to charge the load capacitance. ### Claim 17 (depends on 15) The current limiting circuit of claim 15 wherein the one or more electrical components include at least one capacitor and at least one resistor. ### Claim 18 (depends on 8) The current limiting circuit of claim 8 wherein the transistor is a first transistor and wherein the one or more control switching devices includes a second transistor and a third transistor. ### Claim 19 (depends on 8) The current limiting circuit of claim 8 wherein the threshold is based on the one or more control switching devices. ### Claim 20 (depends on 8) The current limiting circuit of claim 8 wherein the defined parameter includes a defined period of time after the transistor turns off and wherein the control circuit is configured to control the transistor to turn on when the defined period of time has elapsed.