# US 2013/0154597 A1 · Latching over-current protection circuit and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0154597 A1 - Document ID: US20130154597A1 - Status: Published application - Kind: A1 - Application number: 13/463,417 - Filed: 2012-05-03 - Published: 2013-06-20 - Earliest claimed: 2011-12-19 - Assignees: Tyco Safety Products Canada Ltd. - Inventors: Andrei Bucsa; Stephen D.W. Fosty - Web page: https://patentgrep.com/patent/US20130154597A1 ## CPC - G01R 23/02: Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage - G01R 19/00: Arrangements for measuring currents or voltages or for indicating presence or sign thereof (G01R5/00 takes precedence; for measuring bioelectric currents or voltages A61B5/24) - G06F 17/00: Digital computing or data processing equipment or methods, specially adapted for specific functions (information retrieval, database structures or file system structures therefor G06F16/00) - H02H 3/087: for DC applications - H02J 7/865: {Battery or charger load switching, e.g. concurrent charging and load supply (H02J7/50 takes precedence)} - F16H 59/105: {consisting of electrical switches or sensors} - G01B 7/003: {for measuring position, not involving coordinate determination (coordinate measuring G01B7/004)} - G01B 7/14: for measuring distance or clearance between spaced objects or spaced apertures (G01B7/30 takes precedence) - G01D 5/2457: {Incremental encoders having reference marks} - H02H 3/06: with automatic reconnection - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - 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) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - F16H: GEARING - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR ## Abstract A load limiting circuit includes a transistor switch, for providing current to a load and a latching circuit having a control input, and a latch output driving the transistor switch. A current sensing transistor interconnects with the transistor switch, to sense current in excess of a threshold to the load. The current sensing transistor drives the control input to the latching circuit. An external controller may drive and monitor the control input. The controller may thus turn the transistor switch on and off, and be notified of an over-current condition. The latching circuit may turn the transistor switch off permanently. As well, the controller may attempt to set the load limiting circuit after an over-current condition. ## Claims ### Claim 1 A load limiting circuit comprising: a transistor switch, for providing current to a load; a latching circuit having a control input, and a latch output; a current sensing transistor, interconnected with said transistor switch, to sense current in excess of a threshold to said load; wherein said current sensing transistor drives said control input, and said latch output drives said transistor switch. ### Claim 2 (depends on 1) The load limiting circuit of claim 1, wherein said latching circuit is a complementary latch. ### Claim 3 (depends on 2) The load limiting circuit of claim 2, wherein said complementary latch comprises a BJT pair. ### Claim 4 (depends on 1) The load limiting circuit of claim 1, wherein said latching circuit provides a fault signal, indicative of a current in excess of said threshold to said load. ### Claim 5 (depends on 1) The load limiting circuit of claim 1, wherein said latching circuit comprises an NPN transistor and a PNP transistor. ### Claim 6 (depends on 1) The load limiting circuit of claim 1, further comprising a filter between said current sensing transistor and said transistor switch. ### Claim 7 (depends on 1) The load limiting circuit of claim 1, wherein said transistor switch comprises a BJT. ### Claim 8 (depends on 6) The load limiting circuit of claim 6, wherein said transistor switch, when on, allows current to flow from its collector to emitter. ### Claim 9 (depends on 8) The load limiting circuit of claim 8, wherein said latch output drives a base of said transistor switch. ### Claim 10 (depends on 1) The load limiting circuit of claim 1, further comprising a controller to control operation of said latching circuit through said control input. ### Claim 11 (depends on 10) The load limiting circuit of claim 10, wherein said latching circuit comprises a state output providing a signal indicative of a state of said latch. ### Claim 12 (depends on 11) The load limiting circuit of claim 11, wherein said control input also provides said state output. ### Claim 13 (depends on 12) The load limiting circuit of claim 12, wherein said controller monitors said state output to detect over-current to said load. ### Claim 14 (depends on 10) The load limiting circuit of claim 10, wherein said latching circuit provides a fault signal, indicative of a current in excess of said threshold to said load and wherein said fault signal is interconnected with an interrupt line of said controller. ### Claim 15 (depends on 14) The load limiting circuit of claim 14, further comprising a persistent computer readable medium storing controller executable instructions that cause said controller to set said latching after detecting an over-current condition. ### Claim 16 (depends on 15) The load limiting circuit of claim 15, wherein said controller monitors said fault signal as it keeps said latching circuit on to prevent said latching circuit reverting to an off state. ### Claim 17 A method of limiting current to a load, comprising providing a transistor switch, for providing said current to said load; providing a latching circuit to control a state of said transistor switch; sensing current provided by said transistor switch; latching said latching circuit to turn said transistor switch off, in the presence of said current exceeding a threshold. ### Claim 18 (depends on 17) The method of claim 17, further comprising setting said latching circuit to turn said transistor on, and concurrently monitoring said latching circuit to determine if current in excess of said threshold is provided to said load. ### Claim 19 (depends on 18) The method of claim 18, further comprising latching said latching circuit to turn said transistor off if current in excess of said threshold is provided to said load for a determined interval.