# US 10,770,883 B2 · One-transistor devices for protecting circuits and autocatalytic voltage conversion therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,770,883 B2 - Document ID: US10770883B2 - Status: Granted - Kind: B2 - Application number: 15/755,744 - Filed: 2016-09-21 - Published: 2018-08-30 - Granted: 2020-09-08 - Earliest claimed: 2015-09-21 - Assignees: Sympote Technologies LLC - Applicants: Symptote Technologies LLC - Inventors: Mark D. Creech - Web page: https://patentgrep.com/patent/US10770883B2 ## CPC - H02H 3/085: {making use of a thermal sensor, e.g. thermistor, heated by the excess current (also responsive to the temperature of the protected device H02H5/041, thermal images H02H6/00)} - H02H 3/08: responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04) - H02H 3/087: for DC applications - H02H 9/025: {Current limitation using field effect transistors} - H02M 1/32: Means for protecting converters other than automatic disconnection - H03K 17/04123: {in field-effect transistor switches} - H03K 17/04206: {in field-effect transistor switches} - H03K 17/0822: {in field-effect transistor switches} - H10D 89/811: {using FETs as protective elements} - H10D 89/911: {using passive elements as protective elements} - H03K 2017/6875: {using self-conductive, depletion FETs} - H03K 2217/0027: Measuring means of, e.g. currents through or voltages across the switch - H03K 2217/0081: Power supply means, e.g. to the switch driver - 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) - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract Devices having one primary transistor, or a plurality of primary transistors in parallel, protect electrical circuits from overcurrent conditions. Optionally, the devices have only two terminals and require no auxiliary power to operate. In those devices, the voltage drop across the device provides the electrical energy to power the device. A third or fourth terminal can appear in further devices, allowing additional overcurrent and overvoltage monitoring opportunities. Autocatalytic voltage conversion allows certain devices to rapidly limit or block nascent overcurrents. ## Claims ### Claim 1 A device for protecting a circuit having a primary current path from an overcurrent condition, comprising: a first terminal and a second terminal configured to route the primary current path through the device; a first transistor comprising a first gate, a first drain, and a first source; wherein the first transistor is a depletion mode, normally-on transistor; wherein the first transistor is arranged in series in the primary current path between the first terminal and the second terminal; a driver circuitry; the driver circuitry comprising a voltage converter circuitry adapted to receive an input voltage derived solely from a voltage between the first terminal and the second terminal, and convert the input voltage to a releasably-stored voltage, wherein the driver circuitry is configured to apply the releasably-stored voltage or a derivative voltage thereof as a gate voltage at the first gate relative to the first source, wherein the driver circuitry converts the input voltage to the releasably-stored voltage by multiplying and inverting the input voltage; and wherein the voltage converter circuitry comprises a switched capacitor network; wherein, when a first positive voltage and a normal current condition exist from the first terminal to the second terminal, the first transistor is configured to pass current between the first terminal and the second terminal; and wherein, when a second positive voltage and a severe overcurrent condition exist from the first terminal to the second terminal, the driver circuitry is configured to drive the first transistor into blocking depletion mode by applying the releasably-stored voltage or the derivative voltage thereof as the gate voltage; and wherein the device is configured to pass current during normal current conditions, and to substantially block current during severe overcurrent conditions. ### Claim 2 (depends on 1) The device of claim 1, wherein the voltage converter circuitry is configured to convert the input voltage within 20 μs. ### Claim 3 (depends on 1) The device of claim 1, wherein the voltage converter circuitry is configured to convert the input voltage to the releasably-stored voltage within 100 μs. ### Claim 4 (depends on 1) The device of claim 1, wherein the switched capacitor network is a parallel-to-series switched capacitor network. ### Claim 5 (depends on 1) The device of claim 1, wherein, when a third positive voltage and a slight overcurrent condition exists from the first terminal to the second terminal, the driver circuitry is configured to drive the first transistor into current-limiting mode by applying the releasably-stored voltage or the derivative voltage thereof as the gate voltage; and wherein the device is configured to limit current during slight overcurrent conditions. ### Claim 6 (depends on 1) The device of claim 1, wherein the voltage converter circuitry is configured to convert the input voltage autocatalytically. ### Claim 7 (depends on 1) The device of claim 1, wherein the device is configured to operate without any auxiliary power supply. ### Claim 8 (depends on 1) The device claim 1, wherein the device comprises no terminals other than the first terminal and the second terminal. ### Claim 9 (depends on 1) The device of claim 1, wherein the first transistor is a depletion mode, normally-on SiC transistor. ### Claim 10 (depends on 5) The device of claim 5, further comprising at least one second transistor arranged in parallel electrical communication with the first transistor, wherein each second transistor of the at least one second transistor comprises a second gate, a second drain, and a second source; wherein the at least one second transistor is configured to be driven into blocking depletion mode when the second positive voltage and the severe overcurrent condition exist from the first terminal to the second terminal; and wherein the at least one second transistor is configured to be driven into current limiting mode when the third positive voltage and the slight overcurrent condition exist from the first terminal to the second terminal. ### Claim 11 (depends on 1) The device of claim 1, wherein the driver circuitry further comprises a voltage floating circuitry configured to float the releasably-stored voltage to obtain a floated voltage; wherein the driver circuitry is configured to apply the floated voltage or a derivative of the floated voltage as the gate voltage. ### Claim 12 (depends on 1) The device of claim 1, further comprising a temperature responsive element arranged in series in the primary current path with the first transistor; wherein the temperature responsive element is configured to cause the driver circuitry to drive the first transistor into blocking depletion mode when the severe overcurrent condition exists. ### Claim 13 (depends on 1) The device of claim 1, further comprising a gate protection circuitry configured to reduce a gate voltage at a transistor in the device. ### Claim 14 (depends on 13) The device of claim 13, wherein the gate protection circuitry comprises a gate-protecting transistor in parallel with the first transistor, and a gate resistor in series electrical communication between the gate of the gate-protecting transistor and the second terminal. ### Claim 15 A method for protecting a circuit against an overcurrent condition, comprising: providing a device having a first terminal and a second terminal, and a first transistor comprising a first gate, a first drain, and a first source; wherein the first transistor is a depletion mode, normally-on transistor; wherein the first transistor is arranged in series in a primary current path between the first terminal and the second terminal; wherein the device is configured to receive no auxiliary power; placing the first terminal and the second terminal in series electrical communication in the circuit so that all current flowing in the circuit flows through or is blocked by the device; when a non-zero voltage exists between the first terminal and the second terminal, converting the non-zero voltage to obtain a releasably-stored voltage; floating the releasably-stored voltage to obtain a floated voltage; when an overcurrent condition exists between the first terminal and the second terminal, applying the floated voltage to the first gate to drive the first transistor into blocking depletion mode, thereby blocking substantially all current between the first terminal and the second terminal; thereby protecting the circuit from the overcurrent condition. ### Claim 16 (depends on 15) The method of claim 15, wherein the converting the non-zero voltage to obtain a releasably-stored voltage occurs autocatalytically. ### Claim 17 A method for protecting a circuit against an overcurrent condition, comprising: providing a device having a first terminal and a second terminal, and a first transistor comprising a first gate, a first drain, and a first source; wherein the first transistor is a depletion mode, normally-on transistor; wherein the first transistor is arranged in series in a primary current path between the first terminal and the second terminal; wherein the device is configured to receive no auxiliary power; placing the first terminal and the second terminal in series electrical communication in the circuit so that all current flowing in the circuit flows through or is limited by the device; when a non-zero voltage exists between the first terminal and the second terminal, converting the non-zero voltage to obtain a releasably-stored voltage; floating the releasably-stored voltage to obtain a floated voltage; when an overcurrent condition exists between the first terminal and the second terminal, applying the floated voltage to the first gate to drive the first transistor into current limiting mode, thereby limiting the current between the first terminal and the second terminal; thereby protecting the circuit from the overcurrent condition. ### Claim 18 (depends on 17) The method of claim 17, wherein the converting the non-zero voltage to obtain a releasably-stored voltage occurs autocatalytically.