# US 12,224,738 B2 · Switch device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,224,738 B2 - Document ID: US12224738B2 - Status: Granted - Kind: B2 - Application number: 18/532,807 - Filed: 2023-12-07 - Published: 2024-04-04 - Granted: 2025-02-11 - Earliest claimed: 2017-12-15 - Assignees: Rohm Co., Ltd. - Applicants: Rohm Co., Ltd. - Inventors: Toru Takuma - Web page: https://patentgrep.com/patent/US12224738B2 ## CPC - H03K 17/0828: {in composite switches} - B60R 16/03: for supply of electrical power to vehicle subsystems {or for (circuit arrangements for charging batteries H02J7/00)} - G01K 7/01: using semiconducting elements having PN junctions (G01K7/02, G01K7/16, G01K7/30 take precedence) - G01K 7/16: using resistive elements - H02H 3/08: responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04) - H02H 3/087: for DC applications - H02H 3/243: {for DC systems} - H02H 5/04: responsive to abnormal temperature {(specially adapted for electric machines H02H7/0852)} - H02H 5/10: responsive to mechanical injury, e.g. rupture of line, breakage of earth connection - H02H 6/00: Emergency protective circuit arrangements responsive to undesired changes from normal non-electric working conditions using simulators of the apparatus being protected, e.g. using thermal images - H02H 9/025: {Current limitation using field effect transistors} - H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators - H03K 17/0822: {in field-effect transistor switches} - H03K 17/168: {in composite switches} - H03K 2217/0036: Means reducing energy consumption - 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) - B60R: VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) - 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 An example switch device includes a switching element to connect/disconnect a current path from a power supply terminal to a ground terminal via a load, and an overcurrent protection circuit to limit output current flowing in the switching element to be an overcurrent limit value or less. When an output short circuit of the load is detected, the overcurrent protection circuit decreases the overcurrent limit value to be lower as a power supply voltage is higher. The overcurrent protection circuit includes a reference current generation portion that includes: a differential amplifier portion, an upper side current generation portion arranged to generate a predetermined an upper side current, a lower side current generation portion arranged to generate a lower side current, and a difference current generation portion arranged to output a difference current based on the lower side current and the upper side current, as the reference current. ## Claims ### Claim 1 A switch device comprising: a switching element configured to connect/disconnect a current path from a power supply terminal to a ground terminal via a load; an overcurrent protection circuit configured to limit output current flowing in the switching element to be an overcurrent limit value or less; and a duty control unit, wherein when an output short circuit of the load is detected, the overcurrent protection circuit decreases the overcurrent limit value to be smaller as a power supply voltage is higher, wherein the overcurrent protection circuit includes: a reference current generation portion configured to generate a reference current, and a comparison portion configured to compare a threshold value voltage corresponding to the reference current with a sense voltage corresponding to the output current so as to generate a first overcurrent protection signal for controlling a conduction degree of the switching element, and when an output short circuit of the load is detected, the reference current generation portion decreases the reference current to be smaller as the power supply voltage is higher, and wherein the reference current generation portion includes: a differential amplifier portion, an upper side current generation portion configured to generate an upper side current, a lower side current generation portion configured to generate a lower side current, and a difference current generation portion configured to output a difference current based on the lower side current and the upper side current, as the reference current, wherein the duty control unit is configured to turn off the switching element for a predetermined off-period when a current limiting operation by the over current protection circuit continues for a predetermined on-period, wherein the over current protection circuit is configured to generate a status notification signal for notifying the duty control unit that the over current protection circuit currently limits the output current, wherein the duty control unit is configured to receive the status notification signal so as to generate a second overcurrent protection signal for turning off the switching element for the predetermined off-period when the current limiting operation by the over current protection circuit continues for the predetermined on-period. ### Claim 2 (depends on 1) The switch device according to claim 1, wherein the overcurrent protection circuit decreases the overcurrent limit value only when the power supply voltage is higher than a predetermined threshold value voltage. ### Claim 3 (depends on 1) The switch device according to claim 1, wherein the reference current generation portion further includes a lower side current control unit arranged to stop output of the lower side current when at least one of an output short circuit of the load and an overcurrent abnormality of the output current is not detected. ### Claim 4 (depends on 3) The switch device according to claim 3, wherein the lower side current control unit stops output of the lower side current also when an overvoltage abnormality of the power supply voltage is not detected. ### Claim 5 (depends on 1) An electronic apparatus comprising: the switch device according to claim 1, and a load connected to the switch device. ### Claim 6 (depends on 5) The electronic apparatus according to claim 5, wherein the switch device is a high side switch connected between the power supply terminal and the load, or a low side switch connected between the load and the ground terminal. ### Claim 7 (depends on 5) The electronic apparatus according to claim 5, wherein the load is one of a bulb lamp, a relay coil, a solenoid, a light emitting diode, and a motor. ### Claim 8 (depends on 5) A vehicle comprising the electronic apparatus according to claim 5. ### Claim 9 (depends on 1) The switch device according to claim 1, wherein the differential amplifier portion is configured to amplify a difference value between the power supply voltage or its divided voltage and a predetermined reference voltage so as to generate a differential amplified voltage. ### Claim 10 (depends on 9) The switch device according to claim 9, wherein the lower side current corresponds to the differential amplified voltage. ### Claim 11 (depends on 1) The switch device according to claim 1, wherein the difference current is obtained by subtracting the lower side current from the upper side current.