# US 2021/0242864 A1 · Switch circuit capable of overcurrent protection with small and simple circuit, and with simple operation, without affecting normal operation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0242864 A1 - Document ID: US20210242864A1 - Status: Published application - Kind: A1 - Application number: 17/259,512 - Filed: 2019-03-11 - Published: 2021-08-05 - Earliest claimed: 2018-07-26 - Assignees: OMRON Corporation - Applicants: OMRON Corporation - Inventors: Wataru OKADA; Satoshi IWAI; Noriyuki NOSAKA; Takeo NISHIKAWA; Kenji KOBAYASHI; Keiji SHIRAISHI - Web page: https://patentgrep.com/patent/US20210242864A1 ## CPC - H03K 17/08128: {in composite switches} - H03K 17/0822: {in field-effect transistor switches} - H02H 9/02: responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)} - H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators - H02M 3/158: including plural semiconductor devices as final control devices for a single load - H02M 7/5387: in a bridge configuration - H03K 17/166: {Soft switching} - H03K 2217/0027: Measuring means of, e.g. currents through or voltages across the switch - 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) - 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 driver circuit controls a first switch element. A first resistor is connected between the driver circuit and the first switch element. A second switch element is connected to the first switch element. An overcurrent detector circuit controls the second switch element based on an overcurrent current flowing through the first switch element. A second resistor is connected between the overcurrent detector circuit and the second switch element. The first and second resistor is set such that a turn-off time of the first switch element when the second switch element is turned on by the overcurrent detector circuit is longer than a turn-off time of the first switch element when the first switch element is turned off by the driver circuit. ## Claims ### Claim 1 A switch circuit comprising: a first switch element that has a first terminal connected to a first voltage source, a second terminal connected to a second voltage source, and a third terminal; a driver circuit that generates a first control signal for turning the first switch element; a first resistor that is connected between the driver circuit and the third terminal on and off; a second switch element that has a fourth terminal connected to the third terminal, a fifth terminal connected to the second voltage source, and a sixth terminal; an overcurrent detector circuit that generates a second control signal for turning the second switch element on and off, based on whether or not a current flowing through the first switch element exceeds a predetermined threshold; and a second resistor that is connected between the overcurrent detector circuit and the sixth terminal, wherein the first and second resistors have resistances configured such that a turn-off time of the first switch element when the second switch element is turned on by the second control signal is longer than a turn-off time of the first switch element when the first switch element is turned off by the first control signal. ### Claim 2 (depends on 1) The switch circuit as claimed in claim 1, further comprising a capacitor that is connected between the fifth and sixth terminals of the second switch element. ### Claim 3 (depends on 1) The switch circuit as claimed in claim 1, wherein, when turning the second switch element off, the overcurrent detector circuit generates the second control signal having a polarity opposite to a polarity of a potential of the first voltage source, with respect to a potential of the second voltage source. ### Claim 4 (depends on 1) The switch circuit as claimed in claim 1, wherein the first resistor is integrated with the driver circuit. ### Claim 5 (depends on 1) The switch circuit as claimed in claim 1, wherein the second switch element is an NPN transistor or an N-channel MOSFET, and wherein the overcurrent detector circuit sets the second control signal to a high level when the current flowing through the first switch element exceeds the threshold, and sets the second control signal to a low level when the current flowing through the first switch element is equal to or smaller than the threshold. ### Claim 6 (depends on 1) The switch circuit as claimed in claim 1, wherein the second switch element is a PNP transistor or a P-channel MOSFET, and wherein the overcurrent detector circuit sets the second control signal to a low level when the current flowing through the first switch element exceeds the threshold, and sets the second control signal to a high level when the current flowing through the first switch element is equal to or smaller than the threshold. ### Claim 7 A power converter apparatus comprising at least one switch circuit, the at least one switch circuit comprising: a first switch element that has a first terminal connected to a first voltage source, a second terminal connected to a second voltage source, and a third terminal; a driver circuit that generates a first control signal for turning the first switch element; a first resistor that is connected between the driver circuit and the third terminal on and off; a second switch element that has a fourth terminal connected to the third terminal, a fifth terminal connected to the second voltage source, and a sixth terminal; an overcurrent detector circuit that generates a second control signal for turning the second switch element on and off, based on whether or not a current flowing through the first switch element exceeds a predetermined threshold; and a second resistor that is connected between the overcurrent detector circuit and the sixth terminal, wherein the first and second resistors have resistances configured such that a turn-off time of the first switch element when the second switch element is turned on by the second control signal is longer than a turn-off time of the first switch element when the first switch element is turned off by the first control signal.