# US 12,191,845 B2 · Load drive device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,191,845 B2 - Document ID: US12191845B2 - Status: Granted - Kind: B2 - Application number: 17/786,009 - Filed: 2020-12-11 - Published: 2023-01-19 - Granted: 2025-01-07 - Earliest claimed: 2019-12-26 - Assignees: Hitachi Astemo, Ltd. - Applicants: Hitachi Astemo, Ltd. - Inventors: Keishi Komoriyama; Yoichiro Kobayashi - Web page: https://patentgrep.com/patent/US12191845B2 ## CPC - H03F 1/301: {in MOSFET amplifiers (H03F1/303, H03F1/305, H03F1/308 take precedence)} - H03K 17/0822: {in field-effect transistor switches} - H01F 7/18: Circuit arrangements for obtaining desired operating characteristics, e.g. for slow operation, for sequential energisation of windings, for high-speed energisation of windings - H03F 3/211: {using a combination of several amplifiers (H03F3/60 takes precedence)} - H03F 3/345: with field-effect devices (H03F3/347 takes precedence) - H03F 3/45475: {using IC blocks as the active amplifying circuit} - H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)} - H03K 2017/0806: {against excessive temperature} - H03K 2217/0072: Low side switches, i.e. the lower potential [DC] or neutral wire [AC] being directly connected to the switch and not via the load - H03F: AMPLIFIERS - 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) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - 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) ## Abstract Achieved is a load drive device capable of suppressing local concentration of temperature at the time of absorbing a counter electromotive force of an inductive load while suppressing a size of a power transistor. The load drive device includes a first transistor connected between a first control electrode and an inductive load. Further, the load drive device includes an active clamp circuit that becomes conductive when a terminal voltage of a second control electrode between the first transistor and the inductive load exceeds a threshold. Furthermore, the load drive device includes a second transistor connected to the second control electrode and connected in parallel to the first transistor. ## Claims ### Claim 1 A load drive device comprising: a first transistor connected between a first control electrode and an inductive load; an active clamp circuit that becomes conductive when a terminal voltage of a second control electrode between the first transistor and the inductive load exceeds a threshold; a second transistor connected to the second control electrode and connected in parallel to the first transistor; a buffer circuit that is connected to the first transistor via the first control electrode, receives an input of an input signal for driving the inductive load, and drives the first transistor; a resistor connected in series to the second transistor, and a voltage amplifier circuit that compares a voltage of the second control electrode with a predetermined voltage threshold, wherein the voltage amplifier circuit outputs a voltage level obtained by amplifying a differential voltage between the voltage of the second control electrode and the voltage threshold, and conduction of the second transistor is controlled by the amplified voltage level. ### Claim 2 (depends on 1) The load drive device according to claim 1, further comprising a first trigger output circuit that outputs a trigger signal from a time point at which the input signal of the buffer circuit is switched from on to off, wherein conduction of the second transistor is controlled by the trigger signal. ### Claim 3 (depends on 1) The load drive device according to claim 1, further comprising a second trigger output circuit that outputs a trigger signal from a time point at which the active clamp circuit becomes conductive, wherein conduction of the second transistor is controlled by the trigger signal. ### Claim 4 (depends on 1) The load drive device according to claim 1, further comprising a control unit that controls conduction of the inductive load, wherein the control unit outputs a trigger signal according to an inductance value of the inductive load, a resistance value, a battery voltage value, and a clamp voltage value from a time point at which interruption of the inductive load is started, and conduction of the second transistor is controlled by the trigger signal. ### Claim 5 A load drive device comprising: a first transistor connected between a first control electrode and an inductive load; a second transistor connected to the second control electrode and connected in parallel to the first transistor; a second transistor control signal output unit that turns on the second transistor at a timing when the first transistor is turned off; a buffer circuit that is connected to the first transistor via the first control electrode, receives an input of an input signal for driving the inductive load, and drives the first transistor; a resistor connected in series to the second transistor, and the second transistor control signal output unit is a voltage amplifier circuit that compares a voltage of the second control electrode with a predetermined voltage threshold, the voltage amplifier circuit outputs a voltage level obtained by amplifying a differential voltage between the voltage of the second control electrode and the voltage threshold, and conduction of the second transistor is controlled by the amplified voltage level. ### Claim 6 (depends on 5) The load drive device according to claim 5, wherein the second transistor control signal output unit is a first trigger output circuit that outputs a trigger signal from a time point at which the input signal of the buffer circuit is switched from on to off, and conduction of the second transistor is controlled by the trigger signal. ### Claim 7 (depends on 5) The load drive device according to claim 5, further comprising an active clamp circuit that causes a current to flow from the second control electrode to the first control electrode when a terminal voltage of the second control electrode between the first transistor and the inductive load exceeds a threshold, wherein the second transistor control signal output unit is a second trigger output circuit that outputs a trigger signal from a time point at which the active clamp circuit becomes conductive, and conduction of the second transistor is controlled by the trigger signal. ### Claim 8 (depends on 5) The load drive device according to claim 5, wherein the second transistor control signal output unit is a control unit that controls conduction of the inductive load, the control unit outputs a trigger signal according to an inductance value of the inductive load, a resistance value, a battery voltage value, and a clamp voltage value from a time point at which interruption of the inductive load is started, and conduction of the second transistor is controlled by the trigger signal. ### Claim 9 (depends on 5) The load drive device according to claim 5, further comprising an active clamp circuit that causes a current to flow from the second control electrode to the first control electrode when a terminal voltage of the second control electrode between the first transistor and the inductive load exceeds a threshold.