# US 12,184,270 B2 · IGBT/MOSFET desaturation circuity w/ reverse polarity protection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,270 B2 - Document ID: US12184270B2 - Status: Granted - Kind: B2 - Application number: 18/098,049 - Filed: 2023-01-17 - Published: 2024-07-18 - Granted: 2024-12-31 - Earliest claimed: 2023-01-17 - Assignees: Rosemount Aerospace Inc. - Applicants: Rosemount Aerospace Inc. - Inventors: Joseph Orlowske - Web page: https://patentgrep.com/patent/US12184270B2 ## CPC - H03K 17/0822: {in field-effect transistor switches} - H03K 17/0828: {in composite switches} - H03K 17/78: using opto-electronic devices, i.e. light-emitting and photoelectric devices electrically- or optically-coupled - 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) ## Abstract Apparatus and associate methods relate to desaturation protection of a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT). Desaturation protection circuitry provides desaturation protection to the MOSFET or IGBT as well protection of the desaturation protection circuitry, should such circuitry be connected to reverse power. The desaturation protection circuitry determines a desaturation condition based on a control voltage generated by a Zener-diode-resistor network conductively coupled between first and second conduction nodes of the MOSFET or IGBT. The Zener-diode-resistor network is coupled to first and second conduction nodes via a rectifying diode that is configured to protect the desaturation protection circuitry from reverse bias power. Negative feedback limits current through a signal isolation device that is conductively isolated from the output node, which indicates whether the desaturation condition has been determined. ## Claims ### Claim 1 A system for desaturation protection of a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT), the system comprising: first and second input nodes configured to sense a voltage difference across first and second conduction terminals of the MOSFET or the IGBT connected thereto; an output node configured to indicate whether the voltage difference exceeds a desaturation condition; a Zener-diode-resistor network conductively coupled, via a rectifying diode configured to block reverse-polarity current conduction through the Zener-diode-resistor network, between the first and the second input nodes and comprising a pull-up network connected to a pull-down network at a first control node, wherein, the Zener-diode-resistor network is configured to generate a first control voltage at the first control node based on the voltage difference; a signal isolation device having a device-input current path and a device-output current path conductively isolated from one another, the signal isolation device configured to generate an output signal, via the device-output current path, at the output node in response to current conduction through the device-input current path; a first switch having a first-switch input control terminal coupled to the first control node and a first-switch output conduction path coupled to both the device-input current path and a control network, wherein the first switch is configured to turn on in response to the first control voltage exceeding a first-switch threshold voltage, thereby conducting current through the device-input current path and generating a second control voltage in the control network; and a second switch having a second-switch input control terminal coupled to the control network and a second-switch output conduction path conductively coupled to the pull-up network, wherein the second switch is configured to conduct current through the pull-up network in response to the second control voltage exceeding a second-switch threshold voltage, thereby causing negative feedback control of the current conducted through the device-input current path. ### Claim 2 (depends on 1) The system of claim 1, further comprising the IGBT having first and second conduction nodes conductively coupled to the first and the second input nodes, respectively. ### Claim 3 (depends on 1) The system of claim 1, further comprising the MOSFET having first and second conduction nodes conductively coupled to the first and the second input nodes, respectively. ### Claim 4 (depends on 1) The system of claim 1, further comprising a control circuit having an input port conductively coupled to the output node and having an output port conductively coupled to a control terminal of the IGBT or the MOSFET, wherein the control circuit is configured to determine whether the IGBT or the MOSFET is on based, at least in part, upon a system control voltage at the control terminal of the IGBT or the MOSFET. ### Claim 5 (depends on 4) The system of claim 4, wherein the control circuit supplies a signal to a control terminal of the IGBT or the MOSFET in response to the desaturation condition, thereby turning off the IGBT or the MOSFET. ### Claim 6 (depends on 1) The system of claim 1, wherein the pull-up network comprises a Zener diode in series with a resistor, the Zener diode configured to conduct current when a voltage across the Zener diode exceeds a Zener-breakdown condition. ### Claim 7 (depends on 1) The system of claim 1, wherein the pull-down network comprises a resistor. ### Claim 8 (depends on 1) The system of claim 1, wherein the signal isolation device is an opto-isolator. ### Claim 9 (depends on 1) The system of claim 1, wherein the rectifying diode is configured to operate at a voltage of at least 270 volts. ### Claim 10 (depends on 1) The system of claim 1, wherein the rectifying diode is configured to operate at a voltage up to 1200 volts. ### Claim 11 (depends on 1) The system of claim 1, wherein a pull-up resistor of the pull-up network and a pull-down resistor of the pull-down network are selected to create a predetermined ratio such that the first control voltage is based on a product of the predetermined ratio and the voltage difference and a Zener-breakdown voltage of a Zener diode within the pull-up network. ### Claim 12 (depends on 1) The system of claim 1, wherein the control network is one or more resistors. ### Claim 13 (depends on 1) The system of claim 1, wherein the first switch is a metal-oxide-semiconductor field-effect transistor (MOSFET). ### Claim 14 (depends on 1) The system of claim 1, wherein the second switch is a bipolar-junction-transistor (BJT). ### Claim 15 A method for desaturation protection of a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT), the method comprising: sensing a voltage difference via first and second input nodes across first and second conduction terminals of the MOSFET or the IGBT connected thereto; generating a first control voltage at a first control node based on the voltage difference via a Zener-diode-resistor network conductively coupled, via a rectifying diode configured to block reverse-polarity current conduction through the Zener-diode-resistor network, between the first and the second input nodes and comprising a pull-up network connected to a pull-down network at the first control node; turning on a first switch having a first-switch input control terminal coupled to the first control node and a first-switch output conduction path coupled to a control network, in response to the first control voltage exceeding a first-switch threshold voltage, thereby conducting current through the first-switch output conduction path and generating a second control voltage in the control network; generating an output signal via a signal isolation device having a device-input current path, conductively coupled to the first-switch output conduction path, and a device-output current path, conductively isolated from the device-input current path, via the device-output current path, in response to current conduction through the device-input current path; turning on a second switch having a second-switch input control terminal coupled to the control network and a second-switch output conduction path conductively coupled to the pull-up network, in response to the second control voltage exceeding a second-switch threshold voltage such that current conducts through the pull-up network, thereby causing negative feedback control of the current conducted through the first-switch output conduction path; and indicating, by receiving the output signal at an output node conductively coupled to the device-output current path, whether the voltage difference exceeds a desaturation condition. ### Claim 16 (depends on 15) The method of claim 15, further comprising: evaluating, via a control circuit having an input port conductively coupled to the output node and having an output port conductively coupled to a control terminal of the IGBT or the MOSFET, whether the IGBT or the MOSFET is on based, at least in part, upon a system control voltage at the control terminal of the IGBT or the MOSFET. ### Claim 17 (depends on 16) The method of claim 16, wherein the control circuit supplies a signal to the control terminal of the IGBT or the MOSFET in response to the desaturation condition, thereby turning off the IGBT or the MOSFET. ### Claim 18 (depends on 15) The method of claim 15, wherein the pull-up network comprises a Zener diode in series with a resistor, the Zener diode configured to conduct current when a voltage across the Zener diode exceeds a Zener-breakdown condition. ### Claim 19 (depends on 15) The method of claim 15, wherein the pull-down network comprises a resistor. ### Claim 20 (depends on 15) The method of claim 15, wherein the signal isolation device is an opto-isolator.