# US 9,434,407 B2 · Wake-up circuit in an electric steering system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,434,407 B2 - Document ID: US9434407B2 - Status: Granted - Kind: B2 - Application number: 14/455,982 - Filed: 2014-08-11 - Published: 2014-11-27 - Granted: 2016-09-06 - Earliest claimed: 2010-05-14 - Assignees: Steering Solutions IP Holding Corporation - Applicants: Steering Solutions IP Holding Corporation - Inventors: Ishtiaque Amin; Philip G. Bright; Paul M. Fisher - Web page: https://patentgrep.com/patent/US9434407B2 ## CPC - B62D 5/0481: {monitoring the steering system, e.g. failures} - B62D 15/021: {Determination of steering angle} - B62D 15/0235: {by measuring or deriving directly at the electric power steering motor} - H02P 6/182: using back-emf in windings - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract In one aspect, a wake-up circuit is provided for triggering a determination of an absolute rotational position of a rotatable shaft of a motor in an electric power steering system of a vehicle. The wake-up circuit includes a plurality of inputs coupled to separate phases of the motor. A voltage boosting circuit is operable to increase a back electromotive force (EMF) voltage induced on one or more of the inputs by rotation of the rotatable shaft of the motor and produce at least one voltage-boosted back EMF voltage. A comparator circuit is operable to compare the at least one voltage-boosted back EMF voltage to a reference voltage and trigger a monitoring system to perform the determination of the absolute rotational position of the rotatable shaft of the motor in the electric power steering system based on a result of the compare during an ignition off state of the vehicle. ## Claims ### Claim 1 A wake-up circuit for triggering a determination of an absolute rotational position of a rotatable shaft of a motor in an electric power steering system of a vehicle, the wake-up circuit comprising: a plurality of inputs coupled to separate phases of the motor; a voltage boosting circuit operable to increase a back electromotive force (EMF) voltage induced on one or more of the inputs by rotation of the rotatable shaft of the motor and produce at least one voltage-boosted back EMF voltage, the voltage boosting circuit comprising at least one capacitor in-line with each of the inputs and a blocking diode positioned between pairs of the inputs to prevent the at least one capacitor in-line with each of the inputs from discharging into the phases of the motor; and a comparator circuit operable to compare the at least one voltage-boosted back EMF voltage to a reference voltage and trigger a monitoring system to perform the determination of the absolute rotational position of the rotatable shaft of the motor in the electric power steering system of the vehicle based on a result of the compare during an ignition off state of the vehicle. ### Claim 2 (depends on 1) The wake-up circuit of claim 1, wherein the voltage boosting circuit charges the at least one capacitor on a first cycle polarity of each of the inputs and effectively doubles the back EMF voltage on a second cycle polarity opposite the first cycle polarity to produce the at least one voltage-boosted back EMF voltage. ### Claim 3 (depends on 1) The wake-up circuit of claim 1, further comprising a full-wave rectifier circuit, wherein the at least one capacitor on each of the inputs of the voltage boosting circuit is positioned between a diode pair of the full-wave rectifier circuit for each of the inputs. ### Claim 4 (depends on 3) The wake-up circuit of claim 3, wherein a first diode of the diode pair establishes a ground reference for one of the phases of the motor, and a second diode of the diode pair establishes an instantaneous forward voltage for the comparator circuit. ### Claim 5 A wake-up circuit for triggering a determination of an absolute rotational position of a rotatable shaft of a motor in an electric power steering system of a vehicle, the wake-up circuit comprising: a plurality of inputs coupled to separate phases of the motor; a voltage boosting circuit operable to increase a back electromotive force (EMF) voltage induced on one or more of the inputs by rotation of the rotatable shaft of the motor and produce at least one voltage-boosted back EMF voltage; a scaling and protection circuit comprising a voltage divider circuit and a voltage clamp; and a comparator circuit operable to compare the at least one voltage-boosted back EMF voltage to a reference voltage and trigger a monitoring system to perform the determination of the absolute rotational position of the rotatable shaft of the motor in the electric power steering system of the vehicle based on a result of the compare during an ignition off state of the vehicle. ### Claim 6 (depends on 5) The wake-up circuit of claim 5, wherein the scaling and protection circuit further comprises at least one current limiting resistor positioned between the voltage divider circuit and the voltage clamp, and a comparator input voltage indicative of the at least one voltage-boosted back EMF voltage is established between the at least one current limiting resistor and the voltage clamp. ### Claim 7 A system for determining an absolute rotational position of a rotatable shaft of a motor in an electric power steering system of a vehicle, the system comprising: a wake-up circuit comprising a voltage boosting circuit and a comparator circuit, the voltage boosting circuit operable to increase a back electromotive force (EMF) voltage induced on one or more inputs by rotation of the rotatable shaft of the motor and produce at least one voltage-boosted back EMF voltage, the voltage boosting circuit comprises at least one capacitor in-line with each of the inputs and positioned between a diode pair of a full-wave rectifier circuit for each of the inputs, the comparator circuit operable to compare the at least one voltage-boosted back EMF voltage to a reference voltage and output a control signal based on a result of the compare during an ignition off state of the vehicle; and a monitoring system comprising a microprocessor and first and second position sensors operable to generate signals indicative of a relative rotational position of the rotatable shaft, the microprocessor configured to activate in response to the control signal and determine a current absolute position value indicating a current absolute rotational position of the rotatable shaft based on a previously stored absolute position value and an amount of relative rotation of the rotatable shaft based on the signals from the first and second position sensors. ### Claim 8 (depends on 7) The system of claim 7, wherein the voltage boosting circuit charges the at least one capacitor on a first cycle polarity of each of the inputs and effectively doubles the back EMF voltage on a second cycle polarity opposite the first cycle polarity to produce the at least one voltage-boosted back EMF voltage. ### Claim 9 (depends on 7) The system of claim 7, wherein a first diode of the diode pair establishes a ground reference for one phase of the motor, and a second diode of the diode pair establishes an instantaneous forward voltage for the comparator circuit. ### Claim 10 (depends on 7) The system of claim 7, wherein the wake-up circuit further comprises a blocking diode positioned between pairs of the inputs to prevent the at least one capacitor in-line with each of the inputs from discharging into phases of the motor. ### Claim 11 (depends on 7) The system of claim 7, wherein the wake-up circuit further comprises a scaling and protection circuit comprising a voltage divider circuit and a voltage clamp. ### Claim 12 (depends on 11) The system of claim 11, wherein the scaling and protection circuit further comprises at least one current limiting resistor positioned between the voltage divider circuit and the voltage clamp, and a comparator input voltage indicative of the at least one voltage-boosted back EMF voltage is established between the at least one current limiting resistor and the voltage clamp. ### Claim 13 A method for triggering a determination of an absolute rotational position of a rotatable shaft of a motor in an electric power steering system of a vehicle, the method comprising: increasing a back electromotive force (EMF) voltage induced on one or more inputs from separate phases of the motor by rotation of the rotatable shaft to produce at least one voltage-boosted back EMF voltage, the increasing performed by a voltage boosting circuit comprising at least one capacitor in-line with each of the inputs that charges the at least one capacitor on a first cycle polarity of each of the inputs and effectively doubling the back EMF voltage on a second cycle polarity opposite the first cycle polarity to produce the at least one voltage-boosted back EMF voltage; comparing the at least one voltage-boosted back EMF voltage to a reference voltage; and triggering a monitoring system to perform the determination of the absolute rotational position of the rotatable shaft of the motor in the electric power steering system of the vehicle based on a result of the comparing during an ignition off state of the vehicle. ### Claim 14 (depends on 13) The method of claim 13, wherein the at least one capacitor on each of the inputs is positioned between a diode pair of a full-wave rectifier circuit for each of the inputs. ### Claim 15 (depends on 13) The method of claim 13, further comprising preventing the at least one capacitor in-line with each of the inputs from discharging into the phases of the motor.