FREQUENCY BASED FAULT DETECTION

• US 20120194201A1
• Filed: 01/28/2011
• Published: 08/02/2012
• Est. Priority Date: 01/28/2011
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Rtx Corporation)
• Original Assignee: Hamilton Sundstrand Corporation (Rtx Corporation)
• Inventors: Saloio, James
• Granted Patent: US 8,872,522 B2
• Time in Patent Office: Days
• US Class Current: 324/537
• CPC Class Codes: G01R 27/26 Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H02H 1/003 Fault detection by injection of an auxiliary voltage same for detection of earth fault currents H02H3/17; for monitoring earth connection H02H5/105
• CPC Class Codes: H02H 9/042 comprising means to limit the absorbed power or indicate damaged over-voltage protection device

Abstract

A electrical circuit includes an excitation voltage connected via a first circuit path to an output, a switching device having a control terminal and first and second controlled terminals connected to the first circuit path, and a controller that generates a control signal provided to the control terminal of the switching device to selectively supply the excitation voltage to the output. Faults in the electrical circuit are detected by monitoring the switching device voltage at one of the controlled terminals of the switching device.

Claims

1. An electrical circuit with fault detection, the electrical circuit comprising:

an excitation voltage connected via a first circuit path to an output;

a switching device having a control terminal and first and second controlled terminals, the controlled terminals connected in the first circuit path, wherein a control signal provided to the control terminal selectively controls supply of the excitation voltage to the output;

a controller for providing the control signal to the control terminal of the switching device at a first frequency;

a comparator connected to monitor a switch voltage at a first controlled terminal of the switching device and generate a feedback signal based on a comparison of the monitored switch voltage to a threshold voltage; and

wherein the controller monitors a second frequency associated with the feedback signal and detects a fault condition based on a comparison of the first frequency to the second frequency.

2. The electrical circuit of claim 1, wherein the controller compares the first frequency to the second frequency by counting a number of rising edges of the feedback signal within a single cycle of the control signal and detects a fault condition if the number of rising edges is greater than a threshold value.

3. The electrical circuit of claim 2, wherein the controller includes a pulse counter that is incremented with each rising edge of the feedback signal, wherein a pulse counter value is stored when an end of the single cycle of the control signal is detected.

4. The electrical circuit of claim 2, wherein the controller includes a pulse counter that is incremented with each falling edge of the feedback signal, wherein a pulse counter value is stored when an end of the single cycle of the control signal is detected.

5. The electrical circuit of claim 1, wherein the electrical circuit is a driver circuit for an inductive-capacitive (LC) circuit, wherein a capacitive open-circuit fault condition is detected when the monitored second frequency is greater than the first frequency.

6. The electrical circuit of claim 1, wherein the electrical circuit is an amplifier circuit having at least one inductive component and at least one capacitive component, wherein a capacitive open-circuit fault condition is detected when the monitored second frequency is greater than the first frequency.

7. A method of detecting open-circuit capacitance faults in an electrical circuit that includes an excitation voltage connected to an output via a first conductive path and at least one switching device, having a control terminal and first and second controlled terminals connected in the first conductive path, a controller connected to provide a control signal to the control terminal of the switching device to selectively control supply of the excitation voltage to the output, the method comprising:

monitoring a switching device voltage at a first controlled terminal of the switching device;

comparing the switching device voltage to a threshold voltage to generate a feedback signal that indicates whether the switching device voltage is greater than or less than the threshold voltage;

monitoring a frequency response of the feedback signal and comparing the frequency response of the feedback signal to the frequency of the control signal provided to the switching device; and

detecting an open-circuit capacitive fault when the monitored frequency of the feedback signal is greater than the frequency of the control signal.

8. The method of claim 7, wherein monitoring the frequency response of the feedback signal includes maintaining a count of a number of cycles detected in the feedback signal within a single cycle of the control signal.

9. The method of claim 8, wherein detecting an open-circuit capacitive fault includes comparing the count of the number of cycles detected in the feedback signal to a threshold value and indicating a fault condition if the count is higher than the threshold value.

10. An electrical circuit with fault detection, the electrical circuit comprising:

an excitation voltage connected via a first circuit path to an output;

a switching device having a control terminal and first and second controlled terminals, the controlled terminals connected in the first circuit path, wherein a control signal provided to the control terminal selectively controls supply of the excitation voltage to the output;

a controller for providing a control signal to the control terminal of the switching device to control the supply of power from the excitation voltage to the output;

a comparator connected to monitor a switch voltage at a first controlled terminal of the switching device and generate a feedback signal based on a comparison of the monitored switch voltage to a threshold voltage;

a transient voltage suppression (TVS) device connected in parallel with the first circuit path to shunt excess voltage from the first circuit path in response to a transient overvoltage condition; and

wherein the controller determines operability of the TVS device based on a measured duration between a first rising edge and a first falling edge of the feedback signal following a transient overvoltage condition in response to the switching device being turned Off.

11. The electrical circuit of claim 10, wherein the controller determines that the TVS device is not operating properly if the measured duration is less than an expected value.

12. A method of monitoring health of a transient voltage suppression (TVS) device employing in an electrical circuit that includes an excitation voltage connected to an output via a first conductive path and at least one switching device, having a control terminal and first and second controlled terminals connected in the first conductive path, a controller connected to provide a control signal to the control terminal of the switching device to selectively control supply of the excitation voltage to the output, the TVS device connected in parallel to the first conductive path, the method comprising:

monitoring a switching device voltage at a first controlled terminal of the switching device;

comparing the switching device voltage to a threshold voltage to generate a feedback signal that indicated whether the switching device voltage is greater than or less than the threshold voltage;

measuring a time value between a first rising edge of the feedback signal and a first falling edge of the feedback signal following a transient overvoltage in response to the switching device being turned Off; and

detecting a fault in the TVS device based on the measured time value.

13. The method of claim 12, wherein detecting a fault in the TVS device based on the measured time value includes:

comparing the measured time value to an expected time value; and

detecting a fault in the TVS device when the measured time value is less than the expected time value.

14. An electrical circuit with fault detection, the electrical circuit comprising:

an excitation voltage connected via a first circuit path to an output for connection to an inductive-capacitive (L-C) load;

a switching device having a control terminal and first and second controlled terminals, the controlled terminals connected in the first circuit path, wherein a control signal provided to the control terminal selectively controls supply of the excitation voltage to the output;

a controller for providing a control signal to the control terminal of the switching device to control the supply of power from the excitation voltage to the output;

a comparator connected to monitor a switch voltage at a first controlled terminal of the switching device and generate a feedback signal based on a comparison of the monitored switch voltage to a threshold voltage; and

wherein the controller calculates a frequency associated with oscillations in the monitored feedback signal following the switching device being turned Off to detect fault conditions in the L-C load.

15. The electrical circuit of claim 14, wherein the controller compares the calculated frequency to an expected frequency to detect the fault condition in the L-C load.

16. The electrical circuit of claim 14, wherein the controller calculates based on the calculated frequency an inductance values associated with the L-C load and compares the calculated inductance value to an expected inductance value.

17. The electrical circuit of claim 14, wherein the controller detects a short-circuit inductor fault if no oscillations are observed in the monitored feedback signal after the switching device is turned Off.

18. The electrical circuit of claim 14, wherein the controller excludes a first oscillation in the monitored feedback signal in calculating the frequency associated with the oscillations.

19. A method of detecting faults in an inductive-capacitive (L-C) load circuit driven by a driver circuit that includes an excitation voltage connected to the LC load via a first conductive path and at least one switching device, having a control terminal and first and second controlled terminals connected in the first conductive path, a controller connected to provide a control signal to the control terminal of the switching device to selectively control supply of the excitation voltage to the L-C load circuit, the method comprising:

monitoring a switching device voltage at a first controlled terminal of the switching device;

comparing the switching device voltage to a threshold voltage to generate a feedback signal that indicates whether the switching device voltage is greater than or less than the threshold voltage;

calculating a frequency associated with monitored oscillations in the feedback signal following turn-off of the switching device; and

detecting a fault in the L-C load based on the calculated frequency of the oscillations in the feedback signal.

20. The method of claim 19, wherein the calculated frequency is compared to an expected value to detect changes in inductance of the L-C load.

21. The method of claim 19, further including:

detecting a short-circuit fault in the L-C load if no oscillations are detected following turn-off of the switching device.