Fault detection for a pulse width modulation driver

• US 6,317,458 B1
• Filed: 12/21/1998
• Issued: 11/13/2001
• Est. Priority Date: 12/21/1998
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Gottshall, Paul C., Boggs, Brian L., Hart, Steven O., McGee, Brian G.
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Nguyen, Dung X.
• Application Number:
  US09/217,022
• Time in Patent Office: 1,058 Days
• Field of Search: 375/278, 375/238, 375/277, 323/286, 323/276, 363/41, 363/39
• US Class Current: 375/238
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/1555 for the generation of a regulated current to a load whose impedance is substantially inductive
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A driver for producing a desired pulse width modulated current through a load has a driver control for storing diagnostics codes in a diagnostic register responsive to detection of at least one electrical fault condition in a circuit including the load. A short circuit detection signal is generated in response a sensed current exceeding a programmed load current range for the driver, whereupon the driver control disables the load current and generates an interrupt signal to a microprocessor. Open circuits and shorts across the load are distinguished by way of a minimum current signal representative of a sensed current flowing through the load exceeding a predetermined minimum.

Claims

1. A driver for producing a desired pulse width modulated current through a load, comprising:

a target generator for supplying a target current value;

at least one feedback sensor for providing at least one signal representative of a sensed current flowing through the load;

a comparator for comparing said at least one sensed current signal to said target current value;

a driver control for selectively generating trigger signals to switch current through the load in response to the result of said comparison; and

a diagnostic register for storing diagnostic codes, wherein said driver control stores said diagnostics codes in said register responsive to detection of at least one electrical fault condition in a circuit including the load.

2. The driver of claim 1, further comprising:

a feedback block for scaling said at least one sensed current signal by a programmable gain multiplier; and

an element for comparing said scaled signal to a reference voltage and generating a short circuit detection signal when said signal representative of a sensed current flowing through the load exceeds a percentage of a full scale value for a load current range corresponding to said programmable gain multiplier.

3. The driver of claim 1, wherein said sensed current signal is provided by a current sense resistor having a predetermined voltage to current feedback ratio representative of the current through the load, said feedback block enabling programmable selection of the load current range over which said comparator and driver control are operable.

4. The driver of claim 1, further comprising:

means for generating a short circuit detection signal responsive to said at least one signal representative of a sensed current exceeding a programmed load current range for the driver.

5. The driver of claim 4, further comprising at least one switch selectively connecting the load to one of a D.C. source and ground, wherein in response to said short circuit detection signal, said driver control disables said at least one switch and generates an interrupt signal to a microprocessor.

6. The driver of claim 4, further comprising:

a first switch selectively connecting the high side of the load to a D.C. source;

a second switch selectively connecting the low side of the load to ground;

a second feedback sensor for providing at a second signal representative of a sensed current flowing through the load;

wherein said first and second feedback sensors are electrically connected with opposing sides of said load.

7. The driver of claim 4, wherein in response to said short circuit detection signal, said driver control disables said first and second switches and stores a short circuit diagnostic code in said diagnostic register, said code providing a distinction between high side short to ground and low side short to the D.C. source.

8. The driver of claim 1, further comprising:

means for generating a minimum current signal when said at least one signal representative of a sensed current flowing through the load exceeds a predetermined minimum.

9. The driver of claim 8, wherein when said driver control determines said at least one signal representative of a sensed current has not reached a said target current value within a given interval, and said minimum current signal is not generated, said drive control responsively stores an open circuit diagnostic code.

14. The method of claim 4, further comprising, disabling said first and second switches and storing a short circuit diagnostic code in said diagnostic register in response to said short circuit detection signal, said code providing a distinction between high side short to ground and low side short to battery.

10. A method of diagnosing load circuit electrical faults in a driver for producing a desired pulse width modulated current through the load, the method comprising the steps of:

supplying a target current value;

providing at least one signal representative of a sensed current flowing through the load;

comparing said at least one sensed current signal to said target current value;

selectively generating trigger signals to switch current through the load in response to the result of said comparison; and

storing diagnostic codes responsive to detection of at least on electrical fault condition in a circuit including the load.

11. The method of claim 10, further comprising:

scaling said at least one sensed current signal by a programmable gain multiplier;

comparing said scaled signal to a reference voltage; and

generating a short circuit detection signal when said signal representative of a sensed current flowing through the load exceeds a percentage of a full scale value for a load current range corresponding to said programmable gain multiplier.

12. The method of claim 10, further comprising:

generating a short circuit detection signal responsive to said at least one signal representative of a sensed current exceeding a programmed load current range for the driver.

13. The method of claim 12, further comprising:

selectively connecting the load to one of a battery and ground using at least one switch; and

in response to said short circuit detection signal, disabling said at least one switch and generating an interrupt signal to a microprocessor.

15. The method of claim 10, further comprising:

generating a minimum current signal when said at least one signal representative of a sensed current flowing through the load exceeds a minimal current value.

16. The method of claim 15, further comprising, when said at least one signal representative of a sensed current has not reached a said target current value within a given interval and said minimum current signal is not generated, storing an open circuit diagnostic code.

17. The method of claim 15, further comprising setting a load short diagnostic code when is the signal representative of a sensed current flowing through the load falls below said minimal current a given number of times in a row after said trigger signals are turned off.