Supervisory integrated circuit for anti-lock brake system units

• US 5,945,743 A
• Filed: 04/02/1997
• Issued: 08/31/1999
• Est. Priority Date: 04/02/1997
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Truck Brake Systems Company
• Original Assignee: Alliedsignal Truck Brake Systems Company
• Inventors: Squires, Ronald E., Greenly, Cheryl L., Pattantyus, Tamas I.
• Primary Examiner(s): Elms, Richard T.
• Application Number:
  US08/825,875
• Time in Patent Office: 881 Days
• Field of Search: 307/9.1, 307/10.1, 303/138, 303/139, 361/238, 701/45, 701/36, 701/71, 701/76, 701/83, 701/72-75
• US Class Current: 307/10.1
• CPC Class Codes: B60T 8/1708 for lorries or tractor-trailer combinations

Abstract

A supervisory circuit for an anti-lock brake system (ABS) unit. The circuit includes an independent internal voltage reference source that provides power to the circuit components. The circuit also includes an external power source monitor powered by the internal voltage reference source which inhibits the ABS unit when an external power source voltage exceeds a predetermined level. The circuit also includes a system voltage monitor powered by the internal voltage reference source that inhibits the ABS unit when a system voltage deviates from predetermined system voltage parameters. The circuit also includes an electronic control unit (ECU) monitor powered by the internal voltage reference source that monitors a periodic signal generated by an ECU and that inhibits the ABS unit if an ECU timing signal deviates from a predetermined threshold level. The supervisory circuit helps to prevent spurious operation of ABS modulators due to race conditions.

Claims

1. A supervisory circuit for an anti-lock brake system (ABS) unit including an electronic control unit (ECU) and an external power source, comprising:

a power source monitor that inhibits the ABS unit when an external power source voltage deviates from a first predetermined window;

an electronic control unit (ECU) monitor that monitors a periodic signal generated by the ECU and that inhibits the ABS unit if said periodic signal deviates from a second predetermined window; and

a system supply voltage monitor that inhibits the ABS unit when an ECU supply voltage deviates from a third predetermined window.

2. The circuit of claim 1, further comprising an independent internal voltage reference source having a shunt regulator that provides power to said power source monitor, said ECU monitor and said system supply voltage monitor when said external power source is within a predetermined system battery voltage range.

3. The circuit of claim 2, further comprising a plurality of voltage reference lines that supply power from said independent internal voltage reference source to internal circuit components.

4. The circuit of claim 2, further comprising a plurality of clamping signal lines coupled to said independent internal voltage reference source, said external power source monitor, said system supply voltage monitor and said ECU monitor that inhibits energization of ABS unit solenoids upon sensed circuit inhibit conditions by said voltage reference source or one of said monitors.

5. The circuit of claim 2, wherein said independent internal voltage reference source comprises a band-gap voltage reference source.

6. The circuit of claim 1, wherein said external power source monitor comprises a first comparator.

7. The circuit of claim 6, wherein said first comparator is referenced to a voltage of approximately 1.5 V.

8. The circuit of claim 6, wherein said first comparator further protects said ECU from load dump pulses in response to said external power source voltage deviating from said first predetermined window.

9. The circuit of claim 6, wherein said first comparator is activated to inhibit the ABS unit when said external power source generates a voltage which exceeds a predetermined value.

10. The circuit of claim 1, wherein said system supply voltage monitor comprises a window comparator that compares an ABS unit voltage level to a predetermined voltage window and inhibits the ABS unit if the ABS unit voltage level deviates from a predetermined voltage range.

11. The circuit of claim 1, wherein said ECU monitor comprises:

an exclusive OR-gate (EXOR) that generates a watch-dog signal in response to a duty cycle signal generated by the ECU; and

a window comparator that monitors the timing of the watch-dog signal and inhibits the ABS unit if the watch-dog signal deviates from said second predetermined window.

12. The circuit of claim 11, further comprising:

a second comparator coupled to said window comparator that detects watch-dog signal peaks;

a flip-flop coupled to an output of said second comparator and to an output of said EXOR gate;

a current mirror that is selectively switched between a plurality of charging capacitors and ground;

said flip-flop being set by positive leading edges of said watch-dog signal peaks, thereby transmitting current flow from said current mirror into said plurality of charging capacitors.

13. The circuit of claim 12, wherein the positive leading edges terminate current flowing from said current mirror into said plurality of charging capacitors and switch the coupling of said current mirror from said plurality of charging capacitors to ground.

14. The circuit of claim 1, wherein said ECU monitor further comprises a window comparator and a master-slave flip-flop set, operatively coupled to said window comparator, said window comparator generating a signal that initializes an inhibit state of the ABS unit, said inhibit state being stored in said master-slave flip-flop set until two subsequent non-inhibit pulses are generated by said ECU monitor.

15. An anti-lock brake system (ABS) control system, comprising:

an electronic control unit (ECU) including an ECU power source that controls system operation and that generates a periodic watch-dog signal;

a system battery that provides power to said ECU power source;

a supervisory circuit comprising;

a supervisory circuit internal voltage reference source that provides power to said circuit independent of said system battery;

a first voltage detector that inhibits system operation when said system battery deviates from first predetermined operating levels;

a second voltage detector that inhibits system operation when said ECU power source deviates from second predetermined operating levels; and

a watch-dog timer that monitors said periodic watch-dog signal and that inhibits system operation when said signal deviates from predetermined threshold operating parameters.

16. The ABS control system of claim 15, further comprising a plurality of clamp outputs coupled to said first and second voltage detectors and said watch-dog timer to inhibit system modulators in response to an inhibit signal from said supervisory circuit.

17. The ABS control system of claim 16, further comprising a reset device for controlling orderly power up and power down of said ECU when said ECU power source is less than a preset value, said reset device also causing said clamp outputs to inhibit the system modulators when said reset device is in a reset state.

18. The ABS control system of claim 15, wherein outputs from said first and second voltage detectors, said reset device and said watch-dog timer are input into a current sinking transistor whose output inhibits operation of said system.

19. The ABS control system of claim 15, wherein said watch-dog timer generates a saw-tooth waveform in response to the watch-dog signal such that positive peaks of the saw-tooth waveform coincide with positive leading edges of the watch-dog signal;

said watch-dog timer being operative to compare the positive peaks with preset voltage limits;

said watch-dog timer inhibiting system operation if the positive peaks fall outside of said predetermined threshold operating parameters.

20. The ABS control system of claim 19, wherein said watch-dog timer includes a masterslave flip-flop set that latches with a detected waveform positive peak falling outside said predetermined threshold operating parameters, and that unlatches subsequent to two consecutive waveform positive peaks falling within said predetermined threshold operating parameters.

21. The ABS control system of claim 20, further comprising a watch-dog pulse input including an exclusive OR-gate coupled to said master-slave flip-flop set that receives the watch-dog signal and that controls generation of the saw-tooth waveform.

22. An anti-lock brake system (ABS) supervisory circuit, comprising:

a power supply;

voltage monitoring means powered by said power supply that monitors at least one system voltage level and that inhibits system operation when the system voltage level deviates from a preset voltage window; and

a watch-dog timer circuit powered by said power supply that monitors a system timing signal and that inhibits system operation if the timing signal deviates from a preset timing signal level.

23. The ABS supervisory circuit of claim 22, wherein said power supply comprises an independent internal voltage reference source that provides power to circuit components independently from said external power supply.

24. The ABS supervisory circuit of claim 22, wherein said voltage monitoring means comprises:

an electronic control unit (ECU) voltage monitor that inhibits system operation when an ECU supply voltage deviates from a preset ECU voltage window; and

a system battery voltage monitor that inhibits system operation when a system battery voltage level deviates from a preset system battery voltage window.

25. An anti-lock brake system (ABS) supervisory circuit, comprising:

an internal voltage reference source, powered by an external system power supply having a system voltage, that generates an internal reference voltage that is independent from the voltage of said external system power supply; and

voltage monitoring means powered by said independent internal voltage reference source that monitors the system voltage level and that inhibits the system operation when the system voltage level deviates from a preset voltage window.

26. The supervisory circuit of claim 25, wherein said voltage monitoring means comprises:

an electronic control unit (ECU) voltage monitor that inhibits system operation when an ECU supply voltage deviates from a preset ECU voltage window; and

a system battery voltage monitor that inhibits system operation when a system battery voltage level deviates from a preset system battery voltage window.

27. The supervisory circuit of claim 25, further comprising a watch-dog timer circuit powered by said independent internal voltage reference source that monitors a system timing signal and that inhibits system operation if the timing signal deviates from a preset timing signal level.

28. The supervisory circuit of claim 25 wherein said voltage monitoring means includes a hysteresis functionality that prevents reactivation of system operation once the system voltage has been inhibited, until the system voltage both no longer deviates from the preset voltage window and is clear of the endpoint of the preset voltage window by a predetermined amount.

29. A supervisory circuit for an anti-lock brake system (ABS) unit, comprising:

an external power supply;

an independent internal voltage reference source that provides power to circuit components independently from said external power supply; and

a watch-dog timer circuit powered by said independent internal voltage reference source that monitors a system timing signal and that inhibits system operation if the timing signal deviates from a preset timing signal level.

30. The supervisory circuit of claim 29, further comprising:

an electronic control unit (ECU) voltage monitor that inhibits system operation when an ECU supply voltage deviates from a preset ECU voltage window; and

a system battery voltage monitor that inhibits system operation when a system battery voltage level deviates from a preset system battery voltage window.