Fast power-fail detector for power supplies with energy hysteresis

• US 4,713,553 A
• Filed: 10/21/1985
• Issued: 12/15/1987
• Est. Priority Date: 10/21/1985
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Townsend, Greg M., DiPrizio, Giuseppe M.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Shik Luen Paul
• Application Number:
  US06/789,866
• Time in Patent Office: 785 Days
• Field of Search: 307/64, 307/66, 307/83, 307/86, 307/87, 307/310, 324/76 R, 324/78 R, 324/78 D, 324/78 E, 324/77 A, 324/51, 324/52, 361/18, 361/21, 361/33, 361/37, 361/56, 361/59, 361/60, 361/64, 361/65, 361/79, 361/82, 361/86, 361/87, 361/88, 361/90, 361/91, 361/92, 361/93, 361/106, 361/125, 361/54, 361/63, 361/67, 361/89 , 361/109, 328/146, 328/149, 328/150
• US Class Current: 307/64
• CPC Class Codes: G01R 19/16552 in I.C. power supplies

Abstract

A system for rapidly detecting power disturbances with ferroresonant transformers having a decay profile comprising the steps of rectifying a power signal; comparing the rectified signal against a reference signal; comparing the rectified signal against a dynamic reference signal; and generating a power-fail signal in response to either comparison falling below its respective reference.

Claims

1. A method for rapidly detecting power signal disturbances in power systems with transformers having energy storage decay profiles, the method comprising the steps of:

comparing the power signal against a dynamic reference signal;

comparing the power signal against a relatively absolute reference signal; and

generating a power-fail signal in response to either comparison approximating its respective reference, whereby the dynamic reference signal decay is long relative to the transformer energy storage decay profile and the power-fail signal indicates a power disturbance.

4. A method for fast power disturbance detection as claimed in claim 1, further comprising:

controlling, with variable gain, the step of comparing the power signal against a dynamic reference signal.

5. A method for fast power disturbance detection as claimed in claim 4 further including:

compensating temperature-induced variations associated with the step of controlling, with variablegain the power signal against a dynamic reference signal.

6. A method for fast power disturbance detection as claimed in claim 1 further comprising the step of:

switching to an alternate power source in response to the generated power-fail signal.

7. A method for fast power disturbance detection as claimed in claim 1 wherein:

the power signal is rectified.

2. A fast power signal disturbance detector in power systems with transformers having energy storage decay profiles, the detector comprising:

means for comparing the power signal against a dynamic reference signal;

means for comparing the power signal against a relatively absolute reference; and

means for generating a power-fail signal in response to either comparison approximating its respective reference,

whereby the dynamic reference signal decay is long relative to the transformer energy decay profile and the power-fail signal indicates a power disturbance.

3. A fast power signal disturbance detector in power systems with ferroresonant transformers having energy storage decay profiles comprising:

means for full wave rectifying a power signal;

means for comparing the rectified power signal against a dynamic reference signal including

a comparator in a variable gain controlled loop;

means for comparing the rectified power signal against a relatively absolute reference signal; and

means for generating a power-fail signal in response to either comparison approximating its respective reference further comprising;

an AND gate having one input coupled to the dynamic reference comparator, another input coupled to the relatively absolute reference comparator and an output, and

a Johnson ring counter missing pulse

detector coupled to the AND gate output.

8. An AC line-fail and brown-out voltage detection apparatus for protecting equipment utilizing a ferro-resonant transformer, said apparatus comprising in combination:

rectification means for providing a unipolar waveform having a magnitude proportional to the incoming AC line voltage and synchronized to the frequency thereof;

missing pulse detection means for normally receiving a pulse train and generating a power fail output signal upon receipt of a pulse train having a missing pulse; and

two-part voltage detection means interposed between said rectification means and said missing pulse detection means for detecting the magnitude and rate-of-decrease of said waveform with respect to fixed and dynamically determined limits and outputting a pulse train having a missing pulse when said waveform is below said limits, thereby providing a fast power fail output signal for protecting said equipment.

9. The apparatus according to claim 8 wherein said rectification means includes full-wave rectification means.

10. The apparatus according to claim 8 wherein said rectification means includes half-wave rectification means.

11. The apparatus according to claim 8 wherein said missing pulse detection means includes resettable counter means operating in conjunction with time base means for monitoring said combined output pulse train at a clock rate substantially greater than the frequency of said waveform.

12. The apparatus according to claim 8 wherein said two-part voltage detection means includes:

brown-out detection means for detecting when said waveform drops below a fixed minimum voltage;

sag detection means for detecting when said waveform decreases too quickly below a moving-average voltage established by said waveform; and

logic gate means for providing a combined output pulse train based upon the output pulse train from each of said voltage detection means.

13. The apparatus according to claim 8 wherein power fail output signal is utilized for activating alternate power supply means in place of said AC line, thereby maintaining uninterrupted operation of said equipment.

14. An AC line-fail and brown-out voltage detection apparatus for uninterruptably maintaining operation of equipment utilizing a ferro-resonant transformer, said apparatus comprising in combination:

rectification means for providing a unipolar waveform having a magnitude proportional to the incoming AC line voltage and synchronized to the frequency thereof;

missing pulse detection means for normally receiving a pulse train and generating a power fail output signal upon receipt of a pulse train having a missing pulse;

switching means for switching said equipment from said ferro-resonant transformer to an alternate source of supply such as a backup battery upon receipt of said power fail output signal; and

two-part voltage detection means interposed between said rectification means and said missing pulse detection means for detecting the magnitude and rate-of-decrease of said waveform with respect to fixed and dynamically determined limits and outputting a pulse train having a missing pulse when said waveform is below said limits, thereby providing a fast power fail output signal for maintaining uninterrupted operation of said equipment.

15. A circuit for detecting an AC line-fail and brown-out voltage condition for protecting equipment utilizing a ferro-resonant transformer, said circuit comprising in combination:

a rectifier circuit converting said AC line voltage into a proportional, unipolar, synchronous waveform;

a counter having a reset input, a clock input driven by a suitable timebase, and a disable input which is driven by an output of said counter; and

a brown-out detector and a sag detector having a logic gate for combining the outputs thereof, and interposed between said rectifier circuit and said counter,

said brown-out detector indicating that said waveform has dropped below a fixed minimum voltage and said sag detector indicating that said waveform has decreased too quickly below its moving-average reference voltage and outputting from said logic gate a pulse train having a missing pulse so as to delay resetting said counter, thereby providing a fast power fail output signal for protecting said equipment.

16. The circuit of claim 15 wherein said rectifier circuit includes a full-wave rectifier arrangement.

17. The circuit of claim 15 wherein said rectifier circuit includes a half-wave rectifier arrangement.

18. The circuit of claim 15 whereins said rectifier circuit includes at least one resistive divider network for providing a waveform proportional to said AC line voltage.

19. The circuit of claim 15 wherein said counter includes a Johnson ring counter.

20. The circuit of claim 15 wherein said timebase includes an oscillator.

21. The circuit of claim 15 wherein said timebase includes a high-frequency oscillator and a frequency divider.

22. The circuit of claim 15 wherein said timebase outputs a first frequency of approximately 484 Hertz to said counter.

23. The circuit of claim 15 wherein said timebase outputs a second frequency of approximately 124 kilohertz to said sag detector.

24. The circuit of claim 15 wherein said brown-out detector includes a voltage comparator having a present fixed reference voltage.

25. The circuit of claim 15, wherein said sag detector comprises an AGC loop having a slowly-changing variable-gain characteristic, including a variable-gain stage, a comparator coupled to an output of said variable-gain stage, an inverter coupled to an output of said comparator, and a fixed-delay monostable stage coupled to an output of said inverter, and an included network for establishing a moving average reference voltage based upon said waveform.

26. The circuit of claim 25 wherein said variable gain stage includes an amplifier and a variable attenuator.

27. The circuit of claim 25 wherein said monostable stage includes a counter having a reset input and a clock input which is driven from said timebase so as to effect a fixed delay of approximately 1 millisecond.

28. The circuit of claim 15, wherein said sag detector comprises an AGC loop having a slowly-changing variable-gain characteristic including a variable-gain stage, a comparator coupled to an output of said variable-gain stage, and a network for establishing a moving-average reference voltage which has temperature-compensating components, such as a zener diode and a thermistor.

29. The circuit of claim 15 wherein said sag detector comprises an AGC loop having a slowly-changing variable-gain characteristic including a variable-gain stage, a comparator coupled to an output of said variable-gain stage, and a network coupled to an output of said comparator for establishing a moving-average reference voltage.

30. The circuit for detecting an AC line-fail and brown-out voltage condition for uninterruptably maintaining operation of equipment utilizing a ferro-resonant transformer, said circuit comprising in combination:

a rectifier circuit converting said AC line voltage into a proportional, unipolar synchronous waveform;

a counter having a reset input, a clock input driven by a suitable timebase, and a disable input which is driven by the output of said counter;

an electronic switch for electrically switching said equipment from said ferro-resonant transformer to an alternate source of supply such as a backup battery upon receiving said power fail output signal; and

a brown-out detector and a sag detector having a logic gate for combining the outputs thereof, and interposed between said rectifier circuit and said counter,

said brown-out detector indicating that said waveform has dropped below a fixed minimum voltage and said sag detector indicating that said waveform has decreased too quickly below its moving-average reference voltage and outputting from said logic gate a pulse train having a missing pulse so as to delay resetting said counter, thereby providing a fast power fail output signal for maintaining uninterrupted operation of said equipment.

31. A method of detecting an AC line-fail and brown-out voltage condition for protecting equipment utilizing a ferro-resonant transformer, said method comprising the steps of:

rectifying said AC line voltage and providing a proportional, unipolar waveform synchronized thereto;

monitoring a pulse train and generating a power fail output signal upon receipt of a pulse train having a missing pulse; and

detecting the magnitude and rate-of-decrease of said waveform with respect to fixed and dynamically determined limits and outputting a pulse train having a missing pulse when said waveform is below said limits, thereby providing a fast power fail output signal for protecting said equipment.

32. The method of claim 31 wherein the step of rectifying said AC line voltage includes full-wave rectifying.

33. The method of claim 31 wherein the step of rectifying said AC line voltage includes half-wave rectifying.

34. The method of claim 31 wherein the step of monitoring a pulse train includes resetting a counter which continually counts the number of cycles of a timebase frequency and generates a power fail output signal only when said counter receives a pulse train having a missing pulse.

35. The method of claim 31 wherein the step of detecting the magnitude of said waveform includes comparing it to a fixed, minimum voltage and the step of detecting the rate-of-decrease in said waveform comprises comparing it to a moving-average voltage established by said waveform.

36. A method of detecting an AC line-fail and brown-out voltage condition for uninterruptably maintaining operation of equipment utilizing a ferro-resonant transformer, said method comprising the steps of:

rectifying said AC line voltage and providing a proportional, unipolar waveform synchronized thereto;

monitoring a pulse train and generating a power fail output signal upon receipt of a pulse train having a missing pulse;

switching said equipment from said ferro-resonant transformer to an alternate source of supply such as a backup battery upon receiving said power fail output signal; and

detecting the magnitude and rate-of-decrease of said waveform with respect to fixed and dynamically determined limits and outputting a pulse train having a missing pulse when said waveform is below said limits, thereby providing a fast power fail output signal for maintaining uninterrupted operation of said equipment.