CIRCUIT DIAGNOSTICS FROM FLAME SENSING AC COMPONENT

• US 20070188971A1
• Filed: 02/15/2006
• Published: 08/16/2007
• Est. Priority Date: 02/15/2006
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Chian, Brent, Nordberg, Timothy
• Granted Patent: US 8,875,557 B2
• Time in Patent Office: Days
• US Class Current: 361/247
• CPC Class Codes: F23N 2227/16 Checking components, e.g. electronic
• CPC Class Codes: F23N 2229/06 with periodical shutters; Modulation signals
• CPC Class Codes: F23N 2229/12 with flame rectification current detecting means
• CPC Class Codes: F23N 5/242 using electronic means

Abstract

A diagnostic flame sensing circuit having less filtration so that an AC component of a flame sensing input is available for circuit diagnostics. Synchronized data sampling may used to detect the peak to peak magnitude of the residual AC component. A comparison of the magnitude of the component relative to a magnitude of the component during normal operation of the circuit may be used to check the condition of nearly all of the elements in the circuit.

Claims

1. A diagnostic flame sensing circuit comprising:

a chopper;

a high voltage DC source connected to a first terminal of the chopper; and

a filter connected to a second terminal of the chopper; and

wherein;

a first output of the filter is for a flame sensor;

a second output of the filter is available for an analysis; and

when the flame sensing circuit is activated, an analysis of the second output of the filter may reveal diagnostics.

2. The circuit of claim 1, wherein the diagnostics may comprise:

when a ripple of the second output of the filter is noticeably greater than a normal ripple, one or more components of the flame sensing circuit may be abnormal;

when the ripple of the second output of the filter is noticeably less than the normal ripple, one or more components of the filter may be abnormal; and

/or

when the flame sensing rod is not driven and the ripple of the second output of the filter is reasonably observable, there may be significant noise at the input to the filter.

3. The circuit of claim 2, wherein when the high voltage DC source is not providing a significant voltage to the first terminal of the chopper and the ripple is significant, there may be significant noise from the high voltage DC source, a filter component may be abnormal, or the chopper may be receiving a drive signal from the frequency generator.

4. A circuit diagnostics system comprising

an input terminal;

a chopper having a switchable terminal that alternatively connects to the input terminal and to a reference ground according to a signal to a drive terminal of the chopper;

a first capacitor having a first lead connected to the switchable terminal of the chopper and having a second lead;

a first resistor having a first end connected to the second lead of the first capacitor, and having a second end connected to an output terminal; and

a second capacitor having a first lead connected to the output terminal, and having a second lead connected to the reference ground.

5. The system of claim 4, further comprising a bias voltage control mechanism connected to the output terminal.

6. The system of claim 4, wherein the second lead of the first capacitor may be connectable to a flame sensor.

7. The system of claim 4, further comprising a voltage sensor connected to the input terminal.

8. The system of claim 7, wherein the voltage sensor is a voltage divider connected across the input terminal and the reference ground, and having a middle terminal.

9. The system of claim 8, further comprising a third capacitor having a first lead connected to the input terminal and a second lead connected to the reference ground.

10. The system of claim 9, further comprising:

a fourth capacitor connected between the chopper and the first capacitor; and

wherein the fourth capacitor has a first lead connected to the switchable terminal of the chopper and a second lead connected to the first lead of the first capacitor.

11. The system of claim 10, further comprising a second resistor having a first end connected to the first lead of the first capacitor and having a second end connected to the reference ground.

12. The system of claim 4, further comprising a controller having a first input connected to the output terminal.

13. The system of claim 12, wherein the controller comprises:

an analog-to-digital converter (ADC) connected to the output terminal; and

a processor connected to the ADC.

14. The system of claim 13, further comprising a diagnostics indicator connected to the processor.

15. The system of claim 14, wherein the diagnostics indicator notes the condition of various components according to a ripple voltage at the output terminal.

16. The system of claim 11, further comprising:

a third resistor having a first end connected to the output terminal and a second end connected to a voltage control mechanism; and

an analog-to-digital converter having an input connected to the output terminal; and

wherein the chopper has a drive terminal.

17. The system of claim 16, wherein if a magnitude of the ripple voltage at the output terminal is greater than a magnitude of a normal ripple voltage at the output terminal, then a cause may be one or a combination of:

the first resistor is leaky;

the second capacitor has reduced capacitance;

the second resistor is open;

the voltage divider has an incorrect ratio;

the fourth capacitor and/or the first capacitor is shorted;

or

the signal to the drive terminal of the chopper has too low of a frequency.

18. The system of claim 16, wherein if a magnitude of the ripple voltage is less than a magnitude of a normal ripple voltage at the output terminal, then a cause may be one or a combination of:

the second capacitor is leaky;

the second resistor and third resistor are leaky;

the voltage divider has an incorrect ratio;

the ADC has sensing periods out of sync with the switchable terminal of the chopper;

the chopper is not operating;

the signal to the drive terminal of the chopper has too high of a frequency;

the fourth capacitor has a reduced capacitance;

the fourth capacitor is open;

the first capacitor has a reduced capacitance;

or

the first capacitor is open.

19. The system of claim 16, wherein the chopper is deactivated and a magnitude of the ripple voltage is greater than a fraction of a magnitude of a normal ripple voltage at the output terminal, then a cause may one or a combination of:

the high system noise;

or

the chopper is operating when it should not be operating.

20. The system of claim 16, further comprising a DC-to-DC circuit having an output connected to the input terminal.

21. The system of claim 20, wherein the chopper is deactivated and a magnitude of the ripple voltage is greater than a magnitude of a normal ripple voltage at the output terminal, then a cause may be one or a combination of:

an output noise of the DC-to-DC circuit is high;

the third capacitor has a reduced capacitance;

or

the chopper is operating when it should not be operating.

22. A circuit diagnostics system comprising:

an input terminal for receipt of an AC voltage relative to a first reference ground;

a first capacitor having a first lead connected to the input terminal, and having a second lead;

a first resistor having a first end connected to the second lead of the first capacitor, and having a second end;

a second capacitor having a first lead connected to the second end of the first resistor, and having a second lead connected to a second reference ground;

a second resistor having a first end connected to the first lead of the second capacitor and having a second end connected to an output terminal;

a third capacitor having a first lead connected to the output terminal, and a second lead connected to the second reference ground; and

when the circuit diagnostics system is activated, then a ripple voltage at the output terminal contains diagnostics information.

23. The system of claim 22, further comprising a voltage sensing circuit connected to the input terminal.

24. The system of claim 22, further comprising:

an analog-to-digital converter having an input connected to the output terminal; and

wherein the resistors and capacitors are components of the circuit diagnostics system.

25. The system of claim 24, wherein:

when the ripple voltage of the output terminal is greater than a normal ripple voltage, then one or more components of the circuit diagnostics system may be abnormal;

or

when the ripple voltage of the output terminal is noticeably less than the normal ripple voltage, then one or more components of the circuit diagnostics system may be abnormal.

26. The system of claim 24, wherein with an AC voltage at the input terminal, and a magnitude of the ripple voltage being less than a magnitude of a normal ripple voltage, then a cause may be one or a combination of:

the second and/or third capacitor has leakage;

the analog-to-digital converter sensing is not in synchronization with the AC voltage at the input terminal;

the AC voltage at the input terminal has ceased;

or

the first and/or second resistor is open;

the first capacitor is open or too small.

27. The system of claim 23, wherein with a normal voltage at the input terminal, and a magnitude of the ripple voltage is greater than a magnitude of a normal ripple voltage, then a cause may be one or a combination of:

the first and/or second resistor has leakage;

the second and/or third capacitor is smaller than normal or open;

the AC voltage varies and the voltage sensing circuit is not operating or is operating but not accurately;

or

the first capacitor is shorted.