Low cost high speed spark voltage and flame drive signal generator

• US 8,300,381 B2
• Filed: 02/10/2009
• Issued: 10/30/2012
• Est. Priority Date: 07/03/2007
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Chian, Brent, McDonald, Jonathan, Planer, Norm
• Primary Examiner(s): Jackson, Stephen W
• Application Number:
  US12/368,830
• Publication Number:
  US 20090136883A1
• Time in Patent Office: 1,358 Days
• Field of Search: 361/253
• US Class Current: 361/253
• CPC Class Codes: H03K 3/57 the switching device being a semiconductor device

Abstract

A system for generating a high DC voltage for a spark to ignite a flame in a combustion device, and a high AC voltage for a flame rod to sense a flame in the device, from a low voltage for combustion device control. The system may be an inexpensive mechanism.

Claims

1. A spark voltage and flame rod voltage generator for a combustion device, comprising:

a driver for receiving a low-voltage supply and a control signal;

an inductive-capacitive (LC) circuit connected to an output of the driver, for providing a flame rod voltage; and

a rectification-capacitive circuit connected to an output of the LC circuit for providing a spark voltage.

2. The generator of claim 1, wherein the low voltage supply has a magnitude less than magnitudes of the flame rod voltage and the spark voltage.

3. The generator of claim 1, wherein the frequency of the control signal can be changed to approach or equal a resonant frequency of the LC circuit.

4. The generator of claim 3, wherein:

a change in pulse width of the control signal can change the magnitudes of the flame rod voltage and the spark voltage; and

a change in frequency of the control signal can change the magnitudes of the flame rod voltage and the spark'"'"'voltage.

5. The generator of claim 1, further comprising:

a voltage sensing circuit connected to the output of the LC circuit;

a direct current (DC) blocker having a first end connected to the output of the LC circuit;

a flame rod connected to a second end of the DC blocker; and

a flame sensing circuit connected to the second end of the DC blocker.

6. The generator of claim 5, further comprising a controller having a first input connected to the voltage sensing circuit, a second input connected to the flame sensing circuit, and a first output for providing the control signal to the driver.

7. The generator of claim 6, further comprising a spark mechanism having a voltage input connected to an output of the rectification-capacitive circuit and a control input connected to a second output of the controller.

8. The generator of claim 7, further comprising:

a connection mechanism connected between the flame rod and the DC blocker; and

a compensation circuit, for reducing effects of an impedance of the connection mechanism upon the flame sensing circuit, having an input connected to the connection mechanism and an output connected to a third input of the controller.

9. The generator of claim 8, further comprising a current limiter connected in between the second end of the DC current blocker and the connection mechanism.

10. The generator of claim 9, wherein the controller has a third output for providing a bias voltage to the flame sensing circuit.

11. The generator of claim 9, wherein the first, second and third inputs of the controller are connected to analog-to-digital converters.

12. A method for generating a spark voltage and a flame rod voltage for a combustion device, from a low voltage supply of the combustion device, comprising:

providing an electrical supply having a first voltage to a driver circuit;

providing a pulse width modulation (PWM) signal having a duty cycle and a frequency to the driver circuit for driving an inductor-capacitor (LC) circuit with the PWM signal;

adjusting the pulse width and frequency of the PWM signal to obtain a near sinusoidal signal having a second voltage at an output of the LC circuit;

rectifying the near sinusoidal signal having the second voltage into a direct current (DC) signal; and

charging up a capacitor with the DC signal for a spark voltage.

13. The method of claim 12, further comprising:

lowering the second voltage of the near sinusoidal signal to a third voltage without effectively affecting the spark voltage on the capacitor; and

providing the near sinusoidal signal having the third voltage as a flame rod voltage; and

wherein each of the second and third voltages is greater than the first voltage.

14. The method of claim 13, further comprising:

providing the spark voltage to a spark mechanism for providing a spark in the combustion device when desired;

providing the near sinusoidal signal having the third voltage to a flame rod via a DC blocker; and

determining whether there is a flame via a voltage signal at the flame rod.

15. The method of claim 14, further comprising compensating the voltage signal at the flame rod.

16. A spark voltage and flame rod voltage generator for a combustion device, comprising:

an inductor-capacitor (LC) circuit;

a driver for driving the LC circuit with a pulse width modulated (PWM) signal;

a spark voltage circuit connected to an output of the LC circuit;

a voltage sensing circuit connected to the output of the LC circuit;

a flame sensing circuit connected via a direct current (DC) blocking device to the output of the LC circuit; and

a flame rod connected via the DC blocking device to the output of the LC circuit.

18. The generator of claim 16, wherein:

the PWM signal has a frequency which can be varied to nearly match a resonant frequency of the LC circuit so as to generate a near sinusoidal signal at the output of the LC circuit; and

the PWM signal has a duty cycle which can be varied to adjust an amplitude of the near sinusoidal signal.

19. The generator of claim 18, further comprising:

a voltage sensing circuit for detecting a voltage at the output of the LC circuit; and

wherein;

the spark voltage circuit comprises;

a storage device for holding a second voltage for a spark; and

a rectifier having a first end connected to the output of the LC circuit and having a second end connected to the storage device;

the frequency and/or duty cycle of the PWM signal can be adjusted to charge the storage device to the second voltage; and

the frequency and/or duty cycle of the PWM signal can be adjusted to reduce a third voltage at the output of the LC circuit to less than the second voltage; and

the frequency and/or duty cycle of the PWM signal can be adjusted as desired to change the third voltage for the flame rod.

20. The generator of claim 16, further comprising:

a controller having inputs connected to the voltage sensing circuit and the flame sensing circuit, and having an output for providing the PWM signal to the driver; and

a compensation circuit having a high impedance input connected to the flame rod and a low impedance output connected to the controller; and

wherein the compensation circuit comprises;

a voltage divider having a first end being the high impedance input, a second end connected to a reference voltage, and a terminal connected between the first and second ends of the voltage divider; and

a peak detector having an input connected to the terminal and having an output being the low impedance output.

17. The generator of 16, wherein:

the generator uses a power supply having a first voltage;

the spark voltage circuit is for providing a second voltage;

the output of the LC circuit has a third output voltage; and

each of the second and third voltages is greater than the first voltage.