Redundant Ignition Control Circuit and Method

Abstract

A redundant ignition control system and method for gas burning appliances is provided. The system utilizes a main processor and a supervisory processor to provide the redundant, fail safe operation of both the pilot valve and the main gas valve of the appliance. Three switching elements under the control of the two processors, as well as the use of high pass filters to block DC from the gas control valves provide redundant, fail safe operation. The use of variable duty cycle or frequency pulse width modulated signals enables use in low power applications and ensures system safety. Inclusion of a gas valve verification sequence, ignition sequence, burner monitoring sequence, and heat shutdown and standby sequences ensures safe, low power operation during normal control, and fail safe operation upon the failure of any component of the system.

Description

FIELD OF THE INVENTION[0001]This invention generally relates to ignition control systems for intermittent pilot and direct spark ignition systems for gas burners, and more particularly to fail safe ignition control systems for such intermittent pilot and direct spark ignition systems enabling use of low power or self-powered sources.BACKGROUND OF THE INVENTION[0002]Ignition control systems, such as those used in controlling the flow of gas to a pilot burner and a main burner for gas fired water heaters, space heaters and furnaces are increasingly utilizing intermittent pilot or direct spark ignition systems, which do not use a standing pilot. These intermittent pilots most commonly use a flame sensing circuit to detect the presence of a flame before allowing the opening of the main gas valve that supplies the main burner to avoid unconsumed fuels from flowing freely.[0003]As more and more applications are relying on low power sources, such as battery power or self-powered implementa...

AI Technical Summary

Benefits of technology

[0006]In one embodiment of the present invention, a redundant gas valve control system and method that provides fail safe gas valve operation with minimum power consumption is provided. The system utilizes dual microprocessor technology with simplified communication techniques between the microprocessors, preferably utilizing a general purpose input output (I / O). Such an embodiment minimizes resources required by each processor and allows for use of simple, low cost components. The system minimizes power consumption by sensing the supply voltage and energizing the gas valve control coils with variable pulse width modulated (PWM) power instead of utilizing a DC voltage to activate and hold the valves. As such, the system is particularly useful in intermittent pilot or direct spark ignition systems without a standing pilot flame in low power applications, such as battery powered or self powered systems.

[0007]In one embodiment the pilot and main gas valves are controlled by three switching elements. In one embodiment each of the pilot valve and the main gas valve are controlled by a switching element under the control of the main processor. A third switching element, a gas valve supply switch under the control of the supervisory processor, controls the power to both of the main valve switch and the pilot valve switch. In one embodiment of the present invention, additional fail safe circuitry in the form of a high pass filter is interposed between the switching element and the gas valve. This high pass filter ensures that only the properly generated high frequency signal will energize the gas valves, and prevents the application of DC voltage that may be generated by a fault within the system from energizing the gas valves.

Problems solved by technology

As more and more applications are relying on low power sources, such as battery power or self-powered implementations via a thermopile or hydro generator, the energy consumption of typical ignition control systems becomes a serious design issue.

Unfortunately, the control methods used by these typical ignition control systems to energize and hold open these valves during the entire call for heat event is not compatible with newer lower voltage supplies.

This power problem is further compounded when failsafe operation of the gas valves is considered.

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