FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE
Specification
(See Section 10; rule 13)
SYSTEMS AND METHODS FOR CONTROLLING MULTISTAGE ELECTRONIC CONTROLLED GAS VALVE
EMERSON ELECTRIC CO.
a US Company
Of 8000 West Florissant Avenue
St. Louis, Missouri 63136
USA
INVENTORS:
1. BROKER JOHN F
2. TAW ARE SACHEM
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

TECHNICAL FIELD
The present disclosure relates to systems and methods for controlling gas flow to a gas-fired appliance, and more particularly relates to an electronic control system for an electronic controlled multistage gas valve for controlling gas flow to such an appliance.
BACKGROUND
Conventional electronic control systems for control of gas flow to a gas-fired appliance include a gas valve member that is moved by a magnetic field generated by a coil to vary gas flow rate. For the purpose, a control unit controls actuation of one or more gas valve relays through which power is supplied to the coil. For example, in a typical two-stage heating furnace, at least two gas valve relays, Stage I and Stage II, are provided in the control unit, also referred to as furnace control unit. When there is a call for heat at a particular stage, for example, at Stage II, both the gas valve relays gets ON, and a 24VAC signal is applied to an ON/OFF type gas valve so as to open the gas valve to Stage II.
A typical electronic controlled gas valve system 100 for control of a two-stage gas valve, hereinafter interchangeably referred to as "gas valve", is shown in Fig. 1. The gas valve (not shown here) can be a mechanical or an electromechanical valve driven by a gas valve control unit 104. The gas valve control unit 104 is in turn controlled by a control unit 102, which is electronically coupled to the gas valve control unit 104.
The control unit 102 receives a 24VAC input from an AC power source 106, and through gas valve relays Rland R2, sends 24 AC signals to the gas valve control unit 104 over wires wl and w2. The relays Rl and R2 may be part of a consolidated relay unit 105 having one or more relays integrated into it as per the requirement. Typically, the relays Rl and R2 are coupled to the AC power

source through at least one rectifier circuit (not shown here), typically a half-bridge rectifier, such that the rectifier circuit provides a half-wave rectified supply to the relay coil(s) for switching them ON/OFF. Also, an un-rectified 24VAC supply is provided to relay contacts so that the relays Rl and R2 send 24VAC signals to the gas valve control unit 104.
-Further, the gas valve control unit 104 is shown to include two hardware circuits 108 and 110. The hardware circuits 108 and 110 are configured to process the signals received from the respective relays Rl and R2 of the control unit 102. Outputs from the respective hardware circuits 108 and 110 are sent to a controller device 112, such as a microcontroller, which is configured to control energizing/de-energizing of a coil 124 coupled to the gas valve control unit 104. In operation, the hardware circuits 108 and 110 detect the presence of signals from the relays Rl and R2 for the controller device 112. When there is a call for heat, for example, at Stage II, both the relays Rl and R2 send 24VAC signals to the gas valve control unit 104. The hardware circuits 108 and 110 make the 24VAC signals from the two relays Rl and R2 out of phase. The controller device 112 checks whether the received signals are out of phase with each other before it opens the mechanical gas valve for Stage II.
The microcontroller 112 is powered by a microcontroller power supply 114, which is in series connection to a power supply circuit 116 of the gas valve control unit 104. The power supply circuit 116 gets power from the 24VAC power source 106 through relay Rl, as shown. When there is call for heat, relay Rl gets energized and provides 24VAC power to the gas valve control unit 104.
Apart from receiving the signals from the hardware circuits 108 and 110, the controller device 112 may also receive other input signals, for example, input from a gas selection unit 118, which could suggest an alternative fuel source and/or inputs from a first and a second gas valve feedback units 120 and 122, which could be photo-interrupters used for determining current position of the

two-stage gas valve. The first and second feedback units 120 and 122 may provide analog or digital signals to indicate the current position of the gas valve.
The controller device 112 processes the inputs to provide output signals for regulating power supplied to the coil 124. For the purpose, the coil 124 is coupled to the controller device 112 via two voltage-controlled switching devices 126 and 128, which may include field-effect transistors (FETs) or similar devices. The microcontroller provides a digital voltage signal, such as a "High" signal or "Low" signal, to one of the switching device, say the switching device 126, and a pulse width modulated (PWM) duty cycle signal to the other switching device, the switching device 128. Based on the signals received, the switching devices 126 and 128 control magnetization of the coil 124, which consequently impacts a current position of the two-stage gas valve so as to control the gas flow through the gas valve to the gas-fired appliance.
In the conventional control systems for controlling the movement of the gas valve as discussed above, at least two gas valve relays are required. The cost of implementing two gas valve relays is too high. In addition, there are space constraints too.
Moreover, if the Stage I or the Stage II gas valve relay gets stuck or the associated hardware fails due to some reason, the 24 VAC signal nevertheless is constantly applied to the gas valve control unit and the associated coil and/or the gas valve may remain continuously energized or open. This could lead to a hazardous situation for people working in the vicinity as well as the property where the whole set up is fixed.
In conventional control unit designs, such a state is displayed as an "error' condition and the control unit operates towards tuning the gas valve relays OFF, However, since one or more of the gas valve relays has already failed, the control unit does not have the actual control on the operation of the gas valve, and the gas may continue to leak unchecked from the gas valve.

Further, in case of a multiple stage gas valve control (control of more than two stages), the conventional control units communicate with the gas valve through communication protocols, such as Climate Talk, to operate the valve in a particular stage. Implementation of a communication network is a cost intensive approach and increases the overall cost of the control system.
There seems to be certain solutions available in the market for controlling the operation of electronically controlled gas valves as discussed above. For example, US4832594 provides a control system with time redundancy, wherein the integrated controller is designed to have 3 timers. Two of the timers form the lower and upper time limits, during which the third timer must enable the gas valve relay. If any of the timers is faulty, the gas valve relay will not work.
Further, in US20100075264, a redundant ignition control circuit has been disclosed, wherein the redundant ignition control circuit includes a main microprocessor and a supervisory microprocessor, which communicate with each other through PWM signals. In addition, each microprocessor uses a PWM signal to activate the relay under its control, based on the current mode of operation of the gas valve. The relays may be replaced with MOSFETs or BJTs in different implementations. However, aforesaid solutions have limitations and are vulnerable to safety lapses on the part of the technician. Moreover, there is a need for a solution that is cost efficient, simple to implement, and has easy back-compatibility.
SUMMARY
According to the present disclosure, an electronic control unit for controlling an electronic controlled multistage gas valve (MGV) for adjusting gas flow to a gas fired appliance is described. In an embodiment, the electronic control unit comprises an integrated furnace control (IFC) unit, a multistage gas valve

control (MGVC) unit electronically coupled to said IFC unit, and a coil electronically coupled to said MGVC unit, wherein the IFC unit, over a first communication line, provides at least one power supply signal, and over a second communication line, provides at least one pulse width modulated (PWM) duty cycle signal to said MGVC unit for controlling at least one of energizing and de-energizing of said coil, wherein the electronic controlled MGV is adapted to move in response to a magnetic field generated by said coil.
In accordance with an aspect of the present disclosure, a method of controlling an operation of an electronic controlled multistage gas valve of a gas fired appliance is described. The method, in an implementation, comprises detecting the presence of a power supply signal from an integrated furnace control unit, detecting the presence of a pulse width modulated duty (PWM) cycle signal from said integrated furnace control unit, and at least one of energizing and de-energizing a coil of a MGVC unit based on said detecting of the presence of said power supply signal and said PWM duty cycle signal.
OBJECTS
Some of the objects of the tool of the present disclosure, which at least one embodiment discussed herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of
the state-of-the-art or at least provide a useful alternative.
An object of the present disclosure is to provide a system for controlling a multistage electronic controlled gas valve (gas valve) that is cost inexpensive as compared to conventional systems used for the same purpose.
Another object of the present disclosure is to provide a system for controlling a multistage electronic controlled gas valve that is less dependent on relay-based signaling for achieving the desired control of the gas valve.

Yet another object of the present disclosure is to provide a electronic controlled gas valve system that is compatible with existing electronic controlled gas valve
systems.
Another object of the present disclosure is to provide a system for controlling an electronic controlled multistage gas valve that is capable of handling various stages of gas flow to a gas fired appliance with minimum or no modifications.
Another object of the present disclosure is to provide a system and a method for controlling a multistage electronic controlled gas valve that is safe and reliable.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
BRIEF DESCRIPTION OF DRAWINGS
The systems and methods for controlling multistage electronic controlled gas valve of the present disclosure will now be explained in relation to the accompanying non-limiting drawings, in which:
FIGURE 1 illustrates a block representation of a conventional two-stage gas valve control system;
FIGURE 2 illustrates a block representation of an electronic control system for controlling a multistage gas valve, in accordance with an embodiment of the present disclosure;
FIGURE 3 illustrates a schematic representation of the electronic control system of Figure 2, in accordance with an embodiment of the present disclosure;
FIGURE 4 illustrates a detailed block representation of the electronic control system of Figure 2, in accordance with an embodiment of the present disclosure; and

FIGURE 5 illustrates an AC signal and a PWM signal as sent from an integrated furnace control unit of the electronic control system of Figure 2;
DETAILED DESCRIPTION
The disclosure will now be described with reference to the accompanying drawings, which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The description hereinafter, of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with

modification within the spirit and scope of the embodiments as described herein.
Referring to Figures 2 to 4, an electronic control system 200 for controlling a multistage electronically-controlled gas valve is shown in accordance with one or more embodiments of the present disclosure.
As shown in Fig. 2, the electronic control system 200 includes an integrated furnace control (IFC) unit 202 and an electronic gas valve unit 204. The electronic gas valve unit 204 further comprises a multistage gas valve control unit (MGVC) 208. The integrated control unit 202 controls operations of the MGVC unit 208, which in turn governs the controlling of a mechanical gas valve 210 coupled to the MGVC unit 208.
In an embodiment, the IFC unit 202 includes a gas valve relay 206, which turns ON whenever there is a call for heat. For example, in an embodiment, a user makes a call for heat by sending a signal to the IFC unit 202 to turn ON the electronic control system 200.
In an implementation, a 24VAC signal (S1 is applied to the MGVC unit 208 through the gas valve relay 206. In addition, the IFC unit 202 sends a pulse width modulated (PWM) duty cycle signal (S2), or simply PWM signal, to the MGVC unit 208. In an embodiment, the IFC unit 202 includes a transistor configured to generate a PWM signal with a desired duty cycle.
The MGVC unit 208, based on the PWM signal with the desired duty cycle, for example, a 50% duty cycle or a 100% duty cycle, opens the valve to the respective stage. So even though the MGVC unit 208 is ON because of the 24VAC signal being received continuously through the gas valve relay 206, the MGVC unit 208 will not turn the mechanical gas valve 210 to a different position of functioning unless the MGVC unit 208 receives the PWM signal too from the IFC unit 202. Thus, in case the IFC unit 202 gets stuck and the MGVC

unit 208 continuously receives the 24VAC signal, the MGVC unit 208 will not turn the mechanical gas valve 210 ON unless the desired PWM signal is not sensed by the MGVC unit 208.
Further, the electronic control system 200, which has only one gas valve relay 206 provided in the IFC unit 202, also provides for varied stages of operation of the mechanical gas valve 210 by providing a PWM signal with different duty cycles. Thus the electronic control system 200 uses a single gas valve relay 206 and a PWM signal to control varied operations of the mechanical gas valve 210.
Figure 3 shows a schematic representation of the electronic control system 200 of Figure 2. As shown in the IFC unit 202, a 24 VAC signal is applied to contacts of the gas valve relay 206 while through a half-wave bridge (not shown), a DC supply from the 24VAC is applied to power a relay coil of the gas valve relay 206 and the rest of the low voltage circuits, like a microprocessor. The half-wave bridge makes the relay coil magnetized and switches the gas valve relay 206 to ON/OFF states. The gas valve relay 206, through its contacts, is coupled to a primary controller 302, such as a microcontroller, of the MGVC unit 208 over wire wl. On the other hand, the MGVC unit 208 may include a dedicated power supply 304 for controlling a power supply to the primary controller 302. The dedicated power supply 304 may be powered by the 24VAC power supply over a common line (not shown here).
Further, a switching device 306 such as a transistor or an isolated switching device is provided in the IFC unit 202, which is configured to provide a PWM signal with a predefined duty cycle. The PWM signal is applied to the primary controller 302 via a hardware circuitry 308 over line w2. In an embodiment, the hardware circuitry 308 may include an optoisolator for isolating an input side from an output side so as to provide an isolated PWM signal. The primary controller 302 is further coupled to a coil 314 through appropriate switching devices 310 and 312. In an embodiment, the switching devices 310 and 312 may

include field-effect transistors and the likes. The primary controller 302 controls energizing/de-energizing of the coil 314, which in turn governs the controlling of the mechanical gas valve 210. In an implementation, the coil 314 may include a coil of a stepper motor, which upon activation of the coil 314 changes a position of the mechanical gas valve to predefined steps.
In an implementation, the primary controller 302 sends a digital voltage signal, such as a "High" signal or "Low" signal, to one of the switching devices, say the switching device 312, and a pulse width modulated (PWM) duty cycle signal to the other switching device, i.e., the switching device 310. Based on the signals received, the switching devices 310 and 312 control magnetization of the coil 314, which consequently manipulates a position of the mechanical gas valve.
Figure 4 shows a detailed block representation of the electronic control system 200 of Figure 2. In an embodiment, the electronic control system 200 includes the IFC control unit 202 and the MGVC unit 208. In the IFC unit 202, a common power supply 402 is coupled to a gas valve relay 406. The gas valve relay 406 is switched when there is a call for heat. In an embodiment, the common power supply 402 provides a 24VAC power supply to the gas valve relay 406 through contacts of the gas valve relay 406. In addition, the IFC unit 202 may include a PWM generation unit 408, which generates a PWM duty cycle signal. The PWM generation unit may include components such as a transistor or a microprocessor capable of providing a PWM duty cycle signal. The IFC unit 202 is electronically coupled to the MGVC unit 208 through wires wl and w2 for supplying the 24VAC signal and the PWM duty cycle signal respectively. In addition, a common wire Wen is provided, which powers a power supply unit 410 of the MGVC unit 208.
The 24 VAC supply 402 powers the power supply unit 410 of the MGVC unit 208 through the gas valve relay 406. Further, the power supply unit 410 is

coupled to a dedicated power supply 416, which powers a primary controller 414, such as a microcontroller, of the MGVC unit 208. The primary controller 414, in addition to receiving the 24VAC signal through the gas valve relay 406, also receives the PWM duty cycle signal from PWM generation unit 408 over wirew2.
Apart from receiving the 24VAC signal and the PWM duty cycle signal, the primary controller 414 also receives other input signals, for example, input from a gas selection unit 418, which could suggest an alternative fuel source and /or inputs from a first and a second gas valve feedback units 420 and 422, which could be photo-interrupters used for determining current position of the two-stage gas valve. The first and second feedback units 420 and 422 may provide analog or digital signals to indicate the current position of the mechanical gas valve.
The primary controller 414 processes all the inputs to provide output signals for regulating power supplied to a coil 424. In an embodiment, the coil 424 is coupled to the primary controller 414 via two voltage-controlled switching devices 426 and 428, which may be field-effect transistors (FETs) or similar devices.
The primary controller 414 provides a digital voltage signal, such as a "High" signal or "Low" signal, to one of the switching devices, say the switching device 426, and a pulse width modulated (PWM) duty cycle signal to the other switching device, which is the switching device 428. Based on the signals received, the switching devices 426 and 428 control magnetization of the coil 424, which consequently impacts a current position of the two-stage gas valve so to control the gas flow through the gas valve to the gas-fired appliance.
Figure 5 shows representations of the 24VAC signal and the PWM duty cycle signal provided to the MGVC unit 208. The IFC unit 202 as disclosed in the present disclosure can be made compatible to the existing MGVC unit 104

without much design alterations. For example, in the electronic control unit 200, the IFC unit 202 is provided with a half-bridge rectifier, whereas the MGVC unit 104 uses a full wave rectifier. Due to this, GROUND reference points for the IFC unit 202 and the MGVC unit 104 are different. In such a case, when TH is positive with respect to TR, a negative side of the full wave rectifier is only a diode drop above TR. Since the GROUND of the IFC unit 202 is TR and the GROUND of the mechanical valve is only diode drop above TR, the two GROUNDS do not have much difference and therefore PWM duty cycle can be transmitted during this state. On the other hand, when TH is negative with respect to TR, then the two GROUNDS have way different potentials - the GROUND of the mechanical valve being way positive. During this period, the PWM duty cycle signal cannot be transmitted (the blank portion shown in Fig. 5b). In this state, the MGVC unit 104 may interpret the 24VAC signal being received from the conventional control unit 102, and operates accordingly, i.e., through the one or more relays provided in the consolidated relay unit 105.
In another scenario, one may implement an optoisolator to isolate the PWM duty cycle signal at a gas valve side of the MGVC unit 104 because in the MGVC unit 104, a GROUND of the controlling device 112 is at a different potential than a GROUND of the power supply to the coil 124.
TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The electronic control unit, in accordance with the present disclosure described herein above, has several technical advantages including but not limited to the realization of:
• Instead of having two or more relays to control an operation of the electronic operated valve, only one relay is used. Thus, one can save on additional relay cost and circuitry supporting the same.

• The circuitry to transfer and receive the PWM duty cycle signal costs way less than the relay cost.
• With the inclusion of PWM duty cycle signal, a double check for safety is provided before the mechanical gas valve is actually turned ON. The MGCV unit 208 will not open the mechanical valve until it detects a proper PWM duty cycle signal, even so when the 24VAC signal is being continuously detected. Because of such an arrangement, unwanted gas valve operation can be avoided.
• The operation of the IFC unit 202 can be upgraded up to multiple (modulating) stages by providing a different duty cycle signal without adding any cost to the electronic control unit.
• Further, one may add diagnostics circuitry to the MGCV unit 208 to display different error conditions.
• The present electronic control unit 200 can be made compatible for traditional IFC units.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge

in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

We claim:
1. An electronic control unit for controlling an electronic controlled
multistage gas valve (MGV) for adjusting gas flow to a gas fired appliance, the
electronic control unit comprises:
an integrated furnace control (IFC) unit;
a multistage gas valve control (MGVC) unit electronically coupled to said IFC unit; and
a coil electronically coupled to said MGVC unit, wherein the IFC unit, over a first communication line, provides at least one power supply signal, and over a second communication line, provides at least one pulse width modulated (PWM) duty cycle signal to said MGVC unit for controlling at least one of energizing and de-energizing of said coil, wherein the electronic controlled MGV is adapted to move in response to a magnetic field generated by said coil.
2. The electronic control unit as claimed in claim 1, wherein said IFC unit and said MGVC unit are powered through a common power supply.
3. The electronic control unit as claimed in claim 2, wherein said common power supply supplies a 24VAC.
4. The electronic control unit as claimed in claim 1, wherein the IFC unit comprises at least one relay and at least one PWM generation unit.
5. The electronic control unit as claimed in claim 4, wherein said at least one PWM generation unit comprises a transistor.

6. The electronic control unit as claimed in claim 4, wherein said at least one PWM generation unit comprises a microcontroller.
7. The electronic control unit as claimed in claim 4, wherein said at least one relay is coupled to said common power supply via a half-bridge rectifier.
8. The electronic control unit as claimed in claim 1, wherein said MGVC unit comprises at least one opto-coupling device for isolating said PWM duty cycle signal received from the IFC unit.
9. The electronic control unit as claimed in claim 1, wherein said MGVC unit comprises a primary controller that is configured to receive and process said PWM duty cycle signal and said power supply signal from the IFC unit.
10. The electronic control unit as claimed in claim 1, wherein said primary controller is a microcontroller.
11. The electronic control unit as claimed in claim 1, wherein said coil is coupled to the MGVC unit through one or more field effect transistors.
12. The electronic control unit as claimed in claim 1, wherein said coil comprises at least one coil of a stepper motor that is configured to move the electronic controlled MGV based on an input to said coil.

13. A method of controlling an operation of an electronic controlled
multistage gas valve of a gas fired appliance, the method comprising the steps
of:
detecting the presence of a power supply signal from an integrated furnace control unit;
detecting the presence of a pulse width modulated duty (PWM) cycle signal from said integrated furnace control unit; and
at least one of energizing and de-energizing a coil of a MGVC unit based on said detecting of the presence of said power supply signal and said PWM duty cycle signal.
14. The method as claimed in claim 11 further comprises isolating said PWM
duty cycle signal following detecting the presence of the PWM duty cycle
signal.