Patent Publication Number: US-10309906-B2

Title: Low-powered system for driving a fuel control mechanism

Description:
This is a continuation application of co-pending U.S. patent application Ser. No. 15/707,765, filed Sep. 18, 2017, and entitled “A LOW-POWERED SYSTEM FOR DRIVING A FUEL CONTROL MECHANISM”, which is a continuation of co-pending U.S. patent application Ser. No. 15/676,691, filed Aug. 14, 2017, and entitled “A LOW-POWERED SYSTEM FOR DRIVING A FUEL CONTROL MECHANISM”, which is a continuation application of U.S. patent application Ser. No. 14/042,269, filed Sep. 30, 2013, and entitled “A LOW-POWERED SYSTEM FOR DRIVING A FUEL CONTROL MECHANISM” now U.S. Pat. No. 9,752,990, issued Sep. 5, 2017, all of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure pertains to combustion control devices and particularly to low power combustion control devices. More particularly, the disclosure pertains to safe low power combustion control devices. 
     SUMMARY 
     The disclosure reveals a low-powered system. The system may have a fuel control mechanism pick circuit which has an energy storage mechanism for providing a large amount of current for a short time to a fuel control mechanism drive. A safety switch may control whether current can flow to the fuel control mechanism drive to operate a corresponding fuel control mechanism for controlling fuel to a pilot light or a heating element. The pilot light or heating element may provide heat to a thermoelectric source that generates electrical power from the heat. The power may go to a DC-to-DC converter and voltage clamp for providing a voltage source to a microcontroller and other circuits of the system. The safety switch may receive a special signal to enable a flow of current from the storage mechanism to the fuel control mechanism drive. The pick circuit may prevent a reverse flow of current from the storage mechanism to the thermoelectric source that could harm the thermoelectric source. The microcontroller may provide an available low magnitude flow of current to charge up the storage mechanism; however, such current is not necessarily sufficient for the fuel control mechanism drive. The microcontroller may also provide the special signal to the safety switch to enable a sufficient flow of current from the storage mechanism to the fuel control mechanism drive. The fuel control mechanism may control fuel to the pilot light and/or heating element of a water heater, stove, furnace, and other appliances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a diagram of an example illustrative fuel control system; 
         FIG. 2  is a diagram of traces of amplitudes of various components versus time for the control system; 
         FIG. 3  is a diagram of a power input protection module; 
         FIG. 4  is a diagram of a pick circuit; 
         FIG. 5  is a diagram of a safety switch; 
         FIGS. 6 and 7  are diagrams of alternative safety switches; 
         FIG. 8  is a diagram of a pilot valve drive circuit; 
         FIG. 9  is a diagram of a main valve drive circuit; 
         FIG. 10  is a diagram of a DC-to-DC converter circuit; 
         FIG. 11  is a diagram of a voltage clamping circuit; 
         FIG. 12  is a diagram of a microcontroller; 
         FIG. 13  is a diagram of circuitry for a communication port for the system; 
         FIG. 14  is a diagram of circuitry for a temperature sensor and interface; 
         FIG. 15  is a diagram of circuitry for a flammable vapor sensor; 
         FIG. 16  is a diagram of circuitry for a door sensor; and 
         FIG. 17  is a diagram of circuitry for a light emitting diode indicator. 
     
    
    
     DESCRIPTION 
     The present system and approach may incorporate one or more processors, computers, controllers, user interfaces, wireless and/or wire connections, and/or the like, in an implementation described and/or shown herein. 
     This description may provide one or more illustrative and specific examples or ways of implementing the present system and approach. There may be numerous other examples or ways of implementing the system and approach. 
     In a flame powered combustion system, a microcontroller may actively manage the flame generated power to run the valves and the electronics. Active management itself may take some power, and the system cost may be higher with an actively controlled DC-to-DC converter. Thus, an actively controlled DC-to-DC converter may not necessarily be used. The microcontroller may be kept in sleep mode as much as possible to reduce power consumption. A free-running DC-to-DC converter may be improved for high efficiency, and be structured to take limited power from a source. 
     The transformer used in the free-running DC-to-DC converter may be designed so that at the critical input voltage level (closed-circuit input voltage of about 155 mV). The DC-to-DC converter may take just enough power to keep the microcontroller running while the pilot and main valves can be held in. This approach may be referred to “built-in optimized power sharing”. 
     The active power management procedure may be minimal. Since the microcontroller does not necessarily need to generate a pulse wave modulated (PWM) signal, the microcontroller may stay in a deep sleep mode instead of idle mode whenever not in active mode, thus consuming less power. A valve picking circuit and safety switch may be designed to use a small amount of energy for valve picking. Flame powered combustion controls may run with a power source generated from pilot flame. The output power from the power source may be very limited. 
     In a flame powered water heater control, a valve picking circuit may be used to store energy for valve picking, and a safety switch may be used to safe guard against a possible microcontroller malfunction. 
     A valve-picking circuit may be designed to improve the energy efficiency during valve picking time. A switch may be added between the power source and the safety switch, so that the valve picking circuit can apply full voltage stored on a capacitor to the valve during valve picking time. With the added switch, the efficiency may be about doubled in the valve picking process. 
     An N-channel MOSFET may be used for the safety switch. A PNP BJT may be added in the gate drive for the MOSFET. The drive signal might only be produced when the controller is driving an I/O pin actively. 
     A fail-safe flame powered combustion control valve may be noted. Combustion controls should be designed to be fail-safe, which may often require additional components or software tests to ensure that a product is fully functional during startup and operation. 
     An electronic pilot valve control may employ redundant transistors to operate the valve coils, and require a specific dynamic drive of the circuit (from the microcontroller) to hold the valve or valves open (i.e., flowing gas). 
     The present approach may add additional protection for the microcontroller pin toggling failure modes. The approach may do so in a low-cost manner requiring very few parts. 
     The present circuit may first use two I/O pins to charge a capacitor. Once the capacitor is properly charged, then the charge on the capacitor may keep a bipolar junction transistor forward biased to turn on a MOSFET that serves as a safety switch (i.e., redundant valve drive). If the microcontroller fails such that virtually all of its I/O pins are toggling in the same manner, the capacitor is not necessarily charged and the safety switch would remain in the OFF state. 
       FIG. 4  is a diagram of a pick circuit  14 . A transistor  37  may be noted. During valve pick time, transistor  37  may be off, preventing current flow back to flame power input  71 . Capacitor  32  may be charged to 2.2 volts or higher before picking a valve. 3.4 volts may be needed in other designs. 
     When picking a valve, transistor  36 , transistor  38  and transistor  52  or  53  may be turned on. Current may flow from capacitor  32  to the respective valve (connected at terminal  73  and/or terminal  74 ). A voltage applied to the valve is not necessarily restricted to a certain level. 
     To turn on transistor  38 , microcontroller  20  should toggle at pin  41  at a frequency higher than a few hundred Hz with a high duty cycle. This may produce a voltage signal to turn on transistor  43  for most of the time. Parasitic gate capacitance of transistor  38  may keep transistor  38  on during a short low time at pin  41 . 
     Safety switch  15  may be safe as high input voltage can not necessarily turn the safety switch on. Safety switch  15  may be safe as it is in a path of picking current. The present circuit may have low cost and a low component count. For instance, there may be no need for a P-channel MOSFET on a printed circuit board of switch  15 , no need of an interlock switch with DC-to-DC converter  12 , no more than one stage of a charge pump, and no more dedicated turn-off circuit. 
     There may be good power management during pick time as the DC-to-DC converter  12  may be active. The present circuit may be turned on instantly. Since transistor  37  may be incorporated, safety switch  15  does not necessarily need be turned off quickly. When toggling at pin  41  stops, safety switch  51  may be off in a few hundreds of a micro-second. 
     Since safety switch  15  may be turned on instantly, and the transition from on-state to off-state may be quickly detected, the health of safety switch  15  may be checked almost any time (i.e., during start up, and run or idle time) and as frequently as necessary, thus improving safety features of control. 
     A safety switch transistor  38  may be an N-channel MOSFET. If pin  41  is toggled with a high-duty waveform and pin  42  has an output high state, capacitor  44  may be charged and then transistor  43  may be turned on. When transistor  43  is in an ON state, transistor  38  may also be turned on. However, if pins  41  and  42  are toggled at the same frequency and phase, then capacitor  44  will not necessarily be charged, and transistor  43  and safety switch transistor  38  will remain in an OFF state. 
       FIG. 1  is a diagram of an example illustrative control system  10 . Power may be available to a power input protection module  11 . An output from module  11  may go to a DC-to-DC converter  12 , and an output from converter  12  may go to a voltage clamping circuit  13 . Circuit  13  may provide a component supply voltage (Vcc) to a microcontroller  20 . The voltage may also be provided to other electronic components of system  10 . 
     Another output from module  11  may be provided to a pick circuit  14 . Circuit  14  may be connected to a safety switch  15  and microcontroller  20 . 
       FIG. 8  is a diagram of a pilot valve drive circuit.  FIG. 9  is a diagram of a main valve drive circuit. Safety switch  15  may be connected to pilot valve drive  16 , main valve drive  17 , and microcontroller  20 . Pilot valve drive  16  and main valve drive  17  may also be connected to microcontroller  20 . 
     A communication port  18  and an indicator circuit may be connected to microcontroller  20 . A temperature sensor and knob interface  21 , a flammable vapor sensor  22 , and a door sensor  23  may be connected to microcontroller  20 . 
       FIG. 2  is a diagram of traces of amplitudes of signals of various components versus time for system  10 . Trace  75  shows a pilot valve being opened by a user holding a knob down for a brief period of time and the pilot being lit at a time line  77 . A voltage tp (Vtp) may begin at time line  77  to gain and achieve a certain amplitude as shown by a trace  76 . When Vtp reaches about 150 millivolts at a time line  78 , DC-to-DC converter  12  may start producing output current to charge capacitor  63 . As a charge of a capacitor  63  reaches about 1.8 volts, at a time line  79 , microcontroller  20  may enter an active mode. In one minute or so, the Vtp  76  trace may reach 700 millivolts. When the trace  65  of the charge on capacitor  63  reaches about 2.6 volts at a time line  81 , then P 21  of input  33  starts to change state between an output high and a high-impedance input. When it is in output high state, current flows from microcontroller to charge up capacitor  32 . When it is in input state, capacitor  32  holds its charge. Trace  65  may have an up and flat or stepped affect superimposed on its increasing magnitude. Trace  33  may continue with the interchanging states of output high and high-impedance input to a time line  82  where a trace  32  of Vcap indicates that pick circuit  14  is ready to pick a valve. Trace  33  may remain at a high after time line  82 . 
     At time line  83 , transistor  38  may turn on and thus begin to pick a valve such as the pilot valve, where a transistor  52  turns on as indicated by trace  52  to energize the coil of the pilot valve to keep it open. A transistor  37  may turn on for about 40 milliseconds at time line  83  and then turn off for about 30 milliseconds at a time line  84 . As transistor  37  turns off at time line  84 , transistor  36  may turn on for about 30 milliseconds and then turn off at a time line  85  when transistor  37  turns back on. At timeline  83 , a pick current may begin to build up. After transistor  36  is turned on at time line  84  the current will increase quickly and be sufficient, such as 35 milliamps, to pick a valve as indicated by trace  86 . The current may increase to at least about 70 milliamps as indicated by amplitude 87 to guarantee a pilot valve pick. The magnitude of the pick current may be greater than 70 milliamps as indicated at time line  85 . Shortly after time line  85 , the valve picking may be complete and the current flowing to the valve coil may return to a lower, “hold” value. 
       FIG. 3  is a diagram of power input protection module  11 . A supply current may come from a thermopile  25  at input  71  relative to a ground or reference voltage  72 , and pass through a thin trace  26  on a printed circuit board. Thin trace  26  may act as a fuse in case of excessive input voltages to module  11 , or to limit current in an event that a battery on DC power supply is connected. Diode  27  may offer protection in case an input voltage with a wrong polarity is connected to module  11 . Diode  27  may prevent possible damage to circuits connected to module  11  by clamping the input voltage to a safe level. Capacitor  28  may prevent ESD from damaging MOSFETs. Capacitor  29  may be a tank capacitor that helps improve the efficiency of DC-to-DC converter  12 . 
       FIG. 4  is a diagram of pick circuit  14 . Line  31  of circuit  14  may be connected to line  31  of module  11 . Pick circuit or valve picking circuit  14  may have a storage capacitor  32 . An I/O pin  33  may be connected to microcontroller  20  to control charging of capacitor  32 . Energy for picking a valve may be stored in capacitor  32  which is charged to a voltage  34  via a digital signal having current limited by a resistor  35 . Charging capacitor  32  may be sequenced such that voltage  34  stays sufficiently high. After capacitor  32  charged above 2.2 volts, the energy stored on capacitor  32  may be enough for picking a valve. When a valve is picked, a transistor  36  may be turned on to allow current flow from capacitor  32  to a valve drive, and a transistor  37  may be turned off to prevent current flowing back to the thermopile input. 
       FIG. 5  is a diagram of a safety switch  15 . A transistor  38  of safety switch  15  may be turned on to pick a valve. A picking sequence may differ for a pilot valve and a main valve. Transistor  38  may be an N-channel MOSFET and may act as the safety switch. Transistor  38  may be connected by a line  39  to pick circuit  14 . Transistor  38  may be controlled by I/O pins  41  and  42  and an interface circuit having a transistor  43 , a capacitor  44 , a diode  45 , a resistor  46  and a resistor  47 . Microcontroller  20  may drive the interface circuit by toggling a digital output at pin  41  at a frequency and duty cycle such that pin  41  low time is short (such as shorter than 20 micro-second) and keeping pin  42  at a high state. The toggling signal may generate a high enough voltage to turn on transistor  43 . When transistor  43  is on, then a positive voltage may be applied to the gate of transistor  38  and turn on transistor  38 . If a signal on pin  41  stops toggling, or if the signal on pin  42  toggles together with the signal on pin  41  at the same frequency and phase, then transistor  43  may stay in an off state and transistor  38  is not driven. A resistor  48  may bleed the gate of transistor  38  to turn off transistor  38  if transistor  43  is not in an on state. Resistor  47  may limit the base current of transistor  43 , and resistor  46  may prevent transistor  43  from being turned on by leakage. 
     The working conditions of safety switch  15  may be checked by the microcontroller  20  at least once per heating cycle of an associated heating system by reading a voltage across the valve coils. If safety switch  15  is found to be inoperable at any time, microcontroller  20  may take appropriate action to handle a fault condition. 
       FIGS. 6 and 7  are diagrams of safety switches  15   a  and  15   b , respectively, which may be used as alternative to safety switch  15  of  FIG. 5 . Unmarked components may be added with a variation in circuit detail relative to that in  FIG. 5 . In  FIG. 7 , a waveform of a duty cycle may toggle a pin input. 
       FIGS. 8 and 9  are diagrams of a pilot valve drive  16  and main valve drive  17 . Working conditions of drives  16  and  17  may be checked by microcontroller  20  at least once per heating cycle by reading the voltage across each of the pilot and main valve coils. If a transistor is found to be inoperable at any time, microcontroller  20  may take the appropriate action to handle the fault condition. 
     Pilot drive  16  and main drive  17  may be in parallel with each other relative to a line  51 , but in series with safety switch  15  on a line  49 . The drivers, transistors  52  and  53 , may be N-type FETs. To allow current to one of the valve coils, microcontroller  20  may set the gate of the appropriate transistor to high. Diodes  54  and  55  may provide a return current path to the valve coils when transistors  52  and  53 , respectively, are turned off. Diodes  54  and  55  may also increase a level of ESD protection for the electronics. Resistors  56  and  57  of valve drives  16  and  17 , respectively, may protect an ADC input (valve status sense) of microcontroller  20 . Voltages on lines  73  and  74  may be combined to a single voltage for sensing by microcontroller  20 . 
       FIG. 10  is a diagram of DC-to-DC converter  12 , which may be a low voltage step-up converter that starts to convert an input voltage to a higher voltage when the input voltage is about 150 millivolts or higher. Converter  12  may boost the voltage to above 2.0 volts in order to start microcontroller  20 . Low-voltage DC-to-DC converter  12  may be a free-running oscillator having a transformer  58 , a transistor  59 , a resistor  61 , and a capacitor  62 . Capacitor  62  may provide a positive feedback to a gate of transistor  59  driving transistor  59  on and off with oscillations. Capacitor  62  may also provide a DC shift needed for optimum performance of the free-running oscillator. Toggling transistor  59  may cause an energy build-up in transformer  58  and cause the energy to be dumped from the secondary winding of transformer  58  to a storage capacitor  63  through a diode  64 . Transistor  59  may be an N-channel depletion J-FET that conducts at zero Vgs. This characteristic may enable a start-up at very low input voltages. Resistor  61  may pull the gate of transistor  59  to zero voltage when control is not supplied, and thus get the circuit of converter  12  ready for a start-up. 
     Some example and illustrative specifications of converter  12  may be noted. Converter  12  may start a conversion with an input voltage equal to or greater than 150 millivolts. An output voltage should be greater than 2.0 volts after the input voltage is applied. With an input voltage of equal to or greater than 260 millivolts, converter  12  output voltage should be greater than 2.0 volts with microcontroller  20  functioning normally and the pilot valve open. With an input voltage equal to or greater than 330 millivolts, converter  12  output voltage should be higher than 2.0 volts with microcontroller  20  functioning normally and both the pilot and main valves open. 
       FIG. 11  is a diagram of a voltage clamping circuit  13 . Circuit  13  may have a line  65  connected to line  65  of converter  12 . Line  65  may be regarded as a Vcc line. A zener diode  66 , a transistor  67  and a resistor  68  may form the voltage clamping circuit. Circuit  13  may clamp Vcc to below 4.1 volts when a very strong thermopile (1.0 volt open circuit voltage) is connected to the board. The maximum voltage that microcontroller  20  can tolerate may be 4.1 volts. 
       FIG. 12  is a diagram of microcontroller  20 . Terminal  1  of controller may be connected to a Vcc line  65  of voltage clamping circuit  13 . Microcontroller  20  may an MSP430G2533 (TI). Pin numbers (i.e., I/O pins, e.g., P 20 ) may be connected to lines of various components of system  10  as indicated by one or more lines labeled with a corresponding pin number (e.g., P 20 ). 
       FIG. 13  is a diagram of circuitry for a communication port  18  for system  10 .  FIG. 14  is a diagram of circuitry for a temperature sensor and interface  21 .  FIG. 15  is a diagram of circuitry for a flammable vapor sensor  22 .  FIG. 16  is a diagram of circuitry for a door sensor  23 .  FIG. 17  is a diagram of circuitry for a two-color light emitting diode (LED) indicator  19 . 
     To recap, a control circuit may incorporate a thermally activated power source, a valve pick circuit connected to the thermally activated power source, a safety switch circuit connected to the valve pick circuit, and a valve drive circuit connected to the safety switch circuit. The valve pick circuit may incorporate a charge storage device, a first switch for preventing current flow back to the thermally activated power source, and a second switch for allowing current to flow from the charge storage device to the safety switch circuit. The safety switch circuit may require not perfectly in phase input signals to turn on a third switch for allowing the current to flow from the second switch to the valve drive circuit. 
     The charge storage device may be charged to at least a first voltage before a valve pick time of the valve pick circuit. The first switch may be off during the valve pick time of the valve pick circuit. The third switch may be connected to the first and second switches and the charge storage device through the second switch. A fourth switch may be for receiving the not perfectly in-phase input signals to turn on the third switch. 
     The valve drive circuit may incorporate a fifth switch connected to the third switch, and a first terminal connected to the fifth switch, for a connection to a first valve. When the charge storage device is charged to at least the first voltage, the valve pick time begins and the second, third and fifth switches are turned on, current may flow from the charge storage device via the first connection to a first valve. 
     A magnitude of the current to the first valve may range from one to three times a minimum magnitude of current needed to operate the first valve. 
     The first, second, third, fourth and fifth switches may be transistors. The charge storage device may be a capacitor. 
     The first, third and fifth transistors may be N-channel field effect transistors (FETs). The second transistor may be an NPN bipolar transistor. The fourth transistor may be a PNP bipolar transistor. 
     The control circuit may further incorporate a microcontroller. The microcontroller may provide the not perfectly in phase input signals to the fourth switch to turn on the third switch. 
     The control circuit may further incorporate a single DC-to-DC converter connected to the thermally activated power source. The control circuit may further incorporate a voltage clamping circuit connected to an output of the single DC-to-DC converter and to an input of the microcontroller. 
     The thermally activated power source may incorporate a thermopile device. The thermopile device may incorporate two or more serially connected thermocouple devices. The microcontroller may be an ultra-low-power microcontroller. 
     An approach for controlling one or more valves, may incorporate applying thermal energy to a thermoelectric device, generating a first voltage potential from the thermal energy using the thermoelectric device, converting the first voltage potential to a second voltage potential using a power converter, operating a controller using the second voltage potential, storing a charge on a capacitor using a third voltage potential from the controller, permitting, via signals from the controller to a safety switch, the charge on the capacitor to flow as a current through the safety switch to a valve drive circuit, preventing the charge on the capacitor to flow to the thermoelectric device, and permitting the current to the valve drive circuit to have a magnitude that ranges from one to three times a minimum magnitude of current needed to operate a valve connected to the valve drive circuit. 
     The signals from the controller to the safety switch may not necessarily be perfectly in phase for permitting the charge on the capacitor to flow as a current through the safety to the valve drive circuit. 
     The approach for controlling one or more valves, may further incorporate operating an igniter for a heating element, and manually holding the valve, connected to the valve drive circuit, open for providing fuel to the heating element for obtaining a flame from the heating element. 
     The valve may be tension-loaded to close the valve. The flame may heat up the thermoelectric device to generate the first voltage potential. The valve may be held open until an occurrence of the minimum magnitude of current needed to operate the valve connected to the valve drive circuit. The heating element may be a pilot light. 
     A flame control system may incorporate a power source, a reverse current protection circuit connected to the power source, an energy storage circuit connected to the reverse current protection circuit, a safety switch connected to the energy storage circuit, and a drive circuit, for a fluid control mechanism, connected to the safety switch. Providing a certain electronic signal to the safety switch may permit current to flow from the energy storage circuit through the safety switch to the drive circuit for the fluid control mechanism. 
     The flame control system may further incorporate a microcontroller connected to the energy storage circuit and the safety switch. The microcontroller may provide the certain electronic signal to the safety switch for permitting current to flow from the energy storage circuit through the safety switch to the drive circuit for the fluid control mechanism. 
     The certain electronic signal may incorporate not perfectly in phase input signals. 
     The flame control system may further incorporate a microcontroller connected to the energy storage circuit, a single DC-to-DC converter connected to the power source, and a clamping circuit connected to the DC-to-DC converter and the microcontroller. 
     The power source may incorporate a thermoelectric generator. The fluid control mechanism may incorporate a fuel valve connected to a flame generator. The flame generator, upon receipt of fuel and ignition, may heat the thermoelectric generator to provide electrical power. The energy storage circuit may incorporate a capacitor. 
     A patent document that may be relevant is U.S. Pat. No. 6,959,876, issued Nov. 1, 2005, and entitled “Method and Apparatus for Safety Switch”. U.S. Pat. No. 6,959,876, issued Nov. 1, 2005, is hereby incorporated by reference. 
     In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
     Although the present system and/or approach has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the related art to include all such variations and modifications.