Patent Abstract:
A device for increasing an extreme low voltage from a heat to electrical voltage thermopile is shown. The device has an oscillator including two MOSFET transistors coupled to a transformer having four bifilar windings wound on a core having a high permeability. The two transistors operate alternately to generate an intermediate voltage which is increased in magnitude by a voltage doubling and rectifying circuit to obtain the substantially constant operating output voltage. The output voltage is further maintain constant by a current control cirucit including an adjustable potentiometer adjustable to vary the current.

Full Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to an electronic device for increasing an extremely low DC voltage to a voltage suitable for operating other electronic devices. More particularly it relates to an electronic device usable for increasing the extremely low voltage generated by a transducer which converts heat energy of the flame of a pilot light of a gas equipment such as a gas fireplace and the like to an electrical power suitable for operating the electrical control of the gas supply to the gas equipment.  
         BACKGROUND OF THE INVENTION  
         [0002]    The gas supply to the main burner of a gas equipment is controlled by an electrically operated solenoid valve. Such valve is commonly operated with a voltage supply of 6 to 9 volts DC in order to reduce the potential fire hazard for operating it in the explosive gas environment if it is operated with a higher voltage. The solenoid valve may be actuated with a manual switch or an electronic remote control device. The operating electrical power of the electronic remote control device, also is commonly in the range of 6 to 9 volts supplied by either a battery or by power obtained through a step-down voltage supply from an AC current source. Wiring of an AC source to the receiver of the remote control device is often difficult to make due to the installation location of the gas equipment particularly when the gas equipment is situated in a building having a finished wall construction. Battery may be used to provide the electrical power for operating the remote control receiver for ease in installation. However, the drawback of a battery supply is that the battery requires replacement from time to time as its power depletes, especially when its power would deplete in a much faster rate in a hot environment during the operation of the gas equipment. Moreover, users of the gas equipment are unwilling to perform such task of replacing the battery due to either the fear of might accidentally cause a fire hazard in the explosive gas environment or being unfamiliar with the gas equipment. More often the user would neglect to replace the battery so that the gas equipment becomes inherently inoperative.  
         SUMMARY OF THE INVENTION  
         [0003]    It is the principal object of the present invention to provide an electronic device operable for increasing extremely low DC voltage to a voltage suitable for operating electronic devices.  
           [0004]    It is an object of the present invention to provide a power source for operating the remote control switch of the solenoid valve a gas equipment by utilizing the heat energy of its pilot light.  
           [0005]    It is another object of the present invention to provide a conversion device which is capable of converting heat energy of the pilot light burner of a gas equipment to electrical power in the magnitude suitable for operating electronic control devices of the gas equipment.  
           [0006]    It is another object of the present invention to provide an electronic device for converting heat energy to a substantially constant electrical power source for operating the gas supply control solenoid valve of a gas equipment.  
           [0007]    It is yet another object of the present invention to provide a heat to electrical power supply conversion device which is simple in construction and easy to incorporate in a natural gas equipment installation.  
           [0008]    These and other objects are achieved by my invention. The structure and some of its&#39; various modes of operation may be understood by reference to the drawings taken in conjunction with the detailed description.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a schematic circuit diagram of the electrical circuit of the device according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]    With reference to the drawing, the electronic device  10  of the present invention has an oscillation circuit having two MOSFET transistors  11  and  12  connected in tandem and coupled with a multi-winding transformer  13  which has four bifilar windings  14 ,  15 ,  16  and  17 . The four bifilar windings are wound on a core having a very high permeability so as to provide a good coupling between the windings. The numbers of windings in windings  14  and  15  are equal to one another and the numbers of windings of windings  16  and  17  are equal to one another and is much higher than those of windings  14  and  15 . The start of the winding  14  is connected to the end of the winding  16  at a first connection terminal  18 , and the end of the winding  14  is connected to the start of the winding  15  at a second connection terminal  19 , whereas the end of the winding  15  is connected to the start of the winding  17  at a third connection terminal  20 . The start of the windings  14 ,  15 ,  16  and  17  is indicated in the drawing with a dot. The source terminals  18  and  19  for the transistors  11  and  12  respectively are connected to one another. The source terminals  21  and  22  of the transistors  11  and  12  respectively are connected to a common terminal  23 . The drain terminal  24  of the transistor  11  is connected to the first connection terminal  18  and the drain terminal  25  of transistor  12  is connected to the connection terminal  20 . The gate terminal  26  of the transistor  11  is connected to the end of winding  17  through a resistor  27  while the gate terminal  28  is connected to the start of the winding  16  through a resistor  29  similar to resistor  27 . The head of transformer winding  16  is connected to the anode of a first Schottky diode  30  and the cathode of a second Schottky diode  31  through a capacitor  32 . Similarly, the end of transformer winding  17  is connected to the anode of a third Schottky diode  33  and the cathode of a four Schottky diode  34  through a capacitor  35 . The parallel diode circuit provides a full wave rectification to the voltage outputted from the oscillation circuit.  
         [0011]    The above oscillation circuit is operable by an extremely low DC voltage as low as about 0.15 volt which is too low to operate common transistors. The extremely low voltage is inputted to connection terminal  19  and common terminal  23 . Due to the extremely low voltage, the oscillator circuit initially would not be actuated by the low voltage; in order to initiate the operation of the oscillation circuit, a short circuit operation is made by a momentary switch  38  connected across the source terminal  21  and drain terminal  24  of the transistor  11 . When the momentary switch  38  is closed and then opened, the output first voltage across the drain to common terminals of the transistor  11  will be at least double of that of the extremely low input DC voltage; and this first voltage will induce a much higher first secondary voltage across the winding  16  by the transformer action due to the much higher number of windings of winding  16  relative to the winding  14 . This first secondary voltage will be applied to the gate terminal  28  through resistor  29  to present an increased voltage to turn on the transistor  12  so that the transistor  12  begins to conduct. The conduction of current through the transistor  12  will continue until the current saturates the core of the transformer  13  at which point the transistor  12  will turn off. The termination of conduction of the transistor  12  will generate a second secondary voltage across the winding  17  by the transformer action due the much higher number of windings of the winding  17  relative to the winding  15 . The second secondary voltage will be applied inherently to the transistor  11  to turn the later on. In this manner, the transistors  11  and  12  are turned on and off with one transistor turning on while the other transistor turning off, in a continuous cycle. The combination of diodes  30  and  31  and capacitor  32  forms a first doubling circuit to provide a voltage doubling function to the first secondary voltage across the winding  13 , while the combination of diodes  33  and  34  and capacitor  35  provides a second voltage doubling circuit to provide a voltage doubling function to the second secondary voltage across the winding  17 . The two doubling circuits also provide a full wave rectification to the combined first secondary voltage and second secondary voltage appearing at terminals  26  and  37 . This combined high voltage is further smoothed by the capacitor  38  connected across the terminals  26  and  37 . The high voltage has sufficient current and a high efficiency. It is also very economical to build as it does not require a special winding for the high voltage output. The feedback windings  16  and  17  are used in the dual purposes to provide a full load current.  
         [0012]    The smooth output voltage across the terminals  26  and  37  to a stabilization circuit including FET transistor  39  and a zener diode  40  connected in series across the output terminals. A potentiometer  41  is connected between the gate of transistor  39  and the anode of the zener diode  40 . The potentiometer  41  may be adjusted to vary the amount of current flowing through the drain terminal to the source terminal of the FET transistor  39  into the zener diode  40  while the output voltage is maintained substantially constant.  
         [0013]    It would be appreciated by those skilled in the art that alternatively P-channel MOSFET transistor may be used instead of the N-channel MOSFET transistor by changing the polarity and connection of the diodes and the junction FET transistor.  
         [0014]    The above circuit device is suitable for increasing the extra low DC voltage obtained from a thermopile heated by the pilot light flame of a gas equipment. Such extra low DC voltage is not suitable for operating the electrical control of the gas supply to the main burner of a gas equipment. With the device of the present invention, the extra low voltage is increased to the suitable voltage for operating the gas control solenoid valve and the remote control circuit of the gas supply to the main burner.  
         [0015]    While the preferred embodiment of the invention has been disclosed, it should be appreciated that the invention is susceptible of modification without departing from the scope of the following claims.

Technology Classification (CPC): 7