Abstract:
A power supply unit for use with thermostats or other like devices. The power supply unit may keep electromagnetic interference emissions and harmonics at a minimum. A unit may have enough power for triggering a switch at about a cross over point of a waveform of input power to the unit. Power for triggering may come from a storage source. Power for the storage source may be provided with power stealing which require switching transistors which can generate emissions. In-line thermostats using MOSFETS power steal may do the power steal during an ON state (triac, relay or silicon controlled rectifier activated). Gate signals to the transistors may be especially shaped to keep emissions from transistor switching at a minimum. All that may be needed, during an OFF state as a bypass, is a high voltage controllable switch. The need may be achieved using high voltage MOSFETS.

Description:
BACKGROUND 
       [0001]    The present disclosure pertains to thermostats and particularly to various kinds of power supply arrangements for thermostats. 
       SUMMARY 
       [0002]    The disclosure reveals a power supply unit for use with thermostats or other like devices. The power supply unit may keep electromagnetic interference emissions and harmonics at a minimum. A unit may have enough power for triggering a switch at about a cross over point of a waveform of input power to the unit. Power for triggering may come from a storage source. Power for the storage source may be provided with power stealing which require switching transistors which can generate emissions. In-line thermostats using MOSFETS power steal may do the power steal during an ON state (triac, relay or silicon controlled rectifier activated). Gate signals to the transistors may be especially shaped to keep emissions from transistor switching at a minimum. All that may be needed, during an OFF state as a bypass, is a high voltage controllable switch. The need may be achieved using high voltage MOSFETS. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0003]      FIG. 1   a  is a block diagram of a thermostat circuit; 
           [0004]      FIG. 1   b  is a diagram of a power supply unit having a layout divided into several areas incorporating an off state area, an always active area and an on state area; 
           [0005]      FIG. 2   a  is a diagram of a positive bypass switch; 
           [0006]      FIG. 2   b  is a diagram of a positive protect circuit connected to the positive bypass switch; 
           [0007]      FIG. 3   a  is a diagram of a negative bypass switch; 
           [0008]      FIG. 3   b  is a diagram of a negative protect circuit connected to the negative bypass switch; 
           [0009]      FIG. 4  is a diagram of a circuit showing power steal switching MOSFETs; 
           [0010]      FIG. 5  is a diagram of a circuit showing a large capacity capacitor; 
           [0011]      FIG. 6  is a diagram of a DC-DC converter or linear regulator circuit; 
           [0012]      FIG. 7  is a diagram of a half wave zero crossing detect circuit; 
           [0013]      FIG. 8   a  and  FIG. 8   b  are diagrams of a MOSFET gate signal shaping circuit; 
           [0014]      FIG. 9  is a diagram of a MOSFET reverse wave protection circuit; 
           [0015]      FIG. 10  is a diagram of an SCR gate triggering signal circuit; 
           [0016]      FIG. 11  is a diagram of an SCR circuit; and 
           [0017]      FIG. 12  is a diagram of a plug that may be used for various connections external to the power supply unit. 
       
    
    
     DESCRIPTION 
       [0018]    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. 
         [0019]    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. 
         [0020]    There may be a need for a new kind of bypass which is non-current limited, inexpensive, small space, power dissipation proportional to current consumption, audible noise free and electromagnetic interference compliant. 
         [0021]    Since in-line thermostats using MOSFETS (metal-oxide-semiconductor field-effect transistors) power steal may already do the power steal during the ON state (triac, relay or silicon controlled rectifier (SCR) activated). All that may be needed, during the OFF state as a bypass, is a high voltage controllable switch. This may be achieved using high voltage MOSFETS. 
         [0022]    The thermostats may relate to HVAC (heating, ventilation and air conditioning) systems. 
         [0023]    Using the same synchronization as for a MOSFET power steal, one may synchronize the MOSFET switch. For an energy hungry application, the peak current through the switch can became very high since the power steal is half wave only. So, a second switch with small modification to the synchronization circuit may be added to make a full wave switch and reduce harmonics. 
         [0024]    The present approach may be used with an in-line controller doing MOSFET power steal like the line volt thermostat. It may allow a circuit to be universal for virtually all thermostats, and that has characteristics such as being non-current limited, inexpensive, situated in a small space, having power dissipation proportional to current consumption, and being audible noise free and electromagnetic interference compliant. The present approach may use one or more switches in a power steal circuit for an in-line thermostat 
         [0025]      FIG. 1   a  is a block diagram of a thermostat circuit  71  discussed herein. An AC (alternating current) line voltage may be provided by power supply  72  on lines  73  and  74  to thermostat  71  and electric baseboard  75 . Line voltage on line  73  may go to a bypass switch  76  and triac, relay or SCR  77 . Circuit low voltage may go along line  78  to stealing circuit  79 . A connection may go from triac, relay or SCR  77  to a MOSFETs power steal along line  81 . Lines  78  and  81  may be connected by a line  83 . A load voltage may connect stealing circuit  79  and MOSFETs power steal along lines  84  and  85  via line  86  to electric baseboard  75 . Areas  91 ,  92  and  93  indicate off state, always active and on state, respectively. 
         [0026]      FIG. 1   b  is a diagram of a power supply unit  11  having a layout divided into three areas incorporating an off state area  12 , an always active area  13  and an on state area  14 . 
         [0027]    A positive bypass switch  15  in area  12  may have an input from a line  16  ( 2 ). Also in area  15  is a negative bypass switch  17 . Line  16  may go to negative bypass switch  17 . An AGND line  21  may be an input to switch  17 . 
         [0028]    Power steal switching MOSFETs  18  in area  13  may have an input from a line  19  ( 1 ) and be connected to an AGND (ground) line  21 . A line  22  may go from negative bypass switch to power steal switching MOSFETs  18 . 
         [0029]    An energy storage  23  in area  13  may receive an input of Vrect (stolen energy) on line  24  from positive bypass switch  15  and an RS 1 G input on line  24  from power steal switching MOSFETs  18 . An output Vrect on line  24  may go from energy storage  23  to a DC-DC (direct current) converter or linear regulator  25  of area  13 . An output Vcc (3Vdc) on a line  26  may go outside of unit  11  to a processor and circuits  27 . Vrect on line  24  may go to a backlight circuit  28  outside of unit  11 . Vrect on line  24  may also go to negative bypass switch  17 . 
         [0030]    A half wave ZC (zero crossing) detect  31  in area  13  may have an input connected to line  16  and an input connected to Vrect on line  24 . Detect  31  may output a D latch positive signal on a line  32 , a D latch negative signal on a line  33 , and a crossing signal on a line  34 . The signals on lines  32 ,  33  and  34  may go to a MOSFET gate signal shaping circuit  35  in area  13 . 
         [0031]    A MOSFET reverse wave protection circuit  36  in area  13  may have an input of Vrect on line  24  and of line  19  ( 1 ) of AC in. A protect signal on a line  37  may go from protection circuit  36  to shaping circuit  35 . A Vsync signal on a line  38  may go from shaping circuit  35  to positive bypass switch  15  and to negative bypass switch  17 . A Vg signal may be on a line  39  and may go to power steal switching MOSFETs  18 . 
         [0032]    An SCR gate triggering signal circuit  41  of area  14  may have inputs of Vrect on line  24 , line  16  ( 2 ) of AC in and a CPU (computer) drive signal on a line  42 . Circuit  41  may provide a gate signal Vgm+ on a line  43  and a gate signal Vgm− on a line  44  to an SCR circuit  45  of area  14 . Line  16  ( 2 ) of AC in may be an input to SCR circuit  45 . An AC out on a line  46  may be provided by circuit  45 . 
         [0033]      FIG. 2   a  is a diagram of positive bypass switch  15 . Switch  15  may be connected to a positive protect circuit  51  as shown in a diagram of  FIG. 2   b . A Vdp signal may go on a line  53  from switch  15  to circuit  51 . 
         [0034]      FIG. 3   a  is a diagram of negative bypass switch  17 . Switch  17  may be connected to a negative protect circuit  52  as shown in a diagram of  FIG. 3   b . A Vdn signal may go on a line  58  from switch  17  to circuit  52 . An over current terminal in circuit  51  may be connected via a line  57  with an over current terminal in circuit  52 . 
         [0035]      FIG. 4  is a diagram of circuit  18  showing power steal switching MOSFETs  61  and  62 .  FIG. 5  is a diagram of circuit  23  showing a large capacity (e.g., 820 microfarads) capacitor  63 .  FIG. 6  is a diagram of a DC-DC converter or linear regulator circuit  25 . 
         [0036]      FIG. 7  is a diagram of a half wave zero crossing detect circuit  31 .  FIG. 8   a  and  FIG. 8   b  are diagrams of MOSFET gate signal shaping circuit  35 . Lines  21 ,  24 ,  34 ,  37  and  65  connect the diagrams of  FIGS. 8   a  and  8   b  to show the whole circuit  35 .  FIG. 9  is a diagram of MOSFET reverse wave protection circuit  36 . 
         [0037]      FIG. 10  is a diagram of SCR gate triggering signal circuit  41 , which provides trigger signals Vgm+ and Vgm− on lines  43  and  44  to SCR circuit  45  shown in a diagram of  FIG. 11 . 
         [0038]      FIG. 12  is a diagram of a plug  66  that may be used for various connections external to unit  11 . 
         [0039]    To recap, an in-line thermostat power system may incorporate a bypass switch, a power stealing circuit connected to the bypass switch, an energy storage circuit connected to the power stealing circuit, an SCR interface circuit connected to the energy storage circuit, and an SCR circuit connected to the SCR interface circuit. The bypass switch may be a controllable switch for line voltage. 
         [0040]    The line voltage controllable switch may incorporate a positive bypass switch and a negative bypass switch. The positive bypass switch may incorporate one or more line voltage MOSFETs. The negative bypass switch may incorporate one or more line voltage MOSFETs. 
         [0041]    The positive bypass switch may incorporate a positive protect circuit. The negative bypass switch may incorporate a negative protect circuit. 
         [0042]    The system may further incorporate a half wave zero crossing detection circuit connected to the energy storage circuit, and a gate signal shaping circuit connected to the half wave zero crossing detection circuit, the bypass switch, and the power stealing circuit. The power stealing circuit may incorporate one or more switching MOSFETs. The gate signal shaping circuit may provide a gate signal that results in a soft transition of turning on and off of the one or more MOSFETs of the power stealing circuit. 
         [0043]    The SCR interface circuit may have a first input connected to an output of the energy storage circuit, a second input connectable to a line voltage, a third input connectable to a control signal source, and an output of gate signals. The SCR circuit may have a first input for gate signals from the SCR interface circuit, a second input connectable to a line voltage, and an output of a controlled line voltage. 
         [0044]    The system may further incorporate a thermostat having a temperature sensor, a temperature setting adjuster, and a processor connected to the temperature sensor and a temperature setting adjuster. The processor may incorporate the control signal source that provides a signal to the SCR interface circuit which in turn outputs the gate signals to the SCR circuit, with a goal to bring a temperature indication from the temperature sensor and a temperature setting of the temperature setting adjuster to a same value. 
         [0045]    The system may further incorporate a heater having terminals connected to a line voltage and an output of the SCR circuit. The temperature sensor may be situated in a space that contains the heater. The gate signals to the SCR may result in the output of the SCR circuit to control heat from the heater to achieve the goal to bring the temperature indication from the temperature sensor and the temperature setting of the temperature setting adjuster to a same value. 
         [0046]    A thermostatic power supply mechanism may incorporate a first terminal for connection of a power source; a bypass switch having an input connected to the first terminal; an SCR circuit having a first connection connected to the first terminal, an input for a control signal, and a second connection connectable to a load; a second terminal for connection to a load; a stealing circuit having an input connected to an output of the bypass switch, and an output connected to the second terminal; and a power steal module having an input connected to the output of the SCR circuit and an output connected to the second terminal. 
         [0047]    The bypass switch may incorporate one or more MOSFETs that are switched. The power steal module may incorporate one or more MOSFETs that are switched to steal power. The stealing circuit may have an energy storage unit. Stolen power may go to the energy storage. 
         [0048]    The energy storage cell may incorporate one or more super capacitors. 
         [0049]    The bypass switch may have circuitry that incorporates a positive bypass switching MOSFET, and a negative bypass switching MOSFET. 
         [0050]    The mechanism may further incorporate a MOSFET gate signal shaper that provides a gate signal to the power steal module that softens a transition of turning on or off of the one or more MOSFETs. 
         [0051]    The mechanism may further incorporate an SCR control signal circuit having an output that provides the control signal to the input of the SCR circuit. The control signal provided to the input of the SCR circuit may result in making power available or not available at the second connection of the SCR circuit. The second connection of the SCR circuit may be connected to the load. The load may be a heater. 
         [0052]    A power supply unit for a thermostat and electric heater may incorporate a bypass switch circuit having an input connectable to a first line voltage, a power steal device having an input connectable to an output of the bypass switch circuit, an energy storage having an input connected to an output of the power steal device, an SCR gate signal circuit having an input connected to an output of the energy storage, and an SCR circuit having an input from an output of the SCR gate signal circuit and an input connectable to a second line voltage, and having an output for providing a controlled second line voltage. The bypass switch circuit may have one or more MOSFET switches. Also, the power steal device may have one or more MOSFET switches. 
         [0053]    The unit may further incorporate a linear regulator connected to the output of the energy storage. 
         [0054]    The unit may further incorporate a zero crossing detector having an input connectable to the second line voltage. 
         [0055]    The unit may further incorporate a FET gate signal shaping circuit having an input for receiving zero crossing information from the zero crossing detector and having an output for providing a sync signal to the bypass switch circuit. 
         [0056]    The unit may further incorporate a reverse wave protection circuit having an input connected to the first line voltage, a second input connected to the output of the energy storage, and having an output for providing a protect signal to the FET gate signal shaping circuit. 
         [0057]    U.S. patent application Ser. No. 13/868,754, filed Apr. 23, 2013, and entitled “Triac or Bypass Circuit and MOSFET Power Steal Combination”, is hereby incorporated by reference. 
         [0058]    In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
         [0059]    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.