Abstract:
The interfacing of a controller having an output with components (e.g., a triac) that require more current to successfully drive than the amount of current that is drawn by the circuit or controller which is being driven. The extra current drawn may be efficiently used, rather than wasted, for other circuitry such as a power supply for the electronics of the controllers or other devices. Also, another source may automatically come into place to provide current for the power supply or other circuitry when the driving controller becomes inactive.

Description:
BACKGROUND  
       [0001]     This invention pertains to actuators and particularly to actuator controls. More particularly, it pertains to interfacing among controllers.  
       SUMMARY  
       [0002]     The invention may be an interface for an actuator controller. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0003]      FIG. 1  is a schematic of a system for a controller interface; and  
         [0004]      FIG. 2  is a schematic of another version of the system for a controller interface. 
     
    
     DESCRIPTION  
       [0005]     The invention is a system that may be used for providing triac loading without wasting the current used for loading which may be needed if the output of the triac is connected to a high impedance mechanism, thus resulting in an efficient interface. Actuators designed without microcontrollers that have floating control inputs may typically drive an actuator motor directly from the floating control input. This may cause a current link on the floating control input that is in line with the worst-case minimum input current required to keep a triac active on virtually all controllers (i.e., legacy and modern). To avoid issues, the present invention may efficiently source enough current on a modern microcontroller driven actuator to maintain the worst-case minimum input current required by the triac output controller.  
         [0006]     The invention solves the technical challenge by diverting the sourced current from the regular power terminals to the floating control inputs by means of an appropriate voltage drop. This may provide the modern microcontroller driven actuator an advantage of backward compatibility with all controllers.  
         [0007]     The present invention may be effected by using a series of diodes to guarantee current flow from the floating inputs whenever the inputs are active. Essentially, it may incorporate an additional rectifier with a lower forward voltage drop. This lower voltage drop may force the current to take the easiest path to the power supply, which in this case is via the present floating control inputs. When the inputs are not being driven, input current may revert back to the normal power input terminals via the rectifier with the larger forward voltage drop.  
         [0008]     The feasibility of the floating control scenario may be verified. One may measure the voltage drop on the diodes connected in series and verify that the voltage drops down when either of the floating inputs are used. This indicates that the input current changes its path to the power supply. It may be noted that several diodes were added to the design to assure the desired path of current to the power supply.  
         [0009]      FIG. 1  shows an illustrative, specific instance of the present invention. Other instances or examples may be used to illustrate the present invention. One application of this invention may be interfacing a legacy output controller with a modern actuator controller. A circuit or system  10  shows an application of providing low current triac signals to floating inputs of a microcontroller  11 , an actuator microcontroller  11 , or an overall controller  11 . Signals to microcontroller  11  may originate from triacs  12  and  13  in a triac controller  14  or in an HVAC controller. Controller  14  and the circuitry for interfacing the controller  14  with the microcontroller  11 , and possibly with other components of system  10 , may be incorporated into an overall controller  80 . The triacs may be substituted with other kinds of switches or solid state devices. An AC source having a rms voltage between 20 and 40 volts from secondary winding a step-down power transformer  18 , which has its primary winding connected to a 120 volt, 60 cycle power line source across terminals  59  and  49  of the primary winding, may be provided across terminals  15  (R) and ground  16  (C). The terminal  49  to a ground may be isolated from the ground  16  of the secondary winding and the system circuit  10 . The power line source may instead be of another voltage and cycle rate than indicated here.  
         [0010]     The controller  14  may output one of several signals, for example, a counterclockwise directing signal or a clockwise signal destined for an actuator  17 . A processor  19  may receive a signal at terminal  21  indicating whether and which direction the actuator  17  is to be activated. For instance, the actuator  17  may be connected to a damper in an air duct (e.g., it could be connected to a valve or other mechanism needing control). A signal at terminal  21 , indicating that the actuator turn the damper counterclockwise (CCW), may go to the processor  19 . Processor  19  may output a signal to a gate of triac  12 . Triac  12  may be turned on with the gate signal and current may flow through the triac  12  from input  15 , through diode  22  and a 27.4 K-ohm resistor  23  to an input  24  of the actuator microcontroller  11 . Microcontroller  11  may be a PIC18F4431 part available from Microchip Technology Inc. Microcontroller  11  may have a high impedance input and does not need a large signal to effect an excitation signal on a line  25  from the microcontroller powerful enough to drive a sizable actuator  17  with significant torque to operate a large damper, valve, or the like, in a CCW direction. Actuator  17  may be a motor (e.g., brushless motor), solenoid, or the like. Line  26  may be another microcontroller  11  output for driving the actuator  17  in the opposite clockwise (CW) direction. Line  27  may be a common terminal or reference ground relative to lines  26  and  27 . Line  27  may or may not be tied in with ground  16 .  
         [0011]     The CCW signal from triac  12  may appear as a half-wave rectified signal in view of diode  22  having its anode connected to the triac  12 . Also, a diode  28  having an anode connected to the ground  16  and a cathode connected to input or line  24  may remove a significant portion of a negative signal on line  24 . A 24.7 K-ohm resistor  29 , connected to the cathode of diode  22 , may be a pull-down resistor connected to the ground  16 . There may be a 0.1 microfarad capacitor  31  connected between line  24  and ground  16 . Capacitor  31  may operate as a filter, particularly in conjunction with resistor  23 . A diode  32  may have an anode connected to line  24  and a cathode connected to Vcc  33 . Diode  32  may suppress positive signals that exceed the voltage level of Vcc  33 , particularly since the 24.7 K-ohm resistor  23  is in series with diode  32  relative to Vcc, which would realize the excess voltage as a voltage drop across it (the resistor). A 0.1 microfarad capacitor  34  may be connected between the output or line  35  of triac  12  and ground  16 . Capacitor  34  may operate as a filter and/or storage.  
         [0012]     At this extent of the description, the triac  12  may be turned on but there may not be sufficient current going from the output  35  through the noted circuitry to line or input  24  of microcontroller  11 . Thus, a way to increase the current from line  15  through triac  12  to line  35  so that the minimum current required to keep triac  13  active is to attach a load on line  35 . An easy solution would be to connect a resistor between line  35  and ground. However, that would be an inefficient approach resulting in a waste of electrical power. Also, this approach or other wasteful expenditure of power may cause problems with the circuit and associated components because resulting generated heat, even a small amount, may cause failure of devices, integrated circuits, transistors, electrolytic capacitors, and other active and passive components. A solution may be to divert current from line  35  of the triac  12  to be used within the present circuit or system  10 . A diode  36  may have an anode connected to line  35  and a cathode connected to a line  37 . Line  37  may be connected to an anode of a diode  38 . Diode  38  may have a cathode connected to an input  39  of a DC-to-DC voltage converter  40  which can constitute a switching power supply. The converter  40  may be a MC33063 part available from Fairchild Semiconductor Corporation. Converter  40  may output a voltage on line  41  which may provide electrical power for circuit or system  10 . With this approach, current taken from triac  12  is sufficiently significant so that it may continue to operate in view of providing a very low current signal to input line  24  of the actuator microcontroller  11 , and yet provide an efficient use of the taken current within the system  10 .  
         [0013]     A simplified example circuit  43 , operating a power supply filter, at the output  41  of the converter  40  for providing the Vcc  33  supply to the system  10 , may include a Schottky rectifier  42  having a cathode connected to line  41  and an anode connected to the ground  16 . Rectifier or diode  42  may be a 10BQ060 part available from International Rectifier. A 1,000 microhenry inductor  44  may have one end connected to output or line  41  and another end connected to Vcc line  33 . A 1,000 microfarad capacitor  45  may have one end connected to line  33  and the other end connected to ground  16 . Also, there may be a 15 K-ohm resistor  46  connected between line  33  and ground  16 . There may be other components, such as capacitors, connected between line  33  and ground  16 .  
         [0014]     On line  37 , at the input side of converter  40 , may be a zener diode  47  having a cathode connected to line  37  and an anode connected to ground  16 . Diode  47  may be a P6SMB56AT3 part available from Semiconductor Components Industries, LLC. These components  47  and  38 , converter  40  and filter  43  may constitute a power supply  50 . Power supply  50  may also be regarded as a conditioning circuit, or referred to with another appropriate name. Also, there may be a storage circuit  48  that may have four or so  220  microfarad capacitors (two capacitors  51  and  52  are shown) connected between line  37  and ground  16 . Circuit  48  may also be referred to as a filter or a part of one, or another appropriate name.  
         [0015]     At this point of the description, it can be noted that current needed to sustain the operation of triac  12  may be used to sustain the power supply  50  for Vcc  33 . However, when the current of the triac is absent, then the power supply may be sustained by a current from the secondary winding of the transformer  18  connected to terminals  15  and ground  16 . A goal that may be achieved by circuit  10  is that when a triac ( 12  or  13 ) is on, current is being provided from it for the power supply  50 , and then when the triacs are off, the current source may be from the transformer  18 . To effect a current source selection scheme is to have each source with a different voltage presented to line  37 . It may be again noted the ultimate source is the transformer  18  at terminal  15  relative to ground  16 , even with respect to the triacs  12  and  13 . The voltage drops between the two immediate sources may be different. The source with the smaller voltage drop should be the prevailing current source. The source via triac  12  and diode  36  may be regarded as having less than three diode voltage drops in a series below the terminal 15 voltage. The other voltage source via four diodes  53 ,  54 ,  55  and  56  of diode module  60  may be regarded as having about four diode voltage drops cumulatively below the terminal 15 voltage. The number of diode voltage drops or diodes may be other than four. The voltage difference between the two sources may be at least one diode drop. Diode module  60  may also be regarded as a voltage drop circuit or a supply circuit, or referred to with another appropriate name. Circuits  48 ,  50  and  60  may be referred to as an interface circuit  88 .  
         [0016]     Diode  53  may have its anode connected to terminal  15 , diode  54  may have its anode connected to a cathode of diode  53 , diode  55  may have its anode connected to a cathode of diode  54 , and diode  56  may have its anode connected to a cathode of diode  55 . A cathode of diode  56  may be connected to the input or line  37  to the switching power supply circuit  50 . So if the triac  12  or  13  is on or activated, the voltage level at the cathode of diode  36  may be greater than the voltage available from diode. Thus, no current flow is available through diode  56  since there is not a sufficient positive drop from anode to cathode across at least diode  56  for a forward current flow, and there may be virtually no reverse current flow because of the diode characteristic. If triac  12  or  13  is off or inactivated, there is not a sufficient positive voltage drop from anode to cathode across diode  36  for a forward current flow, and there may be virtually no reverse current flow because of the diode action. Thus, there may be current flow from only diode  56  to line  37  when the triacs  12  and  13  are off, or there may be current flow only from diode  36  when triac  12  or  13  is on. It may be noted that the voltage at both diodes  36  and  56  have similar waveforms which are in phase due to their common source at terminal  15 . Virtually all of the current provoked from triacs  12  and  13  may be utilized by system  10 , resulting in significant efficiency in keeping the triacs on. The triacs  12  and  13  may be on just long enough to effect a CCW or CW movement of actuator  17  as needed.  
         [0017]     Relative to getting the actuator  17  to operate in a CW manner, the components and operations may be of the same nature as those for getting the actuator to operate in the CCW manner. Components and lines  75 ,  76 ,  74 ,  62 ,  69 ,  63 ,  68 ,  72 ,  71  and  64  of the CW control portion may correspond to components and lines  35 ,  36 ,  34 ,  22 ,  29 ,  23 ,  28 ,  32 ,  31  and  24 , in the given order, respectively, of the CCW control portion.  
         [0018]     A signal on the gate of triac  13  may result in a small current signal on output line  75  through a diode  62  and 27.4 K-ohm resistor  63  to an input or line  64  for microcontroller  11  so as to provide a signal or power via line  26  to initiate CW movement of the actuator  17 . A 0.1 microfarad capacitor  74  may be connected from line  75  to ground  16 . A 27.4 K-ohm resistor  69  may be connected from the cathode of diode  62  to ground  16 . A diode  68  may have a cathode connected to line  64  and an anode connected to ground  16 . A diode  72  may have an anode connected to line  64  and a cathode connected to Vcc  33 . A 0.1 microfarad capacitor  71  may have one end connected to line  64  and the other end connected to ground  16 .  
         [0019]     The purposes and operational aspects of these components of the CW portion may be similar to those purposes and aspects of like components of the CCW portion of system  10 . A diode  76  may have an anode connected to the triac  13  output line  75  and a cathode connected to line  37 . The manner in which current is provided via line  37  to power supply  50 , in lieu of the current from the diode module  60 , by triac  13  may be the same as the way the current is provided by triac  12  via diode  36  to line  37 .  
         [0020]     The half-wave rectifier  60  in  FIG. 1  may be replaced by a full-wave rectifier  85 . An example of rectifier  85  is shown in  FIG. 2 . With rectifier  85  in  FIG. 1 , one, two or more diodes of the group of diodes  53 - 56  from the rectifier  60  may be left in the circuit to maintain a sufficiently greater voltage drop than that present at line  37  if one of the triacs  12  and  13  is turned on. Diode  53  may have its anode connected to an output  87  of rectifier  85 . Since the ripple is less severe at the output of the full-wave rectifier than at the output of the half-wave rectifier  60 , then less capacitance would be required in storage circuit  48 . Other devices may be utilized to provide a fully rectified voltage on line  37  to the power supply circuit  50 . The full-wave rectifier may be more efficient that the half-wave rectifier.  
         [0021]     As shown in  FIG. 2 , rectifier  85  may have a diode  81  with an anode connected to the input of the rectifier and output terminal or line  15  of the secondary winding of transformer  18  Diode  81  may also have a cathode connected to the output  87 . A diode  82  may have a cathode connected to the input of the rectifier and an anode connected to the ground  16 . A diode  83  may have a cathode connected to the output  87  and an anode connected to a line or terminal  86  rather than  16 , since in this configuration having the rectifier  85  that terminal or line of the secondary winding of transformer  18  is not connected directly to ground  16 . A diode  84  may have an anode connected to the anode of diode  83  and a cathode connected to ground  16 .  
         [0022]      FIG. 2  not only shows an alternative power source, i.e., a full rectifier  85 , in lieu of the half-wave rectifier  60 , but it also reveals another approach for switching sources of voltage to the power supply circuit  50 . Diodes  36  and  76  may be replaced with switches  93  and  94 , respectively. Also a switch  96  may be connected in series between the output of rectifier  85  or  60 , as this configuration may be used with various rectifiers or sources of rectified voltage. The switches  93 ,  94  and  96  may be turned on or off with control lines  91 ,  92  and  95 , respectively. These control lines  91 ,  92  and  95  may be connected to the microcontroller  11  in this configuration but may be operated with some other mechanism. Switches  93 ,  94  and  96  may be regarded as a switching circuit  97 . The switches may be FET&#39;s or some other kind of mechanism that may provide a similarly operative. In the case of FET&#39;s, the control lines may be connected to gates of the FET&#39;s, respectively.  
         [0023]     Besides to the switch  93 , line  35  may be connected to the microcontroller  11 . Similarly, besides to switch  94 , line  75  may be connected to microcontroller  11 . Microcontroller  11  may sense when there is a voltage at the output of the triac  12  or  13  (indicating that the triac is on) via line  35  or  75 , respectively. Upon sensing this voltage, microcontroller  11  may provide a signal to control line  91  or  92  to turn on switch  93  or  94  to connect line  35  or  75 , respectively, to line  37 . Simultaneously, microcontroller  11  may send a signal via control line to open switch  95  to disconnect the output of the rectifier from line  37  to the input of power supply circuit  50 . So, the triac that is on to provide an actuator signal to microcontroller  11  may be providing power to circuit  50 . When no triac is on, then power may be provided from the rectifier (full-wave or half-wave) to the power supply circuit  50 . It may be possible for microcontroller  11  instead to sense an on voltage of either triac  12  or  13  via the actuator input line  24  or  64 , respectively. The sensing mechanism of the microcontroller  11  may be a distinct circuit separate from the microcontroller  11 . It may be noted that in some actuator control configurations, that a triac of the triac controller  14  may be on only about ten percent of the time when the system  10  is in operation.  
         [0024]     Rectifier  85 , switching circuit  97 , storage circuit  48  and power supply circuit  50  may be regarded as an interface circuit  98  in  FIG. 2 . Rectifier  85  may be configured as a half-wave rectifier and still be a part of the interface circuit  98 . Similarly in  FIG. 1 , diode module, voltage drop circuit or supply circuit  60  may be configured as a full-wave rectifier, as long as the appropriate voltage drop is maintained with circuit  60 , and still be a part of the interface circuit  88 .  
         [0025]     In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense.  
         [0026]     Although the invention 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 present specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.