Abstract:
A configurable output circuit is disclosed. The output circuit comprises an analog output circuit capable of producing an analog output signal usable to control the output device, a binary output circuit capable of producing a binary output signal usable to control the output device, and means for configuring the output circuit to provide an analog output mode or a binary output mode so that the output signal is either the binary output signal or the analog output signal. A method of providing an output control signal to an output device comprises providing an output circuit having a binary output circuit and an analog output circuit, receiving a first output mode control signal, configuring the output circuit in either a binary output mode or an analog output mode, receiving a first device control signal, and providing the output control signal to the output device as either a binary signal or an analog signal.

Description:
FIELD  
       [0001]     The present description relates generally to output circuits that provide output signals usable to control output devices. In particular, the present description relates to output circuits that are configurable to provide either an analog or binary output signal usable to control output devices.  
       BACKGROUND  
       [0002]     Output circuits are used for controlling output devices. In industrial applications, for example, output circuits are used to control devices such as fans, actuators, temperature control systems, lighting systems, and so on. One type of output circuit is an analog output circuit. Typically, analog output circuits provide a continuously varying output voltage or current having a magnitude which is indicative of a desired output state of an output device. For example, in some applications, industry standards have been developed which specify that such voltage output circuits provide an output voltage in the range of 0 to 10 volts, with the output voltage having a magnitude that is proportional to a desired output condition. Thus, for a variable speed motor, an output circuit may provide an output voltage having a magnitude of 5 volts to cause the motor to operate at 50% maximum speed. An output device that is controlled in this manner is often referred to as a voltage-controlled output device.  
         [0003]     Another type of output circuit is binary output circuit. Typically, binary output circuits provide an output based on the base-two number system (i.e., in 1&#39;s and 0&#39;s) or another system wherein the output provided by the circuit has only two discrete levels (e.g., either 5 volts or 0 volts).  
         [0004]     In general, an output device is either analog controlled output device or a binary controlled output device, but not both. Generally, it is necessary that the output circuit be matched with the type of output device used, that is, that analog output circuits be used with analog-controlled output devices and binary output circuits be used with binary-controlled output devices.  
         [0005]     When installing a new control system or modifying an existing control system, it is not always known which type of output devices will be or have been used. For example, when modifying an existing control system, where a new controller is installed but the output devices of the original system remain in place, it is generally not known in advance whether particular output devices are analog output devices or binary output devices. While this information can be determined by examining product specifications for the output device and/or by performing suitable measurements, this process is time consuming and not always possible or practical to perform.  
         [0006]     It is known to provide a circuit (e.g., in a device) that provides an analog or a binary output. It is also known to provide a circuit that provides both an analog and a binary output. However, such known circuits are “hardwired” and are not configured to be configurable, reconfigurable, adapted, changed, or the like. Once the circuit is manufactured or fabricated, the type of outputs cannot be altered or changed (e.g., between analog and binary). As such, an additional circuit or device would need to be provided if a different type of output is needed or desired (e.g., additional use or functionality is required upon or after installation).  
         [0007]     Accordingly, it would be advantageous to provide a circuit that is adaptable. It would also be advantageous to provide an output that is configurable (or reconfigurable) before, during, or after installation (e.g., the electrical device is in the field). It would further be advantageous to provide an output that can be configured by software before, during or after installation. To provide an inexpensive, reliable, and widely adaptable configurable output that avoids the above-referenced and other problems would represent a significant advance in the art.  
       SUMMARY  
       [0008]     The present invention relates to a configurable output circuit capable of producing an output signal to control an output device. The output circuit comprises an analog output circuit capable of producing an analog output signal usable to control the output device, a binary output circuit capable of producing a binary output signal usable to control the output device, and means for configuring the output circuit to provide an analog output mode or a binary output mode so that the output signal is either the binary output signal or the analog output signal.  
         [0009]     The present invention also relates to a system comprising a controller, an output device, an output circuit configurable in an analog output mode wherein an analog output circuit portion of the output circuit is capable of producing an analog output signal usable to control the output device, and a binary output mode wherein a binary output circuit portion of the output circuit is capable of producing a binary output signal usable to control the output device.  
         [0010]     The present invention further relates to a configurable output circuit capable of producing an output signal. The output circuit comprises a first input configured to receive a first input signal, a first output circuit being capable of producing an analog output signal based on the first input signal and usable to control an output device, a second output circuit being capable of producing a binary output signal based on the first input signal and usable to control the output device, a second input configured to receive a second input signal, and a switch being capable of switching the output signal between a first mode of operation in which the first output circuit is active to a second mode of operation in which the second output circuit is active, the switch switching the configurable output circuit between the first mode of operation and the second mode of operation responsive to the second input signal.  
         [0011]     The present invention further relates to a method of providing an output control signal to an output device. The method comprises providing an output circuit having a binary output circuit and an analog output circuit, receiving a first output mode control signal, configuring the output circuit in either a binary output mode or an analog output mode, receiving a first device control signal, and providing the output control signal to the output device as either a binary signal or an analog signal.  
         [0012]     The present invention further relates to various features and combinations of features shown and described in the disclosed embodiments. 
     
    
     DESCRIPTION OF THE FIGURES  
       [0013]      FIG. 1  is a block diagram illustrating a control system that includes a configurable output circuit according to an exemplary embodiment.  
         [0014]      FIG. 2  schematically illustrates the configurable output circuit of  FIG. 1  according to a first exemplary embodiment.  
         [0015]      FIG. 3  schematically illustrates the analog output portion of the configurable output circuit of  FIG. 2  according to an exemplary embodiment.  
         [0016]      FIG. 4  schematically illustrates the binary output portion of the configurable output circuit of  FIG. 2  according to an exemplary embodiment.  
         [0017]      FIG. 5  schematically illustrates the configurable output circuit of  FIG. 1  according to a second exemplary embodiment.  
         [0018]      FIG. 6  schematically illustrates the configurable output circuit of  FIG. 1  according to a third exemplary embodiment.  
         [0019]      FIG. 7  is a block diagram illustrating a control system that includes a configurable output circuit according to an alternative embodiment.  
         [0020]      FIG. 8  schematically illustrates the configurable output circuit of  FIG. 7  according to a first exemplary embodiment.  
         [0021]      FIG. 9  schematically illustrates the analog output portion of the configurable output circuit of  FIG. 8  according to an exemplary embodiment.  
         [0022]      FIG. 10  schematically illustrates the binary output portion of the configurable output circuit of  FIG. 8  according to an exemplary embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0023]     The configurable output design is adaptable for any of a variety of controlled systems or applications, including office, home, manufacturing, industrial, commercial or other systems that employ a controller output. For purposes of explanation, the components of the disclosed embodiments will be illustrated as a configurable output designed for an industrial control application, such as a heating, ventilation, and air-conditioning (HVAC) system, the features of the disclosed embodiments have a much wider applicability.  
         [0024]      FIG. 1  illustrates a block diagram of a control system  10  including a configurable output circuit  20  according to an exemplary embodiment. Control system  10  may be any type of control system. For example, in one embodiment, control system  10  is an industrial control system such as a heating, ventilating, and air-conditioning (HVAC) system. Control system  10  includes an output system or device  12 , a pulse width modulated (PWM) signal  16 , and a binary output control (BOC) signal  18  to output circuit  20 .  
         [0025]     Output system or device  12  is coupled to output circuit  20 . Output system or device  12  may be a lighting system, a mechanical actuator, a fan, a temperature control system, or any other type of output device. In one embodiment, output system or device  12  is configured to accept an analog output signal  40  from output circuit  20 . In another embodiment, output system or device  12  is configured to accept a binary output signal  42  from output circuit  20 .  
         [0026]     PWM signal  16  is, for example, a time-optimized PWM signal provided by system  10  to generate an analog output signal. BOC signal  18  is provided by system  10  (e.g., from a system controller configured to control output system or device  12 ) as a control signal which is the basis for a binary output signal to be provided to output system or device  12 . For example, in one embodiment BOC signal  18  is set to either a 0 volt level or a 5 volt level which output circuit  10  processes into a binary output signal. BOC signal  18  may be generated by any of a variety of controllers, such as a microprocessor-based controller, the output of an A/D or D/A converter, the output of a potentiometer, or the like.  
         [0027]     Output circuit  20  is configured to be coupled to output system or device  12 , and may be incorporated into system  10  in a number of ways. For example, output circuit  20  may be may be included in any of a variety of electrical or electronic apparatuses or subsystems used within system  10 . In one embodiment, an electronic controller within system  10  includes one or more configurable output circuits  20 . In another embodiment, the controller is configured to provide one or more fixed (or “hard-wired”) outputs and one or more output circuits  20 . Such devices (with configurable outputs) are intended to be more flexible during installation (e.g., connectable to systems or devices not known when the device was manufactured; to provide future adaptability to add or change systems or devices connected to the device; or the like).  
         [0028]     Output circuit  20  includes a buffer  22 , an optical isolator  24 , a binary output device  26 , optical isolators  28  and  30 , an integrator  32 , and a switch  34 . Output circuit  20  receives PWM signal  16 , and BOC signal  18  as inputs. Output circuit  20  is subdivided into an analog output circuit  36  and a binary output circuit  38 . Output circuit  20  is capable of being configured (e.g., using software during installation or during a later modification) to provide an analog output mode or a binary output mode depending on the type or characteristics of output system or device  12 . In the analog output mode of operation, output circuit  20  provides an analog output signal  40  to output system or device  12 . In the binary output mode of operation, output circuit  20  provides a binary output signal  42  to output system or device  12 .  
         [0029]     Buffer  22  is configured to receive PWM signal  16 , and BOC signal  18  as inputs. Buffer  22  is further configured to isolate the sources (not shown) of PWM signal  16 , and BOC signal  18  by, for example, minimizing impedance effects from output circuit  10 .  
         [0030]     Optical isolator  24 , included in binary output circuit  38 , is coupled to buffer  22  and to binary output device  26  and is configured to receive BOC signal  18  from buffer  22 . Optical isolator  24  is a transistor or other suitable electronic switching device. Optical isolator  24  operates to apply BOC signal  18  to binary output device  26 .  
         [0031]     Binary output device  26 , included in binary output circuit  38 , is coupled to optical isolator  24  and output system or device  12 . Binary output device  26  is configured to receive BOC signal  18  from optical isolator  24  and to provide binary output signal  42  to output system or device  12  in response to BOC signal  18 . Binary output device  26  is also configured to optically isolate output system or device  12  from the source of each input (not shown) to output circuit  20  to, for example, prevent electrical damage to each source. For example, in one embodiment, output system or device  12  is an alternating current (AC) device, and binary output device  26  is configured to switch an AC power source according to BOC signal  18  while optically isolating the source of BOC signal  18  from the AC power source.  
         [0032]     Optical isolators  28  and  30 , included in analog output circuit  36 , are coupled to buffer  22 . Optical isolators  28  and  30  are further coupled to integrator  32  and are configured to receive PWM signal  16  from buffer  22  and to provide PWM signal  16  to integrator  32 . Optical isolators  28  and  30  are also configured to optically isolate output system or device  12  from the source of each input (not shown) to output circuit  20  to, for example, prevent electrical damage to each source.  
         [0033]     Integrator  32 , included in analog output circuit  36 , is coupled to optical isolators  28  and  30 , and to switch  34 . Integrator  32  is configured to receive PWM signal  16  from optical isolators  28  and  30 , and to provide an analog output signal  40  to switch  34  that is based on PWM signal  16  as received from optical isolators  28  and  30 .  
         [0034]     Switch  34 , included in analog output circuit  36 , is coupled to optical isolators  28  and  30 , integrator  32 , and output system or device  12 . Switch  34  is configured to receive analog output signal  40  from integrator  32 , as well as PWM signal  16  from optical isolators  28  and  30 , and to provide analog output signal  40  to output system or device  12  in response to PWM signal  16 .  
         [0035]     Output circuit  20  is configured to receive PWM signal  16  and BOC signal  18 , and to processes PWM signal  16  and BOC signal  18  according to the configuration of output circuit  20 . Output circuit  20  then provides the processed output signal to output device  12 . Depending on the configuration of output circuit  20  as determined by PWM signal  16  and BOC signal  18 , output circuit  20  provides an analog output signal  40  using analog output circuitry  36 , or a binary output signal  42  using binary output control circuitry  38 . For example, according to an exemplary embodiment, output circuit  20  may be configured to operate in analog output mode by varying PWM signal  16  from 0 percent to 100 percent and setting BOC signal  18  to 0 volts. When output circuit  20  is configured to operate in analog output mode, optical isolator  24  is “OFF” according to BOC signal  18 , and PWM signal  16  is received by optical isolators  28  and  30 . Optical isolators  28  and  30  provide PWM signal  16  to integrator  32 , which then provides analog output signal  40  based on PWM signal  16  to switch  34 . Switch  34  is “ON” according to PWM signal  16 , and provides analog output signal  40  to output system or device  12 .  
         [0036]     Continuing with the embodiment, output circuit  20  may be configured to operate in binary output mode by setting PWM signal to 0 percent and switching BOC signal  18  from 0 volts to 5 volts. When output circuit  20  is configured to operate in binary mode, BOC signal  18  is received by switch  24 , which is “ON” while switch  34  is “OFF” according to PWM signal  16 . Optical isolator  24  then provides a signal to binary output device  26 , which provides binary output signal  42  to output system or device  12 .  
         [0037]      FIG. 2  schematically illustrates a configurable output circuit  120  which is an embodiment of output circuit  20  shown in  FIG. 1 . Output circuit  120  receives PWM signal  116 , and BOC signal  118  as inputs, and includes a buffer  122 , an optical isolator  124 , a binary output device in the form of a triac  126 , optical isolators  128  and  130 , an integrator  132 , and a switch  134 . Output circuit  120  is subdivided into an analog output circuit  136  (shown in  FIG. 3 ) and a binary output circuit  138  (shown in  FIG. 4 ). In analog output mode, analog output circuit  136  provides analog output signal  140 . In binary output mode, binary output circuit  138  provides binary output signal  142 .  
         [0038]     Table I below provides exemplary input and output signal ratings for output circuit  120 .  
                                                             Symbol   Parameter   Value   Units                                PWM   Pulse Width Modulated (PWM) Input Signal                   Maximum Frequency   1000   Hz           Minimum Input Signal   3.15   V       BOC   Binary Output Control Signal           Minimum Input High Level   3.51   V       CO   Configurable Output           Maximum Output Voltage: analog output, binary output   10, ±36   V           Maximum Output: analog output, binary output   10, 500   mA           Maximum Surge Current (binary output 10us)   5   A           Maximum Blocking Voltage (binary output)   400   V       15 VI   15 V Isolated Power Supply   14.25 to   V               15.75       5 VI   5 VI Isolated Power Supply (5 VI isolated power supply   4.75 to   V           derived from 15 VI using voltage reference)   5.05       Power   Maximum Power Dissipation:       Dissipation   Analog Output   735   mW           Binary Output   1961   mW                  
 
         [0039]     Table II below provides exemplary component values for output circuit  120 .  
                                           Component           Qty   Reference   Description                   1   U5   TL431       1   C1   ELEC, 2.2 UF, 50 V, TA, 20%, −40 + 85       1   C2   Mult. Cer. SMD Cap. 2,2 nF 50 V 0805 X7R 10%       1   C3   Capacitor, Ceramic Disc, 0.01 uF, 20%, 500 V, −55 + 105, Crimped               Leads       1   C4   CAP., POLYP, .01UF, 100 V, RADIAL, 10%, −40 + 100       2   D1-D2   DIODE, 75 V 200 mA, BAS16 SOT23       1   D3   DIODE, DUAL DIODE, LOW POWER       2   E1,E2   TERM, FASTON, 0.250 TAB SIZE       2   Q1-Q2   MMBTA56, DRIVER, PNP, S3       1   Q3   MOSFET_N-Channel_60 V_115 mA_2N7002_SOT23       1   Q4   TRIAC, Q4004F42 4 A 400 V TO220       1   R14   RES, 340 OHM, 1%, 1/8 W 200 PPM       2   R15-R16   RES, MF, 1.54 K, 1 %, .125 W, TA, 100 PPM, AS0017       1   R17   RES, THK, 47, 1%, .062 W, S2, THK, 100 PPM       2   R18-R19   RES, 10 K, 1% .0625W, THK 100 PPM       1   R20   RES, 3.32 K, 1% .0625W, THK 100 PPM       1   R21   RES, 1.54 K OHM, 1%, 1/16 W 100 PPM       1   R22   RES, 75 OHM, 5%, 1/2 W 200 PPM       1   R23   RES, CF, 47, 5%, .5 W, TA, #PPM       1   R7   R, 75.OK, 1%, .062 W, S2, THK, 100 PPM       2   R8,R10   RES, 100 K, 1%, 1/16 W 100 PPM       1   R9   RES, 47.5 K, 1% .0625 W, THK 100 PPM       1   U2   IC_OperationalAmplifier_Quad_LM2902_SO14       1   U6   IC, DIGITAL, 74AHC1G14, SCHMITT TRIGGER INVERTER, SINGLE               GATE, CMOS, SMT, SOT23-5       1   U7   IC, OptoCoupler, TLP16OG       2   U8-U9   IC, OPTOISOLATOR, HCPL-181, 4 PIN SMT PKG       1   VR1   PTC, 10, 24 V, 320 mA, TR                  
 
         [0040]     Buffer  122  includes buffers  150  and  152 . In one embodiment, buffers  150  and  152  are part of a single integrated circuit (IC) package. In another embodiment, buffers  150  and  152  are separate ICs. Buffer  150  receives PWM signal  116  as an input. Buffer  150  is coupled to optical isolator  128  via resistor  154 , and to optical isolator  130  via resistor  156  such that optical isolators  128  and  130  receive PWM signal  116  as an input. Buffer  152  receives BOC signal  118  as an input. Buffer  152  is coupled to optical isolator  124  via resistor  158  such that optical isolator  124  receives BOC signal  118  as an input.  
         [0041]     The anode of optical isolator  124  is coupled to buffer  152  via resistor  158  such that it receives BOC signal  118 , while the cathode of optical isolator  124  is coupled to ground. MT 1  of optical isolator  124  is coupled to triac  126  via resistor  160  and MT 2  of optical isolator  124  is directly coupled to the gate of triac  126 . In the illustrated embodiment, optical isolator  124  is an optically isolated switch. In this embodiment an optically isolated switch is used in order to isolate BOC signal  118  from an AC output device (not shown) coupled to output circuit  20  without the slow speed and short life of the contacts associated with mechanical relays.  
         [0042]     Triac  126 , included in binary output circuit  138 , is configured to receive BOC signal  118  from optical isolator  124  and to provide binary output signal  142  to an output system or device (not shown) coupled to output terminals  196  and  198  in response to BOC signal  118 . In the illustrated embodiment, triac  126  is optically controlled by optical isolator  124 .  
         [0043]     Optical isolator  128 , included in analog output circuit  136 , is coupled to buffer  150  via resistor  154  such that it receives PWM signal  116  as an input. Optical isolator  128  is further coupled to integrator  132  via buffer  162  and resistor  164  such that it provides inverted PWM signal  116  to integrator  132 . Optical isolator  130 , included in analog output circuit  136 , is coupled to buffer  150  via resistor  156  such that it receives PWM signal  116  as an input. Optical isolator  130  is further coupled to integrator  132  via buffer  162  and resistor  164  such that it provides inverted PWM signal  116  to integrator  132 .  
         [0044]     Integrator  132 , included in analog output circuit  136 , includes operational amplifier  172 , capacitor  174 , and resistors  176 ,  178 , and  180 . In the illustrated embodiment, capacitor  174  and resistors  176 ,  178 , and  180  are selected such that integrator  132  has a time constant of about 1.045 seconds. In another embodiment, other values may be selected. Integrator  132  is coupled to optical isolator  128  via buffer  162  and resistor  164  such that it receives inverted PWM signal  116  as an input to non-inverting input of operational amplifier  172 . Integrator  132  is further coupled to switch  134  and is configured to provide a time averaged version of inverted PWM signal  116  to switch  134  in the form of analog output signal  140 .  
         [0045]     Switch  134 , included in analog output circuit  136 , includes transistor  182 . The drain of transistor  182  is coupled to integrator  132  such that it receives analog output signal  140  from integrator  140 . The source of transistor  182  is coupled to output terminal  196  and to integrator  132  via diode  184  such that switch  134  provides analog output signal  140  to an output system or device (not shown) coupled to output terminals  196  and  198 , as well as to integrator  132  as a feedback signal. The gate of transistor  182  receives inverted PWM signal  116  as an input via diode  186 , resistor  188 , and transistor  190 .  
         [0046]      FIG. 3  schematically illustrates a simplified version of output circuit  120  in which the circuit components that are not used in analog output mode have been removed and the components of analog output circuit  136  are shown. Analog output circuit  136  receives PWM signal  116  from buffer  152  and includes optical isolators  128  and  130 , integrator  132 , and switch  134 . When output circuit  120  operates in analog output mode, analog output circuit  136  provides analog output signal  140  to an output system or device (not shown) coupled to output terminals  196  and  198 .  
         [0047]     In the illustrated embodiment, in order to configure output circuit  120  to operate in analog output mode, BOC signal  118  (not shown) is set to a TTL “low.” PWM signal  116  is received by optical isolators  128  and  130 . PWM signal  116  is also coupled to diode  186  via buffer  162 , such that it is inverted. The gate of transistor  190  is coupled to diode  186  via resistor  188 . When PWM signal  116  is a TTL “low,” transistor  190  is “ON.” Accordingly, switch  134  provides analog output signal  140  to an output system or device (not shown) coupled to output terminals  196  and  198 .  
         [0048]     According to an exemplary embodiment, PWM signal  116  is a time-optimized pulse width modulated signal that is used to generate analog output signal  140 . When output circuit  120  is configured to operate in analog output mode, PWM signal  116  is received by optical isolators  128  and  130 . Optical isolators  128  and  130  couple PWM signal  116  to integrator  132  via buffer  162  and resistor  164 . Integrator  132  then provides analog output signal  140  to switch  134 , which provides analog output signal  140  to an output system or device (not shown) coupled to output terminals  196  and  198 .  
         [0049]      FIG. 4  schematically illustrates a simplified version of output circuit  120  in which the circuit components that are not used in binary output mode have been removed and the components of binary output circuit  138  are shown. Binary output circuit  138  receives BOC signal  118  from buffer  150  and includes optical isolator  124  and triac  126 . When output circuit  120  operates in binary output mode, binary output circuit  138  provides binary output signal  142  to an output system or device (not shown) coupled to output terminals  196  and  198 . In binary mode, BOC signal  118  is used to provide current to the optically controlled driver of triac  126 , which in turn provides gate current to triac  126 .  
         [0050]     In order to configure output circuit  120  to operate in binary output mode, PWM signal  116  (not shown) is set to 0 percent modulation. BOC signal  118  is set to TTL “high” and is coupled to the anode of optical isolator  124  through resistor  158 . Optical isolator  124  is “ON” and accordingly couples BOC signal  118  to triac  126  via resistor  160  such that triac  126  is opened and closed according to BOC signal  118  to provide binary output signal  142  to an output system or device (not shown) coupled to output terminals  196  and  198 .  
         [0051]     According to the illustrated embodiment, analog output circuit  136  and binary output circuit  138  share output terminals  196  and  198 . Analog output circuit  136  is protected from high voltage spikes when output circuit  120  is configured to operate in binary output mode by voltage regulating device  192 . Further, the inputs to operational amplifier  172  are protected when the device is in binary output mode by dual diode  194 . Dual diode  194  limits the voltage at the input of operational amplifier  172  by clamping it to the 5 volt supply.  
         [0052]     In typical applications and installations (e.g., an electrical device in a controlled system), electrical devices using output device  10  are installed (e.g., mounting and wiring of the electrical device(s)) and configured (e.g., initiation, powering-up, programming, testing, etc.) by different persons (e.g., having different expertise and/or negotiated responsibilities). For example, in a new construction installation, a first person (such as an electrician) mounts or installs the device and connects the wiring. Thereafter, a second person (such as a building, systems, or HVAC engineer) can program, reprogram, initiate, power-up or otherwise have operational control over HVAC system.  
         [0053]     The device with the configurable output may be a general device configured for a variety of applications and systems, which would have an unknown input characteristic (e.g., analog or binary). This general device may be configured according to the application. Alternatively, while the system is being configured, tested, and/or powered-up, it may become desirable to add an additional controlled device. If necessary, the configurable output can be configured to be compatible with this additional controlled device. Alternatively, after the installation and initial configuration, it may become desirable to modify or expand the controlled system. Such modification may require a different output. An engineer or other technician can configure the output accordingly.  
         [0054]      FIG. 5  schematically illustrates a configurable output circuit  220  according to another exemplary embodiment. Table III below provides exemplary values for the circuit of  FIG. 5 .  
                                       Component               Reference   Quantity   Description                   U1   1   IC, OPTO ISOLATOR, SP646 SCR       R11-R12   2   RES, 281 OHM, 1%, 1/16 W 200 PPM       C1   1   ELEC, 22 UF, 16 V, TR, 20%,‘40 + 105       J1   1   S-BLOCK, 1 × 10, OMIS, FS, SCREW TERMINAL       VR1   1   MOV, 68 V, 56 V, 100 A, TR       U3-U4   2   IC, OptoCoupler, TLP621       Q1-Q2   2   MMBTA56, DRIVER, PNP, S3       U2   1   IC_OperationalAmplifier_Quad_LM2902_SO14       U5   1   IC, VOLTAGE REF. TL431       U7   1   IC&lt;Digital. TriState-Quad Buffer, CMOS, SO14, MC74HC125AD       D1   1   Diode, Switching, 100 V, 25 nA, 225 mW, 1N4148, SOT23       R14   1   RES, 499 OHM, 1%, 1/8 W 200 PPM       DS1   1   LED_Red_Diffused_2.6 mcd @ 20 mA_155_1206       R1-R8   8   RES, 10 K, 1% .0625 W, THK 100 PPM       R9-R10   2   RES, 47.5 K, 1% .0625 W, THK 100 PPM       R13   1   RES, 4.99 K OHM, 1%, 1/16 W 200 PPM       U6   1   IC, DIGITAL, 74AHC1G14, SCHMITT TRIGGER INVERTER,               SINGLE GATE, CMOS, SMT; SOT23-                    
         [0055]      FIG. 6  schematically illustrates a configurable output circuit  320  according to an exemplary embodiment. Output circuit  320  differs from output circuit  120  (shown in  FIG. 2 ) in that output circuit  320  is self-configuring. Output circuit  320  receives a single PWM input signal that is either a PWM signal for a binary output or a PWM signal for an analog output. Output circuit  320  selects binary output mode if a PWM signal for a binary output is received, or analog output mode if a PWM signal for an analog output is received.  
         [0056]      FIG. 7  illustrates a block diagram of a control system  410  including a configurable output circuit  420  according to an exemplary embodiment. Control system  410  may be any type of control system. For example, in one embodiment, control system  410  is an industrial control system such as a heating, ventilating, and air-conditioning (HVAC) system. Control system  410  includes an output system or device  412 , and provides a reset signal  414 , a mode control signal  416 , and a device control signal  418  to output circuit  420 .  
         [0057]     Output system or device  412  is coupled to output circuit  420 . Output system or device  412  may be a lighting system, a mechanical actuator, a fan, a temperature control system, or any other type of output device. Output system or device  414  may also be a microprocessor-based system that accepts the output signal from output circuit  410  as an input signal, digitizes the input signal, and uses the input signal for microprocessor-based control of output device  414 . As another example, output device  414  may be an electromechanical actuator that has a state which is directly controlled by the signal from the output circuit  410 . In one embodiment, output system or device  412  is configured to accept an analog output signal  440  from output circuit  420 . In another embodiment, output system or device  412  is configured to accept a binary output signal  442  from output circuit  420 .  
         [0058]     Reset signal  414  is provided by system  410  (e.g., from a computer or other device capable of configuring or reconfiguring output control circuit  420 ) to set mode control signal  416  and device control signal  418  to known states during, for example, a system reset. Mode control signal  416  is provided by system  410  to configure (or reconfigure) output circuit  420  to operate in an analog output mode or in a binary output mode. For example, in one embodiment, mode control signal  416  is a transistor-transistor logic (TTL) signal which provides a TTL “high” signal to configure output circuit  420  to operate in analog output mode, or a TTL “low” signal to configure output circuit  420  to operate in binary mode. Mode control signal  416  may be provided by system  410  to output circuit  420  in a variety of ways. In one embodiment, mode control signal  416  is provided by an operator using software. In another embodiment, mode control signal  416  is provided by any of a variety of inputs, such as computing device (e.g., a laptop, personal digital assistant (PDA), etc. that may be permanently or temporarily coupled to the output circuit  420 ), or the like. According to another embodiment, mode control signal  416  is set or configured during installation. In another embodiment, mode control signal  416  is configured (or reconfigured or modified) after installation. In one embodiment, configuring (or reconfiguring) of mode control signal  416  is done by an operator (e.g., technician, engineer, etc.). In another embodiment, configuring (or reconfiguring) is done by another system in communication with output circuit  420 .  
         [0059]     Device control signal  418  is provided by system  410  (e.g., from a system controller configured to control output system or device  412 ) as a control signal which is the basis for either a binary or analog output signal to be provided to output system or device  412 . For example, in one embodiment device control signal  418  is pulse width modulated (PWM) signal which output circuit  410  processes into either an analog output signal or a binary output signal. Device control signal  418  provides a control signal which is the basis for either analog output signal  440  or binary output signal  442 . Device control signal  418  may be generated by any of a variety of controllers, such as a microprocessor-based controller, the output of an A/D or D/A converter, the output of a potentiometer, or the like.  
         [0060]     Output circuit  420  is configured to be coupled to output system or device  412 , and may be incorporated into system  410  in a number of ways. For example, output circuit  420  may be may be included in any of a variety of electrical or electronic apparatuses or subsystems used within system  410 . In one embodiment, an electronic controller within system  410  includes one or more configurable output circuits  420 . In another embodiment, the controller is configured to provide one or more fixed (or “hard-wired”) outputs and one or more output circuits  420 . Such devices (with configurable outputs) are intended to be more flexible during installation (e.g., connectable to systems or devices not known when device  412  was manufactured; to provide future adaptability to add or change systems or devices connected to device  412 ; or the like).  
         [0061]     Output circuit  420  includes a buffer  422 , a switch  424 , an optical switch/relay  426 , optical isolators  428  and  430 , an integrator  432 , and a switch  434 . Output circuit  420  receives reset signal  414 , mode control signal  416 , and device control signal  418  as inputs. Output circuit  420  is subdivided into an analog output circuit  436  and a binary output circuit  438 . Output circuit  420  is capable of being configured (e.g., using software during installation or during a later modification) to provide an analog output mode or a binary output mode depending on the type or characteristics of output system or device  412 . In the analog output mode of operation, output circuit  420  provides an analog output signal  440  to output system or device  412 . In the binary output mode of operation, output circuit  420  provides a binary output signal  442  to output system or device  412 .  
         [0062]     Buffer  422  is configured to receive reset signal  414 , mode control signal  416 , and device control signal  418  as inputs. Buffer  422  is further configured to isolate the sources (not shown) of reset signal  414 , mode control signal  416 , and output device control signal  418  by, for example, minimizing impedance effects from output circuit  10 . Buffer  422  is also configured to allow reset signal  414  to set mode control signal  416  and device control signal  418  to a known state during, for example, a system reset.  
         [0063]     Switch  424 , included in binary output circuit  438 , is coupled to buffer  422  and to optical switch/relay  426  and is configured to receive mode control signal  416  and device control signal  418  from buffer  422 . Switch  424  is a transistor or other suitable electronic switching device. Switch  424  operates to couple device control signal  418  to optical switch/relay  426  in response to output mode control signal  426 .  
         [0064]     Optical switch/relay  426 , included in binary output circuit  438 , is coupled to switch  424  and output system or device  412 . Optical switch/relay  426  is configured to receive device control signal  418  from switch  424  and to provide binary output signal  442  to output system or device  412  in response to device control signal  418 . Optical switch/relay is also configured to optically isolate output system or device  412  from the source of each input (not shown) to output circuit  420  to, for example, prevent electrical damage to each source. For example, in one embodiment, output system or device  412  is an alternating current (AC) device, and optical switch/relay  420  is configured to switch an AC power source according to device control signal  418  (e.g., a PWM signal) while optically isolating the source of device control signal  418  from the AC power source.  
         [0065]     Optical isolators  428  and  430 , included in analog output circuit  436 , are coupled to buffer  422 . Optical isolator  428  is further coupled to integrator  432  and is configured to receive device control signal  418  from buffer  422  and to provide device control signal  418  to integrator  432 . Optical isolator  428  is also configured to optically isolate output system or device  412  from the source of each input (not shown) to output circuit  420  to, for example, prevent electrical damage to each source. Optical isolator  430  is further coupled to switch  434  and is configured to receive mode control signal  416  from buffer  422  and to provide mode control signal  416  to switch  434 . Optical isolator  430  is also configured to optically isolate output system or device  412  from the source of each input (not shown) to output circuit  420  to, for example, prevent damage electrical damage to each source.  
         [0066]     Integrator  432 , included in analog output circuit  436 , is coupled to optical isolator  428  and to switch  434 . Integrator  432  is configured to receive device control signal  418  from optical isolator  428  and to provide an analog output signal  440  to switch  434  that is based on device control signal  418  as received from optical isolator  428 .  
         [0067]     Switch  434 , included in analog output circuit  436 , is coupled to optical isolator  430 , integrator  432 , and output system or device  412 . Switch  424  is a transistor or other suitable electronic switching device. Switch  434  is configured to receive analog output signal  440  from integrator  432 , as well as mode control signal  416  from optical isolator  430 , and to provide analog output signal  440  to output system or device  412  in response to mode control signal  426 .  
         [0068]     Output circuit  420  is configured to receive mode control signal  416  and device control signal  418 , and to processes device control signal  418  according to the configuration of output circuit  420  indicated by mode control signal  416 . Output circuit  420  then provides the processed output signal to output device  412 . Depending on the configuration of output circuit  420  as determined by mode control signal  416 , device control signal  418  is processed as an analog output signal  440  using analog output circuitry  30 , or a binary output signal  442  using binary output control circuitry  432 . For example, where output circuit  420  is configured to operate in analog output mode, switch  424  is “OFF” according to mode control signal  416 , and device control signal  418  is received by optical isolator  428 . Optical isolator  428  provides device control signal  418  to integrator  432 , which then provides analog output signal  440  based on control signal  418  to switch  434 . Switch  434  is “ON” according to mode control signal  416 , and provides analog output signal  440  to output system or device  412 . Where output circuit  420  is configured to operate in binary mode, device control signal  418  is received by switch  424 , which is “ON” while switch  434  is “OFF” according to mode control signal  416 . Switch  424  then provides a signal to optical switch/relay  426 , which provides binary output signal  442  to output system or device  412 .  
         [0069]      FIG. 8  schematically illustrates a configurable output circuit  720  which is an alternative embodiment of output circuit  420  shown in  FIG. 7 . Output circuit  720  receives reset signal  714 , mode control signal  716 , and device control signal  718  as inputs, and includes a buffer  722 , a switch  724 , an optical switch/relay  726 , optical isolators  728  and  730 , an integrator  732 , and a switch  734 . Output circuit  720  is subdivided into an analog output circuit  736  (shown in  FIG. 9 ) and a binary output circuit  738  (shown in  FIG. 10 ). In analog output mode, analog output circuit  736  provides analog output signal  740 . In binary output mode, binary output circuit  738  provides binary output signal  742 .  
         [0070]     Table I below provides exemplary input and output signal ratings for output circuit  720 .  
                                                             Symbol   Parameter   Value   Units                                Device   Pulse Width Modulated (PWM) Device Control Signal               Control   Maximum frequency   1200   Hz           Minimum input signal   3.15   V       Mode Control   Mode Control Signal           Minimum Input High Level   3.15   V       System   System Reset Signal       Reset   Maximum Input Low Level   1.35   V       AO/BO   Analog Output Signal/Binary Output Signal           Maximum Output Voltage: analog output, binary output   10, 36   V           Maximum Output: analog output, binary output   10, 500   mA           Maximum Surge Current (binary output 10us)   5   A           Maximum Blocking Voltage (binary output)   400   V       15 VI   15 V Isolated Power Supply   14.25 to   V               15.75       5 VI   5 VI Isolated Power Supply (5 VI isolated power supply   4.75 to   V           derived from 15 VI using voltage reference)   5.05       Power   Maximum Power Dissipation:       Dissipation   Analog Output   735   mW           Binary Output   1961   mW                  
 
         [0071]     Table II below provides exemplary component values for output circuit  720 .  
                                                     Component               Reference   Quantity   Description                                U1   1   IC, Opto Isolated Solid State Relay, SP646 SCR       R11,R12   2   Resister, 680 Ohm, 1%, 1/16 W, 200 PPM       C1   1   Elec, 22 UF, 16 V, TR, 20%, −40 + 105       VR1   1   Mov, 68 V, 56 V, 100 A, TR       U3,U4   2   Ic Opto Coupler, ISD202 ISOCOM DIP 8 Pins       Q1,Q2   2   MMBTA56, Driver, PNP, S3       Q3,Q4   2   FET, FDN5618P, P-Channel       U2   1   Ic_Operational Amplifier_Quad_LM2902_SO14       U5   1   IC, Voltage Ref. TL431       U7   1   IC, Digital TnState-Quad Buffer, CMOS, SO14, MC74HC125AD       D1,D2,D3   3   Diode, Switching, 100 V, 25 nA, 225 mW, 1N4148, SOT23       R14,R15   2   Resisters, 340 Ohm, 1%, 1/16 W, THK 100 PPM       DS1   1   LED_GreenDifused_2.6 mcd @ 20 mA_155_1206 (LED lamp)       R1-R8   8   Resisters, 10 K, 1%, 1/16 W, THK 100 PPM       R9,R10   2   Resister, 47.5 KOhm, 1%, 1/16 W, 200 PPM       R13   1   Resister, 4.99 KOhm, 1%, 1/16 W, 200 PPM       U6   1   IC, Digital, 74AHC1G14, Schmitt Trigger Inverter, Single Gate,               CMOSSMT, 50T23-5                  
 
         [0072]     Buffer  722  includes buffers  750  and  752 . In one embodiment, buffers  750  and  752  are part of a single integrated circuit (IC) package. In another embodiment, buffers  750  and  752  are separate ICs. Buffer  750  receives mode control signal  716  and system reset signal  714  as inputs. Buffer  750  is coupled to switch  724  via resistor  754 , and to optical isolator  730  via resistor  756  such that switch  724  and optical isolator  730  receive mode control signal as an input. Buffer  750  receives device control signal  718  and system reset signal  714  as inputs. Buffer  752  is coupled to switch  724 , and optical isolator  728  via resistor  758  such that switch  724  and optical isolator  728  receive device control signal  718  as an input.  
         [0073]     Switch  724 , included in binary output circuit  738 , includes transistor  764 . The drain of transistor  764  is coupled to buffer  752  such that it receives device control signal  718 , while the source of transistor  764  is coupled to optical switch/relay  726  via resistor  765 . The gate of transistor  764  is coupled to buffer  750  via resistor  754  such that it receives mode control signal  716 .  
         [0074]     Optical switch/relay  726 , included in binary output circuit  738 , is configured to receive device control signal  718  from switch  724  and to provide binary output signal  742  to an output system or device (not shown) coupled to output terminals  796  and  798  in response to device control signal  718 . In the illustrated embodiment, optical switch/relay  724  is an optically isolated solid state relay. In this embodiment an optically isolated relay is used in order to isolate device control signal  718  from an AC output device (not shown) coupled to output circuit  720  without the slow speed and short life of the contacts associated with mechanical relays.  
         [0075]     Optical isolator  728 , included in analog output circuit  736 , is coupled to buffer  752  via resistor  758  such that it receives device control signal  718  as an input. Optical isolator  728  is further coupled to integrator  732  via buffer  766  and resistor  768  such that it provides inverted device control signal  718  to integrator  732 . Optical isolator  730 , included in analog output circuit  736 , is coupled to buffer  750  via resistor  756  such that it receives mode control signal  716  as an input. Optical isolator  730  is further coupled to switch  734  via resistor  770  such that it provides mode control signal  716  to switch  734 .  
         [0076]     Integrator  732 , included in analog output circuit  736 , includes operational amplifier  772 , capacitor  774 , and resistors  776 ,  778 , and  780 . In the illustrated embodiment, capacitor  774  and resistors  776 ,  778 , and  780  are selected such that integrator  732  has a time constant of about 1.045 seconds. In another embodiment, other values may be selected. Integrator  732  is coupled to optical isolator  728  via inverter  766  and  768  such that it receives inverted device control signal  718  as an input to non-inverting input of operational amplifier  772 . Integrator  732  is further coupled to switch  734  and is configured to provide a time averaged version of inverted device control signal  718  to switch  734  in the form of analog output signal  740 .  
         [0077]     Switch  734 , included in analog output circuit  736 , includes transistor  782 . The drain of transistor  782  is coupled to integrator  732  such that it receives analog output signal  740  from integrator  740 . The source of transistor  782  is coupled to output terminal  796  and to integrator  732  via diode  784  such that switch  734  provides analog output signal  740  to an output system or device (not shown) coupled to output terminals  796  and  798 , as well as to integrator  732  as a feedback signal. The gate of transistor  782  is coupled to optical isolator  730  via resistor  770  such that it receives mode control signal  716  as an input.  
         [0078]      FIG. 9  schematically illustrates a simplified version of output circuit  720  in which the circuit components that are not used in analog output mode have been removed and the components of analog output circuit  736  are shown. Analog output circuit  736  receives mode control signal  716  and device control signal  718  from buffer  722  and includes optical isolators  728  and  730 , integrator  732 , and switch  734 . When output circuit  720  operates in analog output mode, analog output circuit  736  provides analog output signal  740  to an output system or device (not shown) coupled to output terminals  796  and  798 .  
         [0079]     In the illustrated embodiment, in order to configure output circuit  720  to operate in analog output mode, mode control signal  716  is set to a TTL “high.” Mode control signal  716  is received by optical isolator  730 , which couples mode control signal  716  to the gate of transistor  782  via resistor  770 . Mode control signal  716  is also coupled to transistors  786  and  788  via diode  790 . Transistors  786  and  788  selectively couple AC return  794  to isolated ground  795  in response to mode control signal  716 . When mode control signal  716  is a TTL “high,” transistors  782 ,  786 , and  788  are “ON.” Accordingly, AC return  794  is coupled to isolated ground  795  and switch  734  provides analog output signal  740  to an output system or device (not shown) coupled to output terminals  796  and  798 .  
         [0080]     Device control signal  718  is a time-optimized PWM signal that is used to generate analog output signal  740 . When output circuit  720  is configured to operate in analog output mode, device control signal  718  is received by optical isolator  728 . Optical isolator  728  couples device control signal  718  to integrator  732  via inverter  766  and resistor  768 . Integrator  732  then provides analog output signal  740  to switch  734 , which provides analog output signal  740  to an output system or device (not shown) coupled to output terminals  796  and  798 .  
         [0081]      FIG. 10  schematically illustrates a simplified version of output circuit  720  in which the circuit components that are not used in binary output mode have been removed and the components of binary output circuit  738  are shown. Binary output circuit  738  receives mode control signal  716  and device control signal  718  from buffer  722  and includes switch  724  and optical switch/relay  726 . When output circuit  720  operates in binary output mode, binary output circuit  738  provides binary output signal  742  to an output system or device (not shown) coupled to output terminals  796  and  798 . In binary mode, the pulse width modulated signal (PWM) is used to close the normally open solid state relay U 1 .  
         [0082]     In order to configure output circuit  720  to operate in binary output mode, mode control signal  716  is set to a TTL “low.” Device control signal  718  is a PWM signal and is coupled to the drain of transistor  764 . Switch  724  is “ON” and accordingly couples device control signal  718  to optical switch/relay  726  via resistor  765  such that the normally open solid state relay is opened and closed according to device control signal  718  to provide binary output signal  742  to an output system or device (not shown) coupled to output terminals  796  and  798 .  
         [0083]     In the illustrated embodiment, binary output circuit also includes light emitting diode (LED)  760  and resistor  762 . LED  760  and resistor  762  are connected in series between the output of buffer  750  and the output of buffer  752 . When mode control signal  716  is a TTL “low” and output circuit  720  is operating in binary mode, LED  720  is ON whenever device control signal  718  is a TTL “high.” LED  760  is preferably bright enough to be seen in a ceiling or remote mounting location.  
         [0084]     According to the illustrated embodiment, analog output circuit  736  and binary output circuit  738  share output terminals  796  and  798 . Analog output circuit  736  is protected from high voltage spikes when output circuit  720  is configured to operate in binary output mode by voltage regulating device  792 . Further, the connection between AC return  794  and isolated digital ground  795  is broken via transistors  786  and  788  when the device is in binary output mode.  
         [0085]     In typical applications and installations (e.g., an electrical device in a controlled system), electrical devices using output device  10  are installed (e.g., mounting and wiring of the electrical device(s)) and configured (e.g., initiation, powering-up, programming, testing, etc.) by different persons (e.g., having different expertise and/or negotiated responsibilities). For example, in a new construction installation, a first person (such as an electrician) mounts or installs the device and connects the wiring. Thereafter, a second person (such as a building, systems, or HVAC engineer) can program, reprogram, initiate, power-up or otherwise have operational control over HVAC system.  
         [0086]     The device with the configurable output may be a general device configured for a variety of applications and systems, which would have an unknown input characteristic (e.g., analog or binary). This general device may be configured according to the application. Alternatively, while the system is being configured, tested, and/or powered-up, it may become desirable to add an additional controlled device. If necessary, the configurable output can be configured to be compatible with this additional controlled device. Alternatively, after the installation and initial configuration, it may become desirable to modify or expand the controlled system. Such modification may require a different output. An engineer or other technician can configure the output accordingly.  
         [0087]     It is also important to note that the construction and arrangement of the elements of the configurable output as shown in the preferred and other exemplary embodiments are illustrative only. Although only a few embodiments of the present invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, the configurable output circuit  10  may be used in many different types of devices and packages. As such, the environmental characteristics are defined and adaptable on a device-by-device basis. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and/or omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present invention as expressed in the appended claims.