Abstract:
A power supply approach and mechanism for electrical devices using a polarity-insensitive two-wire bus that can carry data and power. However, some devices, such as CO2 sensors and secure digital memory cards, may need certain amounts of energy for measuring and writing data, respectively, that are more intense than the amount of energy available on the two-wire bus. Sensor, card and other device data may be conveyed by the two-wire bus. The present approach and mechanism may convert power from the two-wire bus into intense energy that can enable the sensors, cards and other devices to satisfactorily operate. A current limiter may be incorporated to protect the two-wire bus from loss of data and energy for slave devices on the bus during a period of charging a storage cell in that an empty huge storage capacitor connected to bus directly could short the bus.

Description:
BACKGROUND 
       [0001]    The present disclosure pertains to power supplies and particularly to power supplies designed for providing certain kinds of outputs. 
       SUMMARY 
       [0002]    The disclosure reveals a power supply approach and mechanism for electrical devices using a polarity-insensitive two-wire bus that can carry data and power. However, some devices, such as CO2 sensors and secure data or digital memory cards, may need amounts of energy for measuring and/or writing data, respectively, that are more intense than the amount available on the two-wire bus. Data for the sensors may be conveyed by the two-wire bus. The present approach and mechanism may convert power from the two-wire bus into a form of energy that can enable the sensors and cards to satisfactorily to measure and/or write data. A current limiter may be incorporated to protect the two-wire-bus from loss of data and energy for slave devices on the bus during a period of charging of the storage cell in that an empty huge capacitor connected to bus directly could totally short the bus. The present approach and mechanism may be applicable to other electrical devices that utilize the two-wire bus for conveying data but need more intense energy than is available on the bus to operate adequately. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0003]      FIG. 1  is a diagram of a module having a two-wire connection and a sub-module for providing extra power to the module when needed; 
           [0004]      FIG. 2  is a diagram showing circuit details of the module in  FIG. 1 ; and 
           [0005]      FIG. 3  is a functional block diagram of a DC to DC converter. 
       
    
    
     DESCRIPTION 
       [0006]    The present approach and mechanism 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. 
         [0007]    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. 
         [0008]    The present approach may solve an issue of many wires needed for having features like CO2, humidity, temperature measurement, LCD and buttons user interface and secure digital card writing available on a two-wire sylk sensor system. 
         [0009]    Wiring for a multi-point transfer today may require up to eight wires running and terminating at one or more sensors. Sylk™ (sylk) bus technology may be available from Honeywell International Inc. and may allow virtually all of the point information to be sent on just two polarity insensitive wires thereby saving installation time, wiring errors and materials. But a drawback may be the limited amount of instantaneous energy available from the sylk bus to the sensor. To date, applications like CO2 measurement and secure digital (SD) card writing have not necessarily been possible to offer on the sylk bus, because of a lack of quick presence of energy when needed. 
         [0010]    A two-wire bus approach may be described in U.S. Pat. No. 7,966,438, issued on Jun. 21, 2011, and entitled “Two-Wire Communications Bus System”. U.S. Pat. No. 7,966,438, issued on Jun. 21, 2011, is hereby incorporated by reference. 
         [0011]    Marketing may have labeled the two-wire approach as “game changing”. The approach is possible by incorporating a new current limited power supply circuit to charge a local capacitor/storage cell. An onboard microcontroller may monitor the voltage in the storage cell and calculate when there is sufficient energy in the cell to conduct an energy intensive action like a CO2 measurement or writing of a flash memory. 
         [0012]      FIG. 1  is a diagram of an example two-wire mechanism, module, approach or device  10  that may have a sub-module  11 . The module or device may be for a CO2 or some other sensor or electronic function requiring energy intensive action. Sub-module or circuit  11  may incorporate an electromagnetic compatibility (EMC) protection circuit  23 , a polarity protection (e.g., a rectifier) circuit  24  and a data and power splitter  25 . An output  18  from sub-module  11  may go to a current limiter  12 . An output  19  may go from current limiter  12  to a storage capacitor circuit  13 . An output  19  may go from capacitor  13  to a DC-DC converter  14 . Power sub-module  11  may have a connection with a sylk bus  16  to provide power and a data. Data may be taken from a splitter circuit  25 . A power connection may be made from power sub-module  11  to current limiter  12 . 
         [0013]      FIG. 2  is a diagram that shows more details of mechanism, module, approach or device  10  of  FIG. 1 . A sylk bus connector  16  may have two conductors  21  and  22  connected to an ECM protection circuit  23 . Conductors  21  and  22  of the sylk bus may convey power and data signals to sylk module  11 . EMC protection circuit  23  may have a spark gap  26  across conductors or lines  21  and  22 . A 100 pico farad capacitor  27  and a varistor  28  may be connected across lines  21  and  22  in circuit  23 . 
         [0014]    Lines  21  and  22  may proceed through circuit  23 . Circuit  23  may have a full-wave rectifier for providing polarity protection. An output line  31  may be connected to an anode of a diode  33  of splitter circuit  25 . Data may be picked off at terminal  17  connected to the anode of diode  33 . Power from a cathode of diode  33  may proceed along a line  18  to an input of current limiter  12 . Line  32  from circuit  24  to splitter  25  may be regarded as a common reference terminal or ground for circuit  25 , current limiter  12 , storage capacitor  13 , and DC-DC converter  14 . 
         [0015]    Line  18  may be connected to a collector of an NPN transistor  34 , a first end of a 4.75K ohm resistor  35 , a first end of a 100K ohm resistor  36 , and a first terminal of a 0.1 microfarad capacitor  37 . A second terminal of capacitor  37  may be connected to line  32 . A second end of resistor  36  may be connected to a cathode of a zener diode  38  and a base of an NPN transistor  39 . An anode of zener diode  38  may be connected to line  32 . Zener diode  38  is not necessarily needed for a current limiter but may provide additional voltage protection to prevent a voltage higher than the 16 volts on storage capacitor  43  having, for instance, a rating of 8200 micro farads at 16 volts. 
         [0016]    A second end of resistor  35  may be connected to a collector of transistor  39 . An emitter of transistor  39  may be connected to a base of transistor  34  and to a cathode of a three terminal zener diode  41  having a low voltage rating and sharp characteristics. An emitter of transistor  34  may be connected to a first end of a 110 ohm resistor  42 . A second end of resistor  42  may be connected to an anode of zener diode  41  and to an output line  19  of current limiter  12 . A third terminal of zener diode  41  may be connected to the cathode of diode  41 . 
         [0017]    Lines  19  and  32  from current limiter  12  may go to a storage capacitor circuit  13 . Line  19  may be connected to a positive terminal of an 8,200 microfarad polarity sensitive capacitor  43 . A negative terminal of capacitor  43  may be connected to line  32 . Three one micro farad capacitors  44 ,  45  and  46  may be connected in parallel with capacitor  43 . Output lines  19  of storage capacitor circuit  13  may be connected to a DC to DC converter  14  voltage regulator integrated circuit (IC)  48 . Circuit  48  may be a TPS54060 chip available from, for example, certain vendors of Texas Instruments products. 
         [0018]    The discrete circuitry supporting IC  48  may be as shown in  FIG. 2  or modified for a particular use. An example as shown for converter circuit  14  may have line  19  connected to a terminal  52  for a voltage in to IC  48 . Line  32  may be connected to ground terminals  59  and  61  of IC  48 . 
         [0019]    A 200K ohm resistor  71  may have a first end connected to line  19  and a second end connected to an EN (enable) terminal  53  of IC  48 . A 47.5K ohm resistor  72  may have a first end connected to terminal  53  and a second end connected to line  32 . A 200K ohm resistor  73  may have a first end connected to a RT/CLK (timing resistor and external clock) terminal  55  and a second end connected to line  32 . A 0.1 micro farad capacitor  74  may have a first terminal connected to an SS/TR (slow start and tracking) terminal  54  of IC  48  and a second terminal connected to line  32 . 
         [0020]    A 53.6K ohm resistor  75  may have a first end connected to a COMP (compensation) terminal  58  of IC  48 . A second end of resistor  75  may be connected to a first terminal of a 0.001 micro farad capacitor  76 . A second terminal of capacitor  76  may be connected to line  32 . A 12 pico farad capacitor  74  may have a first terminal connected to terminal  58  of IC  48  and a second terminal connected to line  32 . A 53.6 ohm resistor  78  may have a first end connected to a PWRGD (power good) terminal  56  of IC  48 , and a second end connected to line  32 . 
         [0021]    A 0.1 micro farad capacitor  79  may have a first terminal connected to a BOOT (bootstrap voltage) terminal  51  and a second terminal connected to a PH terminal  60  of IC  48 . A first terminal of a 100 micro henry inductor  81  may have a first terminal connected to terminal  60  and a second terminal connected to a V DCDC  output terminal  80 . A zener diode  82  may have a cathode connected to terminal  60  and an anode connected to line  32 . 
         [0022]    A 61.9K ohm resistor  83  may have a first end connected to terminal  80  and a second end connected to a VSENSE (voltage sense) terminal  57  of IC  48 . A first end of a 9.53K ohm resistor  84  may have a first end connected to terminal  57  and a second end connected to line  32 . 
         [0023]    A 0.1 micro farad capacitor  85  may have a first terminal connected to terminal  80  and a second terminal connected to line  32 . A polarity sensitive 100 micro farad capacitor  86  may have a positive terminal connected to terminal  80  and a negative terminal connected to line  32 . 
         [0024]      FIG. 3  is a Texas Instruments Inc. (TI) functional block diagram  90  of IC  48 . Pin numbers (i.e., in the small square tabs) in diagram  90  plus a number  50  may correspond to pin numbers for IC  48  in  FIG. 2 , e.g., pin number  4  (SS/TR) of diagram  90  plus  50  equals pin number  54  (SS/TR) of IC  48 . 
         [0025]    Some of the less common parts in diagram  80  may be noted. Varistor  28  may clamp a voltage in both directions, such as an AC voltage, whereas a zener diode may clamp a voltage in just one direction. Varistor  28  may have a part number V56MLA1206NH and be available a from a Littlefuse parts vendor. Full wave rectifier  24  may be a diode bridge HD04-T available from Diodes Inc. or a Schottky diode bridge MB16S from Micro Commercial Components. Diode  33  may have a part number 1N4148W-13 and be available from a Diodes Incorporated parts vendor. Component  33  may have a reverse recovery time of four nanoseconds. Transistors  34  and  39  may have a part number MMBT3904LT1 and be available from a Motorola parts vendor. Zener diode  38  may have a part number MMSZ4703 and be available from a General Semiconductor parts vendor. Diode  41  may have a part number LM431BIM3 and be available from a National Semiconductor parts vendor. Diode  41  may be an adjustable precision zener shunt regulator. Diode  82  may have a part number 10BQ060 and be available from a Sensitron Semiconductor parts vendor. Component  82  may be a Schottky rectifier. 
         [0026]    To recap, a power supply for a two-wire bus connected electrical module, may incorporate a protection circuit having an input for connection to a two-wire bus, a data and power splitter connected to the protection circuit, a current limiter connected to the data and power splitter, a energy storage cell connected to the current limiter, and a DC to DC converter connected to the energy storage cell. An output of the DC to DC converter may provide more intense energy per unit of time than the two-wire bus. 
         [0027]    The protection circuit may incorporate an electromagnetic compatibility protection sub-circuit and a polarity protection sub-circuit. 
         [0028]    The energy storage cell may incorporate a capacitor having a value greater than one microfarad. 
         [0029]    The electromagnetic compatibility protection sub-circuit may incorporate a spark gap and a varistor. 
         [0030]    The polarity protection sub-circuit may incorporate a rectifier. 
         [0031]    The data and power splitter may incorporate a diode having an anode connected to an output of the polarity protection sub-circuit and a cathode connected to an input of the current limiter. 
         [0032]    The current limiter may incorporate one or more transistors, and one or more zener diodes to limit a rate of flow of current to the energy storage cell. 
         [0033]    The DC to DC converter may be selected from a group consisting of step-down regulators and buck converters. 
         [0034]    An electrical input from the two-wire bus to the protection circuit may incorporate a first magnitude of energy for a first duration of time. An electrical output from the DC to DC converter may incorporate a second magnitude of energy for a second duration of time. The second magnitude of energy may be greater than the first magnitude of energy. The first duration of time may be greater than the second duration of time. 
         [0035]    A mechanism for providing energy to a device, may incorporate a two-wire bus capable of providing power and data, an electromagnetic compatibility and polarity protection circuit connected to the two-wire bus, a splitter for extracting data from the two-wire bus, a storage capacitor, a current limiter for limiting an amount of current from the splitter to the storage capacitor, and a DC-DC converter for providing an electrical energy supply having greater intensity than the electrical energy supply available on the two-wire input. 
         [0036]    The data on the two-wire bus may be from a CO2 module. The electrical energy supply from the DC-DC converter may be for sufficiently powering the CO2 module in a measurement mode. The energy supply on the two-wire bus may often be insufficient for the CO2 module in a measurement mode. 
         [0037]    The data on the two-wire input may be for a secure digital card. The energy supply from the DC-DC converter may be for sufficiently powering the secure digital card in a writing mode. The energy supply on the two-wire bus may often be insufficient for the secure digital card in a writing mode. 
         [0038]    The mechanism may further incorporate a controller connected to the storage capacitor. The controller may monitor a voltage at the storage capacitor and calculate when there is enough energy in the storage capacitor to provide an amount of intensive energy for operating a certain electrical device, or the controller may ensure an initial time period for storing energy in the storage capacitor to provide enough intensive energy for operating a certain electrical device without the controller monitoring the voltage at the storage capacitor. Energy from the two-wire bus may incorporate an insufficient amount of intensive energy for operating a certain electrical devices. 
         [0039]    An approach for providing data and power relative to an electrical device, may incorporate providing a two-wire bus for conveying power and data, connecting a splitter to the two-wire bus for obtaining data from the two-wire bus, limiting current from the two-wire bus going to a storage cell, and monitoring an amount of energy in the storage cell to determine when there is a sufficient amount of energy to enable an energy intensive action by an electrical device. 
         [0040]    The amount of energy in the storage cell may be monitored by a controller measuring a voltage at the storage cell and calculating when there is a sufficient amount of energy in the storage cell to enable an energy intensive action by the electrical device. 
         [0041]    The approach may further incorporate providing electromagnetic compatibility protection between the two-wire bus and the splitter. 
         [0042]    The approach may further incorporate protecting the splitter or the storage cell from incorrect electrical polarities on the two-wire bus. 
         [0043]    The approach may further incorporate performing a DC to DC conversion of electrical energy from the storage cell to a greater amount of energy per a smaller duration of time that available from the storage cell. 
         [0044]    The electrical device may be selected from a group consisting of sensors and memories. 
         [0045]    The two-wire bus is a polarity insensitive bus. 
         [0046]    In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
         [0047]    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.