Abstract:
Apparatus, systems and methods for correcting data received from a power cable is presented. A method receives communication data from a near end of a cable that has near and far ends. The data is compared using hysteresis to a high threshold and/or a low threshold. The data is reset to produce corrected data by resetting the data to either a high value or a low value based on the comparing. For example, when the corrected data is high, the data is reset to a low value when the communication data crosses the low threshold and when the corrected data is low, the data is reset to a high value when the communication data crosses the high threshold. The corrected data can provide a power supply data needed so that it can more accurately provide a power through the cable to the far end of the cable.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Application Ser. No. 61/617,907, filed Mar. 30, 2012; the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The current invention relates generally to apparatus, systems and methods for charging and/or supplying power to electronic items. More particularly, the apparatus, systems and methods relate to charging and/or supplying power to electronic items on display in a commercial setting. Specifically, the apparatus, systems and methods provide for charging and/or supplying power to electronic items with the use of advanced techniques to compensate for cable loss. 
     2. Description of Related Art 
     Merchants often desire displaying powered-up electronic devices to consumers so that the consumers can handle and explore the various functions of different electronic devices. For example, a merchant may wish to display a variety of different cellular phones so that consumers can handle and evaluate the functionality of each phone. Alternatively, merchants may desire displaying cameras, computer-related devices, electronic games and the like powered-up to allow handling and exploration of these devices. 
     A display that exhibits electronic items will often show several different electronic items. Traditional power supplies for these types of displays would provide a central power supply that would supply power to each electronic device through a corresponding power cable attached between each electronic device and the central power supply. The central power supply in general supplied one main voltage level to each power cable so that each electronic device needed to be able to accept the same voltage level. Alternatively, voltage converters could be used to convert the main voltage to different voltage levels; however, converters add substantial cost to the powering system and take up additional space. Also, today&#39;s electronic devices often require high currents, which increase the voltage loss in the power cable and connectors and result in a significant difference between the voltage supplied by the power supply and what is expected by the electronic device. What is needed is a better way to supply power to electronic items on display in a commercial setting. 
     SUMMARY OF THE INVENTION 
     One example embodiment of the invention includes a method for correcting data received via a power cable. A method may include receiving communication data from a near end of a cable that has near and far ends. The communication data can be data representing a measured voltage at the far end of the cable. The method may also include comparing the communication data, possibly using hysteresis, to a reference threshold, a high threshold, and/or a low threshold. The data may be reset to produce corrected data by resetting the data to either a high value or a low value based on the comparing. For example, when the corrected data is high, the data may be reset to a low value when the communication data crosses the low threshold and when the corrected data is low, the data may be reset to a high value when the communication data crosses the high threshold. In some embodiments, the high threshold can be set so that the high threshold is higher than the low threshold. The corrected data can provide data to a power supply so that the power supply can more accurately provide power through the cable to the far end of the cable. 
     Another configuration of an example embodiment includes a system for supplying power to a cable. The system includes a cable with a near end and a far end, a comparator located at the near end of the cable, a controller located at the far end of the cable, an inverting device, a voltage input device, a single communication wire, and another wire. The comparator can be an operational amplifier (op-amp). The voltage input device may be located at the far end of the cable to input a voltage into the controller. The single communication wire may be located between the comparator and the inverting device and the wire may be between the inverting device and the controller. The controller may communicate data to the inverter which may invert the data to create inverted data. The comparator may compare the inverted data to at least one reference voltage and generate corrected data based, at least in part, on the comparison of the inverted data to the at least one reference voltage. The cable communicates the corrected data to a power supply at the near end of the cable so that the power supply can supply a power through the cable to the far end of the cable that is accurate at the far end of the cable. 
     In some configurations, the system can include biasing elements to create hysteresis at the comparator between the inverted data and at least one reference voltage, The hysteresis can be implemented using a low threshold and a high threshold. When the corrected data is high, the comparator will not transition the corrected data low until the inverted data goes below the low threshold. When the corrected data is low, the comparator will not transition the corrected data high until the inverted data goes above the high threshold, 
     In yet another configuration, the system can include a voltage measurement device at the far end of the cable for creating a far end voltage value representing the voltage at the far end of the cable. The controller may transmit the far end voltage value over the wire between the inverting device and the controller and the single communication wire to the comparator where it is compared to one or more reference voltages and is adjusted. The power supply then supplies the corrected power through the cable to the far end of the cable that has been corrected based, at least in part, on the far end voltage value. 
     Other configurations of some example embodiments can include other useful devices and features. For example, the system can include a low voltage dropout (LDO) regulator to stabilize the voltage at an analog-to-digital converter (ADC) in the controller that is used to sample the voltage (e.g., power) at the far end of the cable. The system could include a Schottky diode and a capacitor that is used to maintain a high voltage value when the single communication wire is driven low so that the controller has a steady power supply. The inverting device could be a bipolar junction transistor (BJT) with its gate connecting the wire to the controller, its emitter connected to the single communication wire, and its collector connected to ground. 
     In another configuration of an example embodiment, a system, for example for receiving a noisy signal from a power cable, may include comparator logic circuitry, amplification logic circuitry, and a power supply. The comparator logic circuitry may compare a received communication signal received from a power cable to a reference signal. The amplification logic circuitry may amplify the received signal to a corrected output signal that is high when the received communication signal is greater than the reference signal. Similarly, the amplification logic amplifies the received signal to a corrected output signal that is low when the received communication signal is less than the reference signal. This system can send the corrected output signal to the power supply where the corrected output signal may be decoded so that the power supply can adjust a power that the power supply is supplying to the power cable. 
     In some configurations, this system can have biasing elements configured to create hysteresis between the reference signal and the received communication signal using a low threshold and a high threshold. When the corrected output signal is high, the corrected output signal will not go low until the received communication signal goes below the low threshold. When the corrected output signal is low, the corrected output signal will not go high until the received communication signal goes above the high threshold. The low threshold and the high threshold can be separated by at least one volt or another voltage. A first pair of biasing resistors can be connected in series and the reference voltage can be the voltage between the resistors. A second pair biasing resistors can be used with feedback from the corrected output signal used to bias the received communication signal. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       One or more example embodiments that illustrate the best mode(s) are set forth in the drawings and in the following description. The appended claims particularly and distinctly point out and set forth the invention. 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example methods, and other example embodiments of various aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale. 
         FIG. 1  illustrates an example embodiment of a power supply system. 
         FIG. 2  illustrates an example schematic of an example embodiment of a power supply system. 
         FIG. 3  illustrates an example graph of how hysteresis effects signal Vcomm-in that is input into the power supply. 
         FIG. 4  illustrates an example embodiment of a method of adjusting the communication signal of a power supply cable. 
     
    
    
     Similar numbers refer to similar parts throughout the drawings. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example embodiment of a power supply system The system  1  provides power to merchandise items  2  displayed at a display cabinet  4  or another type of suitable display at a retail establishment. In  FIG. 1 , the merchandise items  2  are shown as cameras, however, other merchandise items  2  can be powered by the power supply system  1 . For example, the system  1  can power electronic devices such as cellular phones, computers, electronic games and the like. A power supply unit  3  provides power to one or more of the merchandise items  2  through one or more cables  5 . The merchandise items  2  may also be secured to a display stand that provides theft deterrence and prevention, for example, by including an audible and/or visual alarm that is triggered by cutting or disconnecting a cable  5  from a merchandise item  2 . 
     “Logic”, as used herein, includes but is not limited to hardware, firmware, software and/or combinations of each to perform a function(s) or an action(s), and/or to cause a function or action from another logic, method, and/or system. For example, based on a desired application or need, logic may include a software controlled microprocessor, discrete logic like an application specific integrated circuit (ASIC), a programmed logic device, a memory device containing instructions, or the like. Logic may include one or more gates, combinations of gates, or other circuit components. Logic may also be fully embodied as software. Where multiple logical logics are described, it may be possible to incorporate the multiple logical logics into one physical logic. Similarly, where a single logical logic is described, it may be possible to distribute that single logical logic between multiple physical logics. Building on the forgoing, “logic circuitry” refers to specialized hardware that is specially manufactured to perform desired functionality (e.g., an ASIC, FPGA, etc.) or general purpose hardware (e.g., a processor) that is specially configured via the implementation of software or firmware to perform desired functionality. 
       FIG. 2  illustrates some example features and components of an example embodiment of a schematic of a circuit  200  for adjusting the voltage of a signal (V comm ) communicated on a power cable to a power supply  202 . The power supply is configured to supply power over a cable containing conductors +PS and −PS to a load device  210  such as an electronic device on display at a retail display as shown in  FIG. 1 . Each conductor +PS and −PS is shown with a loss resistor Rcable that simply models the line loss of each of these cables and that is not actually a resister in the circuit  200  illustrated in  FIG. 2 . An operational amplifier (op-amp)  204  and resistors R 1 , R 2 , R 3 , R 4  are configured to clean up a communication signal Vcomm sent from microcontroller  208  using transistor  212 . The Schottky diode  214 , low voltage dropout (LDO) regulator and capacitor C are configured to generate a very clean voltage for an analog-to-digital (ND) conversion inside the microcontroller  208 . 
     For easy viewing and understanding, the components of  FIG. 2  are illustrated as being distributed widely between the power supply  202  and the load  210 . However, in some example embodiments, the op-amp  204  and resistors R 1 , R 2 , R 3 , R 4  may be located at the near end  216  of the cable at the power supply  202 , and in some embodiments they would be located inside the power supply  202  itself. The transistor  212 , Schottky diode  214 , low voltage dropout (LDO) regulator  206 , capacitor C and the microcontroller  208  are located at the far end  218  of the cable at the load  210 . Thus, a three wire cable with conductors/wires +PS, −PC and Vcomm would span between these two cable ends. 
     Having described the components and structure of the example circuit  200  for adjusting the voltage of a signal (Vcomm) communicated by the microcontroller, its operation and functionality are now discussed. In operation, the power supply  202  supplies the op-amp  204  and the collector of the transistor  212  with a nominal +5 voltage. The Schottky diode  214  and the capacitor C act to store energy in the capacitor C when the emitter of the transistor  212  is turned on as discussed further below. The voltage on the AID converter inside the microcontroller  208  is used for the reference voltage of A/D converter. Therefore, the low voltage dropout (LDO) regulator  206  is used to generate a very accurate voltage that is input to LDO_in of the microcontroller  208 . In this configuration, a 3.6 volt precision voltage reference/WO regulator  206  is used. Using this precision voltage regulator allows for the elimination, or at least the minimization, of line losses and an accurate voltage measurement can be obtained by load voltage sense resistors R 6 , R 7 . 
     The operation of the op-amp  204  will now be discussed ignoring the hysteresis biasing resistors R 1 , R 2 , R 3 , R 4  for the moment and assuming they create a theoretical ideal comparison reference voltage of 2.5 volts at the inverting input V− of the op-amp  204 . In operation, the microcontroller  208  occasionally needs to communicate with the power supply  202  and does so by transmitting serial data over the Vcomm wire between the transistor  212  and the microcontroller  208  and the Vcomm-inv between the transistor  212  and resistor R 3 . The microcontroller  208  communicates by sending binary 1s and 0s (represented as 5 volts and 0 volts respectively) over Vcomm to the gate node of the transistor  212 . 
     First, the transmission of a 0 from the microcontroller  208  is discussed and then the transmission of sending a 1 from the microcontroller  208  is discussed. When the microcontroller  208  transmits a 0 (0 volts/low value) to the transistor  212 , this will not turn on the gate so that the voltage of the emitter of the transistor  212  remains high which means Vcomm-inv is high. Ideally, this high voltage will be 5 volts so that the V+ input of the op-amp  204  is also 5 volts. The op-amp  204  compares this voltage (5 volts) to the reference voltage at V− input (2.5) and determines that a 1 (high value) has been transmitted over Vcomm-inv and drives a 5 volt signal (a high level) into the Vcomm-in input of the power supply  202 . If for some reason there were line losses, as well as noise on the Vcomm and Vcomm-inv lines, the voltage received at the V+ input of the op-amp  204  could be, for example, 3.8 volts. Because 3.8 volts is still greater than the reference voltage at V− (which is 2.5 volts), the op-amp  204  still correctly drives a 5 volt signal into the Vcomm-in input of the power supply  202 . 
     When the microcontroller  208  transmits a 1 (5 volts/high value) to the transistor  212 , this is more than enough voltage to turn on the transistor  212  to cause current to flow between its emitter and collector. Releasing this current causes Vcomm-inv to go to 0 volts (ground). Now, when the op-amp  204  compares this voltage (0 volts) to the reference voltage at V− input (2.5) it determines that a 0 (low value) has been transmitted over Vcomm-inv and drives a 0 volt signal (a low level) into the Vcomm-in input of the power supply  202 . If for some reason there was noise as well as other parasitic disturbances on the Vcomm and Vcomm-inv lines, the voltage received at the V+ input of the op-amp  204  could be, for example, 1.5 volts. Because 1.5 volts is still less than the reference voltage at V− (which is 2.5 volts), the op-amp  204  still correctly drives a 0 volt signal into the Vcomm-in input of the power supply  202 . In summary, as long as a 0 value arrives at the op-amp  204  below 2.5 volts and a high arrives above 2.5 volts, the op-amp  204  will always correctly detect the right value and drive the correct low value (0 volts) or correct high value (5 volts) to the power supply&#39;s Vcomm-in input. 
     The four transistors R 1 , R 2 , R 3 , R 4  can add hysteresis to the comparisons that the op-amp  204  performs between its V+ input and its reference voltage (V−). For example, when R 1 =10 k ohms, R 2 =15 k ohms, R 3 =10 K ohms and R 4 =50 k ohms, this biases the op-amp  204  so that the low voltage threshold voltage (Vth low) is 2.5 volts and the high threshold voltage (Vth high) is 3.5 volts. In other words a high voltage has to go lower than 2.5 volts before the op-amp drives a low value to the power supply  202  (the same as above). On the other hand, a low voltage now has to get to 3.5 volts (one voltage above 2.5 volts) before the op-amp  204  will switch from driving a low value (0 volts) to the power supply  202  and begin driving a high value (5 volts) to the power supply  202 . Therefore, there can be more noise on a low signal without causing a false transition of a high signal. 
       FIG. 3  illustrates how the op-amp operates with hysteresis wherein the low voltage threshold voltage (Vth low) is 2.5 volts and the high threshold voltage (Vth high) is 3.5 volts. In this illustration, a noise spike on Vcomm-inv was encountered that reached a high point  302 , however, this spike only reached about 1.8 volts which is below Vth-high so there was no transition from low to high on the value output from the op-amp to power supply input Vcomm-in, Later, Vcomm-inv does rise to 3.5 volts at point  304  which causes the op-amp to drive a high value (5 volts) to Vcomm-in. This value stays high until that point  306  Vcomm-inv crosses the 2.5 volt level causing the op-amp  204  to switch the value it is driving to the Vcomm-in from a high value to a low value. This value remains low even when a rather large noise spike  308  is later encountered, because the noise never reached Vth-high, 3.5V. 
     As understood by those of ordinary skill in the art, the resistors R 1 , R 2 , R 3 , R 4  can be other values. For example, when R 1 =10 k ohms, R 2 =12.2 k ohms, R 3 =10 K ohms and R 4 =40 k ohms, this biases the op-amp  204  so that the Vth-low is 2.0 volts and the high threshold voltage Vth-high is 3.44 volts. 
     Example methods may be better appreciated with reference to flow diagrams. While for purposes of simplicity of explanation, the illustrated methodologies are shown and described as a series of blocks, it is to be appreciated that the methodologies are not limited by the order of the blocks, as some blocks can occur in different orders and/or concurrently with other blocks from that shown and described. Moreover, less than all the illustrated blocks may be required to implement an example methodology. Blocks may be combined or separated into multiple components. Furthermore, additional and/or alternative methodologies can employ additional, not illustrated blocks. 
       FIG. 4  illustrates a method  400  recovering a noisy signal received at a far end of a power cable. For example, the cable may be a 3-wire cable as discussed above with two power conductors and a single communications wire. The method begins by transmitting, at  402 , an original communications signal at a far end of the power cable to a near end of the cable. As discussed above, a microcontroller desiring to communicate with a power supply can generate a signal that turns a transistor on or off to create an inverted signal that is transmitted across the cable to its near end. 
     The received communication signal at the near end of the cable is compared, at  404 , to a reference signal using hysteresis. As discussed above, the signal can be compared and then recovered, at  406 , using hysteresis. Hysteresis provides that when a prior signal is high, a low signal is not considered received until the received signal crosses a low threshold. Similarly, when a prior signal is low, a high signal is not considered received until the received signal crosses a high threshold. The recovered signal is then sent to logic, at  408 , where it is decoded. For example, the recovered signal that is now accurate signal/data that can represent power requirements at the far end the cable can be sent to a power supply where it can control/inform the power supply about power requirements at the far end of the cable so that the power supply can better supply a more accurate power to the far end of the cable for delivery to the near end of the cable. 
     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. Such terms are used for descriptive purposes and are intended to be broadly construed. Therefore, the invention is not limited to the specific details, the representative embodiments, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. 
     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described. References to “the preferred embodiment”, “an embodiment”, “one configuration”, “one example”, “an example”, and so on, indicate that the embodiment(s) or example(s) so described may include a particular feature, structure, characteristic, property, element, or limitation, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element or limitation. Furthermore, repeated use of the phrase “in the preferred embodiment” does not necessarily refer to the same embodiment, though it may.