Abstract:
Techniques for duplex communication and power transfer across an isolator are provided. In an example, a first transceiver coupled to a firs-t side of an isolator can include a transmit modulator configured to receive first data and timing signals, to provide control signals to oscillate an output of the transceiver to transmit power and to order each half-cycle of an oscillation cycle of the output to transmit the first data. A second transceiver coupled to a second side of the isolator can include a receive detection circuit configured to compare a received oscillation cycle with a plurality of thresholds and to provide a plurality of comparator outputs indicative of reception of the positive half-cycle and the negative half-cycle, and a receive decoder configured to identify the order of half-cycles and to provide an output indicative of logic level of the first data.

Description:
CLAIM OF PRIORITY 
       [0001]    This patent application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 62/244,058, entitled, “CIRCUITS, SYSTEMS, AND METHODS FOR SIMULTANEOUSLY TRANSMITTING DATA SIGNALS, TIMING INFORMATION AND POWER THROUGH A TRANSFORMER”, filed on Oct. 20, 2015, which is hereby incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This document pertains generally, but not by way of limitation, to isolation circuits and systems, and more particularly to isolation circuits and systems that allow power transfer and duplex communications via an isolation device. 
       BACKGROUND 
       [0003]    Many applications require transmission of one or more of data, timing information or power between a first system and a second system, where the second system is designed to be isolated from the first system. In some cases, one or more of these types of signals may need to be transmitted in both directions between the two systems. Conventional approaches can transmit each of these types of signals using a separate isolator such as a transformer. However, these approaches are inefficient in terms of use of resources and provide corresponding poor performance. Therefore, a need exists for circuits, systems and methods to transmit one or more of data, timing information or power between isolated systems in a more efficient manner and with higher performance. 
       SUMMARY 
       [0004]    The present inventors have recognized apparatus and methods for transferring power, clock and data between two isolated systems using a single isolation transformer. In addition, certain examples can allow full duplex data communication between the isolated systems using the single isolation transformer. In certain examples, the system can use a three-level coding scheme of positive and negative half-cycle waveforms and pauses. The pauses can separate the individual waveforms from each other such that the individual waveforms can be detected and decoded by the receiving circuit. Transmitted data, such as bit-values can be encoded by the transmitting circuit modulating a phase of the transmitted positive and negative half-cycle waveforms. In certain examples, one side of the isolation device can include circuitry to rectify at least a portion of the received signals and provide a power supply rail. 
         [0005]    This overview is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views, Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, hut not by way of limitation, various embodiments discussed in the present document. 
           [0007]      FIG. 1  illustrates generally an example system for transferring power, a clock signal and duplex data communication between two isolated systems using a single isolation transformer. 
           [0008]      FIG. 2  illustrates generally a block diagram example of a first communication circuit. 
           [0009]      FIG. 3  illustrates generally a block diagram example of a second communication circuit. 
           [0010]      FIGS. 4A and 4B  illustrate generally signals that can be generated by the first communication circuit. 
           [0011]      FIGS. 5A-5D  illustrate generally example current signal waveforms that include data generated by the first communication circuit and data generated by the second communication circuit. 
           [0012]      FIG. 6  illustrates generally an example circuit for the first communication circuit. 
           [0013]      FIG. 7  illustrates generally an example circuit for the second communication circuit. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  illustrates generally an example system  100  for transferring power, a clock signal (CLK 1 ) and duplex data communication between two isolated communication circuits  101 ,  102 , or transceivers, using a single isolation device  103 . The system  100  can include a first communication circuit  101 , a second communication circuit  102  and an isolation device  103 . In certain examples, the isolation device, or isolator, can include an isolation transformer  103  or the windings or antennas of a near field communication system. Other isolation devices are also possible without departing from the scope of the present subject matter and can include, but are not limited to, an inductive isolator, an optical isolator, a capacitive isolator, or combinations thereof. 
         [0015]    In certain examples, the first communication circuit  101  can transmit a clock signal (CLK 1 ) and a first data signal (DIN 1 ) to the second communication circuit  102 , and the second communication circuit  102  can transmit a second data signal (DIN 2 ) to the first communication circuit  101 . The second communication circuit  102  can receive and decode the transmitted signal of the first communication circuit  102  to provide a first received data signal (DOUT 2 ) and a first received clock signal (CLK 2 ). The first communication circuit  101  can receive and decode the transmitted data signal from the second communication circuit  102  and can provide a second received data signal (DOUT). In certain examples, the first communication circuit can receive power from a first voltage source (VS 1 ) and the transmission signal of the first communication circuit  101  can provide power for a power supply (VS 2 ) of the second communication circuit  102  as well as other components that may be associated with the second communication circuit  102 . In certain examples, the power supply (VS 2 ) of the second communication circuit  102  can be realized by rectifying the received signal and, in some examples, storing charge of the rectified signal on a battery or a capacitor. In certain examples, the exchange of data, the clock and power can all happen simultaneously or in a full duplex type mode as simultaneous transmission and reception is sometimes referred. 
         [0016]      FIG. 2  illustrates generally a block diagram example of a first communication circuit  201 . The first communication circuit  201  can include an input to receive power from a first power supply (VS 1 ), a transmit timing circuit  211 , a transmit encode circuit  212 , a driver circuit  213 , a receive detection circuit  214  and a receive decode circuit  215 . The transmit timing circuit  211  can receive a system clock (CLK 1 ) and provide timing signals for the transmit encode circuit  212  and the receive decode circuit  215 . The transmit encode circuit  212  can receive a data signal (DIN 1 ) and can provide encode command signals to the driver circuit  213 . The driver circuit  213  can receive the encode command signals and can generate and encode data on a cycle of an oscillatory transmit signal. In certain examples, one or more clock signals can be encoded with the transmit signal in either the frequency of each oscillatory cycle, including pauses between each cycle or in the frequency of each oscillatory cycle. 
         [0017]    The receive detection circuit  214  can monitor loading of the transmit signal and generate encoded receive data signals based on the transmit signal loading. The receive decode circuit  215  can receive the encoded receive data signals from the receive detection circuit  214  and can provide a data output (DOUT 1 ) using the encoded receive data signals and a clock signal received from the transmit timing circuit  211 . 
         [0018]      FIG. 3  illustrates generally a block diagram example of a second communication circuit  302 . The second communication circuit  302  can include a receive detection circuit  321 , a receive decode circuit  322 , a clock recovery circuit  323 , a data encode circuit  324  and a rectifier circuit  325 . The receive detection circuit  321  can be coupled to and can receive waveforms from the isolator  103 . The receive detection circuit  321  can generate waveform information and pass the waveform information to the receive decode circuit  322 . The receive decode circuit  322  can use the wave form information to decode the data transmitted from the first communication circuit and can pass detection information to the clock recovery circuit  324 . The clock recovery circuit  324  can use the detection information to generate a recovered clock signal (CLK 2 ) and associated delays that can be used for clock recovery such as delays associated with the clock pulse width for example. The data encode circuit  324  can receive input data (DIN 2 ) and can generate rectification control commands using the clock signal (CLK 2 ) encode data on the waveforms. The rectifier circuit  325  can receive the rectification commands and can load the isolator  103  to encode the input data on the waveforms of the isolator  103 . In certain examples, the rectifier circuit  325  can transfer charge induced in the isolator  103  to provide a power supply (VS 2 ) for the second communication circuit  302 . 
         [0019]      FIGS. 4A and 4B  illustrate generally signals that can be generated by the first communication circuit. The signals can transmit data, clock information and power in certain examples. With respect to data,  FIGS. 4A and 4B  each include a single cycle of an oscillating signal preceded by a pause and followed by a pause. The difference between the signal of  FIG. 4A  and the signal of  FIG. 4B  is the phase pattern of the cycle. Thus, the signal of  FIG. 4A  can illustrate a data bit having a first state and the signal of  FIG. 4B  illustrates a data bit having a second state. The second communication circuit can employ detection logic to detect a received cycle and decode logic to determine the phase pattern of the cycle. In certain examples, the system clock of the first communication circuit initiates each data bit transmission. Therefore, the second communication circuit includes logic to recover the clock signal by detecting, for example, a particular point of each received half-cycle. The signal waveforms of  FIGS. 4A and 4B  illustrate the voltage waveforms as they may appear at each side of the isolator. 
         [0020]      FIGS. 5A-5D  illustrate generally example current signal waveforms that include data generated by the first communication circuit and data generated by the second communication circuit. The second communication system can generate a data bit state by loading the signal generated by the first communication system. In certain examples,  FIGS. 5A and 5B  illustrate current of the primary side of the isolator representing different loadings of a positive and negative polarity of the data signal to generate a first data state of a data bit, e.g., a selected one of a 1 or 0, from the second communication circuit back to the first communication circuit when the first communication circuit transmits a positive into negative voltage pulse or a negative into positive voltage pulse, respectively.  FIGS. 5C and 5D  illustrate current of the primary side of the isolator representing different loadings of the positive and negative polarities of the data signal to communicate a second data state, e.g., the other of the 1 or 0, from the second communication circuit back to the first communication circuit, when the first communication circuit transmits a positive into negative pulse or a negative into positive pulse, respectively. Consequently,  FIGS. 5A-5D  illustrate waveforms that can simultaneously communicate data information (full duplex) between the first communication circuit and the second communication circuit through a single isolator, such as a single transformer having a single, first, or primary, winding and a single, second, or secondary, winding, for example. 
         [0021]      FIG. 6  illustrates generally a circuit diagram for an example first communication circuit  601 . As discussed above with reference to  FIG. 2 , the first communication circuit  601  can include an input to receive power from a first power supply (VS 1 ), a transmit timing circuit  611 , a transmit encode circuit  612 , a driver circuit  613 , a receive detection circuit  614  and a receive decode circuit  615 , The combination of the transmit timing circuit  611 , the transmit encode circuit  612  and the driver circuit  613  can sometimes be referred to as a transmitter or transmit modulator. The combination of the receive detection circuit  614  and the receive decode circuit  615  can sometimes be referred to as a receiver. 
         [0022]    In certain examples, the driver circuit  613  can generate a cyclical signal to drive the isolation element  103 . In certain examples, the driver circuit  613  can include four switches (S 1 , S 2 , S 3 , S 4 ) to supply current from a power supply (VS 1 ), for example, to a first winding of an isolation transformer  103 . When the first and fourth switches (S 1 , S 4 ) are close, current can pass through the first winding in a first direction to generate, for example, a positive half-cycle. When the second and third switches (S 2 , S 3 ) are closed simultaneously, current can pass through the first winding in a second direction to generate, for example, a negative half-cycle. In some examples, the driver circuit  613  can include optional inverting or non-inverting drivers to buffer the command signals or to provide proper driving control signals for the switches (S 1 , S 2 , S 3 , S 4 ). 
         [0023]    The transmit timing circuit  611  can receive a system clock (CLK 1 ) and can provide timing signals for initiating a cycle transmission using the driver circuit  613 , for timing the cycle and for receiving data from the second communication circuit. In certain examples, a frequency of the system clock (CLK 1 ) can be commensurate with a bit frequency of the first communication circuit  601 . In an example, the transmit timing circuit  613  includes two one-shots, an AND-gate and a XOR-gate. In general the transmit timing signals generate a first pulse from the AND-gate followed by a second pulse from the XOR gate. Each pulse has a duration (t). The first pulse is initiated on a rising edge of the clock signal (CLK) and the second pulse in initiated on the second edge of the first pulse. In the illustrated example, the rising edge of the clock can initiate a rising edge of the first timing pulse from the AND-gate. Upon the expiration of the first one-shot, the first timing pulse can transition from a high logic state to a low logic state. The falling edge of the first timing pulse can initiate a rising edge of the second timing pulse from the output of the XOR-gate. Upon the expiration of the second one-shot, the second timing pulse can transition from the high logic level to a low logic level. 
         [0024]    The transmit encode circuit  612  can receive the data (DIN 1 ) of the first communication device and the timing signals of the transmit timing circuit  611  and can provide the control signals for the driver circuit  613  such that when the data input to the transmit encode circuit is in a first state the positive and negative half-cycles can be transmitted in a first sequence and when the data input to the transmit encode signal is in a second state the positive and negative half-cycles can be transmitted in a second, opposite sequence. As is discussed below, the second communication circuit can decode the data transmitted from the first communication circuit by determining the half-cycle order of each received cycle. In certain examples, the transmit encode circuit  612  can include a latch, a four of AND-gates and two NOR gates. In certain examples, the latch can include a D flip-flop to receive and hold the logic level of the data of the first communication device. The AND-gates and NOR-gates can be arranged as shown to encode the order of the half-cycles of each transmitted cycle according to the logic level of the output of the latch. As illustrated in the example of  FIG. 4 , a high data logic level can be represented in a transmitted cycle with a positive half-cycle followed by a negative half-cycle ( FIG. 4A ) and a low data logic level can be represented in a transmitted cycle with a negative half-cycle followed by a positive half-cycle ( FIG. 4B ). 
         [0025]    The receive detection circuit  614  can include a pair of current sensors and a corresponding pair of comparator amplifiers. The second communication circuit can communicate data to the first communication circuit  601  by loading the isolation transformer  103  while the first communication circuit  603  is transmitting data. The loading of the isolation transformer  103  can be detected by detecting a change, such as an increase, in current on the first winding of the isolation transformer  103 . As such, the pair of current sensors detect current of the first winding. The first current sensor can detect first winding current during a positive half-cycle and the second current sensor can detect first winding current during a negative half-cycle. Each of the comparator amplifiers can receive a threshold (vth) indicative of the transition between the first winding being loaded and not loaded. The first comparator can provide an output indicative of whether the positive half-cycle was loaded by the second communication circuit and the second comparator can provide an output indicative of whether the negative half-cycle was loaded by the second communication circuit. Valid data transferred from the second communication circuit to the first communication circuit is detected when, simultaneously, the voltage at one terminal of the isolator is lower than the threshold voltage and the voltage at the other terminal of the isolator is higher than the threshold voltage. 
         [0026]    The receive decode circuit  615  of the first communication device  603  can receive a timing signal from the transmit timing circuit  611  and the outputs from the comparators of the receive detection circuit  614  and can provide the logic level of the data (DOUT 2 ) received from the second communication circuit. In certain examples, the receive decode circuit  615  can include an first latch, such as an RS latch, and a second latch. The first latch can receive the outputs of the receive detection circuit and can capture which half-cycle of the transmitted cycle of the first communication circuit was loaded by the second communication circuit. The output of the first latch can be received by the second latch and latched to the output of the receive decode circuit using the timing signal received from the transmit timing circuit. 
         [0027]      FIG. 7  illustrates generally an example circuit diagram of an example second communication circuit  702 . As discussed above with reference to  FIG. 3 , the second communication circuit  702  can include a receive detection circuit  721 , a receive decode circuit  722 , a clock recovery circuit  723 , a data encode circuit  724  and a rectifier circuit  725 . The second communication circuit  702  can receive power, data and a clock signal from the first communication signal via an isolation device such as an isolation transformer  103 . 
         [0028]    In certain examples, the rectifier circuit  725  can include a rectifier  726  and a load circuit  727 . The rectifier  726  can include a pair of diodes that can transfer charge from the second winding of the isolation transformer and store the charge on a power supply (VS 2 ). The power supply (VS 2 ) can include for example a capacitor or a battery for powering at least the second communication circuit  702 . A first diode can transfer charge to the power rail (VS 2 ) during a positive half-cycle of a received transmission from the first communication circuit and a second diode can transfer charge to the power supply (VS 2 ) during a negative half-cycle of a received transmission from the first communication circuit. The load circuit  727  of the rectifier circuit  725  can allow the second communication device  702  to transmit data to the first communication device by selectively loading the second winding of the isolation transformer  103 . In certain examples, the load circuit  727  can include a pair of diodes and a pair of switches. Control of the switches of the load circuit  727  is discussed below. 
         [0029]    The receive detection circuit  721  can include four comparator circuits for detecting amplitude levels of each half-cycle of a received cycle transmission from the first communication device. Two of the comparators detect the logic level of a positive half-cycle and two comparators detect the logic level of a negative half-cycle. The illustrated example includes a two pairs of comparators to detect signal voltage on the second side of the isolator  103 . Each pair of comparators can detect that a signal is above or below a low threshold (v thl ) and above or below a high threshold (v thh ). For purposes of the present subject matter, the combination of one pair of comparators detecting the voltage above the high threshold (v thh ) and the other pair of comparators detecting the voltage below the low threshold (v thl ) can provide the minimum information for receiving data and recovering a clock at the second communication circuit  702 . It is understood that the four comparators of the receive detection circuit  721  can provide additional information including information about noise or differential voltages of the second winding of the isolator among other things. 
         [0030]    The receive decode circuit  722  can receive the output of the receive detect comparators and can use a first logic array to indicate whether a logic level of the positive half-cycle was high or not and whether the logic level of the negative half-cycle was high or not. A second logic array can receive the outputs of the first logic array and can provide two outputs indicative of when the each half-cycle is received. In certain examples, the first logic array can include two pairs of logic gates with each pair including an AND-gate and a NOR-gate. The first pair of logic gates can receive the outputs of the two comparators that detect the logic level of the positive half-cycle, and the second pair of logic gates can receive the outputs of the two comparators that detect the logic level of the negative half-cycle. In certain examples, the second logic array can include a pair of AND gates. A first AND-gate of the pair of AND-gates can receive an output from each of the pair of gates of the first logic array. A first input of the first AND-gate can be coupled to an output of the AND-gate of the first pair of gates of the first logic array and a second input of the first AND-gate can be coupled to an output of the NOR-gate of the second pair of gates of the first logic array. A first input of the second AND-gate of the second logic array can be coupled to an output of the NOR-gate of the first pair of gates of the first logic array and a second input of the second AND-gate can be coupled to an output of the AND-gate of the second pair of gates of the first logic array. In certain examples, the output of the first AND-gate of the second logic array can indicate the logic level of the data received from the first communication circuit and the output of the second AND-gate of the second logic array can provide a complimentary indication the logic level of the data received from the first communication. In general, the outputs of the receive decode circuit are actively providing an indication of the received waveform during reception of the received waveform on the second winding of the isolation transformer and are inactive between transmissions of the first communication circuit. 
         [0031]    The clock recovery circuit  723  can provide a first output indicative of the received data (DOUT 2 ) and a second output indicative of the recovered system clock (CLK 2 ) at the first communication device. Recapturing the clock signal can assist in timing the transmission of data from the second communication device  702 . In certain examples, the clock recovery circuit  723  can include a latch, an OR-gate and a one-shot. In certain examples, the latch can receive either output of the received decode signal and latch it so the data is available to other processing circuitry associated with the second communication circuit. In the illustrated example of  FIG. 7 , the output of the first AND-gate of the second logic array of the received decode circuit is received at a D-latch of the clock recovery circuit. The OR-gate of the clock recovery circuit can receive the output of each AND-gate of the second logic array of the received decode circuit. Such an arrangement can provide at least the leading edge of the recovered clock signal because at least one of the inputs to the OR-gate triggers at each clock cycle. The output of the OR-gate can be provided to the latch of the clock recovery circuit to clock the latch. The output of the OR-gate can also be provided as an input to the one-shot of the clock recovery circuit. The one-shot of the clock recovery circuit provides a feedback input to the OR-gate to maintain the output of the OR-gate for a predetermined interval. In certain examples, the frequency of the system clock of the first communication system is known and the predetermined interval of the one-shot of the clock recovery circuit can be for example, one half of the period of the system clock. Such an interval can produce a clock signal with a 50% duty cycle. It is understood that other one-shot intervals are possible without departing from the scope of the present subject matter. 
         [0032]    Control of the switches of the load circuit  727  can be based on control signal received from the data encode circuit  724 . In certain examples, the data encode circuit  724  includes a latch, such as a D-flip-flop. Data (DIN 2 ) can be received at an input of the latch and moved to the outputs of the latched when triggered by the recovered clock signal (CLK 2 ). The outputs of the latch can provide the control signals for the switches of the load circuit  727 . In certain examples, when a switch of the load circuit is activated, the switch can complete a circuit that couples the second side of the isolator to ground via a diode, such as a Zener diode. When the voltage on the winding breaks down the Zener diode junction, the second side of the isolator is loaded and increased current demand on the first side of the isolator can indicate the loading. Detecting the increased current demand on the first side of the isolator  103  can allow the duplex transfer of data across the isolator  103 . 
         [0033]    It is understood that the logic circuit examples of the figures discussed above are one example implementation of the functions discussed, and that upon reading and understanding the functions performed other logic circuit implementations are possible that can perform the described functions without departing from the scope of the present subject matter. 
       Additional Notes 
       [0034]    The above description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. 
         [0035]    In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls. 
         [0036]    In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
         [0037]    Geometric terms, such as “parallel”, “perpendicular”, “round”, or “square”, are not intended to require absolute mathematical precision, unless the context indicates otherwise. Instead, such geometric terms allow for variations due to manufacturing or equivalent functions. For example, if an element is described as “round” or “generally round,” a component that is not precisely circular (e.g., one that is slightly oblong or is a many-sided polygon) is still encompassed by this description. 
         [0038]    Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like. 
         [0039]    The above description is intended to be illustrative, and not restrictive. For example, the above-described examples or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure, It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.