Patent Description:
Electrical devices in many contexts include a communication system to send information between a transmitter and a receiver that are galvanically isolated and are hence referenced to different ground potentials. Examples include power converters, medical equipment, marine equipment, and the like. The communications channel in such communication system can be implemented using an inductive coupling like a signal transformer. Like other transformers, signal transformers can transfer electrical energy across galvanic isolation. In general, signal transformers are designed to minimize leakage inductance and stray capacitance and thereby improve highfrequency response. For example, the windings of a signal transformer can be split into sections and interleaved.

Switching power converters generally convert an input into a regulated output for a load by controlling the transfer of power across an energy transfer element. In operation, one or more switches are controlled to provide the desired power transfer. A wide variety of approaches have been described, including varying the duty cycle (i.e., the ratio of the on-time of the switch to the total switching period), varying the switching frequency, and/or varying the number of current conduction pulses per unit time.

A power converter can have a primary side and a secondary side that are galvanically isolated from each other. A power converter can also include one or more controllers to control the one or more switches. The one or more controllers may communicate across the galvanic isolation. One such communication system uses the windings of an inductive coupling to send information from a transmitter to a receiver.

<CIT> describes a communications method for controlling at least one power switching device of a power converter, a communications system for a power converter, and a power converter comprising the communications system.

<CIT> describes a fault detection circuit for use with a power converter includes an initiate fault check circuit coupled to generate an enable signal in response to a first sense signal coupled to be received from an output socket. A threshold detection circuit is coupled to generate a threshold detection output signal in response to a second sense signal coupled to be received from the power converter and a second reference signal. A logic circuit is coupled to generate a fault signal that is coupled to be received by the power converter in response to the threshold detection output signal and the enable signal.

<CIT> describes systems and methods for controlling a wireless power transfer system based upon Inductive Charging Technology using frequency based signaling communication protocol, operable to function in modes of Standby, Digital Ping, Identification, Power Transfer and End of Charge.

<CIT> describes a signal transmission system for communicating across galvanic isolation. The signal transmission system includes first circuitry referenced to a first potential, the first circuitry comprising signal transmission circuitry, second circuitry referenced to a second potential and galvanically isolated from the first circuitry, the second circuitry comprising signal reception circuitry, and a magnetic coupling between the first circuitry to the second circuitry across the galvanic isolation.

<CIT> describes a bi-directional, magnetic isolator that can pass an isolated housekeeping supply voltage from an input side to an output side and can also transfer an isolated error signal from the output side to the input side of the isolator. The magnetic isolator comprises a pair of pulse transformers each having a primary and a secondary winding. The housekeeping supply voltage is transferred through one of the pulse transformers by pulsing the supply voltage from the primary winding to a secondary winding, rectifying the pulsating voltage and storing the rectified voltage on an output capacitor. The error signal is transferred in an opposite direction through the second pulse transformer using the same technique, i.e., the error signal is chopped to create a pulsating signal that can be transferred from a primary winding to a secondary winding of the second pulse transformer where it is rectified and stored on an output capacitor as a voltage representative of the error signal. A fixed on-time clock is used to pulse both the supply voltage and the error signal.

Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

Corresponding reference characters indicate corresponding components throughout the several views of the drawings. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention.

Reference throughout this specification to "one embodiment", "an embodiment", "one example" or "an example" means that a particular feature, structure or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment", "in an embodiment", "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures or characteristics may be combined in any suitable combinations and/or subcombinations in one or more embodiments or examples. Particular features, structures or characteristics may be included in an integrated circuit, an electronic circuit, a combinational logic circuit, or other suitable components that provide the described functionality. In addition, it is appreciated that the figures provided herewith are for explanation purposes to persons ordinarily skilled in the art and that the drawings are not necessarily drawn to scale.

As described above, electrical devices may include an inductive coupling that provides a communications channel between a transmitter and a receiver that are galvanically isolated from one another. However, an inductive coupling communications channel may have certain limitations. For example, because the transmitter and the receiver are galvanically isolated, it may be costly to provide both the transmitter and the receiver with a clock signal. Communications across an inductive coupling communications channel are thus generally asynchronous and different transmitters can attempt to transmit a signal at the same time.

This specification describes inductive coupling communications channels that can address some of these limitations. For example, multiple transmitters and receivers can be coupled to an inductive coupling and access the communications channel that it provides. In effect, the inductive coupling can provide multiple channel access. In some cases, the transmitters can transmit asynchronously, i.e., without a clock signal or other timing mechanism that ensures that their respective transmissions do not collide. In some cases, the signals transmitted can have different priorities so that signals that are more important to the operation of a device are conveyed more reliably than signals that are less important.

The inductive coupling communications channels are implemented in power conversion systems in which a switch controller controls the switching of a power switch. In some such power conversion systems, the power switch may be an insulated-gate bipolar transistor (IGBT) controlled by an IGBT driver. In some cases, the switch controller may include a driver interface and a drive circuit that are coupled to communicate across galvanic isolation using the inductive coupling communications channel. The inductive coupling can be implemented as a signal transformer or other coupled inductors. The driver interface may be on the primary side of the transformer while the drive circuit may be on the secondary side. The power conversion system may also include a system controller, which controls one or more switch controllers.

The driver interface may be coupled to receive one or more input signals from a system controller and provide one or more output signals to the system controller. In one example, the driver interface receives a command signal from the system controller regarding switching the power switch between an ON state and OFF state. The command signal is then communicated to the drive circuit across the galvanic isolation via the inductive coupling communications channel to drive the switching of the power switch. In other words, the command signal is communicated from the primary to the secondary of the power converter.

The drive circuit is coupled to receive a fault signal representative of a fault condition of the power converter, such as an overcurrent or overvoltage condition of the power switch. The fault signal is communicated across the galvanic isolation via the inductive coupling communications channel from the drive circuit to the driver interface. The driver interface then outputs the fault signal to the system controller. In other words, the fault signal is communicated from the secondary to the primary of the power converter. An indication of the fault by the fault signal may trigger the system controller to immediately tum off the power switch or the driver may tum off the power switch independently of the fault signal transmission.

Operating conditions of the power switch or the power converter, such as temperature or voltage of the power switch, the input voltage of the converter, or the load current of the power switch, may also be communicated from secondary to the primary of the power converter. This can be referred to as data and the corresponding communications as data signals.

In embodiments in accordance with claim <NUM>, data signals regarding the operating conditions of the power switch/converter are communicated by the driver circuit to the driver interface across the galvanic isolation via the same inductive coupling communications channel that communicates fault signals and command signals. As such, the driver interface and the drive circuit are capable of bidirectional communication and may eliminate the need for additional hardware. Thus, a driver circuit can communicate both a fault signal and data signals across the galvanic isolation via a single inductive coupling communications channel.

The driver interface is coupled to the primary winding of the inductive coupling whereas the drive circuit is coupled to the secondary winding of the inductive coupling. The driver interface transmits a command signal to the drive circuit by applying a voltage to the primary winding, which induces a voltage and current in the secondary winding. Further, the drive circuit transmits both the fault signal and the data signal to the driver interface via the inductive coupling. The drive circuit sends a fault signal by providing current to flow in a first direction through the secondary winding of the inductive coupling and sends a data signal by providing current to flow in a second direction through secondary winding of the inductive coupling, wherein the first direction and second direction are opposite of each other. The driver interface receives and differentiates the fault signal and the data signal by the direction of the received induced current in the primary winding of the inductive coupling.

In one embodiment, the transmission of the command signal, fault signal, and data signal are not synchronized. As such, the duration and/or magnitude may be selected to manage collisions if the signals are transmitted at the same time. The duration and/or magnitude may be selected to operate in the high power/high noise environment like a power converter. In one example, the duration and/or magnitude of the fault signal is relatively long/large as compared to either the command signal or the data signal such that the fault signal will dominate. The magnitude of the command signal may be relatively large compared to the data signal but the duration may be relatively small as compared to either the fault signal or the data signal. Further, the data signal may have a relatively small magnitude but long duration as compared to either the fault signal or the command signal.

<FIG> illustrates an example power conversion <NUM> that includes a driver interface with bidirectional communication <NUM> and drive circuits with bidirectional communication <NUM>, <NUM>. Power converter <NUM> receives an input voltage <NUM> (VIN) and is designed to transfer electrical energy from the input to a load <NUM> through an energy transfer element L1 <NUM> by controlling the switching of power switches <NUM>, <NUM>. In various implementations, the power converter <NUM> can control voltage, current, or power levels of the energy output to the load <NUM>. In the example shown in <FIG>, energy transfer element L1 <NUM> and two power switches <NUM>, <NUM> are coupled together in a half-bridge configuration. However, other topologies can also be used.

In the example shown in <FIG>, power switches <NUM>, <NUM> are IGBTs. However, examples of the present invention can also be used in combination with other power switches. For example, metal-oxide-semiconductor field-effect transistors (MOSFETs), bipolar transistors, injection enhancement gate transistors (IEGTs) and gate turn-off thyristors (GTOs) can be used. In addition, power converter <NUM> can be used with power switches which are based on gallium nitride (GaN) semiconductors or silicon carbide (SiC) semiconductors.

System controller <NUM> is coupled to receive system inputs <NUM> and provide system outputs <NUM>. The system controller <NUM> determines whether the switch controllers (shown as the driver interface <NUM> and drive circuits <NUM>, <NUM>) should tum on or turn off the power switches <NUM>, <NUM> based on the system inputs <NUM>. Example system inputs <NUM> include pulse width modulated (PWM) signal for a general purpose motor drive, a turn-on and turn-off sequence of a multi-level power converter, or a system fault turn-off request.

In the illustrated power converter <NUM>, the system controller outputs one or more commands CMD <NUM> to the drive interface <NUM> of the switch controller. Command CMD <NUM> may be a rectangular pulse waveform that includes logic high and logic low sections of varying durations. For example, logic high values may indicate that power switch <NUM> should be in the ON state while logic low values may indicate that power switch <NUM> should be in the OFF state. Power switch <NUM> is switched alternately with power switch <NUM> so that both are not in the ON state at the same time. Indeed, power switches <NUM>, <NUM> are generally controlled to have a dead time where both are in the OFF-state between switching transitions. In any case, the durations of the logic high/logic low values can correspond to the desired driving of power switches <NUM>, <NUM>.

Power switches <NUM>, <NUM> are each controlled by the driver interface with bidirectional communication <NUM> and a drive circuit with bidirectional communication (<NUM>, <NUM> respectively). Although <FIG> illustrates a single driver interface <NUM>, it should be appreciated that each drive circuit <NUM>, <NUM> may have its own driver interface. The driver interface <NUM> and the system controller <NUM> are both referenced to a primary reference potential <NUM> while the drive circuit <NUM> is referenced to a secondary reference potential <NUM> and the drive circuit <NUM> is referenced to a secondary reference potential <NUM>. Secondary reference potentials <NUM>, <NUM> are different potentials. The drive circuits <NUM>, <NUM> bidirectionally communicate with the driver interface <NUM> and are also galvanically isolated from the driver interface <NUM> by isolated communication links <NUM>. The isolated communication links may be implemented as a signal transformer, coupled inductors, or other inductive coupling.

Driver interface <NUM> interprets the command CMD <NUM> sent by the system controller <NUM> and sends a command signal to instruct drive circuits <NUM>, <NUM> to drive power switches <NUM>, <NUM> into the ON and OFF states, respectively, via the isolated communication links <NUM>. The drive circuits <NUM>, <NUM> receive their respective command signals and generate the first drive signal UDR1 <NUM> and the second drive signal UDR2 <NUM> to drive power switches <NUM>, <NUM>.

In general, drive circuits <NUM>, <NUM> can have corresponding structures and perform corresponding operations. However, for the sake of brevity, a detailed description of the drive circuit <NUM> is omitted from the following discussion, which refers only to drive circuit <NUM>.

Drive circuit <NUM> receives a first sense signal USENSE1 <NUM> and a second sense signal USENSE2 <NUM>. The first and second sense signals USENSE1 <NUM>, USENSE2 <NUM> are representative of operational conditions of the power switch <NUM> and may be referred to as data. In the example shown, the first sense signal USENSE1 <NUM> is representative of the collector-to-emittter voltage of power switch <NUM> while the second sense signal USENSE2 <NUM> is representative of the temperature of the power converter as measured by the temperature sensor NTC <NUM>. Other example operating conditions include the gate-emitter voltage of the power switch, the current flowing through the power switch, or the load current of L1 <NUM>. Drive circuit <NUM> may detect a fault condition or receive fault signals (not shown) that are representative of an overvoltage or overcurrent fault in the respective power switches <NUM>, <NUM>. The fault signal and the data provided by the first and second sense signals USENSE1 <NUM>, USENSE2 <NUM> are communicated from the drive circuit <NUM> to the driver interface via the communication link <NUM>. The command signal is transmitted from the primary side of the power converter <NUM> to the secondary side of the power converter <NUM> while fault and data are transmitted from the secondary side of the power converter <NUM> to the primary side of the power converter <NUM>. As such, the communication across the isolating communication link <NUM> is bidirectional.

Driver interface <NUM> receives the fault signal and data signals from the drive circuit <NUM> and converts and outputs data signal D <NUM> and (if appropriate) fault signal F <NUM> to system controller <NUM>. The system controller <NUM> may use the received signals to determine whether to tum on or turn off power switches <NUM>, <NUM>. The determination whether to tum on or turn off power switches <NUM>, <NUM> may also be made, e.g., by drive circuit <NUM>.

<FIG> illustrates an example switch controller <NUM> with bidirectional communication between the driver interface <NUM> and the drive circuit <NUM>. The inductive coupling of communication link <NUM> is implemented as a signal transformer with a primary winding and secondary winding. The voltage across the primary winding is labeled as the primary voltage VP <NUM> while the voltage across the secondary winding is labeled as secondary voltage Vs <NUM>. The dots on the inductive coupling that forms communication link <NUM> represent the direction of current and polarity of voltage that one winding of a signal transformer induces in the other. It should be appreciated that similarly named and numbered elements are coupled and function as described above. Further, the system controller <NUM> and the power switch <NUM> are illustrated in <FIG> to provide context for the driver interface <NUM> and the drive circuit <NUM>.

System controller <NUM> is coupled to receive system inputs <NUM> and provide system outputs <NUM>. Further, the system controller <NUM> is coupled to output command signal CMD <NUM> to the driver interface <NUM> and receive fault signal FLT <NUM> and data signal DATA <NUM> from the driver interface. The system controller <NUM> may generate command CMD <NUM> in response to system inputs <NUM>, fault signal FLT <NUM>, and data signal DATA <NUM>.

The illustrated driver interface <NUM> includes a command transmitter <NUM>, a fault receiver <NUM>, and a data receiver <NUM>. Further shown are switches G1 <NUM>, G2 <NUM>, G3 <NUM>, and G4 <NUM>. The illustrated switches are n-type metal-oxide-semiconductor field effect transistors (MOSFETs) but it should be appreciated that other switches may be used. Switch G1 <NUM> is coupled to a supply voltage VDD and the dot-end of the primary winding of transformer <NUM>. Switch G2 <NUM> is coupled to primary reference <NUM> the end of the primary winding without the dot. Switch G3 <NUM> is coupled to the supply voltage VDD and the end of the primary winding without the dot. Switch G4 <NUM> is coupled to primary reference <NUM> and the dot-end of the primary winding of transformer <NUM>. As shown, the input/output terminal of the driver interface <NUM> which is coupled to transistors G1 <NUM>, G4 <NUM> is labeled with TRP while the input/output terminal of the driver interface <NUM> which is coupled to transistors G2 <NUM>, G3 <NUM> is labeled with TRN.

The command transmitter <NUM> is coupled to receive command CMD <NUM> from the system controller <NUM> and generate control signals for each of the switches G1 <NUM>, G2 <NUM>, G3 <NUM>, and G4 <NUM>. The voltage generated across the primary winding of transistor <NUM> by the control of switches G1 <NUM>, G2 <NUM>, G3 <NUM>, and G4 <NUM> can instruct drive circuit <NUM> to drive power switch <NUM>. In one example, command transmitter <NUM> responds to a logic high command signal CMD <NUM> by transmitting an ON command that instructs drive circuit <NUM> to drive power switch <NUM> into an ON state and to a logic low command signal CMD <NUM> by transmitting an OFF command that instructs drive circuit <NUM> to drive power switch <NUM> into an OFF state. For example, in response to receiving a rising edge in command CMD <NUM>, command transmitter <NUM> can control switches G1 <NUM>, G2 <NUM> into a conductive ON state and control switches G3 <NUM>, G4 <NUM> into a non-conductive OFF state for a fixed amount of time. As a result, the dot-end of primary winding is coupled to the supply voltage VDD and the other end is coupled to primary reference <NUM>. Voltage VDD is thus applied to the primary winding for a fixed amount of time. In another words, there is a positive pulse in primary voltage VP <NUM> of a magnitude that is substantially equal to voltage VDD. In response to receiving a falling edge in command CMD <NUM>, command transmitter <NUM> can control switches G3 <NUM>, G4 <NUM> into a conductive ON state and switches G1 <NUM>, G2 <NUM> into a non-conductive OFF state for a fixed amount of time. As a result, the dot-end of the primary winding is coupled to the primary reference <NUM> and the other end is coupled to supply voltage VDD. A negative reference voltage -VDD is thus applied to the primary winding for a fixed amount of time. In another words, there is a negative pulse in primary voltage VP<NUM> of a magnitude that is substantially equal to voltage VDD.

When the command transmitter <NUM> is not transmitting an ON command or an OFF command (i.e., in an idle state), the command transmitter <NUM> either a) turns on switches G2 <NUM>, G4 <NUM> and turns off switches G1 <NUM>, G3 <NUM> or b) turns off switches G2 <NUM>, G4 <NUM> and turns on switches G1 <NUM>, G3 <NUM>. This may be done to improve the noise immunity of the communications across the transformer <NUM>.

As will be further discussed, a fault receiver <NUM> is coupled to the dot-end of the primary winding of transformer <NUM> to sense an induced current and a data receiver <NUM> is coupled to the end of the primary winding without the dot to sense an induced current. These induced currents represent fault and data signals, respectively.

Drive circuit <NUM> includes the drive signal generator <NUM>, a fault transmitter <NUM>, and a data transmitter <NUM>. Drive signal generator <NUM> is coupled to the secondary winding and senses the secondary voltage Vs <NUM> across the secondary winding of transformer <NUM>. A changing voltage across the primary winding induces a voltage across the secondary winding. Drive signal generator <NUM> senses the induced secondary voltage Vs <NUM> to determine if the command transmitter <NUM> sends an ON command or an OFF command. Drive signal generator <NUM> also generates a responsive drive signal UDR <NUM> to drive the power switch <NUM> accordingly.

Fault transmitter <NUM> is coupled to receive a fault control signal UFAULT <NUM>. The fault control signal UFAULT <NUM> may indicate an overcurrent (e.g., an overload or short-circuit) or overvoltage fault in the power switch <NUM>. In one example, the fault control signal UFAULT <NUM> is a rectangular pulse waveform that includes logic high and logic low sections of varying lengths. In response to a fault, the fault control signal UFAULT <NUM> may transition to a logic high value. In response to the fault control signal UFAULT <NUM>, fault transmitter <NUM> generates a fault signal <NUM> to communicate the presence of a fault to the driver interface <NUM>. The fault transmitter <NUM> is referenced to a secondary reference <NUM>. Fault transmitter <NUM> may be implemented as a switchable current source that provides a fault current IFAULT <NUM> in response to the fault control signal UFAULT <NUM>. In the illustrated implementation, fault current IFAULT <NUM> flows into the dot-end of the secondary winding and induces a primary side fault current IFAULT_P <NUM> which flows out of the dot-end of the primary winding. The magnitude of the primary side fault current IFAULT_P <NUM> is related to the secondary side fault current IFAULT <NUM> by the turns ratio of the signal transformer <NUM>. Fault receiver <NUM> senses the primary side fault current IFAULT_P <NUM>, identifies that the primary side fault current IFAULT_P <NUM> is indicative of a fault on the secondary side, and outputs a signal FLT <NUM> to the system controller <NUM>.

In the illustrated implementation, data transmitter <NUM> is coupled to receive a first sense signal USENSE1 <NUM> and a second sense signal USENSE2 <NUM>. Both sense signals are representative of operating conditions of the power switch <NUM>. Data transmitter <NUM> encodes the data provided by the first sense signal USENSE1 <NUM> and the second sense signal USENSE2 <NUM> and generates a data signal IDATA <NUM> that embodies that data. Data signal IDATA <NUM> induces a corresponding primary side data current IDATA_P <NUM> and thereby conveys information to the driver interface <NUM> via an inductive coupling <NUM>. In some implementations, the information is encoded in a binary word. For example, logic high pulses in the data signal IDATA <NUM> can indicate binary "<NUM>" and logic low pulses or no pulse can indicate binary "<NUM>. " In some implementations, the data signal IDATA <NUM> comports with a universal asynchronous receiver transmitter (UART) protocol. In some implementations, an error-correcting code such as a Hamming code or cyclic redundancy check (CRC) code can be used.

The data transmitter <NUM> is referenced to secondary reference potential <NUM> and may be implemented as a current source that provides data current signal IDATA <NUM>. Data current signal IDATA <NUM> flows into a different end of the secondary winding from fault current IFAULT <NUM>, namely, the end of the secondary winding without the dot in the illustrated implementation. The secondary side data current IDATA <NUM> induces a primary side data current IDATA_P <NUM> which flows from the opposite end of the dot in the primary winding. The magnitude of the primary side data current IDATA_P <NUM> is related to the magnitude of the secondary side data current IDATA <NUM> by the turns ratio of the signal transformer <NUM>. Data receiver <NUM> senses the primary side data current IDATA_P <NUM> and decodes the received signal. The decoded information is conveyed to the system controller as DATA <NUM>. As will be discussed further below, the magnitude and the duration of the command signals sent by the command transmitter <NUM> (i.e., primary voltage VP <NUM>), the fault signals sent by the fault transmitter <NUM> (i.e., fault current IFAULT <NUM>), and the data signals sent by the data transmitter <NUM> (i.e., data current IDATA <NUM>) may be chosen so that these signals can be differentiated even in the event of collisions between them. Driver interface <NUM> and drive circuit <NUM> thus need not be synchronized or limited to transmitting information in accordance with a time sharing scheme. Rather, the communications channel formed by inductive coupling <NUM> can provide simultaneous access to multiple transmitters that transmit data asynchronously.

<FIG> is a table <NUM> of example current and voltage values for the command signals, fault signal, and data signals input into signal transformer <NUM> for an example implementation. It should be appreciated that the polarities of the currents are consistent with their illustration in <FIG>. The polarities of the primary voltage VP <NUM> and secondary voltage Vs <NUM> are also consistent with their illustration <FIG>.

The first row of the table <NUM> sets forth the primary voltage VP <NUM> for a transmitted ON command and a transmitted OFF command in the example implementation. For an ON command, the primary voltage VP <NUM> is substantially +VDD for a period T1. For an OFF command, the primary voltage VP <NUM> is substantially -VDD for a period T1. In the example implementation, VDD is substantially <NUM> volts (V) and period T1 is substantially <NUM> nanoseconds (ns). Although the example ON and OFF commands have an equal duration but opposite polarity, it should be appreciated that a variety of different polarities and durations may be used in other implementations.

The second row of table <NUM> sets forth the secondary winding current for a transmitted fault current IFAULT <NUM> in the example implementation. In response to a fault, the magnitude of the fault current IFAULT <NUM> is substantially equal to -I<NUM> for a period T2. In the absence of a fault, the fault current IFAULT <NUM> can be substantially equal to zero. The duration of period T2 is greater than the duration of period T1 for the command signals. In the example implementation, I<NUM> is substantially equal to <NUM> milliamps (mA) and the duration of period T1 is substantially equal to <NUM> microseconds (us). However, in other implementations, different polarities and durations may be used. For example, the windings of the transformer may be wrapped in the opposite direction around the core. Also, in other implementations, a no fault condition may be another magnitude and/or may have a predetermined duration.

The third row of table <NUM> sets forth the secondary winding current for a transmitted data current IDATA <NUM> in the example implementation. In the example implementation, the data is encoded in a binary word. The data current IDATA <NUM> is substantially equal to +I<NUM> for period T3 to transmit a binary "<NUM>. " Data current IDATA <NUM> is substantially zero to transmit a binary "<NUM>. " Further, the duration of period T3 is greater than the duration of period T1. In the example implementation , +I<NUM> is substantially 30mA and period T3 has a duration of <NUM>. However, in other implementations, different polarities and durations may be used. Also, a "<NUM>" transmission may be another magnitude and/or may have a predetermined duration.

<FIG> illustrates a data transmitter <NUM>, which is one example of data transmitter <NUM> shown in <FIG>. It should be appreciated that similarly named and numbered elements are coupled and function as described above. Further, an inductive coupling <NUM>, a drive signal generator <NUM>, and a power switch <NUM> are illustrated to provide context for the data transmitter <NUM>.

The data transmitter <NUM> includes a data control/encoder <NUM>, a switch <NUM> (illustrated as an n-type MOSFET), resistances <NUM>, <NUM>, and a diode <NUM>. Resistance <NUM> is coupled to the data control/encoder <NUM> and the control terminal of switch <NUM>. Diode <NUM> is coupled to resistance <NUM> and the end of the secondary winding without the dot. Resistance <NUM> is coupled to the dot-end of the secondary winding and the switch <NUM>. Switch <NUM> is coupled between resistor <NUM> and secondary reference <NUM>.

Data transmitter <NUM> may also include an optional demagnetization circuit <NUM> to demagnetize the transformer <NUM>. Demagnetization may prevent transformer <NUM> from going into saturation. Demagnetization circuit <NUM> includes a switch <NUM> (illustrated as an n-type MOSFET), resistances <NUM>, <NUM>, and a diode <NUM>. Resistance <NUM> is coupled to the data control/encoder <NUM> and the control terminal of switch <NUM>. Diode <NUM> is coupled to resistance <NUM> and the dot-end of the secondary winding. Resistance <NUM> is coupled to the end of the secondary winding without the dot and the switch <NUM>. Switch <NUM> is coupled between resistor <NUM> and secondary reference <NUM>.

The data control/encoder <NUM> receives the first and second sense signals USENSE1 <NUM>, USENSE2 <NUM> and encodes at least some of the data provided by these signals. The data control/encoder <NUM> may optionally include an analog-to-digital converter to convert the data into a digital value, a SPI (Serial Peripheral Interface), an I2C interface, or other digital interface to receive data from a digital sensor. In some implementations, data control/encoder <NUM> may apply a universal asynchronous receiver transmitter (UART) protocol. In some implementations, data control/encoder <NUM> may use an error-correcting code such as a Hamming code or cyclic redundancy check (CRC) code.

Data control/encoder <NUM> controls switch <NUM> into and out of conduction to generate data current IDATA <NUM>. In one embodiment, data control signal UDATA <NUM> is logic high when transmitting a binary "<NUM>" and logic low when transmitting a binary "<NUM>. " Or in other words, the data control signal UDATA <NUM> switches the switch <NUM> into conduction to transmit a binary "<NUM>" and switches the switch <NUM> out of conduction to transmit a binary "<NUM>. " The inverse polarity can also be used. When the data control signal UDATA <NUM> turns on the switch <NUM>, current flows through resistor <NUM>, diode <NUM> and into the end of the secondary winding without the dot. The current flows out of the dot-end of the secondary winding and through resistor <NUM> and switch <NUM> to secondary reference <NUM>. In one example, the magnitude of data current IDATA <NUM> is substantially equal to I<NUM> and switch <NUM> is turned on for period T3. The data current IDATA <NUM> induces a primary side data current IDATA_P <NUM> which flows out of the end of the primary winding without the dot.

The transmitted data current IDATA <NUM> may magnetize and eventually saturate the transformer <NUM>. Demagnetization circuit <NUM> may demagnetize the transformer <NUM> intermittently or every time the data transmitter <NUM> transmits a binary "<NUM>. " The demagnetization circuit <NUM> demagnetizes the transformer <NUM> by sending a demagnetization current IDEMAG <NUM> of equal value to the data current IDATA <NUM> but in the opposite direction through the secondary winding. In the example shown, the demagnetization current IDEMAG <NUM> flows into the dot end of the secondary winding. The equal and opposite demagnetization current IDEMAG <NUM> may be transmitted before or after a binary "<NUM>" data current IDATA <NUM> or when necessary. When the switch <NUM> is turned on, demagnetization current IDEMAG <NUM> flows through resistor <NUM>, diode <NUM> and into the dot-end of the secondary winding. The demagnetization current IDEMAG <NUM> flows out of the secondary winding and through resistor <NUM> and switch <NUM> to secondary return <NUM>. In some implementations, the values of resistances <NUM> and <NUM> may be substantially equal and the value of resistances <NUM> and <NUM> may be substantially equal. In other implementations, they may have different values.

<FIG> illustrates example first and second sense signals USENSE1 <NUM>, USENSE2 <NUM>. In one example, the first sense signal USENSE1 <NUM> is representative of the input voltage VIN <NUM> and may increase as the input voltage VIN <NUM> increases. The second sense signal USENSE2 <NUM> is representative of temperature and may decrease as the temperature increases.

<FIG> illustrates a fault transmitter <NUM>, which is one example of the fault transmitter <NUM> shown in <FIG>. It should be appreciated that similarly named and numbered elements couple and function as described above. Further, an inductive coupling <NUM>, a drive signal generator <NUM>, and a power switch <NUM> are illustrated to provide context for fault transmitter <NUM>.

The fault transmitter <NUM> includes switches <NUM>, <NUM> (illustrated as n-type MOSFETs) and a diode <NUM>. Switch <NUM> is coupled between a supply voltage VISO and diode <NUM>. Further, switch <NUM> is controlled by fault control signal UFAULT <NUM>. Diode <NUM> is coupled to the dot-end of the secondary winding of inductive coupling <NUM>. The switch <NUM> is coupled to the other end of the secondary winding (without the dot) and is referenced to secondary reference <NUM>. Switch <NUM> is controlled by shifted fault control signal UFAULT' <NUM>.

The fault control signal UFAULT <NUM> and shifted fault control signal UFAULT' <NUM> are synchronized and, in some implementations, can be output from a single source. In response to sensing a fault, both fault control signal UFAULT <NUM> and shifted fault control signal UFAULT' <NUM> can be transitioned to a logic high state that controls switches <NUM>, <NUM> into a conductive state. Fault current IFAULT <NUM> flows through switch <NUM>, diode <NUM>, and into the dot-end of the secondary winding of transformer <NUM>. Fault current IFAULT <NUM> also flows out of the opposite end of the secondary winding and to secondary reference <NUM> through switch <NUM>. The magnitude of the fault current IFAULT <NUM> is substantially equal to current I<NUM> and the switches <NUM>, <NUM> are turned on for period T2.

<FIG> illustrates a fault receiver <NUM> and data receiver <NUM>, which are examples of the fault and data receiver <NUM>, <NUM> shown in <FIG>. It should be appreciated that similarly named and numbered elements are coupled and function as described above. Further, an inductive coupling <NUM> is illustrated to provide context for the fault receiver <NUM> and data receiver <NUM>.

The fault receiver <NUM> is shown as including a comparator <NUM>, an integrator <NUM>, and a comparator <NUM>. The fault receiver <NUM> is coupled to the dot-end of the primary winding of transformer <NUM>. As mentioned above, a transmitted fault current IFAULT <NUM> on the secondary induces a primary side fault current IFAULT_P <NUM>. The primary side fault current IFAULT_P <NUM> is sensed by the fault receiver <NUM>. In one example, the primary side fault current IFAULT_P <NUM> may be sensed by a current sensing resistance or MOSFET. For example, the fault current IFAULT_P <NUM> may be sensed by sensing the drain-source voltage of transistor G4 shown in <FIG>.

The sensed primary side fault current IFAULT_P <NUM> and a first threshold TH1 <NUM> is received by comparator <NUM>. As shown, the primary side fault current IFAULT_P <NUM> is received at the non-inverting input while the first threshold TH1 <NUM> is received at the inverting input of comparator <NUM>. The output of comparator <NUM> is received by integrator <NUM>. In the illustrated example, integrator <NUM> integrates with an upward slope up to a maximum value when the sensed primary side fault current IFAULT_P <NUM> is greater than the first threshold TH1 <NUM>. The integrator <NUM> integrates with a downward slope to a minimum value when the sensed primary side fault current IFAULT_P <NUM> is less than the first threshold TH1 <NUM>. As will be further discussed, the first threshold TH1 <NUM> may be within the range of <NUM>-145mA. For an example where the sensed primary side fault current IFAULT_P <NUM> is a voltage signal, the first threshold TH1 <NUM> may be a range of voltage values which correspond to a current value of <NUM>-145mA.

In operation, when the sensed primary side fault current IFAULT_P <NUM> is greater than the first threshold TH1 <NUM>, comparator <NUM> outputs a high signal that is integrated with an upward slope up to a maximum value by integrator <NUM>. When the sensed primary side fault current IFAULT_P <NUM> is less than the first threshold TH1 <NUM>, comparator <NUM> outputs a low signal and integrator <NUM> is discharged with a downward slope down to a minimum value. The integration result is output from integrator <NUM>.

Comparator <NUM> is coupled to receive the output of integrator <NUM> and a second threshold TH2 <NUM>. As shown, the output of integrator <NUM> is received at the inverting input of comparator <NUM> and the second threshold TH2 <NUM> is received at the non-inverting input. In response to the output of integrator <NUM> rising above second threshold TH2 <NUM>, comparator <NUM> outputs a logic high fault signal FLT <NUM>. In response to the output of integrator <NUM> being below second threshold TH2 <NUM>, comparator <NUM> outputs logic low fault signal FLT <NUM>. The second threshold TH2 <NUM> may be representative of a time threshold for the amount of time which the sensed primary side fault current IFAULT_P <NUM> is greater than the first threshold TH1 <NUM>. For example, the second threshold TH2 <NUM> may correspond to an amount of time between <NUM>-1620ns. Signal FLT <NUM> is conveyed to the system controller (not shown). Thus, when the output of integrator <NUM> is greater than the second threshold TH2 <NUM>, fault receiver <NUM> indicates that a fault was transmitted from the driver circuit on the secondary.

Data receiver <NUM> includes a comparator <NUM>, an integrator <NUM>, a comparator <NUM>, and a decoder <NUM>. Data receiver <NUM> is coupled to the end opposite of the dot-end of the primary winding of transformer <NUM>. As mentioned above, a transmitted data current signal IDATA <NUM> from the driver circuit induces a primary side data current IDATA_P <NUM>. The primary side data current IDATA_P <NUM> is sensed by data receiver <NUM>. For example, the primary side data current IDATA_P <NUM> may be sensed by a current sensing resistor or MOSFET.

The sensed primary side data current IDATA_P <NUM> and a third threshold TH3 <NUM> is received by comparator <NUM>. As shown, the primary side data current IDATA_P <NUM> is received at the non-inverting input while the third threshold TH3 <NUM> is received at the inverting input of comparator <NUM>. As will be further discussed, the third threshold TH3 <NUM> may be within the range of <NUM>-20mA. For an example where the sensed primary side data current IDATA_P <NUM> is a voltage signal, the third threshold TH3 <NUM> may be a range of voltage values which correspond to a current value of <NUM>-20mA. In operation, when the sensed primary side data current IDATA_P <NUM> is greater than the third threshold TH3 <NUM>, comparator <NUM> outputs a high signal that is integrated with an upward slope up to a maximum value by integrator <NUM>. When the sensed primary side data current IDATA_P <NUM> is less than the third threshold TH3 <NUM>, comparator <NUM> outputs a low signal and integrator <NUM> is discharged with a downward slope down to a minimum value. The integration result is output from integrator <NUM>.

Comparator <NUM> is coupled to receive the output of integrator <NUM> and a fourth threshold TH4 <NUM>. As shown, the output of integrator <NUM> is received at the inverting input of comparator <NUM> and the fourth threshold TH4 <NUM> is received at the non-inverting input. The output of comparator <NUM> is logic high in response to output of integrator <NUM> rising above fourth threshold TH4 <NUM>. The output of comparator <NUM> is logic low in response to the output of integrator <NUM> being less than the fourth threshold TH4 <NUM>. The fourth threshold TH4 <NUM> may be representative of a time threshold for the amount of time which the sensed primary data current IDATA_P <NUM> is greater than the third threshold TH3 <NUM>. For example, the fourth threshold TH4 <NUM> may correspond to an amount of time greater than <NUM>-<NUM>. Successive logic high and logic low states on the output of integrator <NUM> can form a series of binary bits that represent of operating conditions on the secondary.

Decoder <NUM> receives the output of comparator <NUM> and decodes the series of bits sent by the data transmitter <NUM>. Based on the information encoded in bits, decoder <NUM> outputs data DATA <NUM> to the system controller. The outputted data DATA <NUM> can be in the form of an analog signal, PWM signal, a bit stream, etc..

<FIG> is a table <NUM> setting forth one implementation of the magnitudes and durations-- at transmission-- of command signals, fault signals, and data signals that can embody their relative priorities of those signals in the event of collisions on the inductive coupling. As discussed above, the driver interface and driver circuit need not be synchronized and collisions between the signals may occur. As such, the nature of the signals may be selected to set a relative priority that determines which signals are received when a collision occurs. In effect, a lossy but multiple access communications channel can be implemented on the inductive coupling.

In the example shown in <FIG>, fault signals are prioritized over command and data signals. At least at the time of their transmission, command signals are prioritized over data signals. However, in general, the duration of data signal transmission is much longer and data will generally not be lost even with an intervening command signal. To implement these priorities, the fault signal at transmission can have relatively large (current) magnitude for a relatively long duration of time relative to the other signals. Details of an example fault signal are shown in the top row of table <NUM>. Further, command signals can be implemented as voltage signals, in contrast with the fault and data current signals. Details of an example command signal at transmission are shown in the second row of table <NUM>. Please note that command signals can be significantly shorter in duration than both fault and data signals. The individual bits that constitute data signals (and the associated demagnetization currents) are small in magnitude but have a relatively longer duration compared to fault signals and command signals. Details of an example data bit at transmission are shown in the third row of table <NUM>, and details of an example demagnetization current are shown in the fourth row of table <NUM>. It should be appreciated that the example fault and data, signals are current signals but the command signals are voltage signals. Nevertheless, these signals all induce a voltage or a current on the other side of the galvanic isolation provided by the inductive coupling.

In the example shown, fault current signals have a magnitude of I<NUM> substantially equal to 170mA and period T2 has a duration of <NUM> at transmission. The first threshold TH1 used to detect the fault current signal is within the range of <NUM>-145mA. Command voltage signals have a magnitude of supply voltage VDD substantially equal to 15V (which translates to a command current of magnitude ICMD substantially equal to 70mA) for period T1, which is substantially equal to 200ns in duration. ON command signals have a positive polarity whereas OFF command signals have a negative polarity of equal magnitude. As discussed above, the ON and OFF command signals need be equal in duration and opposite in polarity. Data current bits have a magnitude of I<NUM> substantially equal to 30mA and a period T3 with a duration of <NUM> at transmission. The third threshold TH3 used to detect a data current bit is within the range of <NUM>-20mA. Demagnetization currents have magnitude of I<NUM> substantially equal to 30mA and a period T3 with a duration that is substantially equal to <NUM>. The polarity of the demagnetization currents is opposite the polarity of the data current bits.

<FIG> is a timing diagram <NUM> which schematically illustrates an example collision between signals that are transmitted on the inductive coupling simultaneously. As described above, at transmission on the secondary winding, a fault signal can have a magnitude of I<NUM> substantially equal to 170mA and period T2 substantially equal to <NUM> in duration. At transmission on the secondary winding, data current bits can have a magnitude of I<NUM> substantially equal to 30mA and a period T3 with a duration that is substantially equal to <NUM>, but a polarity that is opposite to the polarity of the fault signal. In one example, the magnitude of the fault current signals received at the primary winding may be referred to with magnitude I2_P. The range for the magnitude I2_P is related to threshold TH1 (shown in <FIG>). For example, the magnitude I2_P for the primary side fault current should be greater than the first threshold TH1. In one example, the first threshold TH1 <NUM> is within the range of <NUM>-145mA. For data bits, the magnitude of the signals received on the primary winding may be referred to as magnitude I3_P. The range for the magnitude I3_P is related to threshold TH3 (shown in <FIG>). For example, the magnitude I3_P for the primary side data current should be greater than the third threshold TH3 <NUM>. In one example, the third threshold TH3 <NUM> is within the range of <NUM>-20mA. Although the fault signals and data bits may have predetermined durations at transmission on the secondary side, the durations received on the primary side may vary due to noise and other conditions. For example, the duration of received fault current signals may be greater than <NUM>-<NUM> ns to exceed time threshold TH2 (shown in <FIG>) and the duration of received data bits may be greater than <NUM>-<NUM> to exceed time threshold TH4 (shown in <FIG>).

Timing diagram <NUM> illustrates a primary winding current <NUM> that includes a three-way collision between an ON command <NUM>, a binary "<NUM>" data bit <NUM>, and a fault signal <NUM>. As shown, the ON command <NUM> collides with the binary "<NUM>" data bit <NUM> first. A fault signal <NUM> subsequently collides with the same binary "<NUM>" data bit <NUM>. The polarity of the primary winding current <NUM> shown in <FIG> (and <FIG>) for current flowing into terminal TRN (i.e. to transistors G2 or G3 shown in <FIG>) is positive while current flowing out of terminal TRN (i.e. from transistors G2 or G3 shown in <FIG>) is negative.

For the illustrated example, a demagnetization current <NUM> is induced on the primary side before the binary "<NUM>" data bit <NUM>. For the sake of simplicity, a magnetizing current is not shown <FIG> and <FIG>. During the demagnetization current <NUM>, the primary winding current is substantially -I3_P <NUM> for period T3 <NUM>. After the demagnetization current <NUM> has finished, the binary "<NUM>" data bit <NUM> begins and the primary winding current <NUM> increases to substantially I3_P <NUM> for period T3 <NUM>. The primary winding current is substantially I3_P <NUM> for period T3 <NUM> except during collisions with the ON command <NUM> and the fault signal <NUM>. As shown, an ON command <NUM> is transmitted at the same time as the binary "<NUM>" data bit <NUM> is received. A spike in the primary winding current <NUM> is associated with the ON command <NUM> and the primary winding current <NUM> increases to a magnitude ICMD <NUM> for period T1 <NUM>. After the period T1 <NUM>, the primary winding current <NUM> decreases to substantially I3_P <NUM>. Since the ON command transition <NUM> is a voltage signal, it swamps the voltage associated with transmission of a binary "<NUM>" data bit <NUM> and the ON command <NUM> can be received on the secondary side notwithstanding the collision. In effect, during the transmission of an ON command, the ON command <NUM> is prioritized over the received binary "<NUM>" data bit <NUM>. However, in general, the duration of data signal transmission is much longer than the ON command and data will generally not be lost even with an intervening ON command.

The fault signal <NUM> is received at the primary winding during the time that the binary "<NUM>" data bit <NUM> is received. As shown, the primary winding current <NUM> decreases to substantially -I2_P <NUM> for period T2 <NUM> in the midst of data bit <NUM>. At the end of period T2 <NUM>, the primary winding current <NUM> increases to a magnitude substantially equal to I3_P <NUM> and remains at magnitude I3_P <NUM> for the remainder of period T3 <NUM>. Since the polarity of the received fault signal <NUM> is opposite to the polarity of the received data bit <NUM>, the fault signal can be discerned notwithstanding the collision. In effect, the polarity of fault signal <NUM> embodies a prioritization of the fault signal <NUM> over the binary "<NUM>" data bit <NUM>.

<FIG> is another timing diagram that schematically illustrates a collision between an ON command <NUM>, a fault signal <NUM>, and a binary "<NUM>" data bit <NUM> on the primary side of a power converter. Similar to <FIG>, a demagnetization current <NUM> is induced on the primary side before the binary "<NUM>" data bit <NUM> is transmitted. During demagnetization <NUM>, the primary winding current is substantially -I3_P for period T3 <NUM>. After demagnetization <NUM> has finished, the binary "<NUM>" data bit <NUM> begins and the primary winding current <NUM> increases to substantially I3_P for period T3 <NUM>. The primary winding current is substantially I3_P <NUM> for period T3 <NUM> except during collisions with an ON command <NUM> and a fault signal <NUM>.

The fault signal <NUM> is received at the primary winding in the midst of a binary "<NUM>" data bit <NUM>. As shown, the primary winding current <NUM> decreases to substantially -I2_P <NUM> for period T2 <NUM>. During the received fault signal <NUM>, an ON command <NUM> is transmitted during the period T2 <NUM>. A spike in the primary winding current <NUM> is associated with the ON command <NUM> and the primary winding current <NUM> increases for period T1 <NUM>. The peak of ON command <NUM> is substantially -I2_P plus ICMD. After the period T1 <NUM>, the primary winding current <NUM> decreases to substantially -I2_P <NUM> and the fault signal <NUM> again predominates. At the end of period T2 <NUM>, the primary winding current <NUM> increases to a magnitude substantially equal to I3_P <NUM> and remains at magnitude I3_P <NUM> for the remainder of period T3 <NUM>. The respective magnitude and duration of the fault signal <NUM> and ON command signal <NUM> embodies a prioritization of fault signal <NUM> over the ON command signal <NUM>. In particular, fault signal <NUM> can still be discerned by a fault receiver that integrates as described above.

The above description of illustrated examples of the present invention, including what is described in the Abstract, are not intended to be exhaustive or to be limitation to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, the scope of protection of the present invention is only defined by the attached claims.

Claim 1:
A method comprising communicating fault signals (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), command signals, and data signals (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) regarding operating conditions of a power switch (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) or power converter from a driver circuit (<NUM>, <NUM>, <NUM>) to a driver interface (<NUM>, <NUM>) across a galvanic isolation (<NUM>) via an inductive coupling communications channel, wherein the driver interface is coupled to a primary winding of an inductive coupling (<NUM>, <NUM>, <NUM>, <NUM>) and the drive circuit is coupled to a secondary winding of the inductive coupling, the method comprising:
transmitting, by the driver interface, a command signal to the drive circuit by applying a voltage to the primary winding, which induces a voltage and current in the secondary winding;
and characterized by further comprising:
transmitting, by the drive circuit, both a fault signal and a data signal to the driver interface via the inductive coupling, wherein the drive circuit sends the fault signal by providing current to flow in a first direction through the secondary winding of the inductive coupling and sends the data signal by providing current to flow in a second direction through secondary winding of the inductive coupling, wherein the first direction and second direction are opposite of each other; and
receiving, by the driver interface the fault signal and the data signal; and
differentiating, by the driver interface, the fault signal and the data signal by the direction of the received induced current in the primary winding of the inductive coupling.