Patent Description:
<CIT> describes a solid state switch including a terminal T <NUM>, a terminal L <NUM>, at least one FET-type device coupled to terminal T <NUM> and terminal L <NUM>, and at least one thyristor-type device coupled to the terminal T <NUM> and terminal L 1in parallel to the at least one FET-type device. Current flow passing through the solid state switch may be shared insofar as the at least one FET-type device transmitting all current at lower current regimes, e.g. below some predetermined threshold value, with the at least one thyristor-type device transmitting all current in higher current regimes, e.g., above the threshold value. The at least one FET-type device and the at least one thyristor-type device each may have one or more dedicated gate drivers for providing on- and/or off-signals to the gates of the at least one FET-type device and the at least one thyristor-type device.

In view of these and other shortcomings in the art, there is a significant need for the unique apparatuses, methods, systems and techniques disclosed herein.

Accordingly, there is provided an apparatus as defined by independent claim <NUM>, and a method as defined by independent claim <NUM>. Specific embodiments are defined by the dependent claims. For the purposes of clearly, concisely and exactly describing non-limiting exemplary embodiments of the disclosure, the manner and process of making and using the same, and to enable the practice, making and use of the same, reference will now be made to certain exemplary embodiments, including those illustrated in the figures, and specific language will be used to describe the same.

Exemplary embodiments of the disclosure include unique systems, methods, techniques and apparatuses for power switch control. Further embodiments, forms, objects, features, advantages, aspects and benefits of the disclosure shall become apparent from the following description and drawings.

With reference to <FIG>, there is a circuit diagram illustrating an exemplary power switch <NUM>, also known as a ThyFET switch. It shall be appreciated that power switch <NUM> may be implemented in a variety of applications, including solid state contactors, solid state circuit breakers, solid state disconnectors, and other types of devices structured to open in order to interrupt the flow of current, to name but a few examples. Power switch <NUM> may be incorporated into alternating current (AC) power systems, direct current (DC) power systems, power distribution systems, power transmission systems, facility power systems, vehicular power systems, and machine drives, to name but a few examples.

Power switch <NUM> includes a field-effect transistor (FET) based branch <NUM> and a thyristor-based branch <NUM> coupled in parallel between terminals <NUM> and <NUM>. Branch <NUM> and branch <NUM> are both structured to selectively allow current to flow between terminals <NUM> and <NUM>. In other embodiments, power switch <NUM> may be structured to conduct current in a single direction.

FET-based branch <NUM> includes a FET device <NUM> and a FET device <NUM> coupled in series. FET devices <NUM> and <NUM> may each include a junction gate field-effect transistor (JFET) or a metal-oxide-semiconductor field-effect transistors (MOSFETs) based on various semiconductor technologies such as silicon (Si), silicon-carbide (SiC), or gallium-nitride (GaN), to name but a few examples.

Each FET device is a power semiconductor device with a different conduction power loss profile relative to thyristor devices. The voltage-current characteristic of FET devices is mostly resistive and yields lower conduction losses at lower current magnitudes, in comparison to thyristor devices. Thyristor devices have voltage-current characteristics related to a fixed voltage of the p-n junction voltage of a FET device. The fixed voltage characteristic generates relatively high losses compared to FET devices at lower current magnitudes, but generates relatively lower losses as compared to FET devices at higher current magnitudes.

As the magnitude of current flowing through branch <NUM> increases, the voltage across branch <NUM> increases. Furthermore, as the magnitude of the current flowing through branch <NUM> increases, power losses increase at a rate greater than a linear increase, also known as an exponential increase.

In certain embodiments, branch <NUM> includes additional components such as additional FET devices or filters, to name but a few examples. In other embodiments, branch <NUM> includes a single FET device.

Thyristor-based branch <NUM> includes a thyristor device <NUM> and a thyristor device <NUM> coupled in an antiparallel configuration. Thyristor devices <NUM> and <NUM> may each include a silicon controlled rectifier (SCR), a silicon controlled switch (SCS), a gate turn-off thyristor (GTO), or an integrated gate-commutated thyristor (IGCT), to name but a few examples.

Thyristor device <NUM> is structured such that when turned on, current may flow from terminal <NUM> to terminal <NUM> by way of thyristor device <NUM>. Thyristor device <NUM> is structured such that when turned on, current may flow from terminal <NUM> to terminal <NUM> by way of thyristor device <NUM>. Depending on the direction of current from terminal <NUM> to terminal <NUM> or vice-versa, there is a positive voltage VAK1 from the anode to cathode of device <NUM> or a positive voltage VAK2 from the anode to cathode of device <NUM>. When either voltage VAK1 or VAK2 is positive, the voltage is referred to as a forward voltage.

Thyristor device <NUM> and thyristor device <NUM> are structured such that the voltage across each thyristor device remains constant while conducting current over a range of magnitudes. As a result, power loss through thyristor-based branch <NUM> may correspond proportionally to the magnitude of the current flowing through branch <NUM>.

The FET devices and the thyristor devices are each selected and constructed or sized to minimize power losses of power switch <NUM> at both lower current magnitudes and higher current magnitudes, thus providing an improved loss profile. Each FET device includes a first power loss characteristic based on a rated current. Each thyristor device includes a second power loss characteristic based on a surge current, for example and without limitation, an inrush current and a start current associated with an electric motor.

Power switch <NUM> includes a controller <NUM> structured to measure electrical characteristics of power switch <NUM>. In the illustrated embodiment, controller <NUM> includes a voltage sensor <NUM> coupled to terminal <NUM> and a voltage sensor <NUM> coupled to terminal <NUM>. Each voltage sensor is structured to measure a voltage of power switch <NUM>. For example, each voltage sensor may measure a line-to-ground voltage. Controller <NUM> may then use the measured voltages to determine a voltage across power switch <NUM>. In another embodiment, controller <NUM> may include a single voltage sensor to measure a voltage across power switch <NUM>.

Controller <NUM> controls the devices of branches <NUM> and <NUM> such that only branch <NUM> is turned on when controller <NUM> determines the magnitude of current conducted by power switch <NUM> is less than a current threshold, and both branches <NUM> and <NUM> are turned on when controller <NUM> determines the magnitude of the current conducted by power switch <NUM> is greater than the current threshold. Controller <NUM> uses the voltage measurements from voltage sensors <NUM> and <NUM> to determine a voltage threshold corresponding to the current threshold. Using the voltage threshold, controller <NUM> determines whether the magnitude of the conducted current is less than or greater than the current threshold. As explained in more detail below, controller <NUM> is structured to update the voltage threshold based on operating conditions of power switch <NUM>. It shall be appreciated that the features of power switch <NUM> may be present in other exemplary power switches described herein, such as power switches <NUM> and <NUM>.

With reference to <FIG>, there is a graph <NUM> illustrating power losses of an exemplary power switch, such as power switch <NUM>, including a single FET device coupled in parallel with a single thyristor device. Graph <NUM> includes a line <NUM> representing power losses generated by a FET device over a range of current magnitudes, and a line <NUM> representing power losses generated by a thyristor device over a range of current magnitudes.

As illustrated by graph <NUM>, there is a current magnitude, also known as current threshold ITH, where the power loss generated by the current magnitude flowing through the FET device is equal to the power loss generated by the current magnitude flowing through the thyristor device. For all current magnitudes less than current threshold ITH, the FET device generates less power loss compared to the thyristor device. For all current magnitudes greater than current threshold ITH, the thyristor device generates less power loss compared to the FET device.

By controlling the power switch to turn on the thyristor device for all current magnitudes greater than current threshold ITH, the exemplary power switch reduces power losses. By allowing current to flow through both the FET device configuration and the thyristor device configuration after the current magnitude exceeds current threshold ITH, the combined loss profile of the power switch is less than the separate power loss profiles of the FET device or the thyristor device.

As illustrated by graph <NUM>, the favorable combined loss profile is dependent on current sharing between the FET device and the thyristor device. Therefore, the more accurately the voltage threshold used by the controller corresponds to the current threshold, the smaller the power losses of the power switch. If the voltage threshold corresponds to a current magnitude greater than current threshold ITH, the high voltage across the thyristor device will increase power losses and more current will flow through the FET device, also increasing power losses. A voltage threshold less than the forward voltage required by the thyristor device to turn on would result in the thyristor device not being turned on.

Operating conditions of an exemplary power switch will cause the current threshold ITH to change. For example, the resistance of the FET device increases as the operating temperature of the FET device increases. As the resistance of the FET device increases, current threshold ITH decreases. Resistance of the FET device may also increase due to device degradation over time. Furthermore, as the thyristor device junction temperature increases, the gate voltage threshold of the thyristor device decreases. The exemplary power switch reduces power losses by regularly adjusting the voltage threshold used to determine whether the thyristor device should be turned on.

With reference to <FIG>, there is a flowchart illustrating an exemplary process <NUM> for operating an exemplary power switch, such as power switch <NUM>. It shall be appreciated that a number of variations and modifications to process <NUM> are contemplated including, for example, the omission of one or more aspects of process <NUM>, the addition of further conditionals and operations, and/or the reorganization or separation of operations and conditionals into separate processes.

Process <NUM> begins at operation <NUM> where a controller operates the power switch in a power switch off condition such that the FET-based branch and the thyristor-based branch are turned off. It shall be appreciated that the FET-based branch is turned off by the controller when at least one FET device of the FET-based branch is turned off so as to substantially eliminate the flow of current through the FET-based branch. Similarly, the FET-based branch is turned on by the controller when at least one FET device of the FET-based branch is turned on so as to allow the flow of current through the FET-based branch. It shall be appreciated that the thyristor-based branch is turned off by the controller when at least one thyristor device of the thyristor-based branch is turned off effective to substantially eliminate the flow of current through the thyristor-based branch. Similarly, the thyristor-based branch is turned on by the controller when at least one thyristor device of the thyristor-based branch is turned on effective to allow the flow of current through the thyristor-based branch. The controller may operate the power switch in the power switch off condition by turning off at least one switch of the FET-based branch and the thyristor-based branch, or by controlling at least one switch of the FET-based branch and the thyristor-based branch to remain in an off condition.

Process <NUM> proceeds to conditional <NUM> where the controller determines whether an instruction to turn on the power switch has been received. Instructions may be received by an external control system, such as an intelligent electronic device (IED), or may be generated by the controller. If the instruction was not received, process <NUM> enters a loop whereby process <NUM> returns to operation <NUM> where the power switch remains in the power switch off condition while regularly performing conditional <NUM> until the turn-on instruction is received. Once the turn-on instruction is received, process <NUM> proceeds to a FET control subprocess <NUM> and thyristor control subprocess <NUM> such that subprocess <NUM> and subprocess <NUM> are executed simultaneously until the controller receives an instruction to turn off the power switch.

During subprocess <NUM>, process <NUM> proceeds first to operation <NUM> where the controller turns on the FET-based branch. Process <NUM> proceeds to conditional <NUM> where the controller determines whether an instruction to turn off the power switch has been received. If the instruction was not received, process <NUM> enters a loop whereby process <NUM> returns to operation <NUM> where the FET-based branch remains turned on in the power switch on condition while regularly performing conditional <NUM> until the turn-off instruction is received. Once the turn-off instruction is received, process <NUM> proceeds to operation <NUM> where the controller turns off the FET-based branch. Process <NUM> then exits subprocess <NUM> and returns to operation <NUM>.

During subprocess <NUM>, process <NUM> proceeds first to conditional <NUM> where the controller determines whether an instruction to turn off the power switch has been received. If the turn-off instruction was received, process <NUM> exits subprocess <NUM> and returns to operation <NUM>. If the turn-off instruction has not been received, process <NUM> proceeds to operation <NUM>.

During operation <NUM>, the controller determines a thyristor forward voltage VAK while the FET-based branch is turned on and the thyristor-based branch is turned off. For example, the controller may determine voltage VAK by measuring across an anode and a cathode of a thyristor device of the thyristor-based branch using a voltage sensor. In another example, the controller may determine voltage VAK by measuring a first line-to-ground voltage at the anode of a thyristor device, measuring a second line-to-ground voltage at the cathode of the thyristor, and determining voltage VAK using the first and second line-to-ground voltage measurements.

The controller stores the most recently determined voltage VAK, as well as previously determined voltages VAK. For example, the voltage VAK may be stored in a vector such that VAK[n] is the most recently determined VAK, VAK[n-<NUM>] is the second most recently determined VAK, and so on. Each time a new voltage VAK is determined, n is incremented such that the previous VAK[n] becomes VAK[n-<NUM>].

Process <NUM> proceeds to conditional <NUM> where the controller determines whether a thyristor device turn-on condition is occurring. If the controller determines a thyristor device turn-on condition is not occurring, process <NUM> returns to conditional <NUM>. If the controller determines a thyristor device turn-on condition is occurring, process <NUM> proceeds to operation <NUM>.

The controller may determine a thyristor device is ready to be turned on, i.e. a turn-on condition is occurring, if the voltage VAK[n] is greater than a thyristor voltage threshold, the thyristor device is turned off, and the magnitude of the current flowing through the power switch is increasing. For the initial execution of conditional <NUM>, the thyristor voltage threshold may be a value stored in memory of the controller based on a device data sheet, to name but one example. The controller will not attempt to turn on the thyristor device if the forward voltage is less than the thyristor voltage threshold. As explained in more detail below, the thyristor voltage threshold is updated each time the controller determines a thyristor device turn-on condition is occurring.

The controller may determine the current conducted through the power switch is increasing by determining VAK[n] is greater than VAK[n-<NUM>]. The controller will not turn on the thyristor device unless the current is increasing to ensure the thyristor device is turned on before a peak current flows through the power switch.

During operation <NUM>, the controller turns on the thyristor device of the thyristor-based branch. In order to turn on the thyristor device, the controller transmits a pulse to the gate of the thyristor device while the forward voltage of the thyristor device is greater than the instant forward voltage threshold of the thyristor device. The gate pulse includes a current magnitude greater than a gate current threshold value for the thyristor device. The width of the gate pulse is a time period Ton of sufficient length to turn on the thyristor device.

Process <NUM> proceeds to operation <NUM> where the controller waits to update the thyristor threshold voltage until after the controller has finished transmitting the gate pulse to the thyristor device. After a delay of at least time period Ton, the controller proceeds to operation <NUM>.

During operation <NUM>, the controller updates the thyristor threshold voltage based on a voltage across the thyristor device measured immediately after the gate pulse terminates. Once the thyristor device is triggered successfully, the voltage drop across the combination of FET and thyristor devices is very nearly equal to the thyristor threshold voltage since the current through the thyristor device is small, just after the trigger instant. The thyristor threshold voltage may be determined using the following equation, where VTH is the thyristor voltage threshold, VAK is the forward voltage across the thyristor device, n is the measurement index of the forward voltage VAK used in conditional <NUM>, Ton is the time width of the gate pulse, Ts is the sampling rate of the measurements taken to determine VAK, and Vmargin is a noise margin voltage.

Vmargin is added to the forward voltage measurement immediately after the gate pulse terminates to determine an updated thyristor threshold voltage. Vmargin is a noise margin configured to reduce erroneous thyristor device triggers. Vmargin may be a voltage in a range between <NUM> and <NUM> mV, to name but one example.

Process <NUM> proceeds from operation <NUM> to operation <NUM> where the thyristor device is turned off. It shall be appreciated that the thyristor device is turned off at the next current zero-crossing after the controller removes the gate pulse to the thyristor device. Therefore, the controller may be said to turn off the thyristor device by withholding a gate pulse of a conducting thyristor device at the time of a current zero-crossing. Process <NUM> then returns to conditional <NUM>. Process <NUM> continues to execute subprocess <NUM> until the controller receives a turn-off instruction.

With reference to <FIG>, there is illustrated a plurality of graphs <NUM> illustrating electrical characteristics of exemplary power switch <NUM> controlled using exemplary process <NUM> for a time period between t<NUM> and t<NUM>. The plurality of graphs <NUM> includes a graph <NUM> illustrating current flowing through power switch <NUM>, a graph <NUM> illustrating voltage across power switch <NUM>, and a graph <NUM> illustrating power switch <NUM> power loss. During the time period between t<NUM> and t<NUM>, the controller operates the power switch using an initial thyristor threshold voltage. During the time period between t<NUM> and t<NUM>, the controller operates power switch <NUM> using an updated thyristor threshold voltage.

Current graph <NUM> includes a current line <NUM> illustrating the magnitude of current flowing through FET-based branch <NUM>; a current line <NUM> illustrating the magnitude of current flowing through thyristor-based branch <NUM>; and combined current line <NUM> illustrating the total current flowing through power switch <NUM>.

Voltage graph <NUM> includes a voltage line <NUM> illustrating a magnitude of voltage across power switch <NUM>; an initial voltage threshold line <NUM> illustrating the initial thyristor voltage threshold used determine whether the thyristor device should be turned on between time periods t<NUM>-t<NUM>; and an updated voltage threshold line <NUM> illustrating the updated thyristor voltage threshold used to determine whether the thyristor device should be turned on between time periods t<NUM>-t<NUM>. At times t<NUM> and t<NUM>, a thyristor device is turned on using the initial thyristor voltage threshold. At times t<NUM> and t<NUM>, a thyristor device is turned on using the updated thyristor voltage threshold. As illustrated in graph <NUM>, the updated voltage threshold is lower than the initial voltage threshold and closer to the forward voltage necessary to turn on the thyristor device, causing the power switch to turn on the thyristor device when the magnitude of the current through the FET-based branch is less than when the thyristor device is turned on using the initial thyristor voltage threshold.

Power graph <NUM> includes a power loss line <NUM> illustrating the power losses caused by current flowing through power switch <NUM>. It is important to note that at t<NUM>, when the thyristor device is turned on using the updated thyristor threshold voltage, the power loss of power switch <NUM> reduces relative to the power loss during the time period between t<NUM>-t<NUM> when the controller was not using the updated thyristor threshold voltage.

With reference to <FIG>, there is illustrated an exemplary power switch <NUM> including a controller <NUM>, a FET-based branch <NUM>, and a thyristor-based branch including a thyristor device <NUM> and thyristor device <NUM>. Controller <NUM> is structured to receive power from a power source, receive a command signal from a control device, receive measurements of electrical characteristics of power switch <NUM>, and output control signals to controllable devices of power switch <NUM> using the received power, the received command signal, and the received measurements.

Controller <NUM> includes isolated power supplies <NUM>, <NUM>, and <NUM> being coupled between a power source and a gate drive of controller <NUM>. The power source may be structured to output alternating current (AC) power or direct current (DC) power. The power source may be a utility grid, a facility grid, or a generator, to name but a few examples. Each isolated power supply is structured to receive power from the power source and output a power signal isolated from the received power to one of the gate drivers of controller <NUM>. The power signal may be isolated using a transformer, to name but one example.

Controller <NUM> includes opto-isolators <NUM>, <NUM>, and <NUM>, also known as optical couplers or optocouplers. Each opto-isolator is structured to receive a signal and output an isolated signal based on the received signal, the isolated signal being isolated using light. Opto-isolator <NUM> receives a command signal from a device external to the controller. Opto-isolators <NUM> and <NUM> receive an output signal from a processing device <NUM>.

Controller <NUM> includes analog isolators <NUM> and <NUM>, each structured to receive a measurement signal from a measuring device of controller <NUM> and output an isolated signal based on the received measurement signal. The isolated signal may be isolated from the measurement signal using a transformer or an opto-isolator, to name but a few examples. Since the frequency of the measurement signal is the same as the grid frequency, the bandwidth requirement for the analog isolators is low.

Controller <NUM> includes measuring devices <NUM> and <NUM>, each measuring device being structured to measure an electrical characteristic of a thyristor device of power switch <NUM>. In the illustrated embodiment, measuring device <NUM> is structured to measure a voltage from an anode of thyristor device <NUM> to a ground of gate driver <NUM>, and output a measurement signal based on the measured voltage. In the illustrated embodiment, measuring device <NUM> is structured to measure a voltage from an anode of the thyristor device <NUM> to a ground of gate driver <NUM>, and output a measurement signal based on the measured voltage. Before outputting each measurement signal, measuring devices <NUM> and <NUM> remove any portions of measurement signal corresponding to a negative voltage across the corresponding thyristor device.

Controller <NUM> includes a plurality of gate drivers including FET gate driver <NUM>, thyristor device gate driver <NUM>, and thyristor device gate driver <NUM>. Each gate driver receives a power signal from an isolated power supply and a command signal. Gate driver <NUM> uses the power signal and the command signal to output a control signal to the switches of FET-based branch <NUM> effective to turn on or turn off the switches of FET-based branch <NUM> based on the received command signal. Gate driver <NUM> uses the power signal and the command signal received from processing device <NUM> to output a control signal to thyristor device <NUM> effective to operate thyristor device <NUM>. Gate driver <NUM> uses the received power signal and the command signal received from processing device <NUM> to output a control signal to thyristor device <NUM> effective to operate thyristor device <NUM>.

Processing device <NUM> is structured to receive the measurement signal from measuring device <NUM> by way of analog isolator <NUM>, receive the measurement signal from measuring device <NUM> by way of analog isolator <NUM>, and receive the command signal. Using the received signals, processing device <NUM> is structured to generate and output a control signal to thyristor device gate driver <NUM> and thyristor device gate driver <NUM>. Processing device <NUM> generates the control signal based on an exemplary control process, such as process <NUM> in <FIG>.

Controller <NUM> includes isolated power supplies <NUM>, <NUM>, and <NUM> being coupled between a power source and a gate drive of controller <NUM>. The power source may be structured to output AC power or DC power. The power source may be a utility grid, a facility grid, or a generator, to name but a few examples. Each isolated power supply is structured to receive power from the power source and output a power signal isolated from the received power to one of the gate drivers of controller <NUM>. The power signal may be isolated using a transformer, to name but one example.

Controller <NUM> includes measuring device <NUM> structured to measure an electrical characteristic of the thyristor-based branch of power switch <NUM>. In the illustrated embodiment, measuring device <NUM> is structured to measure a voltage across both thyristor devices <NUM>, <NUM> and output a measurement signal based on the measured voltage to a level shifter <NUM>. The portions of the measurement signal corresponding to a negative voltage are level shifted.

Processing device <NUM> may include a microcontroller or a microprocessor, to name but a few examples. Processing device <NUM> is structured to receive the level-shifted measurement signal from level shifter <NUM> and receive the command signal. The portion of the level shifted measurement signal corresponding to negative voltage across the thyristor devices is received by an analog to digital converter (ADC) of processing device <NUM> and subtracted from a reference voltage level of the ADC, effectively rectifying the measurement signal. Using the received signals, processing device <NUM> is structured to generate and output a control signal to thyristor device gate driver <NUM> and thyristor device gate driver <NUM>. Processing device <NUM> generates the control signal based on an exemplary control process, such as process <NUM> in <FIG>.

Further written description of a number of exemplary embodiments shall now be provided. One embodiment is an apparatus comprising: a thyristor-based branch including a thyristor device; a FET-based branch coupled in parallel with the thyristor-based branch and including a FET device; and a controller structured to turn on the FET device, turn on the thyristor device after turning on the FET device based on a thyristor voltage threshold, and update the thyristor voltage threshold based on a voltage measurement corresponding to the thyristor-based branch measured while the thyristor device is turned on.

In certain forms of the foregoing apparatus, the controller is structured to turn on the thyristor device in response to determining a second voltage measurement is greater than the thyristor voltage threshold. In certain forms, the controller is structured to turn on the thyristor device also in response to determining the thyristor device is turned off and determining a current flowing through the FET-based branch is increasing. In certain forms, the controller includes a voltage sensor structured to transmit a series of voltage measurements at a sampling rate, the series of voltage measurements including the first voltage measurement and the second voltage measurement. In certain forms, the controller is structured to turn on the thyristor device by transmitting a gate pulse to the thyristor device, and wherein the updated thyristor threshold voltage is equal to a sum of a voltage margin and the voltage measurement of the series of voltage measurements taken after the gate pulse terminates. In certain forms, the controller is structured to turn on the thyristor device by transmitting a gate pulse to the thyristor device, and wherein the controller updates the thyristor threshold voltage using the following equation, where VTH is the updated thyristor voltage threshold, VAK is the series of voltage measurements, n is an index number of the second voltage measurement, Ton is a width of the gate pulse, Ts is the sampling rate of the series of measurements, and Vmargin is a noise margin voltage: <MAT> In certain forms, the controller is structured to turn off the thyristor device, and then turn on the thyristor device using the updated thyristor threshold voltage.

Another exemplary embodiment is a method comprising: operating a thyristor-based branch including a thyristor device and a FET-based branch coupled in parallel with the thyristor-based branch and including a FET device; turning on the FET device; turning on the thyristor device after turning on the FET device based on a thyristor voltage threshold; receiving a voltage measurement measured while the thyristor device is turned on; and updating the thyristor voltage threshold based on the voltage measurement. In certain forms of the foregoing method, turning on the thyristor device in response to determining a second voltage measurement is greater than the thyristor voltage threshold. In certain forms, turning on the thyristor device is also in response to determining the thyristor device is turned off and determining a current flowing through the FET-based branch is increasing. In certain forms, the method comprises operating a controller including a voltage sensor structured to transmit a series of voltage measurements at a sampling rate, the series of voltage measurements including the first voltage measurement and the second voltage measurement. In certain forms, turning on the thyristor device includes transmitting a gate pulse to the thyristor device, and wherein the updated thyristor threshold voltage is equal to a sum of a noise margin voltage and the voltage measurement of the series of voltage measurements taken after the gate pulse terminates. In certain forms, turning on the thyristor device includes transmitting a gate pulse to the thyristor device, and wherein updating the thyristor threshold voltage includes using the following equation, where VTH is the updated thyristor voltage threshold, VAK is the series of voltage measurements, n is an index number of the second voltage measurement, Ton is a width of the gate pulse, Ts is the sampling rate of the series of measurements, and Vmargin is a noise margin voltage: <MAT> In certain forms, the method comprises turning off the thyristor device; and turning on the thyristor device using the updated thyristor threshold voltage.

A further exemplary embodiment is a controller for a power switch including a FET device and a thyristor device, the controller comprising: a voltage sensor structured to output a series of voltage measurements corresponding to a voltage of the thyristor device including a first voltage measurement; and a processing device structured to execute a set of instructions effective to turn on the FET device, turn on the thyristor device after turning on the FET device based on a thyristor voltage threshold, update the thyristor voltage threshold based on the first voltage measurement measured while the thyristor device is turned on, turn off the thyristor device, and turn on the thyristor device using the updated thyristor threshold voltage.

In certain forms of the foregoing controller, the controller is structured to turn on the thyristor device in response to determining a second voltage measurement of the series of voltage measurements is greater than the thyristor voltage threshold. In certain forms, the controller is structured to turn on the thyristor device also in response to determining the thyristor device is turned off and determining a current flowing through the FET device is increasing. In certain forms, the controller is structured to turn on the thyristor device by transmitting a gate pulse to the thyristor device. In certain forms, the updated thyristor threshold voltage is equal to a sum of a voltage margin and the voltage measurement of the series of voltage measurements taken after the gate pulse terminates. In certain forms, the controller updates the thyristor threshold voltage using the following equation, where VTH is the updated thyristor voltage threshold, VAK is the series of voltage measurements, n is an index number of the second voltage measurement, Ton is a width of the gate pulse, Ts is the sampling rate of the series of measurements, and Vmargin is a noise margin voltage: <MAT>.

It is contemplated that the various aspects, features, processes, and operations from the various embodiments may be used in any of the other embodiments unless expressly stated to the contrary. Certain operations illustrated may be implemented by a computer including a processing device executing a computer program product stored on a non-transient, computer-readable storage medium, where the computer program product includes instructions causing the processing device to execute one or more of the operations, or to issue commands to other devices to execute one or more operations.

Claim 1:
An apparatus (<NUM>, <NUM>, <NUM>) comprising:
a thyristor-based branch (<NUM>) including a thyristor-type device (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
a FET-based branch (<NUM>, <NUM>, <NUM>) coupled in parallel with the thyristor-based branch (<NUM>) and including an FET-type device (<NUM>, <NUM>); and
a controller (<NUM>, <NUM>, <NUM>) structured to
turn on the FET-type device (<NUM>, <NUM>),
turn on the thyristor-type device (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) by transmitting a gate pulse to the gate of the FET-type device (<NUM>, <NUM>) based on a thyristor voltage threshold (<NUM>, <NUM>) that is greater than the instant forward voltage threshold of the thyristor device (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), and
update the thyristor voltage threshold (<NUM>) based on a first voltage across the thyristor device measured immediately after the gate pulse terminates.