AIRCRAFT SOLID SATE POWER CONTROLLER AND AIRCRAFT ELECTRIC POWER SUPPLY SYSTEM

An aircraft solid state power controller for controlling electric power in an aircraft comprises: a solid state power switching device for switching the electric power, the solid state power switching device comprising an input node, an output node and a control node; a first bypass diode electrically connected between the input node of the solid state power switching device and the control node of the solid state power switching device; and a switchable bypass electrically connected between the input node of the solid state power switching device, and he output node of the solid state power switching device. The switchable bypass comprises a second bypass diode and a bypass switch. An electric bypass current (Ibypass) flowing through the second bypass diode is switchable by switching the bypass switch on and off. The aircraft solid state power controller further comprises a bypass controller configured for switching the bypass switch on/off.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. 102022122243.8 filed Sep. 2, 2022, the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The invention is related to aircraft solid state power controller (“SSPC”) for controlling the supply of electric power from an electric power supply to at least one electric load within an aircraft. The invention is further related to an aircraft electric power supply system that comprises such an SSPC.

BACKGROUND

Modern aircraft usually comprise at least one aircraft solid state power controller (“SSPC”) for controlling the supply of electric power from an electric power supply to at least one electric load within an aircraft. The at least one SSPC may in particular be configured to act as an electric safety device or circuit breaker, which interrupts the supply of electric power in case the electric current flowing through the SSPC exceeds a predefined threshold. When the supply of electric power to an inductive load that is electrically connected to the SSPC is interrupted, relatively high inductive voltages may be induced. Such inductive voltages may damage components of the SSPC or other electric components, which are electrically connected to the SSPC. High inductive voltages may in particular damage switched off solid state power switching devices that are employed within the SSPC for controlling the supply of electric power to the at least one electric load.

It therefore would be beneficial to provide an improved SSPC, which is capable of controlling and switching electric loads without being damaged, in particular without being damaged by high inductive voltages that are induced by inductive loads, when the electric power supplied by the SSPC is switched off.

SUMMARY

According to an exemplary embodiment of the invention, an SSPC for controlling the supply of electric power from an electric power supply to at least one electric load within an aircraft comprises a solid state power switching device for switching the electric power, a first bypass diode, and a switchable bypass. The solid state power switching device comprising an input node, an output node and a control node. The first bypass diode has a first node, which is electrically connected to the input node of the solid state power switching device, and a second node, which is electrically connected to the control node of the solid state power switching device.

The switchable bypass has a first node, which is electrically connected to the input node of the solid state power switching device, and a second node, which is electrically connected to the output node of the solid state power switching device. The switchable bypass comprises a second bypass diode and a bypass switch. The second bypass diode and the bypass switch are electrically connected with each other in a serial configuration so that an electric bypass current flowing through the second bypass diode is controllable by switching the bypass switch between a low resistance state (“on-state”) and a high resistance state (“off-state”). The SSPC further comprises a bypass controller, which is configured for controlling the bypass switch, i.e. for switching the bypass switch between the low resistance on-state and the high resistance off-state.

Exemplary embodiments of the invention further include an aircraft electric power supply system comprising at least one electric load and at least one electric power supply for supplying electric power to the at least one electric load. The aircraft electric power supply system further comprises at least one SSPC according to an exemplary embodiment of the invention, which allows controlling, in particular switching, the supply of electric power from the at least one electric power supply to the at least one electric load.

Exemplary embodiments of the invention further include an aircraft with an aircraft electric power supply system according to an exemplary embodiment of the invention.

Exemplary embodiments of the invention also include a method of switching off an SSPC according to an exemplary embodiment of the invention, wherein the method includes: switching the bypass switch into a low resistance on-state in order to allow bypassing the solid state power switching device via the second bypass diode; and switching the solid state power switching device into a high resistance off-state, in which it does not supply any electric power to the at least one load. In a method according to an exemplary embodiment of the invention, the bypass switch is then switched into a high resistance off-state a predetermined period of time after the solid state power switching device has been switched into the high resistance off-state.

Alternatively or additionally to switching off the bypass switch after a predetermined amount of time, the method may include measuring the voltage between the input node and the output node of the solid state power switching device, comparing the measured voltage with a predefined threshold, and switching the bypass switch into the high resistance off-state when the measured voltage has dropped below the predefined threshold.

Activating the switchable bypass before the solid state power switching device is switched off allows dissipating the inductive voltage that is induced by the inductive load when the solid state power switching device is switched off through the second bypass diode of the switchable bypass. Dissipating the inductive voltage allows preventing that the solid state power switching device or any other electric components, which are electrically connected to the solid state power switching device, are damaged by the induced voltage and/or an induced electric current that is driven by the induced voltage, when the solid state power switching device is switched off.

According to the invention, the switchable bypass is deactivated after some time, after a considerable portion of the induced voltage has been dissipated, in order to prevent an undesirable overshooting of the bypass, which may result in an infinite clamping.

As a result, an SSPC according to an exemplary embodiment of the invention provides a reliable and durable SSPC, which is able to switch large electric powers, in particular high electric voltages of up to several thousands of volts and/or large electric currents of up to several thousands of amperes, without being damaged and without damaging electric components that are electrically connected to the SSPC.

The first and second bypass diodes may be semiconductor diodes. Semiconductor diodes provide reliable and durable diodes, which may be designed to withstand large electric loads, in particular high electric voltages and/or large electric currents. Semiconductor diodes are not affected by accelerations and vibrations, as they occur in an aircraft. They also have a long lifetime and may be produced at reasonable costs.

The solid state power switching device may be or may include an insulated-gate bipolar transistor (IGBT) or a field-effect transistor (FET), in particular a metal-oxide-semiconductor field-effect transistor (MOSFET). Insulated-gate bipolar transistors and field-effect transistors, in particular metal-oxide-semiconductor field-effect transistors, provide reliable and durable solid state power switching devices, which are capable to switch large electric loads, in particular high electric voltages and/or large electric currents. Such transistors are not affected by accelerations and vibrations, as they occur in an aircraft. They also have a long lifetime and are available at reasonable costs.

If the solid state power switching device is a FET or a MOSFET, the first node of the first bypass diode may be electrically connected to the source of the FET or MOSFET and the second node of the first bypass diode may be electrically connected to the gate of the FET or MOSFET. In an alternative configuration, the first node of the first bypass diode may be electrically connected the drain of the FET or MOSFET, and the second node of the first bypass diode may be electrically connected to the gate of the FET or MOSFET.

In case the solid state power switching device is a FET or MOSFET, the first node of the switchable bypass may be electrically connected to the source of the FET or MOSFET, and the second node of the switchable bypass may be electrically connected to the drain of the FET or MOSFET. Alternatively, the first node of the switchable bypass may be electrically connected to the drain of the FET or MOSFET, and the second node of the switchable bypass may be electrically connected to the source of the FET or MOSFET.

The most appropriate of these configurations may be chosen based on the circumstances, such as the polarity of the voltage, which is to be switched by the solid state power switching device and/or the availability and configuration of the electric components, in particular the solid state power switching device.

The first and second bypass diodes may be Zener diodes or transient voltage suppressor diodes (“TVS diodes”), which are electrically connected to be operated in their respective blocking directions.

The second bypass diode may be a high power TVS diode, which is capable of withstanding transient voltages of up to 3000 V and transient currents of up to 10 kA.

The first bypass diode may have a first breakdown voltage Ubreak1 in the range of 1500 V to 2000 V, and the second bypass diode may have a second breakdown voltage Ubreak2 in the range of 1000 V to 3000 V.

In order to provide an SSPC that is capable to control very large electric powers, for example controlling electric powers of at least 250 kW, in particular to withstand electric powers of at least 500 kW, the second bypass diode may be configured to be able to withstand electric powers of at least 250 kW, in particular to withstand electric powers of at least 500 kW.

The SSPC, and in particular the solid state power switching device, may be configured to be able to switch electric voltages in the range of 1500 V to 3000 V, in particular for switching electric voltages in the range of 2000 V to 2500 V.

The SSPC, and in particular the solid state power switching device, may be configured to be able to switch electric currents in the range of 1000 A to 2000 A, in particular to switch electric voltages in the range of 1200 A to 1700 A.

The bypass switch, which is employed for activating and deactivating the switchable bypass, may also include a semiconductor switch. The bypass switch may, for example, include an IGBT or an FET, in particular a MOSFET. Such semiconductor switches provide reliable and durable switches, which are able to switch large electric loads and which are not affected by accelerations and/or vibrations, at reasonable costs.

The bypass controller may be configured for driving the bypass switch time-controlled. More specifically, the bypass controller may be configured for deactivating the bypass by switching off the bypass switch a predetermined period of time ΔT after the solid state power switching device has been switched off. Said predetermined period of time ΔT may, for example, be in a range of between 100 μs and 10 ms, in particular in a range of between 500 μs and 5 ms.

Driving the bypass switch time-controlled allows for a simple and inexpensive implementation of the bypass controller. In particular, no additional components, such as sensors, are necessary for driving the bypass switch time-controlled.

The SSPC may also comprise a voltage sensor for measuring the voltage between the input node and the output node of the solid state power switching device, which is defined by the breakdown voltage of the second bypass diode (TVS diode). In such a configuration, the bypass controller may be configured for driving the bypass switch based on the voltage measured by the voltage sensor. Driving the bypass switch based on the voltage measured by the voltage sensor allows deactivating the switchable bypass as soon as the voltage between the input node and the output node of the switchable bypass has dropped below a predefined threshold.

The bypass controller may, for example, be configured for deactivating the switchable bypass by switching off the bypass switch when the voltage measured by the voltage sensor has dropped below 1500 V.

DETAILED DESCRIPTION

FIG.1shows an aircraft24, in particular an airplane, which is equipped with an electric power supply system2including an electric power supply4, an electric load6, and an aircraft solid state power controller (SSPC)5according to an exemplary embodiment of the invention. Although the electric power supply system2depicted inFIG.1, includes only on electric power supply4, one electric load6, and one SSPC with a single SSPC channel.

Typical embodiments of electric power supply systems2may comprise more the one of each of said components, respectively.

An electric power supply system2may in particular include a plurality of SSPCs, with each SSPC including numerous SSPC channels of the type depicted inFIG.1and described in the following.

FIG.2shows a circuit diagram of the electric power supply system2depicted inFIG.1. The electric power supply system2comprises an electric power supply4, in particular a DC electric power supply4, an electric load6, which includes a resistive component R and an inductive component L, and an SSPC (or an SSPC channel)5according to an exemplary embodiment of the invention.

In the embodiment depicted inFIG.2, the electric load6is connected between the positive pole of the DC electric power supply4and the SSPC5. In an alternative embodiment, which is not explicitly shown in the figures, the electric load6may be connected between the negative pole of the DC electric power supply4and the SSPC5.

The electric load6may be selectively supplied with electric power from the electric power supply4by controlling, in particular by switching, the SSPC5.

The SSPC5comprises a solid state power switching device10, which is configured for controlling/switching the electric power that is supplied by the electric power supply4to the electric load6. Th solid state power switching device10may be an insulated-gate bipolar transistor (IGBT) or a field effect transistor (FET), in particular a metal-oxide-semiconductor field-effect transistor (MOSFET).

The solid state power switching device may be configured for switching electric voltages in the range of 1500 V to 3000 V, in particular for switching electric voltages in the range of 2000 V to 2500 V.

The solid state power switching device may be configured for switching electric currents in the range of 1000 A to 2000 A, in particular for switching electric voltages in the range of 1200 A to 1700 A.

The solid state power switching device10has an input node10a, an output node10band a control node10c.

In case the solid state power switching device10is an IGBT, the input node10amay be the collector or the emitter of the IGBT, and the output node10bmay be the other one of the collector an the emitter. The control node10cmay be the gate of the IGBT.

In case the solid state power switching device10is a FET or a MOSFET, as it is depicted inFIG.2, the control node10cmay be the gate of the FET/MOSFET.

The input node10amay be the source of the FET/MOSFET, and the output node10bmay be the drain of the FET/MOSFET. Alternatively, the input node10amay be the drain of the FET/MOSFET, and the output node10bmay be the source of the FET/MOSFET.

The SSPC5further comprises a first bypass diode12having a first node12aand a second node12b. The first bypass diode12may be a semiconductor diode.

The first node12aof the first bypass diode12is electrically connected to the input node10aof the solid state power switching device10. The second node12bof the first bypass diode12is electrically connected to the control node10cof the solid state power switching device10.

The first bypass diode12is a Zener-Diode or a TVS diode having a first breakdown voltage Ubreak1. The first breakdown voltage Ubreak1 is an intrinsic parameter of the first bypass diode12. The first bypass diode12is electrically connected in its blocking direction to the solid state power switching device10. In consequence, under normal operating conditions, when the voltage applied to the first bypass diode12in its blocking direction, is below the first breakdown voltage Ubreak1, the first bypass diode12ablocks and appears as an open electric circuit.

When the electric voltage, which is applied to the first bypass diode12in its blocking direction, exceeds the first breakdown voltage Ubreak1, the first bypass diode12avalanches and provides a low impedance electric path between its two nodes12a,12b. In consequence, the first bypass diode12appears as a closed electric circuit and an electric voltage is applied to the control input10cof the solid state power switching device10.

The SSPC5further comprises a switchable bypass with a first bypass node8aand a second bypass node8b.

The first bypass node8ais electrically connected to the input node10a(e.g. the source or the drain) of the solid state power switching device10, and the second bypass node8bis electrically connected to the output node10c(e.g. the drain or the source) of the solid state power switching device10.

The switchable bypass8comprises a second bypass diode16and a bypass switch18. The bypass switch18may be or may include a semiconductor switch, such as an IGBT, a FET or a MOSFET.

The second bypass diode16and the bypass switch18are serially electrically connected with each other. In consequence, an electric bypass current flowing through the second bypass diode16is switchable by controlling the bypass switch18.

The second bypass diode16is a high power bypass diode, in particular a high power transient voltage suppressor diode (TVS diode). The second bypass diode16has a second breakdown voltage Ubreak2. The second breakdown voltage Ubreak2 is an intrinsic parameter of second first bypass diode16.

The second bypass diode16is electrically connected in its blocking direction. When an electric voltage that is below the second breakdown voltage Ubreak2 is applied to the second bypass diode16in its blocking direction, the second bypass diode16blocks any electric current from flowing through the second bypass diode16. In consequence, it appears as an open electric circuit.

When the electric voltage, which is applied to the second bypass diode16in its blocking direction, exceeds the second breakdown voltage Ubreak2, the second bypass diode16avalanches and provides a low impedance path between its two nodes. In consequence, the second bypass diode16appears as a closed electric circuit.

The second bypass diode16may have a second breakdown voltage Ubreak2 in the range of 1000 V to 3000 V, and is capable to handle electric currents of up to 10 kA. The second bypass diode16may in particular be configured to withstand electric powers of up to 250 kW, in particular to withstand electric powers of up to 500 kW.

The SSPC5further comprises a bypass switch controller20, which is configured for controlling the bypass switch18to switch between a high resistive on-state and a low resistive off-state.

In the following, an example of operating the SSPC5and in particular controlling the bypass switch18is described with reference toFIG.3.

FIG.3shows a graph, in in which the electric current I flowing through the electric load6and the electric voltage Ubypass between the input node10aand the output node10bof the solid state power switching device10are plotted on the vertical axis over time t, which is plotted on the horizontal axis. The electric current I is plotted as a dashed line, and the electric voltage Ubypass is plotted as a solid line.

During a first period of time T0<t1<T1, the solid state power switching device10is switched on, i.e. the solid state power switching device10is switched into a low resistance on-state, in which there is no significant electric potential difference or voltage Ubypass between the input node10aand the output node10bof the solid state power switching device10(Ubypass=0). (Due to the physical properties of the solid state power switching device10, there may be a small potential difference or voltage Ubypass of less than 3 V between the input node10aand the output node10b. This potential difference, however, is negligible in the context of the present invention.)

At t=T1, the electric current I, which flows through the electric load6, and which is indicated by the dashed line, reaches a predefined maximum value Imax. When the electric current I reaches the predefined maximum value Imax, the solid state power switching device10is switched into a high resistance off-state by an overelectric current detector or “electric current limiter”, which is not depicted inFIG.2.

Switching of the electric power that is supplied to the electric load6, induces an inductive voltage Uind in the inductive component L of the electric load6. The induced inductive voltage Uind adds to the voltage U0(“bus voltage U0”) supplied by the electric power supply4. This results in a relatively high voltage U1, which is the sum U1=Uind+U0of the induced inductive voltage Uind and the bus voltage U0, between the input node10aand the output node10bof the solid state power switching device10.

In order to prevent the solid state power switching device10(or another electric component of the SSPC2) from being damaged by a high induced inductive voltage Uind, the bypass switch18of the switchable bypass8has been switched on for activating the switchable bypass8before the solid state power switching device10has been switched off. As a result, the high voltage U1=Uind+U0is applied to the second bypass diode16.

If the high voltage U1exceeds the second breakdown voltage Ubreak2 of the second bypass diode16, which is usually the case, an induced electric current lind, which is driven by the high voltage U1, may bypass the solid state power switching device10through the switchable bypass8, i.e. through the second bypass diode16and the bypass switch18, which is switched on.

As a result of bypassing the solid state power switching device10via the second bypass diode16, the voltage U1between the input node10aand the output node10bof the solid state power switching device10drops during a second time period T1<t2T2.

Due to the physical properties of the second bypass diode (high power TVS diode)16, the induced electric current Iind flowing through the second bypass diode16causes the second breakdown voltage Ubreak2 of the second bypass diode16to drop during the second time period T1<t<T2. There is a risk that the second breakdown voltage Ubreak2 of the second bypass diode16drops even below the bus voltage U0. This would result in short-ciruiting the electric power supply4.

It has been found difficult or even impossible to select a second bypass diode16so has a suitable second breakdown voltage Ubreak2 at the beginning of the clamping, when the induced voltage Uind is high, and which also provides a sufficiently high second breakdown voltage Ubreak2 at the end of the clamping, when the induced voltage Uind is relatively low, in order to prevent short-ciruiting the electric power supply4.

According to the invention, this problem is solved by deactivating the switchable bypass8with the second bypass diode16by switching off the bypass switch18at a time t=T2.

The bypass switch18is controlled by a bypass switch controller20, which is configured for switching the bypass switch18on and off.

The bypass switch controller20may be configured for driving the bypass switch18time-controlled. In other words, the bypass switch controller20may be configured for switching off the bypass switch18a predetermined amount of time after the solid state power switching device10has been switched off. The bypass switch controller20may in particular be configured for switching off the bypass switch18after a time period ΔT=T2−T1, which is in the range of 100 μs to 10 ms, after the solid state power switching device10has been switched of g at time t=T2.

Alternatively or additionally, the bypass switch controller20may comprise a voltage sensor22, which is configured for detecting the voltage Ubypass between the first and second nodes8a,8bof the switchable bypass8. In such a configuration, the bypass switch controller20may be configured for switching off the bypass switch18, when the voltage Ubypass between the first and second nodes8a,8bof the switchable bypass8has dropped below a predefined voltage Uoff, for example below a predefined voltage Uoff of 1500 V.

After the switchable bypass8has been deactivated by switching off the bypass switch18, the solid state power switching device10is (at least partially) switched on, i.e. brought into an at least partially conducting low resistive state, during the following time period T2<t<T3by an electric voltage UG that is applied to the control input10cof the solid state power switching device10via the first bypass diode12. The first bypass diode12is conductive and applies an electric voltage UG to the control input10cof the solid state power switching device10as long as the voltage that is applied to the first bypass diode12exceeds the first breakdown voltage Ubreak1 of the first bypass diode12.

In consequence, the remaining induced voltage Uind, which is still present between the input and output nodes10a,10bof the solid state power switching device10after the bypass switch18has been switched off, is reduced further due to an electric current Iind, which flows though the solid state power switching device10until the voltage Ubypass1 applied to the first bypass diode12drops below the first breakdown voltage Ubreak1 of the first bypass diode12. When the voltage Ubypass1 applied to the first bypass diode12drops below the first breakdown voltage Ubreak1 of the first bypass diode12, the first bypass diode12blocks and no electric voltage is applied to the control input10cof the solid state power switching device10. In consequence, the solid state power switching device10is switched off.

At t=T3the induced inductive voltage Uind has been completely dissipated so that only the bus voltage U0, which is supplied by the electric power supply4, is applied to the input node10aand the output node10bof the solid state power switching device10.

In an SSPC5according to an exemplary embodiment of the invention, the electric current Iind dissipating the inductive voltage Uind, which is induced when the solid state power switching device10is switched off, flows through the second bypass diode16during the first time period T1<t<T2in which the electric bypass8is switched on. In the following second time period T2<t<T3, the electric bypass8is switched off and the remaining inductive voltage Uind is dissipated by an electric current Iind that flows through the solid state power switching device10, which is at least partially switched on due to a voltage that is applied to the control input10cof the solid state power switching device10via the first bypass diode12.

As the solid state power switching device10is (at least partially) switched on, only a small electric current, which is sufficient for switching on the solid state power switching device10, flows through the first bypass diode12. In consequence, the first bypass diode12does not need to be designed to withstand large electric currents. The first bypass diode12may therefore be a conventional Zener diode with a first breakdown voltage Ubreak1 in the range of 1500 V to 2000 V, and it its sufficient that it is capable to withstand transient electric currents of up to 10 kA.