Double-gate field-effect transistor and switching device comprising such a field-effect transistor

Abstract

Dual-gate field-effect transistor and switching device comprising such a field-effect transistor. The present invention relates to a junction field-effect transistor (100) with a side structure, comprising: - a support layer (10) of a first type of conductivity, - a semiconductor layer (14) of a second type of conductivity forming a channel, - a first electrode (e1) capable of forming a source or a drain, - a second electrode (e2) capable of forming a source or a drain, - a doped region (18) in contact with a gate connection terminal (g1) located between the first and second electrodes (e1, e2), the field-effect transistor (100) further comprising an additional doped region (20) in contact with another gate connection terminal (g2) located between the gate connection terminal (g1) and the second electrode (e2). (Figure 2)

Description

Title of the invention: Double-gate field-effect transistor and switching element comprising such a field-effect transistor

[0001] The present invention relates to the field of power electronics, and more specifically concerns a power transistor which has a particularly advantageous application in the automotive field.

[0002] As shown in [Fig. 1], electric or hybrid electric vehicles include a high-voltage battery to power an electric motor, generally three-phase, via an inverter. This high-voltage battery has a maximum open-circuit voltage of several hundred volts, for example 400V or 800V, hence its designation "high voltage" as opposed to the maximum open-circuit voltage of a standard vehicle battery, which is around 14V.

[0003] The high-voltage battery 30 is normally connected to a high-voltage network 300 of the vehicle, to which the inverter is connected, via a first contactor 32 and a second contactor 34. However, the high-voltage network 300 has at least a capacity 28 which must be pre-charged before closing the first and second contactors 32, 34 together, to avoid a current surge which would damage the high-voltage components of the vehicle.

[0004] The pre-charging of the capacitance 28 is carried out by a pre-charging circuit 50 comprising an inrush current limiting resistor 54 connected in series with a pre-charging contactor 52. This pre-charging circuit 50 is connected in parallel with the first contactor 32, which connects the high-voltage battery 30 to the high-voltage network 300. Thus, before closing the first contactor 32, the second contactor 34 and the pre-charging contactor 52 are closed first, then the pre-charging contactor 52 is opened, and the first contactor 32 is closed.

[0005] In the event of a fault on the high-voltage network 300, the first and second contactors 32, 34 must be able to open while carrying a significant current. Furthermore, a fuse 36 ensures a permanent break between the high-voltage battery 30 and the high-voltage network 300 in the event of a short circuit.

[0006] This system for connecting the high-voltage battery 30 to the high-voltage network 300, using contactors, is sometimes replaced by electronic switching components (or SSRs for "Solid State Relay"). These electronic switching components eliminate the need for a pre-charge circuit, by themselves limiting the inrush current through linear control of these switching components.

[0007] Furthermore, the electronic switching components are theoretically capable of performing an unlimited number of current interruptions between the high-voltage battery 30 and the high-voltage network 300, even when carrying a significant current. This is not the case for the contactors, whose contacts deteriorate during interruptions under current and eventually stick. They must therefore be systematically replaced when such an event occurs, for example, during a crash causing a short circuit in the high-voltage battery 30. However, since the contactors are often integrated with the high-voltage battery 30 in a housing called a "battery pack," this replacement requires removing the housing and therefore incurs a significant maintenance cost.

[0008] Finally, the electronic switching components provide a fault current limiting function, typically during a short circuit. This function prevents all the vehicle's high-voltage components from being transiently subjected to a very high fault current supplied by the high-voltage battery 30. This function is implemented by linear control of these components and allows the fuse 36 in the vehicle to be eliminated.

[0009] However, these electronic switching components are more expensive than the contactor-based connection system of [Fig. 1], primarily because several MOSFETs (metal-oxide-semiconductor field-effect transistors) are required per switching component to perform all these functions, as these transistors are not voltage bidirectional. The main failure mechanism of these components, especially when made of silicon carbide, is the degradation of their gate oxides. Although the failure rate associated with this mode is acceptable for applications such as an inverter or a charger, its elimination by a gate oxide-free technology would allow for safe applications without the need to add dedicated elements such as fuses or pyrotechnic devices.

[0010] The present invention aims to remedy at least in part the aforementioned drawbacks by providing in particular a field-effect transistor, a switching element comprising such a field-effect transistor and a method for managing the supply of energy in a high-voltage network of a vehicle, which make it possible to replace the mechanical switching of the battery contactors in a vehicle, by a reliable electronic switching using the switching element, the latter not needing to be replaced at each opening under current of the circuit linking the high-voltage battery of the vehicle to the high-voltage network of the vehicle.

[0011] To this end, the invention proposes a junction field-effect transistor with a lateral structure, comprising: - at least one support layer of a first type of conductivity, - at least one superimposed semiconductor layer of a second type of conductivity to the support layer and capable of forming a channel between a source and a drain, - a first electrode implanted on the semiconductor layer and capable of forming the source or the drain, - a second electrode implanted on the semiconductor layer and capable of forming the drain or the source, - a doped area according to the first type of conductivity in contact on one side with the semiconductor layer and on the other side with a gate connection terminal located between the first and second electrodes and electrically isolated from the first and second electrodes, the field-effect transistor being characterized in that it further comprises an additional area doped according to the first type of conductivity, in contact on the one hand with the semiconductor layer and on the other hand with another gate connection terminal located between the gate connection terminal and the second electrode, and electrically isolated from the gate connection terminal and the second electrode.

[0012] By "superimposed on the support layer", it is understood that the semiconductor layer is supported by the support layer, possibly via other semiconductor layers more or less doped and of the first or second type of conductivity. In particular, preferably the support layer is heavily doped, and a semiconductor layer of the first type of conductivity, less doped than the support layer and produced for example by epitaxy, is intercalated between the support layer and the semiconductor layer of the second type of conductivity.

[0013] Furthermore, the first and second electrodes are implanted on the semiconductor layer of the second type of conductivity via heavily doped regions of the second type of conductivity, these heavily doped regions forming part of the source or drain formed by one or the other of the first or second electrodes. The regions doped with the first type of conductivity in contact with the gate connection terminals are also preferably heavily doped and each form, with one of the gate connection terminals, a gate of the field-effect transistor according to the invention.

[0014] Furthermore, a first type of conductivity of type P is preferably used, that is to say, the type using a deficit of electrons in the material to conduct them, and a second type of conductivity of type N is preferably used, that is to say, the type using a surplus of electrons in the material to conduct them. This material is preferably silicon carbide (SiC), for example with a hexagonal Wurtzite 4H crystal structure, which makes the transistor more efficient due to the large energy of its band gap. These choices make it possible to obtain a field-effect transistor according to the invention that is inexpensive and efficient, that is to say, able to withstand up to 250V / qm (volts). per micrometer). Alternatively, the material used is gallium nitride, or diamond, which is much more expensive but very efficient (withstanding up to 1000V / m²).

[0015] Thanks to the invention, the field-effect transistor according to the invention forms a single component with two gates, which makes it bipolar in the sense that it is bidirectional in current and voltage and can, in particular, interrupt the current flowing through the field-effect transistor in either direction.When current flows through the field-effect transistor according to the invention in one direction, a control voltage is applied between one of the gate connection terminals and the first or second electrode used as a source. When current flows through the field-effect transistor according to the invention in the other direction, a control voltage is applied between the other gate connection terminal and the other first or second electrode, which will then in turn be used as a source. A control voltage is applied between the first or second electrode used as a source and the gate connection terminal closest to that electrode.

[0016] Compared to a two-MOSFET series structure for achieving bidirectional switching, the current in the field-effect transistor according to the invention flows through the resistance of only one channel instead of through both channels of the two MOSFET transistors. Thus, the power dissipation during operation of the field-effect transistor according to the invention is almost half that of the two-MOSFET structure.

[0017] Furthermore, thanks to the invention, a transistor with low failure rates is produced because it does not have a gate oxide. Indeed, the field-effect transistor according to the invention includes an insulating layer, for example made of silicon dioxide, which electrically isolates the electrodes and the gate connection terminals from each other, but this insulating layer does not function like a gate oxide and is therefore not subject to the same stresses. As a result, the field-effect transistor according to the invention has a failure rate (or "Failure In Time Rate," i.e., 10⁹ / MTBF, where MTBF is the mean time between two failures, also called "Mean Time Between Failure") of between 10⁹ and 10¹¹, which complies with the safety requirements related to the high-voltage network of an electric or hybrid vehicle. This failure rate is also much lower than that of an electromechanical structure with a fuse.

[0018] It should be noted that, given its lateral structure, the field-effect transistor according to the invention has a lower current density than an equivalent vertical MOSFET. However, considering the energy dissipation peaks that the field-effect transistor according to the invention must withstand during pre-charging phases of a high-voltage battery in a vehicle, or during current-driven opening, this lateral structure offers, compared to a field-effect transistor with vertical structure, a larger contact surface between the support layer and a re-cooler and therefore improves the heat exchange of the transistor according to the invention with this cooler.

[0019] Furthermore, this lateral structure facilitates the manufacturing process of the field-effect transistor according to the invention, as it can use etching, deposition, or epitaxial steps only on its top surface. Finally, due to its lateral structure and the absence of a gate oxide, the field-effect transistor according to the invention allows for greater tolerance to crystalline defects, and consequently a more favorable manufacturing scrap rate, which does not negatively impact the cost of this type of component compared to a smaller vertical MOSFET with a higher current density.

[0020] The invention also relates to a switching element comprising a field-effect transistor according to the invention, characterized in that it further comprises at least one enhancement MOSFET transistor, connected in series with the field-effect transistor in a cascode arrangement.

[0021] Thanks to the cascode configuration between the enhancement-mode MOSFET and the field-effect transistor according to the invention, the switching element is open, i.e., does not allow current to flow, when no control voltage is applied, either to one of the gate connection terminals of the field-effect transistor according to the invention or to the gate of the enhancement-mode MOSFET. Thus, the switching element according to the invention can be used in place of battery contactors in a vehicle, since it will leave the circuit connecting the vehicle's high-voltage battery to the vehicle's high-voltage network open when the vehicle is in standby mode, i.e., "asleep" or switched off. The enhancement-mode MOSFET is preferably a low-voltage transistor, for example, one that can withstand 16 or 25V.Thus, the cost of the switching device according to the invention should ultimately be lower than that of a prior art electronic switching component.

[0022] The invention also relates to a method for managing the energy supply in a high-voltage network connected to a high-voltage battery via at least one switching device according to the invention, the management method being characterized in that it comprises a step of activating the switching device comprising substeps of: - blocking of the field-effect transistor by applying a blocking voltage between one of the gate connection terminals and that of the first or second electrode used as the source of the field-effect transistor, - MOSFET transistor conduction, and - awaiting a request to close the shut-off device.

[0023] In this patent application, the cutting element is open when it prevents the The current flows, and the circuit is closed when it conducts current. The closing request therefore aims to close the circuit linking the high-voltage battery to the high-voltage network. The management method according to the invention is implemented, for example, in a vehicle computer, for example, in the vehicle's main computer, or in a dedicated computer. This computer is, for example, connected to a gate control circuit for the transistors constituting the switching element according to the invention.

[0024] Of course, the gate blocking voltage depends on whether the field-effect transistor according to the invention is N-type or P-type. Similarly, the MOSFET's turn-on voltage uses a control voltage whose value depends on whether the MOSFET in the switching element according to the invention is N-type or P-type.

[0025] Furthermore, during the blocking step, at least one blocking voltage is actually applied, since it is optionally applied to both gate connection terminals, that is, between each of the gate connection terminals and their nearest electrode. This option makes it possible to prevent current flow in both directions.

[0026] A control voltage, whether for blocking or turning off the transistor, is always applied between a gate connection terminal of the transistor and the transistor electrode proximal to that gate connection terminal. In the blocking stage, therefore, at least one blocking voltage is applied between the voltage of the first or second electrode used as the source of the field-effect transistor and the gate connection terminal proximal to that electrode.

[0027] In one embodiment of the invention, the management method according to the invention includes a pre-charge step of at least one capacitor connected to the high voltage network, the pre-charge step comprising a limitation of the current through the switching member by a progressive variation of the voltage between said one of the gate connection terminals and that of the first or second electrode used as the source of the field-effect transistor.

[0028] In this embodiment, the high-voltage network includes one or more capacitors requiring pre-charging before allowing all battery current to flow to the high-voltage network. This capacitor or these capacitors are connected downstream of the switching device(s), for example, by being connected in parallel to the terminals of the high-voltage network.

[0029] It should be noted that in this application, the terms "upstream" or "downstream" refer to the relative position of electrical components or assemblies with respect to the direction of the current flowing out of the high-voltage battery and towards consumers of the high-voltage battery, i.e., when the battery is discharging. Thus, a first component is upstream of a second component if the current flowing out of the high-voltage battery first passes through the first component and then the second component before entering the high-voltage battery.

[0030] Furthermore, the gradual variation of the voltage between said one of the gate connection terminals and that of the first or second electrode used as the source of the field-effect transistor corresponds to a gradual change from a value close to -15V to a value close to 0V if the field-effect transistor according to the invention is of type N, or a gradual change from a value close to +15V to a value close to 0V if the field-effect transistor according to the invention is of type P. This voltage variation is gradual in the sense that the control voltage does not go directly from -15V or 15V to 0V but takes intermediate values, the change from -15V or 15V to 0V taking several milliseconds, the field-effect transistor being traversed by a very large current. Of course, a conventional opening or closing without current flowing through the field-effect transistor can occur in less than a microsecond.

[0031] Alternatively, the pre-charge step involves sending current pulses to the high-voltage network, achieved by successively opening and closing the switching element. The openings of the switching element are preferably triggered by reaching a high current threshold through the switching element. This alternative allows for less energy dissipation during pre-charge than using only current limiting through progressive control of the control voltage of the field-effect transistor according to the invention.

[0032] In yet another alternative, the pre-charging step comprises: - a sub-step of sending current pulses on the high voltage network, achieved by successive closures and openings of the switching element, followed by - a sub-step of limiting the current through the switching element by a progressive variation of the voltage between said one of the grid connection terminals and that of the first or second electrode used as the source of the field-effect transistor.

[0033] This alternative combines the two previous pre-charge techniques and therefore offers the advantage of low energy dissipation while limiting current surges in the pre-charged capacitors. Preferably, the limiting sub-stage is triggered when the voltage across the high-voltage network reaches a high voltage threshold. The high voltage threshold is chosen to optimize the pre-charge stage in terms of performance; for example, it is set at a value between 70% and 90% of the battery voltage.

[0034] As with the blocking step, current limiting and / or current pulse sending are optionally carried out by modifying the two control voltages of the two gate connection terminals.

[0035] In one example of use of the invention, the management method according to the invention includes a step of opening the cutting element while it is being traversed by a non-zero current, the opening step comprising a control of the voltage between said one of the gate connection terminals and that of the first or second electrode used as source of the field-effect transistor as a function of the voltage across the terminals of the switching element and / or as a function of a variation of the current through the switching element as a function of time.

[0036] This control is preferably carried out on the two control voltages of the two grid connection terminals, since the non-zero current being due to a fault, it can come from the battery or the high voltage network.

[0037] This step of opening the current-controlled switching device occurs exceptionally when it is necessary to isolate the high-voltage battery while high-voltage equipment is still operating, for example, following a crash of a vehicle implementing the management method according to the invention. Since the impedance of the high-voltage network is inductive, the energy stored in the wiring and filters of the connected equipment must be dissipated, which is facilitated by the switching device according to the invention. The control of the control voltage in this step makes it possible to dissipate this energy without damaging the switching device, in particular without causing excessive overvoltage across the switching device. Alternatively, this control of the control voltage is based on the voltage across the field-effect transistor and / or on a variation of the current flowing through the switching device over time.

[0038] This control can be conditional upon the current flowing through the switching device reaching a high current threshold, indicative of a fault current. For example, the opening of the switching device only uses such a control when the current is greater than 500 A (amperes).

[0039] In another example of use of the invention, the management method according to the invention comprises a step of opening the switching element, the latter being traversed by zero current, the opening step comprising the substeps of: - blocking of the field-effect transistor by applying a blocking voltage between said one of the gate connection terminals and that of the first or second electrode used as the source of the field-effect transistor, - MOSFET transistor blocking - cutting off the power supply to a control circuit of the switching device.

[0040] During the blocking step, at least one blocking voltage is actually applied, since it is possibly applied to both grid connection terminals, i.e. between each of the grid connection terminals and their nearest electrode.

[0041] In this other example of opening the switching device, no control voltage is used when the current is zero or almost zero. zero, that is to say less than 100 mA.

[0042] Finally, in yet another example of use of the invention, the pre-charge step is followed by a high-voltage battery charging step via a charging terminal. In this case, the charging step is preceded by a step in which a near-zero voltage is applied between the other gate connection terminal and that of the first or second electrode used as the source of the field-effect transistor, this electrode being different between these two steps, when such a voltage was not already applied during the preceding pre-charge step. Indeed, when only a control voltage is used, the direction of current flow must be taken into account.

[0043] In this other example of use of the invention, the capacity pre-charged during the pre-charge stage is an input capacity of the charging terminal, the high voltage network then being made up of high voltage electrical links allowing the charging terminal to be connected to the high voltage battery.

[0044] When the pre-charge stage is followed by a stage of energy consumption by the high-voltage network, the two control voltages of the gate connection terminals of the field-effect transistor of the switching device are almost zero, to allow the battery to be recharged during the regenerative driving phases of the vehicle.

[0045] Finally, the invention relates to a vehicle comprising a high-voltage battery and a high-voltage network, each terminal of the high-voltage battery being connected to the high-voltage network via a disconnect device according to the invention. In this vehicle, preferably, two disconnect devices connect the high-voltage battery to the high-voltage network, this connection between the high-voltage battery and the high-voltage network being made without contactors or fuses.

[0046] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given by reference to the accompanying schematic drawings on the other hand, in which:

[0047] [Fig. 1] already described in relation to the prior art, represents a high-voltage battery of a vehicle connected to a high-voltage network of the vehicle via contactors,

[0048] [Fig.2] represents a field-effect transistor according to the invention, in a mode of realization of the invention,

[0049] [Fig. 3] represents a switching device according to the invention, in one embodiment of the invention, as well as a control circuit for this switching device,

[0050] [Fig. 4] represents a high-voltage battery of a vehicle, connected to a network high voltage of the vehicle via switching devices according to the invention, in one embodiment of the invention,

[0051] [Fig.5] represents steps in a process for managing the energy supply in the high-voltage network of [Fig.4], in one embodiment of the invention,

[0052] [Fig. 6] represents the evolution of a control voltage of a field-effect transistor of a switching device shown in [Fig. 4], as well as the evolution of the current in the high-voltage battery shown in [Fig. 4], and the evolution of the voltage across the terminals of the high-voltage network shown in [Fig. 4], during a pre-charge step of the management process of [Fig. 5], and

[0053] [Fig.7] represents an opening step under current when a fault current appears, implemented by the management process of the [Fig.5].

[0054] According to an embodiment of the invention shown in [Fig. 2], a junction field-effect transistor 100 with a lateral structure according to the invention comprises: - a first support layer 10 made of P-type silicon carbide (SiC), heavily doped with boron (which is reflected by the notation "P+" [Fig.2]) for example by ion implantation, - a second P-type semiconductor layer 12 made of silicon carbide but less heavily doped with boron (which is reflected by the notation "P-" [Fig.2]), formed by epitaxy above the first support layer 10, - a third N-type semiconductor layer 14 made of silicon carbide, also formed by epitaxy above the second support layer 12, - a first zone 16 and a second zone 18 of type N in silicon carbide, heavily doped for example with phosphorus (which is reflected by the notation "N+" [Fig.2]) and produced for example by photolithography then implantation and diffusion on the third semiconductor layer 14, these first and second zones being produced each at a distinct end of the semiconductor layer 14, or close to these ends, - a third zone 20 and a fourth zone 22 of type P in silicon carbide, heavily doped for example in boron and produced for example by photolithography then implantation and diffusion on the third semiconductor layer 14, the third zone 20 being proximal to the first zone 16 with respect to the second zone 18, and the fourth zone 22 being proximal to the second zone 18 with respect to the first zone 16, - a first metallic electrode in contact with the first zone 16, - a second metallic electrode e2 in contact with the second zone 18, - a first connection terminal for a metal grid in contact with the third zone 20, - a second metal g2 grid connection terminal in contact with the fourth zone 22, and - an insulating layer 15, for example of silicon dioxide (SiO2) covering the free surface of the third conductive layer 14 and insulating between them the electrodes el, e2 and the gate connection terminals gl, g2.

[0055] The first, second, third, and fourth zones 16, 18, 20, 22 each extend, optionally, onto the surface of the third conductive layer 14 beyond the limits of the electrode or the grid connection terminal partially covering it, in which case these zones are covered, on this surface, by the insulating layer 15 where they are not covered by an electrode or a grid connection terminal. Of course, the first, second, third, and fourth zones 16, 18, 20, 22 do not touch each other.

[0056] The distance between the first gate connection terminal g1 and the second gate connection terminal g2 is, for example, between 15 and 20 pm (micrometers) for a field-effect transistor 100 withstanding up to 1200V. Furthermore, for such a field-effect transistor 100, the distance between the first gate connection terminal g1 and the first electrode e1, as well as the distance between the second gate connection terminal g2 and the second electrode e2, are on the order of 1 pm. Finally, the thickness of the epitaxial layers is, for example, 4 to 6 pm for such a field-effect transistor 100.

[0057] The field-effect transistor 100 therefore has an N-channel formed by the third conductive layer 14. The first electrode e1 can be used as either a drain or a source. When used as a drain, then the second electrode e2 is used as a source, and the second gate connection terminal g2 allows the field-effect transistor 100 to be turned on by applying a control voltage Vg2 (referenced in [Fig. 3]) of approximately -15V between the second gate connection terminal g2 and this second electrode e2, i.e., by setting the second electrode e2 to a potential 15V higher than the second gate connection terminal g2.

[0058] When, on the contrary, the first electrode el is used as a source, then the second electrode e2 is used as a drain and the first gate connection terminal gl allows the field-effect transistor 100 to be opened by applying a control voltage Vgl (referenced [Fig.3]) of about -15V between the first gate connection terminal g1 and the first electrode el, that is to say by putting the first electrode el at a potential 15V higher than the first gate connection terminal gl.

[0059] Of course, many embodiments are possible, for example, in one alternative the field-effect transistor according to the invention is a P-type channel, in which case the types of the different layers must be reversed. Also, other types of dopants than boron or phosphorus are of course usable, and manufacturing variations are usable, for example, the formation of the second semi-con- layer ductrice 12 uses a diffusion furnace or ion implantation.

[0060] Figure 3 now illustrates how the field-effect transistor 100 is connected in a switching element 200 according to the invention. In order to make the switching element 200 open in the absence of a control voltage, an enhancement-mode MOSFET 110, of type N in this embodiment of the invention, is connected in series with the field-effect transistor 100 in a cascode configuration.

[0061] A first terminal of the switching member 200 is the first electrode e1 of the field-effect transistor 100. The drain of the MOSFET transistor 110 is connected to the second electrode e2 of the field-effect transistor 100, and the source of the MOSFET transistor 110 has an electrode e3 forming a second terminal of the switching member 200.

[0062] The source of the MOSFET transistor 110 is connected to the second gate connection terminal g2 by a resistor or resistive connection Rg.

[0063] A control circuit 4 allows the following to be applied: - a first control voltage Vgl between the first grid connection gl and the first electrode el, - a second control voltage Vg2 between the second gate connection g2 and the second electrode e2, and

[0064] - a third control voltage Vg3 between the gate of the MOSFET transistor 110 and the source of the MOSFET transistor 110.

[0065] The control circuit 4 is capable of receiving a voltage measurement Vc made by a voltmeter 2 across the terminals of the switching element 200, i.e. between the electrodes el and e3. It is also capable of receiving a current measurement through the switching element 200.

[0066] When the MOSFET transistor 110 is blocked, the second control voltage Vg2 becomes negative due to the resistive connection between the second gate connection terminal g2 and the source of the MOSFET transistor 110, blocking the field-effect transistor 100 as soon as this second control voltage Vg2 becomes less than the blocking voltage of the field-effect transistor 100.

[0067] Of course, other connection variants are possible for forming the switching element 200; in particular, the MOSFET transistor can be connected by its drain or its source to the first electrode, depending on the role of the latter. Furthermore, when the MOSFET transistor is of a different type than the field-effect transistor (for example, P-type and N-type respectively), the connections are modified accordingly.

[0068] As shown in [Fig. 4], in an example of use of the invention, two switching elements 200 and 202 according to the invention are used in place of battery contactors in the high-voltage circuit of [Fig. 1]. The resistive connections Rg of these switching elements are not shown for the sake of simplicity in [Fig. 4].

[0069] In particular, the switching member 200 is connected by the first electrode el corresponding to its first terminal to a positive terminal of the battery 30, and is connected by the electrode e3 corresponding to its second terminal, to a first terminal of the high voltage network 300.

[0070] The switching element 202 is identical to the switching element 200, in particular it comprises a field-effect transistor 102 identical to the field-effect transistor 100 and connected in series with an enhancement-mode MOSFET 112 identical to the MOSFET 110. The electrodes and connection terminals of the field-effect transistor 102 and the MOSFET 112 are therefore referenced in the same way as the electrodes and connection terminals of the field-effect transistor 100 and the MOSFET 110.

[0071] The electrode e3 of the source of the MOSFET transistor 112 is connected to a negative terminal of the battery 30, and the first electrode el of the field-effect transistor 102 is connected to a second terminal of the high-voltage network, separate from the first terminal of the high-voltage network.

[0072] Thus the potential at the level of the first electrode el of the field-effect transistor 100,102 is always greater than the potential at the level of the source of the MOSFET transistor 110, 112 when the battery is connected to energy consumers, which ensures a natural blocking of the MOSFETs 110, 112 when they are not powered.

[0073] The high-voltage network 300 comprises a capacitor 28 connected between its first and second terminals, an inverter connected in parallel with the capacitor 28, and a three-phase electric motor connected to the output of the inverter. The voltage across the terminals of the high-voltage network 300 is denoted VHt, and the voltage across the terminals of the high-voltage battery 30 is denoted VBatt-

[0074] A management method 400 according to the invention, for supplying energy to the high-voltage network 300 from the battery 30, is now described in relation to [Fig. 5]. The management method 400 is, for example, implemented in software in a main computer of the vehicle equipped with the battery 30, the switching devices 200, 202, and the high-voltage network 300. This computer is connected via a CAN (Controller Area Network) bus to the analog control circuit 4.

[0075] Prior to the implementation of the management method 400, the vehicle is in a standby state 402, i.e., asleep, a vehicle user having parked the vehicle and locked the doors. In this state 402, the control circuit 4 is not powered and the switching elements 200, 202 are open, in particular because a zero voltage is naturally established between the gate and the source of each of the MOSFET transistors 110, 112 in the absence of a control voltage between this gate and this source. As a result, a negative voltage appears between the gate connection terminal g2 and the second electrode e2 of each of the effect transistors. fields 100 and 102, which has the effect of blocking them. This is the cascode effect.

[0076] When the vehicle exits sleep mode, the control circuit 4 is powered and the vehicle's main control unit activates the disconnect devices 200, 202 to allow for their rapid closure. This activation step 404 comprises the following substeps:

[0077] - blocking 4040 of each field-effect transistor 100, 102 by applying a blocking voltage of -15V between the second gate connection g2 of the field-effect transistor 100, 102 and its second electrode e2 which functions as a source of the field-effect transistor 100, 102, and by applying a blocking voltage of -15V between the first gate connection gl of the field-effect transistor 100, 102 and its first electrode el which functions as a drain of the field-effect transistor 100, 102,

[0078] - switching on 4042 of MOSFET transistors 110, 112 by applying a a positive voltage of approximately 15V between the grid of each of them and the source of each of them, and

[0079] - waiting 4044 for a request to close the shut-off devices 200, 202.

[0080] Once the shut-off devices 200, 202 are activated, their closing or opening is de triggered solely by the control of the gate connection terminals gl and g2 of their respective field-effect transistors 100 and 102. The control voltages Vg2 and Vgl applied to close the field-effect transistors 100 and 102 are each approximately 0V, for example, between 0V and -IV, and the control voltages Vg2 and Vgl applied to open the field-effect transistors 100 and 102 are each approximately -15V, for example, between -10V and -20V. The MOSFET transistors 110 and 112 serve only to keep the vehicle's high-voltage circuit open when the control circuit 4 is not powered.

[0081] In summary, each field-effect transistor 100, 102 is:

[0082] - equivalent to an open circuit when its control voltages Vgl and Vg2 are equal to the blocking voltage of the field-effect transistor 100, 102,

[0083] - equivalent to a closed circuit when its control voltages Vgl and Vg2 are virtually none

[0084] - equivalent to a conducting diode in the direction of the second electrode e2 to the first electrode el when the control voltage Vgl is almost zero while the control voltage Vg2 is equal to the blocking voltage of the field-effect transistor 100, 102, and

[0085] - equivalent to a conducting diode in the direction of the first electrode el to the second electrode e2 when the control voltage Vg2 is almost zero while the control voltage Vgl is equal to the blocking voltage of the field-effect transistor 100, 102.

[0086] Although in this embodiment of the management method 400 according to the invention, the operating mode of the field-effect transistors 100, 102 corresponding to diodes is not used, such use is conceivable as an alternative embodiment.

[0087] When the vehicle's main computer receives a request to close the switching devices 200, 202, for example following a request to start the vehicle's electric motor, it implements a pre-charge step 406 of the capacity 28.

[0088] The pre-charge step 406 includes a first sub-step of sending current pulses 4060 to the high-voltage network 300, achieved by successive closings 24 and openings of the switching elements 200, 202, as shown in [Fig. 6]. Alternatively, one of the switching elements 200, 202 can be kept closed while the other switching element 202, 200 performs the successive closings 24 and openings. In this case, the switching element generating the current pulses alternates with the other switching element, for example, at each different pre-charge step 406 or within the same pre-charge step 406 to symmetrical their wear and / or limit their heating.

[0089] Each opening following a closing 24 is triggered as soon as a high threshold IMax of the current Ibatt through the battery is reached, this high threshold IMax being for example set at 200 A, and being preferably between 50 and 500 A.

[0090] The duration of successive closures 24 is a few hundred microseconds each and increases as the voltage VHt across the high-voltage network 300 increases, because the time t it takes for the current Ibatt to reach the upper threshold IMax also increases, the voltage Vc across the switching device 200 being (VBatt - VHt). Each closure 24 is triggered by a steep voltage rise Vg2, Vgl from -15V to 0V, while each opening following a closure 24 is controlled to limit the overvoltage on the switching device 200, 202.

[0091] These successive closures 24 and openings allow the capacitance 28 to be progressively charged, thus progressively increasing the voltage VHt at the terminals of the high voltage network 300.

[0092] When the voltage VHt across the terminals of the high-voltage network 300 reaches a high voltage threshold, set for example at 70% of the voltage VBatt of the battery 30, the vehicle's main computer implements, in this pre-charge step 406, a second sub-step of limiting the current 4062 through the switching devices 200, 202. In this sub-step of limiting the current 4062, a progressive (continuous) increase 26 of the control voltages Vg2, Vgl brings them up from approximately -15V to approximately 0V.

[0093] Alternatively, the pre-charge step 406 is carried out solely by a command to progressively increase the voltages Vg2, Vgl up to a value close to 0V, or solely by sending current pulses of increasingly longer durations.

[0094] Once the voltage VHt across the terminals of the high voltage network 300 reaches almost the voltage VBatt across the terminals of the high voltage battery 30, the control voltages Vgl, Vg2 are maintained at the value close to zero and the high voltage battery 30 operates in discharge during a stage 410 of supplying the vehicle's high voltage equipment.

[0095] Alternatively, when the high-voltage battery 30 is connected via the switching members 200, 202 to a charging terminal, the pre-charge step 406 having served to charge an input capacity of the charging terminal, then the management method 400 implements a charging step 408 of the high-voltage battery 30.

[0096] Once the charging step 408 or the supplying 410 of the high-voltage network is completed, the vehicle's main computer commands the opening of the switching devices 200, 202. We consider, as an example, the case where a discharge 410 has just ended.

[0097] During a step 414 immediately following this opening command, if the current flowing through the switching elements 200, 202 is zero or almost zero (branch Y of test 412 in [Fig. 5]), the vehicle being, for example, stopped and no high-voltage equipment of the vehicle running, then the opening step 414 of the switching elements 200, 202 comprises the sub-steps of:

[0098] - blocking 4140 of field-effect transistors 100, 102 by application of voltages control voltages Vg2, Vgl of -15V between the second gate connection terminal g2 and the second electrode e2 of each field-effect transistor 100, 102 and respectively between the first gate connection terminal gl and the first electrode el of each field-effect transistor 100, 102, then

[0099] - blocking 4142 of MOSFET transistors 110, 112 by applying a zero voltage between their respective grids and sources, then

[0100] - 4144 interruption of the power supply to control circuit 4.

[0101] The vehicle can thus return to standby mode, with minimal energy consumption by the vehicle's 14V on-board network to allow in particular a subsequent wake-up of the main computer.

[0102] In an application of the invention where a fault appears in the high-voltage network 300 or in the high-voltage battery 30 (branch N of test 412 on [Fig.5]), generating an abnormally high current, the vehicle's main computer implements a step 416 of opening the current-cutting devices 200, 202.

[0103] The opening step 416 includes a first substep 4160 for limiting the fault current, shown in [Fig. 7]. When the fault current reaches an ISM threshold high, for example 500A, the current passing through the breaking elements 200, 202 (equal to the current Ibatt passing through the high voltage battery 30) is limited so as to limit the energy to be dissipated during the opening which will follow, as well as the thermal stress of the cables and connectors which undergo the fault current.

[0104] To achieve this current limitation 4160, the gate control voltage Vg2 of each field-effect transistor 100, 102 and the gate control voltage Vgl of each field-effect transistor 100, 102 are reduced until a low current threshold Isc is reached, at which point the field-effect transistors 100, 102 are blocked in a second sub-step 4162. The low current threshold Isc is, for example, 100 mA. Indeed, it is the current variation dlc / dt that creates overvoltage on the field-effect transistor 100, 102, which must be limited by the gate controls. This limitation can be achieved until the current le is completely eliminated.

[0105] The reduction of the gate control voltages Vg2, Vgl of the field-effect transistors 100, 102 allowing the current Ibatt to reach a low threshold ISc of current, results from a control of these gate control voltages Vg2, Vgl as a function of the voltage Vc measured across the terminals of the switching element 200, that is to say that the gate control voltages Vg2, Vgl are adjusted so that the voltage Vc measured across the terminals of the switching element does not exceed a critical voltage withstand threshold of the field-effect transistors 100, 102, reduced by a safety margin for example of about twenty volts.

[0106] Alternatively, the gate control voltages Vg2 and Vgl are controlled based on the measured current flowing through the switching element 200, and more specifically based on the time variation dlc / dt of this current. Thus, the gate control voltages Vg2 and Vgl are adjusted so that this variation does not exceed a predetermined maximum current variation threshold.

[0107] In another variant, the gate control voltages Vg2, Vgl are controlled both according to the measurement of the current through the switching element 200 and according to the voltage Vc measured across the terminals of the switching element 200, so that neither the critical voltage withstand threshold of the field-effect transistors 100, 102, less the safety margin, nor the predetermined maximum current variation threshold, are reached.

[0108] Once the lower current threshold Isc is reached, the switching devices are opened by:

[0109] - the second substep 4162 of blocking field-effect transistors 100, 102, by applying control voltages Vg2, Vgl of -15V between the second gate connection terminal g2 and the second electrode e2 of each field-effect transistor 100, 102 and respectively between the first gate connection terminal gl and the first electrode el of each field-effect transistor 100, 102, followed

[0110] - by a third blocking substep 4164 of MOSFET transistors 110, 112 by application of a zero voltage between their respective grids and sources, followed

[0111] - by a fourth substep of switching off the circuit's power supply 4166 Order 4.

[0112] The current-opening step 416 is carried out in such a way as not to damage the switching elements 200, 202, and can therefore be repeated many times without needing to replace these switching elements 200, 202, which are preferably integrated into the battery pack to ensure that there is no voltage on the battery pack connectors. The invention thus makes it possible to save money compared to a conventional contactor system, which requires a dedicated pre-charge system, and makes it possible to preserve the cables and connectors of the vehicle's high-voltage network 300 thanks to the current-limiting function performed by the switching elements 200, 202.

[0113] Furthermore, although the switching elements 200, 202 require cooling, and the control circuit 4 requires a power supply, this power supply and cooling are possibly implemented by equipment integrated into the battery pack and not specific to the switching elements 200, 202. For example, the power supply of the power supply circuit 4 is shared with that of the vehicle's on-board network, while the cooling of the switching elements 200, 202 reuses, for example, a battery cell cooling system.

[0114] It should be noted that the invention is not limited to application in a motor vehicle, but may find other applications, particularly in any system comprising a high-voltage battery that must be disconnected from its consumers during shutdown or maintenance phases. For example, the disconnecting device according to the invention can be used in an energy storage system using a photovoltaic generator, and in various systems equipped with high-voltage batteries, such as construction equipment.

[0115] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of the different embodiments of the invention envisaged in this application can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

Demands

1. Switching element (200, 202) comprising a junction field-effect transistor (100, 102) with a side structure, comprising: - at least one support layer (10) of a first type of conductivity, - at least one semiconductor layer (14) of a second type of conductivity superimposed on the support layer (10) and capable of forming a channel between a source and a drain, - a first electrode (el) implanted on the semiconductor layer (14) and capable of forming the source or the drain, - a second electrode (e2) implanted on the semiconductor layer (14) and capable of forming the drain or the source, - a zone (20) doped according to the first type of conductivity in contact on the one hand with the semiconductor layer (14) and on the other hand with a gate connection terminal (gl) located between the first and second electrodes (el, e2) and electrically isolated from the first and second electrodes (el, e2), the field-effect transistor (100, 102) further comprising an additional region (22) doped according to the first type of conductivity, in contact on the one hand with the semiconductor layer (14) and on the other hand with another gate connection terminal (g2) located between the gate connection terminal (gl) and the second electrode (e2), and electrically isolated from the gate connection terminal (gl) and the second electrode (e2), the switching element (200, 202) being characterized in that it further comprises at least one enhancement MOSFET transistor (110, 112), connected in series with the field-effect transistor (100) in a cascode configuration.

2. A method (400) for managing the supply of energy in a high-voltage network (300) connected to a high-voltage battery (30) via at least one switching device (200) according to claim 1, the management method (400) being characterized in that it comprises an activation step (404) of the switching device (200) comprising substeps of: - blocking (4040) of the field-effect transistor (100) by applying a blocking voltage between one of the gate connection terminals (g2) and that of the first or second electrode (e2) used as the source of the field-effect transistor (100) - turning on (4042) of the MOSFET transistor (110), and - waiting (4044) for a request to close the switching element (200).

3. Method of managing (400) the supply of energy in a high voltage network (300) according to claim 2, comprising a pre-charge step of at least one capacitance (28) connected to the high voltage network (300), the pre-charge step comprising a limitation of the current (le) through the switching member (200) by a progressive variation of the voltage (Vg2) between said one of the gate connection terminals (g2) and that of the first or second electrode (e2) used as the source of the field-effect transistor (100).

4. Method of managing (400) the supply of energy in a high voltage network (300) according to claim 2, comprising a pre-charge step of at least one capacity (28) connected to the high voltage network (300), the pre-charge step comprising sending current pulses on the high voltage network (300), carried out by successive closings and openings of the switching device (200).

5. Method of managing (400) the supply of energy in a high voltage network (300) according to claim 2, comprising a pre-charge step (406) of at least one capacitor (28) connected to the high voltage network (300), the pre-charge step (406) comprising: - a sub-step of sending current pulses (4060) on the high voltage network, carried out by successive closings and openings of the switching member (200), followed - by a sub-step of limiting the current (4062) through the switching member (200) by a progressive variation of the voltage (Vg2) between said one of the gate connection terminals (g2) and that of the first or second electrode (e2) used as the source of the field-effect transistor (100).

6. A method (400) for managing the supply of energy in a high-voltage network (300) according to any one of claims 2 to 5, comprising an opening step (416) of the switching element (200) while it is carrying a non-zero current (le), the opening step (416) comprising controlling the voltage between said one of the gate connection terminals (g2) and that of the first or second electrode (e2) used as the source of the field-effect transistor (100) as a function of the voltage (Vc) across the switching element (200) and / or as a function of a variation in the current (the) passing through the cutting element (200) as a function of time (t).

7. Method of managing (400) the supply of energy in a high voltage network (300) according to any one of claims 2 to 5, comprising an opening step (414) of the switching element (200), the latter being traversed by a zero current (le), the opening step (414) comprising the substeps of: - blocking (4140) of the field-effect transistor (100) by application of a blocking voltage between said one of the gate connection terminals (g2) and that of the first or second electrode (e2) used as source of the field-effect transistor (100), - blocking (4142) of the MOSFET transistor (110), - cutting off (4144) a power supply to a control circuit (4) of the switching element (200).

8. Method of managing (400) the supply of energy in a high voltage network (300) according to any one of claims 3 to 5, wherein the pre-charge step (406) is followed by a charging step (408) of the high voltage battery (30) by a charging terminal.

9. Vehicle comprising a high-voltage battery (30) and a high-voltage network (300), each of the terminals of the high-voltage battery (30) being connected to the high-voltage network (300) via a switching device (200, 202) according to claim 1.

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