Battery disconnect device with transistors and liquid cooling

Abstract

Electric battery disconnect device with transistors and liquid cooling. The electric battery disconnect device comprises an input terminal (E) for connection to a terminal (201) of the battery, a current path (I) extending from the input terminal, and an output terminal (S) of the device for connection to a load (300). The current path comprises a first circuit (110) having at least two transistors (111, 112), each equipped with an internal diode and arranged in series with opposite conduction directions. The device further comprises a channel (400) through which a coolant can flow, the channel being configured so that the power dissipated by said at least two transistors is removed by the coolant. Figure for the abstract: Fig. 1.

Description

Title of the invention: Device for disconnecting an electric battery with transistors and liquid cooling technical field

[0001] The invention relates to devices for disconnecting an electric battery, for example the batteries of electric or hybrid vehicles used to supply electrical energy to a powertrain. Previous technique

[0002] Battery disconnect devices, known by the acronym "BDU" (for "Battery Disconnect Unit"), are systems that allow the battery to be connected and disconnected from the electrical network, particularly high-voltage networks. These devices protect electrical systems from overload, short-circuit, overvoltage, and overcurrent conditions, which can originate in the battery, an inverter, an electric motor, or auxiliary systems.

[0003] A good level of protection is necessary to avoid the risks of fire or electrocution for users.

[0004] In an electric or hybrid vehicle operating on a high-voltage battery, the battery disconnection device is a specific subsystem which can be integrated separately or distributed into several subsystems in the vehicle so that protection is obtained as close as possible to certain critical systems of the vehicle (inverter, battery, charger, etc.).

[0005] Solutions known according to the prior art may include a disconnection device integrated into a battery pack that primarily protects the inverter and a DC charger. Second devices may be provided in separate power distribution units (PDUs).

[0006] Other solutions according to the prior art may include protection located directly in the battery pack, and other protections distributed, for example in one or more power distribution units.

[0007] In a manner known per se, the battery disconnection and connection functions are implemented by electromechanical contactors, fuses, or pyrolytic fuses.

[0008] These components are indeed well suited for applications involving high power between the battery and power subsystems (inverter, charger). These components offer, given their possible dimensions and optimizations possible, satisfaction in terms of safety function, overload protection and short-circuit protection.

[0009] That being said, these components have drawbacks. Their long-term durability (on a scale of approximately 15 years) is questionable. These devices can be affected by false positives; they can trigger unnecessarily.

[0010] These devices are also impacted by false negatives; they may not trigger when necessary, for example.

[0011] Another drawback of these components is their resistance in the on-state, which generates heat dissipation detrimental to the robustness and reliability of the battery connection devices. Furthermore, the battery disconnect devices can be sensitive to excessively high temperatures (momentary or prolonged) and can therefore be affected by the components they contain.

[0012] Battery disconnect devices use two types of cooling for this purpose, by free convection (the disconnecting components and busbar dissipate into the air which is cooled), or by indirect cooling where the components and busbars are interfaced with a cold plate via a thermal interface material, for example electrically insulating (usually designated by the Anglo-Saxon acronym "TIM: Thermal Interface Material").

[0013] There is therefore a need for battery disconnection devices which do not have the disadvantages mentioned above. Description of the invention

[0014] To this end, the invention proposes a device for disconnecting (and connecting after disconnection) an electric battery, comprising a terminal intended to be connected to a terminal of the battery, a current path extending from the input terminal, and an output terminal of the device intended to be connected to a load, the current path comprising a first circuit having at least two transistors each equipped with an internal diode and arranged in series (the input and output of the first circuit are on either side of the at least two transistors) and in two opposite directions of conduction, the device further comprising a channel in which a coolant can circulate, the channel being configured so that the power dissipated by said at least two transistors is evacuated by the coolant.

[0015] Thus, the invention proposes not to use contactors, fuses or pyrolytic fuses, but to use at least two transistors in the device, at least in one of the branches going from one of the terminals of the battery to the load.

[0016] Transistors are particularly advantageous in that they can reversibly switch from the conducting state to the blocking state, and vice versa (therefore, disconnection and reconnection are possible).

[0017] The inventors observed that power transistors can be used in place of electromechanical contactors, for example, because they perform the same function but with improved properties. In particular, semiconductor-based transistors have a response time on the order of a hundred microseconds, compared to a response time on the order of 30 milliseconds for a contactor. Furthermore, transistors offer advantages over contactors in terms of power loss, longevity, weight (60 g for a transistor versus approximately 200 g for an electromechanical relay), capacitance, vibration resistance, noise level, functionality, and efficiency.

[0018] Power transistors switch very quickly under a large load and can therefore ensure very good durability under very variable current and cutoff profiles with reproducible performance.

[0019] That said, the inventors of the present intervention have observed that the use of transistors results in greater heat dissipation. Losses can be three to five times higher, and therefore a special cooling system is preferable.

[0020] Here, it is proposed to use a cooling system employing a coolant, rather than air. The coolant can be, for example, of the glycol type.

[0021] Also, the two transistors are of the same type here (for example, if they are MOSFETs, they are both of the same conduction type N or P).

[0022] The arrangement of a transistor in a particular conduction direction is related to the structure of the transistor and the orientation of its internal diode. Here, the internal diodes of the two transistors are in opposite orientations, for example with the anode of the internal diode of one transistor connected to the anode of the internal diode of the other transistor, or the cathode of the internal diode of one transistor connected to the cathode of the internal diode of the other transistor.

[0023] Also, the direction of conduction of a transistor can be: - drain to source for N-type field-effect transistors (the anode of the internal diode being connected to the source), - source to drain for P-type field-effect transistors (the anode of the internal diode being connected to the drain).

[0024] Thus, said at least two transistors can be connected in series with the source of one connected to the source of the other, or the drain of one connected to the drain of the other for field-effect transistors, regardless of the type of the two transistors (P or N).

[0025] The first circuit is thus bidirectional.

[0026] For example, the load mentioned above that receives electrical energy from the battery (the "load" in English) can be a motor vehicle powertrain. The supply of electrical energy to the powertrain can be called the "discharge" in English.

[0027] According to a particular embodiment, the battery terminal is the positive terminal, and in which the device comprises a second circuit including at least one transistor arranged between an input terminal of the second circuit connected to a battery charging port, and an output terminal of the second circuit connected between the first circuit and the output terminal of the device (i.e. connected to the output terminal of the first circuit), said at least one transistor being provided with an internal diode and arranged in a direction of conduction from the input terminal of the second circuit to the output terminal of the second circuit (in other words, the anode of the internal diode of said at least one transistor is connected to the charging port).

[0028] The first circuit is located in the branch extending from a battery terminal to the load; the second circuit is dedicated to protection during charging and is arranged between a battery charging port and a point located between the device's output terminal and the first circuit. The battery charging port may be intended to be connected to a charger including a rectifier.

[0029] According to a particular embodiment, the second circuit comprises, in the same package, at least two transistors arranged on one or more separate chips, connected in parallel and arranged between the input terminal of the second circuit and the output terminal of the second circuit, said at least two transistors being arranged according to said direction of conduction going from the input terminal of the second circuit to the output terminal of the second circuit.

[0030] According to a particular embodiment, the channel is further configured so that the power dissipated by said at least one transistor of the second circuit (or all the transistors of the second circuit) is evacuated by the coolant (for example the same liquid as the transistors of the first circuit, for the same channel).

[0031] It has been observed that the power from the charger may also require liquid cooling if a transistor is used. The channel can then be configured to allow this cooling (for example, by covering the casing of a transistor in the second circuit).

[0032] According to a particular embodiment, the device includes a processor configured to independently control the control electrodes of the transistors of the first circuit and the second circuit (if a second circuit is present).

[0033] In this particular embodiment, the control electrodes of the transistors (gate or base) each have their own connection to the processor.

[0034] According to a particular embodiment, one or more of said transistors of the first circuit or of the second circuit is mounted in a pin-shaped finned housing, said pin-shaped fins extending into said channel.

[0035] A pin-shaped finned housing can be called by the Anglo-Saxon expression PINFIN, and allows good cooling of the transistor(s).

[0036] It can be noted that several transistors can be arranged in the same package, for example all the transistors of the first or second circuit.

[0037] According to a particular embodiment, at least one of said transistors of the first circuit or of the second circuit is mounted in a housing assembled on a metal plate by means of a layer of thermal interface material, the metal plate being in contact with the coolant in said channel.

[0038] This particular embodiment also allows for adequate cooling. It should be noted that one or more transistors can be arranged in the same package, for example, all the transistors of the first or second circuit. The metal plate is generally called a "cold plate." Several separate packages can be arranged on this plate.

[0039] According to a particular embodiment, at least one of said transistors of the first or second circuit is mounted in a housing assembled between two metal plates by means of two layers of thermal interface material, the two metal plates each being in contact with the coolant in said channel.

[0040] According to a particular embodiment, the device includes at least one current sensor arranged in series with a negative terminal of the battery, the current sensor having, once mounted in a system including the load and the battery, an accuracy less than or equal to plus or minus 2% and a bandwidth greater than 500kHz.

[0041] Such a current sensor can be made using a so-called "shunt" resistor.

[0042] According to a particular embodiment, the first circuit includes a damping circuit configured to allow conduction in both directions of conduction of the two transistors of the first circuit, connected in parallel to the two transistors of the first circuit.

[0043] The damping circuit can be referred to by the Anglo-Saxon term "snubber". This circuit allows current peaks to be dealt with.

[0044] According to a particular embodiment, the damping circuit of the first circuit comprises two branches connected together in parallel, each branch comprising, in series, a diode defining a direction of conduction specific to the branch, a resistor, and a capacitor.

[0045] In this particular embodiment, the diodes allow for one branch per direction of current conduction, to have a bidirectional damping circuit.

[0046] According to a particular embodiment, the second circuit includes a damping circuit configured to permit conduction in the direction of conduction from the input terminal of the second circuit to the output terminal of the second circuit, connected in parallel to said at least one transistor of the second circuit.

[0047] According to a particular embodiment, the damping circuit of the second circuit comprises, in series, a diode defining the direction of conduction of the damping circuit, a resistor, and a capacitor. Brief description of the drawings

[0048] [Fig-1] Fig. 1 is a schematic representation of a device according to a example.

[0049] [Fig.2] Fig.2 represents a transistor in a pin-shaped finned package.

[0050] [Fig.3] The [Fig.3] represents a transistor in a package mounted on a cold plate.

[0051] [Fig.4] Fig.4 represents a transistor in a package mounted between two plates.

[0052] [Fig. 5] Fig. 5 represents a damping circuit according to an example

[0053] [Fig.6] Fig.6 represents a damping circuit according to an example.

[0054] [Fig.7] Fig.7 shows yet another damping circuit according to an example. Description of the implementation methods

[0055] In [Fig.1], a system comprising a device 100 for disconnecting a battery 200 used for supplying electrical energy to a load 300 is shown.

[0056] The battery 200 can be an electric or hybrid vehicle battery used to supply electrical power to a powertrain (the load 300).

[0057] The load 300 can therefore be, for example, an electric or hybrid vehicle inverter used for the traction and / or propulsion of the vehicle.

[0058] The battery, 200, has a positive terminal 201 and a negative terminal 202. In the illustrated example, the disconnect device is connected to the positive terminal. However, the invention is not limited to a disconnect device connected to the positive terminal of the battery and can be adapted for connection to the negative terminal of the battery.

[0059] The device includes an input terminal E which is therefore connected to the positive terminal 201 of the battery, and, in a current path leading to the load 300, a first circuit 110 comprising two transistors 111. The current path which The current flowing from the input to the output of the device is marked I in the figure. In the figure, the two transistors 111 and 112 are N-type MOSFET field-effect transistors (the invention also applies to P-type transistors), and preferably silicon carbide transistors, which are advantageous for high-power applications.

[0060] Transistor 111 is connected in a first direction of conduction, and the second transistor 112 is connected in the opposite direction of conduction with the two transistors in series.

[0061] Thus, the two sources 111S and 112S of these transistors are connected together here (alternatively, and without being shown, the two drains 111D and 112D of these transistors are connected together). In the figure, the internal diodes of these transistors are shown, with their anodes connected together.

[0062] The two gates 11IG and 112G of these two transistors are controlled by a processor 130 of the device. It should be noted that the gate control of these transistors is implemented independently. As can be seen in the figure, each gate has a separate connection to the processor 130.

[0063] The device further comprises a second circuit, 120 including a transistor 121 (here of type N, although the other type of conduction is conceivable by adapting the circuit) whose drain is connected to the output terminal of the device and the source to a PRC charging port (for example for connection to a rectifier).

[0064] Transistor 121 is configured to carry current in the direction from the charging port PRC to the branch carrying current I. In particular, transistor 121, via its drain 121D, is connected between the output terminal S and the first circuit. The source 121S of this transistor is connected to the charging port PRC. The anode of the internal diode of transistor 121 is connected to the charging port.

[0065] The second circuit further comprises, in parallel with transistor 121, another transistor 121' arranged in the same direction of conduction, transistor 121' is optional, and is used for applications whose power requires the paralleling of several transistors.

[0066] In fact, transistors 121 and 121' can be transistors arranged in the same package, present on one or more separate semiconductor chips.

[0067] This is also the case for transistors 111 and 112 which may comprise one or more semiconductor chip(s) in one or more packages.

[0068] In fact, a transistor represented in the figure can be implemented by a plurality of individual transistors, formed on one or more semiconductor chips. It's worth noting that the number of chips per unit allows for fine-tuning the available power. Connecting multiple units in parallel allows for a coarser adjustment of the available power.

[0069] The first circuit allows the battery 200 to be electrically isolated from the load 300. For this purpose, the gates of the HlGetll2G transistors can be controlled by the processor 130, particularly when the processor 130 detects, using a sensor, a situation in which it is necessary to block the flow of current I. As an example, a current sensor comprising a resistor 140 in series with the battery, connected to terminal 202 of the battery, can be used to detect short circuits. A voltage sensor 141 is connected across the terminals of resistor 140, and this voltage sensor 141 is connected to the processor 130. In fact, here, the resistor is a so-called shunt resistor. It should be noted that this allows for an accuracy of ±2% and a bandwidth greater than 500 kHz.

[0070] The use of a resistor allows for precise and rapid detection of a rise in current level, which should lead to a blocking of the transistors.

[0071] The invention is not limited to the use of a shunt resistor and covers other equally efficient sensors.

[0072] The second circuit 120 is useful for protecting the rest of the circuit from a problem with the battery charger.

[0073] The transistors in the first circuit may require special cooling. This may also be the case for the transistors in the second circuit. We will now describe the possible cooling methods.

[0074] Figure 2 is a cross-sectional view of transistor 111, and more specifically a cross-sectional view of the package 11 IB in which the transistor 111 chip is located. The package 11 IB is of the PINFIN type, with fins extending directly into a channel 400 through which a coolant flows. It can be noted that the package 11 IB can contain other semiconductor chips, for example, the chip(s) of transistor 112. Figure 3 is a cross-sectional view of a variant in which a package 11 IB' of transistor 111 is mounted on a metal plate 500 by means of a layer of thermal interface material (preferably electrically insulating). It can be noted that several packages can be assembled on the plate 500, which is in contact with the channel 400 through which a coolant flows.

[0075] Figure 4 is a cross-sectional view of another embodiment in which a housing 11 IB” of the transistor 111 is mounted between two metal plates 500” by means of a layer of thermal interface material (preferably electrically insulating). The two metal plates 500” are in contact with the coolant of the channel 400.

[0076] It can be noted that the 11 IB housing of [Fig.2] is the most suitable for high power, followed by the 111B housing, then the 111B housing”.

[0077] Figure 5 shows a damping circuit mounted on transistor 121 of the second circuit. More precisely, the damping circuit 125 is connected in parallel to the source and drain of transistor 121. It has one branch and is configured to allow conduction in the direction from the transistor's drain to its source. This branch includes a diode 126 whose anode is connected to the source of transistor 121, a resistor 127, and a capacitor 128 whose terminal is connected to the drain of transistor 121.

[0078] Figure 6 shows a damping circuit connected in parallel to the two transistors 111 and 112 of the first circuit. More specifically, the damping circuit has two branches, each associated with a direction of conduction. A first branch, 115A, has a diode 116A in series with a resistor 117A and a capacitor 118A. The anode of diode 116A is connected to the drain of transistor 111, and capacitor 118A has one terminal connected to the drain of transistor 112. A second branch, 115B, has a diode 116B in series with a resistor 117B and a capacitor 118B. The anode of diode 116B is connected to the drain of transistor 112, and capacitor 118B has one terminal connected to the drain of transistor 111.

[0079] Fig. 7 shows an alternative to the damping circuit of Fig. 6.

[0080] Here, the damping circuit has two branches, each associated with a direction of conduction. A first branch 115A has a diode 116A in series with a resistor 117A and a capacitor 118A. Here, the cathode of diode 116A is connected to the drain of transistor 112, and capacitor 118A has one terminal connected to the drain of transistor 111. A second branch 115B has a diode 116B in series with a resistor 117B and a capacitor 118B. The cathode of diode 116B is connected to the drain of transistor 111, and capacitor 118B has one terminal connected to the drain of transistor 112.

[0081] In addition, a resistor 119A connects branch 115A to ground and a resistor 119B connects branch 115B to ground. This alternative has the advantage of improving the switch-off response time. It should be noted that in one variant, resistors 119A and 119B can each be replaced by a varistor (which is less expensive than power resistors).

Claims

Demands

1. Device for disconnecting an electric battery, comprising an input terminal (E) for connection to a terminal (201) of the battery, a current path (I) extending from the input terminal, and an output terminal (S) of the device for connection to a load (300), the current path comprising a first circuit (110) having at least two transistors (111, 112) each having an internal diode and arranged in series and in two opposite directions of conduction, the device further comprising a channel (400) in which a coolant can flow, the channel being configured so that the power dissipated by said at least two transistors is evacuated by the coolant.

2. Device according to claim 1, wherein the battery terminal is the positive terminal (201), and wherein the device comprises a second circuit (120) comprising at least one transistor arranged between an input terminal of the second circuit connected to a battery charging port, and an output terminal of the second circuit connected between the first circuit and the output terminal of the device, said at least one transistor being provided with an internal diode and arranged in a direction of conduction from the input terminal of the second circuit to the output terminal of the second circuit.

3. Device according to claim 2, wherein the second circuit comprises, in the same package, at least two transistors arranged on one or more separate chips, connected in parallel and arranged between the input terminal of the second circuit and the output terminal of the second circuit, said at least two transistors being arranged in said direction of conduction from the input terminal of the second circuit to the output terminal of the second circuit.

4. Device according to claim 2 or 3, wherein the channel is further configured so that the power dissipated by said at least one transistor of the second circuit is evacuated by the coolant.

5. A device according to any one of claims 1 to 4, comprising a processor (130) configured to control independently the control electrodes of the transistors of the first circuit and the second circuit.

6. Device according to any one of claims 1 to 4, wherein one or more of said transistors of the first circuit or of the second circuit is mounted in a pin-shaped finned housing (11 IB), said pin-shaped fins extending into said channel.

7. Device according to any one of claims 1 to 6, wherein at least one of said transistors of the first circuit or of the second circuit is mounted in a housing (11 IB') assembled on a metal plate by means of a layer of thermal interface material, the metal plate being in contact with the coolant in said channel.

8. Device according to any one of claims 1 to 7, wherein at least one of said transistors of the first or second circuit is mounted in a housing (11 IB”) assembled between two metal plates by means of two layers of thermal interface material, the two metal plates each being in contact with the coolant in said channel.

9. Device according to any one of claims 1 to 5, comprising a current sensor (140, 141) arranged in series with another terminal of the battery, configured to have in use with the battery and load an accuracy less than or equal to plus or minus 2% and a bandwidth greater than 500kHz.

10. Device according to any one of claims 1 to 9, wherein the first circuit comprises a damping circuit (115) configured to permit conduction in both directions of conduction of the two transistors of the first circuit, connected in parallel to the two transistors of the first circuit.

11. Device according to claim 10, wherein the damping circuit of the first circuit comprises two branches connected together in parallel, each branch comprising, in series, a diode (116A, 116B) defining a direction of conduction specific to the branch, a resistor (117A, 117B) and a capacitor (118A, 118B).

12. A device according to any one of claims 1 to 11, wherein the second circuit comprises a damping circuit (125) configured to permit conduction in the direction of

13. conduction going from the input terminal of the second circuit to the output terminal of the second circuit, connected in parallel to at least one transistor of the second circuit. Device according to claim 12, wherein the damping circuit of the second circuit comprises, in series, a diode (126) defining the direction of conduction of the damping circuit, a resistor (127) and a capacitor (128).

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