System for converting a first voltage into a second voltage, comprising at least one passive voltage-limiting component

Abstract

The invention relates to a system (2) for converting a first voltage (U1) into a second voltage (U2) comprising a converter (4) provided with at least two input terminals (5), at least two output terminals (8), and at least one electronic switching branch (10), the or each branch (10) comprising two switching half-branches (16) connected in series to an intermediate terminal (8), at least one half-branch (16) comprising at least one switching member (19), the or each switching member (19) comprising a controllable electronic switch (20); and a device (6) for controlling the or each electronic switch (20) of the or each branch (10); the converter (4) further comprising, for the or each electronic switch (20), a passive voltage-limiting component (12) connected to the electronic switch (20), thermally coupled to the electronic switch (20), and having a negative thermal coefficient.

Description

[0001] SYSTEM FOR CONVERTING A FIRST ELECTRICAL VOLTAGE INTO A SECOND ELECTRICAL VOLTAGE COMPRISING AT LEAST ONE PASSIVE VOLTAGE LIMITER COMPONENT

[0002] DESCRIPTION

[0003]

[0001] The invention relates to a system for converting a first electrical voltage into a second electrical voltage, comprising a converter of a first electrical voltage into a second electrical voltage as well as a device for controlling the converter. The invention also relates to an electric charger for an electric or hybrid vehicle, comprising such an electrical conversion system, as well as to an electric or hybrid vehicle, in particular an automobile, comprising such an electric charger.

[0004]

[0002] Known in the state of the art are electric chargers for electric or hybrid vehicles, on board such a vehicle and intended to be connected to a terminal or an electric charging station for the vehicle's electrical power supply. The on-board charger can operate in an electric or hybrid vehicle in several operating modes, including:

[0005] - network to vehicle (or G2V for “grid to vehicle” in English);

[0006] - vehicle to grid (or V2G for “vehicle to grid” in English);

[0007] - vehicle to home (or V2H for “vehicle to home” in English);

[0008] - vehicle to load (or V2L for “vehicle to load” in English).

[0009]

[0003] In the vehicle-to-load (V2L) mode, the supply of an alternating electric current (typically 230 V single-phase) is typically achieved by taking electrical energy from the vehicle's high-voltage battery (battery with a nominal voltage of 400 V or 800 V) and converting the latter into alternating electric current (using a power conversion stage present in the charger). It is then possible to connect an external electrical device to the vehicle so as to power the device with the alternating electric current. The power conversion stage conventionally comprises a system for converting a first direct electric voltage into a second alternating electric voltage, the conversion system being provided with a converter as well as a converter control device.

[0010]

[0004] The converter of a first direct electrical voltage into a second alternating electrical voltage typically has a topology made up of three electronic switching branches (or arms). Each switching branch comprises two half-switching branches connected in series at an intermediate terminal. Each half-branch comprises one or more current switching members connected in parallel. Each switching member comprises an electronic switch of the transistor type, typically a metal-oxide gate field effect transistor (or MOSFET in English terminology, from "Metal Oxide Semiconductor Field Effect Transistor"). The control device is connected to each of the electronic switches to enable their control.

[0011]

[0005] However, due to the geometry of the converter (in particular the geometry of the printed circuit board of the latter, which allows the flow of electric currents from the control device to the switches), different current paths exist between the switches, which generates distinct parasitic inductance values ​​and causes distinct switching losses within each of the electronic switch chips. More precisely, for an electronic chip which has the longest current path, the parasitic inductance is higher, which results in a lower quantity of switched current and therefore more switching losses. This imbalance between switching losses is complemented by another imbalance concerning conduction losses, due to differences in electrical parameters between the chips.

[0012]

[0006] Such an imbalance between switching and conduction losses results in differences between the junction temperatures of the different chips, which is critical for the converter from the point of view of limiting the latter's performance (and therefore its ability to supply alternating electric current). Indeed, greater losses within the chip of a given electronic switch result in higher temperatures, and this temperature imbalance significantly degrades the electrical performance of the converter.

[0013]

[0007] There is therefore a need to be able to reduce the imbalance between the switching and conduction losses of the switching members of a system for converting a first electrical voltage into a second electrical voltage, in order to harmonize and regulate the junction temperatures between the chips of these switching members and thus improve the electrical performance of the system.

[0014]

[0008] To achieve this objective, the invention proposes, in its broadest sense, a system for converting a first electrical voltage into a second electrical voltage, comprising:

[0015] - a converter of a first electrical voltage into a second electrical voltage, the converter comprising at least two input terminals, at least two output terminals, and at least one electronic switching branch connected between the two input terminals, the or each branch comprising two switching half-branches connected in series at an intermediate terminal, at least one half-branch comprising at least one switching member, the or each switching member comprising a controllable electronic switch provided with a control electrode and two conduction electrodes;

[0016] - a control device for the or each electronic switch of the or each branch; in which the converter further comprises, for the or each electronic switch, a resistor and a passive voltage-limiting component, the resistor being connected between the control device and the control electrode of said electronic switch, said passive voltage-limiting component being connected between the control electrode and one of the conduction electrodes of said electronic switch, being thermally coupled to said electronic switch, and having a negative thermal coefficient.

[0017]

[0009] The presence in the converter of such a passive voltage-limiting component for the or each electronic switch makes it possible to balance the junction temperatures between the chips of the switching members and thus improve the electrical performance of the system. Indeed, by placing such a passive voltage-limiting component within the converter and by thermally coupling it to the associated electronic switch, the temperature of this component becomes very close to that of the chip of the electronic switch. Thus, when the chip of the switch is heated more than the other switch chips during operation of the converter, the passive voltage-limiting component associated with this switch has a lower breakdown voltage (due to the negative thermal coefficient of the component).However, for a transistor-type electronic switch having a control electrode and two conduction electrodes, the value of its internal resistance is proportional to the voltage applied to the control (voltage applied between the control electrode and one of the conduction electrodes). Consequently, when the chip of a switch is heated more than the other switch chips during operation of the converter, the value of the control voltage decreases and therefore the chip of the switch in question has a greater resistance, which leads to the switch having less electric current flowing within it (and therefore less conduction losses). This mechanism, enabled by the presence of the passive voltage-limiting component for the or each electronic switch, thus allows automatic regulation of the temperature between the chips of the switching devices.The resistance allows the voltage between the control electrode and one of the conduction electrodes of the electronic switch to be decoupled.

[0018]

[0010] According to a variant, the or each passive voltage-limiting component is a Zener diode.

[0019]

[0011] According to a variant, the Zener diode is arranged in the switching member comprising the electronic switch to which it is connected.

[0020]

[0012] According to a variant, the Zener diode is arranged in the converter in such a way that it is located at a distance from the chip of the electronic switch to which it is connected which is less than 0.5 cm, preferably of the order of 1 mm or 2 mm. This makes it possible to further improve the regulation of the junction temperatures between the chips of the switching members, and therefore to further improve the electrical performance of the system.

[0021]

[0013] According to a variant, the or each resistor has a resistance value between 1 Q and 10 Q.

[0022]

[0014] According to one variant, the or each electronic switch comprises a semiconductor electronic switching component, such as a transistor or a thyristor.

[0023]

[0015] According to a variant, said semiconductor electronic switching component is a metal-oxide gate field effect transistor, said passive voltage-limiting component being connected between the gate and the source of said metal-oxide gate field effect transistor.

[0024]

[0016] According to a variant, the Zener diode is such that its breakdown voltage is between 16 V and 22 V, for a temperature between 150°C and 200°C.

[0025]

[0017] This makes it possible to obtain a breakdown voltage for the Zener diode which is close to the nominal gate-source voltage of the corresponding metal-oxide gate field effect transistor (in its closed state), when the transistor chip is close to its maximum temperature (which is between 150°C and 200°C).

[0026]

[0018] The invention also relates to an electric charger for an electric or hybrid vehicle, the electric charger comprising a system for converting a first electrical voltage into a second electrical voltage as described above.

[0027]

[0019] The invention also relates to an electric or hybrid vehicle, in particular an automobile, comprising an electric charger as described above.

[0028]

[0020] Embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the single appended figure in which:

[0029] - [Fig.1] is a schematic representation of an electrical conversion system according to an embodiment of the present invention.

[0030]

[0021] With reference to Figure 1, a system 2 for converting a first electrical voltage U1 into a second electrical voltage U2 is illustrated, according to one embodiment of the invention. The electrical conversion system 2 is typically installed within an electric or hybrid motor vehicle, more precisely within an electric charger of the vehicle, and comprises a converter 4 of a first electrical voltage U1 into a second electrical voltage U2, and a device 6 for controlling the converter 4.

[0031]

[0022] The converter 4 is for example connected on the one hand to a high voltage battery 3 of an electric or hybrid vehicle, supplying to its two input terminals 5 (only one of which is shown in FIG. 1) the first electrical voltage U1, and on the other hand to a load 7 delivering between its output terminals 8 (only one of which is shown in FIG. 1) the second electrical voltage U2. In the exemplary embodiment shown in FIG. 1, the first electrical voltage U1 is a direct electrical voltage from the electric storage battery of the vehicle, after transformation by one or more other stage(s) of the electric charger, and the second electrical voltage U2 is an alternating electrical voltage, for example three-phase. According to this same example, the converter 4 comprises two input terminals 5 and three output terminals 8. Alternatively, the first electrical voltage U1 may be an alternating electrical voltage.Alternatively or additionally, the second electrical voltage U2 may be a direct electrical voltage.

[0032]

[0023] The converter 4 of a first electrical voltage U1 into a second electrical voltage U2 comprises at least one electronic switching branch 10 connected between its two input terminals 5. In the particular embodiment of FIG. 1, the converter 4 comprises three electronic switching branches 10. The converter 4 also comprises three passive voltage-limiting components 12, and three resistors 14. Each assembly consisting of an electronic switching branch 10, a passive voltage-limiting component 12 and a resistor 14 corresponds to a distinct phase of the alternating electrical voltage U2.

[0033]

[0024] Each electronic switching branch 10 comprises two half-switching branches 16 connected in series at an intermediate terminal 8. In Figure 1, only one half-branch 16 is shown for each switching branch 10, for reasons of clarity (the other half-branches 16 not shown should be imagined as mirror images of the half-branches 16 shown, and connected to the other input terminal - not visible in Figure 1 - of the converter 4). Each intermediate terminal 8 of an electronic switching branch 10 corresponds to an output terminal of the converter 4. The three intermediate terminals 8 appear to be connected to each other.

[0034]

[0025] Each switching half-branch 16 comprises a switching member 19. In a variant not shown, each switching half-branch 16 comprises a number N1 of switching members 19, N1 being an integer greater than or equal to two. In a further variant, only one switching half-branch 16 comprises a number N3 of switching members, N3 being an integer greater than or equal to one.

[0035]

[0026] As known per se, each switching member 19 is bidirectional in current and unidirectional in voltage. Each switching member 19 comprises a controllable electronic switch 20 having a control electrode 20A and two conduction electrodes 20B, 20C. Each switch 20 is for example formed from a metal-oxide gate field effect transistor, also called a MOSFET transistor (from the English “Metal Oxide Semiconductor Field Effect Transistor”). All the MOSFET transistors 20 are, for example, identical. The gate 20A of each MOSFET transistor 20 is connected to the control device 6 to receive a corresponding control signal.Alternatively, the MOSFET transistor 20 is replaced by any semiconductor electronic component comprising a control electrode and two conduction electrodes, such as a bipolar transistor, a field effect transistor, a thyristor, a gate-turn-off thyristor, an IGCT thyristor (from the English "Insulated Gate Commutated Thysistor"), or an MCT thyristor (from the English "MOS Controlled Thyristor") for example.

[0036]

[0027] Each passive voltage-limiting component 12 is thermally coupled to the chip of one of the MOSFET transistors 20, and is connected between the gate 20A and the source 20C of this transistor. Each passive voltage-limiting component 12 is typically a Zener diode, which has a breakdown voltage of between 16 V and 22 V, for a temperature of between 150°C and 200°C. Each passive voltage-limiting component 12 has a negative thermal coefficient. For example, when each passive voltage-limiting component 12 is a Zener diode, each Zener diode 12 has a breakdown voltage of 19 V for a temperature equal to 175°C, and a breakdown voltage of 17 V for a temperature equal to 200°C, without this being limiting within the scope of the present invention.

[0037]

[0028] Each Zener diode 12 is for example arranged in the switching member 19 which comprises the MOSFET transistor 20 to which it is connected. Each Zener diode 12 is typically arranged in the converter 4 in such a way that it is located at a distance from the chip of the MOSFET transistor 20 to which it is connected which is less than 0.5 cm, preferably of the order of 1 mm or 2 mm.

[0038]

[0029] Each resistor 14 is connected between the control device 6 and the gate 20A of a corresponding MOSFET transistor 20. Each resistor 14 has a resistance value for example between 1 Q and 10 Q.

[0030] The electrical conversion system 2 according to the invention makes it possible to reduce the imbalance between the switching and conduction losses of the switching members 19, in order to harmonize and regulate the junction temperatures between the chips of these switching members 19 and thus improve the electrical performance of the system 2.

Claims

CLAIMS 1. System (2) for converting a first electrical voltage (U1) into a second electrical voltage (U2), comprising: - a converter (4) of a first electrical voltage (U1) into a second electrical voltage (U2), the converter (4) comprising at least two input terminals (5), at least two output terminals (8), and at least one electronic switching branch (10) connected between the two input terminals (5), the or each branch (10) comprising two switching half-branches (16) connected in series at an intermediate terminal (8), at least one half-branch (16) comprising at least one switching member (19), the or each switching member (19) comprising a controllable electronic switch (20) provided with a control electrode (20A) and two conduction electrodes (20B, 20C); - a device (6) for controlling the or each electronic switch (20) of the or each branch (10); characterized in that the converter (4) further comprises, for the or each electronic switch (20), a resistor (14) and a passive voltage-limiting component (12), the resistor (14) being connected between the control device (6) and the control electrode (20A) of said electronic switch (20), said passive voltage-limiting component (12) being connected between the control electrode (20A) and one of the conduction electrodes (20C) of said electronic switch (20), being thermally coupled to said electronic switch (20), and having a negative thermal coefficient.

2. Electrical conversion system (2) according to claim 1, characterized in that the or each passive voltage limiting component (12) is a Zener diode.

3. Electrical conversion system (2) according to claim 2, characterized in that the Zener diode (12) is arranged in the switching member (19) comprising the electronic switch (20) to which it is connected.

4. Electrical conversion system (2) according to claim 2 or 3, characterized in that the Zener diode (12) is arranged in the converter (4) in such a way that it is located at a distance from the chip of the electronic switch (20) to which it is connected which is less than 0.5 cm, preferably of the order of 1 mm or 2 mm.

5. Electrical conversion system (2) according to any one of claims 1 to 4, characterized in that the or each resistor (14) has a resistance value between 1 Q and 10 Q.

6. Electrical conversion system (2) according to any one of claims 1 to 5, characterized in that the or each electronic switch (20) comprises a semiconductor electronic switching component, such as a transistor or a thyristor.

7. Electrical conversion system (2) according to claim 6, characterized in that said semiconductor electronic switching component (20) is a metal-oxide gate field effect transistor, said passive voltage limiting component (12) being connected between the gate (20A) and the source (20C) of said metal-oxide gate field effect transistor.

8. Electrical conversion system (2) according to claim 7 when it depends on claim 2, characterized in that the Zener diode (12) is such that its breakdown voltage is between 16 V and 22 V, for a temperature between 150°C and 200°C.

9. Electric charger for electric or hybrid vehicle, characterized in that it comprises a system (2) for converting a first electrical voltage (U1) into a second electrical voltage (U2) according to any one of claims 1 to 8.

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