FR2977739A1 - Electrical device for supply system of three-phase electric machine used to drive e.g. hybrid car, has supply circuit including transmission unit for transmitting data signal from low voltage circuit to high voltage circuit - Google Patents

Abstract

The device has a low voltage circuit (16) provided with a microcontroller (14) whose reference mass is on a low voltage battery (18). A high voltage circuit (8) is provided with a bridge (6) whose reference mass is on a high voltage battery (10). A galvanic insulation (20) is between the two circuits. A supply circuit (24) supplies power from the low voltage circuit to the high voltage circuit. The supply circuit includes a transmission unit for transmitting a data signal from the high voltage circuit to the low voltage circuit.

Description

Ref. Valeo CFR0458 1 Electrical device and corresponding power system The present invention relates to an electrical device. It also relates to a power system of an electric machine for driving a vehicle comprising such a device. More particularly, the invention relates to the field of electric or hybrid vehicles. Such vehicles comprise an electric machine for driving the vehicle using an electrical device comprising: a first circuit, called a LV circuit, provided with first electronic components capable of being supplied with low voltage; and a second circuit, called an HV circuit, provided with second electronic components capable of being supplied with high voltage. For reasons of operational safety, a potential barrier must be maintained between these two circuits. However, it is sometimes necessary to pass signals and / or current between them. For example, a high-voltage rechargeable battery is provided to provide the high power supply of the electric machine and it is necessary to determine the battery charge level to know the range of the vehicle. It is known for this to accurately measure the voltage level provided by this battery by means of an analog digital conversion ADC (analogous to "Analog to Digital Conversion") and a microcontroller exploiting the information provided by the means of conversion. The microcontroller is at the level of the LV circuit and the measurement of the voltage of the battery and its conversion in digital form require the use of at least one low voltage component of the HT circuit. To ensure the transmission of digital data from the HV circuit to the LV circuit, it is known to use an opto-isolator or a pulse transformer or an integrated circuit of digital insulator type.

In order to supply the low voltage component of the HV circuit, it is known to provide an additional floating supply or a power supply Ref. Valeo CFR0458 2 additional obtained from the high-voltage power supply. Another solution would be to supply the low voltage component from the LV circuit. These various options result in a complex and unreliable electrical device, in particular by causing a multiplication of the means to be implemented to ensure the galvanic isolation between the circuits. The present invention aims to improve the situation. For this purpose, the invention relates first of all to an electrical device comprising: a first circuit, called a LV circuit, provided with first electronic components whose reference mass is on a first voltage source; - A second circuit, said HT circuit, provided with second electronic components whose reference mass is on a second voltage source; and a galvanic isolation between the LV circuit and the HV circuit. According to the invention, this device comprises a supply circuit of a component, said component BT, of the circuit HT from the circuit LV, said supply circuit comprising means for transmitting a data signal from the circuit HT to the LV circuit. For example, the first voltage source delivers a voltage lower than that of the second voltage source. In a particular example, the first voltage source is a low voltage and the second voltage source is a high voltage.

In the context of the present application, a low voltage designates a voltage lower than 60V and a high voltage designates a voltage greater than 60V. Through the use of a power supply circuit itself comprising means for transmitting an analog and / or digital data signal, from the HV circuit to the LV circuit, the present invention provides a solution for ensuring that both the power supply of the LV component of the HV circuit and the data transmission, while maintaining the galvanic isolation between the HV circuit and the LV circuit, this in a simplified way. Advantageously, the power supply circuit comprises a transformer whose primary is connected to the LV circuit and the secondary is connected to the HT circuit.

Unlike existing devices, a single transformer is sufficient for powering and transmitting the data signal. Preferably, the feed circuit comprises: Ref. Valeo CFR0458 3 - an oscillator connected between a first power supply and the primary of the transformer, delivering an alternating voltage to the primary; and - AC voltage rectifying means connected to the secondary of the transformer.

The first power supply is in particular the first source of voltage, for example the low voltage supply of the first components of the LV circuit. According to a preferred embodiment, the oscillator is a harmonic oscillator, in particular of the Colpitts type. It may include a Class A amplifier looped in response to generate oscillations.

Advantageously, the rectifying means comprise a diode bridge. Advantageously, the data signal transmission means comprise damping means of the oscillator according to a damping factor function of the data signal. The means for transmitting the data signal may also comprise: damping factor detecting means; and means for determining (44) the data signal from the detected damping factor. According to a preferred embodiment, the damping means comprise short-circuit means for rectifying means.

Advantageously, the data signal represents the voltage across a second power supply. This second power supply is in particular the second voltage source, for example the high voltage power supply of the second components of the HV circuit. Preferably, the second power supply is a battery and the data signal represents the charge level of the battery. The circuit HT comprises, for example, means for measuring the charge level of the battery delivering said data signal, the frequency of said signal being representative of said charge level and said HT circuit being configured so that said signal is supplied as input to damping means.

Advantageously, the device further comprises means for detecting an overvoltage applied to the second power supply.

Ref. Valeo CFR0458 4 According to an exemplary embodiment, said means for detecting an overvoltage are made capable of modifying the signal delivered by the means for measuring the charge level of the battery. Preferably, the measuring means are powered by said supply circuit. The invention also relates to a power supply system for an electric machine for driving a vehicle, in particular an electric or hybrid vehicle, comprising the device of the invention. Embodiments of the invention will now be described more specifically, but not limitatively, with reference to the accompanying drawings in which: - Figure 1 is a diagram showing a power system of an electric machine according to a mode embodiment of the invention; FIG. 2 is a diagram showing an electrical device of the system of FIG. 1, according to one embodiment of the invention; FIG. 3 is a detailed electrical diagram of a first exemplary embodiment of the device of FIG. 2; FIG. 4 and FIG. 5 are graphs illustrating the operation of the circuit of FIG. 3; FIG. 6 is a detailed electric diagram of an exemplary embodiment of the device according to the invention; and FIG. 7 is a graph illustrating the operation of the circuit of FIG. 6. FIG. 1 represents a power supply system 2 of an electric machine 4 driving an electric or hybrid motor vehicle. The electric machine 4 is a three-phase machine. The three phases of this machine 4 are connected to a three-phase high-voltage power bridge 6. The machine 4 and the bridge 6 are connected to a high-voltage circuit 8, called the HV circuit, supplied with high voltage from a high voltage battery 10, called HT battery. A high voltage here means a voltage greater than 60V, typically of the order of 300 to 400V.

Control means 12 connected to a microcontroller 14 control the operation of the power bridge 6.

Ref. Valeo CFR0458 5 The microcontroller 14 is connected to a low voltage circuit 16, called LV circuit, supplied with low voltage from a low voltage battery 18, called battery BT. A low voltage here means a voltage below 60V, typically between 12V and 14V.

The HT circuit 8 and the BT circuit 16 are separated by a galvanic isolation 20 forming a potential barrier between the two circuits. By way of example, the HT circuit 8 and the LV circuit 16 are printed on two opposite sides of a printed circuit board, called the PCB (according to the acronym "Printed Circuit Board"), the thickness of said card providing electrical insulation between the two circuits 8, 16. The HT circuit 8 also comprises means 22 for measuring the voltage supplied by the battery HT 10. These measuring means 22 are supplied with low voltage from the LV circuit. 16 According to the invention, the power supply circuit 24 also transmits a data signal representing the voltage measured by the measurement means 22 to the microcontroller 14. This signal makes it possible to deduce the charge level of the battery 10. This data signal is a binary signal coming from the measurement means 22. For example, the measurement means 22 consist of a frequency-voltage converter 26 (FIG. 2). By this is meant a converter delivering a rectangular signal having a variable frequency, a function of the voltage applied at the input. The value of the frequency of the data signal is here representative of the value of the voltage of the battery HT 10. The voltage-frequency converter has the advantage of delivering a signal that is insensitive to attacks, in particular of the electromagnetic interference type EMI, and of allow the transmission of the data signal through the potential barrier with a negligible error rate. For example, the error rate is less than or equal to 0.2%, or even zero. With reference to FIG. 2, the supply circuit 24 comprises a transformer 30 whose primary 32 is connected to the BT circuit 16 and the secondary 34 is connected to the HV circuit 8. The primary 32 and the secondary 34 provide the galvanic isolation 20. The supply circuit 24 also comprises a harmonic oscillator such as a Colpitts type oscillator 36 connected between the supply BT 18 and the primary Ref. Valeo CFR0458 6 32 of the transformer 30. This oscillator 36 outputs an AC voltage. At secondary 34, rectifying means 38 of the AC voltage are provided. The supply circuit 24 further comprises damping means 40 of the oscillator 36 according to a damping factor function of the data signal and detection means 42 of the damping factor. The damping means 40 are connected to the secondary 34 of the transformer 30 and the detection means 42 are connected to the primary 32 of the transformer 30. In a remarkable manner, the fact of causing a damping at the secondary 34, this damping being visible at the primary 32, allows to transmit the information without additional cost, by amplitude modulation. Determining means 44 determine the value of the data signal as a function of the damping factor detected by the detection means 42. A first example of an architecture of the supply circuit 24 is detailed with reference to FIGS. 3, 4 and 5. .

The Colpitts oscillator 36 comprises two capacitors C1, C3 in series and an inductance L1 parallel to the capacitors. The capacitor C1 and the inductance L1 are connected to the low voltage battery 18. The inductance L1 is here the inductance of the primary 32 of the transformer 30. The resonance frequency Fo of the oscillator is determined by the values of C1, C3 and L1 according to the relationship Fo = 1 27r Ll. Cl - C3 (Cl + C3) For example, a resonance frequency of about 10 MHz will be chosen. C1 is chosen about ten times larger than C3. By way of example, L1 is of the order of 1 pH. Its own parasitic capacity will be limited to low values, less than 20 pF. The choice of a resonance frequency of about 10Mhz advantageously allows to have small components for the oscillator 36. It is thus possible to wind the transformer 30 directly on the circuit board decay. There is thus a transformer without core. This avoids the use of an expensive patch transformer, and cumbersome because it would be very difficult to isolate because of isolation distances to be respected.

Ref. Valeo CFR0458 7 The potential barrier is defined, for example, by a transformer made using two spirals of conductive tracks provided on the printed circuit, the spiral defining the primary winding of the transformer being provided on one of the faces circuit and the spiral defining the secondary on the other side, the right of the first.

The oscillator 36 also comprises a bipolar transistor type NPN type Q1 mounted in polarization type "common base". The NPN transistor may be replaced by a transistor of another type such as a PNP bipolar transistor, a JFET transistor or a MOSFET transistor mounted in "common grid" type polarization, by adjusting the polarization parameters of this transistor in a suitable manner.

Oscillator 36 also comprises a resistor R4 connected to the collector of transistor Q1. In order to avoid the influence of the parasitic elements due in particular to the internal resistances of the components, the value of R4 is chosen to be greater than the sum of the internal resistances of the capacitors C1, C3 and of the inductance L1. For example, R4 is greater than 1 o. This resistor R4 then makes it possible to stabilize the quality factor of the circuit tuned to the collector of transistor Q1 in terms of supply, aging, temperature, etc. The oscillator 36 also comprises, connected to the base of the transistor Q1, a capacitor C6 and a resistor R15 connected in parallel. The capacitor C6 and the resistor R15 are here connected in parallel with a DC voltage V3 in series with a resistor R12. Capacitor C6 and resistor R15 are used here, by way of example, to bias transistor Q1. In addition, the oscillator 36 comprises a resistor R16, connected between the emitter of the transistor Q1 and the ground, and a resistor R9 connected between the emitter of the transistor Q1 and a midpoint situated between the capacitors C1 and C3. R9 is chosen much higher than an impedance of the capacitor C1. The voltage gain resulting from the oscillator 36 is about 80 and its open-loop gain is about 7. The oscillator 36 has an open loop gain of much greater than 1 while the phase shift between the oscillator 36 input and output is very low around the resonance frequency Fo, thus ensuring large amplitude oscillations. The AC voltage supplied by the oscillator 36 is rectified at the secondary by the rectifying means 38 which comprise a diode bridge D1, D5, D6, D7.

Ref. Valeo CFR0458 8 According to another embodiment not shown, the diode bridge may comprise two transistors, for example of the MOSFET type, replacing diodes D6 and D7. The damping means 40 allow the voltage delivered by the oscillator 36 to be damped by short-circuiting the diode bridge 38 or, more precisely, one of the branches of the bridge, by means of a MOSFET transistor M7. mounted between the corresponding branch and the mass. The short-circuit frequency of the diode bridge is directly related to the frequency delivered by the voltage-frequency converter 26, which itself depends on the voltage supplied by the battery HT 10. For this, the gate of the transistor M7 is connected to an output Vs of said frequency converter. The frequency-voltage converter 26 comprises a comparator 48, for example an operational amplifier, whose frequency of the output voltage Vs is an image of the voltage supplied by the battery HT 10 connected to the non-inverting input of the comparator 48 by the intermediate of a voltage divider comprising a resistor R10. A capacitor C7 is also connected between the non-inverting input of the comparator 48 and the ground. The comparator 48 is powered by a voltage V + corresponding to the voltage rectified by the diode bridge 38. The output Vs of the comparator 48 is connected to the gate of the transistor M7. Preferably, an RC circuit 50, comprising a resistor R2 and a capacitor C2 connected in parallel, is provided between the diode bridge 38 and the supply V + of the comparator 48. This RC circuit makes it possible to adapt the rectified voltage to the power consumed by the comparator 48. In particular, the resistor R2 is chosen to stabilize the consumption of the circuit and the capacitor C2 to filter the residual harmonics at the output of the diode bridge 38. The short-circuit by the damping means 40 (transistor M7) results in the primary 32 by a reduction of the amplitude of the oscillations. This reduction, comparable to an amplitude modulation, is detected by the detection means 42.

Ref. Valeo CFR0458 9 At the output of the detection means 42, a signal Vd representative of the damping factor of the oscillator 36 is obtained. The determination means 44 determine from this signal Vd an image of the frequency of the output signal of the voltage-frequency converter 26, that is to say the voltage at the terminals of the battery HT 10. Advantageously, the determining means 44 comprise a Schmidt trigger, not shown here, connected at the output of the detection means 42. The graphs of FIGS. 4 and 5 show the evolution of the voltage, at different points of the circuit of FIG. time. Curve 60 of FIG. 4 shows the evolution of the voltage at the terminals of capacitor C7, that is to say at the non-inverting input of comparator 48, as a function of time. This voltage has the form of a periodic signal comprising two distinct parts P1 and P2 respectively corresponding to the charge and the discharge of the capacitor C7. The frequency-voltage converter 26 is configured to allow the succession of these two parts, the period of which is the image of the voltage at the terminals of the HV battery 10. The capacitor C7 is charged through a resistor R10 connected between the battery HT 10 and the non-inverting input of the comparator 48. In addition, the capacitor C7 is discharged through a resistor R13. The time separating two successive cycles of charge-discharge thus determines the output frequency of the frequency-converter 26.

Curve 62 shows the evolution of the voltage at the inverting terminal of comparator 48 as a function of time. The curve 64 shows the evolution of the voltage Vs at the output of the comparator 48 as a function of time. The frequency converter 26 is configured so that the voltage Vs is periodic of the same period as the voltage across the capacitor C7. The voltage Vs is zero during the part P1 and has a peak during the part P2. Curve 66 shows the evolution of the voltage across the resistor R2 as a function of time. This voltage is equal to the supply voltage V + of the comparator 48, that is to say the voltage rectified by the diode bridge 38. This voltage is substantially continuous, except during the part P2 where it undergoes a slight fall . The circuit is configured so that the voltage drop across the capacitor Ref. Valeo CFR0458 10 C2 does not disturb the power supply of the voltage-frequency converter 26. The modulation depth of the amplitude of oscillation is typically greater than 80%. Curve 68 (FIG. 5) represents the envelope of the voltage at the collector of transistor Q1, that is, at primary 32. This envelope also has the same period as voltage Vs (curve 64) at the output of FIG. Comparator 48. The curve 70 shows the evolution of the voltage Vd at the output of the detection means 42. Thanks to the invention, this voltage is periodic of the same period as the period of the voltage Vs at the output of the comparator 48. therefore also the image of the voltage at the terminals of the battery HT 10.

A second example of an architecture of the supply circuit 24 is detailed with reference to FIGS. 6 and 7. The circuit of FIG. 6 differs from the circuit of FIG. 3 in particular by the addition of detection means 74 of an overvoltage 75 This is a surge 75 that would be added to the voltage of the battery HT 10. For example, it is desired to detect an overvoltage that would change the voltage of the battery HT 10 with a nominal value of 300 V at 410 V. The application of this overvoltage at the secondary 34 of the transformer 30 has the effect of damping the oscillator 36 abruptly. The detection means 74 comprise a comparator 80, for example an operational amplifier.

The voltage from the battery HT 10 is applied to the non-inverting input of the comparator 80, the reference voltage being applied to the inverting input of the comparator 80. The output voltage of the comparator 80 is applied to the gate of a M2 MOS transistor connected to the inverting input of the comparator 48. A resistor R19 is also provided for biasing the transistor M2. It replaces the resistor R2 of FIG. 3. The application of an overvoltage thus has the effect of activating the damping means 40 by closing the transistor M7. Curve 84 shows the evolution of the voltage Vd at the output of the detection means 42 as a function of time.

Curve 86 shows the evolution of the voltage at the non-inverting input of comparator 48 as a function of time.

Ref. Valeo CFR0458 11 The curve 88 shows the evolution of the output voltage of the comparator 80. This voltage is an image of the overvoltage 75 applied. This voltage is zero during a first part P3 and not zero during a second part P4. The operation of the circuit during the part P3 is identical to the operation described with reference to FIGS. 3, 4 and 5. It is observed in particular that the time during which the voltage Vd (curve 84) is very low (almost zero) corresponds to periods of time. about ten microseconds. Following the application of the overvoltage 75, the time during which Vd (curve 84) is very small increases significantly and thus becomes much greater than 10 ps. The calculation of this duration at the transformer primary and its comparison to the normal duration of about ten microseconds make it possible to detect the presence of a surge in the secondary. The invention thus provides a compact and inexpensive device for both supplying the means for measuring the voltage of the battery HT and transmitting the result of this measurement to the LV circuit. It will be noted in particular that only one potential barrier provided by the transformer 30 is necessary. This single potential barrier makes it possible, in a remarkable manner, to transmit more than one signal, in particular two signals, such as the voltage across the power supply 10 and an overvoltage signal.

Other embodiments are still conceivable. Thus, the voltage-frequency converter can be replaced by an analog-digital converter, the signal transmitted from the secondary to the primary is coded as digital data with a determined number of bits. This choice is advantageous in particular for the transmission of the measurement signal of a phase current of the motor or of diagnostic data, for example. In addition, the Colpitts oscillator can be replaced by another harmonic oscillator that can be cushioned at will, like a Hartley-type oscillator, for example.

Claims (16)

REVENDICATIONS1. An electrical device comprising: - a first circuit (16), said LV circuit, provided with first electronic components (14) whose reference mass is on a first voltage source (18); - A second circuit (8), said HT circuit, provided with second electronic components (6) whose reference mass is on a second voltage source (10); and a galvanic isolation (20) between the LV circuit (16) and the HV circuit (8), characterized in that it comprises a supply circuit (24) for a component (22), called a BT component, the HV circuit (8) from the LV circuit (16), said supply circuit (24) comprising means for transmitting a data signal from the HV circuit (8) to the LV circuit (16). 2. Device according to claim 1, wherein the power supply circuit (24) comprises a transformer (30) whose primary (32) is connected to the LV circuit (16) and the secondary (34) is connected to the HT circuit ( 8). 3. Device according to claim 2, wherein the power supply circuit (24) comprises: - an oscillator (36) connected between a first power supply (18) and the primary (32) of the transformer (30), delivering an alternating voltage primary school (32); and rectifying means (38) of the alternating voltage connected to the secondary (34) of the transformer (30). The device of claim 3, wherein the oscillator (36) is a harmonic oscillator. 5. Device according to claim 4, wherein the oscillator (36) is a Colpitts.Ref type oscillator. Valeo CFR0458 13 6. Device according to any one of claims 3 to 5, wherein the rectifying means (38) comprise a diode bridge. 7. Device according to any one of claims 3 to 6, wherein the data signal transmission means comprise damping means (40) of the oscillator (36) according to a damping factor function of the signal of data. 8. Device according to claim 7, wherein the means for transmitting the data signal comprise: - detection means (42) damping factor; and means for determining (44) the data signal from the detected damping factor. 9. Device according to claim 7 or 8, wherein the damping means (40) comprises short-circuit means rectifying means (38). Apparatus according to any one of the preceding claims, wherein the data signal represents the voltage across a second power supply (10). The apparatus of claim 10, wherein the second power supply (10) is a battery and the data signal represents the battery charge level. 12. Device according to claim 11, wherein the HT circuit (8) comprises means (26) for measuring the charge level of the battery (10) delivering said data signal, the frequency of said signal being representative of said charge level. and said HT circuit (8) being configured so that said signal is input to the damping means (40). 13. Device according to any one of claims 10 to 12, further comprising means (74) for detecting an overvoltage (75) applied to the second power supply (10). Ref. Valeo CFR0458 14 14. Device according to claims 12 and 13, wherein said means (74) for detecting an overvoltage are made to modify the signal delivered by the measuring means (26) of the charge level of the battery (10). 15. Device according to any one of claims 12 to 14, wherein the measuring means (26) are fed by said supply circuit (24). 16. A power supply system (2) for an electric machine (4) for driving a vehicle, in particular an electric or hybrid vehicle, comprising a device according to any one of claims 1 to 15.