FR3128597A1 - Electrical conversion system for vehicle battery - Google Patents

Abstract

The invention relates to an electrical conversion system intended to be connected to a battery (BATT), for example of an electric or hybrid vehicle, to convert the input voltage supplied by the battery into an auxiliary voltage (V_aux). The system comprises a conversion unit (2) provided with two electric converters (U1, U2), a first converter (U1) capable of being controlled to generate the auxiliary voltage (V_aux) and to supply a first electric power, and a second converter (U2) also capable of being controlled to generate said auxiliary voltage (V_aux) and to supply a second electric power having a higher value than that of the first electric power supplied by the first electric converter. An analog control circuit is used to activate the second electric converter (U2) when a power surplus is necessary, in particular when starting the vehicle. Figure to be published with abstract: Figure 1

Description

Electrical conversion system for vehicle battery

Technical field of the invention

The present invention relates to an electrical conversion system intended to be connected to the two terminals of a battery of an electric or hybrid vehicle.

State of the art

Traction of an electric or hybrid vehicle is made possible by the use of several batteries or electrical energy storage modules, brought together in a battery pack. Each module generally comprises several electrochemical cells. To supply the vehicle's on-board network, i.e. for example the headlights, the windows, the ABS when braking, the steering assistance, but also much more basic functions such as opening/ central locking by remote control, a standard 12V or 24V lead-acid battery is generally used, which is recharged by the battery pack via a DC/DC type converter. The presence of this additional lead battery is justified by the need to have a voltage of 12V even when the vehicle is not on and by the need to have an independent 12V source which does not discharge the traction battery. For safety reasons in particular, certain functions powered by the 12V voltage supplied by this battery must:

• Be available even in the event of a serious failure of the battery pack used to drive the vehicle (= no voltage at the terminals of the battery pack);
• Be available even in the event of a communication breakdown between the various control circuits of the battery pack;
• Do not empty the traction battery pack if the vehicle is stationary for a long time (weeks or months);
• Be available even when the vehicle is stationary (ignition off);

Recently, it has been proposed to do away with this additional lead-acid battery and to use the traction batteries directly to supply the on-board network. For each module of a battery pack, a converter is intended to convert the voltage of the module into a voltage of 12V available for supplying the on-board network. The converters associated with each module can be controlled according to the state of charge of their module, performing at the same time a balancing operation (the most charged modules will supply more current to the 12V on-board network). This solution is described in particular in the patent applicationsFR2972581A1 AndFR2982090A1.

However, if this architecture has the advantage of dispensing with the use of the additional lead-acid battery, it does not make it possible to meet all the operating constraints mentioned above.

In fact, when the vehicle is stationary (i.e. with the ignition off), the voltage measurement cards at the terminals of each module are not powered, so the voltage levels of the modules are no longer available, and the central control unit, responsible for sending control orders to the DC/DC converters of the modules, is also off, which means that the converters cannot be controlled appropriately.

There is therefore a need to propose a solution making it possible to guarantee supply to the on-board network, even when the vehicle is stationary, that is to say on standby, regardless of the duration of this stoppage.

The patent application FR3089072A1 proposes a solution to manage this problem, which consists in implementing a control sequence in which conversion units are activated in turn independently to maintain the voltage on the auxiliary network.

However, after analysis, it was found that there are at least two distinct vehicle standby states:

• A first long-term standby state: In this state, only the anti-theft device and the amplifier/demodulator of the vehicle door opening control signal remain powered. The power required is then extremely low (of the order of a few watts).
• A second standby state before starting: This state is encountered just before starting the vehicle. This involves, for example, powering the electromechanical system used to open the doors: the power required on the vehicle's auxiliary network is then higher, up to a peak of 50W.

These two sleep states do not require the same level of power. And there is therefore a need to take account of these different power levels in order to limit the consumption of the system. It is in fact unnecessary for a converter to be able to supply the power necessary for the second standby state while the vehicle is in a long-term standby state. This assumption derives from the observation that a converter capable of providing a certain nominal power, has a non-negligible consumption even if it is in the process of providing a power much lower than its nominal power, because among other things of the losses internal to the device itself. -even. The higher the nominal power of a converter, the higher its losses at low power and incompatible with long standby.

The object of the invention is to propose a solution making it possible to dispense with the use of the lead-acid battery for supplying an auxiliary network of a vehicle, taking into account the different power levels required for the different standby states of the vehicle.

This object is achieved by an electrical conversion system comprising:

• Two main inputs connected to a battery used for storing electrical energy and a main output on which is delivered a so-called auxiliary voltage intended for an auxiliary network from an input voltage supplied between its main inputs by said battery,
• A conversion unit comprising:
  • Two secondary inputs connected respectively to the two main inputs and a secondary output connected to the main output of the system,
  • A first DC/DC type electrical converter comprising first inputs respectively connected to the two secondary inputs of the conversion unit and a first output connected to the secondary output of the conversion unit, said first converter being capable of being controlled to generate the auxiliary voltage from the input voltage and to provide a first electric power on its first output,

Said electrical conversion system being particular in that:

• The conversion unit comprises a second DC/DC type electrical converter comprising second inputs connected respectively to the two secondary inputs of the conversion unit and a second output connected to the secondary output of the conversion unit, said second converter being adapted to be controlled to generate on its second output said auxiliary voltage, from the input voltage,
• It comprises an analog control circuit connected between the secondary output of the conversion unit and a control input of said second electrical converter, said analog control circuit comprising:
  • Means for comparing the value of the output electric current supplied on the secondary output of the conversion unit with a threshold value,
  • Control means connected to said control input of the second electrical converter and configured to generate an analog control signal on said control input when the output current exceeds said threshold value,
• The second electric converter is configured to supply a second electric power having a higher value than that of the first electric power supplied by the first electric converter, according to the state of said control signal present on its control input.

By state of the control signal is meant the presence or absence of the control signal, as well as, possibly, the amplitude level of this control signal and/or its frequency.

According to one feature, said first electrical power supplied by the first electrical converter is less than or equal to a power threshold value and in that the current threshold value is set so that the second electrical converter is activated before the first electrical power provided the first electrical converter reaches said power value.

According to another feature, the comparison means comprise means for measuring the current flowing on the secondary output of the conversion unit.

According to another feature, the means of comparison comprise an operational amplifier or a hysteresis comparator, capable of receiving as input an image voltage of the current flowing on the secondary output of the conversion unit and a reference voltage generated by a reference.

According to another feature, the control means comprise:

• A control assembly comprising an input capable of receiving a trigger signal from the comparison means,
• A relay connected to the control assembly and able to generate said control signal, according to the state of said trigger signal.

According to another feature, the relay of said control means is an optocoupler.

According to another feature, the second inputs of the second converter are formed of a positive terminal and a negative terminal and in that the second converter is configured to be in an inactive state when its control input is connected to its negative terminal and in an active state when its control input is disconnected from its negative terminal.

According to another feature, the system comprises a first diode connected to the first output of the first converter and a second diode connected to the second output of the second converter.

According to another feature, the system comprises an electrical insulation barrier arranged to separate a high voltage part from a low voltage part of the system.

The invention also relates to an electrical power supply system comprising a battery comprising two terminals between which it is capable of delivering an input voltage, this electrical power supply system comprising an electrical conversion system as defined above, of which the two main inputs are respectively connected to the two terminals of said battery.

The invention finally relates to an electric or hybrid vehicle, comprising an auxiliary power supply network on which a so-called auxiliary voltage is delivered, this vehicle carrying an electric power supply system as defined above for generating said auxiliary voltage.

Brief description of figures

Other characteristics and advantages will appear in the detailed description which follows given with regard to the appended drawings in which:

• There represents the general architecture of the electrical conversion system of the invention and illustrates its principle of operation;
• There represents a concrete embodiment of the electrical conversion system of the invention;

Detailed description of at least one embodiment

In the rest of the description, the term "terminal" used is not to be considered in a limiting manner, that is to say in the material sense of the term. It is used to better describe the connections made between the different blocks of the system. It should be understood as a simple electrical connection point.

There shows a battery (also called a battery pack) intended for storing electrical energy and which can be used to tow an electric or hybrid vehicle. This battery may comprise one or more electrical energy storage modules connected in series.

An electrical energy storage module can be composed of one or more electrochemical cells (not shown) connected in series and/or parallel. In a non-limiting manner, for a vehicle, a battery can comprise eight modules in series, each module possibly comprising any number of electrochemical cells, for example twelve cells.

Each battery is for example capable of supplying a voltage of 400V intended for the traction of the vehicle. This battery is also used to provide the voltage necessary to supply an auxiliary network AUX of the vehicle (also called a vehicle's on-board network).

To supply this auxiliary network AUX, an electrical conversion system is used intended to convert the voltage supplied by the battery, called the input voltage, into a second voltage intended for supplying the auxiliary network, this second voltage being called the auxiliary voltage V_aux.

With reference to the , the conversion system comprises two main input terminals A1, A2 respectively connected to the two terminals of the battery, to receive the input voltage V_batt supplied by the battery BATT and a main output terminal A3 on which the voltage is distributed auxiliary V_aux.

The conversion system comprises a conversion unit 2 responsible for supplying the auxiliary voltage V_aux from the input voltage V_batt.

This conversion unit 2 comprises two secondary input terminals B1, B2, each connected to a separate main input terminal of the system and a secondary output terminal B3 connected to the main output terminal A3 of the system.

The conversion unit 2 comprises a first converter U1 of the DC/DC (direct/direct) type.

This first converter U1 conventionally comprises two first input terminals C1, C2, a positive terminal and a negative terminal, respectively connected to the two secondary input terminals B1, B2 of the conversion unit 2, two first output terminals C3 , C4 connected to system secondary output terminal B3 and ground respectively.

It can be controlled to convert the input voltage V_batt applied between its two first input terminals into an electrical output potential applied to its first output terminal, to generate the auxiliary voltage V_aux with respect to ground.

According to the invention, the conversion unit 2 comprises a second DC/DC converter U2, also configured to convert the input voltage V_batt supplied by the battery BATT into an output voltage corresponding to the auxiliary voltage V_aux.

This second converter U2 comprises two second input terminals D1, D2, a positive terminal and a negative terminal, respectively connected to the two secondary input terminals B1, B2 of the conversion unit 2 and two second output terminals D3, D4 connected respectively to the secondary output terminal B3 of the conversion unit and to ground. It will be seen that this second converter U2 also comprises a control input PC, through which it can be controlled in the active state or in the inactive state. Depending on the type of component used, the active state of the converter can for example be generated in the presence or in the absence of a control signal S2 on its control input PC. In other words, the second converter U2 can be configured by default in the active state and the reception of the control signal S2 deactivates it or by default in the inactive state and the reception of the control signal S2 makes it active. Of course, other activation/deactivation principles could be envisaged.

The two converters U1, U2 are thus connected in parallel with the battery BATT.

According to the invention, the first converter U1 is configured to supply a first electric power and the second converter U2 is configured to supply a second electric power. The second electric power has a higher value than that of the first electric power.

The first electrical power is thus used and sufficient for supplying the auxiliary network AUX in the first prolonged standby state of the vehicle while the second electrical power is additionally injected for supplying the auxiliary network AUX in the second standby state , before starting, of the vehicle.

The electrical conversion system 1 also comprises an analog control circuit 3, having an architecture suitable for activating the second converter U2 when a higher power level is required. The first converter U1 is thus kept permanently active to maintain the auxiliary voltage V_aux on the auxiliary network AUX while the second converter U2 is activated only when necessary to provide the necessary surplus power.

The analog control circuit 3 is connected between the secondary output terminal B3 of the conversion unit 2 and the control input PC of the second converter U2.

In general, this analog control circuit 3 comprises:

• Comparison means M1 of the electric current I_s present on the secondary output terminal B3 of the conversion unit 2;
• Control means M2 of the second converter U2, connected to the comparison means M1 and responsible for controlling the second converter U2 from a trigger signal S1 supplied by the comparison means; The control means are configured to activate/deactivate the second converter U2 according to the state of the control signal S2;

It should be noted that the trigger signal S1 and the control signal S2 are both analog signals.

By state of the control signal S2 is meant for example the presence or absence of the control signal S2, as well as, possibly, the amplitude level of this control signal S2 and/or its frequency.

The comparison means M1 are configured to compare the current I_s which flows through the secondary output terminal of the conversion unit with a threshold value I_th.

We will see below, with reference to the , that the comparison means M1 are preferably configured to compare voltages, the image voltage of the current I_s and a reference voltage V_ref generated by a reference circuit.

The comparison means M1 comprise two inputs E1, E2 respectively receiving the current threshold value I_th or a corresponding voltage and the measured current I_s or a corresponding voltage, and an output E3 to which they are capable of applying the trigger signal S1 when the current I_s exceeds the threshold value I_th.

The control means M2 comprise an input F1 able to receive the trigger signal S1 and an output F2 on which they are able to generate the control signal S2 intended for the control input PC of the second converter U2.

It should be noted that, given that the main input terminals A1 and A2 connected to the traction battery are not electrically connected to the main output terminal A3, nor to earth, an insulation barrier is implied. in the diagram shown in and the converters U1, U2 and the control means M2 are designed to cross this insulation barrier while resisting the voltage difference which may exist there.

There represents a particular architecture of the conversion system of the invention. This architecture is to be considered in a non-limiting way. It is of course obvious that it would be possible to carry out the various functions by using other components and other arrangements.

In a non-limiting manner, the comparison means M1 can comprise a current measurement resistor R3 connected to the secondary output terminal of the conversion unit 2. The voltage drop across the terminals of this resistor R3 is monitored by a component of voltage monitoring U4 (called "current shunt monitor"), the gain of which is fixed by a resistor R6 and a capacitor C_1. This component U4 thus generates an electric potential representative of the output current I_s.

The reference circuit U5 is connected to the main output terminal A3 of the system and makes it possible to pick up the electric potential V_aux applied to this main output terminal A3. From the electric potential V_aux, the reference circuit U5 generates the reference voltage V_ref.

In a non-limiting manner, the comparison means M1 can comprise a component U6 of the hysteresis comparator or operational amplifier type, receiving as input the electric potential generated by the monitoring component U4 and the reference electric potential V_ref generated by the reference circuit U5 via a resistive bridge of two resistors R7, R8. Two other resistors R9, R10 make it possible to adjust the difference due to the hysteresis. The output of this component U6 remains in the low state, as long as the electrical potential at the output of the monitoring component U4 remains below a threshold value set at the midpoint by the two resistors R7 and R8 and by the reference electrical potential V_ref generated at the output of the reference circuit U5. This condition is thus satisfied when the current flowing on the output of the conversion unit fulfills the following condition:

I_ s < V _ ref * (R8 * 5kohm) / ((R7 + R8) * R3 * R6)

With :

V_ref which corresponds to the value of the reference electric potential generated by the reference circuit U5;

V_ref *(R8*5kohm)/((R7+R8)*R3*R6) which corresponds to said threshold value I_th;

Of course, it should be understood that the relation which fixes the threshold value I_th is linked to the electronic architecture used to implement the comparison. If other components were used, the relation defining I_th would be different.

In a non-limiting manner, the control means M2 of the analog control circuit 3 comprise an input terminal F10, and two output terminals F20, F21. Input terminal F10 is connected to the output of component U6 of comparison means M1.

The control means M2 comprise for example two field effect transistors Q1, Q2 connected in cascade. The first transistor Q1 has its gate connected to the input terminal F10 of the control means M2, via a resistor R11, and its source connected to ground. The second transistor Q2 has its gate connected to the drain of the first transistor Q1, its drain connected, via a resistor R14, to a driver component U3 and its source connected to a voltage source, supplying the auxiliary voltage V_aux. A resistor R12 is connected between the gate and the source of the first transistor Q1. A resistor R13 is connected between the gate and the source of the second transistor Q2. The first transistor Q1 is for example an 'n' channel MOSFET and the second transistor Q2 is a 'p' channel MOSFET.

The driving component U3 is configured to drive the second converter U2.

In the system, the two converters U1, U2 are arranged astride an insulation barrier 4 (shown in dotted lines on the ), ensuring insulation between the battery and the rest of the vehicle. The control component U3 is also arranged at this isolation barrier 4. In general, this control component U3 is made in the form of a relay.

In a non-limiting way, the component U3 can be made in the form of an optocoupler operating for example in normally closed mode ("normally ON" in English). It comprises two first terminals located on the low voltage side and two second terminals located on the high voltage side (battery side), on either side of the insulation barrier 4. By default, if no current flows between its first two terminals, its two second terminals are interconnected. And if a current flows between its first two terminals, the two second terminals are disconnected from each other. The two second terminals of the control component U3 are respectively connected to the control input PC of the second converter U2 and to the negative terminal of the second converter, thus making it possible to control it.

The second converter in fact comprises the PC control input. In the architecture represented, if this control input PC is free and is not connected to any potential or connected to a high impedance, the second converter is active, that is to say it provides an electric potential on its output terminal. If the control input PC is connected to the negative input terminal of the second converter, the latter is inactive and provides no electric potential on its output terminal.

As indicated above, the second converter U2 therefore remains inactive when its control input PC is connected by a short circuit to its negative terminal.

Thus, in operation, as long as the output current I_s fulfills the above condition, i.e. it is lower than the threshold value I_th, the voltage applied to the gate of the first transistor Q1 is at l low state, the first transistor Q1 remains open. The second transistor Q2 also remains open. Thus no current flows between the first two terminals of the control component U3. The control input PC of the second converter U2 is short-circuited to its negative terminal, via the link between the two second terminals of the control component. The second converter is thus inactive.

On the other hand, when the current I_s becomes greater than the threshold value I_th defined by the above relation, the first transistor Q1 switches to the closed state, also causing the closing of the second transistor Q2. A current thus flows between the first two terminals of the control component U3, causing the disconnection of the two second terminals of the control component. The PC control input of the second converter U2 is no longer short-circuited. The second converter becomes active.

It should be noted that it is important to correctly set the threshold value I_th of the switching current so that the second converter U2 is activated before the first converter U1 reaches its upper limit of power supplied, to avoid a gradual drop. voltage on the auxiliary network. It is thus preferable to take a little safety margin on the activation threshold of the second converter U2.

The choice to use a fixed voltage value V_ref is justified by the fact that the auxiliary network can vary its voltage, although its nominal value is fixed (for example at 12V). The V_ref value of the voltage reference must be less than the difference between the minimum value that the voltage of the auxiliary network can reach and the intrinsic voltage drop of the component chosen in the reference circuit U5.

At the output of each converter U1, U2, the conversion unit comprises an assembly formed by a resistor and a diode connected in series (R1, D_1 for the first converter U1 and R2, D_2 for the second converter U2), placed in the circuit so that the output of one converter does not discharge into that of the other converter, thus allowing parallel operation of the two converters.

As indicated above, the resistors R4 and R5 fix the output voltage of the second converter U2 which is advantageously set at a lower level than that of the first converter U1.

In a non-limiting way, the second converter U2 can also include an analog control input SC. The converter can be configured to supply a variable output voltage on its output terminal, controlled in a linear manner by an analog control signal applied to its analog control input SC. In the context of the invention, this analog control input advantageously receives a constant signal, to maintain the electrical output potential at a constant level on its output terminal. This constant electric potential is obtained by connecting a resistive bridge composed of two resistors R4, R5 connected between the positive terminal and the negative terminal, and whose midpoint is connected to this analog control input SC.

The invention thus has many advantages, including:

• Simplicity of architecture and operation, linked to an entirely analog construction, allowing robustness and safety;
• Particularly low consumption, the analog control circuit using only low consumption components;
• A particularly reactive solution, linked to the use of an analog circuit, requiring no digital processing or communication protocol;

Claims (11)

Electrical conversion system (1) comprising:

• Two main inputs (A1, A2) connected to a battery (BATT) used for storing electrical energy and a main output (A3) on which is delivered a so-called auxiliary voltage (V_aux) intended for an auxiliary network from an input voltage supplied between its main inputs by said battery,
• A conversion unit (2) comprising:
  • Two secondary inputs (B1, B2) connected respectively to the two main inputs (A1, A2) and one secondary output (B3) connected to the main output (A3) of the system,
  • A first electrical converter (U1) of the DC/DC type comprising first inputs (C1, C2) connected respectively to the two secondary inputs (B1, B2) of the conversion unit (2) and a first output (C3) connected to the secondary output (B3) of the conversion unit, said first converter being capable of being controlled to generate the auxiliary voltage (V_aux) from the input voltage and to supply a first electric power on its first output (C3) ,

Said electrical conversion system being characterized in that:

• The conversion unit (2) comprises a second electrical converter (U2) of the DC/DC type comprising second inputs (D1, D2) respectively connected to the two secondary inputs (B1, B2) of the conversion unit (2) and a second output (D3) connected to the secondary output (B3) of the conversion unit, said second converter (U2) being capable of being controlled to generate on its second output said auxiliary voltage (V_aux), from the input voltage,
• It comprises an analog control circuit (3) connected between the secondary output (B3) of the conversion unit and a control input (PC) of said second electric converter (U2), said analog control circuit (3) comprising:
  • Comparison means (M1) of the value of the output electric current (I_s) supplied on the secondary output (B3) of the conversion unit with a threshold value (I_th),
  • Control means (M2) connected to said control input (PC) of the second electrical converter (U2) and configured to generate an analog control signal (S2) on said control input when the output current (I_s) exceeds said threshold value (I_th),
• The second electric converter (U2) is configured to supply a second electric power having a higher value than that of the first electric power supplied by the first electric converter (U1), according to the state of said control signal (S2) present on its control input (PC).

System according to Claim 1, characterized in that the said first electrical power supplied by the first electrical converter (U1) is less than or equal to a power threshold value and in that the current threshold value (I_th) is fixed so that the second electric converter (U2) is activated before the first electric power supplied by the first electric converter reaches said power value. System according to Claim 1 or 2, characterized in that the comparison means include means for measuring the current (I_s) flowing on the secondary output of the conversion unit (3). System according to one of Claims 1 to 3, characterized in that the means of comparison (M1) comprise an operational amplifier or a hysteresis comparator, capable of receiving as input an image voltage of the current (I_s) flowing on the secondary output (B3) of the conversion unit (3) and a reference voltage (V_ref) generated by a reference circuit (U5). System according to one of Claims 1 to 4, characterized in that the control means (M2) comprise:

• A control assembly comprising an input capable of receiving a trigger signal (S1) from the comparison means (M1),
• A relay connected to the control assembly and able to generate said control signal (S2), according to the state of said trigger signal.

System according to Claim 5, characterized in that the relay of the said control means (M2) is an optocoupler. System according to one of Claims 1 to 6, characterized in that the second inputs of the second converter (U2) are formed by a positive terminal (D1) and a negative terminal (D2) and in that the second converter is configured to be in an inactive state when its control input (PC) is connected to its negative terminal (D2) and in an active state when its control input is disconnected from its negative terminal. System according to one of Claims 1 to 7, characterized in that it comprises a first diode (D_1) connected to the first output (C3) of the first converter (U1) and a second diode (D_2) connected to the second output (D3) of the second converter (U2). System according to one of Claims 1 to 8, characterized in that it comprises an electrical insulation barrier (4) arranged to separate a high voltage part from a low voltage part of the system. Electrical power supply system comprising a battery (BATT) comprising two terminals between which it is capable of delivering an input voltage (V_batt), characterized in that it comprises an electrical conversion system as defined in one of claims 1 to 9, whose two main inputs (A1, A2) are respectively connected to the two terminals of said battery (BATT). Electric or hybrid vehicle, comprising an auxiliary power supply network (AUX) on which is delivered a so-called auxiliary voltage (V_aux), characterized in that it embeds an electric power supply system as defined in claim 10 for generating the said voltage auxiliary (V_aux).