FR3056876A1 - ELECTRIC HEATING DEVICE FOR MOTOR VEHICLE POWERED BY TWO ELECTIC POWER SUPPLY NETWORKS - Google Patents

Abstract

The present invention relates to an electric heater (1) adapted to be powered by a first and second networks, the electric heater (1) comprising: - three connection interfaces respectively with the first network, the second network, and a communication bus; a functional module (11); - a main switch (Q2); a first protection module (10) comprising: a microcontroller (MC) for detecting an overvoltage between the functional module (11) and the first and / or third connection interfaces (112, ILW), and for opening a second switch protection (Q4); - a secondary switch (Q6) adapted to open during said overvoltage so as to open the main switch (Q2); - said second protective switch (Q4) adapted to open so as to open the secondary switch (Q6).

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an electric heating device for a motor vehicle adapted to be supplied with voltage by a first electrical supply network and by a second electrical supply network.

It finds a particular, but not limiting, application in motor vehicles.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

In the field of electric heating devices for a motor vehicle, in particular when these electric heating devices are additional devices, it is known to supply an electric heating device by two different electrical supply networks, one being one high power power supply network used to supply high voltage to resistive heating elements of the electric heater and the other being a low power power supply network used to provide lower voltage to control elements of the heater current in the heating resistors. The heating resistors and the control elements are part of the same functional module. To this end, the electric heating device includes a communication bus on which heating instructions can be sent to it and a connection interface with each electric power network. The communication bus is supplied by the same power supply network as the control elements.

A disadvantage of this state of the art is that if a problem such as a short circuit occurs in the functional module comprising said control elements, there is a risk that the high voltage supplied by the high power power supply network is not found on the connection interface connected to the low power power supply network and on the communication bus, thus creating a dangerous voltage, called overvoltage, which may damage them.

In this context, the present invention aims to solve the aforementioned drawback.

GENERAL DESCRIPTION OF THE INVENTION

To this end, the invention provides an electric heating device for a motor vehicle adapted to be supplied with voltage by a first electric supply network and by a second electric supply network, according to which the electric heating device comprises:

- a first interface for connection with the first power supply network;

- a second interface for connection with the second power supply network;

- a third interface for connection with a communication bus;

- a functional module connected to the first connection interface and to the second connection interface;

- a main switch connected to the functional module adapted to transmit signals on the communication bus;

a first protection module adapted to isolate the first electrical supply network and the communication bus from the second electrical supply network when there is an overvoltage between the functional module and the first connection interface and the third connection interface , said first protection module comprising:

- an overvoltage detection module comprising a microcontroller suitable for:

- detecting an overvoltage between the functional module and the third connection interface and / or between the functional module and the first connection interface;

- open a second protection switch following said detection;

- a secondary switch adapted to open when there is said overvoltage so as to open the main switch;

- said second protection switch adapted to open so as to open the secondary switch.

Thus, as will be seen in detail below, the first protection module will detect an overvoltage between the functional module and the first connection interface and the third connection interface, and will deactivate the main switch so that it is opened following the detection of such an overvoltage. This will disconnect the high power power supply network from the low power power supply network and the communication bus. The latter will therefore not be impacted by said overvoltage and will therefore be protected.

Opening the secondary switch prevents currents flowing from the second power supply network to the first power supply network. This thus protects the communication bus against an overvoltage.

According to non-limiting embodiments, the electric heating device can also include one or more additional characteristics among the following:

According to a nonlimiting embodiment, said microcontroller comprises:

- a first input adapted to measure the first voltage between the functional module and the secondary switch;

- an output suitable for controlling the opening of the second protection switch;

- a second input suitable for measuring a voltage between the functional module and the main switch.

According to a nonlimiting embodiment, the signals are signals of low logic.

According to a nonlimiting embodiment, the low logic signals are 0 Volt signals.

According to a nonlimiting embodiment, the electric heating device further comprises a main non-return diode adapted to prevent a current from flowing to the first power supply network when the main switch is open. This protects the first power supply network.

According to a nonlimiting embodiment, the electric heating device further comprises a secondary non-return diode adapted to prevent a current from flowing in the second protection switch. This protects said second protection switch.

According to a nonlimiting embodiment, the electric heating device further comprises a main return resistor adapted to guarantee the opening of the main switch when said overvoltage exists.

According to a nonlimiting embodiment, the electric heating device further comprises a secondary return resistor adapted to guarantee the opening of the secondary switch when there is said overvoltage.

According to a nonlimiting embodiment, the electric heating device further comprises a basic resistance adapted to guarantee the closing of the secondary switch when a current flows in said secondary switch.

According to a nonlimiting embodiment, the electric heating device further comprises a self-resetting fuse adapted to protect the communication bus against an overcurrent. This protects said communication bus.

According to a nonlimiting embodiment, the electric heating device also comprises a tertiary non-return diode adapted to guarantee that the main switch remains open.

According to a nonlimiting embodiment, the electric heating device further comprises a protection diode adapted to protect the main switch against an increase in the voltage of the first electrical supply network. This prevents it from being damaged.

According to a nonlimiting embodiment, the electric heating device further comprises an additional protection diode adapted to protect the secondary switch against a voltage reversal. This prevents it from being damaged by negative voltage.

According to a nonlimiting embodiment, the first electrical supply network is adapted to supply a voltage lower than a voltage supplied by the second electrical supply network.

According to a nonlimiting embodiment, the first electrical supply network is adapted to supply a voltage of 12Volts.

According to a nonlimiting embodiment, the second electrical supply network is adapted to supply a voltage of 48Volts.

According to a nonlimiting embodiment, the communication bus is a LIN bus or a PWM bus. A LIN bus allows you to use only one wire for sending and receiving signals. Thus, only one wire is used for two different functions, namely a diagnostic function and a setpoint function. It is also possible to use any other type of communication bus making it possible to have bidirectional communication. A PWM bus is used to receive or send signals with a controlled duty cycle.

According to a nonlimiting embodiment, the functional module comprises a control module adapted to be supplied with voltage by the first electrical supply network and for receiving and / or transmitting signals via the communication bus. The functional module can thus exchange information with another electronic device via its control module. It can thus send diagnostic information and receive setpoint information.

According to a nonlimiting embodiment, the functional module comprises at least one resistive heating element connected to the first connection interface and at least one associated control element connected to the second connection interface, said control element being adapted to control said resistive heating element. In particular, said control element is adapted to control the current of said resistive heating element.

According to a nonlimiting embodiment, the main switch is arranged near the third connection interface. This minimizes the communication link between the main switch and the third connection interface. This protects said communication link against a short circuit that could occur between the main switch and the third connection interface.

According to a nonlimiting embodiment, the first connection interface and the second connection interface are connected to a common ground, and the electric heating device also further comprises a second protection module adapted to isolate the first network of power supply and the communication bus of the second power supply network in the event of a loss of the common ground.

According to a nonlimiting embodiment, the second protection module comprises:

- said secondary switch;

- said second protection switch;

- said secondary non-return diode.

Thus, part of the components of the first protection module are used to protect the first network and the communication bus against a common loss of mass. This reduces the costs and also the complexity of the architecture of the electric heating device 1 for the protections.

The invention also applies to an air blower for a motor vehicle. Thus, according to a nonlimiting embodiment, there is also proposed an air blower for a motor vehicle adapted to be supplied with voltage by a first electrical supply network and by a second electrical supply network, according to which the blower of air includes:

- a first interface for connection with the first power supply network;

- a second interface for connection with the second power supply network;

- a third interface for connection with a communication bus;

- a functional module connected to the first connection interface and to the second connection interface;

- a main switch connected to the functional module adapted to transmit signals on the communication bus;

a first protection module adapted to isolate the first electrical supply network and the communication bus from the second electrical supply network when there is an overvoltage between the functional module and the first connection interface and the third connection interface , said first protection module comprising:

- an overvoltage detection module comprising a microcontroller suitable for:

- detecting an overvoltage between the functional module and the third connection interface and / or between the functional module and the first connection interface;

- open a second protection switch following said detection;

- a secondary switch adapted to open when there is said overvoltage so as to open the main switch;

- said second protection switch adapted to open so as to open the secondary switch.

BRIEF DESCRIPTION OF THE FIGURES

The invention and its various applications will be better understood on reading the following description and on examining the figures which accompany it:

FIG. 1 represents a diagram according to a nonlimiting embodiment of the invention of an electric heating device for a motor vehicle, said electric heating device being supplied by a first and a second electrical supply network, and connected to a communication bus and comprising a first overvoltage protection module and a second protection module against a ground fault;

- Figure 2a shows a diagram of the electric heating device of Figure 1 with the detail of the electronic components of the first protection module according to a non-limiting embodiment;

- Figure 2b shows a diagram of the electric heating device of Figure 1 with the detail of the electronic components of the second protection module according to a non-limiting embodiment;

- Figure 3 shows a diagram of the electric heater of Figure 1 when there is a short circuit in the second power supply network according to a non-limiting embodiment;

- Figure 4 shows a diagram of the electric heating device of Figure 1 when the mass is lost according to a non-limiting embodiment;

- Figure 5 shows a diagram of the electric heating device of Figure 1 when it receives signals from another electronic device, according to a non-limiting embodiment;

- Figure 6 shows a diagram of the electric heating device of Figure 1 when it sends signals to another electronic device, according to a non-limiting embodiment;

- Figure 7 shows a flowchart illustrating the operation of a main switch of the electric heating device of Figure 1 according to a non-limiting embodiment.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Identical elements, by structure or by function, appearing in different figures keep, unless otherwise specified, the same references.

The electric heating device 1 for a motor vehicle is described with reference to Figures 1 to 6 according to a non-limiting embodiment.

By motor vehicle is meant any type of motor vehicle.

The electric heating device 1 is supplied with voltage by a first electrical supply network G12 and by a second electrical supply network G48.

In the following description, the terms power supply network and network will be used interchangeably.

As illustrated in FIG. 1, the electric heating device 1 comprises:

a first connection interface 112 with the first power supply network G12;

- a second connection interface I48 with the second power supply network G48;

- a third ILW connection interface with a BLW communication bus;

a functional module 11 connected to the first connection interface 112 and to the second connection interface I48;

- a main switch Q2 connected to the functional module 11 and adapted to transmit DAT signals on the BLW communication bus;

a first protection module 10 adapted to isolate the first power supply network G12 and the communication bus BLW from the second power supply network G48 when there is a USS overvoltage between the functional module 11 and the first connection interface 112 and the third ILW connection interface.

The electric heater 1 is part of an NLW communication network.

In a nonlimiting example, a USS overvoltage appears between the functional module 11 and the first connection interface 112, and between the functional module 11 and the third connection interface ILW, when there is a DC short circuit in the functional module. 11.

Such a DC short circuit is taken as a nonlimiting example in the following description. In the following description, a DC short circuit in the functional module 11 will also be simply cited as a DC short circuit. It will be noted that when a short circuit CC occurs in the functional module 11, this means that the elements of the functional module 11 which the DLW control module will be defective are destroyed.

As will be seen in detail below, during a DC short circuit on the functional module 11 which generates such a USS overvoltage, all of the components of the functional module 11 rise to the potential of the voltage supplied by the second G48 power supply network. This results in the appearance of potential differences and therefore of currents flowing between said functional module 11 and:

- the first connection interface 112;

- the first protection module 10;

- the BLW communication bus.

These currents and voltages risk damaging in particular the first connection interface 112 and the BLW communication bus. The main non-return diode D8 and the first protection module 10 make it possible to protect these elements against said currents and voltages.

In particular, the first protection module 10 will make it possible to isolate the first connection interface 112 and the third connection interface ILW and consequently the communication bus BLW from a dangerous voltage, namely said overvoltage USS. Indeed, these interfaces which are sized for a low voltage G12 power supply network (here 12V) cannot withstand a voltage that is too large, for example greater than 40V.

The first protection module 10 includes:

- an overvoltage detection module 100 comprising a microcontroller MC suitable for:

- detecting a USS overvoltage between the functional module 11 and the third connection interface ILW and / or between the functional module 11 and the first connection interface 112;

- send an opening instruction C1 to a second protection switch Q4;

- a secondary switch Q6;

- said second protection switch Q4.

As described in detail below, when there is a short circuit which causes a USS overvoltage, the microcontroller MC detects it and triggers the opening of the second protection switch Q4. Opening the second protection switch Q4 will open the secondary switch Q6. Finally, the opening of the secondary switch Q6 will cause the opening of the main switch Q2. The opening of the main switch Q2 will make it possible to isolate the first and third connection interfaces 112, ILW from the second network G48 and consequently to isolate the first network G12 and the communication bus BLW from the second network G48. The first G12 network and the BLW communication bus will thus be protected from said USS overvoltage.

In a nonlimiting embodiment, the electric heating device 1 also comprises a main non-return diode D8.

In a nonlimiting embodiment, the electric heating device 1 also comprises a main return resistor R7.

In a nonlimiting embodiment, the electric heating device 1 also comprises a secondary return resistor R15.

In a nonlimiting embodiment, the electric heating device 1 also comprises a secondary non-return diode D11.

In a nonlimiting embodiment, the electric heating device 1 also comprises a basic resistance R14.

The various elements of the electrical device 1 are described in more detail below.

• Connection interfacesJJ. ^. We ^ JLWj.JGND The first connection interface 112 is suitable for connecting the electric heating device 1 with the first power supply network G12. It is an input that receives a voltage supplied by the first G12 power supply network.

The second connection interface I48 is suitable for connecting the electric heating device 1 with the second power supply network G48. It is an input that receives a voltage supplied by the second G48 power supply network.

The first and second networks G12, G48 are connected to batteries (not shown) of the motor vehicle which are voltage generators.

In a nonlimiting embodiment, the first electrical supply network G12 is adapted to supply a voltage U1 (called first voltage) lower than a voltage U2 (called second voltage) supplied by the second electrical supply network G48.

In a nonlimiting embodiment, the first power supply network G12 is adapted to supply a voltage U1 substantially equal to 12V (Volts). It’s a low power network.

In a nonlimiting embodiment, the second power supply network G48 is adapted to supply a voltage U2 substantially equal to 48V (Volts). It’s a high power network. It should be noted that a battery, connected to the second G48 network, which usually supplies a voltage of 48V makes it possible to supply a voltage which can rise to 58V.

It should be noted that a voltage, for example 12V, supplied by a battery is generally very unstable. Thus, in a nonlimiting example, in the event of faults in the alternator of the motor vehicle, the voltage can rise very high, sometimes up to 100V. Also, in a nonlimiting embodiment, the voltage U1 supplied by the network G12 is filtered. This makes it possible to limit the voltage U1 which supplies the electric heating device 1, in particular the secondary switch Q6 and the second protection switch Q4 described below. In FIGS. 2a and 2b, the filtered voltage U1 is thus represented in a triangle and inside the frame of the electric heating device 1. The filtering of a voltage being known to those skilled in the art, it is not not described here.

In the following description, we will speak indifferently of first voltage U1 or voltage U1, and of second voltage U2 or voltage U2.

In the following description, the voltages of 12V for the voltage U1 and of 48V for the voltage U2 will be taken as nonlimiting examples.

In a nonlimiting embodiment, the first connection interface 112 and the second connection interface I48 are connected to the same ground GDN, also called common ground GND.

They are connected by a ground cable CX to said common ground GND. Thanks to this common GND mass, overheating of the electric heating device 1 is avoided. Such overheating can indeed occur if two different masses are used, the two masses being dimensioned differently. In this case, there is a ground cable (called signal ground cable) connected to the first connection interface 112 and a ground cable (called power ground cable) connected to the second connection interface I48. When the hot power ground cable is disconnected, in this case, there is indeed a risk that the signal ground cable will burn because the two masses are dimensioned differently.

The third connection interface ILW is suitable for connecting the electric heating device 1 with a communication bus BLW. It's an entrance.

The connection interfaces 112, I48, ILW thus comprise electrical connections suitable for making the connections respectively with the first power supply network G12, the second power supply network G48 and the communication bus BLW.

In a first non-limiting embodiment, the BLW communication bus is a LIN (“Local Internetconnect Network”) communication bus. The electric heater 1 is thus part of a NLW communication network called LIN. A LIN communication bus is a bidirectional communication bus. Thus, a LIN communication network allows the use of only one wire for the communication of signals.

In a second nonlimiting embodiment, the communication bus BLW is a communication bus PWM ("Puise Modulation Width"). The electric heater 1 is thus part of a NLW communication network called PWM. A PWM communication bus is a unidirectional bus. Thus, in this case, the electric heater 1 comprises two unidirectional PWM communication buses, one being used for receiving signals, and the other being used for sending signals.

The BLW communication bus makes it possible to convey DAT signals from the electric heating device 1 to an external electronic device 2 (described below) and / or from the external electronic device 2 to the electric heating device 1. It will be noted that there are a communication line LLW internal to the electric heating device 1 between the functional module 11 and the third connection interface ILW over which said signals from the functional module 11 pass. In a non-limiting embodiment, this communication line is an electronic track .

As illustrated in FIG. 1 also, in a nonlimiting embodiment, the electric heating device 1 also comprises an earth interface IGND. The IGND mass interface is an output. It will be noted that in a nonlimiting example, the ground cable CX connects the ground interface IGND to the chassis of the motor vehicle which forms a ground plane.

In a nonlimiting embodiment, the first protection module 10, the functional module 11, the main non-return diode D8 and the main switch Q2 are part of the same printed circuit card, called PCBA card (in English "Printed Circuit Board Assembly"). This PCBA printed circuit board is thus connected to the ground plane formed by the chassis of the motor vehicle.

As illustrated in FIG. 1, in a nonlimiting embodiment, the first connection interface 112 and the third connection interface ILW are part of the same connector BN12. This allows not to multiply the connectors.

As illustrated in FIG. 1, in a nonlimiting embodiment, the second connection interface I48 and the ground interface IGND are part of the same connector BN48. This allows not to multiply the connectors.

• .Lot®Çrup.teur.prinçipal.C2

The main switch 02 is suitable for transmitting DAT signals on the BLW communication bus.

To this end, it is connected to the BLW communication bus via the third ILW connection interface. It is arranged between the BLW communication bus and the functional module 11, in particular its DLW control module (described below).

In a nonlimiting embodiment, the main switch Q2 is a MOSFET transistor. In a nonlimiting variant, it is an N-channel transistor.

In this case, the gate G of the transistor receives the first voltage U1, namely the voltage of 12V in the nonlimiting example taken, the source S is connected to the communication bus BLW via the third connection interface ILW, and the drain D is connected to the DLW control module.

The main switch Q2 has a threshold voltage Vgsth.

The main switch Q2 is closed when its voltage Vgs is equal to the voltage U1 supplied by the first network G12, namely here 12V. When the DAT signals which circulate on the communication bus BLW are at 0V in a nonlimiting embodiment, the drain D and the source S are at potential 0V. The gate G being supplied by the voltage U1 of 12V, the voltage Vgs is therefore at 12V. Vgs being higher than a threshold voltage Vgsth, the main switch Q2 closes well. In a nonlimiting example, Vgsth = 2V.

In a nonlimiting embodiment, the main switch Q2 comprises a breakdown voltage greater than 48Volts. In a nonlimiting variant, the breakdown voltage is substantially equal to 100Volts. The main switch Q2 thus supports the voltage U2, here 48V, which it receives (in particular between the source S and the drain D in the nonlimiting embodiment of the MOSFETS) during an overvoltage USS or when the common ground GND is lost.

The main switch Q2 is open when the voltage Vgs is less than the voltage Vgsth, that is to say when Vgs is substantially equal to 0V in a nonlimiting example. As we will see below, the main switch Q2 opens:

- thanks to the first protection module 10 when there is a USS overvoltage; and

- thanks to the second protection module 20 when the common GND ground is lost.

Thus, as will be seen later in the description, the first protection module 10 makes it possible to protect the first power supply network G12 and the communication bus BLW against a USS overvoltage, while the second protection module 20 allows protect the first power supply network G12 and the communication bus BLW against a common ground loss GND.

In a nonlimiting embodiment, the main switch Q2 is disposed near the third connection interface ILW, namely substantially close to said connector BN12, so as to minimize the length of the communication line LLW between said main switch Q2 and said third ILW connection interface. This allows a minimum of electronic track which forms the LLW communication line on the PCBA printed circuit board on which the main switch Q2 is placed between the source S of the main switch Q2 and the connector BN12. This minimizes the risk of having a short circuit external to the functional module 11, due to water infiltration for example, on this part of the electronic track between the source S and the connector BN12. Such a short circuit can indeed damage the ILW communication link and thus prevent DAT signals from passing over it.

o Protection period D3

In a nonlimiting embodiment, the electric heating device 1 also comprises a protection diode D3 associated with the main switch Q2 illustrated in FIG. 2a or 2b.

It is arranged in parallel with the main return resistor R7 (described below) and the tertiary non-return diode D6 (described below). Its anode A is connected to the source S of the main switch Q2 and its cathode K is connected to the grid of the main switch Q2.

This protection diode D3 is adapted to protect the main switch Q2 against an increase in the voltage U1 of the first power supply network G12, in particular against an excessively high voltage between its gate G and its source S.

Indeed, if a fault occurs on the first power supply network G12, the voltage U1 which it supplies can greatly increase and be found on the gate-source voltage V _G s of the main switch Q2 so that to damage. In a nonlimiting example, a fault may occur in the event of a fault in the alternator or the starter of the motor vehicle.

In a nonlimiting embodiment, the protection diode D3 is a Zener diode. The Zener diode D3 includes a threshold voltage VS3. If the voltage V _GS of the main switch Q2 becomes greater than or equal to this voltage VS3, the Zener diode clips said voltage V _GS so that it is equal to the threshold voltage VS3. Thus, in a nonlimiting example, the threshold voltage VS3 is equal to 20V. The main switch Q2 is thus protected.

o R6 resettable fusjble.autp ₇

In a nonlimiting embodiment, the electric heating device

I further comprises a self-resetting fuse R6 illustrated in FIG. 2a or 2b.

This self-resetting fuse R6 is arranged in series with the main switch Q2, in particular between said main switch Q2 and the BLW communication bus.

It is suitable for protecting the BLW communication bus against an overcurrent. An overcurrent is a current which is too strong and which said BLW communication bus cannot support.

Indeed, during the linear speed of the main switch Q2, namely during the switching phase, the main switch Q2 behaves like a resistor. However, when there is a DC short circuit which generates a USS overvoltage, there is a potential difference between the drain D (V _D = 48V) and the source S (V _s = 0V when the DAT signals are emitted). generates a current (not shown) of the order of a few amps. This current, called overcurrent, is dangerous because the BLW communication bus does not support this level of overcurrent. This can damage said BLW communication bus or cut communications between the external electronic module 2 (described below) and the functional module 11 of the electric heating device 1.

When an overcurrent is generated and crosses the self-resetting fuse R6, the latter heats up and opens, thus preventing said current from passing through the BLW communication bus.

When again, normal conditions are reached (there is no more overcurrent, the self-resetting fuse R6 closes again.

o Non-return diode.

In a nonlimiting embodiment, the electric heating device 1 also comprises a tertiary non-return diode D6 (illustrated in FIG. 2a or 2b) adapted to guarantee that the main switch Q2 remains open.

The tertiary non-return diode D6 is arranged in series with the main return resistor R7. Its anode A is connected to the gate G of the main switch Q2 and its cathode K is connected to the source S of the main switch Q2 via the main return resistor R7.

When the main switch Q2 is open, there is the source voltage V _s = 0V or 12V respectively if the DAT signals are emitted or not. When V _s = 12V, this voltage of 12V can be found on the gate voltage V _G , namely at node N4 illustrated in FIG. 2a or 2b.

If the voltage V _s returns to 0V (DAT signals are emitted), the voltage of the source V _s is found on the gate voltage V _G , but the latter does not immediately return to 0V due to the parasitic capacitances of the main switch Q2. Thus, for a very short period, V _GS can be greater than the threshold voltage Vgsth of the main switch Q2. For example we have V _G = 2.5V and V _s = 0V. This has the effect of turning on the main switch Q2. Thus, the main switch Q2 may close when it should remain open.

With the tertiary non-return diode D6, when it is blocked, this prevents the source voltage V _s from ending up on the gate voltage V _G. This guarantees that the main switch Q2 remains open. This prevents the main switch Q2 from closing when it is open.

The tertiary non-return diode D6 is blocked when the potential difference V _A k <VS6, with VS6 the threshold voltage of the tertiary non-return diode D6. In a nonlimiting example VS6 = 0.6V.

Note that the main switch Q2 opens when the secondary switch Q6 opens. When the secondary switch Q6 opens, the node N5 illustrated in FIG. 2a or 2b is at 0V and when the voltage V _s = 0V (when the DAT signals are sent) from the main switch Q2, there is the voltage at the anode A of the tertiary non-return diode D6 V _A = 0V and the voltage at the cathode K of the tertiary non-return diode D6 V _K = 0V (the cathode K being connected to the source S). This has the consequence that the tertiary non-return diode D6 is blocked.

• Functional module

The functional module 11 is connected to the first connection interface 112 and to the second connection interface I48 via respectively the connector BN12 and via the connector BN48 seen previously. It can thus be supplied by the two different voltages U1 and U2 supplied respectively by the two networks G12 and G48.

The functional module 11 is also connected to the common ground GND via the connector BN48.

An electrical node N1, called the first node, connects the functional module 11 to the first connection interface 112 via an electrical connection wire and to the third connection interface ILW via the secondary switch Q6 and the main switch Q2 described below. .

The functional module 11 comprises a DLW control module described below (called in English "electronic driver").

An electrical node N2, called the second node, connects the functional module 11, in particular its DLW control module, and the main switch Q2 via the communication line LLW.

An electrical node N3, called the third node, connects the functional module 11 and the first protection module 10 at the level of the common ground GND.

The third node N3 is thus connected to the common ground GND via said functional module 11.

In the following description, an electrical node is also called a node.

When a DC short circuit appears in the second power supply network G48 which generates a USS overvoltage, the functional module 11 rises to the potential of 48V.

This implies a USS overvoltage at the electrical nodes N1, N2 and N3 which can go up to 48V. Note that the USS overvoltage can occur on one, two, or all of these nodes N1, N2, N3.

At the first node N1, a potential difference of 48V12V appears (between the first node N1 and the first connection interface 112) which causes the appearance of the current il (illustrated in FIG. 3) flowing from the functional module 11 to the first connection interface 112 which risks damaging the first connection interface 112. The main non-return diode D8 (described below) prevents such a current there from flowing and thus protects the first connection interface 112. The latter does not is thus not damaged.

At the second node N2, on the side of the drain D of the main switch Q2 described below, a potential difference of 48V-0V or 48V12V (between the second node N2 and the third connection interface ILW) appears which causes l appearance of a current i2 (illustrated in FIG. 3) flowing from the DLW control module to the BLW communication bus (via the third connection interface ILW) which risks damaging it as well as the third connection interface ILW. The first protection module 10 described below and the main switch Q2 prevent such a current i2 from flowing and thus protect the communication bus BLW and the third connection interface ILW. The latter are thus not damaged.

At the third node N3, a potential difference of 48V12V appears (between the third node N3 and the first connection interface 112) which causes the appearance of the current i3 (illustrated in FIG. 3) flowing from the functional module 11 to the first connection interface 112 which risks damaging the first connection interface 112.

At the third node N3, a potential difference of 48V-0V between this third node N3 and the communication bus BLW (all the functional module 11 being mounted up to the potential of 48V) which results in the creation of a current i3 (illustrated in FIG. 3) between said third node N3 and said communication bus BLW. The first protection module 10 (in particular the secondary non-return diode D11) described below prevents such a current i3 from flowing and thus protects the communication bus BLW and the third connection interface ILW. The latter are thus not damaged.

In a nonlimiting embodiment, the electric heating device 1 is an additional electric heating device. In this case, the functional module 11 comprises at least one resistive heating element 110 (illustrated in FIG. 1 and 3) and at least one control element 111 (illustrated in FIG. 1 and 3) associated for controlling the current in said au minus one resistive heating element 110.

Said resistive heating element 110 is connected to the second connection interface I48 and said associated control element 111 is connected to the first connection interface 112. Thus in the nonlimiting example taken, the control element 111 is powered by the low power voltage U1 of 12V and the resistive heating element 110 is supplied by high power voltage U2 of 48V.

In a nonlimiting example, the resistive heating element 110 is a heating resistance.

In another nonlimiting example, the resistive heating element 110 is a resistive track.

In the two nonlimiting examples, the heat produced by the resistive heating element 110 is transmitted via a fluid circulation conduit (not illustrated) to said fluid which can thus be heated

Since such electric heaters are known to those skilled in the art, they are not described in detail here.

In a nonlimiting embodiment, a control element 111 comprises an electronic component such as a switch, which is in a nonlimiting example, a MOSFET. It makes it possible to control the current which feeds a resistive heating element 110. The control of the current in resistive heating elements being known to those skilled in the art, it is not described here. Conventionally, the electric heating device 1 comprises a plurality of control elements. A control element 111 cooperates with a DLW control module of the functional module 11 which sends it DAT signals. A DLW control module can control one or more control elements 111.

The DLW control module is described below.

Ο Μ Pilot.Iodule

As illustrated in FIGS. 1 to 6 in which the DLW control module is schematically illustrated, the DLW control module comprises a switch Q8 in series with a pulling resistance R8. It is connected to the main switch Q2 of the electric heater 1.

The DLW control module is described below with reference to FIGS. 5 and 6 in its operating mode when:

- there is no short circuit in the second G48 power supply network and therefore when there is no USS overvoltage;

- the GND common ground is not lost.

For simplicity, the operating mode is described with a bidirectional BLW communication bus.

The DLW control module is adapted to be supplied with voltage by the first G12 power supply network. It is thus connected to the first power supply network G12 and to the common ground GND via the functional module 11. It is connected to the first network G12 via its pulling resistor R8 and to the common ground GND via its switch Q8.

The DLW control module is suitable for receiving and / or transmitting DAT signals via the BLW communication bus. It transmits the received DAT signals to the control element 111 of the functional module 11, said control element 111 interpreting these DAT signals so as to control the resistive heating elements 110.

In a nonlimiting embodiment, said electric heating device 1 is adapted to operate in slave mode, it forms a slave module. As illustrated in Figures 5 and 6, the DLW control module is suitable for receiving and transmitting DAT signals on the BLW communication bus to and from an external electronic device 2 called the master module.

In a nonlimiting embodiment, the DAT signals are low logic signals. In a nonlimiting example, the low logic DAT signals are 0V signals. It will be noted that in the case of the LIN protocol, the signals of low logic are so-called dominant signals.

When the switch Q8 is open (Figure 5), the draw resistor R8 brings the drain D of the main switch Q2 of the slave module 1 to 12V. When the switch Q8 is closed (Figure 6), the switch brings the drain D of the main switch Q2 of the slave module 1 to common ground GND.

The external electronic device 2 operates in master mode and includes a switch Q9 and a pull-up resistor R9. The master module 2 is supplied with a low power voltage.

The master module 2 is connected to the second power supply network G12 via its pulling resistor R9 and to the common ground GND via its switch Q9.

When the switch Q9 is open (Figure 6), the pull-up resistor R9 brings the communication bus BLW to 12V, which causes the source S of the main switch Q2 of the slave module 1 to be 12V. When the switch Q9 is closed (Figure 5), the switch brings the BLW communication bus to ground, which causes the source S of the switch Q2 of the slave module 1 to be OV.

It will be noted that by default (namely when the electric heating device 1 is powered or not) the switches Q8 and Q9 are open. This therefore corresponds to their initial state. The LIN protocol and master-slave operation prevents them from closing at the same time. Note that for the PWM protocol which is unidirectional, it is not possible to have such collisions.

A slave module 1 and the master module 2 form an NLW communication network. In a nonlimiting embodiment, the communication network NLW can comprise a plurality of slave modules 1. In a nonlimiting embodiment, the switches Q8 and Q9 are NPN switches.

In a nonlimiting embodiment, the master module 2 is the engine control ECU of the motor vehicle or even an electronic device connected to the dashboard of the motor vehicle.

In this case, the DAT signals are in a nonlimiting example:

- heating power setpoints sent from the master module 2 to the electric heating device 1; and

- diagnostic information sent to the master module 2 by the electric heating device 1. In nonlimiting examples, this information indicates short circuits, overvoltages, undervoltages, over-temperatures, faulty equipment, consumption electric heater 1 etc.

As illustrated in FIGS. 5 and 6, the master module 2 is supplied with a voltage of 12V in the nonlimiting example taken illustrated in FIGS. 5 and 6.

FIG. 5 illustrates the sending of DAT signals from the master module 2 to the electric heating device 1 and FIG. 6 illustrates the sending of DAT signals from the electric heating device 1 to the master module 2.

When the master module 2 communicates with the slave module 1, it sends DAT signals to it. For this purpose, the switch Q9 switches so that OV (corresponding to logic signal 0) or 12V (corresponding to logic signal 1) signals are sent on the BLW communication bus to slave module 1. When the switch Q9 closes, a logic signal 0 is sent, when switch Q9 opens, a logic signal 1 is sent. The Q8 switch is always open to him.

When the slave module 1 responds to the master module 2, the switch Q8 switches so that 0V (corresponding to a logic signal 0) or 12V (corresponding to a logic signal 1) signals are sent on the BLW communication bus to the master module 2. When switch Q8 closes, a logic signal 0 is sent, when switch Q9 opens, a logic signal 1 is sent. Switch Q9 is always open to him.

Thus, as illustrated in FIG. 5, when the master module 2 sends DAT signals to the electric heater 1, it imposes a zero on the communication bus BLW (in the case where the DAT signals are of low logic) , the latter then being at ground potential GND. To this end, he closes his switch Q9. On the source S, there is therefore 0V and on the grid 12V (since the main switch Q2 receives on its grid G 12V from the first connection interface 112). The voltage Vgs of the main switch Q2 is therefore equal to 12V (and therefore greater than a threshold voltage Vgsth) which causes said main switch Q2 to be closed. DAT signals therefore arrive at the input of the DLW control module.

As illustrated in FIG. 6, when the slave module, here the electric heating device 1, sends DAT signals to the master module 2, it imposes a zero (in the case where the DAT signals are of low logic) on the drain D of the main switch Q2. To this end, the slave module 1 closes its switch Q8. Switch Q8 is closed, drain D is at ground potential GND, i.e. at 0V.

It will be noted that the NLW communication network comprises a master module 2 and can comprise a plurality of slave modules 1 of which at least one slave module is supplied by the first electrical supply network G12 and the second electrical supply network G48. The other slave modules 1 can be supplied in the same way or only by the first power supply network G12.

It will be noted that the communication bus BLW makes it possible to route DAT signals from the master module 2 to all of the slave modules 1. Thus, if a DC short circuit occurs which generates an overvoltage USS on the electric heating device 1 described above which is a slave module, it disconnects from the NLW communication network thanks to the first protection module 10, but the master module 2 and the other slave modules 1 continue to operate without being disturbed by the faulty slave module (the one which suffered a surge). The NLW communication network is thus protected from a USS overvoltage on one of its slave modules 1.

Thus, by protecting the BLW communication bus, the other slave modules 1 which have not undergone a USS overvoltage are also protected.

Thus, the first protection module 10 prevents:

- destruction of the other slave modules 1; or

- the disturbance of the communication between the other slave modules and the master module 2.

o Road diode .free D2

It will be noted that as illustrated in FIGS. 5 and 6, in a nonlimiting embodiment, the main switch Q2 comprises a freewheeling diode D2 (called in English "body diode").

The freewheeling diode D2 is adapted to guarantee the closing of the main switch Q2.

The freewheeling diode D2 is disposed between the drain D and the source S of the main switch Q2.

When the drain D is at 0V, the freewheeling diode D2 becomes on.

Recall that a freewheeling diode is conducting when the voltage V _A k equal to the potential difference between V _A its anode A and V _k its cathode K is greater than a threshold voltage VS2 (given by the manufacturer). In a nonlimiting example, VS2 = 0.6V.

Thus, when the drain D is at 0V, the voltage V _k is at 0V. Furthermore, V _A is at 12V since before the switch Q8 closes, the source of the main switch Q2 was at 12V (thanks to the pulling resistor R9 seen previously). Thus, we have V _AK which is equal to 12V, ie greater than 0.6V. The freewheeling diode D2 when passing imposes 0.6V on the source S of the main switch Q2, and increases the voltage Vgs from OV (when Q2 is open, Vgs = 0V) to 11.4V (12V- 0.6V). This voltage value Vgs is sufficient for the main switch 02 to close. When it closes, it connects its drain voltage D to its source S so that Vds is substantially equal to OV (except for a parasitic resistance Rdson) and the voltage Vgs is substantially equal to 12V. Thus the DAT to OV signals arrive at the input of the master module 2.

The freewheeling diode D2 thus makes it possible to correctly close the main switch 02. Otherwise, the source S would remain at the potential of 12V and the grid being at 12V, we would have Vgs <Vgsth and said main switch 02 would remain open. It is recalled that in a nonlimiting example, Vgsth = 2V.

Note that when the main switch Q2 is open (blocked state) (for example during a USS overvoltage or a common GND mass loss as described below), it is not controlled and we have Vgs <Vgsth or Vgs = 0V in a nonlimiting example and V _AK + OV (V _KA k can go up to 48V) and the freewheeling diode D2 returns to a blocked state. It will be noted that the freewheeling diode D2 is not destroyed by this high voltage since the breakdown voltage of the main switch Q2 is greater than 48V.

Note that if there is no USS overvoltage, and when the switches Q8 and Q9 are open (by default), the gate G and the source S of the main switch Q2 are at 12V, we have V _gs = 0V. The main switch Q2 is then open. Similarly, if the common GND ground is correctly connected and the switches Q8 and Q9 are open (by default), the gate G and the source S of the main switch Q2 are at 12V, we have V _gs = 0V. The main switch Q2 is then open.

• Non-return period, main D8

In a nonlimiting embodiment, the electric heating device

I includes a main non-return diode D8.

The main non-return diode D8 is adapted to prevent a current from flowing to the first power supply network G12 when the main switch Q2 is open. It protects the secondary switch Q6 during a DC short circuit.

The main non-return diode D8 is disposed between the functional module 11 and the first connection interface 112, and in particular between the first electrical node N1 and the first connection interface 112. More particularly, its cathode K is connected to the functional module 11 and its anode A is connected to the first connection interface 112.

When there is a DC short circuit which generates a USS overvoltage, the first node N1 goes up to the potential of 48V.

There is thus a potential difference between the first node N1 and the first connection interface 112 which results in the creation of a current il (illustrated in FIG. 3) between said first node N1 and said first connection interface 112. Indeed , in this case, the first node N1 is at the potential of 48V (all the functional module 11 being mounted up to the potential of 48V) while the first connection interface 112 is at the potential of 12V since connected to the first network G12 of 12V.

The main non-return diode D8 is adapted to prevent such a current il from flowing from the second power supply network G48 via the first node N1 to the first power supply network G12 via the first connection interface 112.

The main non-return diode D8 prevents current there from flowing when it is in a blocked state.

The main non-return diode D8 is in a blocked state when the voltage V _A k which is equal to the potential difference V _A at its anode A and V _K at its cathode K is less than its threshold voltage VS8 (given by the maker). In a nonlimiting example, VS8 = 0.6V. There is such a difference when there is a DC short circuit which generates a USS overvoltage on node N1. Indeed, in this case, we have V _A = 12V (since connected to 112) and V _K = 48V (the first node N1 being at the potential of 48V). We therefore have V _A k negative and therefore V _AK <VS8.

Thus, the first connection interface 112 is protected against any DC short circuit coming from the second network G48 and therefore against any USS overvoltage.

It will be noted that the main non-return diode D8 is conducting when V _A k> VS8. This is obtained when there is no DC short circuit and therefore USS overvoltage on the first node N1. Indeed, in this case, we have V _A = 12V (since connected to 112) and V _k = 12-0.6V, which gives V _A k> VS8.

The same reasoning applies when the GND mass is lost. Indeed, when the common ground GND is lost as illustrated in FIG. 4, the ground cable CX having been cut, the first node N1 becomes floating, because it is no longer connected to the common ground GND. So it goes up to the 48V potential.

It will be noted that the voltage V _A k is less than the threshold voltage VS8 (D8 is blocked) when the common ground GND is lost. Indeed, in this case, we have V _A = 12V and V _K = 48V (the first node N1 being at the potential of 48V). We therefore have V _A k negative and therefore V _A k <VS8.

Furthermore, V _A k> VS8 (D8 is on) when the common ground GND is not lost. Indeed, in this case, we have V _A = 12V and V _k = 12-0.6V.

It will be noted that the main non-return diode D8 also makes it possible to protect the battery connected to the first network G12 against a rise in potential. In fact, in this main non-return diode D8, in the event of a USS overvoltage or common mass loss, the 48V potential is likely to be found on the 12V battery, which would damage not only said battery, but also the other electronic elements of the motor vehicle which are powered by said battery.

• E remier mod u le de. protection .10

The first protection module 10 is illustrated in detail in Figure 2a.

The first protection module 10 is adapted to isolate the first power supply network G12 and the communication bus BLW from the second power supply network G48 when there is a USS overvoltage between the functional module 11 and the first connection interface 112 and the third ILW connection interface.

Such a USS overvoltage is found on the first node N1, on the second node N2 and on the third node N3.

It is recalled that an overvoltage USS exists when the voltage between the functional module 11 and the first and third connection interfaces 112, ILW is greater than the voltage U1 supplied by the first supply network G12.

In a nonlimiting embodiment, the first protection module 10 comprises:

- an overvoltage detection module 100 comprising a microcontroller MC suitable for:

- detecting a USS overvoltage between the functional module 11 and the third connection interface ILW and / or between the functional module 11 and the first connection interface 112;

- Open said second protection switch 04 following said detection;

- a secondary switch 06 adapted to open when there is such a USS overvoltage so as to open the main power switch Q2;

- said second protection switch 04 adapted to open so as to open the secondary switch 06.

In order to open the second protection switch Q4, the microcontroller MC is adapted to send it an opening instruction C1.

The various elements of the protection module 10 are described in detail below.

o Surge sensing module. 100 The overvoltage detection module 100 is illustrated in detail in FIG. 2a.

Microcg.ntrô.leur.MÇ

The microcontroller MC is illustrated in detail in FIGS. 2a and 2b.

In a nonlimiting embodiment, the microcontroller MC comprises:

- A first input E1 adapted to measure the first voltage U1 between the functional module 11 and the first connection interface I2, more particularly between the functional module 11 and the secondary switch Q6;

- an output S1 adapted to control the opening of the second protection switch Q4;

- a second input E2 adapted to measure a voltage U10 between the functional module 11 and the third connection interface ILW, more particularly between the functional module 11 and the secondary switch Q2.

To this end:

- the first input E1 is connected to the node N1 between the secondary switch Q6 (described below) and the functional module 11;

- the second input E2 is connected to the communication line LLW, via a sixth node N6;

- the output S1 is connected to the base B of the second protection switch Q4 (described below);

The MC microcontroller thus detects:

- if the first voltage U1 on node N1 is greater than a limit voltage Uth. In this case, said first voltage U1 becomes dangerous for the main switch Q2 (when the secondary switch Q6 is closed, the latter being closed by default). It’s a USS surge; and or

- if the voltage U10 on the node N2 is greater than a limit voltage Uth. In this case, the voltage U10 becomes dangerous for the main switch Q2.

Thus, the voltages U1 / U10 become dangerous for the third connection interface ILW and for the communication bus. It’s a USS surge.

In a nonlimiting example, the limit voltage Uth is substantially equal to 22V.

In a nonlimiting embodiment, in order to measure the voltages U1 or U10, the microcontroller MC comprises an analog-to-digital converter or a hysteresis comparator.

When the microcontroller MC detects a DC short circuit and therefore a USS overvoltage, it sends an opening instruction C1 on the base B of the second protection switch Q4. It therefore activates its output S1. To this end, the output S1 is grounded. The microcontroller MC thus controls the second protection switch Q4.

On receipt of the opening instruction C1, the second protection switch Q4 therefore opens. It is no longer driven by the resistor R3 (described below). Its opening cascadely opens the secondary switch Q6 and the main switch Q2 as described later in the description. This protects the third ILW communication interface and the BLW communication bus against any USS overvoltage.

It will be noted that the voltage U1 / U10 which has exceeded the limit voltage Uth may again become lower than the limit voltage Uth during a temporary fault (which caused said USS overvoltage) in the functional module 11.

In a nonlimiting embodiment, the microcontroller MC is adapted to close the second protection switch Q4. To this end, in a nonlimiting embodiment, the microcontroller MC is adapted to send it a closing instruction C2.

When the voltage U1 / U10 which has exceeded the limit voltage Uth again becomes lower than the limit voltage Uth, the microcontroller MC sends a closing instruction C2 to the second protection switch Q4 via the output S1. It therefore activates its output S1. For this purpose, the output S1 is put in floating state. Resistor R3 will thus allow the second protection switch Q4 to be controlled. On receipt of said closing instruction C2, the second protection switch Q4 closes. Closing it creates a current between the emitter E and the base B (reverse of the current referenced ib6 in Figures 2a and 2b) of the secondary switch Q6 which closes. The closing of the secondary switch Q6 which brings back the voltage U1 of 12V on the grid G of the main switch Q2. The latter therefore closes. The DAT signals can be transmitted again on the LLW communication line.

For this purpose, as illustrated in the flowchart of Figure 7, when there is no USS overvoltage, the main switch Q2 is closed (illustrated Q2_ST1). DAT signals sent by the external electronic device 2 are received by the electric heater 1 (illustrated function RX (1, 2, DAT)).

If there is a USS overvoltage due to a short circuit for example, the first voltage U1 or the voltage U10 are higher than the limit voltage Uth and the following operations are carried out as illustrated in FIG. 7.

- If the voltage measured U1 / U10 by the microcontroller MC is greater than the limit voltage Uth (branch Y), the microcontroller MC transmits an opening instruction C1 to the second protection switch Q4 (illustrated function TX (MC, Q4, C1 )). The latter opens (illustrated Q4_ST2) and opens the main switch Q2 (illustrated Q2_ST2).

- If the measured voltage U1 / U10 is always higher than the limit voltage Uth, the microcontroller MC takes no action and the second protection switch Q4 remains open as well as the secondary switch Q6 and the main switch Q2.

- Otherwise, if the voltage U1 / U10 measured is or becomes lower than the limit voltage Uth (branch N), the microcontroller MC transmits a closing instruction C2 to the second protection switch Q4 (illustrated function TX (MC, Q4 , C2) which closes (illustrated Q4_ST1) causing the secondary switch Q6 (illustrated Q6_ST1) and the main switch Q2 (illustrated Q2_ST1) to close in cascade. The main switch Q2 can again transmit or receive signals DAT to or from the external electronic device 2 (illustrated function TX (1,2, DAT)).

o .Second .int.err.upte.ur.de. protection Q4 The second protection switch Q4 is suitable for opening:

- during a USS overvoltage; or

- when the GND common ground is lost so as to open the secondary switch Q6.

The second protection switch Q4 is connected to the first power supply network G12 via the resistor R3.

The resistor R3 is thus adapted to drive the second protection switch Q4. The resistor R3 is adapted to limit a current which could flow between the first power supply network G12 and the base B of the second protection switch Q4. Indeed, in this case, without resistance R3, between the first power supply network G12 and the common ground GND, there would be a short circuit which would generate a current in the second protection switch Q4 of a few thousand amps. Said second protection switch Q4 could not withstand such a strong current. Resistor R3 thus protects said second protection switch Q4 by limiting the current flowing in its base B, referenced Ib4. The resistor R3 is thus dimensioned to have a base current Ib4 B adapted to the second protection switch Q4. Resistor R3 is a so-called “pull-up” resistor. In another nonlimiting embodiment, the function of the resistor R3 can be integrated into the microcontroller MC. Thus, the microcontroller MC includes a "pull-up" resistor integrated at its output S1.

The second protection switch Q4 is arranged between the functional module 11 and the secondary switch Q6. It is connected to the microcontroller MC as seen previously.

In a nonlimiting embodiment, the second protection switch Q4 is a bipolar transistor. In a nonlimiting variant, the bipolar transistor Q4 is of the NPN type. Its collector C is connected to the base resistor R14 (described below), its emitter E is connected to the common ground GND (via the secondary non-return diode D11 described below), its base B is connected to the microcontroller MC, more particularly at its output S1. In this way it can be controlled during opening and closing by said microcontroller MC.

The third node N3 connects in particular the functional module 11 and the second protection switch Q4.

The second protection switch Q4 is closed by default. When closed, the second protection switch Q4 is controlled by the resistor R3. The second protection switch Q4 further includes an internal return resistor (illustrated but not referenced) located between its base B and its emitter E and an internal return resistor located between the resistor R3 and its base B. These internal return resistors with the resistor R3 allow the first voltage U1, namely 12V, to be applied to the emitter E of the second protection switch Q4.

Using internal recall resistors saves space.

The second protection switch Q4 opens when the MC microcontroller has detected a USS overvoltage as seen above.

When there is a DC short circuit, as seen previously, a USS overvoltage (whether on node N1 or on node N2) is detected by the overvoltage detection module 100 (in particular the microcontroller MC via respectively its two inputs E1 and E2), which results in the sending to the second protection switch Q4 of an opening instruction C1 following this detection, via the output S1 of the microcontroller MC. At this time, the second protection switch Q4 opens.

The opening of the second protection switch Q4 causes the base resistor R14 (described below) to be disconnected from the common ground GND. The base B of the secondary switch Q6 is no longer connected to the common ground GND, it becomes floating. The 12V potential is therefore installed. In fact, thanks to the secondary return resistor R15 (described below), the base B of the secondary switch Q6 rises to 12V. We then obtain a potential difference between the emitter E and the base B which is zero V _B e = 0 (the emitter E of the secondary switch Q6 being at the potential of 12V), which has the consequence of opening the secondary switch Q6.

Thus, when the second protection switch Q4 opens, it causes the opening of the secondary switch Q6, and therefore the opening of Q2 (as described below) so that the first power supply network G12 and the BLW communication bus are disconnected from the second power supply network G48. They will no longer be disturbed by a DC short circuit and therefore by a USS overvoltage.

During the GND common ground loss, the emitter E of the second protection switch Q4 is floating. In this case, no current can pass through the transmitter E. The current ie4 (not shown) in the transmitter E is therefore zero. As we have ie4 = ib4 + ic4 and that ib4 and ic4 (not illustrated) cannot be negative therefore ib4 = 0, the second protection switch Q4 therefore opens. The opening of the second protection switch Q4 causes the opening of the secondary switch Q6, the latter causing the opening of the main switch Q2 as described below.

o the secondary switch Q6 The secondary switch Q6 is suitable for opening:

- during a USS overvoltage; or

- when the GND common ground is lost so as to open the main switch Q2.

The secondary switch Q6 is closed by default.

In a nonlimiting embodiment, the secondary switch Q6 is a bipolar transistor. In a nonlimiting variant, the bipolar transistor Q6 is of the PNP type. Its base B is connected to the collector C of the second protection switch Q4, its transmitter E is connected to the first network G12, and its collector C is connected to the gate G of the main switch Q2.

When a DC short circuit occurs which generates a USS overvoltage, the base B of the secondary switch Q6 is in open circuit, the second protection switch Q4 having been opened by the microcontroller MC. Base B is floating, because it is no longer connected to GND common ground. We then have the base current Ib6 (current flowing in base B of the secondary switch Q6) equal to 0, which causes the latter to open. He is said to be in a blocked state.

When a DC short circuit occurs which generates a USS overvoltage, the second node N2 rises to the potential 48V and a potential difference, here of 48V-0V (DAT signals are emitted) thus appears on the second node N2 and on the module DLW control, which generates the current i2 which flows on the BLW communication bus via the main switch Q2 if the latter is closed and if DAT signals flow on the BLW communication bus, said DAT signals being at 0V as described previously. The DLW control module and the BLW communication bus do not support such an i2 current and therefore risk being damaged. The secondary switch Q6 (which opened as seen previously following the detection of the USS overvoltage by the microcontroller MC) makes it possible to open the main switch Q2 and thus prevents such a current i2 from flowing in the communication bus BLW (via the third ILW connection interface). The latter is thus protected as well as the third ILW connection interface.

When the secondary switch Q6 opens, the main switch Q2, in particular its gate G (connected to the collector C of the secondary switch Q6) in the non-limiting example of the MOSFET, is no longer supplied by the voltage U1, namely 12V, and therefore the potential of the gate G is equal to 0V. Indeed, the tertiary non-return diode D6 prevents the main return resistor R7 from letting a voltage pass from the source S to the gate G.

As the source S of the main switch Q2 is either at the potential of 12V or at the potential of 0V depending on the switching of the switches Q8, Q9 described above, we have V _G s = -12V or V _GS = 0V, which does not allow the main switch Q2 to be closed, because V _GS is less than the threshold voltage Vgsth of the main switch Q2 which is 2V in a nonlimiting example. The main switch Q2 therefore opens.

Thus, there is no longer any difference in potential at the level of the DLW control module, and therefore of current i2 which flows on the BLW communication bus. The third ILW connection interface and the BLW communication bus are thus protected. By opening the main switch Q2 during a DC short circuit and therefore during a USS overvoltage, we thus disconnected the second network G48 from the BLW communication bus.

During a GND common ground loss, the second protection switch Q4 opens as seen previously, which causes the opening of the secondary switch Q6, it is in a blocked state. When the secondary switch Q6 opens, this opens the main switch Q2. By opening the main switch Q2 during the GND common ground loss, the second network G48 was disconnected from the BLW communication bus.

• Résjstance.deTappel.pnncjpale.R7

In a nonlimiting embodiment, the electric heating device 1 also comprises a main return resistor R7.

The return resistor R7 is adapted to guarantee the opening of the main switch Q2 when said main switch Q2 must open (during a USS overvoltage or during a common GND mass loss).

The main restoring resistor R7 is connected to the cathode K of the tertiary non-return diode D6 and to the source S of the MOSFET transistor Q2.

It is recalled that a return resistor makes it possible to initialize the state of the grid

G of a switch.

By default, the level of control applied (namely the value of the voltage applied) to the gate G of the main switch Q2 is undefined (the gate sees neither 12V nor 0V voltage). It is in a floating state, and could force it to enter conduction, either completely (with risk of erratic operation of the electric heating device 1), or partially (with risk of destruction of the main switch Q2).

When the electric heating device 1 is supplied, and there is no fault such as a DC short-circuit or a common ground loss GND, the potential of the gate G of the main switch Q2 is of 12V, because the secondary switch Q6 is closed. When the secondary switch Q6 is closed, the node N4 (as well as the node N5) illustrated in FIG. 2a is at the potential of the voltage U1, namely 12V in the example.

When the secondary switch Q6 opens (due to a USS overvoltage or GND common ground loss), the main switch Q2 opens. The node N4 corresponds to the gate voltage V _G of the main switch Q2. The node N4 (as well as the node N5) becomes floating. There is therefore a potential difference between the source S (which is at 0V due to the DAT signals) of the main switch Q2 and the node N4, ie the gate G of the main switch Q2. This potential difference generates a current (not illustrated) which will flow in the tertiary non-return diode D6 and the main return resistor R7 and will go to the source S and the self-resetting fuse R6. The node N4 (as well as the node N5) will thus descend to the 0V potential of the source S. The return resistor R7 allows the node N4 and therefore the gate G of the main switch Q2 to be at 0V quickly . We will thus have the voltage Vgs at 0V which guarantees the opening of the main switch Q2. The main booster resistor R7 is a so-called “pull-up” resistor.

• Résjstance.deTappel.seçondaire.R15 In a nonlimiting embodiment, the electric heating device 1 also comprises a secondary return resistor R15.

The secondary return resistor R15 is adapted to guarantee the opening of the secondary switch Q6 when said secondary switch Q6 must open (during a USS overvoltage or during a common GND mass loss).

The secondary booster resistor R15 is connected to the base B and to the emitter E of the bipolar transistor Q6.

The secondary return resistor R15 makes it possible to control the secondary switch Q6 on opening when its base B is floating, namely when the second protection switch Q4 opens as described above.

Indeed, this secondary return resistor R15 makes it possible to initialize the voltage V _B e of the secondary switch Q6 at 0V (it is therefore by default at 0V) which guarantees the opening of the secondary switch Q6 when it there is no current Ib6 flowing in the base B of said secondary switch Q6.

The secondary booster resistor R15 is a so-called “pullup” resistor.

• Secondary anti-return diode.D11

In a nonlimiting embodiment, the first protection module 10 further comprises a secondary non-return diode D11.

The secondary non-return diode D11 is adapted to prevent a current i3 from flowing in the second protection switch Q4. It thus protects the second protection switch Q4 during a DC short circuit.

The secondary non-return diode D11 is disposed between the functional module 11 and the second protection switch Q4. The third node N3 thus links in particular the functional module 11 and the secondary non-return diode D11. The secondary non-return diode D11 is connected to the common ground GND via the functional module 11.

In particular, the anode A of the secondary non-return diode D11 is connected to the emitter E of the second protection switch Q4, and its cathode K is connected to the common ground GND.

When there is a DC short circuit which generates a USS overvoltage, from the point of view of the emitter E of the second protection switch Q4, the node N3 rises to the potential of 48V (all the functional module 11 being mounted up to 'at the potential of 48V), i.e. the transmitter E is found at 48V. Consequently, there is therefore a potential difference of 48V-12V between the emitter E of the second protection switch 04 and its base B, the latter being at 12V (04 being closed by default). This therefore generates a current I3 which is found on the emitter E of the second protection switch 04 and is too large for the second protection switch 04.

The second protection switch 04 may then break. Consequently, the protection of the main switch 02 is no longer ensured.

It is the same when the common mass GND is lost.

The secondary non-return diode D11 is adapted to prevent such a current i3 from flowing in the second protection switch Q4. It thus protects said second protection switch Q4.

The secondary non-return diode D11 prevents the current i3 from flowing when it is in a blocked state.

For this purpose, the secondary non-return diode D11 is in a blocked state when the voltage V _A k equal to the potential difference V _A at its anode A and V _K at its cathode K is less than its threshold voltage VS11 (given by the manufacturer). In a nonlimiting example, VS11 = 0.6V. There is such a difference when there is a USS overvoltage. Indeed, in this case, we have V _A = 12V (the voltage 12V being applied to the emitter E of the second protection switch Q4 via the resistor R3 and its internal return resistor located between its base B and its emitter E, transmitter E connected to the anode A of the secondary non-return diode D11) and V _K = 48V (the third node N3 being mounted up to the potential of 48V). We therefore have V _AK negative <VS11.

When the secondary non-return diode D11 is blocked, there is no potential difference across the second protection switch Q4. We indeed have V _E = 12V (the 12V voltage being applied via the resistor R3) and its internal return resistance located between its base B and its emitter E) and V _b = 12V (the node N7 is at 12V thanks to the resistance R3). We get V _E b = OV. It will be noted that it is the same when the common mass GND is lost.

It will be noted that the secondary non-return diode D11 is conducting when V _A k> Vs. This is obtained when there is no short circuit. Indeed, in this case, we have V _A at the potential 12V and V _k at the ground potential.

Note that it is the same when the GND common ground is not lost.

• Basic resistance R14

In a nonlimiting embodiment, the electric heating device 1 also comprises a basic resistance R14.

The base resistor R14 is suitable for dimensioning the base current Ib6 which flows in the secondary switch Q6.

The basic resistor R14 is placed between the secondary switch Q6 and the second protection switch Q4.

In particular, the base resistor R14 is connected to the base B of the secondary switch Q6 and to the collector C of the second protection switch Q4.

The basic resistance R14 makes it possible to control the secondary switch Q6 at closing thanks to the basic current Ib6 which it provides.

Indeed, the dimensioning of the basic current Ib6 makes it possible to guarantee the closing of the secondary switch Q6. In addition, this avoids having an excessive Ib6 current which could break the Q6 component.

Recall that the threshold value of Ib6 for the secondary switch Q6 to close is Ib6> lc / β, with the collector current and β the current amplification of the switch given by the manufacturer of the switch.

• DI2protectjpn.additional diode

In a nonlimiting embodiment, the electric heating device 1 also comprises an additional protective diode D12.

The additional protection diode D12 to protect the secondary switch Q6 against a voltage reversal U1.

The additional protective diode D12 is disposed between the secondary switch Q6 and the first network G12.

If a user makes an error when he connects the battery connected to the first network G12, for example by reversing the + and - terminals of the battery, the additional protection diode D12 is blocked. This thus avoids having a voltage V _B e of the secondary switch equal to - 12V which would cause overheating of said secondary switch 06 and therefore which would risk damaging it.

• .Second protection module 20

The second protection module 20 is illustrated in detail in FIG. 2b.

The second protection module 20 is adapted to isolate the first electrical network G12 and the communication bus BLW from the second electrical supply network G48 during a loss of the common ground GND.

The GND common ground is lost when the ground connection cable CX which connects the first and second connection interfaces 112 and I48 to the GND common ground is cut off as illustrated in FIG. 4.

The second protection module 20 is part of the first protection module 10. In fact, it comprises:

- the secondary switch 06 described above;

- the second protection switch 04 described above;

- the secondary non-return diode D11 described above;

- the secondary return resistor R15 described above;

- the basic resistance R14 described above.

In a nonlimiting embodiment, the second protection module 20 further comprises the main return resistor R7.

It will be noted that the microcontroller MC is not part of the second protection module 20. Thus, it does not intervene to solve the GND common mass loss problem.

When the common ground GND is lost, all of the components of the functional module 11 rise to the potential of the voltage supplied by the second power supply network G48. This results in the appearance of potential differences and therefore of currents flowing between said functional module 11 and:

- the first connection interface 112;

- the second protection module 20;

- the BLW communication bus.

These currents risk damaging in particular the first connection interface 112 and the BLW communication bus. The second protection module 20 protects these elements against said currents as follows.

When the GND common ground is lost, the functional module 11 rises to the potential of 48V. The electrical nodes N1, N2 and N3 become floating, because they are no longer referenced to the common ground. They then go up to the potential of 48V.

At the first node N1, a potential difference of 48V12V appears (between the first node N1 and the first connection interface 112) which causes the appearance of the current il (illustrated in FIG. 4) flowing from the functional module 11 to the first connection interface 112 which risks damaging it. The second protection switch Q4 cascaded opens the secondary switch Q6 and the main switch Q2 (as described above) which allows the secondary switch Q6 to prevent such a current from flowing.

At the second node N2, on the drain D side of the main switch Q2, a potential difference of 48V-0V (between the second node N2 and the communication bus BLW) appears which causes the appearance of a current i2 (illustrated in Figure 4) flowing from the DLW control module to the BLW communication bus (via the third ILW connection interface) which risks damaging them. The second protection switch Q4 cascade opens the secondary switch Q6 and the main switch Q2 (as described above) which allows the main switch Q2 to prevent such current i2 from flowing (as described above) in the BLW communication bus. The latter is thus protected as well as the third ILW connection interface.

In addition, when the GND common ground is lost, the DLW control module is no longer referenced to the ground. It goes up to the potential of 48V (all the functional module 11 is mounted up to the potential of 48V). Without the second protection module 20, the DLW control module would see at its terminals a potential difference of 48V-0V which corresponds to the difference between the potential of 48V (applied to the functional module 11) and the potential of 0V of the signals DAT transmitted on the BLW communication bus. This potential difference causes the appearance of a current i2 (illustrated in FIG. 4) which circulates in said DLW control module which would risk damaging it. Indeed, the DLW control module does not support such a large potential difference. In a nonlimiting example, it supports a potential difference less than or equal to 24V. The second protection switch 04 cascade opens the secondary switch 06 and the main switch 02 (as described above) which allows the main switch 02 to prevent the current i2 from flowing when the common ground GND is lost, there will no longer be a potential difference across the terminals of the DLW control module and therefore no more current flowing i2. The DLW control module will only be at 48V potential. It will not be damaged.

Thus, unlike a DC short-circuit which occurs in the functional module 11 where the DLW control module will surely be defective, or even destroyed, said DLW control module will be protected in the event of loss of common GND mass. Thus, the DLW control module is not protected by the first protection module 10 against a DC short circuit, but it is protected by the second protection module 20.

At the third node N3, a potential difference of 48V0V between this third node N3 and the communication bus BLW (all the functional module 11 being mounted up to the potential of 48V) which results in the creation of a current i3 (illustrated in FIG. 4) between said third node N3 and said communication bus BLW. Indeed, in this case, the third node N3 rises to the potential of 48V while the communication bus BLW is at the potential of 0V due to the DAT signals at 0V. During a GND common ground loss, the second protection switch Q4 opens as seen previously. It thus prevents such a current i3 from flowing and thus protects the first connection interface 112 and the communication bus BLW as well as the third connection interface ILW.

It will be noted that with the first protection module 10, a USS overvoltage detection is transformed into a detection of the loss of the common ground GND. Common components are used to protect the first connection interface 112 and the third connection interface ILW (and therefore the communication bus BLW) against the loss of the common ground GND and against said overvoltage USS. In fact, on detection of a USS overvoltage, the second protection switch Q4 opens, which has the consequence that the basic resistance R14 disconnects from the common ground GND as seen previously, which corresponds to a loss of the GND common ground. After the detection of a USS overvoltage, the continuation of the operation of the protection against a USS overvoltage or against a loss of GND mass is the same for the first protection module 10 and for the second protection module 20 as seen previously.

Of course, the description of the invention is not limited to the embodiments described above.

Thus, in another nonlimiting embodiment, the secondary switch Q6 can be a MOSFET transistor or an IGBT transistor. In these cases, the basic resistance R14 is not necessary.

Thus, in another nonlimiting embodiment, the first connection interface 112 and the second connection interface I48 are connected to two different masses. In this case, there is no second protection module 20.

Thus, bidirectional or unidirectional protocols other than the LIN or PWM protocol can be used.

Thus, the invention can also be applied to an air blower 1 for a motor vehicle. Thus, in a nonlimiting embodiment, the air blower 1 for a motor vehicle is adapted to be supplied with voltage by a first electrical supply network G12 and by a second electrical supply network G48. Air blower 1 includes:

a first connection interface 112 with the first power supply network G12;

- a second connection interface I48 with the second power supply network G48;

- a third ILW connection interface with a BLW communication bus;

a functional module 11 connected to the first connection interface 112 and to the second connection interface I48;

- a main switch Q2 connected to the functional module 11 adapted to pass DAT signals on the BLW communication bus;

a first protection module 10 adapted to isolate the first power supply network G12 and the communication bus BLW from the second power supply network G48 when there is a USS overvoltage between the functional module 11 and the first connection interface 112 and the third connection interface ILW, said first protection module 10 comprising:

- an overvoltage detection module 100 comprising a microcontroller MC suitable for:

- detecting a USS overvoltage between the functional module 11 and the third connection interface ILW and / or between the functional module 11 and the first connection interface 112;

- open a second protection switch Q4 following said detection;

- a secondary switch Q6 adapted to open when there is said USS overvoltage so as to open the main switch Q2;

- said second protection switch Q4 adapted to open so as to open the secondary switch Q6.

In this case, the functional module 11 comprises at least one driving load 110 and at least one driving element 111 associated for driving the current in said at least one driving load 110. Said driving load 110 is connected to the second connection interface I48 and the control element 111 is connected to the first connection interface 112. Thus in the nonlimiting example taken, the control element 111 is supplied by the low power voltage U1 of 12V and said drive load 110 is supplied by the high power U2 voltage of 48V. Said motive load 110 makes it possible to turn the motor of the air blower 1.

Note that an air blower 1 includes:

- an electric motor adapted to be powered by the driving load 110;

- a centrifugal type wheel mounted on an axis of the electric motor;

- a motor support comprising a housing in which the electric motor can be housed.

All of these elements are configured to be mounted in an air conditioning, ventilation and / or heating device via said engine support.

In a nonlimiting embodiment, a control element 111 is mounted on the motor support of the air blower 1. In another nonlimiting embodiment, a control element 111 is mounted at a distance from the air blower 1 on or in the air conditioning, ventilation and / or heating device.

Since such blowers are known to those skilled in the art, they are not described in detail here. In a nonlimiting embodiment, an air blower 1 is used in an air conditioning, ventilation and / or heating device for a motor vehicle (called in English HVAC "Heating Ventilation and Air Conditioning") or to cool the engine of the motor vehicle.

Thus, the invention described has the following advantages in particular:

- it is a simple solution to implement and inexpensive;

- it allows, thanks to the first protection module 10, to the main non-return diode D8, and to the main switch Q2, during a USS overvoltage (in particular in the event of a DC short circuit) in the second supply network electrical G48 and therefore during a USS overvoltage, to isolate the communication bus BLW and the first connection interface 112 from the second connection interface I48, and therefore from the second electrical supply network G48. They are thus not damaged;

- it allows, thanks to the second protection module 20, to the main non-return diode D8, and to the main switch Q2, during a common ground loss GND, to isolate the communication bus BLW and the first interface of connection 112 of the second connection interface I48, and therefore of the second power supply network G48. They are thus not damaged;

- it allows, thanks to the second protection module 20 and the main switch Q2, to protect the DLW control module during a common GND mass loss;

- It protects any external electronic device 2 which is connected to said electric heating device 1;

- thanks to the use of the microcontroller MC, it allows the use of fewer electronic components on the PCBA printed circuit board comprising the functional module 11, the first protection module 10 and the main switch Q2. This makes it a cheaper and more reliable solution.

Claims (12)

1. Electric heating device (1) for a motor vehicle adapted to be supplied with voltage by a first electric supply network (G12) and by a second electric supply network (G48), according to which the electric heating device ( 1) includes: - a first connection interface (112) with the first electrical supply network (G12); - a second connection interface (I48) with the second power supply network (G48); - a third connection interface (ILW) with a communication bus (BLW); - a functional module (11) connected to the first connection interface (112) and to the second connection interface (I48); - a main switch (Q2) connected to the functional module (11) adapted to transmit signals (DAT) on the communication bus (BLW); - a first protection module (10) adapted to isolate the first power supply network (G12) and the communication bus (BLW) from the second power supply network (G48) when there is an overvoltage (USS) between the functional module (11) and the first connection interface (112) and the third connection interface (ILW), said first protection module (10) comprising: an overvoltage detection module (100) comprising a microcontroller (MC) suitable for: - detecting an overvoltage (USS) between the functional module (11) and the third connection interface (ILW) and / or between the functional module (11) and the first connection interface (112); - open a second protection switch (Q4) following said detection; - a secondary switch (Q6) adapted to open when there is said overvoltage (USS) so as to open the main switch (Q2); - said second protection switch (Q4) adapted to open so as to open the secondary switch (Q6). 2. An electric heating device (1) according to claim 1 according to which the microcontroller (MC) comprises: - a first input (E1) adapted to measure the first voltage (U1) between the functional module (11) and the secondary switch (Q6); - an output (S1) adapted to control the opening of the second protection switch (Q4); - a second input (E2) adapted to measure a voltage (U10) between the functional module (11) and the main switch (Q2). 3. An electric heater (1) according to claim 1 or claim 2, wherein the electric heater (1) further comprises a main check diode (D8) adapted to prevent a current from flowing to the first power supply network (G12) when the main switch (Q2) is open. 4. Electric heating device (1) according to any one of claims 1 to 3, according to which the electric heating device (1) further comprises a secondary non-return diode (D11) adapted to prevent a current (i3) to circulate in the second protection switch (Q4). 5. Electric heating device (1) according to any one of claims 1 to 4, according to which the electric heating device (1) further comprises a main return resistor (R7) adapted to guarantee the opening of the main switch (Q2) 5 when there is said overvoltage (USS). 6. Electric heating device (1) according to any one of claims 1 to 5, according to which the electric heating device (1) further comprises a secondary return resistor (R15) adapted to guarantee the opening of the secondary switch 10 (Q6) when there is said overvoltage (USS). 7. An electric heating device (1) according to any one of claims 1 to 6, according to which the electric heating device (1) further comprises a basic resistance (R14) adapted to guarantee the closing of the secondary switch. (Q6) 15 when a current (Ib6) flows in said secondary switch (Q6). 8. Electric heating device (1) according to any one of claims 1 to 7, according to which the electric heating device (1) further comprises a self-resetting fuse (R6) adapted to protect the communication bus (BLW ) against a current sur20. 9. Electric heating device (1) according to any one of claims 1 to 8, according to which the electric heating device (1) further comprises a tertiary non-return diode (D6) adapted to guarantee that the main switch (Q2) remains open. 10. Electric heating device (1) according to any one of claims 1 to 9, according to which the electric heating device (1) further comprises a protection diode (D3) adapted to protect the main switch (Q2 ) against an increase in the voltage (U1) of the first power supply network (G12). 11. Electric heating device (1) according to any one of claims 1 to 10, according to which the heating device 5 electric (1) further comprises an additional protection diode (D12) adapted to protect the secondary switch (Q6) against a voltage reversal (U1). 12. Electric heating device (1) according to any one of claims 1 to 11, according to which the functional module (11) 10 includes a control module (DLW) adapted to be supplied with voltage by the first power supply network (G12) and for receiving and / or transmitting signals (DAT) via the communication bus (BLW). 13. Electric heating device (1) according to any one 15 of claims 1 to 12, according to which the main switch (Q2) is arranged near the third connection interface (ILW). 3O56Î 1/7 GND