WO2008040859A1 - Battery circuit-breaker comprising means for determining a current flowing through the input electric terminal thereof - Google Patents

Abstract

The invention relates to a circuit-breaker (1) comprising: an input electric terminal (100) to be connected to an accumulator battery (300); an output electric terminal (200); contact means (3) for closing or opening the electric contact between the two input and output electric terminals; power consuming members (20) connected to said contact means by a first connection cable (107); means for determining the current flowing through the input electric terminal, that comprise means for measuring a voltage including two connection cables (105, 106) one of which at least has a high resistance, means for calculating the current intensity (301) and optionally an electric calibration circuit; and a junction electric circuit (330) connecting said high-resistance connection cable and said first connection cable and having a semi-conductor member provided thereon.

Description

 BATTERY CIRCUIT BREAKER COMPRISING MEANS FOR DETERMINING THE CURRENT THROUGH ITS ELECTRIC ENTRY TERMINAL

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention generally relates to the measurement of the intensity of a current delivered by an accumulator battery in a circuit breaker.

It relates more particularly to a circuit breaker comprising an electrical input terminal intended to be connected to a storage battery, an electrical output terminal, contact means adapted to close or to open the electrical contact between the two electrical terminals. input and output, and means for determining the current flowing in the input electrical terminal.

BACKGROUND

Currently, there is already known a circuit breaker of the aforementioned type in which the determination means comprise a hall effect sensor attached to the outer face of the electrical input terminal.

This sensor is conventionally constituted by a semiconductor wafer fed by a supply current. This plate is sensitive to the presence of a magnetic field perpendicular to it, such a field generating a measurable potential difference between each of its faces.

The main drawback of such determination means is that they have a low accuracy and are sensitive to surrounding magnetic fields produced by sources other than the electrical input terminal of the circuit breaker. There is also known a circuit breaker in which the current determining means are arranged in a separate housing of the circuit breaker box, which is connected by means of an electric cable to the electrical input terminal of the circuit breaker. These determination means then consist of a "shunt" (electrical resistance of a value of the order of a hundred micro-ohms) associated with a heavy electrical system for precisely determining the value of the current flowing in the terminal electrical input of the circuit breaker.

The disadvantages of such determination means are that they are expensive, bulky and difficult to mount and connect to the circuit breaker. In addition, the value of the "shunt" is important so that it causes significant energy losses.

OBJECT OF THE INVENTION

In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a new circuit breaker in which the means for determining the intensity of the current are more precise, less expensive and very compact.

More particularly, according to the invention there is provided a circuit breaker as defined in the introduction, in which there is provided: an input electrical terminal intended to be connected to a storage battery,

- an electrical output terminal,

contact means adapted to close or open the electrical contact between the two electrical input and output terminals; current-consuming elements connected to said contact means by a first connection cable;

means for determining the current flowing in the input electrical terminal which comprise:

means for measuring a voltage comprising two connection cables which are connected to two measuring points of the electrical input terminal and of which at least one of them has a high resistance, and

means for calculating the intensity of the current from said measured voltage and from the open or closed position of the contact means,

an electrical junction circuit which connects said high resistance connection cable and said first connection cable, and on which is provided a semiconductor element adapted to block currents originating from the high resistance connection cable.

Thus, thanks to the invention, it is possible to perform a precise measurement of the electrical potential at two measurement points of the electrical input terminal. This input electrical terminal having a known resistance between these two measuring points, it is possible to calculate the value of the intensity of the current delivered by the accumulator battery from the difference of measured potentials and the value of said resistance. Furthermore, when the contact means are in the open position, the intensity of the current delivered by the battery has a low value. This current is used to power the current consuming elements via the high resistance connection cable and the electrical junction circuit. Therefore, thanks to the invention, the overall resistance of the circulation circuit is high when the contact means are in the open position. The measurement of the weak current (of the order of Ampere) is then made more precise.

On the other hand, when the contact means are in the closed position, the intensity of the current delivered by the battery has a significant value. It flows directly from the electrical input terminal to the electrical output terminal via the contact means. The current-consuming elements are powered by the first connection cable. The semiconductor element prevents any flow of current between the high resistance connection cable and this first connection cable. Therefore, thanks to the invention, the overall resistance of the current flow circuit is low when the contact means are in the closed position. There is therefore little energy loss even if the value of the intensity of the current to be measured is large (of the order of thousands of amperes). This value being important, the current determination has a good accuracy. According to a first advantageous characteristic of the invention, the electrical input terminal, between the two measuring points, has a resistance one hundred times lower than the sum of the resistance of the high resistance connection cable and the resistance of the terminal. electrical input, between the two measuring points. Advantageously, the current determining means comprise at least one calibration electrical circuit comprising in series a switch and a resistor of known value, said calibration electrical circuit being connected, on one side, to said first connection cable whose electrical potential is measured, and, on the other, at a known potential point. The resistors are generally insensitive to the surrounding magnetic fields. However, other factors can distort the calculation of the current, such as temperature changes that change the resistance value of the input electrical terminal. The calibration circuit makes it possible, by closing the switch, to vary the intensity of the measured current by injecting an additional current into the circuit. The value of this additional current being very precisely known, it makes it possible to calibrate the means for calculating the current. Other advantageous and non-limiting characteristics of the circuit breaker according to the invention are the following:

- there is provided another electrical calibration circuit connected, on one side, to a measured potential point located between the current consuming elements and the point of connection of said electrical connection circuit on the high resistance connection cable, and, on the other, at a known potential point;

said other electrical calibration circuit is connected to the electrical junction circuit, between the semiconductor element and the point of connection of said electrical junction circuit on the high resistance connection cable, and the resistance of the first electrical circuit. calibration also constitutes the resistance of the other electrical calibration circuit;

said other electrical calibration circuit is connected to the first connection cable, and the first calibration electrical circuit has a resistance value at least ten times greater than the value of the resistance of the other calibration electrical circuit ; the switch of the first electrical calibration circuit is adapted to close when the contact means are open, while the switch of the other electrical calibration circuit is adapted to close when the contact means are closed;

the high-resistance connection cable has a large cross-section and has a resistance value of the order of one milli-ohm;

the high-resistance connection cable has a small section giving it a resistance of the order of one milli-ohm;

the semiconductor element is formed by a diode whose anode is connected on the side of the high resistance connection cable; the semiconductor element is formed by a MOSFET transistor; and

- Means are provided for comparing the electrical potentials measured on the electrical input terminal and on the first connection cable. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be implemented. In the accompanying drawings:

- Figure 1 is a perspective view of the inside of a housing of a circuit breaker according to the invention;

FIG. 2 is a schematic view of a current cutoff device at the output of a storage battery, which comprises the circuit breaker of FIG. 1;

- Figures 3A and 3B are schematic top views of the circuit breaker of Figure 1 wherein the contact means are in the open or closed position; and

FIGS. 4 to 6 are diagrammatic views of the electrical circuits of the electronic circuit board of the circuit breaker of FIG. 1 according to three embodiments of the invention.

In Figure 1, there is shown a circuit breaker 1 according to the invention which is here intended to be arranged in a vehicle. This circuit breaker 1 comprises a parallelepiped-shaped housing 1A formed by two distinct parts intended to be fitted one above the other to define a housing 1B internally.

On one of its side walls, the housing 1A carries two identical electrical terminals, an electrical input terminal 100 and an electrical output terminal 200, each having a body 101, 201 of elongated shape extending from the inside the housing 1 A to beyond its side wall.

A first end of each of these bodies 101, 201, that disposed inside the housing 1A, is connected to a contact member 102, 202 fixed.

These two electrical terminals 100, 200 are here made of silver-plated copper.

The body 101 of the electrical input terminal 100 laterally comprises two peripheral grooves 103, 104 for receiving a connection cable 105, 106. These two peripheral grooves 103, 104 are arranged near the contactor element 102. They have a shallow depth of about 3 millimeters, and allow the connection cables to be held laterally to crimp them at the bottom of the groove to fix them.

Advantageously, one of the connection cables 106 has a small section which gives it a high resistivity. The length of this connection cable 106 is designed so that it has a precisely determined resistance of the order of one milli-ohm.

Alternatively, the two connection cables may have a large section, so as to reduce their resistivity very strongly. According to this variant, one of the connection cables is provided with an electrical resistance of a value of the order of one milli-ohm.

In any case, the input electrical terminal 100 between the two peripheral grooves 103, 104 has a resistance RO that is one hundred times smaller than the sum R1 of the resistance of the high-resistance connection cable 106 and the resistance of the electrical input terminal 100, between the two peripheral grooves 103, 104.

The two contactor elements 102, 202 of the two electrical input terminals 100 and output 200 have a square section and a small thickness. They form a plane face turned towards the inside of the casing 1A.

The housing 1 B accommodates all the electrical components of the circuit breaker 1. One of these electrical components is contact means 3 adapted to close or to open the electrical contact between the two electrical terminals 100 and 200 output circuit breaker 1.

These contacting means comprise in particular a contact bridge 3 constituting a U-section beam whose two branches are oriented towards the interior of the housing 1A and whose upper face faces the flat faces of the contact elements 102, 202 of the electrical input terminals 100 and output 200. This contact bridge 3 has a length which allows its upper face to be simultaneously able to come into contact with the two planar faces of the contact elements 102, 202. The contact bridge 3 present by elsewhere a central opening for securing it to a movable shaft 2A engaged in this opening. This movable shaft 2A has at mid-height a flange 4 and at one of its ends a threaded portion. A compression spring 5 is engaged on this shaft so as to bear against the flange 4. The contact bridge 3 is as for him positioned against this compression spring 5. A nut 6 is screwed on the threaded portion of the movable shaft 2A so as to maintain the contact bridge 3 against the compression spring 5.

The movable shaft 2A is adapted to translate between two stable positions. In a first stable position, the contact bridge 3 is arranged at a distance from the contacting elements 102, 202 (open position), and in a second stable position, the contact bridge 3 bears against these contact elements (closed position). The movable shaft 2A is preferably made of non-magnetic material.

A bistable actuating device 2 of cylindrical shape is connected to the movable shaft 2A and is able to move it in translation between its first and second stable positions.

The housing 1A also internally comprises an electronic circuit 10 for controlling the bistable operating device 2. This electronic circuit 10 comprises in particular a terminal block (not shown) to which are connected a first connection cable 107 connected at its other end to the bridge of FIG. contact 3, as well as the connection cables 105, 106 connected to the electrical input terminal 100.

The set of electrical components contained in the housing 1A thus makes it possible to open and close the electrical contact of the electrical circuit to which the circuit breaker 1 is connected.

As shown particularly in FIG. 2, this circuit breaker 1 makes it possible to isolate an accumulator battery 300 electrically from the other components of the vehicle.

More specifically, the body 101 of the electrical input terminal 100 of the circuit breaker 1 is connected via a power supply cable 150 to the positive terminal of the storage battery 300 whose negative terminal is connected to an electrical ground. The circuit breaker 1 and the accumulator battery 300 are generally arranged in a battery-box 301 fixed to the frame 600 of the vehicle which forms this electric mass. The body 201 of the electrical output terminal 200 of the circuit breaker 1 is in turn connected by two separate electrical circuits, on the one hand, to a suitable alternator 500, when it is rotated by the main motor (no represented) of said vehicle, to produce an electric current for charging the accumulator battery 300, and, secondly, an electric motor 400 adapted to rotate the main engine of the vehicle to start it. This main engine may for example be an internal combustion engine. The output electrical terminal 200 can of course be connected to other vehicle components such as lights. As shown in FIGS. 3A, 3B and 4, the electronic card 10 comprises current-consuming elements 20, such as a microprocessor which controls the opening and closing of the contact means 3, a clock of the vehicle or an alarm. .

These current consuming elements are supplied with current by the accumulator battery 300 via the first connection cable 107 (which is connected to the contact bridge 3) when the contact bridge is in the closed position.

For their power supply when the contact bridge 3 is in the open position, the electronic card 10 comprises an electrical junction circuit 330 which connects the first connection cable 107 to the high resistance connection cable 106 (which is connected to the terminal electrical input 100). This junction electrical circuit 330 includes a semiconductor element 331 which is adapted to block the weak currents from the high resistance connection cable 106.

More particularly, thanks to the electrical junction circuit 330, when the contact means are in the closed position (FIG. 3B), the supply of the current consuming elements 20 is via the first connection cable 107, without any current being It passes through the high-resistance connection cable 106. On the other hand, when the contact means are in the open position (FIG. 3A), the supply of the current-consuming elements 20 is via the high-resistance connection cable 106.

Here, the semiconductor element is formed by a diode whose anode is connected to the side of the high resistance connection cable 106. This diode is therefore adapted to block any current from the first connection cable 107. adapted to block the weak currents from the high resistance connection cable 106, but passes in this direction currents of intensity a little more important. Thus, when the contact bridge 3 is in the open position, the supply current of the current consuming elements 20 passes through the diode 331, whereas when the contact bridge is in the closed position, this current passes through the first cable of connection 107. In this position of the contact means, the low currents flowing in the high resistance connection cable 106 are indeed blocked by the diode.

Alternatively, if the input electrical terminal 100 were connected to the negative terminal of the storage battery 300, the anode of the diode would be connected to the side of the first connection cable 107.

In summary, when the contact means 3 are closed, the electrical input terminal 100, the contact means 3 and the first connection cable 107 form a first feed path (bold line in FIG. 3B) of the consumer elements 20. When the contact means 3 are open, the electrical input terminal 100, the high-resistance connection cable 106, the electrical connection circuit 330 and a part of the first connection cable 107 form a second path. supply (bold line in FIG. 3A) of the current-consuming elements 20.

As will be described in more detail below, the resistance affecting the calculation of the intensity of the flowing current, for a part towards the electrical outlet terminal 200 and for another part according to the first supply path of the elements. current consumers 20, generally presents the value RO (resistance of the electrical input terminal 100 between its two peripheral grooves shown in very thick lines in Figure 3B). On the other hand, the resistance influencing the calculation of the intensity of the current flowing along the second supply path of the current-consuming elements 20 generally has the value R1 much greater than RO (which is generally equal to the resistance of the connection cable 106 and which is shown in very thick lines in Figure 3A). The electronic card 10 furthermore comprises means for determining the current flowing in the electrical input terminal 100.

These current determining means comprise, firstly, means for measuring a voltage, that is to say a potential difference between two points. These measuring means are here constituted by the two connection cables 105, 106 connected to the electrical input terminal 100. These connection cables 105, 106 each measure, independently of one another, an electric potential U1, U2.

The electric potential U1 measured by the connection cable 105 which is not very resistive corresponds to the potential of the electrical input terminal 100 at the level of a first measuring point P1 belonging to the first peripheral groove 103 of the terminal.

The electric potential U2 measured by the high resistance connection cable 106 corresponds to the potential of a point whose position is variable depending on whether the contact means 3 are in the closed or open positions.

Indeed, as previously described, the path of the current for supplying the current consuming elements 20 is different depending on the position of the contact bridge 3.

Therefore, when the contact bridge 3 is in the closed position, the measured potential U2 corresponds to the potential of the electrical input terminal 100 at a second measurement point P2 belonging to the second peripheral groove 104 of the terminal. The resistance proportional to the potential difference measured between the two measuring points P1, P2 corresponds to the resistance RO of the electrical input terminal 100 (shown in very thick lines in FIG. 3B).

On the other hand, when the contact bridge 3 is in the open position and the current supplying the current consuming elements 20 passes through the high resistance connection cable 106, the potential U2 measured corresponds to the potential of the connection point P3 of the electrical circuit. in practice, this connection point P3 is located on an integrated circuit of the electronic card 10. The resistance proportional to the potential difference measured between the two measurement points P1, P3 corresponds to the sum R1 of the resistances of the input electrical terminal 100 and the high-resistance connection cable 106 (shown in very thick lines in FIG. 3A). This sum of resistors R1 has a value much greater than that of the resistance RO.

In any event, the potential difference measured between the two peripheral grooves 103, 104 or between the first peripheral groove 103 and the connection point P3 provides a measured voltage value. Knowing the value of the resistor RO (about 10 micro-ohms) between the two peripheral grooves 103, 104, the microprocessor can calculate, from the measured voltage and the resistance RO, the intensity of the current flowing in the electrical terminal. 100 when the contact means 3 are in the closed position. Furthermore, knowing the value of the sum R1 of the resistances of the electrical input terminal 100 between its two grooves and the high resistance connection cable 106 (about 1 milli-ohm), the microprocessor can also calculate, starting from the measured voltage and the overall resistance R1, the intensity of the current flowing in the electrical input terminal 100 and in the high-resistance connection cable 106 when the contact means 3 are in the open position.

To do this, the electronic card 10 comprises means for calculating the intensity of the current from said measured voltage. The calculation means comprise a subtractor operational amplifier 301, each of whose two inputs is connected to one of the two connection cables 105, 106.

In a manner known per se, the subtractive operational amplifier 301 comprises an operational amplifier 302 powered for its current operation and provided with two input terminals and an output terminal.

The input terminals are connected to the connection cables 105, 106 via resistors 303, 304 of the same value. The input terminal connected to the connection cable 105 is further connected to the electrical ground via a resistor 305. Furthermore, the input terminal connected to the connection cable 106 is connected to the output terminal of the operational amplifier 302 through a resistor 306 of equal value to that of the resistor 305 connected to ground.

The ratio between the value of this resistor 305 and that of the resistor 303 connected to the connection cable 106 determines the gain K of the subtractive operational amplifier 301. Thus, the potential U3 of the output of the subtractive operational amplifier 301 corresponds to produces the gain K of the subtractive operational amplifier 301 and the potential difference measured between the two connection cables 105, 106 according to the following formula:

U3 = K. (U2-U1), K being the gain of the subtractive operational amplifier 301, U1 and U2 being respectively the potentials of the connection cables 105, 106, and U3 being the potential of the output terminal of the subtractor operational amplifier 301.

This output terminal is connected to an analog digital converter 310 of the electronic card 10 of the circuit breaker 1. This analog converter digital 310 scans the potential U3 measured at the output of the subtractor operating amplifier 301 so that it can be operated by the microprocessor of the electronic card 10. The microprocessor can then calculate the value of the intensity I of the current passing in the input electrical terminal by performing one or the other of the following calculations.

When the contact means are in the closed position: I = U3: (K.R0). It will be noted here that when the contact means are in the closed position, the value RO being low, the determination means generate little energy loss to determine the value of the intensity of a strong current. When the contact means are in the open position: I = U3: (K.R1).

It will be noted here that when the contact means are in the open position, the value R1 being important, it is possible to accurately determine the intensity of a low current.

According to a first embodiment more particularly shown in FIG. 4, the means for determining the intensity of the current further comprise a single calibration electrical circuit 320 adapted to calibrate the measurement chain of the intensity of the current. This electrical calibration circuit 320 is indeed useful insofar as, on the one hand, the subtractive operational amplifier 301 is not perfect so that the potential U3 measured on its output has an inherent error in the operation of the operational amplifier 302, and, on the other hand, it may appear variations of the value of the resistance RO of the electrical input terminal 100 between the two peripheral grooves 103, 104. Indeed, the temperature variations and a inaccuracy in the positioning of the electrical wires 105, 106 can vary substantially the value of this resistance RO. It is the same for the value of the resistance R1.

This electrical circuit 320 comprises in series a switch 321 and a resistor 322 of known value; it is connected, on one side, to the first connection cable 107 whose electrical potential is measured by the microprocessor, and, on the other hand, to the electrical earth (identical to that on which the negative terminal of the battery is connected) accumulators 300). More specifically, the first side of this calibration electrical circuit 320 is connected between the current consuming elements 20 and the diode 331. The switch 321 here is an electrical transistor whose open or closed position is controlled by the microprocessor.

The resistor 322 has a value of 10 ohms which is much greater than the value of the resistor RO of the electrical input terminal 100 between the two peripheral grooves 103, 104. This resistor 322 has a thermal sensitivity of less than 0.005% per degree. Celsius so that temperature differences have little effect on the measurement result.

The calibration method of the current measurement chain has different steps. During a first step, the switch 321 being open, the microprocessor calculates using the above formulas an approximate value of the intensity of the current passing through the electrical input terminal 100. Then, during a second step, the microprocessor controls the closing of the switch 321. During a third step, it calculates again the intensity of the current flowing between the two peripheral grooves 103, 104 of the electrical input terminal 100. part of the measured current is injected by the electrical circuit 320, the result of the calculation is different. This portion of the current has a known value intensity which depends on the potential measured on the first connection cable 107 and the value of the resistor 322. Finally, during a fourth and last step, knowing the exact value of the resistance 322 of the calibration electrical circuit 320, the microprocessor compares the two calculated intensities, and determines a refined value of the intensity of the current flowing through the input electrical terminal.

In such a way that the variations of current due to the variations of the electricity requirements of the electrical equipment of the vehicle do not distort the calculations, this closing of the switch 321 can be carried out regularly, for example every 50 milliseconds, so that the conditions between the first and third steps of the method are substantially identical. Another method making it possible to ensure that the calculations are not distorted consists in opening the contact means 3 before carrying out the measurement steps mentioned above.

According to an advantageous characteristic of the circuit breaker 1, the electronic card 10 comprises means for comparing the electrical potentials of the electrical input terminal 100 (measured via one of the two connection cables 105, 106) and the contact bridge 3 (measured via the first connection cable 107). These comparison means allow the microprocessor to determine the open or closed position of the contact bridge 3. Indeed, a difference of measured minute potentials indicates that the contact bridge 3 is in the closed position while a significant measured potential difference indicates that the contact bridge 3 is in the open position.

The electronic circuit 10 furthermore comprises means for calculating the internal resistance of the accumulator battery 300. These calculation means are located in the microprocessor of the battery switch 1; they are adapted to derive the value of the internal resistance of the accumulator battery 300 from, on the one hand, the value of the resistance of the power supply cable 150, and, on the other hand, the value the difference of the electrical potential measured on one of the connection cables 105, 106 when the switch is open and when it is closed.

The value and increase of this internal resistance indicating the remaining life of the accumulator battery 300 connected to the circuit breaker 1, the electronic circuit 10 can thus provide the driver of the vehicle an indication of the remaining life of the storage battery 300.

It is more specifically intended to determine the internal resistance of the accumulator battery 300 when the contact bridge 3 is in the open position. To do this, the microprocessor controls regularly but at a very low frequency, closing the switch 321 of the calibration electrical circuit 320.

Conventionally, knowing then the value of the intensity of the current delivered by the accumulator battery 300 and the value of the internal resistance of the accumulator battery 300, the microprocessor of the electronic circuit 10 can determine the value of the voltage internal battery. The microprocessor can then determine the charge level of the accumulator battery 300 according to this value of the internal voltage of the battery. The electronic circuit 10 finally comprises means for determining the temperature of the accumulator battery 300. These determination means are connected to the calibration means of the current current measurement chain. These calibration means make it possible to determine with great accuracy the resistance RO of the electrical input terminal 100, between its two peripheral grooves 103, 104. However, this resistance varies very slightly depending on the temperature of the electrical input terminal 100. The microprocessor can therefore determine the value of the temperature of the electrical input terminal 100, and by Therefore, the value of the temperature of the accumulator battery 300 which depends directly on it.

According to a second embodiment of the invention more particularly represented in FIG. 5, the circuit breaker 1 comprises another electrical calibration circuit 340 connected in parallel with the first calibration electrical circuit 320. This other electrical circuit of FIG. calibration 340 comprises a switch 341 and an electrical resistor 342 connected in series. The electrical resistance 322 of the first electrical calibration circuit 320 here has a value one hundred times greater than the value of the electrical resistance 342 of the other electrical calibration circuit 340.

The switch 321 of the first calibration electrical circuit 320 is then adapted to close for the calibration of the intensity measurement chain when the contact means 3 are in the open position, while the switch 341 of the other electrical calibration circuit 340 is adapted to close when the contact means 3 are in the closed position.

Therefore, when the contact means is in the open position and the measured current has a low value, the calibration is performed with the calibration electrical circuit which has a high resistance, so as to reduce the energy losses. On the contrary, when the contact means are in the closed position and the measured current has a large value, the calibration is performed with the calibration electrical circuit which has a small resistance, so that the calibration calculation is accurate. . Since the intensity value is important, the calibration calculation remains accurate.

According to this embodiment, the means for calculating the internal resistance of the accumulator battery 300 are adapted to deduce the value of the internal resistance of the accumulator battery 300 from, on the one hand, the value of the resistance of the power supply cable 150, and, on the other hand, the value of the difference between the electric potential measured on the connection cable 106 when the switch 341 of the other calibration circuit 340 is open and when closed. Since the internal resistance of the accumulator battery 300 varies slightly rapidly, the closing frequency of this switch 341 is chosen so as to be low. The energy losses due to this measure are therefore reduced. It should be noted that the means for calculating the internal resistance of the accumulator battery 300 use this other calibration device 340 insofar as its resistance 342 is lower than that of the first calibration circuit 320, which increases the accuracy of calculations.

According to a third embodiment of the invention more particularly shown in FIG. 6, the circuit breaker 1 here also comprises another electrical calibration circuit 350. According to this embodiment, this other electrical calibration circuit 350 is connected to the junction circuit 330, between the diode 331 and the connection point P3 of the junction circuit 330 on the high resistance connection cable 106.

This other electrical calibration circuit 350 comprises a switch 351 which is its own and shares its electrical resistance 322 with the first electrical calibration circuit 320. For this purpose, the switches 321, 351 of the two electrical calibration circuits 320, 350 and the electrical resistor 322 all have a terminal connected to the same connection point P4.

Here, the switch 321 of the first calibration electrical circuit 320 is adapted to close when the contact means 3 are in the closed position, while the switch 351 of the other calibration electrical circuit 350 is adapted to close when the contact means 3 are in the open position. Therefore, the closing electrical circuit is always the one that is connected to the current flow path (via the electrical junction circuit 330 when the contact bridge 3 is open, and via the first connection cable 107 when the contact bridge 3 is closed).

As a variant, the first electrical calibration circuit 320 connected to the first connection cable 107 could here be situated, not between the diode 331 and the current-consuming elements 20, but rather between the diode 331 and the terminal block of the electronic card. 10. Its operation would be strictly identical. According to another variant not shown of this third embodiment of the invention, the electrical junction circuit may comprise not a diode but rather a switch which may be of MOSFET type. This switch is controlled, in normal operation, so as to block any current when the contact means are in the closed position, and let the current flow when these contact means are in the open position.

In addition, with such a switch, the electronic card can control the simultaneous opening of the contact bridge and the transistor, for example when the charge level of the accumulator battery is almost zero. In this way, no current feeds the current consuming elements, so that the battery no longer discharges. Therefore, the charge level of the battery remains above a threshold that allows it to operate the contact bridge when starting the vehicle.

The presence of said other electrical calibration circuit between the transistor and the connection point of the electrical junction circuit on the high-resistance connection cable makes it possible here to continue to measure the minute current passing through the electrical input terminal when the bridge contact and the transistor are simultaneously open.

The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.

Claims

1. Circuit breaker (1) comprising: an electrical input terminal (100) intended to be connected to a storage battery (300), an electric output terminal (200), contact means (3) adapted to close or open the electrical contact between the two electrical input (100) and output (200) terminals, current-consuming elements (20) connected to said contact means (3) by a first connecting cable (107), - current determining means (105, 106, 301, 320) passing through the electrical terminal of input (100) which include: means for measuring a voltage comprising two connection cables (105, 106) which are connected to two measurement points (P1, P2) of the electrical input terminal (100) and of which at least one of between them (106) has a high resistance, and means for calculating the intensity of the current (301) from said measured voltage and from the open or closed position of the contact means (3), an electrical junction circuit (330) which connects said high resistance connection cable (106) and said first connection cable (107), and on which is provided a semiconductor element (331) adapted to block currents originating from high resistance connecting cable (106). 2. Circuit breaker (1) according to the preceding claim, characterized in that the electrical input terminal (100) between the two measuring points (P1, P2) has a resistance (RO) a hundred times lower than the sum (R1) of the resistance of the high resistance connection cable (106) and the resistance of the electrical input terminal (100) between the two measurement points (P1, P2). 3. Circuit breaker (1) according to one of the preceding claims, characterized in that the current determining means (105, 106, 301, 320) comprise at least one electrical calibration circuit (320) comprising in series a switch (321) and a resistor (322) of known value, said calibration electrical circuit (320) being connected on one side to said first connecting cable (107) whose electrical potential is measured, and, the other, at a point of known potential. 4. Circuit breaker (1) according to the preceding claim, characterized in that it comprises another electrical calibration circuit (340; 350) connected, on one side, to a measured potential point located between the consumer elements. current (20) and the connection point (P3) of said electrical junction circuit (330) to the high resistance connection cable (106), and at the other to a known potential point. 5. Circuit breaker (1) according to the preceding claim, characterized in that said other electrical calibration circuit (350) is connected to the electrical junction circuit (330), between the semiconductor element (331) and the connection point (P3) of said junction electrical circuit (330) on the high resistance connection cable (106), and that the resistor (322) of the first calibration electrical circuit (320) also constitutes the resistance the other electrical calibration circuit (350). 6. Circuit breaker (1) according to claim 4, characterized in that said other electrical calibration circuit (340) is connected to the first connection cable (107), and in that the first electrical calibration circuit (320) has a resistance (322) of value at least ten times greater than the value of the resistor (342) of the other calibration electrical circuit (340). 7. Circuit breaker (1) according to the preceding claim, characterized in that the switch (321) of the first electrical calibration circuit (320) is adapted to close when the contact means (3) are open, while the switch (342) of the other electrical calibration circuit (340) is adapted to close when the contact means (3) are closed. 8. A circuit breaker (1) according to one of the preceding claims, characterized in that the high resistance connection cable (106) has a large section and has a resistance electrical value of the order of milli-ohm. 9. Circuit breaker (1) according to one of claims 1 to 7, characterized in that the high resistance connection cable (106) has a small section conferring resistance on the order of milli-ohm. 10. Circuit breaker (1) according to one of the preceding claims, characterized in that the semiconductor element (331) is formed by a diode whose anode is connected to the side of the high resistance connection cable ( 106). 11. Circuit breaker (1) according to one of claims 1 to 9, characterized in that the semiconductor element (331) is formed by a MOSFET type transistor. 12. Circuit breaker (1) according to one of the preceding claims, characterized in that it comprises means for comparing (10) the electrical potentials measured on the electrical input terminal (100) and on the first cable of connection (107).