ELECTRICAL OR ELECTRONIC DEVICE WITH TWO SUPPLY VOLTS

Description

[0001] The present invention relates to electrical or electronic devices requiring two separate supply voltages.

[0002] The invention relates in particular, although not exclusively, to the field of motor vehicles where certain equipment must be designed to operate with two supply voltages of distinct values, typically a low voltage of around 12 Volts, and a medium voltage of around 48 Volts.

[0003] Document WO 2012 / 131235 relates to an electrical supply system comprising two electrical supply networks and a strategy applied to a hybrid vehicle for the purpose of charging two different batteries - one being lead-acid with a nominal voltage of 12 V and the other lithium with a nominal voltage of 60 V. The system includes a switch module (fuse 17) interposed in series on the common ground, the switch module being capable of switching to an open position in the event of an increase in the current flowing on the common ground.

[0004] For this type of equipment, a specification defining, in particular, certain architectural rules and validation tests is currently being developed by a consortium of automotive manufacturers. This specification ("Electrical and Electronic components in the vehicle 48 V") is being developed by a consortium of automotive manufacturers. Vehicle electrical system, Requirements and tests (specification 148 of 29 / 08 / 2011) requires in particular: that all 12 Volt / 48 Volt equipment have a common ground, and include a 12 Volt connector interface to allow its connection to the 12 Volt vehicle network, and a 48 Volt connector interface to allow its connection to the 48 Volt vehicle network, each connector interface having its own ground connection; that all 12 Volt / 48 Volt equipment pass a leakage current measurement test, so as to ensure that the 48 Volt and 12 Volt power supplies are well protected against these leakage currents; that all 12 Volt / 48 Volt equipment pass a 48 Volt network ground cable loss test, so as to ensure that the 12 Volt network ground cable is not at risk of being damaged following a fault in the 48 Volt network ground cable.

[0005] There figure 1 This diagram schematically illustrates the setup used for the leakage current validation test of an electrical or electronic device 1, comprising a first connector interface 10 for 12 volts and a second connector interface 11 for 48 volts. This test consists of connecting all the inputs / outputs of the first connector interface 10 to the first terminal of a DC voltage generator, connecting the inputs of the second connector interface 11 to the second terminal of the DC voltage generator, applying a voltage of 70 volts using the DC voltage generator, and measuring the current with a standard ammeter. The electrical or electronic device 1 is validated if, during this test, the measured current remains less than or equal to 1 microampere (absolute value).

[0006] The second ground fault test involves connecting the electrical or electronic device between two power supplies, one 12 volts and the other 48 volts, simulating a ground fault on the 48-volt side, and checking for any damage to the ground wire on the 12-volt side. The electrical or electronic device is considered valid if, during this test, no damage is observed after approximately 30 minutes.

[0007] We already know of electrical or electronic device architectures capable of operating with two supply voltages. figure 2 This schematically illustrates an auxiliary heater module 2 which uses two 12-volt power supplies: one low-power supply, represented by the voltage generator 3, and the other higher-power supply, typically in the range of 1000 to 1200 watts, represented by the voltage generator 4. Such an auxiliary heater is used when starting a motor vehicle to warm the passenger compartment more quickly. The low-power supply 3 is used for the management and interface of module 2, while the higher-power supply 4 is used to power the heating elements (not shown) contained within the module. As can be seen in the architecture of the figure 2 Only the ground of voltage generator 4 is connected to the module. Furthermore, the module's LIN data input is powered by both voltage generator 3 and the ground of generator 4. Therefore, such an architecture could not be used for a 12V / 48V device conforming to the aforementioned specification, which requires two separate grounds for each power supply. Moreover, the loss of the ground wire from generator 4 means that module 2 can no longer communicate via its LIN data input.

[0008] There figure 3 This schematically represents another known architecture of an electrical or electronic device 5 used in electric vehicles. Here, the device 5 is powered, via two connector interfaces 50 and 51, with two very different voltages: a first low voltage of approximately 12 Volts, represented by the voltage generator 3, and a second very high voltage of approximately 400 Volts, represented by the voltage generator 6. For safety reasons, this type of device 5 must include an isolation transformer 52 to create galvanic isolation between the 12 Volt power supply and the 400 Volt power supply.

[0009] A similar architecture could be used to create a 12V / 48V electrical or electronic device compatible with the aforementioned specification. However, this solution is expensive and bulky due to the use of an isolation transformer, and remains complex to implement.

[0010] The invention aims to overcome the previous drawbacks by proposing a simple architecture for an electrical or electronic device with two supply voltages, for example 12 Volts / 48 Volts, which meets the specification requirements relating to the presence of two ground terminals, and which allows to satisfy at least one of the two aforementioned tests.

[0011] The present invention meets this objective by proposing an electrical or electronic device capable of being powered in operation by a first voltage value generated by a first electrical network and by a second voltage value greater than the first voltage value and generated by a second electrical network, according to claim 1.

[0012] Normal connection conditions mean the connections necessary for the normal operation of the device, i.e. the usual connections of the connector interfaces to the two electrical networks.

[0013] Other possible particularly advantageous features are defined in the dependent claims.

[0014] The invention and its advantages will be better understood from the following description of a non-limiting example of implementation of the invention, made with reference to the accompanying figures, in which: there figure 1 The diagram, already described above, schematically represents the equivalent electrical circuit for a leakage current measurement test of a 12 Volt / 48 Volt device prescribed by the aforementioned specification 148; figure 2 The diagram, already described above, schematically illustrates a known architecture for a device using two 12-volt supply voltages; figure 3 The diagram, already described above, schematically illustrates a known architecture for a device using a 12-volt supply voltage and a 400-volt supply voltage; figure 4 schematically illustrates an example of the architecture of an electrical or electronic device with two supply voltages, for example 12 Volts / 48 Volts, according to the present invention.

[0015] There figure 4 represents an electrical or electronic device 7 according to one possible embodiment of the invention, within the non-limiting scope of a dual 12 Volt / 48 Volt power supply. This device 7 is shown in its operating conditions, i.e., receiving a first supply voltage of 12 Volts from a first 12 Volt network (represented by a voltage generator 3), and a second, higher supply voltage, typically on the order of 48 Volts, from a second 48 Volt network (represented by a voltage generator 8). To achieve this, the device 7 comprises: a first connector interface 70 suitable for being connected to the two terminals of the voltage generator 3, i.e. in practice to the ground conductor GND_12 and the 12 Volt voltage conductor of the first 12 Volt network; a second connector interface 71 suitable for being connected to the two terminals of the voltage generator 8, i.e. in practice to the ground conductor GND_48 and the 48 Volt voltage conductor of the second 48 Volt network.

[0016] Inside device 7, the ground connections of the two connector interfaces 70 and 71 are connected together to form a common ground.

[0017] Between the two connector interfaces 70 and 71, the device 7 preferably includes an EMC (Electromagnetic Compatibility) filtering module 72 to eliminate possible voltage variations, and a 12V / 48V interface module 73 that integrates the device's specific functionalities. For example, if the device 7 is an auxiliary heater, the module 73 will include the control components, the interface, and the heating elements.

[0018] The device 7 further includes a first switch module 74 interposed in series on the common ground connecting the two ground connections of the connector interfaces 70 and 71, this first switch module 74 being able to be controlled in a closed position as long as the current through it is less than a threshold value of approximately 200 mA, and to switch to an open position if the current through it goes above the threshold value.

[0019] This first switch module 74 can be made by combining a current measurement circuit, typically composed of an amplifier and a comparator, and a MOSFET transistor controlled to open the ground circuit as soon as the current measurement circuit detects a current greater than the threshold value.

[0020] Alternatively and preferably, this switch module 74 will consist of a resettable fuse, for example a positive temperature coefficient resistor or PTC resistor, of infinite value if the current through the resistor is much greater than the threshold value.

[0021] The presence of this first switch module 74 allows the device 7 to pass the GND_48 ground cable loss test. Indeed, if the GND_48 ground cable is cut, a significant current will pass through the common ground and cause the switch 74 to open.

[0022] Device 7 further includes a second switch module 75, also connected in series to the common ground, along with a blocking diode 76. This second switch module is, for example, a MOSFET transistor powered by the 12-volt network. Its source S and drain D are connected respectively to the ground connection of connector module 70 and the ground connection of connector module 71, and its gate G receives the 12-volt supply. In normal operation, this MOSFET transistor is typically in the closed position, and its gate-to-source voltage VGS is then equal to 12 volts. Diode 76, in turn, directs the current in the 12-volt direction towards the 12V / 48V interface module 73.

[0023] The purpose of this second switch module 75 is to allow device 7 to pass the leakage current measurement test. Indeed, by performing this test (in accordance with the electrical diagram of the figure 1 All the inputs / outputs of the first connector interface 70 are interconnected, so that the voltage VGS becomes zero, even when the 70-volt voltage imposed by the test is applied, and switches the transistor to its open position. The blocking diode 76 ensures that no current can flow in the other direction, that is, from the second connector interface 71 to the first connector interface 70.

[0024] In view of the above, each of the two switch modules 74 and 75 described previously is capable of switching to an open position following a change in the connection conditions of the first or second interface: in particular, for the leakage current measurement test, the connections of the connector interface 70 are modified compared to normal operation, hence the closure of the switch module 75. Similarly, the loss (disconnection or damaged cable) of the ground cable GND_48 constitutes a change in the normal connection conditions of the second connector interface 71, resulting in the closure of the switch module 74.

[0025] In all cases, the resulting device meets various requirements of specification 148, while having a simple, inexpensive and compact structure.

[0026] Although the invention was described in the context of the 12 Volt / 48 Volt application in the automotive field, it may be of interest in all cases where a device requires a dual power supply at so-called safe voltage values.

Claims

1. Electrical or electronic device (7) capable of being powered in operation by a first voltage value generated by a first electrical network (3) and by a second voltage value higher than the first voltage value and generated by a second electrical network (8), the device comprising: - a first connector interface (70) capable of being connected, under normal connection conditions, to a ground conductor (GND_12) and a voltage conductor of the first electrical network (3); - a second connector interface (71) capable of being connected, under said normal connection conditions, to a ground conductor (GND_48) and a voltage conductor of the second electrical network (8); each connector interface having a ground connection and the ground connections of the two connector interfaces (70, 71) being connected together to form a common ground; and - at least a first and a second switch module (74; 75) interposed in series on the common ground, each switch module being capable of switching to an open position following a modification of the connection conditions of the first or second interface, the first switch module (74) being capable of being controlled in a closed position as long as the current passing through it is less than a threshold value of approximately 200 mA, and of switching to an open position if the current passing through it goes above the threshold value, the second switch module (75) being capable of switching to an open position as soon as all inputs / outputs of the first connector interface are connected together, characterized in that the second switch module (75) is associated with a non-return diode (76) capable of preventing any current from flowing to the first connector interface (70) when the second switch module (75) is in the open position.

2. Device according to claim 1, characterized in that said first switch module (74) comprises a positive coefficient resistor in series on the common ground.

3. Device according to claim 1, characterized in that said first switch module (74) comprises a transistor controlled by a current measurement circuit capable of measuring the current flowing on the common ground.

4. Device according to claim 1, characterized in that the second switch module (75) comprises a MOSFET transistor powered by voltage from the first electrical network (3).

5. Device according to any one of the preceding claims, characterized in that the first voltage value is approximately 12 Volts, and the second voltage value is approximately 48 Volts.