POWER SUPPLY TO A VOLTAGE CONVERTER IN AN ELECTRIC VEHICLE

Abstract

The invention relates to an electrical voltage conversion circuit (10) in an electric or hybrid vehicle, for supplying a first 12-volt on-board network (LVN) from a second high-voltage on-board network (HVN). The voltage conversion circuit comprises a conversion unit (5) and at least two redundant power supplies for supplying said conversion unit. The two redundant power supplies comprise a first power supply and a second power supply. The conversion unit (5) comprises at least one primary internal power supply (41) and a power switching block (6). The circuit is characterized in that the first power supply (1) is from the first on-board network and the second power supply (2) is from the second on-board network. The first and second power supplies are connected by an OR circuit (3) to the internal power supply of the conversion unit. Figure 2

Description

Title of the invention: POWER SUPPLY FOR A VOLTAGE CONVERTER IN AN ELECTRIC VEHICLE

[0001] The invention generally relates to an electrical voltage conversion circuit used in an electric or hybrid vehicle.

[0002] In such an electric or hybrid vehicle, a first on-board network, known as the low-voltage network, is usually found, which is used to power a number of electrical components. The negative reference of this first on-board network is the vehicle chassis, or otherwise called the vehicle ground, and the positive voltage of this first on-board network is usually in the range of 10 volts to 15 volts. It is common, though slightly inaccurate, to refer to this network as the 12-volt on-board network. This first on-board network is the historical successor to the on-board network that became widespread in internal combustion engine vehicles, for the vast majority of vehicles produced in the latter part of the 20th century.

[0003] With the advent of vehicle electrification, the need arose to install a second on-board electrical system at a higher voltage. This on-board system is generally coupled to a battery, known as a traction battery, which can be used to move the vehicle in a so-called zero-emission mode of operation.

[0004] In this context, a voltage converter is used to supply the first on-board network from the second on-board network. This voltage converter is mandatory in purely electric vehicles; it is also most often found in hybrid vehicles, which still include an internal combustion engine.

[0005] The nominal voltage of this second on-board network can range from 48 volts in some cases of hybrid vehicles, up to 400 volts or even more, for some purely electric vehicles.

[0006] Furthermore, it should be noted that the primary on-board network supplies control units involved in passive and active safety functions, such as the ABS / ESP control unit or the airbag control unit. The primary on-board network also most often supplies the vehicle's signaling and exterior lighting, which contribute, among other functions, to vehicle safety.

[0007] At least for the reasons set out above, a very high availability rate is required for the voltage conversion function which supplies the first on-board network from the second on-board network.

[0008] It should also be noted that the first on-board network can be coupled to an auxiliary battery, a successor to the 12-volt battery of vehicles with a previous electrical architecture.

[0009] In the criteria and requirements relating to the availability rate required for the voltage converter function, we are interested here in the power supply required for the operation of the voltage converter, more precisely the control logic power supply and not the power supply which comes from the second on-board network.

[0010] A voltage converter such as the one described above can also be used in an on-board charger configuration, that is, in equipment that takes electrical power at one voltage as input and delivers it at another voltage as output. An on-board charger for an electric vehicle, which can connect to various charging stations, generally includes such a voltage converter.

[0011] It is known to use on the one hand the battery voltage of the first network as the first power supply of the voltage converter and on the other hand the output of the voltage converter, which is generally regulated to a voltage close to 14 volts, and to reinject the output voltage on the input side as a second power supply.

[0012] However, it turns out that, in certain degraded voltage configurations on the first on-board network, for example following a long period of storage of the vehicle without use, or a failure of the auxiliary battery of the first network, the starting of the voltage converter is not satisfactory, the converter may start in a degraded mode or the start may even fail.

[0013] In the context described above, the inventors sought to propose a solution to further improve the availability rate of the voltage converter and to address certain failures of the first on-board network.

[0014] To this end, the present invention proposes an electrical voltage conversion circuit in an electric or hybrid vehicle, for supplying a first 12-volt on-board network from a second high-voltage on-board network. The voltage conversion circuit comprises a conversion unit and at least two redundant power supplies to supply said conversion unit. The two redundant power supplies comprise a first power supply and a second power supply. The conversion unit comprises at least one internal primary power supply and a power switching block. The circuit is characterized in that the first power supply is from the first on-board network and the second power supply is from the second on-board network. first and second power sources being connected by an OR circuit to the internal power supply of the conversion unit.

[0015] Put another way, the internal power supply of the conversion unit is powered in parallel by two electrically totally independent voltage sources.

[0016] Thanks to the provisions promoted above, even if the first on-board network is in a degraded situation at the time when it is desirable to start the voltage converter, then cleverly it is a voltage that comes from the second on-board network that will compensate for the possible failure related to the first on-board network, and the start-up of the voltage converter will be able to take place under good conditions.

[0017] The term "first on-board network" refers to the on-board network commonly known as the 12-volt on-board network. This is the network with a nominal voltage of 12 volts, the voltage of which is generally between 11.5 volts and 14 volts depending on various operating parameters, including the use of charging from the main battery via the voltage converter.

[0018] The term "OR circuit" refers to a logic circuit corresponding to an OR logic similar to an OR gate. As will be seen later, several solutions are possible for implementing such an OR logic circuit.

[0019] According to one embodiment, the OR gate comprises two diodes. More precisely, the cathodes of these diodes are connected to each other and coupled to the internal power supply of the voltage converter. Consequently, this circuit is very simple; it operates passively and does not require control. A slight voltage drop is simply observed due to the presence of the circuit in relation to the diode junctions. The failure rate of such a circuit is infinitesimal.

[0020] According to an alternative embodiment, the OR circuit may include at least one controlled gate or, more generally, a two-position switch. This allows for the introduction of a priority logic, namely, favoring one of the two power sources when the gate is not controlled and switching to the other when the gate is controlled.

[0021] According to one embodiment, the first power supply provides a voltage close to 14 volts.

[0022] This value corresponds to the voltage prevailing on a conventional 12V network when the alternator driven by an internal combustion engine delivers a regulated voltage close to 14 volts. This value also corresponds to the output of the voltage converter when the voltage converter is operating and delivering voltage to the first on-board network.

[0023] In the present context, the term “neighbor” should be understood as a proximity to plus or minus 5% of the nominal value.

[0024] According to one embodiment, the second power supply provides a voltage close to 14 volts.

[0025] This value is chosen arbitrarily knowing that the switching power supply can be programmed to deliver any voltage from the high voltage supplied by the second on-board network.

[0026] According to one embodiment, the voltage delivered by the second power supply is close to, or even identical to, that of the first power supply. Advantageously, whether the internal power supply of the voltage converter is supplied by one or the other, the same voltage will prevail within the logic circuits controlling the voltage converter. When switching from one to the other, there is no voltage jump.

[0027] Furthermore, it can be provided by means of the diode OR circuit that the higher of the two voltages prevails and provides the energy to operate the control logic of the voltage converter.

[0028] According to one embodiment, the conversion unit includes one or more secondary internal floating power supplies.

[0029] A secondary internal floating power supply provides energy to the logic circuits controlling the "high-side" transistors located in the power control block, which must be in floating mode and must not be able to be coupled even indirectly with the vehicle ground.

[0030] According to one embodiment, the power switching block includes power switches and a regulation control circuit.

[0031] Among the power switches, some are "high-side" switches which must be controlled by a floating control logic.

[0032] According to one embodiment, the first on-board network has a negative reference to a structural element of the vehicle, while the second on-board network has positive and negative poles which are floating, isolated from the structural elements of the vehicle.

[0033] According to one embodiment, the second on-board network is coupled to a traction battery and the first on-board network is coupled to an auxiliary battery.

[0034] According to one embodiment, two traction battery isolation relays are provided, the second source coming from a portion of the second on-board network downstream of the isolation relays.

[0035] When the relays are open, the second on-board network does not supply the voltage converter and there is therefore no electrical consumption associated with the circuit which supplies the logic circuits of the voltage converter from the second on-board network.

[0036] However, generally, the voltage converter is only activated when the isolation relays of the attraction battery are already stuck.

[0037] It is also noted that the activation thresholds of these relays are lower than the thresholds allowing correct operation of the logic circuits of the voltage converter

[0038] The invention further relates to an electric or hybrid vehicle comprising at least one voltage conversion circuit as described above.

[0039] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: [Fig.1] illustrates, in schematic view, an example of an electrical network system in a vehicle, in which the present invention is implemented; [Fig.2] shows an example diagram of an electrical voltage conversion circuit according to the present invention.

[0040] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale.

[0041] Figure [1] illustrates an electrical distribution system in an electric vehicle.

[0042] Herein, the term electric vehicle means a vehicle equipped with an electric drivetrain capable of moving the vehicle in zero-emission mode.

[0043] Thus, in the context of this document, the term electric vehicle encompasses hybrid vehicles comprising an electric drivetrain and an internal combustion engine.

[0044] The vehicle includes a first on-board network, designated LVN, also called a low-voltage network, which is used to power a number of electrical components. This first on-board network has the vehicle chassis, or otherwise known as vehicle ground (symbol GND), as its negative reference, and the positive voltage of this first on-board network is usually in a voltage range between 10 volts and 15 volts.

[0045] In a fairly common approach, a target voltage between 13.5 volts and 14 volts will be chosen for the nominal voltage of the first LVN on-board network.

[0046] Furthermore, the vehicle may include a 12-volt battery, here called an auxiliary battery and identified as 8. The auxiliary battery 8 is connected to the low-voltage network of the LVN vehicle.

[0047] It should be noted that, for the purposes of the present invention, the presence of the auxiliary battery is optional.

[0048] The first LVN on-board network supplies control units involved in passive and active safety functions, such as the airbag control unit or the ABS / ESP control unit. The first on-board network also most often supplies the vehicle's signaling and exterior lighting, which contribute, among other functions, to vehicle safety.

[0049] Among these devices served by the first on-board network are other accessory devices such as the multimedia system (including the car radio receiving broadcast radio programs) useful to the vehicle occupants and the driver when the vehicle is parked, and charging points for portable devices.

[0050] The aforementioned equipment is electrically powered from the 12-volt low-voltage network, which is powered only by the 12-volt battery 8 when the voltage converter is inactive.

[0051] The 12-volt battery can be subjected to significant stress while the main battery (discussed later) is isolated and the voltage converter is also inactive. It is therefore understandable that the voltage of the 12-volt battery can drop and fall substantially below 12 volts.

[0052] Furthermore, the vehicle includes a traction battery, referred to as the main battery and designated 7. This main battery is also called the 'battery pack' in the industry. This component is considered to be known in itself and therefore not described in detail here.

[0053] The main battery includes a battery management computer also called in practical jargon 'BMS' (from the English Battery Management System), which contains an isolation contactor 71, 72 on each of the main positive and negative lines.

[0054] The term high voltage HVN here covers voltages from 48 volts up to more than 800 volts.

[0055] The high voltage HVN network supplies in particular an inverter 91 which controls the phases of an electric traction machine 90 under the impulses of a machine controller not shown.

[0056] The conductors 20 of the HVN high-voltage network are insulated, in particular mechanically insulated to prevent any direct or indirect contact by the action of a human operator. Furthermore, the conductors 20 of the HVN high-voltage network are arranged in a suitable electrical configuration to prevent any direct or indirect coupling with a structural element of the vehicle. Thus, the positive and negative terminals of the HVN high-voltage network are said to be 'floating'.

[0057] The traction battery can have an electrical energy storage capacity of between 1.5 kWh for hybrid vehicles and several tens of kilowatt-hours for long-range electric vehicles.

[0058] Within the framework of the present invention, a voltage conversion circuit 10 is provided to supply the first LVN on-board network from the traction battery 7.

[0059] Furthermore, in a 100% electric vehicle and in a plug-in hybrid vehicle, the main battery can be recharged from a terminal outside the vehicle via equipment called an on-board charger (not shown), assumed to be known per se, and therefore not described in detail here.

[0060] The HVN high voltage network is connected to the main battery 7 and the on-board charger (not shown).

[0061] The voltage conversion circuit 10 comprising a conversion unit 5 and two redundant power supplies to power said conversion unit.

[0062] The conversion unit 5 includes a primary internal power supply 41 and a power switching block 6. The conversion unit 5 includes one or more secondary floating internal power supplies 42.

[0063] The block identified as 4 in [Fig.2] groups together the power supplies necessary to operate the signal-type control logic, i.e. at low power, as opposed to the power switching block 6 discussed below.

[0064] The power switching block 6 is an element considered to be known in itself and therefore not described in detail here.

[0065] It should be noted that the power communication block comprises low-side power transistors connected to the negative terminal of the high-voltage on-board network and high-side transistors connected to the positive terminal of the high-voltage on-board network. In one embodiment, the gate control circuits of the transistors are floating with respect to vehicle ground, at least for the high-side transistors, but this can also be the case for the low-side power transistors.

[0066] The terms high-side and low-side are widely used in the industry; they respectively designate a transistor or switch connected to a positive voltage and a transistor or switch connected to a negative or reference voltage.

[0067] The two redundant power sources are formed by a first power source denoted 1 and a second power source denoted 2.

[0068] The first power supply 1 is provided by the first LVN onboard network via the line marked 81. The first power supply 1 provides a voltage close to 14 volts when the voltage converter is operating. It should be noted that the first power supply generally provides a lower voltage when the voltage converter is not yet operating. The voltage converter's start-up phase is then powered by the second power supply 2.

[0069] In one embodiment, the block marked 11 contains only protection elements. In other words, the voltage prevailing on the first on-board network is used almost directly.

[0070] The second power source 2 comes from the second on-board network, via the line marked 82.

[0071] The second power supply provides a voltage close to 14 volts.

[0072] As a reminder, the term "neighbor" should be understood as a proximity to within ±5% of the nominal value. However, in practice, the output voltage is regulated with greater precision.

[0073] In block 21 in [Fig.2], is shown an example of a schematic diagram which allows a voltage close to 14 volts to be delivered from a floating high voltage network.

[0074] This type of inductance-based circuit is known in itself and therefore not described in detail here; it uses inductors and switching elements. The dashed line symbolizes the coupling of the inductors, which allows for a secondary winding that is galvanically isolated from the primary.

[0075] We note that the left part is floating (between HV+ and HV-) while the right part is referenced to the vehicle mass GND.

[0076] The control logic is representative of the digital signal applied to the base of the transistor and labeled CD2. The electronics that generate this control can also be galvanically isolated from the base of the transistor to be controlled.

[0077] The first and second power supplies are connected by an OR 3 circuit to the internal power supply 41 of the conversion unit.

[0078] In the illustrated example, the OR 3 circuit comprises two diodes, a first diode 31 and a second diode 32. The cathodes of the two diodes are connected together.

[0079] The voltage drop across each diode is moderate, i.e. less than 0.6 volts.

[0080] The dashed line symbolizes the coupling of the inductors which allows for a or several secondary units galvanically isolated from the primary.

[0081] The control logic is representative of the signal at the base of the transistor and is labeled CD4. The electronics that generate this control can also be galvanically isolated from the base of the transistor to be controlled.

[0082] The secondary floating internal power supplies 42 allow the generation of voltages used by the control circuits which drive the power switching block 6. These can be, for example, voltages of +3 volts and -3 volts, +5 volts and -5 volts, +12 volts and -12 volts, +15 volts and -15 volts.

[0083] The number of secondary internal power supplies, floating or not, depends on the need for regulated voltage supply to manage the power control. This number can range from 1 to 6 in typical embodiments.

[0084] It is noted that, thanks to the proposed scheme, even if the first on-board network is in a very unfavorable state, with a voltage below 10 volts, or even below 9 volts, it is sufficient for the isolation relays 71, 72 of the traction battery 7 to close for the voltage of the second HVN network to reach the electrical voltage conversion circuit 10 (via line 82), and provide a sufficient supply voltage to the anode of diode 31. Then the control logic of the conversion unit can begin to operate normally. It is thus possible to recover from a problematic situation on the first on-board network.

[0085] It is noted that using the second power supply from the high-voltage on-board network allows the same starting sequence for the voltage converter to always be used.

[0086] Furthermore, the redundant use of the first power supply from the first on-board network coupled to the auxiliary battery makes it possible to mitigate any incident on the high-voltage on-board network, for example, an undesired failure of one of the battery isolation relays. In such an event, even if the powertrain is faulty, the vehicle's safety functions are maintained in proper working order thanks to the unimpeded operation of the voltage converter.

Claims

Demands

1. Electrical voltage conversion circuit (10) in an electric or hybrid vehicle, for supplying a first 12 Volt on-board network (LVN) from a second high-voltage on-board network (HVN), the voltage conversion circuit comprising a conversion unit (5) and at least two redundant power supplies for supplying said conversion unit, the two redundant power supplies comprising a first power supply and a second power supply, the conversion unit (5) comprising at least one primary internal power supply (41) and a power switching block (6), characterized in that the first power supply (1) is from the first on-board network and the second power supply (2) is from the second on-board network, the first and second power supplies being connected by an OR circuit (3) to the internal power supply of the conversion unit.

2. Voltage conversion circuit according to claim 1, characterized in that the OR circuit (3) comprises two diodes.

3. Voltage conversion circuit according to any one of claims 1 to 2, characterized in that the first power supply (1) provides a voltage close to 14 volts.

4. Voltage conversion circuit according to any one of claims 1 to 3, characterized in that the second power supply (2) provides a voltage close to 14 volts.

5. Voltage conversion circuit according to any one of claims 1 to 4, characterized in that the conversion unit (5) comprises one or more internal secondary floating power supplies (42).

6. Voltage conversion circuit according to any one of claims 1 to 5, characterized in that the power switching block comprises power switches (6) and a regulation control circuit.

7. Voltage conversion circuit according to any one of claims 1 to 6, characterized in that the first on-board network (LVN) has a negative reference to a structural element of the vehicle, while the second on-board network (HVN) has positive and negative poles which are floating, isolated from the structural elements of the vehicle.

8. Voltage conversion circuit according to any one of claims 1 to 7, characterized in that the second on-board network is coupled to a traction battery (7) and the first on-board network (LVN) is coupled to an auxiliary battery (8).

9. Voltage conversion circuit according to any one of claims 1 to 8, characterized in that it provides two isolation relays (71,72) of the traction battery (7), the second source coming from a portion of the second on-board network (HVN) downstream of the isolation relays.

10. Electric or hybrid vehicle comprising at least one voltage conversion circuit according to any one of claims 1 to 9.

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