DC / DC converter for a motor vehicle, vehicle electrical system and motor vehicle with a DC / DC converter

Abstract

The invention relates to a DC voltage converter (1) for a motor vehicle for converting a high-voltage voltage output by a high-voltage storage device (S) into a low-voltage voltage for supplying a low-voltage electrical system (N) of the motor vehicle, wherein the DC voltage converter (1) comprises: - a control unit (2) configured to control a converter unit (3) such that the converter unit (3) converts the high-voltage voltage into the low-voltage voltage for supplying the low-voltage vehicle electrical system (N); and - an internal power supply unit (4) which is connected to the high-voltage voltage and supplies the control unit (2) with electrical energy for controlling the converter unit (3); wherein the internal power supply unit (4) is set up to supply the low-voltage electrical system (N) with a supply voltage in an operating state in which the converter unit (3) is not controlled.

Description

[0001] The invention relates to a DC / DC converter for a motor vehicle, in particular a DC / DC converter that is intended to be installed in the motor vehicle and converts a high-voltage voltage from a high-voltage storage device into a low-voltage voltage for supplying an on-board electrical system. The invention further relates to an on-board electrical system and a motor vehicle with such a DC / DC converter.

[0002] DC / DC converters are a well-known technology used in the state of the art, particularly in partially electric vehicles, hybrid vehicles, and fully electric vehicles, to convert high-voltage to low-voltage. The high-voltage source is typically a high-voltage battery that powers the vehicle's electric drive unit while driving. The resulting low-voltage output supplies various electrical consumers with power via the vehicle's low-voltage electrical system.

[0003] When a vehicle is not in operation, it is necessary to supply the low-voltage electrical system with at least a small amount of electrical energy so that electrical consumers, such as those required for unlocking and starting the vehicle, can function. A DC / DC converter is poorly suited to providing this small amount of electrical energy because its efficiency is very low in the relevant current ranges.

[0004] For this reason, current technology employs a low-voltage battery or an additional micro DC / DC converter, which—specifically for this function—efficiently converts the high-voltage voltage for the minor power supply of the low-voltage electrical system. Both solutions are suboptimal, as they require additional components that are undesirable, at least for environmental and / or cost reasons.

[0005] Against this background, the object of the invention is to create a DC / DC converter that efficiently supplies the low-voltage electrical system in states where the vehicle is being operated or not. At the very least, the object of the invention is to provide an alternative to the prior art.

[0006] This problem(s) is solved by a DC-DC converter according to claim 1. Preferred embodiments are the subject of the dependent claims.

[0007] A DC / DC converter according to the invention for a motor vehicle for converting a high-voltage voltage output by a high-voltage storage device into a low-voltage voltage for supplying a low-voltage electrical system of the motor vehicle has in particular the following features: - Input connections for connecting the DC-DC converter to the high-voltage storage system and output connections for connecting the DC-DC converter to the low-voltage vehicle electrical system; - a control unit configured to control a converter unit when a high-voltage storage device is connected to the input terminals and a low-voltage electrical system is connected to the output terminals, such that the converter unit converts the high-voltage voltage into the low-voltage voltage to supply the low-voltage electrical system; and an internal power supply unit which, when a high-voltage storage device is connected to the input terminals, is connected to the high-voltage voltage and supplies the control unit with electrical energy to control the converter unit; wherein, when a high-voltage storage device is connected to the input terminals and a low-voltage electrical system is connected to the output terminals, the internal power supply unit is configured to supply the low-voltage electrical system with a supply voltage in an operating state in which the converter unit is not controlled.

[0008] The DC-DC converter according to the invention is intended to be connected to the high-voltage battery of the motor vehicle and the low-voltage electrical system of the motor vehicle. For this purpose, the DC-DC converter has, in particular, the corresponding input and output connections, which are preferably integrated into a housing of the DC-DC converter. The input connections are high-voltage input connections and the output connections are low-voltage input connections.

[0009] The high-voltage storage device is preferably an electrochemical energy storage device, wherein the supplied high-voltage voltage is preferably 400V or 800V, but can also be higher values; the DC-DC converter is designed and dimensioned for the corresponding voltage level of the high-voltage system. In addition to supplying the DC-DC converter, the high-voltage storage device preferably also supplies the electric drive unit of the motor vehicle.

[0010] Preferably, all components of the DC-DC converter mentioned and subsequently described as preferred are integrated into the housing, so that the DC-DC converter forms a self-contained unit.

[0011] The supply voltage can be the same value as the low-voltage voltage, or preferably lower or higher.

[0012] The control unit preferably comprises a microcontroller and a gate driver, wherein the converter unit has at least one switch, in particular a semiconductor switch, which the microcontroller controls via the gate driver for the operation of the converter unit.

[0013] Preferably, the DC voltage converter is designed such that the operating state in which the converter unit is not controlled corresponds to a sleep / standby mode in which the motor vehicle is not operated.

[0014] The DC-DC converter, for example, has a signal input through which it receives a signal indicating the sleep / standby mode, whereby upon receiving this signal, the DC-DC converter terminates the control of the converter unit and the internal power supply unit takes over the supply of the low-voltage vehicle electrical system.

[0015] The internal power supply unit can preferably be designed in such a way that it always applies the supply voltage to the low-voltage on-board power supply and takes over the supply voltage when the low-voltage voltage drops.

[0016] In particular, with a high-voltage storage device connected to the input terminals and a low-voltage electrical system connected to the output terminals, the supply voltage can be lower than the low-voltage voltage, with the internal power supply unit being connected to the low-voltage electrical system via a blocking element in such a way that the low-voltage voltage cannot generate a current flow into the internal power supply unit.

[0017] In this case, the supply voltage takes over the supply of the low-voltage electrical system if the low-voltage voltage drops below the supply voltage. Conversely, if the low-voltage voltage subsequently exceeds the supply voltage again, namely when the control unit begins controlling the converter unit, the low-voltage voltage takes over the supply of the low-voltage electrical system.

[0018] The blocking element serves to protect the internal power supply unit by preventing unwanted current flow into it. Preferably, the blocking element is a diode or a semiconductor switch.

[0019] Preferably, the converter unit is designed in such a way that it galvanically isolates the low-voltage vehicle electrical system from the high-voltage voltage, wherein the internal power supply unit is a micro-DC / DC converter.

[0020] Furthermore, the converter unit is preferably configured to generate a current flow in the ampere range in the low-voltage electrical system when controlled by the control unit, and the internal power supply unit is configured to generate a current flow in the milliampere range in the low-voltage electrical system when the converter unit is not operating.

[0021] The invention further relates to an on-board electrical system for a motor vehicle, comprising a high-voltage storage device and a low-voltage on-board electrical system as well as a previously described DC-DC converter, wherein the DC-DC converter is electrically connected to the high-voltage storage device via its input terminals and to the low-voltage on-board electrical system of the motor vehicle via its output terminals and is configured to convert a high-voltage voltage provided by the high-voltage storage device into a low-voltage voltage for supplying the low-voltage on-board electrical system.

[0022] The invention also relates to a motor vehicle which has the DC voltage converter according to the invention, which is electrically connected via its input terminals to a high-voltage storage device of the motor vehicle and via its output terminals to a low-voltage electrical system of the motor vehicle and is configured to convert a high-voltage voltage provided by the high-voltage storage device into a low-voltage voltage for supplying the low-voltage electrical system.

[0023] A preferred embodiment of the DC / DC converter according to the invention is explained below with reference to the accompanying figure.

[0024] The Fig. Figure 1 shows a schematic block diagram of the DC / DC converter according to the preferred embodiment of the invention.

[0025] The figure shows a preferred embodiment of a DC voltage converter 1 according to the invention.

[0026] The DC-DC converter 1 includes a housing 10 in which the corresponding components described below are contained. The components are, for example, arranged together on a circuit board.

[0027] The housing 10 has input terminals 11, via which the DC-DC converter 1 can be connected to a high-voltage storage device S of a (not shown) motor vehicle as intended. The high-voltage storage device S preferably also supplies the electric drive unit of the motor vehicle.

[0028] In addition, the housing has 10 output terminals 12, via which the DC voltage converter 1 can be connected to a low-voltage electrical system N of the motor vehicle.

[0029] A schematically represented load L is connected to the low-voltage electrical system N, where the load L can be a typical consumer present in the motor vehicle, such as seat heating, power steering, windscreen wipers, entertainment / navigation devices, etc.

[0030] The high-voltage storage unit S connected to the input terminals 11 supplies a high-voltage voltage HV+, for example of 400V, 800V or more.

[0031] The DC-DC converter 1 converts the high-voltage voltage into a low-voltage voltage, which it outputs to the low-voltage electrical system N at the output terminals 12. The output low-voltage voltage LV+ is, for example, 12V, 24V, or 48V.

[0032] The DC-DC converter 1 has a control unit 2 housed within the casing, which is configured to control a converter unit 3 such that the converter unit 3 converts the high-voltage voltage of the high-voltage storage device S into the low-voltage voltage for supplying the low-voltage electrical system N. The converter unit 3 is, in particular, a switched converter unit 3, which has at least one switch, preferably a semiconductor switch, and other power components, wherein the control unit 2 controls the switches of the converter unit 3 such that the aforementioned voltage conversion takes place.

[0033] Preferably, the converter unit 3 includes a cooling system (not shown) which prevents the temperature of the converter unit 3 from exceeding, for example, 65°C during operation.

[0034] Preferably, the converter unit 3 is connected to the high-voltage storage device S via a DC link circuit 6, which serves to stabilize the high-voltage voltage. Furthermore, the converter unit 3 is preferably designed to galvanically isolate the low-voltage electrical system N from the high-voltage storage device S.

[0035] The control unit 2 includes a logic circuit 20, for example a microcontroller, and a gate driver 21. The logic circuit 20 controls the at least one switch of the converter unit 3 via the gate driver 21, so that the converter unit 3 performs the aforementioned conversion of the high-voltage voltage into the low-voltage voltage.

[0036] The invention is not limited to the specific construction of the control unit 2 and the converter unit 3.

[0037] An internal power supply unit 4 of the DC-DC converter 1 is connected within the housing 10 such that it is connected to the high-voltage storage device S, with the high-voltage voltage supplied by this high-voltage storage device S supplying the internal power supply unit 4. The internal power supply unit 4 is specifically connected to the high-voltage storage device S in parallel with the DC link circuit 6 or the converter unit 3.

[0038] The internal power supply unit 4 preferably includes a micro DC / DC converter 41, which converts the high-voltage voltage of the high-voltage storage device S into a supply voltage, which is also a DC voltage. The internal power supply unit 4 supplies the resulting supply voltage to the logic circuit 20 and the gate driver, enabling them to operate.

[0039] When the motor vehicle equipped with the DC-DC converter 1 is operated, for example when a user activates the ignition or start button, the logic circuit 20 receives a corresponding signal. This signal is received, for example, from a control unit of the motor vehicle. The logic circuit 20 then controls the converter unit 3 via the gate driver 21 such that the converter unit 3 starts operating and converts the high-voltage voltage into the low-voltage voltage, thereby supplying the low-voltage electrical system N with electrical energy.

[0040] The low-voltage voltage is, for example, 14V. Depending on the number of consumers connected to the low-voltage electrical system N, or the resulting load L, the current flowing through the low-voltage electrical system N can reach high amperage ranges, for example, 200A. The converter unit 3 is specifically designed to deliver this electrical power in the kW range.

[0041] If, however, the vehicle is not in operation, for example when parked and in a sleep / standby mode, the control unit 2 does not activate the converter unit 3. In this case, the converter unit 3 does not output the low-voltage voltage and therefore does not supply the low-voltage vehicle electrical system N with electrical energy.

[0042] However, it is necessary that the low-voltage electrical system (N) is also supplied with electrical energy in this operating state so that essential consumers, such as those required to start the vehicle, continue to operate. The current required for this is much lower than when the vehicle is running. For example, the currents in the low-voltage electrical system (N) for supplying the necessary consumers are in the milliampere range, for example, around 200 mA.

[0043] The internal power supply unit is designed for the required electrical power range.

[0044] According to the invention, the internal energy supply unit 4 is dimensioned and interconnected in such a way that it can also perform this function when the motor vehicle is not in operation.

[0045] For this purpose, the internal power supply unit 4 is additionally connected to the low-voltage electrical system N, preferably via a blocking element 5. The internal power supply unit 4 generates the supply voltage already described, which it delivers to the low-voltage electrical system N via the blocking element 5.

[0046] The supply voltage generated by the internal power supply unit 4 can have the same value (14 V) as the low-voltage voltage generated or output by the converter unit 3 when controlled by the control unit 2. In this case, the blocking element 5 is not necessary.

[0047] However, the supply voltage generated by the internal power supply unit 4 can preferably be lower than the low-voltage voltage. For example, the supply voltage can be on the order of 10V.

[0048] This lower supply voltage level means that when the vehicle is started and the converter unit 3, controlled by the control unit 2, begins operating, the low-voltage voltage output by the converter unit 3 exceeds the supply voltage generated by the internal power supply unit 4, thus rendering the supply voltage in the low-voltage electrical system N ineffective. The blocking element 5, preferably a diode, blocks the current flow into the internal power supply unit in this case and protects it from damage.

[0049] The blocking element 5 can also be provided in case the low-voltage voltage is equal to or lower than the supply voltage.

[0050] In light of the above explanations, it is evident that the invention provides a DC / DC converter 1 which, due to the dual function of the internal power supply unit 4 - namely the supply of the control unit 2 and the supply of the low-voltage vehicle electrical system N when the vehicle is not in operation - eliminates the need for additional components such as a low-voltage battery or an additional micro DC / DC converter.

[0051] The statements preceding the figure description apply equally to the embodiment and vice versa.

Claims

[1] DC-DC converter (1) for a motor vehicle for converting a high-voltage voltage output by a high-voltage storage device (S) into a low-voltage voltage for supplying a low-voltage electrical system (N) of the motor vehicle, wherein the DC-DC converter (1) comprises: - Input terminals (11) for connecting the DC-DC converter (1) to the high-voltage storage (S) and output terminals (12) for connecting the DC-DC converter (1) to the low-voltage electrical system (N); - a control unit (2) configured, when a high-voltage storage device (S) is connected to the input terminals (11) and a low-voltage electrical system (N) is connected to the output terminals (12), to control a converter unit (3) such that the converter unit (3) converts the high-voltage voltage into the low-voltage voltage to supply the low-voltage electrical system (N); and - an internal power supply unit (4) which, when a high-voltage storage device (S) is connected to the input terminals (11), is connected to the high-voltage voltage and supplies the control unit (2) with electrical energy for controlling the converter unit (3); wherein The internal power supply unit (4) is further configured to supply the low-voltage electrical system (N) with a supply voltage when the high-voltage storage unit (S) is connected to the input terminals (11) and the low-voltage electrical system (N) is connected to the output terminals (12) in an operating state in which the converter unit (3) is not controlled. [2] DC voltage converter (1) according to claim 1, wherein the operating state in which the converter unit (3) is not controlled corresponds to a sleep / standby mode in which the motor vehicle is not operated. [3] DC-DC converter (1) according to claim 1 or 2, wherein, with a high-voltage storage device (S) connected to the input terminals (11) and a low-voltage electrical system (N) connected to the output terminals (12), the supply voltage is lower than the low-voltage voltage and the internal power supply unit (4) is connected to the low-voltage electrical system (N) via a blocking element (5) of the DC-DC converter (1) such that the low-voltage voltage cannot generate a current flow into the internal power supply unit (4). [4] DC voltage converter (1) according to claim 3, wherein the blocking element (5) is a diode or a semiconductor switch. [5] DC / DC converter (1) according to any one of the preceding claims 1 to 4, wherein the converter unit (3) is constructed in such a way that it galvanically isolates the low-voltage on-board power supply (N) from the high-voltage voltage and the internal power supply unit (4) is a micro DC / DC converter. [6] DC voltage converter (1) according to any one of the preceding claims 1 to 5, wherein the converter unit (3) is configured to generate a current flow in the ampere range in the low-voltage electrical system (N) when controlled by the control unit (2), and the internal power supply unit (4) is set up to generate a current flow in the milliampere range in the low voltage electrical system (N) in the operating state in which the converter unit (3) is not operating. [7] On-board electrical system for a motor vehicle, comprising - a high-voltage storage device (S), - a low-voltage electrical system (N), as well as - a DC-DC converter (1) according to one of the preceding claims, wherein the DC-DC converter (1) is electrically connected to the high-voltage storage device (S) via its input terminals (11) and to the low-voltage electrical system (N) via its output terminals (12) and is configured to convert a high-voltage voltage output by the high-voltage storage device (S) into a low-voltage voltage for supplying the low-voltage electrical system (N). [8] motor vehicle, comprising - a high-voltage storage device (S), - a low-voltage electrical system (N), as well as - a DC voltage converter (1) according to one of claims 1 to 6, wherein the DC voltage converter (1) is electrically connected to the high-voltage storage device (S) via its input terminals (11) and to the low-voltage electrical system (N) via its output terminals (12) and is configured to convert a high-voltage voltage output by the high-voltage storage device (S) into a low-voltage voltage for supplying the low-voltage electrical system (N).

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