Charging device with auxiliary power supply

Abstract

Charging device comprising an external AC voltage source (3) and a motor vehicle (1) with a high-voltage battery (2), wherein the motor vehicle has a low-voltage battery (4), an intermediate circuit capacitor (6) and a charging electronics unit (8) with a charging voltage input (9) and a supply voltage input (10), characterized in that - that the motor vehicle has a bidirectional auxiliary power supply (11) with two interfaces, - that the first interface (13) of the auxiliary power supply (11) and the low-voltage battery (4) are connected in parallel to the supply voltage input (10) of the charging electronics unit (8), and - that the second interface (12) of the auxiliary power supply is connected in parallel to the intermediate circuit capacitor (6) and in parallel to the charging voltage input (9) of the charging electronics unit (8).

Description

[0001] The invention relates to a charging device for electric vehicles, comprising an external AC voltage source and a motor vehicle with a high-voltage battery, wherein the motor vehicle has a low-voltage battery, an intermediate circuit capacitor and a charging electronics unit with a charging voltage input and a supply voltage input.

[0002] Electric vehicle charging systems are subject to various requirements, such as high user-friendliness, high user flexibility, and high charging capacity, which often lead to very complex and costly solutions. This also makes it more difficult to meet minimum requirements for durability, robustness, and customer availability. State-of-the-art circuits designed to limit the inrush current when a charging connection is established by plugging in a charging cable and closing contactors operate within this complex environment. For example, the inrush current can be limited by a resistor, which can be bypassed after the inrush current occurs, perhaps by switching a relay. Limiting the inrush current fulfills prescribed compliance requirements, such as...The CE marking on safety- and health-related products ensures the free movement of goods. On the other hand, such an inrush current limiting circuit results in additional losses when charging an electric vehicle, leading to a lower charging efficiency.

[0003] Various charging devices for electric vehicles are known from the prior art. For example, US document 2008 / 0316774A1 describes a power supply circuit that allows a main battery and an auxiliary battery to be charged via a single system power supply.

[0004] Document DE 693 14 089 T2 describes a power supply device which has a main battery for driving the vehicle and an auxiliary battery for accessory equipment and in which the drive power is supplied via an inverter to an AC motor for driving the wheels.

[0005] Document DE 10 2010 019 296 A1 deals with an energy supply device comprising a (a) traction battery designed to directly supply an electric drive and providing a first battery voltage, and a (b) charging battery with which the traction battery can be charged.

[0006] The document DE 102 35 489 A1 describes a power supply device, a first battery unit, a second battery unit for a lower voltage than the first battery unit, an inverting circuit, a smoothing capacitor, a DC-DC converter and an electronic control unit, wherein the inverting circuit inputs a voltage from the first battery unit through switches.

[0007] One object of the invention is to provide an improved charging device for an electric vehicle.

[0008] This problem is solved by a charging device with an auxiliary power supply according to claim 1. Advantageous embodiments and further developments of the invention are set out in the dependent claims.

[0009] According to the invention, the motor vehicle has a bidirectional auxiliary power supply with two interfaces. The second interface of the auxiliary power supply is connected in parallel to the intermediate circuit capacitor and in parallel to the charging voltage input of the charging electronics unit. The first interface of the auxiliary power supply and the low-voltage battery are connected in parallel to the supply voltage input of the charging electronics unit.

[0010] The bidirectionality of the auxiliary power supply and the circuit integration of the auxiliary power supply in the charging device offer the advantage that electrical power can be transferred via the auxiliary power supply from the electrical path of the charging device connected to the supply voltage input of the charging electronics unit to the path connected to the charging voltage input of the charging electronics unit and vice versa.

[0011] According to a preferred embodiment of the invention for charging the high-voltage battery at the external AC voltage source, the motor vehicle has a charging control unit, and a charging connection can be established between the motor vehicle and the external AC voltage source. The low-voltage battery supplies the supply voltage input of the charging electronics unit and ensures the electrical supply of the charging control unit and the auxiliary power supply via the first interface of the auxiliary power supply.

[0012] In other words, the low-voltage battery provides electrical power to the charging electronics unit and the auxiliary power supply.

[0013] It is advantageous if the auxiliary power supply charges the intermediate circuit capacitor in order to limit an inrush current into the charging electronics unit when the charging connection is established and the intermediate circuit capacitor is charged.

[0014] Limiting the inrush current by selectively charging the DC link capacitor enables compliance with product-specific safety standards, which may be required, for example, for CE marking. In addition to product safety, limiting the inrush current also has a positive effect on the reliability and longevity of the charging device.

[0015] In another embodiment, if the low-voltage battery is defective or deeply discharged and a charging connection for the high-voltage battery is established, the charging control unit can be electrically supplied via a control line from the external voltage source. The auxiliary power supply can be electrically supplied via its second interface from the external AC voltage source and feeds the supply voltage input of the charging electronics unit via its first interface.

[0016] This ensures that the vehicle's high-voltage battery can be charged via the external power supply and the charging electronics unit even if the low-voltage battery is not providing any electrical power. Although the charging electronics unit is normally powered by the low-voltage battery, the vehicle can still be charged in the event of a breakdown of the low-voltage battery. In such a case, the charging control unit and the charging electronics unit are powered by the external power supply. Therefore, charging the high-voltage battery is not dependent on the functionality of the low-voltage battery.

[0017] Furthermore, a DC-DC converter can convert the electrical voltage between the high-voltage battery and the low-voltage battery, so that the low-voltage battery can be charged via the DC-DC converter.

[0018] This design allows the low-voltage battery to be charged via the external AC power source even in the event of discharge or deep discharge. Therefore, if the vehicle's internal low-voltage supply is insufficient, both the high-voltage and low-voltage batteries can be charged. The integration of the bidirectional power supply thus contributes to the robustness of the charging device, as it ensures high availability for the customer even outside the intended operating range of the charging device. Robustness also implies that any malfunctions that occur can be rectified. In the described design, this is achieved in the case of a discharged or deeply discharged battery due to the recharging of the low-voltage battery.

[0019] The invention is based on the considerations set out below: In electric vehicles, the high-voltage battery is typically charged via a charging device with an on-board charger, which is connected to the AC mains (e.g., the household mains) via a special, standardized interface with logic and contactors. The charger is supplied with operating voltage via the vehicle's low-voltage electrical system. When the contactors close, the inrush current to the on-board charger must be limited to comply with product-specific guidelines for CE marking. Various circuits supplementing the contactors are known for this purpose, but these involve considerable technical effort and thus contribute to increased system complexity. Additional electrical losses in the vehicle's charging electronics and a reduction in the efficiency of charging the high-voltage battery are further consequences. As an improvement, an auxiliary power supply can be integrated that charges a DC link capacitor via the vehicle's low-voltage battery before the contactors close. This limits the inrush current, also known as the start-up current. In this way, CE conformity of the charging device can be achieved. If the auxiliary power supply is bidirectional and connected to the charger, a further advantage arises, which also contributes to the robustness of the charging device. In the intended exceptional case where the on-board charger cannot be powered by the low-voltage battery (e.g., due to deep discharge or a battery defect) and the DC link capacitor cannot be charged, the charger can be powered via the auxiliary power supply using the mains electricity supply. This allows the vehicle to be charged even with a depleted low-voltage battery.Additional circuitry required to ensure the high-voltage storage system can be charged when the low-voltage battery is discharged is therefore unnecessary. This allows for the implementation of a robust charging device with high availability, low susceptibility to failure, and high safety standards using a bidirectional auxiliary power supply.

[0020] A preferred embodiment of the invention is described below with reference to the accompanying drawings. Further details, preferred embodiments, and further developments of the invention will be derived from this.

[0021] In detail, schematically, it shows Fig. 1 charging device with auxiliary power supply

[0022] The Fig. Figure 1 shows a charging device for a vehicle (1) with a high-voltage battery (2). The high-voltage battery, also referred to as a high-voltage storage device, can be charged from an external AC power supply (3). For charging, the vehicle has a charging electronics unit (8) with a charging voltage input (9) and a supply voltage input (10). The charging electronics unit essentially consists of a DC-DC converter preceded by a rectifier (5). The charging electronics unit is monitored and controlled by a charging control unit (7). The charging management is implemented as software on the charging control unit. To charge the high-voltage battery, a charging connection is established between the vehicle and the external AC power supply. The AC power supply can be a single-phase network with one phase conductor (17) and a neutral conductor (14) or a three-phase network with three phase conductors and a neutral conductor.The charging connection includes a control line (20) between the charging control unit and the AC voltage source for monitoring and controlling the charging process. The charging connection also includes a contactor for each of the phase lines (19) and the neutral conductor (16) in the case of three-phase AC. The charging connection can be implemented, for example, with a charging cable and a plug-socket connection system (15, 18, 21). The supply voltage input of the charging electronics unit can be supplied by a 12-volt battery (4) in a 14-volt partial electrical system of the vehicle. This low-voltage battery can be a lead-acid battery. The low-voltage battery (4) also supplies a bidirectional auxiliary power supply (11) via a first interface (13) of the auxiliary power supply. The first interface is also connected to the supply voltage input of the charging electronics unit.The auxiliary power supply has a second interface (12) which is connected in parallel to the charging voltage input of the charging electronics unit via an intermediate circuit capacitor (6). The auxiliary power supply can, for example, be designed as a bidirectional DC-DC switching power supply. The transfer of electrical power between the high-voltage battery and the low-voltage battery is enabled by a DC-DC converter (22).

[0023] To charge the high-voltage battery, the vehicle user establishes the charging connection. The DC link capacitor is charged via the low-voltage battery and the auxiliary power supply. Only when the DC link capacitor is charged does the charging management system, via the control line, allow the contactors of the charging connection to close, thus establishing an electrically conductive connection between the charging electronics unit and the external AC voltage source. The charged DC link capacitor effectively limits a high inrush current into the charging electronics unit. This ensures the charging device's conformity with product-specific approval guidelines and technical standards, such as the CE marking directives or the IEC 60555 standard.

[0024] The bidirectional design of the auxiliary power supply also allows it to be powered via the second interface. This is particularly advantageous when the vehicle's high-voltage battery needs to be charged while the low-voltage battery is discharged or defective. In this emergency situation, which is not the charging device's normal operating state, neither the charging electronics unit's supply voltage input nor the DC link capacitor is charged. If a charging connection is established in this specific case and the contactors are closed by the charging management system, which detects the low-voltage battery's missing voltage through appropriate sensing, a high inrush current does occur. However, due to the exceptional circumstances outside the system's intended operating state, this is acceptable.On the other hand, the auxiliary power supply is fed with rectified alternating current, i.e., essentially pulsed direct current, via the second interface. The supply voltage input of the charging electronics unit is thus electrically supplied via the first interface of the auxiliary power supply. Consequently, even in the exceptional case of a defective low-voltage battery, the bidirectional nature of the auxiliary power supply ensures that the high-voltage battery can still be charged. The DC-DC converter between the high-voltage and low-voltage batteries allows the low-voltage battery to also be charged while the high-voltage battery is charging. The cause of the exceptional case, i.e., the discharge state of the low-voltage battery, can therefore be compensated for by the charging device during a charging process.

[0025] In addition to its longevity and durability, the charging device features in Fig.1. The system also boasts exceptional robustness, ensuring a high degree of reliability and customer availability for both the charging device and the vehicle. This robustness allows for user-friendly operation even in emergency or breakdown situations. The user establishes a charging connection in the same way as with a conventional charging process during normal operation to restore the vehicle's operational readiness. No additional electrical connection, such as jumper cables to another vehicle or other auxiliary power source, is required. Therefore, any connection points or poles, including reverse polarity protection devices, as known to experts from conventional combustion engine vehicles for jump-starting, are unnecessary. This simple architecture also offers cost advantages. Reference symbol list 1 vehicle 2 high-voltage batteries 3 External AC voltage source 4 low-voltage batteries 5 rectifiers 6 Intermediate circuit capacitor 7 Charging control unit 8 Charging electronics unit 9 Charging voltage input 10 Supply voltage input 11 bidirectional auxiliary power supply 12 Second interface 13 First interface 14 Neutral wire 15 Neutral wire connection 16 Contactor Neutral line 17 Phase line 18 Connection Phase Line 19 Schütz phase line 20 Control line 21 Connection control line 22 DC controllers

Claims

Charging device comprising an external AC voltage source (3) and a motor vehicle (1) with a high-voltage battery (2), wherein the motor vehicle has a low-voltage battery (4), an intermediate circuit capacitor (6) and a charging electronics unit (8) with a charging voltage input (9) and a supply voltage input (10), characterized in that: - the motor vehicle has a bidirectional auxiliary power supply (11) with two interfaces, - the first interface (13) of the auxiliary power supply (11) and the low-voltage battery (4) are connected in parallel to the supply voltage input (10) of the charging electronics unit (8), and - the second interface (12) of the auxiliary power supply is connected in parallel to the intermediate circuit capacitor (6) and in parallel to the charging voltage input (9) of the charging electronics unit (8). Charging device according to claim 1 characterized in that, for charging the high-voltage battery at the external AC voltage source, the motor vehicle has a charging control unit (7), a charging connection can be established between the motor vehicle and the external AC voltage source, the low-voltage battery supplies the supply voltage input of the charging electronics unit, the low-voltage battery electrically supplies the charging control unit, the low-voltage battery (4) electrically supplies the auxiliary power supply (11) via the first interface (13) of the auxiliary power supply (11). Charging device according to claim 2, characterized in that the auxiliary power supply charges the intermediate circuit capacitor in order to limit an inrush current into the charging electronics unit when the charging connection is established and the intermediate circuit capacitor is charged. Charging device according to one of claims 1 to 3, characterized in that, in the case of a defective or deeply discharged low-voltage battery and with a charging connection established, the charging control unit can be electrically supplied via a control line from the external voltage source, the auxiliary power supply (11) can be electrically supplied via the second interface (12) of the auxiliary power supply (11) from the external AC voltage source (3), and the auxiliary power supply (11) supplies the supply voltage input (10) of the charging electronics unit (8) via the first interface (13) of the auxiliary power supply (11). Charging device according to claim 4, characterized in that a DC converter converts the electrical voltage between the high-voltage battery and the low-voltage battery, and that the low-voltage battery is charged via the DC converter.

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