Circuit arrangement for discharging at least one energy storage device charged to a high voltage

Abstract

Circuit arrangement for discharging at least one high-voltage charged energy storage device (ES) in a motor vehicle, comprising a discharge circuit (RD, TD; DC-DC1, DC-DC2) connected in parallel to the energy storage device (ES), an auxiliary microcontroller (MC1) for controlling the discharge circuit (RD, TD; DC-DC1, DC-DC2) which can be operated at a low voltage of 3-5 volts, a first voltage supply circuit (SV1) for supplying the auxiliary microcontroller (MC1) with the low voltage of 3-5 volts, which is supplied from a buffer capacitor (C_Buffer) with a voltage of 10-15 volts, and a main microcontroller (MC2) configured to control the auxiliary microcontroller (MC1) for the discharge circuit (RD, TD;to control DC-DC1,DC-DC2), wherein the buffer capacitor (C buffer) is connected for charging to a second voltage supply circuit (SV2), which is connected for operation to the permanent positive voltage terminal (KL30) in the electrical on-board voltage network of the motor vehicle, wherein the second voltage supply circuit SV2 is internally galvanically isolated.

Description

[0001] The invention relates to a circuit arrangement for discharging at least one energy storage device charged to a high voltage in a motor vehicle, with a discharge circuit that is connected in parallel to the energy storage device.

[0002] Such a circuit arrangement is known from DE 10 2016 222 632 A1. In this arrangement, before discharging the energy storage device charged to a high voltage, a short test discharge is first performed via a timer. During this test discharge, a voltage drop detector or rate detector verifies whether the energy storage device, which in this case is a DC link capacitor, is disconnected from the high-voltage battery and can therefore be discharged without the risk of excessive current flow from the high-voltage battery. Only then is a discharge carried out, controlled by the voltage drop detector. The timer and the voltage drop detector can be implemented in a microcontroller, which can be powered by a buffer capacitor charged from the energy storage device via a linear regulator.

[0003] In electric or hybrid-electric vehicles, high-voltage power lines are used to transport electrical energy from a high-voltage battery to the electric traction motor or from the charger to the high-voltage battery. These lines can carry a high DC voltage of several hundred volts. To smooth out current peaks or to provide short-term higher energy output, energy storage devices, usually in the form of intermediate storage capacitors, are connected to these high-voltage power lines. These capacitors are also charged to the high voltage.

[0004] The high-voltage battery is usually connected to the electrical circuits and the high-voltage line via switches, often referred to as contactors, with the energy storage devices on the electrical circuit side being connected to the high-voltage line.

[0005] If the vehicle is stationary for an extended period of time, undergoing inspection or repair, or in the event of an accident, the energy storage device(s) must be discharged below a touch voltage of at least 60 volts so that people are not endangered by the high voltage.

[0006] The US Federal Motor Safety Standards (FMVSS) require that capacitors on high-voltage lines be discharged to below 60 volts within 5 seconds in certain situations.

[0007] Discharge circuits require a power supply, which can be interrupted in the event of a vehicle accident, for example, if the cables of the 12-volt vehicle battery are torn. Using high voltage for the power supply leads to complex insulation requirements in the design of the discharge circuit and necessitates high-voltage-resistant, and therefore expensive, components.

[0008] The object of the invention is therefore to provide a circuit arrangement for discharging at least one energy storage device charged to a high voltage in a motor vehicle, which can be implemented in the low voltage range and still has an accident-proof voltage supply.

[0009] The problem is solved by a circuit arrangement according to claim 1. Advantageous embodiments are specified in the dependent claims.

[0010] Accordingly, a circuit arrangement according to the invention for discharging at least one energy storage device charged to a high voltage in a motor vehicle is formed with a discharge circuit which is connected in parallel to the energy storage device, with an auxiliary microcontroller for controlling the discharge circuit which can be operated with a low voltage of 3-5 volts, with a first voltage supply circuit for supplying the auxiliary microcontroller with the low voltage of 3-5 volts which is supplied from a buffer capacitor with a voltage of 10-15 volts, and with a main microcontroller which is configured to control the auxiliary microcontroller for controlling the discharge circuit.

[0011] By using an auxiliary microcontroller that can be powered by a low voltage of 3-5 volts provided by the first power supply circuit, a relatively small buffer capacitor can be used to power the first power supply circuit, while the discharge circuit can still be kept running for a required time of 5 seconds, which is sufficient to discharge the energy storage, even when the actual power supply, namely the 12-volt vehicle battery, is no longer connected.

[0012] In a first version, the discharge circuit is formed with a discharge resistor and a discharge transistor connected in series with it, whereby the auxiliary microcontroller is connected to the discharge circuit via a driver circuit.

[0013] This represents a very safe method of discharge, since the electrical energy stored in the energy storage device is converted into heat energy only via a discharge resistor, which is connected in parallel to the energy storage device via a discharge transistor connected in series with it, which can usually be done without any problems and without any additional conditions.

[0014] In an alternative second version, the discharge circuit is formed with a DC-DC converter, which is connected on the output side to a high-voltage battery and to a controlling circuit, which is connected to the auxiliary microcontroller.

[0015] This makes it advantageously possible not only to convert the electrical energy stored in the energy storage system into heat, but also to store it back in the high-voltage battery.

[0016] However, since under certain circumstances conditions may prevail in which sufficiently fast discharge by recuperation is not possible, the discharge circuit can also advantageously be formed with a discharge resistor and a discharge transistor connected in series with it, which are connected in parallel to the DC-DC converter.

[0017] This ensures a safe discharge in every case, however, without recovering the energy.

[0018] To charge the buffer capacitor for supplying the auxiliary microcontroller, it can advantageously be connected to a second power supply circuit, which is connected to the permanent positive voltage terminal (the so-called terminal 30) in the vehicle's electrical system for operation.

[0019] The buffer capacitor is charged from the vehicle's electrical system, and if the cables are intact even after an accident, the auxiliary microcontroller can also be supplied directly from the vehicle's electrical system.

[0020] In a further development of the circuit arrangement, the high potential of the high voltage is connected to a monitoring circuit, which is connected to the auxiliary microcontroller and to the main microcontroller via a galvanically decoupled line.

[0021] This allows the discharge current to be monitored by both the auxiliary microcontroller and the main microcontroller.

[0022] In an advantageous embodiment of the circuit arrangement, the control line between the main microcontroller and the auxiliary microcontroller is also galvanically isolated. Optocouplers are used in one embodiment for this purpose.

[0023] This allows for good decoupling between the low-voltage area, in which the main microcontroller has to perform other tasks, and the high-voltage area, with which the auxiliary microcontroller is connected.

[0024] In an advantageous further development, the discharge circuit can be formed with another DC-DC converter, which is connected on the output side to a low-voltage battery (terminal 30) and is connected to another controlling circuit, which is connected to the auxiliary microcontroller.

[0025] This allows the energy stored in the energy storage system to be recuperated not only into the high-voltage battery, but also into the low-voltage battery.

[0026] In an advantageous embodiment of the circuit arrangement, the discharge transistor is a IGBT (insulated gate bipolar transistor) which is connected to a driving circuit which is connected to the second power supply circuit.

[0027] The invention is explained in more detail below using exemplary embodiments and the accompanying figures. Fig. 1 a first embodiment of the circuit arrangement with a discharge circuit comprising a discharge resistor and a discharge transistor connected in series therewith, and Fig. 2 a second embodiment of the circuit arrangement with a DC-DC converter which is connected to a high-voltage battery on the output side.

[0028] The Fig. Figure 1 schematically shows an energy storage device. ES , which is connected between two high-voltage lines that carry a high potential HV_DC+ or a low potential HV_DC- have the energy storage system. ES This can be formed with one or more capacitors, which either serve as smoothing capacitors for current and voltage peaks or, if necessary, to enable a higher load current to support the high-voltage battery to which they are connected via protective switches not shown.

[0029] To discharge the energy storage device ES In the illustrated embodiment, this is the Fig. 1. The series circuit consisting of a discharge resistor RD and a discharge transistor TD , which in the illustrated embodiment is IGBT (insulated gate bipolar transistor) with a substrate diode connected in parallel. The discharge transistor TD is driven by a driver circuit TS controlled, which is supplied on the one hand from, for example, a 12 volt source and on the other hand connected to the low potential HV_DC- is connected. The driver circuit TS is in turn controlled by an auxiliary microcontroller MC1 controlled by a main microcontroller MC2 is controlled to discharge the energy storage device. ES to bring about.

[0030] The auxiliary microcontroller MC1 In the illustrated embodiment, it is supplied from a voltage supply with a low voltage value of 5 volts and its reference potential connection is also at the low potential. HV_DC- the high-voltage line, as it is galvanically connected to the high-voltage section. The control of the auxiliary microcontroller. MC1 through the main microcontroller MC2 This is done via an optocoupler and is therefore galvanically decoupled to protect the main microcontroller. MC2 to isolate from the high-voltage part of the circuit arrangement. The voltage level at the junction of the discharge transistor. TD with the discharge resistor RD is connected directly to the auxiliary microcontroller via a monitoring circuit. MC1 guided and also connected to the main microcontroller via a galvanically isolated optocoupler MC2 supplied to switch the discharge transistor on and off TD to be able to monitor.

[0031] In accordance with the invention, the supply voltage of 5 volts for the auxiliary microcontroller is MC1 from a first power supply circuit SV1 provided, which in turn is supplied by a second power supply circuit SV2 supplied with a voltage of 12 volts, which is provided via a buffer capacitor in accordance with the invention. C_puffer is supported to provide the required 5 seconds of supply voltage for the auxiliary microcontroller MC1 to be able to provide it.

[0032] The second power supply circuit SV2 It is in turn powered by the 12-volt vehicle battery and is connected to its positive terminal, the so-called permanent positive. KL30 and as a clamp 30 It is labeled and connected. Its reference potential is at the negative terminal. KL31 the vehicle battery, which acts as a terminal 31 This is referred to as the reference potential of the first power supply circuit. SV1 and also the buffer capacitor C_puffer is the low potential HV_DC- the high-voltage line, which requires that the second voltage supply circuit SV2 It should be internally galvanically isolated.

[0033] Due to the inventive design of the circuit arrangement of Fig. 1 can therefore also be used in the event that the battery cable has broken off and is thus connected to terminal 30 ( KL30 ) no voltage is applied, the auxiliary microcontroller MC1 about the first power supply circuit SV1 at least for a predetermined period of time, since the buffer capacitor C_puffer is sufficiently large to provide the necessary energy.

[0034] In the Fig. Figure 2 shows a further embodiment of a circuit arrangement according to the invention, in which identical circuit components are provided with the same reference numerals.

[0035] In contrast to the execution of the Fig. 1. An energy storage device will be used here. ES , which is between the high-voltage line potentials HV_DC+ and HV_DC- is arranged, controlled if necessary by the auxiliary microcontroller MC1 and the main microcontroller MC2 about a DC / DC-Wandler DC-DC1 discharged, but advantageously the energy stored ES The stored energy is stored back into the high-voltage battery HVBatt.

[0036] The DC / DC-Wandler DC-DC1 is controlled by a control circuit Con1 controlled in a known manner, wherein the control circuit Con1 from the auxiliary microcontroller MC1 via a control signal EN_1 is being targeted.

[0037] In a further development of such an alternative circuit arrangement, the Fig. 2 also indicated that another DC / DC-Wandler DC-DC2 It may be provided for, via which the energy storage ES into the low-voltage battery NVBatt (which is the usual 12 volt vehicle battery) can be discharged.

[0038] The further DC / DC-Wandler DC-DC2 is controlled by another control circuit Con2 controlled, which in turn is controlled by the auxiliary microcontroller MC1 via another control signal EN_2 is being targeted.

[0039] Both the high-voltage battery HVbatt and the low-voltage battery NVbatt can be controlled by the control circuit Con1 or the further control circuit Con2 via appropriate connections HV_BCN_Sense or LV_BCN_Sense must be connected to the control circuits to monitor the battery charge level. Con1 , Con2 to make it accessible in order to control the discharge into the respective batteries depending on that.

[0040] Not shown in the Fig. 2 is a further development of the circuit arrangement there by an extension including a discharge circuit according to the Fig. 1 namely the series connection of a discharge resistor and a discharge transistor in order to prevent a discharge of the energy storage device in any case where the batteries cannot be used as a backup storage device. ES to be able to bring about. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102016222632 A1

[0002]

Claims

[1] Circuit arrangement for discharging at least one energy storage device (ES) charged to a high voltage in a motor vehicle with a discharge circuit (RD, TD; DC-DC1, DC-DC2) connected in parallel to the energy storage device (ES), with an auxiliary microcontroller (MC1) for controlling the discharge circuit (RD, TD; DC-DC1, DC-DC2), which can be operated with a low voltage of 3-5 volts, with a first power supply circuit (SV1) to supply the auxiliary microcontroller (MC1) with the low voltage of 3-5 volts, which is supplied from a buffer capacitor (C_Buffer) with a voltage of 10-15 volts, and with a main microcontroller (MC2) which is configured to control the auxiliary microcontroller (MC1) to control the discharge circuit (RD, TD; DC-DC1, DC-DC2). [2] Circuit arrangement according to claim 1, wherein the discharge circuit is formed with a discharge resistor (RD) and a discharge transistor (TD) connected in series therewith, wherein the auxiliary microcontroller (MC1) is connected to the discharge circuit (RD, TD) via a driver circuit (TS). [3] Circuit arrangement according to claim 1, wherein the discharge circuit is formed with a DC-DC converter (DC-DC1) which is connected on the output side to a high voltage battery (HVBatt) and is connected to a controlling circuit (Con1) which is connected to the auxiliary microcontroller (MC1). [4] Circuit arrangement according to claim 3, wherein the discharge circuit (DC-DC1; DC-DC2) is further formed with a discharge resistor and a discharge transistor connected in series thereto, which are connected in parallel to the DC-DC converter (DC-DC1, DC-DC2). [5] Circuit arrangement according to one of the preceding claims, wherein the buffer capacitor (C_Buffer) is connected for charging to a second voltage supply circuit (SV2) which is connected for operation to the permanent positive voltage terminal (KL30) in the electrical on-board voltage network of the motor vehicle. [6] Circuit arrangement according to one of the preceding claims, wherein the high potential (HV_DC+) of the high voltage is connected to a monitoring circuit which is connected to the auxiliary microcontroller (MC1) and to the main microcontroller (MC2) via a galvanically isolated line. [7] Circuit arrangement according to one of the preceding claims, wherein the control line between the main microcontroller (MC2) and the auxiliary microcontroller (MC1) is galvanically decoupled. [8] Circuit arrangement according to one of claims 3 to 7, wherein the discharge circuit is formed with a further DC-DC converter (DC-DC2) which is connected on the output side to a low voltage battery (NVBatt) and is connected to a further controlling circuit (Con2) which is connected to the auxiliary microcontroller (MC1). [9] Circuit arrangement according to one of claims 1, 2 and 4 to 8, wherein the discharge transistor (TD) is an IGBT connected to a driving circuit (TS) which is connected to the second voltage supply circuit (SV2). [10] Circuit arrangement according to one of claims 6 to 9, wherein the galvanically decoupled lines are formed with optocouplers.

Images