CN107959410B

CN107959410B - Circuit arrangement for precharging an intermediate circuit capacitor of a high-voltage vehicle electrical system

Info

Publication number: CN107959410B
Application number: CN201710959213.0A
Authority: CN
Inventors: C.齐瓦诺波洛斯; T.凯泽
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-10-17
Filing date: 2017-10-16
Publication date: 2022-03-15
Anticipated expiration: 2037-10-16
Also published as: CN107959410A; DE102016220273A1

Abstract

The invention relates to a circuit arrangement (1) for precharging an intermediate circuit capacitor (2) of a high-voltage vehicle electrical system (3). The circuit arrangement (1) comprises: -a linear regulator (4), -a converter (5), -a drive stage (6) and-a high-voltage MOSFET (7), wherein-the linear regulator (4) is set up for reducing a 12V battery voltage to a lower voltage, -the converter (5) is set up for converting energy of the lower voltage for controlling the drive stage (6) to an increased voltage and for dc separation, and-the drive stage (6) is set up for controlling the high-voltage MOSFET (7) to switch the intermediate loop capacitance (2).

Description

Circuit arrangement for precharging an intermediate circuit capacitor of a high-voltage vehicle electrical system

Technical Field

The invention relates to a circuit arrangement for precharging an intermediate circuit capacitor of a high-voltage vehicle electrical system. The invention relates in particular to a circuit arrangement which makes it possible to use a small number of connections and with which the switching time of a high-voltage MOSFET used for charging an intermediate circuit capacitor can be reduced.

Background

Electrification of personal private traffic is currently being driven sharply forward. In order to generate the required power (very high currents are required in the case of 12V, which would require copper cables with a practically unreasonable cross section), a significantly increased voltage level (for example 400 volts) relative to the 12 volt on-board electrical system is generally used. The intermediate circuit capacitance mediates energy between an energy storage device (e.g., a fuel cell) and one or more electric motors that function as traction motors. The traction motor is usually implemented in three phases. If the high-voltage vehicle electrical system is in operation, the grounding-side contactor is first closed, the intermediate circuit capacitor is charged to approximately 99% by means of the limited current, and only then the positive contactor is closed. In this way, wear and tear and functional impairment of the positive contactor can be reduced or avoided.

For the pre-charging of the intermediate loop capacitance, high voltage MOSFETs are typically used. In order to keep losses and heat generation low also in high-voltage MOSFETs, high-voltage MOSFETs must establish an electrical connection with as little resistance as possible very quickly. Switching times below 600 nanoseconds are desirable. Furthermore, the module for precharging must provide dc isolation between the high voltage side and the information vehicle electrical system. The main task of the commonly used high voltage MOSFET is to conduct and switch the pre-charge current. In order to enter the safe state as soon as possible after switching off the precharge current, the switching off process must be carried out as soon as possible.

US 2015/0256014 a1 discloses a circuit arrangement for switching a pre-charge current of a high-voltage vehicle electrical system. In the battery pack control device, the grounding contactor is first closed, and then the transistor with an insulated gate for controlling the high-voltage MOSFET is closed, so that the intermediate circuit capacitance is charged to 99%. Here, the precharge current is limited by an external precharge resistor. The positive battery pack contactor is then closed.

Disclosure of Invention

The aim of the invention is to enable rapid closing and opening of a high-voltage MOSFET for precharging an intermediate circuit capacitor. Here, preferably only one control signal should be required, which controls the energy transfer and activates/deactivates the high-voltage MOSFET. Furthermore, a dc isolation between the information vehicle electrical system voltage and the high-voltage vehicle electrical system voltage must be ensured. The turn-on of the high voltage MOSFET (the time for the turn-on process of the high voltage MOSFET) should be within a few nanoseconds and the turn-off (i.e., the time between deactivating the microcontroller and actually turning off the high voltage MOSFET) should be within a few microseconds.

Fast turn-on refers to the gate-source capacitance discharging as fast as possible-i.e., energy is ready for the high-voltage MOSFET. Switching off means that after deactivating the control signal/PWM signal the energy in the driver stage decreases as quickly as possible, the MOSFET is switched off and thus reaches a safe state.

The aforementioned object is achieved according to the invention by a circuit arrangement for precharging an intermediate circuit capacitor of a high-voltage vehicle electrical system. The circuit arrangement may be provided and designed for use in an electrically drivable propulsion tool. The circuit arrangement comprises a linear regulator which is designed to reduce the vehicle electrical system voltage at a normal (low) altitude to a still lower voltage. For example, the 12 volt dc voltage may be reduced to 7 volt dc voltage. The converter is designed to convert energy at a lower voltage to an increased voltage and to supply the first and second circuit components electrically connected to the high-voltage MOSFET. These two circuit components are discussed in more detail later. The converter may include one or more transformers and then at least a plurality of secondary windings. Thus, the converter may cause an effective voltage increase. The first circuit component and the second circuit component may be part of a driver stage, which is electrically connected to the converter on the secondary side. The driver stage is set up to control the high-voltage MOSFET to switch (on/off) the intermediate circuit capacitance. The high-voltage MOSFET is designed for precharging (for example to approximately 99%) the intermediate circuit capacitance after closing the ground-side contactor. The linear regulator provides a lower voltage, which is maintained in a stable manner even in the case of a disturbed vehicle electrical system and thus feeds a converter, which is in turn controlled by a Pulse Width Modulation (PWM) signal. In this way, an efficient topology for charging the intermediate circuit capacitor is provided, which is sufficient with a small number of external electrical connections. In addition, losses and wear in the high voltage MOSFET are kept small.

The dependent claims show preferred developments of the invention.

Preferably, a diode may be arranged between the source connection of the high-voltage MOSFET and the cathode of the high-voltage battery. The flow direction of the diode is directed in the direction of the negative pole of the high voltage battery. This does not exclude other elements being connected in series with the diode to the negative pole of the high voltage battery. For example, an ohmic resistor may be provided to limit the charging current. A diode for reverse polarity protection and an ohmic resistor for current limiting may be arranged in series with the intermediate circuit capacitance.

In order to increase the voltage supplied by the converter to the output side of the driver stage, two transformers can be provided in the converter, the primary windings of which are fed in parallel with one another by the linear regulator. And the secondary windings may be connected in series such that the secondary voltages of the secondary windings are summed. Depending on the voltage requirements, three or more transformers can also be arranged in a corresponding manner in the converter according to the invention, wherein the secondary voltages are all added.

The circuit arrangement can have two circuit components within the driver stage (as described above), of which the first circuit component is designed to switch on the high-voltage MOSFET or to precharge the intermediate circuit capacitance and the second circuit component is designed to accelerate the switching-off behavior. The first circuit component includes a first input terminal and a second input terminal. The first input terminal can be set up for electrical connection with a first output terminal of the converter, while the second input terminal of the first circuit component is set up for electrical connection with a second output terminal of the secondary side of the converter. The switches of the first and second current switch as well as the switches switched with voltage are likewise provided with a current limiter (for example designed as a zener diode) and an ohmic resistor, as are voltage threshold transmitters. One output terminal constitutes an output terminal of the first circuit component. The first terminals of the switch with the first current switch, the switch with the voltage switch, the voltage threshold transmitter with the current limiter and the ohmic resistor are each connected to the first input terminal. The respective first connection terminal electrically forms a node which coincides with the first input terminal. The switch of the first current switch and the voltage threshold transmitter with the current limiter are each connected to a control input of the switch of the second current switch. The first connection of the switch of the second current switch and the second connection of the ohmic resistor are connected to the control input of the switch of the voltage switch. The second connection of the switch of the second current switch is connected to the negative connection of the converter, while the second connection of the switch of the voltage switch coincides on the one hand with the output terminal and on the other hand with the control input of the switch of the first current switch. The output terminal may be connected to the gate of the high voltage MOSFET. An electrical energy store (for example in the form of an additional capacitor) may be connected between the first input terminal and the second input terminal. The capacitance can be assigned to the driver stage and/or the converter. In its function for the first circuit component, the capacitor provides an energy reserve for shortening the switching-on behavior. However, to switch off the high voltage MOSFET, the energy stored on the capacitor must drop rapidly. In this respect, according to the invention, a second circuit component is proposed as an optionally preferred addition to the driver stage. The second circuit assembly includes a third input terminal, a first energy storage with a passive discharge device, first and second switches, a second output terminal, third and fourth output terminals, a second ohmic resistance, and a third ohmic resistance. The first energy store is connected with the first connection to the third input terminal, in other words electrically connected. The first energy store is designed to supply electrical energy to the control input of the first switch. The first connection end of the first switch and the second connection end of the third ohmic resistor are electrically connected with the control connection end of the second switch. In other words, their connection ends constitute a common node. The first connection terminals of the second and third ohmic resistors are connected to the second output terminal, and the second connection terminal of the second ohmic resistor and the first connection terminal of the second switch coincide with each other. The second connection terminals of the first and second switches are located on the fourth output terminal. The third output terminal is electrically connected to the first input terminal and the fourth output terminal is electrically connected to the second input terminal. This circuit is responsible for discharging the intermediate circuit capacitance via an ohmic resistor arranged in parallel with the additional capacitance. The first energy storage of the second circuit assembly is discharged by the passive discharge device, thereby opening the first switch. The second switch is therefore closed, whereby an additional discharge of the additional capacitance via the second ohmic resistor is carried out. The switch of the second current switch of the first circuit component and the switch of the first current switch and the switch of the voltage switch of the first circuit component are opened. As a result, the high voltage MOSFET is turned off and no more pre-charge current flows into the intermediate loop capacitance.

With the invention, energy transmission through a dc voltage converter with dc separation can be provided. For this purpose, a forward converter is preferably provided, the coil of which is replaced in the secondary circuit by a resistor in the primary circuit. In this way costs can be saved. The parallel connection of two transformers in the primary loop and the series connection of transformers in the secondary loop results in a doubled voltage in the secondary loop and in an increased number of transformers in the overall system, which transformers can also be used in other modules. In the secondary loop, energy storage is achieved by a capacitor. This enables a very fast switching on of the high-voltage MOSFET, since the energy for switching the high-voltage MOSFET is stored in a capacitor and the control loop, which is preferably formed by a transistor, is qualified for a fast switching-on process. After switching off the precharge current, the high voltage MOSFET is switched off with a very short delay, so that the safe state is reached quickly.

In the prior art, a pre-charge relay is used in conjunction with a pre-charge resistor for pre-charging the intermediate circuit capacitance, whereas the pre-charge relay can be dispensed with by using the invention. This saves costs, installation space and mass.

Drawings

Embodiments of the present invention are described in detail later with reference to the drawings. In the drawings:

FIG. 1 is a strongly simplified block diagram illustrating the principle signal flow through a circuit arrangement according to one embodiment of the present invention;

FIG. 2 is a circuit diagram overview of an embodiment of a circuit arrangement according to another embodiment of the invention;

FIG. 3 is a general configuration of a DC voltage converter that may be used in accordance with the present invention;

FIG. 4 is a general configuration of a first circuit component for turning on a high voltage MOSFET according to another embodiment of the invention;

FIG. 5 is a general configuration of a second circuit component for switching off a high voltage MOSFET according to another embodiment of the invention; and

fig. 6 is a circuit diagram of a circuit arrangement according to an embodiment of the invention, in which devices are shown grouped according to the previously discussed embodiments.

Detailed Description

Fig. 1 shows a strongly simplified abstraction of a configuration according to the invention, in which the circuit arrangement 1 serves as a "black box" for controlling the high-voltage MOSFET 7. Only one single input signal is fed to the circuit arrangement 1. Only one unique output signal is output from the circuit arrangement 1 to the high-voltage MOSFET 7. Accordingly, only one control signal controls the energy transfer to the high voltage MOSFET 7. The same control signal activates and deactivates the high voltage MOSFET 7. The circuit arrangement 1 is responsible for dc isolation of the control device from the power components. Switching on can be done in a few hundred nanoseconds and switching off can be done in a few microseconds, thereby strongly reducing switching losses and excessive temperatures.

Fig. 2 shows an exemplary embodiment of a circuit arrangement 1 according to the present invention, which is fed via a supply voltage 24 (12 volt vehicle electrical system) and is controlled by microcontroller 16. The components enclosed by solid lines, linear regulator 4, converter 5, driver stage 6, control signal 13 and MOSFET 17, are functional units of circuit arrangement 1. The MOSFET 17 is connected to an electrical ground 18. The driver stage 6 is connected to the gate of a high-voltage MOSFET 7, the drain terminal of which is fed by a high-voltage battery pack 19. The gate connection of the high-voltage MOSFET 7 is connected to the output terminal as required. The source terminal is connected to the negative electrode of the high voltage battery 19 via a series circuit comprising a diode 8, an ohmic resistor 10 (current limiting resistor) and an intermediate circuit capacitor 2. The high-voltage onboard power supply system 3 is separated from the circuit arrangement 1 by a dashed line.

Fig. 3 shows a general configuration of a dc voltage converter as can be used in the circuit arrangement according to fig. 1 or 2. The voltage supply 4 feeds a converter 5, by means of which the reduced on-board system voltage can be separately transmitted to the additional capacitor C1. The diode 22 prevents the discharge of the capacitor C1 through the secondary side of the converter 5. The control of the converter 5 takes place via an ohmic resistor R1 and a MOSFET 17, wherein the MOSFET 17 is controlled by a PWM signal 13 at 500kHz and 20% duty cycle. On the primary side, the converter 5 is also connected to a demagnetization device 15. During the period in which MOSFET 17 is controlled by PWM signal 13 (approximately 20% of the operating time), therefore, current flows through converter 5 and is limited by R1. During this time, the capacitor C1 is charged (as in a forward converter). For the remaining time (about 80% of the run length), the core demagnetizes. On the secondary side the diode is turned off in order to prevent discharge of C1.

Fig. 4 shows a general configuration of the first circuit component 11 for accelerating the turn-on behavior of the high-voltage MOSFET. The high-voltage MOSFET is connected on the output side to a voltage-switched switch T3 (which is not shown here, however). On the input side, a voltage threshold transmitter D1 with a current limiter and a switch T1 and an ohmic resistor R1 of a first current switch are connected to the first input terminal. In this case, the first connection of the switch T3, which is a useful voltage switch, is also connected. The second connection of the voltage threshold transmitter D1 and of the switch T1 of the first current switch is connected to the control input of the switch T2 of the second current switch. The output of the switch T2 is connected to a second connection of the ohmic resistor R1 and to the control connection of the voltage-switched switch T3. The control of the switch T1 of the first current switch takes place via the output terminal of the first circuit component shown. In order to discharge a capacitor (not shown at present) which is an energy store for accelerating the switching-on process, if necessary, abruptly and thus switch off the high-voltage MOSFET with a short delay, an exemplary embodiment of the second circuit component is shown subsequently.

Fig. 5 shows an embodiment of a second circuit component 12 which, in the driver stage 6 of an embodiment of the device according to the invention, can be responsible for switching off the high-voltage MOSFET with a short delay. On the input side, a small energy store 21 with a passive discharge device is responsible for the control of the first switch T4. The first connection of the first switch T4 is electrically connected to the second connection of the third ohmic resistor R4 and to the control connection of the second switch T5. The first connection terminals of the third ohmic resistor R4 and the second ohmic resistor R2 are connected to the second output terminals, respectively. The second connection of the second ohmic resistor R2 and the first connection of the second switch T5 are electrically connected to each other. In this way, the ohmic resistor R2 can, with the switches T4, T5 closed, discharge the capacitor C1 very quickly and thus lead to an acceleration of the switching-off behavior of a high-voltage MOSFET (not shown) which is connected to a circuit component (see fig. 4) arranged on the other side of the capacitor C1 for accelerating the switching-on behavior.

Fig. 6 shows a circuit arrangement for implementing the circuit arrangement 1 according to the invention, wherein all components contained in the previously discussed figures are shown and are shown in an exemplary context for implementation in a circuit arrangement. The components are known per se to the expert, so that a detailed explanation can be dispensed with. The circuit arrangement 1 serves to activate a precharging process of an intermediate circuit capacitor (not shown), which can be connected on the output side to a high-voltage MOSFET 7 and a diode 8. The method is performed after closing the negative main relay but before closing the positive main relay. The charging current switched on by the high-voltage MOSFET 7 is limited by an ohmic series resistor (also not shown). The rise time of the gate-source voltage of the high voltage MOSFET 7 must be limited to below 600 nanoseconds in order to sufficiently limit the switching losses that occur. The gate-source voltage of the high voltage MOSFET 7 is controlled by a current transformer 14. Furthermore, the converter 14 with the converter 5 is responsible for the dc isolation between the low-voltage side and the high-voltage side. The linear regulator 4 is set up to generate a stable output voltage which supplies the circuit arrangement 1 shown with power. The converter 14 is controlled by a PWM signal PRCHRG _ CTRL. The input signal source 13 is a control device for the switch 17. The PWM signal activates or deactivates the switch 17 if the signal ABE _ HTO _ LEVEL 2 of the input signal source 13 has a high voltage (high LEVEL). If the switch 17 is closed, a current flows through the transformers (primary side) arranged in parallel with each other. This current is limited by ohmic resistors R8 arranged in parallel with each other in the example (wherein separate power resistors may also be used). The magnetic flux through the converter 5 increases with the primary current, whereby magnetic energy is stored in the converter 5. By the serial connection of the secondary side coils of the converter 5, the voltage is doubled to twice as high as on the primary side. The energy of the converter 5 is transferred to the secondary side, in response to which a current flows through the

diode pair

22, 23. If the switch 17 is open, the current and therefore the energy remaining in the converter 5 is run through the demagnetization component 15 and its freewheeling diode. This results in a negative voltage on the secondary side. However, the respective current flow on the secondary side is prevented by the

diodes

22 and 23.

When the high-voltage MOSFET 7 is switched on, a current is supplied by the converter 14, whose energy charges the capacitors C1 and C3 via the converter 5, wherein the ohmic resistor R6 limits the current flow into the capacitor C3. This causes the first switch T4 to close (with ohmic resistor R4 limiting the current) and the second switch T5 to open. With each switching-on process of the PWM signal on the primary side, a capacitor C1 (having a self-discharging resistance via an ohmic resistor R7) is charged, which capacitor C1 is the main energy store of the driver stage 6. Once the breakdown voltage of diode D1 is reached, capacitor C2 of switch T2 of the second current switch is charged. Subsequently, the switch T2 of the second current switch is closed, and then the current flows through the ohmic resistor R and the switch T3 of the voltage switch is likewise closed. This is followed by the activation of the switch T1 of the first current switch, whereby the base-emitter voltage over the switch T2 of the second current switch stabilizes. In this case, switch T2 of the second current switch is saturated and, correspondingly, switch T3 of the voltage switch is also saturated. This results in a large current from the capacitor C1 which immediately charges the gate capacitance of the high volt MOSFET 7. This results in a sharp turn-on of the high voltage MOSFET.

At switch-off, the capacitor C1 discharges slowly through the ohmic resistor R7. The capacitor C2 discharges slowly through the ohmic resistor R5. The capacitor C3 discharges through the ohmic resistor R3 and the first switch T4 is then closed. This results in a high potential at the base of the second switch T5. Once the second switch T5 is closed, the capacitor C1 discharges through a parallel ohmic (or separate power resistor) resistor R2. The base emitter voltage on the switch T2 of the second current switch drops and then the switch T1 of the first current switch, the switch T2 of the second current switch and the switch T3 of the voltage switch are opened. The high voltage MOSFET 7 is then switched off and no further precharge current flows into the intermediate loop capacitance.

Claims

1. Circuit arrangement (1) for precharging an intermediate circuit capacitance (2) of a high-voltage vehicle electrical system (3), comprising:

-a linear regulator (4),

-a converter (5),

-a drive stage (6) and

-a high voltage MOSFET (7), wherein the output terminal of the linear regulator (4) is connected with the input terminal of the converter (5) and the output terminal of the converter (5) is connected with the input terminal of the driver stage (6), wherein

The linear regulator (4) is set up to reduce the 12V battery voltage to a lower voltage,

the converter (5) is designed to convert a lower voltage for controlling the driver stage (6) to an increased voltage and to perform a DC separation,

-the driver stage (6) is set up for controlling the high-voltage MOSFET (7) to switch the intermediate circuit capacitance (2),

wherein the driver stage (6) further has a first circuit component (11) for switching on the high-voltage MOSFET (7) for precharging an intermediate circuit capacitance (2) of a high-voltage vehicle electrical system (3) and the first circuit component (11) comprises:

-a first input terminal for receiving a first input signal,

-a second input terminal for receiving a second input signal,

-a switch (T1) of a first current switching type,

-a switch (T2) of a second current switching type,

-a switch (T3) of the voltage switching type,

-a voltage threshold generator (D1) with a current limiter,

-ohmic resistance (R1), and

-an output terminal, wherein

-a first connection of a switch of the first current switch type (T1), a first connection of a switch of the voltage switch type (T3), a first connection of a voltage threshold generator with current limiter (D1) and a first connection of an ohmic resistor (R1) are connected to the first input terminal, respectively,

-a second connection of the switch (T1) of the first current switch type and a second connection of the voltage threshold generator (D1) with current limiter are connected to the control input of the switch (T2) of the second current switch type,

-a first connection of a switch (T2) of the second current switching type and a second connection of an ohmic resistor (R1) are connected to a control input of a switch (T3) of the voltage switching type,

-a second connection of the switch (T2) of the second current switch type is connected to electrical ground,

-a second connection of the switch (T3) of the voltage switching type is connected on the one hand to the output terminal and on the other hand to a control input of the switch (T1) of the first current switching type,

wherein the first input terminal is set up for electrical connection with a first output terminal of the converter, wherein the second input terminal of the first circuit component is set up for electrical connection with a second output terminal of the secondary side of the converter and wherein the output terminal is connected with the gate of the high-voltage MOSFET.

2. The circuit arrangement of claim 1, further comprising:

-a diode (8) arranged with the flow direction pointing to the negative ground between the source connection of the high-voltage MOSFET (7) and the negative pole of a high-voltage battery pack provided for charging the intermediate circuit capacitance (2).

3. Circuit arrangement according to claim 2, wherein the diode (8) is arranged in series with the intermediate circuit capacitance (2).

4. A circuit arrangement as claimed in claim 2 or 3, further comprising an ohmic resistor (10) in series with the diode.

5. The circuit arrangement of one of claims 1 to 3, further comprising:

-a negative contactor, and

-a positive contactor, wherein the converter (5) is further set up for closing the high-voltage MOSFET (7) after closing the negative contactor and before closing the positive contactor.

6. Circuit arrangement according to one of claims 1 to 3, wherein the converter (5) has two transformers connected in parallel on the primary side and connected in series on the secondary side.

7. Circuit arrangement according to one of claims 1 to 3, wherein a capacitance (C1) and/or an ohmic resistance (R7) is further connected between the first input terminal and the second input terminal.

8. A circuit arrangement as claimed in one of claims 1 to 3, wherein the driver stage (6) further has a second circuit component (12) comprising:

-a third input terminal for receiving a third input signal,

-a first energy storage (C3) with a passive discharge device (R3),

-a first switch (T4),

-a second switch (T5),

-a second output terminal for outputting a second output signal,

-a fourth output terminal for outputting a fourth output signal,

-a second ohmic resistance (R2) and

-a third ohmic resistance (R4), wherein

A first energy store (C3) is connected with a first connection at a node between the passive discharge device (R3) and the resistor (R6) and is set up to supply energy to the control input of the first switch (T4), wherein further connections of the passive discharge device (R3) and the resistor (R6) are connected with a second connection and a third input of the first energy store, respectively, wherein the second connection of the first energy store is connected with a fourth output,

-a first connection of the first switch (T4) and a second connection of the third ohmic resistor (R4) are connected to a control connection of the second switch (T5),

the first connection terminals of the second (R2) and third (R4) ohmic resistors are each connected to the second output terminal,

-the second connection of the second ohmic resistor (R2) and the first connection of the second switch (T5) are connected to each other,

second connections of the first switch (T4) and of the second switch (T5) are each connected to a fourth output terminal,

the second output terminal is connected to the first input terminal, and

the fourth output terminal is connected with the second input terminal,

wherein the third input terminal is electrically connected to the first output terminal of the converter, wherein the third input terminal is connected to the second output terminal.

9. Circuit arrangement (1) according to one of claims 1 to 3, wherein the circuit arrangement (1) is set up for controlling the converter (5) by means of a PWM signal.