Pre-charging switch and power supply arrangement and method for connecting a load to a DC voltage source

Abstract

The invention relates to a pre-charging switch arrangement (1) for charging a capacitor (C) of a DC circuit (7), comprising a pre-charging resistor (R V ) and the precharge switch (S V The invention further relates to a power supply arrangement (5) for an electrical load and to a method for connecting a load to a high DC voltage source (B). In order to provide a pre-charging switch arrangement by means of which a capacitor can be charged, the charge state of the capacitor can be detected and which ensures the greatest possible level of reliability, it is provided according to the invention that a pre-charging resistor is at least indirectly connected to the device (3) for detecting the voltage across the resistor (U V ). For the power supply arrangement, there is a pre-charge switch arrangement according to the invention, connected in parallel with the controllable switch elements (S1, S2). For the above method, the load is connected to the high DC voltage source depending on the voltage across the pre-charge resistor, the pre-charge resistor being arranged between the high DC voltage source and the load.

Description

[0001] This application is a divisional application of the invention patent application with application number 201580010987.8, application date February 26, 2015, and invention name "Pre-charging switch arrangement, power supply arrangement and method for connecting a load to a high DC voltage source". Technical Field

[0002] The invention relates to a pre-charging switch arrangement for charging a capacitor of a DC circuit, having a pre-charging resistor and a pre-charging switch. The invention also relates to a power supply arrangement for an electrical load, the load being a capacitor on the input side, having a supply current circuit connecting a high voltage source to the capacitor and having two controllable switching elements, each of which is arranged between a pole of the capacitor and the high voltage source. The invention also relates to a method for connecting a load to a high DC voltage source. Background Art

[0003] Pre-charging switch arrangements for DC circuits are known. They are used in particular in high-voltage DC circuits in which the load is intended to be connected to a power supply. In particular in DC circuits in which the load is a capacitor on the input side. Conventional applications include, for example, "battery disconnect units (BDUs)" in electric or hybrid drives of vehicles. Such drives usually have a high-voltage battery that is connected to the on-board network, in particular to an inverter, for supplying the required alternating current or three-phase current voltage to the drive unit. For safety reasons, such a device has two controllable switching elements, one for each pole. These switching elements can be, for example, contactors or relays.

[0004] If, in such a DC circuit, the DC source is directly connected to an uncharged capacitor, a short-circuit current may flow briefly and may cause damage to the components. For this purpose, the capacitor is precharged before it is fully connected to the DC voltage source. To this end, the precharge switch arrangement is connected in parallel to one of the two controllable switch elements. In order to precharge the capacitor, the other controllable switch element and the precharge switch are then closed. The capacitor is thus charged by means of a precharge resistor. If the capacitor has reached the desired charge state, the controllable switch element connected in parallel with the precharge switch arrangement is also closed and the load is connected to the DC voltage source. The precharge switch can then be disconnected again.

[0005] In order to monitor the charge state of the capacitor, the voltage of the capacitor across the disconnected controllable switch element is usually tapped and evaluated. This voltage can provide information about the charge state of the capacitor. This type of voltage measurement requires complex isolation of the high voltage line from the electronic control system, which may exist and which evaluates the voltage and generates a control signal for switching the controllable switch element. In addition, the current blocking between the two sides of the controllable switch element is therefore not ensured in a reliable manner. In the known prior art, auxiliary relays are often used for current blocking. This solution makes the pre-charge switch arrangement complex and costly. Summary of the invention

[0006] It is therefore an object of the present invention to provide a pre-charging switch arrangement, a power supply arrangement and a method for connecting a load to a high DC voltage source, which can reliably detect the charge state of the capacitor, ensure a high reliability level and additionally enable at least the pre-charging switch arrangement to be a compact structure.

[0007] According to the invention, the object for a pre-charging switch arrangement is achieved in that the pre-charging resistor is at least indirectly connected to a device for detecting the voltage across the pre-charging resistor. For a power supply arrangement, the object according to the invention is achieved in that the pre-charging switch arrangement according to the invention is connected in parallel with one of the two controllable switching elements. For the method for connecting a load to a high DC voltage source mentioned in the introduction, the object according to the invention is achieved in that the load is connected to the high DC voltage source depending on the voltage across the pre-charging resistor, which is arranged between the high DC voltage source and the load.

[0008] The present invention provides the following advantages, the voltage to be detected can be tapped at the pre-charge resistor without being tapped at one of the controllable switch elements. When the pre-charge switch is disconnected, after the pre-charge operation is terminated, at least the connection for detecting the voltage is no longer combined with the capacitor in the current-carrying circuit between the on-board power supply network and the high voltage source. Since the voltage to be measured is not tapped at all two sides of one of the controllable switch elements, each of the two sides of the controllable switch element is completely current-blocked when the switch element is disconnected. The use of auxiliary relays can therefore be omitted. Another advantage is that the same voltage can be tapped at the pre-charge resistor as at the controllable switch element (which is connected in parallel). The present invention therefore allows the charging of the capacitor and the detection of the voltage (to determine the charge state of the capacitor) to be performed more reliably, and the need for complex isolation from the high-voltage circuit of the electronic control system can be reduced.

[0009] The solution according to the invention can be further improved by means of various embodiments, each of which is advantageous in itself and which can be freely combined with one another. These embodiments and the advantages associated therewith are discussed below.

[0010] The pre-charging switch may in particular be a contactor or a relay. These components are known and can be used with a high reliability level for switching high voltages or currents.

[0011] In order to reduce the voltage tapped at the pre-charge resistor, the device for detecting the voltage across the pre-charge resistor may have a first voltage divider, which is connected to the pre-charge resistor at the input side. The voltage divider can then provide a voltage proportional to the voltage across the pre-charge resistor. This can be particularly advantageous to protect the device from damage by detecting excessively high voltages. The first voltage divider may have two inputs connected at both ends of the pre-charge resistor.

[0012] The pre-charging switch arrangement can have exactly two high-voltage connections, between which the input of the first voltage divider, the pre-charging resistor and both connections of the pre-charging switch are arranged on a common line section. This makes it possible to achieve a particularly compact pre-charging switch arrangement, which can also be integrated in an existing high-voltage DC circuit in a particularly simple manner.

[0013] The device for detecting the voltage across the pre-charge resistor may have a comparison element for comparing the voltage tapped at the pre-charge resistor with a reference voltage from a DC voltage source. This voltage is referred to as pre-charge voltage below. In this way, it is possible to determine in a simple manner whether the voltage at the pre-charge resistor and therefore the state of charge of the capacitor corresponds to an expected value. The comparison element may be a comparator in particular. When a voltage divider is used, the output of the first voltage divider may be connected to the inverting input of the comparator. In order to prevent incorrect switching and introduce switching hysteresis, the comparator may be formed by a Schmitt trigger.

[0014] The DC voltage source for the reference voltage may be a DC voltage converter. The DC voltage converter may be powered on the input side by a low voltage source from the outside of the pre-charge switch arrangement. The DC converter may be used to provide a sufficiently high DC voltage with which the voltage tapped at the pre-charge resistor or provided by the first voltage divider may be compared. Powering from the outside of the pre-charge switch arrangement is particularly advantageous because the DC voltage converter may then provide a voltage that is current-blocked from the high voltage side.

[0015] In order to define a reference voltage for the comparison element, the DC voltage source may be connected to the comparison element via a second voltage divider. When a comparator is used, the output of the second voltage divider may be connected to the inverting input of the comparator.

[0016] In order to realize a particularly simple construction, the control input of the pre-charge switch can be connected to the input of the DC voltage converter. The control input of the pre-charge switch can particularly energize the coil of a contactor or relay. Such an arrangement enables the pre-charge switch arrangement to have a minimum possible number of low-voltage connections. Due to the use of a common input for the control input of the pre-charge switch and for the DC voltage converter, the DC voltage converter is just activated when the pre-charge switch is switched on.

[0017] The comparison element can be connected at the output side to the input of the transmission unit. A signal of the comparison element can thereby be transmitted, which can be used to control a controllable switching element of the DC circuit.

[0018] This is particularly advantageous when the transmission unit has an output that is galvanically isolated from its input. The output of the transmission unit can, for example, be connected to an electronic control system. The galvanic isolation allows the electronic control system to be operated separately from the high DC circuit. This can significantly increase the reliability, for example, of a vehicle using such a pre-charging switch arrangement.

[0019] Particularly good current blocking can be achieved by the transmission unit being an optocoupler.

[0020] A particularly compact structure can be achieved by connecting the supply line of the output of the transmission unit to the input of the DC voltage converter. If the transmission unit is, for example, an optocoupler, then for example the collector of a phototransistor in the optocoupler may be connected to the same positive supply line, which is also connected to the DC voltage converter on the input side. The emitter of the phototransistor in the optocoupler can then provide the signal of the transmission unit. Such a structure enables the pre-charge switch arrangement to have a total of only three connections, the positive connection, the negative connection and the signal line.

[0021] The pre-charge switch arrangement may have a common reference potential for the supply line of the comparison element, for the output of the DC voltage converter, for the input of the transmission unit, for the first voltage divider and for the second voltage divider, said potential being connected to a line connecting the pre-charge resistor to the pre-charge switch. Such an arrangement enables the pre-charge switch arrangement to be operated separately from the line of the high DC circuit, which carries the negative high voltage potential. Thereby creep currents and power consumption of the pre-charge switch arrangement when it is not used are prevented.

[0022] It is particularly advantageous that the pre-charge switch arrangement is connected exclusively to the high DC circuit via two high voltage connections. The pre-charge switch arrangement can be connected via these two connections upstream and downstream of the controllable switching elements connected in parallel of the DC circuit. In this way, when the pre-charge switch is disconnected, the pre-charge switch arrangement is only connected to one pole of the high voltage source of the DC circuit. When the pre-charge switch is disconnected, the pre-charge switch arrangement is not affected by the current supplied by the high voltage source. This enables a particularly reliable construction and operation. In addition, when the pre-charge switch is disconnected, no quiescent current is taken away from the battery.

[0023] At least the two voltage dividers, the pre-charging resistor, the pre-charging switch, the comparison element, the transmission unit and the DC voltage converter can form a component group arranged in a common housing. A particularly compact design of the pre-charging switch arrangement is thus possible. It is particularly advantageous if the housing has exactly three low-voltage connections for operating the outputs of the DC voltage converter and the transmission unit and two high-voltage connections which are connected in parallel with the controllable switching elements of the circuit.

[0024] The method mentioned in the introduction for connecting a load to a high DC voltage source can be improved by using a pre-charging switch arrangement according to one of the embodiments described above.

[0025] In order to increase the reliability when executing the present method and ensure operational safety when reaching the expected charge state of the capacitor (for example, the safety of the vehicle using the present method), the pre-charge switch can be disconnected and the pre-charge switch arrangement can thereby be switched to a power-free state.

[0026] In the following, the invention is explained in more detail by way of example with reference to embodiments and the accompanying drawings. According to the above explanations, the feature combinations illustrated in the embodiments by way of example can be supplemented by additional features depending on the requirements of a specific application, the additional features being based on the features of the power supply arrangement (according to the invention) and the pre-charge switch arrangement (according to the invention). Similar to the above description, individual features may also be omitted in the described embodiments when their functionality is not important in a specific application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The same reference signs are always used in the figures for elements having the same function and / or the same structure.

[0028] In the attached picture:

[0029] Figure 1 is a schematic circuit diagram of a pre-charging switch arrangement according to the invention in a power supply arrangement according to the invention;

[0030] Figure 2is a schematic diagram of the structure of a device according to the present invention for detecting a voltage across a resistor;

[0031] Figure 3 is a circuit diagram of an embodiment of a power supply arrangement according to the invention and of a pre-charging switch arrangement according to the invention. DETAILED DESCRIPTION

[0032] The device and method according to the invention are described below with a pre-charge switch arrangement and a second controllable switch element being on the positive side of, for example, a high current circuit. However, it is also possible to implement the method with an arrangement on the negative side of the device and with the device according to the invention at the negative side. In this case, the second controllable switch element may also be located at the negative side, while the first controllable switch element may be arranged at the positive side.

[0033] Figure 1 A pre-charging switch arrangement 1 according to the invention is shown, which has a device 3 for detecting a pre-charging resistor R across a power supply arrangement 5 according to the invention. V The power supply arrangement 5 has a DC circuit 7, which is referred to as the power supply circuit 7 in the following. The power supply circuit 7 can Figure 1 The capacitor C of the load is only exemplified in FIG. 1 ) connected to a high DC voltage source B. The high DC voltage source B can be a high voltage battery in particular. The power supply circuit 7 can be switched to all poles, i.e., the controllable switching elements S1 and S2 are arranged at both sides of the high DC voltage source B.

[0034] If both controllable switching elements S1 and S2 are closed, the capacitor C is connected to the high DC voltage source B. A pre-charging switch arrangement 1 is connected in parallel with the controllable switching element S2. The pre-charging switch arrangement 1 has a pre-charging resistor R V and pre-charge switch S V . Pre-charge resistor R V and pre-charge switch S V They are arranged in series on line section 9.

[0035] To detect the voltage across the pre-charge resistor R V The voltage U V , device 3 has a precharge resistor R V The upstream and downstream are connected to the line section 9. The device 3 can be additionally connected to the line M as a pre-charging resistor R V and pre-charge switch S V The reference potential M is located at an additional position of the line section 9 between Figure 3 Description. Across the pre-charge resistor R VDetected voltage U V Can be used to evaluate the charge state of capacitor C.

[0036] Figure 2 is a schematic diagram of the structure of the device 3. V The pre-charge voltage U V is supplied to the first voltage divider 11 and the measured voltage U converted therefrom M From there it is supplied to the comparison element 13. In the comparison element 13, the voltage U M is compared with the reference voltage U generated by the DC voltage source 15 R Compare. The DC voltage source 15 can in particular be a DC voltage converter.

[0037] The comparison element 13 is connected to the transmission unit at the output side. Input Switching signal S S is led from the comparison element 13 to the transmission unit Input Transmission unit With input from Current blocking output Transmission unit Output The switch signal S' s Transmitted to the outside of device 3. Switching signal S' s Can be used to switch the controllable switch element S2. Switching signal S' s The control input of the controllable switching element S2 can be led directly or via a suitable evaluation or electronic control system. The control input can, for example, be adjacent to the coil of the switching element S2 which is designed as a contactor or relay.

[0038] The method according to the invention for connecting a load or its capacitor C to a high DC voltage source B (eg to the second controllable switching element S2 on the positive side of the power supply circuit 7 and the pre-charging switch arrangement 1) is described below with reference to Figure 1 and 2 describe.

[0039] Initially, all switching elements S1, S2 and S V is open. There is no voltage at the capacitor C. In a first step, the controllable switching element S1 is closed. The side of the capacitor C facing the switching element S1 is then connected to one pole of a high DC voltage source B.

[0040] In order to precharge the capacitor C, the precharge switch S V At the same time, device 3 is supplied with voltage. By closing the pre-charge switch SV , capacitor C is pre-charged via resistor R V Connect to high DC voltage source B. Via pre-charge resistor R V , the charging current now flows through the capacitor C, which is thereby charged. During the charging operation, across the pre-charge resistor R V The voltage U V is tapped from device 3. Voltage U V Used to establish the charging state of capacitor C.

[0041] At the beginning of the charging operation, the full voltage of the high DC voltage source B is applied across the pre-charge resistor R V Apply, and pre-charge voltage U V and measuring voltage U M Greater than the reference voltage U R . Reference voltage U R is adjusted according to the desired charge state of capacitor C. Across resistor R V As the charge state of capacitor C increases, the voltage U in comparison element 13 decreases. M Lower than the reference voltage U R , the comparison element will switch the signal S S Transfer to the transmission unit

[0042] Transmission unit The switch signal S S The control input of the controllable switching element S2 is led directly or indirectly. The controllable switching element S2 is thereby closed, whereby the power supply circuit 7 is closed. The load or its capacitor C is then connected to the high DC voltage source B at all poles. If the controllable switching element S2 is closed, the pre-charging switch S V Since the circuit is then interrupted on line section 9 , current can no longer flow through the pre-charging switch arrangement 1 .

[0043] Figure 3 A circuit diagram of an embodiment of a pre-charging switch arrangement 1 according to the invention in a power supply arrangement 5 according to the invention is shown. The circuit diagram follows the structure of the arrangement and device 1, 3 and 5 according to the invention, which structure is referred to as Figure 1 and 2 describe.

[0044] The pre-charging switch arrangement 1 is connected to the high voltage potential of the power supply circuit 7 only via the two high voltage connections 17 and 19. As already described above, by opening the pre-charging switch S V , the pre-charge switch arrangement 1 is switched into the unpowered state.

[0045] The structure of the pre-charging switch arrangement 1 according to the invention is based on the pre-charging resistor R V is described below. Across the pre-charge resistor R V , pre-charge voltage U V is tapped using a first voltage divider 11. The first voltage divider 11 is formed by resistors R1 and R2. V is not exactly the same as the charging voltage at capacitor C. However, the pre-charge voltage U V Can be used to determine the charge state of capacitor C. The first voltage divider 11 provides a measurement voltage U M , which is supplied to the inverting input of the comparator 13.

[0046] The comparator 13 (which serves as a comparison element 13) has supply connections V+, V-. The negative supply connection V- is adjacent to the line M of the device 3. The line M is connected to the voltage divider 11 and the pre-charge switch S V 9 between line M and the inverting input of comparator 13, a Zener diode ZD1 and a capacitor C2 in parallel therewith are connected, which limit the voltage to a suitable level. The voltage depends on the comparator 13, which is used in a component-specific manner. In order not to impair the function of comparator 13, the value of the Zener voltage must be higher than the reference voltage at the non-inverting input. Zener diode ZD1 serves to protect the inverting comparator input. Capacitor 2 serves to stabilize the inverting input.

[0047] An additional resistor R3 may be connected between the voltage divider 11 and the inverting input of the comparator 13 .

[0048] Reference voltage U R is applied to the non-inverting input of the comparator 13. R It is provided by a DC voltage source 15. The DC voltage source 15 may be an output 15 of a DC voltage converter 21. The negative output 15 of the DC voltage converter 21 is connected to the line M.

[0049] Between the positive output of the DC voltage converter 21 and the line M, a capacitor C3 may be connected. The capacitor C3 may be used to stabilize the output voltage of the DC voltage converter 21. The positive output of the DC voltage converter 21 is connected to the positive supply connection V+ of the comparator 13.

[0050] Reference voltage U RThe voltage is provided by a second voltage divider 23 formed by resistors R4 and R5 and connected between the line M and the positive output of the DC voltage converter 21. The output of the second voltage divider 23 is connected via a resistor R6 to the non-inverting input of the comparator 13. The capacitor C1 is connected between the line M and the non-inverting input of the comparator 13 and the resistor R6 and serves to stabilize the non-inverting input of the comparator 13.

[0051] The output of the comparator can be connected to the non-inverting input via resistor R7. A switching hysteresis can thereby be generated, thereby preventing incorrect switching from occurring. The comparator 13 can form a Schmitt trigger together with resistors R7 and R6.

[0052] The output of the comparator 13 can be connected to the transmission unit via the resistor R8. Input In the illustrated embodiment, the transmission unit It is an optocoupler And input It is a light emitting diode Light Emitting Diode The generated light signal can be detected by a phototransistor (It constitutes a transmission unit Output ) is received and can be converted into an electrical signal S' s This signal S' s Can be used to control the controllable switching element S2.

[0053] Phototransistor Can be connected to a low voltage device 25. The low voltage device 25 may belong to an electronic control system (not shown). The low voltage device 25 may have a positive connection, a negative connection, and a signal line. Phototransistor can be connected to the positive line and to the signal line of the low voltage device 25. On the input side, the DC voltage converter 21 can also be connected to the low voltage device 25. The DC voltage converter 21 can be connected to the positive and negative connections of the low voltage device 25 and thereby maintain its operating voltage.

[0054] In a particularly advantageous embodiment, the input 26 of the DC voltage converter 21 can be connected to the pre-charging switch S V The same operating voltage of the low voltage device 25 can then be used to operate the DC voltage converter 21 and the control input 29 (eg, the pre-charge switch S V Coil) both.

[0055] A particularly compact embodiment of the pre-charging switch arrangement 1 according to the invention has only two high voltage connections 17, 19 and three connections to low voltage devices 25. The low voltage devices 25 are preferably outside the pre-charging switch arrangement 1. The pre-charging switch arrangement 1 is not connected in an electrically conductive manner to a negative branch 27 of the power supply circuit 7 at any point.

[0056] The elements of the pre-charging switch arrangement 1 preferably form a component group 31 which can be accommodated in a common housing (not shown).

[0057] Reference numerals list

[0058] 1 Pre-charge switch arrangement

[0059] 3 Equipment

[0060] 5 Voltage supply arrangement

[0061] 7 DC Circuit

[0062] 9 Line segments

[0063] 11 First voltage conductor

[0064] 13 Comparison element / comparator

[0065] 15 DC voltage source

[0066] 17 High voltage connection

[0067] 19 High voltage connection

[0068] 21 DC voltage converter

[0069] 23 Second voltage divider

[0070] 25 Low voltage equipment

[0071] 26 Input of DC voltage converter

[0072] 27 Negative branch of power supply circuit

[0073] 29 Control Input

[0074] 31 Components

[0075] B High DC voltage source

[0076] C Capacitor

[0077] C1 capacitor

[0078] C2 capacitor

[0079] C3 capacitor

[0080] M Reference potential

[0081] R V Pre-charge resistor

[0082] R1 resistor

[0083] R2 resistor

[0084] R3 resistor

[0085] R4 resistor

[0086] R5 resistor

[0087] R6 resistor

[0088] R7 resistor

[0089] R8 resistor

[0090] S1, S2 switch elements

[0091] S S Switch signal

[0092] S V Precharge switch

[0093] U M Measuring voltage

[0094] U R Reference voltage

[0095] U V Precharge voltage

[0096] Transmission unit / optical coupler

[0097] Output of the transmission unit

[0098] Transmission unit input / LED

[0099] V+, V- supply connection

[0100] ZD1 Zener diode

Claims

1. A pre-charging switch arrangement (1) for charging a capacitor (C) of a DC circuit (7), having a pre-charging resistor (R V ), pre-charge switch (S V ), a DC voltage source (15), and a circuit for detecting a voltage across a pre-charge resistor (R V ) voltage (U V ) device (3), wherein the pre-charge resistor (R V ) is at least indirectly connected to the pre-charge resistor (R V ) voltage (U V ) device (3), wherein the device for detecting the voltage across the pre-charge resistor (R V ) voltage (U V ) has a comparison element (13) for comparing the pre-charge resistor (R V ) tapped voltage (U V ) and the reference voltage (U R ) for comparison, where the reference voltage (U R ) is a DC voltage converter (21), wherein the pre-charge switch (S V ) is configured to control the pre-charge switch (S V ) is energized by a coil, the pre-charging switch being a contactor or a relay, wherein the pre-charging switch (S V ) is connected to the input (26) of the DC voltage converter (21) so that when the pre-charge switch (S V ) is switched on, the DC voltage converter (21) is activated, wherein the comparison element (13) is connected to the transmission unit ( ) input( ), and the transmission unit ( ) has a value from its input ( ) Current blocking output ( ).

2. The pre-charging switch arrangement (1) as claimed in claim 1, Features The resistor used to detect the V ) voltage (U V ) has a first voltage divider (11) which is connected at the input side to a pre-charge resistor (R V ).

3. The pre-charging switch arrangement (1) as claimed in claim 1, Features The DC voltage source (15) is connected to the comparison element (13) via a second voltage divider (23).

4. The pre-charging switch arrangement (1) as claimed in claim 1, Features Transmission unit ( )'s output( ) is connected to the input (26) of the DC voltage converter (21).

5. A pre-charging switch arrangement (1) according to any one of claims 1 to 4, Features The supply line of the comparison element (13), the output (15) of the DC voltage converter (21), the transmission unit ( ) input( ), the first voltage divider (11) and the second voltage divider (23) have a common reference potential (M) connected to the pre-charge resistor (R V ) is connected to the precharge switch (S V ) of line (9).

6. A pre-charging switch arrangement (1) according to any one of claims 1 to 4, Features At least two voltage dividers (11, 23), a pre-charge resistor (R V ), pre-charge switch (S V )、Comparison element (13), transmission unit ( ) and the DC voltage converter (21) form a component group (31) arranged in a common housing.

7. A power supply arrangement (5) for an electrical load, the load being a capacitor on the input side, having a DC circuit (7) connecting a high DC voltage source (B) to the capacitor (C) and having two controllable switching elements (S 1 , S 2 ), the two controllable switch elements (S 1 , S 2 ) are each arranged between a pole of a capacitor (C) and a high DC voltage source (B), Features A pre-charging switch arrangement (1) and a controllable switching element (S) according to any one of claims 1 to 6 2 ) are connected in parallel.

8. A power supply arrangement (5) for an electrical load according to claim 7, Features The pre-charging switch arrangement (1) is only operated by means of a controllable switching element (S 2 ) Two high voltage connections (17, 19) upstream and downstream are connected to the DC circuit (7).

9. A method for connecting a load to a high DC voltage source (B), wherein the load is connected to a high DC voltage source (B) according to a pre-charge resistor (R V ) voltage (U V ) is connected to a high DC voltage source (B), the pre-charge resistor (R V ) is placed between the high DC voltage source (B) and the load, Features The method uses a pre-charging switch arrangement (1) according to any of claims 1-6 and a power supply arrangement (5) according to any of claims 7-8.

10. The method according to claim 9, It is characterized in that When the expected charging state is reached, the pre-charge switch (S V ) is disconnected and the pre-charging switch arrangement (1) is thereby switched to a power-free state.

11. The method according to claim 9 or 10, It is characterized in that When the desired charging state is reached, the voltage difference between the high DC voltage source (B) and the load (7) is low enough so that the controllable switch element (S 2 ) can be closed without being damaged or destroyed by huge surge currents.

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