DIAGNOSTIC CIRCUIT FOR A BATTERY DISCONNECT UNIT, METHOD FOR DIAGNOSING A BATTERY DISCONNECT UNIT, BATTERY DISCONNECT UNIT

Abstract

A diagnostic circuit (60) for diagnosing a battery disconnect unit (100) for disconnecting a battery system (200) from an electrical system (300). The battery disconnect unit (100) includes a first switching element (S1) and a second switching element (S2). A first connection of the first switching element (S1) is connected to a first node point (8), and a second connection of the first switching element (S1) is connected to the first terminal (2). A first connection of the second switching element (S2) is connected to the first node point (8), and a second connection of the second switching element (S2) is connected to the second terminal (4). The diagnostic circuit (60) includes a first voltage divider (61) and a second voltage divider (62).

Claims

1. A diagnostic circuit (60) for diagnosing a battery disconnect unit (100) for disconnecting a battery system (200) from an electrical system (300), the battery disconnect unit (100) comprising: a first terminal (2), a second terminal (4), a first switching element (S1), and a second switching element (S2), wherein a first connection of the first switching element (S1) is connected to a first node point (8), a second connection of the first switching element (S1) is connected to the first terminal (2), a first connection of the second switching element (S2) is connected to the first node point (8), and a second connection of the second switching element (S2) is connected to the second terminal (4), wherein the diagnostic circuit (60) comprises a first voltage divider (61) comprising a first resistor (R1), a second resistor (R2), and a first protective diode (D1), and a second voltage divider (62) comprising a third resistor (R3), a fourth resistor (R4), and a second protective diode (D2), wherein the first resistor (R1), the second resistor (R2), and the first protective diode (D1) are connected in series such that the anode of the first protective diode (D1) is connected to a second node point (63), the cathode of the first protective diode (D1) is connected to a first connection of the first resistor (R1), a second connection of the first resistor (R1) is connected to a first connection of the second resistor (R2), and a second connection of the second resistor (R2) is connectable to one of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2), wherein the third resistor (R3), the fourth resistor (R4), and the second protective diode (D2) are connected in series such that the anode of the second protective diode (D2) is connected to the second node point (63), the cathode of the second protective diode (D2) is connected to a first connection of the third resistor (R3), a second connection of the third resistor (R3) is connected to a first connection of the fourth resistor (R4), and a second connection of the fourth resistor (R4) is connectable to the other of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2).

2. The diagnostic circuit (60) according to claim 1, wherein the first and the second voltage divider (61, 62) have an identical resistance ratio.

3. The diagnostic circuit (60) according to claim 1, wherein a resistance ratio of the first voltage divider (61) deviates from a resistance ratio of the second voltage divider (62).

4. The diagnostic circuit (60) according to claim 1, further comprising a DC voltage source (64) that generates a DC voltage (UE) between the first and the second node point (8, 63) during diagnostics.

5. A method of diagnosing a battery disconnect unit (100) for disconnecting a battery system (200) from an electrical system (300) by means of a diagnostic circuit (60) having a first voltage divider (61) including a first resistor (R1), a second resistor (R2), and a first protective diode (D1), and a second voltage divider (62) including a third resistor (R3), a fourth resistor (R4), and a second protective diode (D2), wherein the battery disconnect unit (100) comprises a first terminal (2), a second terminal (4), a first switching element (S1), and a second switching element (S2), wherein a first connection of the first switching element (S1) is connected to a first node point (8), a second connection of the first switching element (S1) is connected to the first terminal (2), a first connection of the second switching element (S2) is connected to the first node point (8), and a second connection of the second switching element (S2) is connected to the second terminal (4), wherein the method comprises the following steps: connecting a second connection of the second resistor (R2) to one of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2); connecting a second connection of the fourth resistor (R4) to the other of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2); generating a DC voltage (UE) between the first and the second node point (8, 63) by means of a DC voltage source (64), while the first and the second switching element (S1, S2) are in the open state; detecting a first measured value of a voltage drop (UP1) at the second resistor (R2); detecting a second measured value of the voltage drop (UP2) at the fourth resistor (R4); and outputting the switching states of the first and the second switching element (S1, S2).

6. A battery disconnect unit (100) for disconnecting a battery system (200) from an electrical system (300), comprising a first terminal (2), a second terminal (4), a first switching element (S1) and a second switching element (S2), wherein a first connection of the first switching element (S1) is connected to a first node point (8), a second connection of the first switching element (S1) is connected to the first terminal (2), a first connection of the second switching element (S2) is connected to the first node point (8), a second connection of the second switching element (S2) is connected to the second terminal (4), wherein the battery disconnect unit (100) further comprises a diagnostic circuit (60) including a first voltage divider (61) having a first resistor (R1), a second resistor (R2), and a first protective diode (D1), and a second voltage divider (62) having a third resistor (R3), a fourth resistor (R4), and a second protective diode (D2), wherein the second connection of the second resistor (R2) is connected to one of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2), and the second connection of the fourth resistor (R4) is connected to the other of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2).

7. The battery disconnect unit (100) according to claim 6, further comprising a current sensing resistor (6) connected between the first terminal (2) and the second connection of the first switching element (S1) or between the first connection of the first switching element (S1) and the first node point (8) or between the first node point (8) and the first connection of the second switching element (S2) or between the second connection of the second switching element (S2) and the second terminal (4).

8. The battery disconnect unit (100) according to claim 6, wherein the first and the second switching element (S1, S2) include a semiconductor switch.

9. A battery system (200) comprising: a battery disconnect unit (100) including a first terminal (2), a second terminal (4), a first switching element (S1), and a second switching element (S2), wherein a first connection of the first switching element (S1) is connected to a first node point (8), a second connection of the first switching element (S1) is connected to the first terminal (2), a first connection of the second switching element (S2) is connected to the first node point (8), and a second connection of the second switching element (S2) is connected to the second terminal (4), wherein the battery disconnect unit (100) further comprises a diagnostic circuit (60) including a first voltage divider (61) having a first resistor (R1), a second resistor (R2), and a first protective diode (D1), and a second voltage divider (62) having a third resistor (R3), a fourth resistor (R4), and a second protective diode (D2), wherein the second connection of the second resistor (R2) is connected to one of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2), and the second connection of the fourth resistor (R4) is connected to the other of the second connection of the first switching element (S1) and of the second connection of the second switching element (S2), and a current sensing resistor (6) connected between the first terminal (2) and the second connection of the first switching element (S1) or between the first connection of the first switching element (S1) and the first node point (8) or between the first node point (8) and the first connection of the second switching element (S2) or between the second connection of the second switching element (S2) and the second terminal (4).

10. A vehicle comprising a battery disconnect unit (100) according to claim 6.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0035] The figure shows:

[0036] FIG. 1 a schematic illustration of a battery system with a battery disconnect unit according to the invention.

DETAILED DESCRIPTION

[0037] FIG. 1 shows a schematic illustration of a battery system 200 with a battery disconnect unit 100 according to the invention.

[0038] As shown in FIG. 1, a battery disconnect unit 100 proposed according to the invention is inserted into a battery system 200. The battery system 200 comprises a plurality of battery cells 5, which in the present case are connected in series to one another. The plurality of battery cells 5 may also be connected in parallel to one another. Preferably, a certain number of battery cells 5 may be combined to form a battery module or a battery pack. A plurality of battery modules or a plurality of battery packs may in turn be connected in series and/or in parallel.

[0039] The battery system 200 is connected to an electrical system 300, which can for example be designed as an on-board power supply of a vehicle or as a charger.

[0040] The battery disconnect unit 100 serves to disconnect the battery system 200 from the electrical system 300. The battery disconnect unit 100 also serves to connect the battery system 200 to the electrical system 300.

[0041] The battery disconnect unit 100 comprises a first terminal 2, a second terminal 4, a first switching element S1, a second switching element S2 and a current sensing resistor 6. The switching elements S1, S2 each have three connections, wherein a switching path is formed between a first connection and a second connection and can be actuated by means of a third connection.

[0042] The first switching element S1 and the second switching element S2 are in the present case designed as field effect transistors. The switching elements S1, S2 each comprise a SOURCE connection, a DRAIN connection and a GATE connection. The switching elements S1, S2 are connected such that in each case, the first connection is the SOURCE connection, the second connection is the DRAIN connection, and the third connection is the GATE connection.

[0043] In the present case, the switching elements S1, S2 are n-channel enhancement-type MOSFETs. The switching elements S1, S2 each comprise a switching path as well as an inverse diode connected in parallel to the switching path. The inverse diode, also referred to as the body diode, is produced in each MOSFET due to the internal structure thereof and is not an explicit component.

[0044] A first connection of the first switching element S1 is connected to a first node point 8, and a second connection of the first switching element S1 is connected to the first terminal 2. A first connection of the second switching element S2 is connected to the first node point 8 via the current sensing resistor 6, and a second connection of the second switching element S2 is connected to the second terminal 4.

[0045] The battery disconnect unit 100 further comprises a diagnostic circuit 60 proposed according to the invention. The diagnostic circuit 60 comprises a first voltage divider 61 comprising a first resistor R1, a second resistor R2 and a first protective diode D1, and a second voltage divider 62 comprising a third resistor R3, a fourth resistor R4 and a second protective diode D2.

[0046] In this case, the first resistor R1, the second resistor R2 and the first protective diode D1 are connected in series such that the anode of the first protective diode D1 is connected to a second node point 63, the cathode of the first protective diode D1 is connected to a first connection of the first resistor R1, a second connection of the first resistor R1 is connected to a first connection of the second resistor R2, and a second connection of the second resistor R2 is connected to the second connection of the first switching element S1.

[0047] The third resistor R3, the fourth resistor R4 and the second protective diode D2 are connected in series such that the anode of the second protective diode D2 is connected to a second node point 63, the cathode of the second protective diode D2 is connected to a first connection of the third resistor R3, a second connection of the third resistor R3 is connected to a first connection of the fourth resistor R4, and a second connection of the fourth resistor R4 is connected to the second connection of the second switching element S2.

[0048] The first and the second voltage divider 61, 62 may have an identical resistance ratio. For example, the first, the second, the third and the fourth resistor R1, R2, R3, R4 may have an identical resistance value.

[0049] Alternatively, a resistance ratio of the first voltage divider 61 may deviate from a resistance ratio of the second voltage divider 62.

[0050] The diagnostic circuit 60 further comprises a DC voltage source 64, which generates a DC voltage UE of, for example, 30 V or another value between the first and the second node point 8, 63 during diagnostics. In the present case, the DC voltage source 64 is designed as a battery cell. In this case, a positive pole of the DC voltage source 64 is connected to the second node point 63. A negative pole of the DC voltage source 64 is connected to the first node point 8.

[0051] Alternatively, the DC voltage source 64 may also be designed as a DC voltage transformer that can convert a DC voltage UE of an external DC voltage source from a different voltage level to a suitable voltage level for the diagnostics. However, a rectifier that converts an AC voltage into a DC voltage UE may also be regarded as a DC voltage source 64.

[0052] The battery system 200 further includes a contactor 20 for switching the battery system 200 on and off. The contactor 20 may be designed as a mechanical relay.

[0053] When performing the method according to the invention, a DC voltage UE is generated between the first and the second node point 8, 63 by the DC voltage source 64, while the first and the second switching element S1, S2 are in the open state.

[0054] A first measured value of the voltage drop UP1 is subsequently detected at the second resistor R2 by a first measurement channel not shown here.

[0055] Simultaneously or thereafter, a second measured value of the voltage drop UP2 is detected at the fourth resistor R4 by a second measurement channel not shown here.

[0056] A statement about the switching states of the first and the second switching element S1, S2 is subsequently made. The detected measured values of the respective voltage drops UP1, UP2 are compared to target values of the respective voltage drops UP1, UP2 with the corresponding switching states of the first and the second switching element S1, S2.

[0057] The invention is not limited to the exemplary embodiments described herein and the aspects highlighted therein. Rather, a variety of modifications, which are within the scope of activities of the person skilled in the art, is possible within the range specified by the claims.