DE102016214415A1 - Circuit for detecting a voltage of a plurality of series-connected electrical energy storage units and method for operating this circuit - Google Patents

Abstract

The invention relates to a circuit for detecting a voltage of a plurality of series-connected electrical energy storage units, the circuit each having a switch for each electrical energy storage unit whose first terminal is respectively connected to its positive pole, a first and a second voltage source, a first and a second voltage source a second transistor and a first and a second ohmic resistor, wherein a control input of the first transistor having a positive pole of the first voltage source and an emitter terminal of the first transistor are electrically connected to a second terminal of the first ohmic resistor includes. In this case, each electrical energy storage unit (Z1,..., Z6) is assigned a switch (S1,..., S6) and a first terminal of the respective switch (S1,..., S6) is in each case associated with a positive pole of the respectively assigned one electrical energy storage unit (Z1, ..., Z6) electrically conductively connected.

Description

The present invention is based on a circuit for measuring a voltage of a plurality of series-connected electrical energy storage units and a method for operating a circuit and its use according to the preamble of the independent claims.

State of the art

In hybrid and electric vehicles systems are usually used with a large number of electrical energy storage units. Since these electrical energy storage units due to production and due to aging effects may have different properties, the voltages of these electrical energy storage units to avoid overcharging or overdischarge by means of circuits are monitored individually.

For monitoring the respective voltage, integrated circuits with one or more multiplexers are usually used.

The publication US 20100052650 A1 discloses an alternative way of measuring voltage for a plurality of electrical energy storage units.

The publication DE 102010063258 A1 also discloses possibilities of voltage measurements with transimpedance amplifiers.

The publication DE 102011079360 A1 discloses an apparatus for measuring a maximum cell voltage of a plurality of serially connected battery cells. A possible embodiment of this device is in 1 of the present application.

A disadvantage of the known prior art is that a large number of components or complex integrated circuits for detecting a voltage are necessary.

Disclosure of the invention

Advantages of the invention

According to the invention, a circuit for detecting a voltage of a plurality of series-connected electrical energy storage units, a method for operating this circuit and their use with the characterizing features of the independent claims are provided.

In this case, the circuit comprises a first and a second voltage source, a first and a second transistor and a first and a second ohmic resistance, wherein a control input of the first transistor having a positive pole of the first voltage source and an emitter terminal of the first transistor having a second terminal of the wherein each electrical energy storage unit is associated with a switch and a first terminal of the respective switch is in each case electrically conductively connected to a positive pole of the respective associated electrical energy storage unit first ohmic resistance. Thus, flexible connection options are provided as well as enabling or disabling of a single electrical energy storage unit within the scope of the voltage measurement.

Depending on the design, an electrical energy storage unit may comprise a plurality of components, for example a plurality of battery cells, which are connected in series and / or in parallel.

An electrical energy storage unit may in particular be understood as meaning an electrochemical battery cell and / or a battery module having at least one electrochemical battery cell and / or a battery pack having at least one battery module. For example, the electric energy storage unit may be a lithium battery cell or a lithium battery module or a lithium battery pack. In particular, the electrical energy storage unit may be a lithium-ion battery cell or a lithium-ion battery module or a lithium-ion battery pack. Furthermore, the battery cell may be of the type lithium polymer accumulator, nickel metal hydride accumulator, lead acid accumulator, lithium air accumulator or lithium sulfur accumulator or more generally an accumulator of any electrochemical composition.

The first and second voltage source can in particular be designed as reference voltage sources whose voltage is very constant and has only one fluctuation range in the range of a few millivolts, for example +/- 1 millivolt.

Further advantageous embodiments of the present invention are the subject of the dependent claims.

Thus, it is advantageous if, furthermore, a collector terminal of the first transistor is electrically conductively connected to a first terminal of the second ohmic resistor, and additionally a control input of the second transistor having a positive pole of the second voltage source and an emitter terminal of the second transistor having a second terminal of second ohmic resistance is electrically connected. Thereby, an electrical connection of the components and an identical structure of the circuit can be achieved.

According to a further aspect, it can be provided that a first terminal of the first ohmic resistor is electrically conductively connected to a second terminal of a further first switch and a further second switch, and the negative pole of the first voltage source to a second terminal of a further third switch and another fourth switch is electrically connected. Thus, flexible connection options for the electrical components can be created.

According to a further advantageous embodiment, a second terminal of a further fifth switch is electrically conductively connected to the first terminal of the second ohmic resistor. This achieves greater flexibility in the electrical connection options. This can then be exploited, for example, by a suitable control of the first, second, third, fourth and fifth switches.

According to a further embodiment, a first terminal of the further first switch and a first terminal of the further second switch are in each case electrically conductively connected in alternation of the electrical energy storage units to a second terminal of the switch assigned to each electrical energy storage unit. Furthermore, in this embodiment, a first terminal of the further third switch and a first terminal of the further fourth switch in the same manner in each case in alternation with a second terminal of each electrical energy storage unit associated switch electrically connected. As a result, individual electrical energy storage units can be selectively connected to an assembly consisting of the first resistor, the first transistor and the first reference voltage source. The potential of the connected electrical energy storage unit ensures a flow of current through these components.

Furthermore, it is advantageous if a first terminal of the further fifth switch is electrically conductively connected to a second terminal of the switch of the first series-connected electrical energy storage unit. Thus, the electrical potential of this associated electrical energy storage unit without use of the further first, further second, further third and / or further fourth switch can be switched via this further fifth switch. This prevents a possible influence on the voltage measurement in the first series-connected electrical energy storage unit in the sequence.

According to one embodiment, the first terminal of the second ohmic resistor and a collector terminal of the second transistor are electrically conductively connected to a voltage measuring unit. In this case, this voltage measuring unit, for example, an analog-to-digital converter and an amplifier, in particular an amplifier with programmable gain, also called Programmable Gain Amplifier include. In addition, an additional voltage source can be provided for this voltage measuring unit. In this case, the voltage position of the additional voltage source can be selected such that a transfer function of the voltage measuring unit is shifted into the typical voltage range of an electrical energy storage unit. Thus, the measurement accuracy of the voltage measurement unit can be increased.

According to a further advantageous embodiment, for example, a complementary Darlington circuit is used instead of the first and / or second transistor. As a result, a base current flowing via the control input, which has an effect on the current flowing through the first or second ohmic resistor, is reduced and the accuracy of the circuit is improved.

According to a further embodiment, a control input of a third transistor to the emitter terminal of the first transistor and a control input of a fourth transistor to the collector terminal of the first transistor are electrically connected. Thus, the control inputs of the third and fourth transistor in operation without error at different potential levels, which can be used for error detection.

Advantageously, an emitter terminal of the third transistor is electrically conductively connected via a third ohmic resistor to an emitter terminal of the fourth transistor, and a collector terminal of the fourth transistor is electrically conductively connected to a reference potential via a fourth ohmic resistor. This circuit can be used to detect certain errors, such as a short circuit of the first transistor. As a result, safety requirements, such as those set by the various ASIL levels in the automotive sector, can be met.

Furthermore, the subject matter of the invention is a method for operating such a circuit, in which two successive switches, each associated with an electrical energy storage unit, are closed and the further first switch and the further second switch are each opened or closed and the further third switch and the other fourth switches are respectively opened or closed so that the first ohmic resistance is electrically connected to the positive pole of one of the two consecutive electrical energy storage units and the negative pole of the first voltage source is electrically connected to the corresponding negative pole of one of the two consecutive electrical energy storage units , By means of this opening or closing, respectively, the voltage of a single electrical energy storage unit causes a current flow through the first resistor. In alternation, all electrical energy storage units can thus be switched on or off. As a result, the electrical energy storage units can be monitored cyclically, for example, with a relatively low outlay on electrical components.

In another aspect, the voltage drop across the second ohmic resistor and the second transistor may be detected. As a result, a simple determination of the individual cell voltages can be made possible.

Appropriately, by means of a detection of the potential before the fourth ohmic resistance to a reference potential a statement about possible errors in the circuit allows. As a result, safety requirements, such as those set by the various ASIL levels in the automotive sector, can be met.

Brief description of the drawings

Advantageous embodiments of the invention are illustrated in the figures and explained in more detail in the following description.

It shows:

1 a taken from the prior art circuit arrangement;

2 a schematic representation of a circuit according to the invention according to a first embodiment;

3 a schematic representation of a circuit according to the invention according to a second embodiment;

4 a schematic representation of a circuit according to the invention according to a third embodiment;

5 a schematic representation of a section of a circuit according to the invention according to a fourth embodiment; and

6 a flowchart of a method according to the invention according to a first embodiment.

Embodiments of the invention

The same reference numerals denote the same device components in all figures.

wobei U_ref der Spannungswert der ersten Spannungsquelle UR1 und U_BE,1 die Basis-Emitter-Spannung des ersten Transistors T1 ist. R ist der Widerstandswert des ersten ohmschen Widerstands R1. Unten den genannten Annahmen ergibt sich der messbare Spannungsabfall U_AD zu: U_AD = I₁R + U_ref + U_BE = U_C2 und entspricht der Spannung U_C2 der elektrischen Energiespeichereinheit Z2. 2 schematically shows a first embodiment of a circuit according to the invention. Electrical energy storage units Z1 to Z6 are each assigned a switch S1 to S6, which, depending on the switch position, a positive pole of the respective electrical energy storage unit Z1 to Z6 with a first ohmic resistor R1, a second ohmic resistor R2 or other ohmic resistors R3 to R6 combines. Furthermore, the electrical energy storage unit Z2 is a first voltage source UR1 and a first ohmic resistance R1, the electrical energy storage unit Z1 a second voltage source UR2 and a second ohmic resistor R2 and the other electrical energy storage units Z3 to Z6 each have a voltage source UR3 to UR6 and a resistor R3 to Assigned to R6. Furthermore, the electrical energy storage unit Z2 is a first transistor T1, the electrical energy storage unit Z1 a second transistor T2 and the other electrical energy storage units Z3 to Z6 each assigned a transistor T3 to T6. Ideally, the transistor, resistor, and voltage source components each have substantially the same characteristics. The closing of an arbitrary switch S1 to S6 and the simultaneous opening of the respective other switches S1 to S6 generates a current flow through a respective voltage U _C1 to U _{C6 of} the selected electrical energy storage unit Z1 to Z6. A resulting voltage drop U _AD is via lines 400 and 401 from a voltage measuring unit 102 detects and corresponds, under some idealizing assumptions such as the same component properties and neglecting the respective base-emitter currents, the respective voltage U _C1 to U _{C6 of} the selected electrical energy storage unit Z1 to Z6. Is closed, for example, a switch S2 and the other switches S1 and S3 to S6 are open, flows through the first resistor R1, a current I _1, for which:

where U _{ref is} the voltage value of the first voltage source UR1 and U _{BE, 1 is} the base-emitter voltage of the first transistor T1. R is the resistance of the first ohmic resistor R1. At the bottom of these assumptions, the measurable voltage drop U _AD is: U _AD = I ₁ R + U _ref + U _BE = U _C2 and corresponds to the voltage U _{C2 of} the electrical energy storage unit Z2.

3 schematically shows a section of a second embodiment of a circuit according to the invention with additional components for error detection. A third and fourth ohmic resistance R3 and R4 and a third and fourth transistor T3 and T4 are electrically conductively connected to each other, that it is possible to detect both short circuits of the first voltage source UR1 and the first transistor T1. This is done by means of a line 103 a potential U _err before the fourth ohmic resistance R4 with respect to a reference potential, for example ground, an evaluation unit (in 3 not shown). If the potential U _{err has} a low level, for example essentially 0 V, when the voltage U _{C2 of} the electrical energy storage units Z2 is actively measured, there is a high probability of a short circuit of the first transistor T1 or of the first voltage source UR1. Sources of error that would falsify a measurement of the voltage U _{C2 of} the electrical energy storage unit Z2 are thus detected.

For example, if there is a short circuit of the first transistor T1, the control inputs of the third and fourth transistors T3 and T4 are at the same potential. Therefore, these transistors block and over the line 103 In a connected evaluation unit, a low level of U _{err is} detected and an error is detected.

For each to be monitored circuit arrangement of transistor and voltage source, for example in 2 for each pair of transistor T1, T3 to T6 and associated voltage source UR1, UR3 to UR6, such an error detection circuit is to be constructed.

In 4 a third embodiment of a circuit according to the invention is shown schematically. In this case, the circuit comprises the first voltage source UR1 and the second voltage source UR2 and the first transistor T1 and the second transistor T2. Furthermore, the first and second ohmic resistors R1 and R2 are integrated in the circuit. By means of a further first, further second, further third and further fourth switches S11, S12, S21 and S22 as well as the switches S1 to S6 assigned to the respective electrical energy storage units Z1 to Z6, the electrical energy storage units Z1 to Z6 can be connected to the first ohmic resistance R1 and the first voltage source UR1 electrically conductively connected. Preferably, this electrical connection for any electrical energy storage unit Z2 to Z6, except for the first electrical energy storage unit Z1, by a suitable switch position such that the positive pole of the electrical energy storage unit with the first ohmic Resistor R1 and its negative pole is conductively connected to the negative pole of the first voltage source UR1. This is referred to below as active voltage measurement. Ideally, the first and second ohmic resistors R1 and R2 have the same resistance value R, and the first and second voltage sources UR1 and UR2 provide the same voltage U _ref . Then, with a suitable choice of the voltage value U _{ref, the} following relationship applies to the current I ₁ flowing through the first ohmic resistor R ₁ :

In this case, U _{BE, 1,} the base-emitter voltage of the first transistor T1 and denotes that voltage which is applied between the base and emitter of the first transistor T1, when a current flows between its emitter and collector.

Ideally, the first and second transistors T1 and T2 have the same base-emitter voltage U _BE . U _Ci denotes one of the voltages U _C2 to U _C6 depending on the switch position of the other first, further second, further third and further fourth switch S11, S12, S21 and S22 and the respective electrical energy storage units Z1 to Z6 associated switches S1 to S6 , The current I ₁ flows with a suitable choice of the voltage value U _ref through the second ohmic resistor R2 and the second transistor T2. The resulting voltage drop is via lines 100 and 101 from the voltage measuring unit 102 detected. The same applies to the voltage measurement unit 102 detected voltage U _erf under the described ideal conditions:

Another fifth switch Sc serves to connect the electrical energy storage unit Z1 directly to the voltage measuring unit 102 to prevent distortions of the detected voltage values. In the case of deviating properties of the corresponding components, calculations can be carried out downstream, for example in a cell monitoring unit (CSC) or a control unit, in order to determine the correct voltage values of the respective electrical energy storage units, since their values in formula 2 do not cancel each other out. With knowledge of the respective properties of the components but this is readily possible.

In addition, one embodiment of the circuit may include common-body transistors, which further reduces possible component-to-component variations, such as thermal differences or manufacturing variations.

The corresponding switches S1 to S6, the further fifth switch Sc and the further first, further second, further third and further fourth switches S11, S12, S21 and S22 can be embodied as semiconductor switches, for example as MOSFETs, which enables fast and low-loss switching , Furthermore, instead of the illustrated first and second bipolar pnp transistors T1 and T2, other transistor designs, for example MOSFETs, may be used.

5 shows the schematic representation of a section of a fourth embodiment. In this case, a possible voltage drop across the second ohmic resistor R2 and the second transistor T2 from a voltage measuring unit 501 detected. The voltage measuring unit 501 includes an amplifier, in particular an amplifier with programmable gain, also called Programmable Gain Amplifier. In addition, an input of the voltage measuring unit 501 by means of a voltage source 500 raised to a suitable voltage level. In this case, the voltage position of the additional voltage source can be selected so that a transfer function of the voltage measuring unit in the typical voltage range of an electrical energy storage unit, for example, between 2.8 V and 4.3 V, is shifted. Thus, the measurement accuracy of the voltage measurement unit can be increased. In addition, via the capacitor 504 a low-pass filtering in the voltage measuring unit 501 reached detected voltage. diodes 503 and 502 are installed as protective diodes.

In 6 a flow chart of a method according to the invention is shown. In a first step ST1, the electrical energy storage unit is set, whose voltage is to be detected. In a second step ST2 switch positions of the switches S1 to S6, S11 to S22 and Sc are made in accordance with this definition. If, for example, the voltage U _{C6 of} the electrical energy storage unit Z6 is to be detected, the switch positions are as follows:
Switches S6 and S5 closed, switches S1 to S4 open, switches S22 and S12 closed, switches S21 and S11 open, switch Sc open.

In a third step ST3, the voltage U _erf dropping across the second ohmic resistor R2 and the second transistor T2 is supplied to a voltage measuring unit and detected. In a fourth step ST4, the detected potential U _{erf is} plausibilized. If this plausibility check is negative, an error has occurred and a fifth step ST5, an error handling procedure, is entered. If the plausibility check is positive, no error is detected and the voltage U _erf is further processed and the method continues with the first step ST1.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 20100052650 A1 [0004]
• DE 102010063258 A1 [0005]
• DE 102011079360 A1 [0006]

Claims (14)

Circuit for detecting a voltage of a plurality of series-connected electrical energy storage units (Z1, ..., Z6), comprising a first and a second voltage source (UR1, UR2), a first and a second transistor (T1, T2) and a first and a second ohmic resistor (R1, R2), wherein a control input of the first transistor (T1) with a positive pole of the first voltage source (UR1) and an emitter terminal of the first transistor (T1) with a second terminal of the first ohmic resistor (R1) are electrically conductively connected, characterized in that each electrical energy storage unit (Z1, ..., Z6) is associated with a switch (S1, ..., S6) and a first terminal of the respective switch (S1, ..., S6) each with a positive pole of the respective associated electrical energy storage unit (Z1, ..., Z6) is electrically conductively connected. A circuit according to claim 1, characterized in that a collector terminal of the first transistor (T1) with a first terminal of the second ohmic resistor (R2) is electrically connected, and a control input of the second transistor (T2) with a positive pole of the second voltage source ( UR2) and an emitter terminal of the second transistor (T2) are electrically conductively connected to a second terminal of the second ohmic resistor (R2). Circuit according to one of the preceding claims, characterized in that a first terminal of the first ohmic resistor (R1) is electrically conductively connected to a second terminal of a further first switch (S11) and a further second switch (S12), and the negative pole of first voltage source (UR1) is electrically conductively connected to a second terminal of a further third switch (S21) and a further fourth switch (S22). Circuit according to one of the preceding claims, characterized in that a second terminal of a further fifth switch (Sc) is electrically conductively connected to the first terminal of the second ohmic resistor (R2). Circuit according to one of claims 3 to 4, characterized in that a first terminal of the further first switch (S11) and a first terminal of the further second switch (S12) in each case in the change of electrical energy storage units (Z1, ..., Z6) a second terminal of each electrical energy storage unit associated switch (S1, ..., S6) are electrically connected, and a first terminal of the further third switch (S21) and a first terminal of the further fourth switch (S22) each alternating with a second terminal of each electrical energy storage unit (Z1, ..., Z6) associated switch (S1, ..., S6) are electrically connected. Circuit according to one of Claims 4 or 5, characterized in that a first terminal of the further fifth switch (Sc) is electrically conductively connected to a second terminal of the switch (S1) of the first series-connected electrical energy storage unit (Z1). Circuit according to one of the preceding claims, characterized in that the first terminal of the second ohmic resistor (R2) and a collector terminal of the second transistor (T2) are electrically conductively connected to a voltage measuring unit ( 102 . 501 ) connected is. Circuit according to one of the preceding claims, characterized in that instead of the first and / or second transistor (T1, T2) a complementary Darlington circuit is used. Circuit according to one of the preceding claims, characterized in that a control input of a third transistor (T3) to the emitter terminal of the first transistor (T1) and a control input of a fourth transistor (T4) to the collector terminal of the first transistor (T1) are electrically connected , A circuit according to claim 9, characterized in that an emitter terminal of the third transistor (T3) via a third resistor (R3) with an emitter terminal of the fourth transistor (T4) is electrically connected, and a collector terminal of the fourth transistor (T4) via a fourth ohmic resistor (R4) is electrically conductively connected to a reference potential. Method for operating a circuit according to one of Claims 5 to 10, characterized in that two successive switches (S1, ..., S6) assigned to one respective electrical energy storage unit (Z1, ..., Z6) are closed and the further first one Switch (S11) and the other second Switch (S12) are each opened or closed and the other third switch (S21) and the further fourth switch (S22) are each opened or closed so that the first ohmic resistance (R1) electrically conductive with the positive pole of the two successive electrical energy storage units (Z2, ..., Z6) is connected and the negative pole of the first voltage source (UR1) is electrically connected to the corresponding negative pole of one of the two consecutive electrical energy storage units (Z2, ..., Z6). A method according to claim 11, characterized in that the voltage drop (Uerf) via the second ohmic resistance (R2) and the second transistor (T2) is detected. Battery comprising at least two electrical energy storage units (Z1, ..., Z6), characterized in that the same comprises at least one circuit according to one of claims 1 to 10. Use of a circuit according to one of claims 1 to 10, a method according to one of claims 11 to 12 and / or a battery according to claim 13 in battery-powered vehicles including hybrid vehicles and stationary energy storage installations.

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