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A method and to a system can be used for measuring electric voltages in batteries with a number of battery cells. A measuring circuit includes at least one digital analog converter that constitutes, in combination with a number of comparators, an analog digital converter to determine the electric vo

A method and to a system can be used for measuring electric voltages in batteries with a number of battery cells. A measuring circuit includes at least one digital analog converter that constitutes, in combination with a number of comparators, an analog digital converter to determine the electric voltages of the battery cells. The comparators compare a reference voltage generated by the digital analog converter with the electric voltage of the battery cells over a number of separate measuring channels to the individual battery cells.

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1. A system for measuring electric voltages in batteries with a plurality of individual battery cells, the system comprising: a digital analog converter (DAC);a plurality of comparators;wherein the DAC and the comparators are coupled together to form a measuring circuit with an analog digital conver

1. A system for measuring electric voltages in batteries with a plurality of individual battery cells, the system comprising: a digital analog converter (DAC);a plurality of comparators;wherein the DAC and the comparators are coupled together to form a measuring circuit with an analog digital converter (ADC);wherein the measuring circuit is configured to determine the electric voltages of the individual battery cells; andwherein the comparators compare a reference voltage generated by the DAC with the electric voltage of the battery cells over a number of separate measuring channels to the individual battery cells. 2. The system according to claim 1, further comprising digital trigger logic coupled with the ADC to provide a number of measuring channels for the individual battery cells. 3. The system according to claim 1, wherein the ADC is designed to serially measure the electric voltages of the individual battery cells for one or more independent measuring cells. 4. The system according to claim 1, wherein the measuring circuit is configured to measure the electric voltages of the individual battery cells sequentially in a quasi-parallel measuring window by performing a plurality of measurement loops within a time period. 5. The system according to claim 1, wherein the measuring circuit is configured to perform a window comparator function at the battery cells, wherein in a number of comparator loops for all measuring channels both an excess voltage and an undervoltage are checked sequentially to determine whether the measured voltages of the individual battery cells lie within a particular voltage window. 6. The system according to claim 1, wherein the measuring circuit is configured to perform a window comparator function for all measuring channels in parallel, wherein in a first measurement an upper threshold value is applied as a reference value to all comparators and results of all comparators are measured simultaneously, and in a second measurement a lower threshold value is applied as a reference value to all comparators and the results of all comparators are measured simultaneously. 7. A method for measuring electric voltages in batteries with a number of individual battery cells using a measuring circuit comprising at least one digital analog converter (DAC) that constitutes, in combination with a plurality of comparators, an analog digital converter (ADC), the measuring circuit configured to determine the electric voltages of the individual battery cells, the method comprising: comparing, by the comparators over separate measuring channels to the battery cells, a reference voltage generated by the DAC with the electric voltages of the individual battery cells, wherein the reference voltage from the DAC is successively increased in a tracking phase that includes a number of tracking steps until the reference voltage exceeds the voltage measured at the battery cell; andgenerating an indication of measured voltage based upon the comparing. 8. The method according to claim 7, wherein in a binary search phase the range of a voltage measured at a battery cell is first of all limited by a binary search method, and in a subsequent tracking phase the reference voltage of the DAC is increased or decreased, respectively, depending on a comparator decision until the comparator generates a corresponding indication that the reference voltage exceeds the voltage measured at the battery cell. 9. The method according to claim 7, wherein during the tracking phase the reference voltage is, by an algorithm executed in the DAC, adapted step by step to a step width predetermined by binary resolution of the DAC and is hence approximated to the voltage measured at the battery cell. 10. The method according to claim 7, wherein the reference voltage generated by the DAC is set to half of a maximum output voltage of the DAC within a binary search phase and is increased or decreased step by step until the voltage measured at the battery cell is defined by a function of the comparator. 11. The method according to claim 7, wherein the tracking phase includes a number of tracking steps and the reference voltage generated by the DAC is compared with the voltage measured at the battery cell in a comparator in every tracking step until the reference voltage exceeds the voltage measured at the battery cell. 12. The method according to claim 11, wherein the battery cells are serially connected to a number of battery blocks or a battery stack. 13. The method according to claim 12, wherein common mode voltages of the battery blocks or battery stacks are suppressed by selected ones of the comparators with respect to the battery cell voltages so as to determine a differential voltage between terminals of the respective battery cell. 14. The method according to claim 7, wherein the measuring circuit is configured to perform excess voltage detection or undervoltage detection for the number of battery cells. 15. A system for measuring electric voltages in batteries with a plurality of battery cells, the system comprising: a measuring circuit comprising at least one digital analog converter (DAC) that constitutes, in combination with a plurality of comparators, an analog digital converter (ADC), the measuring circuit configured to determine the electric voltages of the battery cells over a number of measuring channels separately; anda trimming amplifier that is adjustable to a predetermined trimming value for every individual measuring channel, so that a reference value generated by the DAC is multiplied with a corresponding factor, so that a reference voltage for corresponding measuring channel results. 16. The system according to claim 15, further comprising an additional comparator configured to compare the reference voltage of the DAC with a band gap voltage of the measuring circuit and, when the reference voltage is lower than the band gap voltage, the trimming value for the trimming amplifier is increased and, when the reference voltage is higher than the band gap voltage, the trimming value for the trimming amplifier is decreased. 17. The system according to claim 16, wherein the measuring circuit is configured to perform gain balancing using the additional comparator in that first of all a maximum value of the DAC is adapted and subsequently a voltage measurement is performed with a comparator so as to avoid a gain error caused by the DAC during voltage measurement. 18. The system according to claim 15, wherein the measuring circuit is configured to individually compensate gain errors relating to individual measuring channels by use of a one-time trimming of the DAC and/or by use of an automatic gain error correction of the DAC during operation. 19. The system according to claim 15, wherein the battery cells comprise lithium ion (LION) cells and/or the batteries are suited as accumulators for electric vehicles. 20. A method for measuring electric voltages in batteries with a number of battery cells, the method comprising using a measuring circuit comprising at least one digital analog converter (DAC) with a number of comparators which are each connected with a battery cell over a measuring channel, wherein the measuring channels are repetitively measured one after the other and in a number of measurement loops. 21. The method according to claim 20, wherein voltage values of every battery cell are each detected individually one after the other in a number of measurement loops, and wherein subsequently an average value of measured voltage values is generated as a function of the number of measurement loops by temporal or statistical averaging. 22. The method according to claim 20, wherein a binary search method with a subsequent tracking phase is performed for each measurement of a measuring channel for a valid conversion of the corresponding comparator. 23. The method according to claim 22, wherein ADC values are each added based upon a valid conversion of the corresponding comparator for every measuring channel in an adder and are subsequently divided by the number of measurement loops performed so as to obtain a statistical average value for the voltage measured. 24. The method according to claim 20, wherein by correction of a gain error at the beginning of every measurement of a cell voltage both the influence of a gain error of the DAC and the influence of an offset error of a buffer for a DAC reference voltage on the measuring accuracy of the measuring circuit are reduced or eliminated. 25. A method for measuring electric voltages in batteries with a number of battery cells, comprising using a measuring circuit comprising at least one digital analog converter (DAC) with a number of comparators which are each connected with a battery cell over a measuring channel, wherein the voltages of every battery cell are detected individually one after the other in a number of measurement series, and wherein subsequently an average value of measured voltage values is generated by temporal or statistical averaging as a function of the number of measurement series. 26. The method according to claim 25, wherein a number of 2B measurement series are performed for a number of n measuring channels and 2B measured voltage values are added by an adder for the averaging and subsequently the last B digits of the digital sum value are neglected. 27. A system for implementing a comparator function with a programmable threshold, the system comprising: a digital analog converter (DAC):a plurality of comparators, wherein each comparator is configured to compare a reference voltage generated by the DAC with an electric voltage of an individual battery cell, the comparisons being made over a number of separate measuring channels to the individual battery cells. 28. The system according to claim 27, wherein the comparisons are performed sequentially over the measuring channels. 29. The system according to claim 27, wherein the comparisons are performed in parallel over all measuring channels.