Research on Low Leakage Current Voltage Sampling Method for Multi-cell Series Battery Packs

GUO Zhongjie; GAO Yuyang; DONG Jianfeng; BAI Ruokai

doi:10.11999/JEIT250733

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GUO Zhongjie, GAO Yuyang, DONG Jianfeng, BAI Ruokai. Research on Low Leakage Current Voltage Sampling Method for Multi-cell Series Battery Packs[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250733

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GUO Zhongjie, GAO Yuyang, DONG Jianfeng, BAI Ruokai. Research on Low Leakage Current Voltage Sampling Method for Multi-cell Series Battery Packs[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250733

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Research on Low Leakage Current Voltage Sampling Method for Multi-cell Series Battery Packs

doi: 10.11999/JEIT250733 cstr: 32379.14.JEIT250733

Xi’an University of Technology, School of Automation and Information Engineering, Xi’an 710048, China

Funds: The National Natural Science Foundation of China (62171367), Shaanxi Innovation Capability Support Project (2022TD-39)

Received Date: 2025-08-07
Accepted Date: 2025-12-29
Rev Recd Date: 2025-12-29

Available Online: 2026-01-08

Abstract

Abstract

Objective The battery voltage sampling circuit is a key component of the Battery Management Integrated Circuit (BMIC). It performs real-time monitoring of cell voltages, and its performance directly affects the safety of series battery packs. Traditional resistive voltage sampling circuits exhibit channel leakage current, which affects cell-voltage consistency and sampling accuracy. In addition, the level-shifting circuit in the high-voltage domain contains high-voltage operational amplifiers, and the use of many high-voltage MOSFETs increases area overhead. Methods This study proposes a low-leakage-current battery voltage sampling circuit for 14-series lithium batteries. Based on the traditional resistive sampling structure, channel leakage current is reduced to the pA level by designing an operational-amplifier-isolated active-drive technique. Voltage conversion methods are selected according to the voltage domain of each cell group. The first section of the battery uses a unity-gain buffer for isolation and then performs voltage conversion through resistive division. Sections 2 to 13 use operational-amplifier-isolated active driving to follow each cell voltage synchronously, after which the followed voltage is converted to a ground-referenced level through a level-shifting circuit. The voltage sampling process of the highest-section battery draws power from the entire battery stack and does not affect pack consistency; therefore, this section directly adopts the level-shifting circuit for voltage conversion. Results and Discussions The circuit was designed and verified using a 0.35 µm high-voltage BCD process. The overall layout area of the proposed sampling circuit is 3 105 µm × 638 µm (Fig. 10). Verification results show that, across different process corners and temperatures, the maximum channel leakage current after applying the isolated active-drive technique is only 48.9 pA. In contrast, the minimum leakage current of the traditional sampling circuit is 1.169 × 10⁶ pA (Fig. 12, Fig. 13). The effect of the sampling process on cell-voltage inconsistency is reduced from 18.56% to 2.122 ppm (Fig. 14). Under full PVT verification, the maximum measurement error of the proposed sampling circuit is 0.9 mV (Fig. 15, Fig. 16, Fig. 17). Conclusions This study proposes an operational-amplifier-isolated active-drive technique to address the channel leakage issue in traditional resistive voltage sampling circuits, which affects cell-voltage consistency and measurement accuracy. Using the proposed circuit, the maximum channel leakage current is 48.9 pA, the cell-voltage inconsistency is 2.122 ppm, and the maximum measurement error is 1.25 mV. The circuit achieves very low leakage current while maintaining sampling accuracy. The proposed low-leakage-current sampling circuit is suitable for 14-series lithium battery management chips.
- Battery voltage sampling,
- Operational amplifier isolated active drive,
- Level shift circuit,
- Low leakage current

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References(25)

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