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)

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 one of the key components of the Battery Management Integrated Circuit (BMIC). It is responsible for real-time monitoring of the battery’s voltage status, and its working performance directly determines the safety status of the series battery pack. The traditional resistive voltage sampling circuit has the problem of channel leakage current, which will affect the consistency of battery voltage and sampling accuracy. Meanwhile, the level-shifting circuit in the high-voltage domain includes high-voltage operational amplifiers, and a large number of high-voltage MOSFETs result in additional area overhead. Methods This paper proposes a low leakage current battery voltage sampling circuit applied to 14-series lithium batteries. Improved on the basis of the traditional resistive voltage sampling circuit, the channel leakage current can be reduced to the pA level by designing an operational amplifier isolated active drive technology. According to the different voltage domains of the series battery pack, different voltage conversion methods are adopted. The first section of the battery is isolated using a unity-gain buffer, and then voltage conversion is performed through a resistive voltage division method. Batteries from Section 2 to 13 adopt operational amplifier isolated active driving to synchronously follow the voltage across the batteries, and then convert the followed voltage into a ground-referenced voltage through a level-shifting circuit. The voltage sampling process of the highest-section battery consumes the power of the entire series battery pack and will not affect the consistency of the series battery pack. Therefore, the highest-section battery directly uses the level-shifting circuit for voltage conversion. Results and Discussions This paper conducts a detailed design and complete performance verification of the circuit based on the 0.35 μm high-voltage BCD process. The overall layout area of the designed battery voltage sampling circuit is 3105 μm × 638 μm (Fig. 10). From the verification results, it can be concluded that under the different processes and temperatures, after adopting the operational amplifier isolated active drive technology designed in this paper, the maximum channel leakage current is only 48.9 pA. However, the minimum channel leakage current of the traditional voltage sampling circuit is 1.169×10⁶ pA (Fig. 12, Fig. 13). Reduce the impact of the sampling process on battery inconsistency from 18.56% to 2.122 ppm (Fig. 14). In addition, under comprehensive PVT verification conditions, the maximum measurement error of the battery voltage sampling circuit designed in this paper is 0.9 mV (Fig. 15, Fig. 16, Fig. 17). Conclusions This paper proposes an operational amplifier isolated active drive technology to mitigate the issue in traditional resistive voltage sampling circuits where channel leakage current affects battery voltage consistency and sampling accuracy. Through the battery voltage sampling circuit designed in this paper, the maximum channel leakage current is 48.9 pA, the inconsistency of battery voltage is 2.122 ppm, and the maximum measurement error is 1.25 mV. It can achieve extremely low channel leakage current while ensuring sampling accuracy. The low-leakage-current battery voltage sampling circuit proposed can be applied to the 14-series lithium battery management chip.
- Battery voltage sampling,
- Operational amplifier isolated active drive,
- Level shift circuit,
- Low leakage current

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References(25)

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