Voltage Converting Circuit for Series Battery Cell Selection
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Solution Overview
Problem
Existing voltage converting circuits face challenges in accurately converting the voltage of series connected power storage devices to a reference level without increasing the breakdown voltage of switch elements or circuit size, especially as the number of cells increases, leading to inefficiencies and inaccuracies in voltage measurement.
Innovation Solution
A voltage converting circuit that uses a selection circuit to connect a power storage device to an output node pair and a sampling circuit to sample the voltage using a predetermined potential, employing switch elements with a drive circuit that generates a constant drive voltage based on a drive current from the selected power storage device, and includes a judging circuit to determine the appropriate switch configuration for turning on the transistors, thereby maintaining constant breakdown voltage and reducing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of series connected cells is increased to achieve higher power supply voltage, then the power capacity and energy density are improved, but the gate-source breakdown voltage required for MOS transistors in the selector circuit increases, leading to increased manufacturing cost and element surface area
Solution Approach 1:
The patent divides the selector circuit into multiple stages, where each stage handles a subset of cells. For example, with 10 cells, the first stage divides them into two groups of 5, and subsequent stages further divide these groups. This segmentation reduces the gate-source breakdown voltage requirement at each stage compared to a single-stage circuit that would handle all cells simultaneously.
Solution Approach 2:
The patent transitions from a one-dimensional single-stage selector circuit to a multi-dimensional multi-stage architecture. By adding the dimension of circuit stages, the system can handle higher voltages without proportionally increasing the breakdown voltage requirement for individual transistors, as each stage operates at a reduced voltage level.
2Device complexity
If a multi-stage selector circuit is adopted to reduce gate-source breakdown voltage, then the breakdown voltage requirement is halved at each stage, but the circuit surface area increases due to the increased number of elements
Solution Approach 1:
The patent merges common functional elements across multiple stages to reduce overall circuit area. For example, voltage reference circuits, control logic, and certain transistor configurations are shared between stages rather than duplicated, thereby reducing the total number of elements while maintaining the multi-stage voltage reduction benefit.
3Power
If the number of series connected cells is increased, then the power capacity is improved, but the error in converting cell voltage to ground level increases due to potential differences
Solution Approach 1:
The patent introduces intermediate voltage reference points at each stage of the multi-stage selector circuit. These intermediaries serve as local ground references that reduce the potential difference between the selected cell and the measurement system, thereby minimizing conversion errors and improving voltage measurement accuracy even when measuring high-voltage cells in long series strings.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively avoids the increase in breakdown voltage and circuit size, allowing for accurate voltage conversion and uniform control of series connected power storage devices, while minimizing the impact of parasitic capacitance on measurement accuracy.
Implementation Method 1
a drive circuit that generates a certain drive voltage for turning on the switch element based on a certain drive current flowing from the selected power storage device to the predetermined potential
Data Source
AI summary
A voltage converting circuit and a battery device, aimed at the problem that the breakdown voltage required for the driving input of the selected switch element is increased as the potential of the selected power storage device is increased when a power storage device is selected from a plurality of power storage devices that are connected in series. A certain drive voltage for turning on p-type MOS transistors Q3, Q4 of selection circuit 121 is generated based on a certain drive current Ion flowing from one power storage element to ground level GND. In other words, even if the power storage device selected by selection circuit 121 has a high potential with respect to ground level GND, the drive voltage applied between the gate and source of MOS transistors Q3, Q4 can be held substantially constant.