Flexible Charge Control Circuit for Battery Overcharge Shutdown
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in detecting abnormalities such as overcharge and micro-short circuits during wireless charging, leading to potential safety issues and reduced battery life due to repeated charging cycles, while existing protection circuits are bulky and inefficient in minimizing size and power consumption.
Innovation Solution
A charge control circuit using an oxide semiconductor transistor is integrated over a flexible substrate, connected to the battery terminals to detect abnormalities and control charging, preventing overcharge by blocking power supply through switches and reducing power consumption with low leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid substrate (printed wiring board) is used to mount protection circuits, then safety from battery abnormality is secured, but the size of the battery pack increases and space is consumed
Solution Approach 1:
The patent replaces the conventional rigid printed wiring board with a flexible substrate that can be wound around the battery cell. This flexible substrate maintains the necessary electrical connection functions while significantly reducing the space required in the battery pack, directly resolving the contradiction between safety reliability and space consumption.
Solution Approach 2:
The protection circuit is transformed from a planar rigid board structure to a three-dimensional wrapped structure around the battery cell. By utilizing the cylindrical surface area of the battery, the circuit achieves compact integration without compromising safety functions, effectively addressing the space constraint.
2Reliability
If multiple IC chips are mounted on rigid substrates for protection and switching functions, then battery protection is achieved, but the device complexity and number of components increase
Solution Approach 1:
The patent integrates multiple discrete IC chips (protection circuit and switching circuit) onto a single flexible substrate, which is then wound around the battery cell. This merging of multiple components into a unified integrated structure reduces device complexity while maintaining comprehensive battery protection functions.
Solution Approach 2:
The flexible substrate serves multiple functions simultaneously: it acts as the mechanical support structure, provides electrical connections, enables the protection circuit functionality, and facilitates the switching circuit operation. This multi-functionality reduces the need for separate components, thereby reducing overall device complexity.
3Reliability
If conventional protection circuits are used, then overcharge protection is provided, but power consumption is high due to leakage current
Solution Approach 1:
The patent employs oxide semiconductor transistors which fundamentally change the electrical parameters of the protection circuit, particularly achieving extremely low leakage current (less than 1 zeptoampere). This parameter change in the transistor characteristics directly reduces power consumption while maintaining overcharge protection reliability.
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
The solution effectively prevents overcharge and extends battery life by reducing charging cycles, while minimizing the size and power consumption of the protection circuit, ensuring safe and efficient operation of lithium-ion secondary batteries.
Implementation Method 1
a semiconductor device refers to any device that can function by utilizing semiconductor characteristics
Implementation Method 2
a charge control circuit which is connected to the first transmission path and provided over a flexible substrate
Data Source
AI summary
A structure that includes a circuit for controlling the safe operation of a secondary battery but can overcome space limitations owing to miniaturization of the housing is provided. A charge control circuit is provided over a flexible substrate and bonded to an external surface of the secondary battery. The charge control circuit is electrically connected to at least one of two terminals of the secondary battery and controls charging. To prevent overcharge, both an output transistor of a charging circuit and a blocking switch are brought into off state substantially concurrently. Blocking two paths which connect to the battery can quickly stop charging when overcharge is detected and reduce damage to the battery owing to the overcharge.