Charging Device Switching Element Prevents Battery Over-Discharge
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Solution Overview
Problem
Conventional charging devices fail to adequately prevent over-discharge of lithium ion secondary batteries when the battery pack is left connected to the charging device without an AC power source, leading to potential damage such as short-circuits due to uncontrolled discharging paths formed by internal circuit components.
Innovation Solution
Incorporating a semiconductor switching element connected in series with the discharging resistance circuit and voltage dividing circuits within the charging device, which becomes non-conductive when the AC power source is disconnected, thereby interrupting any discharging paths and preventing over-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay switch is used to interrupt the charging path after charging completion, then the charging path can be interrupted, but the discharging circuit connected to the output side of the relay switch cannot be released from the battery pack
Solution Approach 1:
The patent extracts the discharging path interruption function from the charging path control mechanism. By placing a switching element specifically in the discharging path (between the positive output terminal and the positive terminal of the battery pack), it independently controls discharging interruption without being constrained by the relay switch's positioning. This separates the control of charging and discharging paths, allowing the discharging circuit to be properly released from the battery pack.
2Ease of operation
If component circuit parts of the charging device form a discharge circuit to the battery pack, then the battery pack can be discharged, but over-discharge damage occurs when left connected without power
Solution Approach 1:
The patent applies preliminary anti-action by proactively interrupting the discharging path before over-discharge can occur. The switching element is positioned to preemptively block the discharging circuit formed by component circuit parts (such as resistance elements) when the charging device is disconnected from power. This prevents the harmful effect of over-discharge before it can damage the battery pack, while still allowing normal discharging during active charging operations.
3Reliability
If an exclusive protecting IC or microcomputer is provided in the battery pack, then over-charge and over-discharge can be monitored, but production cost increases
Solution Approach 1:
The patent introduces a switching element as an intermediary component in the charging device's output line that acts as a simple mechanical/electrical barrier to prevent over-discharge. This intermediary switches between conductive and non-conductive states based on charging status, providing protection functionality without requiring complex protecting ICs or microcomputers in the battery pack. This significantly reduces production costs while maintaining essential protection capabilities.
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 over-discharge of secondary batteries even when they are left connected to the charging device without power, using a relatively inexpensive switching unit to ensure battery safety and extend its lifespan.
Implementation Method 1
a semiconductor switching element connected in series with the discharging resistance circuit and voltage dividing circuits within the charging device, which becomes non-conductive when the AC power source is disconnected
Data Source
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AI summary
To prevent a battery pack front being over-discharged even under a state that the battery pack (a secondary battery) is connected to a discharging device that is not connected to an ac input power source for a long time. A charging device (200) has a pair of output lines (L1 and L2) and an anode terminal (O1) and a cathode terminal (O2) of a secondary battery (2) electrically connected between the output lines (L1 and L2) to carry out a charging operation. In the charging device (200) including a component circuit part (a resistance (33), a series connecting circuit of resistances (102,103 and 105), a series connecting circuit of resistances (91 and 92) and an inner circuit part of a shunt regulator (116)) electrically connected by traversing a part between the pair of output lines (L1 and L2), a switching element (121) is inserted between the component circuit part (the resistance (33) or the like) and one of the pair of output lines (L1 and L2). When the charging device (200) is not connected to an input power source (1), the switching element (121) is allowed to be non-conductive to interrupt a discharging path so that the component circuit part does not form the discharging path.