Battery Discharge Switch Failure Detection With Limited Pre-Discharge Current
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Solution Overview
Problem
Existing power source devices with a discharging switch connected in series to a secondary battery fail to detect an off impossible failure of the discharging switch, leading to adverse effects such as heat generation and inability to cut off discharge current, which can cause overdischarge and battery deterioration.
Innovation Solution
A power source device with a current limiting switch in parallel with the discharging switch, a current detection circuit, and a controlling circuit that compares the detected current with a threshold to diagnose off impossible failures, preventing heat generation by limiting current flow through a diode during failure detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is connected in parallel with the switching element to detect off impossible failure, then the failure detection capability is improved, but heat generation due to Joule heat of the diode increases
Solution Approach 1:
The patent extracts the diode from the circuit configuration by replacing it with a current detection circuit that measures current without requiring a parallel diode connection. This eliminates the harmful heat generation while preserving the failure detection capability through alternative means (current sensing).
Solution Approach 2:
The patent introduces a current detection circuit as an intermediary element that indirectly detects switching element status by monitoring current flow, rather than directly using a diode in parallel with the switching element. This intermediary approach enables detection without the adverse thermal effects.
2Reliability
If the discharging switch is controlled to detect off impossible failure, then the reliability is improved, but the discharge current cannot be cut off and overdischarge occurs
Solution Approach 1:
The patent implements preliminary action by detecting off impossible failures during pre-charging periods or idle states before normal discharging operations begin. The failure detection is performed in advance, allowing the system to prevent harmful overdischarge conditions before they occur during active operation.
Solution Approach 2:
The patent uses feedback mechanisms where the current detection circuit continuously monitors discharge current and provides information to the control circuit. When an off impossible failure is detected, the feedback loop enables the control circuit to take corrective action (such as preventing further discharge or alerting the user) before overdischarge and battery deterioration can occur.
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 device effectively detects off impossible failures in the discharging switch while minimizing heat generation and ensuring safe operation by limiting current flow, thereby preventing overdischarge and battery deterioration.
Implementation Method 1
a current detection circuit that detects a current of the secondary battery
Implementation Method 2
a switching element such as an FET having a parasitic diode is used for a charging switch and the discharging switch
Implementation Method 3
a current limiting switch that is connected in parallel with the discharging switch, and is switched to an on state to supply a limited current to a load
Data Source
AI summary
A power source device includes: a secondary battery; a discharging switch connected in series with the secondary battery; a current limiting switch that is connected in parallel with the discharging switch, and is switched to an on state to supply a limited current to a load in a pre-discharging period in which the discharging switch is in an off state; a current detection circuit that detects a current of the secondary battery; and a controlling circuit that controls the discharging switch and the current limiting switch to be turned on or off. The controlling circuit includes a failure diagnosis circuit for the discharging switch, and the failure diagnosis circuit compares a detection current of the secondary battery detected by the current detection circuit with a threshold set to a value larger than the limited current in the pre-discharging period, and when the detection current is larger than the threshold, determines that the discharging switch has an off impossible failure in which the discharging switch cannot be switched off.