Battery Charge-Discharge Circuit for Low-Voltage Charger Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional charge and discharge control circuits face issues with erroneous charger connection detection when the charger voltage is lower than the battery voltage, leading to unintentional restoration from the forced stand-by status, and inability to detect charger connection due to incorrect threshold settings.
Innovation Solution
Incorporating a charger connection detector circuit and a pull-up detector circuit that generates signals based on the external negative electrode terminal voltage, allowing the discharge control switching element to be turned off and then on only when reliable charger connection is detected, with additional conditions for charge start detection to prevent parasitic diode charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charger connection detection voltage threshold is set high to detect chargers with lower voltage than the battery, then charger connection can be detected, but erroneous detection occurs immediately after entering forced stand-by status
Solution Approach 1:
The patent applies preliminary action by requiring the external negative electrode input voltage VM to be pulled up to a predetermined voltage level before the charger connection detector circuit becomes active. This preliminary voltage pull-up action prevents erroneous detection immediately after entering forced stand-by status, while still allowing detection of chargers with lower voltage than the battery once the pull-up condition is satisfied.
2Reliability
If the charger connection detection voltage threshold is set low to avoid erroneous detection in forced stand-by status, then detection reliability improves, but chargers with lower voltage than the battery cannot be detected
Solution Approach 1:
The patent uses preliminary action by establishing a voltage pull-up condition as a prerequisite before enabling charger connection detection. This allows the system to maintain a higher effective detection threshold while avoiding erroneous detection in forced stand-by status, thereby resolving the contradiction between detection reliability and detection accuracy for low-voltage chargers.
3Loss of energy
If the discharge control FET is turned off to prevent discharge to load during shipping, then battery consumption is reduced, but the device cannot restore from forced stand-by status when a charger is connected
Solution Approach 1:
The patent applies feedback by using the charger connection detection signal to trigger restoration of the discharge control FET from its forced OFF state. The detection circuit monitors the external negative electrode input voltage VM, and when a charger connection is detected (indicated by voltage pull-up), the system provides feedback to turn on the discharge control FET, enabling restoration from forced stand-by status.
4Ease of operation
If the discharge control FET remains on to allow charger connection detection, then restoration from forced stand-by status is enabled, but parasitic diode charging occurs causing heat loss
Solution Approach 1:
The patent applies preliminary action by requiring voltage pull-up to a predetermined level before allowing charger connection detection to become effective. This preliminary condition ensures that the discharge control FET remains off during the initial phase, preventing parasitic diode charging and heat loss, while still enabling restoration once the pull-up condition is satisfied and a charger is properly connected.
Data Source
AI summary
A charge and discharge control circuit controls charge and discharge of a secondary battery connected between a positive electrode power supply terminal and a negative electrode power supply terminal by using a discharge control switching element and a charge control switching element connected between the secondary battery and a load or a charger and includes a charger connection detector circuit that generates a charger connection detection signal, based on a voltage of an external negative electrode terminal connected to the charger; and a pull-up detector circuit that detects a pull-up of the voltage of the external negative electrode terminal, based on the voltage of the external negative electrode terminal, and generates a pull-up detection signal. The charge and discharge control circuit turns off the discharge control switching element, and then, turns on the same after receiving the pull-up detection signal and the charger connection detection signal.