Load Switch Circuit Dynamic Mode Switching for Battery Charging
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Solution Overview
Problem
Mobile devices experience performance and battery lifetime issues due to overshoot and undershoot of charging and discharging currents when the external power source operates abnormally or the load of components varies abruptly, as existing switching power supply circuits fail to efficiently control these currents.
Innovation Solution
A load switch circuit comprising a charging transistor, current sensor, voltage sensor, selector, current controller, and mode controller, which selectively switches between voltage control and current control modes based on the magnitude of charging and discharging currents to regulate the charging and discharging processes efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a switching power supply circuit is used to charge the battery, then charging speed and power delivery are improved, but current overshoot and undershoot occur when external power sources operate abnormally or load varies abruptly
Solution Approach 1:
The patent implements dynamic control mode switching between voltage control and current control based on real-time operating conditions. The controller monitors the state of the charging transistor and external power source to determine when to switch between control modes, enabling the system to adapt to varying load conditions and prevent current overshoot/undershoot while maintaining high charging speed.
Solution Approach 2:
The patent employs feedback mechanisms where the controller continuously monitors the charging current, voltage, and transistor state. Based on this feedback, the controller adjusts the control mode (voltage or current control) to maintain stable current flow during battery charging, preventing harmful current variations while preserving fast charging capability.
2Reliability
If voltage control mode is used during battery charging, then battery voltage stability is improved, but current variations and overshoot occur when load changes abruptly
Solution Approach 1:
The system dynamically switches between voltage control mode and current control mode based on real-time conditions. When voltage stability is prioritized, voltage control mode is used; when current precision is needed during load transitions, the system switches to current control mode, thus resolving the contradiction between voltage stability and current control precision.
Solution Approach 2:
The patent changes the control parameter dynamically - switching between controlling voltage and controlling current based on the charging stage and load conditions. This parameter switching enables the system to achieve both voltage stability during normal charging and current precision during load transitions, eliminating the trade-off between these two requirements.
3Measurement precision
If current control mode is used during battery charging, then current precision is improved, but charging efficiency decreases due to increased transistor voltage drop
Solution Approach 1:
The system uses dynamic mode switching to apply current control mode only when high current precision is required (during load transitions or critical charging stages), and switches to voltage control mode during stable charging phases to minimize power loss. This temporal separation of control modes optimizes both current precision and charging efficiency.
Solution Approach 2:
The patent applies current control mode partially - only during specific critical periods when current precision is essential - rather than continuously. This partial application of current control achieves necessary precision while minimizing the associated power losses during the majority of the charging process where voltage control is sufficient.
4Device complexity
If a simple switching power supply circuit is used, then device complexity is reduced, but the circuit cannot efficiently control charging and discharging currents under abnormal conditions
Solution Approach 1:
The patent implements a multi-functional controller that performs multiple roles: monitoring transistor state, detecting external power source conditions, determining control mode, and executing switching control. This universal controller enables the circuit to handle both normal and abnormal conditions with enhanced reliability while maintaining relatively simple circuit architecture through functional integration.
Data Source
AI summary
A load switch circuit includes a charging transistor, a current sensor, a voltage sensor, a selector, a current controller and a mode controller. The charging transistor is connected between a first switch node and a second switch node and controls a charging current in response to a charging control signal. The current sensor is connected to the first switch node and the second switch node and senses the charging current to generate a current sensing signal. The voltage sensor is connected to the first switch node and the second switch node and senses a source-drain voltage of the charging transistor to generate a voltage sensing signal. The selector selects the current sensing signal or the voltage sensing signal in response to a mode signal to generate a selection voltage signal. The current controller compares the selection voltage signal with a reference voltage to generate the charging control signal.