Battery Charging Circuit Stability via Stage Segmentation
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Solution Overview
Problem
Existing battery charging circuits face system instability due to unsmooth switching among multiple control loops for variables like system voltage, charging current, and battery voltage, leading to inefficiency and complexity.
Innovation Solution
A battery charging circuit design incorporating a switching circuit, bias reference circuit, bias generator, comparison circuit, constant time period control circuit, and logic circuit, which proportionally integrates feedback and reference signals to generate control signals for switches, stabilizing the charging process through distinct charge stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple control loops are used to control charging current, system voltage, and battery voltage, then the charging process can be precisely controlled, but system instability occurs due to unsmooth switching among the control loops
Solution Approach 1:
The charging process is segmented into distinct stages (constant current charging stage and constant voltage charging stage) with clearly defined transition conditions. Each stage has its own dedicated control loop, avoiding the instability caused by continuous switching among multiple overlapping control loops. The segmentation is implemented through stage determination logic that switches between control modes based on battery voltage thresholds.
Solution Approach 2:
The control system dynamically adjusts the charging parameters and control mode based on the battery's real-time state. During constant current charging, the system maintains a fixed charging current; when the battery voltage reaches the threshold, it dynamically transitions to constant voltage charging mode. This dynamic adaptation ensures smooth operation across different charging phases without causing system instability.
2Adaptability or versatility
If multiple control loops with multiple variables are used, then comprehensive control of charging parameters is achieved, but the system complexity increases
Solution Approach 1:
The control system merges the control of charging current and system voltage into a unified dual-loop control architecture. The outer loop controls the charging current based on battery voltage feedback, while the inner loop regulates the system voltage. This merging reduces the number of independent control loops needed and simplifies the overall control structure while maintaining comprehensive control capability.
Solution Approach 2:
The control system uses a universal control framework that handles both constant current and constant voltage charging modes through the same basic control loops. The existing dual-loop structure (current loop and voltage loop) serves multiple functions by simply changing the control objectives and feedback weights, eliminating the need for separate dedicated loops for each charging mode.
3Productivity
If traditional charging control is used, then the charging process can be initiated, but system efficiency is reduced due to instability and oscillations
Solution Approach 1:
The system implements comprehensive feedback mechanisms where the battery voltage is continuously monitored and fed back to the control logic. This feedback determines the charging stage and adjusts the control parameters accordingly. The feedback loop ensures that the system responds appropriately to battery state changes, maintaining stability and preventing oscillations that would reduce charging efficiency.
Solution Approach 2:
The control system changes key operating parameters based on the charging stage. During constant current charging, the charging current is maintained at a reference value while the system voltage is regulated. When the battery voltage reaches the threshold, the system changes parameters by switching to constant voltage mode where the system voltage is clamped to the battery voltage and the charging current naturally decreases. These controlled parameter changes improve both stability and efficiency.
Data Source
AI summary
A control method for controlling a battery charging circuit having at least one switch, includes: generating a first difference signal based on the difference between a charging current feedback signal and a charging current reference signal; generating a bias reference signal by proportionally integrating the first difference signal when the battery voltage is higher than a first threshold and less than a second threshold; generating a bias signal by proportionally integrating the difference between the sum of the bias reference signal and a system voltage reference signal and a system voltage feedback signal; generating a comparison signal by comparing the sum of the system voltage feedback signal and a ramp signal with the sum of the bias signal and the system voltage reference signal; and generating a control signal for controlling the at least one switch based on the comparison signal and a constant time period control signal.