Battery Charger Current Supply Circuit Offset Voltage Reduction
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Solution Overview
Problem
Conventional battery chargers face challenges in providing precise charge currents and maintaining accurate voltage levels due to offset voltages caused by mismatched driving capabilities of diodes and current sources, leading to instability and reduced accuracy in constant current and constant voltage charging modes.
Innovation Solution
A current supply for battery chargers that includes a driving transistor, a sensing transistor, a pulling low transistor, a constant voltage controller, and a constant current controller, which dynamically adjust the charge current and voltage to maintain precise charging conditions, along with a constant power controller for thermal regulation, reducing chip circuit area and enabling easy frequency compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diodes and current sources are used in the control circuit, then the charging function is provided, but offset voltages occur due to mismatched driving capabilities, reducing accuracy and stability
Solution Approach 1:
The patent changes the electrical parameters of the control circuit by replacing diodes with transistors and adjusting current source configurations. This parameter change eliminates the driving capability mismatch that causes offset voltages, thereby improving both voltage accuracy and charging stability simultaneously
Solution Approach 2:
The patent uses transistor copies with matched characteristics to replace conventional diodes. By creating precise electrical copies with identical driving capabilities, the mismatch-induced offset voltages are eliminated, improving measurement precision while maintaining system reliability
2Adaptability or versatility
If separate control circuits for constant current and constant voltage modes are used, then both charging modes are supported, but the circuit area increases and complexity increases
Solution Approach 1:
The patent merges the separate constant current and constant voltage control circuits into a unified control architecture. By combining the control functions and sharing common components, the chip circuit area is reduced while maintaining the ability to support both charging modes through a single integrated circuit
Solution Approach 2:
The control circuit is designed with universal components that can perform multiple functions. The same transistors and control elements are used for both constant current and constant voltage modes, enabling the circuit to adapt to different charging requirements without requiring separate dedicated circuits for each mode
3Productivity
If high power is delivered to fast charge the battery, then charging speed increases, but thermal runout risk increases due to excessive power dissipation
Solution Approach 1:
The patent implements a feedback control mechanism that continuously monitors the charging process and adjusts power delivery accordingly. By using feedback to detect temperature or power dissipation levels, the system can reduce power when thermal limits are approached, enabling fast charging while preventing thermal runaway through dynamic adjustment
Solution Approach 2:
The charging system transitions from static fixed-power delivery to dynamic power adjustment. The power delivery is made variable and adaptive, allowing the system to optimize charging speed while responding to thermal conditions in real-time, thus preventing thermal runaway while maintaining high productivity
Data Source
AI summary
Provided is a current supply for providing a charge current to a load. The current supply includes: a driving transistor, providing the charge current to the load; a sensing transistor, limiting the charge current; a pulling low transistor, pulling low a controlling node which controls the driving transistor and the sensing transistor; a constant voltage controller, pulling up the controlling node, controlling the conduction state of the driving transistor and accordingly maintaining the voltage across the load at the first reference voltage, when a voltage across the load rises up and comes close to a first reference voltage; and a constant current controller, controlling the controlling node and the pulling low transistor to limit the charge current to be constantly provided to the load, when the voltage across the load drops much lower than the first reference voltage.