Battery Charger Constant Current Control Loop
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Solution Overview
Problem
Conventional battery chargers with constant current-constant voltage (CC-CV) control loops face issues such as increased charge time, sensitivity in transitioning from CC to CV, and risk of overcharging due to independent CC and CV control circuits, especially in smaller batteries with higher equivalent series resistance (ESR).
Innovation Solution
A battery charger architecture utilizing a constant current control loop with a Digital Voltage Limiter (DVL) and Accelerated Settle Down (ASD) technique, eliminating the need for a constant voltage loop and amplifier, and incorporating digital controls to dynamically manage charging current, thereby reducing charging time and circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CC-CV control loop is used with independent CC and CV control circuits, then charging current can be regulated during CC and CV phases, but transition from CC to CV causes discontinuity and overcurrent risk
Solution Approach 1:
The patent merges the independent CC and CV control circuits into a unified control architecture where a single control circuit manages both charging phases. This eliminates the discontinuity and overcurrent risk associated with transitioning between separate CC and CV control circuits, while maintaining the ability to regulate charging current throughout the entire charging process.
Solution Approach 2:
The control circuit is designed to perform multiple functions: it operates in CC mode during the constant current phase and automatically transitions to CV mode during the constant voltage phase, all within a single unified control architecture. This multi-functional design eliminates the need for separate control circuits while ensuring safe and continuous charging regulation.
2Productivity
If smaller battery pack is charged with conventional CC-CV charger, then charging should be faster, but charge time increases unexpectedly due to larger ESR
Solution Approach 1:
The patent implements dynamic control parameters that adapt to the battery's equivalent series resistance (ESR). By continuously monitoring charging conditions and adjusting control parameters in real-time, the system optimizes charging current delivery despite variations in battery ESR, ensuring that smaller batteries with higher ESR can be charged at expected speeds without unexpected delays.
3Reliability
If conventional CC-CV charger is used, then charging current can be regulated, but circuit area is larger due to separate CC and CV control circuits
Solution Approach 1:
The patent combines separate CC and CV control circuits into a single integrated control circuit that handles both charging phases. This merger maintains the regulatory control needed for safe charging while significantly reducing the overall circuit area by eliminating redundant components and control logic found in separate CC and CV circuits.
4Reliability
If transition from CC to CV is made sensitive, then overcharging can be prevented, but charging time increases due to PRE-CV relaxation
Solution Approach 1:
The patent employs dynamic transition control that adapts to battery conditions during the CC to CV phase transition. The control circuit dynamically adjusts transition parameters based on real-time battery state, preventing overcharging while minimizing unnecessary charging time extensions that would occur with overly sensitive or fixed transition thresholds.
Data Source
AI summary
It is an object of one or more embodiments of the present disclosure to provide a battery charger with a constant current control loop, for use in linear and switching chargers. Advantages include digital controls and a comparator, for decreasing charging current towards termination. The technique of the disclosure eliminates a constant voltage loop and amplifier, without increasing charging time. The technique also simplifies porting the design to another process technology node, and reduces size.