Battery Charger Current Measurement Without Sensing Resistor
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Solution Overview
Problem
Conventional battery chargers in cellular phones use sensing resistors to measure output current, which dissipate power as heat, reducing efficiency and increasing the size of the charger due to the external implementation of these resistors.
Innovation Solution
A switching charger module that measures output current without using a sensing resistor, employing a switching module, controller module, feedback module, and reference voltage generator to regulate charging current and voltage, operating in constant current, constant voltage, and end-of-charge modes to ensure proper battery charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing resistor is used to measure output current in a battery charger, then current measurement is achieved, but power is dissipated as heat reducing efficiency
Solution Approach 1:
The patent removes the sensing resistor from the charging path by extracting its measurement function. Instead of measuring current through a physical resistor in series with the battery, the system uses a current sense amplifier that measures voltage across a small sense node, effectively taking out the power-dissipating component while retaining the measurement capability.
Solution Approach 2:
The patent introduces a current sense amplifier as an intermediary device between the charging circuit and the control system. This amplifier uses a feedback mechanism with a sense resistor connected to the battery negative terminal, allowing indirect current measurement without placing a high-value resistor in the main charging path, thus minimizing power loss.
2Measurement precision
If a sensing resistor is used to measure output current, then current measurement is achieved, but the charger size increases due to external implementation
Solution Approach 1:
The patent merges the current measurement function with the existing battery charger IC by integrating the current sense amplifier and sense resistor into the same package. The sense resistor is connected to the battery negative terminal and the amplifier is integrated within the charger module, combining multiple functions into a single compact unit rather than using separate external components.
3Productivity
If conventional battery charging is used, then charging function is provided, but charging efficiency is reduced due to heat dissipation
Solution Approach 1:
The patent implements a feedback mechanism where the current sense amplifier continuously monitors the charging current through the sense resistor connected to the battery negative terminal. The amplifier's output is fed back to the charger control circuit, enabling real-time adjustment of charging parameters to optimize efficiency and prevent excessive heat generation while maintaining proper charging function.
Data Source
AI summary
A method and apparatus is disclosed to restore or recharge one or more cells of a battery. A switching module sources an element charging current from a first input voltage to the battery when a charging control signal is at a first logical level or sinks an element discharging current from the battery to a second input voltage when the charging control signal is at a second logical level. A controller module provides the charging control signal based upon a comparison of a reference voltage and a control voltage pulse, the control voltage pulse being generated by the controller module in response to a replica current, the replica current being proportional to the element charging current. A feedback module compares a voltage of the battery to a reference voltage to provide a charging error signal. A reference voltage generator module provides the reference voltage in response to the charging error signal, the reference voltage being proportional to a constant current and a duty-cycle of the switching charger when the charging error signal indicates a first mode of operation or a scaled representation of the constant current when the charging error signal indicates a second mode of operation.