Charge Control Circuit with Sense Resistor Calibration
Solution Overview
Problem
Existing charging circuits face challenges in accurately setting and maintaining a charging current due to variations in the resistance value of the resistive element, especially when it is integrated within an LSI circuit, leading to inaccuracies in charging current estimation.
Innovation Solution
A charge control circuit that integrates a sense resistor and a charging current adjustment circuit, allowing for measurement and adjustment of the resistance value and reference voltage during the inspection process, enabling precise control of the charging current through a voltage conversion circuit, error amplifier, and current adjustment unit, with optional features like a switch pass circuit and subsidiary resistor for improved accuracy and reduced power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sense resistor is integrated within an LSI circuit, then the device complexity is reduced and manufacturing is simplified, but the resistance value varies due to process variation leading to inaccurate charging current estimation
Solution Approach 1:
The patent implements a feedback mechanism by measuring the actual resistance value of the sense resistor through dedicated measurement terminals and using this measured value to calculate and adjust the charging current. The charging current adjustment circuit receives the measured resistance value and adjusts the charging current accordingly, creating a closed-loop feedback system that compensates for resistance variations.
Solution Approach 2:
The patent changes the parameter used for charging current control from a fixed predetermined value to a dynamically adjusted value based on actual measurements. By measuring the actual resistance value and reference voltage, and calculating the charging current based on these measured parameters rather than predetermined values, the system adapts to process variations.
2Measurement precision
If the resistance value of the sense resistor varies, then the charging current cannot be accurately estimated, but providing external resistive elements increases device complexity
Solution Approach 1:
The patent makes the sense resistor serve multiple functions: it acts as both the current-sensing element during normal charging operation and as a measurable component for calibration purposes. By providing measurement terminals that allow the sense resistor's value to be measured during inspection, the same component is used for both its primary function and for calibration, eliminating the need for separate external calibration components.
Solution Approach 2:
The system performs its own calibration by measuring the actual resistance value of its internal sense resistor through provided measurement terminals. Rather than requiring external calibration equipment or components, the charging circuit uses its own internal resources and measurement capabilities to determine and compensate for its resistance variations.
3Reliability
If the resistance value of the sense resistor is not measured and adjusted, then the charging current varies due to process variation, but adding measurement and adjustment features increases device complexity
Solution Approach 1:
The patent performs measurement and adjustment of the sense resistor value during the inspection process, before the product is shipped to the customer. By conducting the calibration action in advance during manufacturing inspection, the system ensures accurate charging current control is established before use, while keeping the measurement and adjustment features integrated into the production flow rather than requiring separate post-manufacturing steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for accurate setting and maintenance of the charging current despite variations in the sense resistor's resistance value, ensuring reliable charging operations by measuring and adjusting the resistance and reference voltage, thereby minimizing current fluctuations.
Implementation Method 1
a voltage drop across the sense resistor and a predetermined reference voltage wherein the sense resistor and the charging current adjusting circuit are integrated
Data Source
AI summary
In a charge control circuit that adjusts a charging current flowing through a battery to be charged from a power supply, a sense resistor is provided on a charging path to the battery from an external power supply. A charging current adjustment circuit adjusts the charging current based on an error voltage between a voltage drop across the sense resistor and a predetermined reference voltage. The charging control circuit is integrated in a package. The charging current is inputted to a current input terminal. A battery terminal outputs the charging current to the battery. The current input terminal and the battery terminal also function as terminals used to measure a resistance value of the sense resistor. A voltage monitoring terminal is provided to measure the reference voltage in an inspection process.