Integrated High-Side Current Sensor with Self-Calibration
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Solution Overview
Problem
Conventional current sensing circuits in wireless charger devices face accuracy issues due to shunt resistor inaccuracies caused by process spread, thermal drift, mechanical stress, and ageing, which are difficult to compensate effectively, especially in high-voltage applications, leading to reduced measurement accuracy over the device's lifetime.
Innovation Solution
An integrated high-side current sensor with a run-time self-calibration capability using a scaled replica of the shunt resistor and a switched-capacitor approach, where a replica shunt resistor is co-located with the main shunt resistor and an analog front-end circuitry, allowing for continuous tracking and compensation of inaccuracies through digital signal processing, eliminating the need for temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external discrete shunt resistors are used, then measurement accuracy is improved, but device complexity and calibration difficulty increase
Solution Approach 1:
The patent integrates the shunt resistor directly into the current sensor chip, merging previously separate components (discrete shunt resistor, amplifier, ADC) into a single integrated device. This eliminates the need for external discrete components while maintaining measurement accuracy through careful layout and matching of the integrated shunt with the analog front-end circuitry.
Solution Approach 2:
The integrated current sensor performs multiple functions within a single device: current sensing through the integrated shunt, signal amplification through the analog front-end, and digital conversion through the ADC. This multi-functional integration simplifies the overall system architecture while preserving measurement precision.
2Device complexity
If integrated shunt resistors are used, then device complexity is reduced, but measurement accuracy deteriorates due to drift over time
Solution Approach 1:
The patent implements a feedback mechanism where the analog front-end circuitry continuously monitors the output of the integrated shunt resistor and applies correction algorithms through the digital signal processing block. This feedback loop compensates for drift and variations in the shunt resistor characteristics over time, maintaining measurement accuracy despite using an integrated shunt.
Solution Approach 2:
The patent employs temperature calibration and compensation techniques that dynamically adjust measurement parameters based on temperature conditions. By changing calibration parameters according to temperature, the system compensates for thermal drift in the integrated shunt resistor, maintaining accuracy across different operating conditions.
3Measurement precision
If temperature calibration is applied, then short-term accuracy is improved, but long-term reliability deteriorates due to inability to compensate post-calibration drifts
Solution Approach 1:
The patent performs calibration measurements during manufacturing to establish baseline correction parameters that are stored in the device. These preliminary calibration actions create a foundation for ongoing accuracy maintenance, allowing the device to self-correct for known drift patterns throughout its operational lifetime without requiring external recalibration.
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
This solution maintains high accuracy over the entire lifetime of the device by continuously compensating for drifts and variations, ensuring precise current measurement in high-side current sensing applications, even after initial calibration, thereby enhancing the reliability of wireless charging systems.
Implementation Method 1
a switched-capacitor reference generator capable of producing a current which is dependent on a bandgap voltage, a clock frequency and a capacitance
Implementation Method 2
an analog front end (amplifier, filter), an analog-to-digital converter (ADC)
Data Source
AI summary
In accordance with an embodiment, a method of measuring a load current flowing through a current measurement resistor coupled between a source node and a load node includes: measuring a first voltage across a replica resistor when a first end of the replica resistor is coupled to the source node and a second end of the replica resistor is coupled to a reference current source; measuring a second voltage across the replica resistor when the second end of the replica resistor is coupled to the source node and the first end of the replica resistor is coupled to the reference current source; measure a third voltage across the current sensing resistor; and calculating a corrected current measurement of the load current based on the measured first voltage, the measured second voltage and the measured third voltage.