Driver Circuit Self-Calibration for Accurate Load Impedance Estimation
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Solution Overview
Problem
Existing driver circuitry for loads such as audio and haptic transducers requires extensive testing and calibration to determine impedance, which is unreliable due to manufacturing variations and environmental factors, leading to increased production time and testing costs.
Innovation Solution
The circuitry includes a parameter estimation engine that performs self-calibration to generate circuit parameters for load sensing mode, using a stimulus signal to determine impedance and other parameters without prior knowledge, thereby reducing the need for extensive testing and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If extensive testing and calibration is performed to determine impedance, then measurement accuracy is improved, but productivity deteriorates due to increased production time
Solution Approach 1:
The system performs preliminary self-calibration operations during manufacturing to automatically determine accurate impedance values and store them in memory. This preliminary action eliminates the need for extensive manual testing and calibration during production, thereby improving productivity while maintaining measurement accuracy.
Solution Approach 2:
The driver circuitry performs self-calibration using its own resources (power amplifier, ADC, DAC, memory) without requiring external testing equipment. The system automatically applies test signals, measures responses, calculates impedance values, and stores them for future use, making the calibration process independent and efficient.
2Productivity
If manufacturer-specified impedance values are used, then productivity is improved by reducing testing time, but measurement precision deteriorates due to manufacturing variations and environmental factors
Solution Approach 1:
The system changes the operational parameters of the power amplifier (gain, bandwidth, impedance) during self-calibration to match the actual operating conditions. By measuring impedance at these specific parameter settings, the system obtains accurate values that reflect real-world performance rather than relying on generic manufacturer specifications.
Solution Approach 2:
The system uses feedback from the ADC measurements of the power amplifier's output signal to accurately determine impedance values. The measured voltage and current signals are processed to calculate precise impedance values that are then stored for use during normal operation, ensuring accuracy despite manufacturing variations.
3Productivity
If self-calibration is implemented, then productivity is improved by reducing testing time, but device complexity increases due to additional calibration circuitry
Solution Approach 1:
The system uses the power amplifier and ADC, which are already required for normal operation, to perform self-calibration functions. By making these existing components multi-functional (serving both audio amplification and impedance measurement purposes), the system avoids adding separate dedicated calibration hardware, thereby minimizing the increase in device complexity.
Solution Approach 2:
The calibration functions are merged with the normal audio processing path. The same power amplifier that drives the speaker is used to generate calibration signals, and the same ADC that processes audio feedback is used to measure calibration responses. This merging eliminates the need for separate calibration hardware paths.
Data Source
AI summary
Circuitry for driving a load, the circuitry comprising: driver circuitry; load sensing circuitry; and a parameter estimation engine, wherein the circuitry is operable in: a driving mode of operation in which the driver circuitry supplies a drive signal to a load coupled to the circuitry; and a load sensing mode of operation, for estimating a characteristic of a load coupled to the circuitry based on a signal output by the load sensing circuitry in response to a stimulus signal supplied to the driver circuitry, and wherein the circuitry is operable to perform a calibration operation in which the parameter estimation engine generates a circuit parameter for use in the load sensing mode based, at least in part, on a signal generated by the circuitry in response to a calibration stimulus signal supplied to the driver circuitry.