Load Driver Circuitry for Accurate Impedance Sensing
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Solution Overview
Problem
Existing driver circuitry for loads such as audio and haptic transducers faces challenges in accurately determining impedance due to residual current after transitioning from driving mode to sensing mode, leading to inaccurate impedance calculations.
Innovation Solution
The circuitry includes control circuitry to monitor and compare load current with a predefined threshold, delaying or preventing the transition to sensing mode until residual current decays below the threshold, and employing discharge paths and impedance control to actively reduce residual current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the circuitry transitions immediately from driving mode to sensing mode, then the response time is reduced, but the impedance estimation accuracy deteriorates due to residual current interference
Solution Approach 1:
The circuitry performs preliminary current monitoring and comparison before transitioning to sensing mode. The control circuitry checks whether the residual current has decayed below a threshold level, and only then allows the sensing operation to proceed. This preliminary check ensures that impedance estimation is not performed during periods when residual current would corrupt the measurement, thereby maintaining accuracy without excessive delay.
Solution Approach 2:
The circuitry implements a feedback mechanism where the current monitoring circuitry continuously monitors the residual current and feeds this information back to the control circuitry. Based on this feedback, the control circuitry dynamically determines when the residual current has decayed sufficiently to allow accurate sensing. This feedback loop enables automatic adjustment of the timing to balance speed and accuracy.
2Measurement precision
If the circuitry waits for residual current to decay naturally before sensing, then the measurement accuracy is improved, but the operational latency increases
Solution Approach 1:
The circuitry converts the harmful residual current into a useful timing indicator. By monitoring the decay of the residual current, the system uses the naturally decaying current waveform itself as a signal that the load is ready for accurate sensing. The threshold comparison transforms the harmful residual current into a beneficial trigger that automatically indicates when measurement conditions are optimal, eliminating the need for arbitrary waiting periods.
3Productivity
If the circuitry performs impedance sensing during high current operation, then the processing speed is maximized, but the measurement reliability deteriorates
Solution Approach 1:
The circuitry dynamically adjusts its operation mode based on real-time current conditions. Rather than using a fixed timing schedule, the system continuously monitors the current level and adaptively determines the optimal moment to switch to sensing mode. This dynamic approach allows the system to maximize processing speed by sensing as soon as conditions permit, while simultaneously ensuring measurement reliability by only sensing when current has decayed below the threshold.
Data Source
AI summary
Circuitry for driving a load, the circuitry comprising: driver circuitry; and load sensing circuitry, 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, wherein the circuitry is configured to, in response to a request for operation of the circuitry in the load sensing mode: compare an indication of a current through the load to a predefined threshold; and if the indication of the current through the load meets the predefined threshold, prevent or delay operation in the load sensing mode.