Panel Impedance Sensing Using Driver Replica Current
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Solution Overview
Problem
Existing display panel impedance and bandwidth testing methods require significant hardware and fail to account for parasitic capacitor loads, leading to inaccuracies in capacitance measurements.
Innovation Solution
A method utilizing a driver replica current to measure panel impedance and bandwidth with minimal hardware, incorporating a driver circuit, current sensor, and current-measurement circuit to determine load capacitance and admittance, while compensating for parasitic capacitor effects through multiple measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional impedance testing methods are used, then hardware requirements are significant, but measurement precision is insufficient due to parasitic capacitor effects
Solution Approach 1:
The patent creates a replica of the driver circuit that copies the exact current waveform delivered to the panel. This replica current is then measured to indirectly determine panel capacitance, avoiding the need for direct complex measurements and eliminating parasitic capacitor interference. The copying approach allows precise capacitance extraction through simple current sensing rather than complex impedance measurement hardware.
Solution Approach 2:
The patent introduces a current sensor as an intermediary element that measures the driver current without being affected by parasitic capacitors. By measuring current rather than voltage or impedance directly, the system uses this intermediary quantity to calculate capacitance, thereby avoiding the harmful effects of parasitic capacitance in the measurement path.
2Ease of operation
If parasitic capacitor effects are ignored, then measurement process is simpler, but measurement precision deteriorates due to measurement errors
Solution Approach 1:
The patent extracts the parasitic capacitor effect from the measurement equation by measuring current at a point where it can be separately accounted for. The method isolates the parasitic current component and subtracts it from the total measured current, leaving only the current attributable to the panel capacitance. This extraction allows simple measurement procedures to yield accurate results.
Solution Approach 2:
The patent uses feedback by measuring the actual driver current and using this information to calculate and compensate for parasitic effects. The measured current serves as feedback to determine the true panel capacitance by accounting for parasitic contributions, thereby maintaining measurement simplicity while achieving high precision through computational compensation.
3Measurement precision
If multiple measurements are performed to account for parasitic capacitance, then measurement precision improves, but loss of time increases
Solution Approach 1:
The patent performs preliminary measurement of the parasitic capacitor current under known conditions before the actual capacitance measurement. This preliminary action characterizes the parasitic effects once, and then this characterization is reused in subsequent measurements, avoiding repeated time-consuming parasitic measurements while maintaining precision through the pre-established parasitic model.
Solution Approach 2:
The patent creates a universal measurement approach where a single current measurement setup serves multiple purposes: it measures both the parasitic current and the total current, from which panel capacitance is derived. This multi-functional use of the same measurement hardware and procedure eliminates the need for separate measurement sequences, reducing time loss while achieving high precision through comprehensive current analysis.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A circuit includes a driver to provide a voltage at a node of a load and a first circuit to facilitate determining a load current at the node. The load is a capacitive load and the first circuit facilitates determining the load current by measuring a replica current and determining a capacitance of the load using values of the voltage and the replica current.