Display Panel Current Sensing with PCB Resistance Compensation
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Solution Overview
Problem
The resistance of sensing resistors in display devices is affected by parasitic resistance generated by the printed circuit board, leading to inaccuracies in power current sensing, and this issue is exacerbated by temperature variations.
Innovation Solution
A display device with a current sensor that includes a sensing resistor, a sensing current determiner, and a constant current generator, which compensates for resistance dispersion and temperature effects by determining sensing resistances and currents based on test and driving periods, using temperature-compensation lookup tables and analog-digital converters to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensing resistor is used to sense power current, then current sensing is enabled, but measurement precision deteriorates due to parasitic resistance from the printed circuit board
Solution Approach 1:
The patent applies preliminary action by performing a test measurement before actual operation to determine the actual resistance value of the sensing resistor. The controller measures the voltage across the sensing resistor when a known test current flows through it, calculates the actual resistance, and stores this value for subsequent compensation during normal operation. This preliminary characterization eliminates the need for complex real-time compensation circuits while maintaining high measurement precision.
2Device complexity
If a simple sensing resistor configuration is used, then device complexity is reduced, but measurement precision deteriorates due to temperature-induced resistance changes
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage across the sensing resistor during normal operation and using the pre-determined actual resistance value to calculate the accurate power current. The controller reads the voltage signal from the sensing resistor, applies the compensation formula using the stored actual resistance, and determines the precise current value. This feedback mechanism maintains high measurement precision throughout the display device's operating temperature range without requiring complex temperature compensation hardware.
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 enhances the accuracy of power current sensing by compensating for resistance dispersion and temperature-related resistance increases, ensuring precise determination of sensing currents and improving operational reliability.
Implementation Method 1
a voltage applied to opposite electrodes of the sensing resistor is measured
Implementation Method 2
a constant current generator configured to generate a constant current to provide to the sensing resistor in a test period
Implementation Method 3
the sensing current may be determined by dividing the driving sensing voltage by the first sensing resistance
Data Source
AI summary
A display device includes: a display panel including pixels, a power voltage generator for applying a power current to the display panel in a driving period; and a current sensor including a sensing resistor disposed between the display panel and the power voltage generator; a sensing current determiner for determining a sensing current; and a constant current generator for generating a constant current to the sensing resistor in a test period. The sensing current determiner determines a test sensing current based on a test sensing voltage applied to opposite electrodes of the sensing resistor in the test period and an initial sensing resistance, determines a first sensing resistance based on the test sensing current, the initial sensing resistance, and the constant current, and determines the sensing current based on a driving sensing voltage applied to the electrodes of the sensing resistor in the driving period and the first sensing resistance.