Display Illuminance Sensor Capacitor to Prevent Photodiode Discharge
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Solution Overview
Problem
Display devices face issues with touch signal interference due to parasitic capacitance between touch lines and data or scan fan-out lines, leading to touch sensing errors.
Innovation Solution
Incorporation of a sensor capacitor between the light receiving element and the first sensor transistor to prevent discharge during high light incidence, improving sensor sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a sensor device is integrated into the display device, then the display area can be expanded by removing separate sensor devices, but the light receiving element may discharge when a large amount of light is incident
Solution Approach 1:
The capacitor is pre-charged to a reference voltage before light incident occurs. When light hits the light receiving element, the capacitor maintains the voltage level and prevents discharge by providing a stable reference potential, thus protecting the light receiving element from voltage fluctuations during high light incidence
Solution Approach 2:
The capacitor acts as an intermediary component between the light receiving element and the sensor transistor. It mediates the voltage stability by storing electrical energy and releasing it when needed, preventing direct voltage discharge from affecting the light receiving element during large light incidence
2Measurement precision
If the sensor capacitor is added to prevent discharge, then the sensitivity and accuracy of the illuminance sensor is enhanced, but the device complexity increases
Solution Approach 1:
The capacitor is integrated within the existing sensor pixel structure, sharing common electrodes and circuit elements with the light receiving element and sensor transistor. This merging approach adds the capacitive function without requiring completely separate components, thus limiting the increase in device complexity
Solution Approach 2:
The capacitor serves multiple functions: it acts as a reference voltage source, prevents discharge during high light incidence, and maintains signal stability for accurate illuminance measurement. This multi-functionality reduces the need for additional dedicated components, thereby limiting complexity increase while achieving multiple performance benefits
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
Prevents discharge of the light receiving element when a large amount of light is incident, enhancing the sensitivity and accuracy of the illuminance sensor.
Implementation Method 1
a sensor capacitor comprising a first capacitor electrode electrically connected to a first electrode of the first sensor transistor, and a second capacitor electrode overlapping the first capacitor electrode and electrically connected to a first electrode of the light receiving element
Implementation Method 2
a light receiving element disposed on the read-out line... an illuminance sensor that detects surrounding brightness
Data Source
AI summary
Provided is a display device including an illuminance sensor. The illuminance sensor includes a read-out line disposed on a substrate and extending in a first direction, a light receiving element disposed on the read-out line, a first sensor transistor configured to control a sensing current based on a voltage of a sensor node, which is a first electrode of the light receiving element, a second sensor transistor configured to supply a reset voltage to the sensor node based on a reset signal, a third sensor transistor configured to electrically connect a first electrode of the first sensor transistor to the read-out line based on a gate signal, and a sensor capacitor comprising a first capacitor electrode electrically connected to the first electrode of the first sensor transistor, and a second capacitor electrode overlapping the first capacitor electrode and electrically connected to the first electrode of the light receiving element.