Light Sensing Circuit Temperature Compensation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional light sensing circuits experience sensitivity variations due to ambient temperature changes, leading to inaccurate brightness detection as current generated by photodiodes varies with temperature, resulting in saturated output values regardless of light brightness.

Innovation Solution

Incorporating a temperature sensing unit and controller to adjust the light sensing time period and output current duration based on ambient temperature, ensuring the light sensing circuit operates below saturation levels and maintains consistent sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the light sensing time period is extended to improve brightness detection accuracy, then measurement precision is improved, but the photodiode operates in saturation region at high temperatures causing output values to become insensitive to light brightness changes

Engineering Contradiction:

Improvebrightness detection accuracyVSAvoidsensitivity consistency across temperatures

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The light sensing time period is made dynamic by adjusting it according to temperature. The controller extends the sensing time at lower temperatures to improve measurement precision, and reduces it at higher temperatures to prevent saturation, thereby maintaining sensitivity consistency across different temperature conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The operating parameters of the photodiode are changed based on temperature. By modifying the light sensing time period as a controllable parameter, the system adapts the photodiode's operating conditions to avoid saturation at high temperatures while maximizing measurement precision at lower temperatures

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the light sensing time period is reduced to prevent saturation at high temperatures, then reliability is improved, but measurement precision deteriorates due to insufficient light integration

Engineering Contradiction:

Improvesensitivity consistency across temperaturesVSAvoidbrightness detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts the light sensing time period based on real-time temperature conditions. At high temperatures, the time period is reduced to prevent saturation and maintain reliability, while at lower temperatures, it is extended to ensure sufficient light integration for accurate measurement

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The controllable parameter (light sensing time period) is modified according to temperature to optimize both reliability and measurement precision. The controller selects appropriate time period values that prevent saturation at high temperatures while ensuring adequate light integration at lower temperatures

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a fixed light sensing time period is used to simplify circuit operation, then ease of operation is improved, but the circuit cannot adapt to temperature variations causing sensitivity drift

Engineering Contradiction:

Improvecircuit control simplicityVSAvoidtemperature adaptation capability

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The system implements feedback control by monitoring temperature and automatically adjusting the light sensing time period accordingly. The controller receives temperature information and modifies the sensing parameters in real-time, enabling the circuit to adapt to temperature variations without manual intervention

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The fixed sensing time period is replaced with a dynamic, temperature-dependent time period. The controller automatically adjusts the sensing duration based on temperature conditions, providing both ease of operation and temperature adaptability

Inventive Principle:

Principle #15Dynamics

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

This approach maintains consistent sensitivity of the light sensing circuit across varying temperatures by controlling the light sensing time and output current duration, preventing saturation and ensuring accurate brightness detection.

Implementation Method 1

The photodiode D senses light incident from the outside and generates current according to the brightness of the light

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS8704812B2Light sensing circuit having a controlled light sensing period or a controlled current output period according to ambient temperature, method of controlling the same, and touch panel comprising the light sensing circuit

Publication Date: 2014.04.22 SAMSUNG DISPLAY CO LTD

AI summary

A light sensing circuit, a method of controlling the same, and a touch panel including the light sensing circuit. In the method of controlling the light sensing circuit, including sensing light incident on a photodiode, generating current corresponding to the brightness of the sensed light, amplifying the current using a driving transistor, and outputting the amplified current, the ambient temperature is sensed, and a time period during which the light is sensed by the photodiode or the amplified current is output is controlled by the sensed ambient temperature. Thus, the sensitivity of the light sensing circuit may be constantly maintained without being influenced by the ambient temperature.