Ambient Light Sensor Circuit Leakage Compensation
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Solution Overview
Problem
Conventional flat panel display devices have issues with visibility in varying light conditions due to constant screen brightness, increased power consumption, and size/thickness due to separate ambient light sensor circuits, and inaccuracies in sensing ambient light due to leakage currents and temperature effects.
Innovation Solution
An ambient light sensor circuit integrated on the same substrate as the organic electroluminescence or liquid crystal panel, featuring a transistor, capacitive elements, light receiving elements, and switches to control output current and prevent leakage currents, with a temperature sensor and look-up table for adaptive brightness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ambient light sensor circuit is manufactured on a separate substrate, then the sensing function is achieved, but the size, thickness and power consumption of the flat panel display device are increased
Solution Approach 1:
The patent integrates the ambient light sensor circuit directly onto the same substrate as the flat panel display device, merging two previously separate components into a single integrated structure. This eliminates the need for separate substrates and connections, thereby reducing overall device size and thickness while maintaining the ambient light sensing function.
2Stability of the object's composition
If brightness is set to a constant level, then the display function is stable, but power consumption is increased when used in dark places
Solution Approach 1:
The patent implements dynamic brightness control by integrating an ambient light sensor that continuously monitors surrounding light conditions and automatically adjusts the display brightness accordingly. This dynamic adjustment mechanism allows the display to reduce brightness in dark environments, significantly lowering power consumption while maintaining optimal visibility in varying lighting conditions.
Solution Approach 2:
The patent employs a feedback mechanism where the ambient light sensor circuit provides real-time information about surrounding light levels to the display control system. This feedback loop enables automatic brightness adjustment, allowing the display to adapt to changing environmental conditions and optimize power consumption based on actual viewing requirements.
3Productivity
If the output current is changed due to light leakage current during sampling period, then the sampling process is continuous, but the ambient light cannot be exactly sampled
Solution Approach 1:
The patent extracts and separately compensates for the light leakage current component from the total measured current during the sampling period. By identifying and removing this unwanted leakage component, the system can accurately measure the true ambient light signal without being corrupted by the continuous sampling process itself.
Solution Approach 2:
The patent applies preliminary compensation for light leakage current by measuring or estimating the leakage current magnitude before the actual ambient light sampling occurs. This preliminary anti-action allows the system to pre-correct for the expected leakage effect, ensuring that the subsequent ambient light measurement remains accurate despite the continuous sampling operation.
4Duration of action of stationary object
If the output current is changed due to temperature leakage current, then the circuit operates continuously, but the ambient light sensing accuracy is reduced
Solution Approach 1:
The patent incorporates temperature sensing and compensation mechanisms that continuously monitor circuit temperature and provide feedback to correct for temperature-induced leakage current variations. This feedback system allows the circuit to maintain accurate ambient light sensing despite continuous operation and temperature changes by dynamically adjusting for thermal effects.
Solution Approach 2:
The patent compensates for temperature leakage current by detecting temperature changes and adjusting measurement parameters or applying correction factors based on the temperature profile. This parameter change approach allows the system to maintain sensing accuracy across varying temperature conditions while operating continuously.
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
Improves visibility by automatically adjusting screen brightness, optimizes power consumption, reduces device size and thickness, and accurately samples ambient light by mitigating leakage currents and temperature effects.
Implementation Method 1
a first light receiving element PD1... which produces current in response to incident light
Data Source
Figure 1a~1b
Figure 1c~2a
Figure 2b~3
AI summary
Disclosed are an ambient light sensor circuit and a flat panel display device having the same that can automatically control screen brightness by sensing ambient brightness and controlling an output current. The ambient light sensor circuit comprises: a transistor electrically coupled to a first power source; a first capacitive element electrically coupled between a control electrode of the transistor and a first reference power source; a second capacitive element electrically coupled between the first capacitive element and a second reference power source; a first light receiving element electrically coupled between the first and third reference power sources and controlling a coupling voltage of the first capacitive element and charge/discharge voltages of the second capacitive element by conducting current in response to ambient light; a first switch electrically coupled to the transistor and enabling the transistor to output current from the first power source according to the coupling voltage of the first capacitive element; and a second switch electrically coupled between the first light receiving element and the first capacitive element and interrupting a leakage current of the first light receiving element, thereby preventing the coupling voltage of the first capacitive element from being changed.