Color LED Driver Temperature Compensation NTC Thermistor
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Solution Overview
Problem
RGB LEDs in LCD backlights experience luminance decrease and color coordinate shifts as ambient temperature increases, requiring a temperature compensation unit to maintain consistent light output and color accuracy.
Innovation Solution
A color LED driver with a temperature compensation unit that includes a negative temperature coefficient (NTC) thermistor and linear compensation resistors connected in parallel, directly integrated into the driving current path to adjust red and green LED driving currents, allowing for compact, low-cost, and feedback-free operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional temperature compensation circuit is used, then color coordinate shift is compensated, but device complexity and cost increase
Solution Approach 1:
The patent combines the temperature compensation function with the existing driving circuit by integrating an NTC thermistor directly into the driving current path. This merging approach allows the compensation function to be achieved without adding a separate, complex feedback circuit, thereby maintaining color coordinate stability while minimizing device complexity.
Solution Approach 2:
The NTC thermistor acts as an intermediary element that senses temperature changes and automatically adjusts the driving current to compensate for color coordinate shifts. This intermediary component enables temperature compensation through passive electrical characteristics rather than requiring active feedback control, reducing overall system complexity.
2Measurement precision
If a feedback structure is implemented, then temperature compensation accuracy is improved, but device size and cost increase
Solution Approach 1:
The driving circuit with integrated NTC thermistor provides self-service temperature compensation by automatically adjusting its own operating characteristics based on temperature changes. The NTC thermistor's resistance changes with temperature, which directly modulates the driving current to red and green LEDs, enabling the circuit to self-correct color coordinate shifts without external feedback control.
Solution Approach 2:
The patent replaces a potential mechanical or electronic feedback system with a passive electrical compensation mechanism. The NTC thermistor utilizes its inherent negative temperature coefficient characteristic to automatically adjust current distribution, substituting complex feedback control with a simple passive electrical element that achieves equivalent or sufficient compensation accuracy.
3Device complexity
If NTC thermistor is directly connected to driving current path, then device size is reduced, but current control linearity may be affected
Solution Approach 1:
The patent applies local quality by connecting the NTC thermistor specifically in the driving current paths of the red and green LEDs, where temperature-induced luminance variations are most significant. This localized compensation approach targets the specific areas needing correction without requiring uniform adjustment across all LEDs, maintaining current control precision while simplifying the overall circuit structure.
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 effectively compensates for temperature-induced luminance variations and color shifts, ensuring consistent light output and color accuracy without the need for a feedback structure, enabling a compact, low-cost, and miniaturized LED driver design.
Implementation Method 1
directly connecting a negative temperature coefficient (NTC) thermistor to a driving current path of a color LED applied to an LCD backlight to compensate a characteristic variation of the LED due to a variation in a temperature
Data Source
AI summary
Disclosed herein is a color LED driver, which is capable of being implemented by a compact structure without a feedback structure and accompanying a small size and low cost, by directly connecting a negative temperature coefficient (NTC) thermistor to a driving current path of a color LED applied to an LCD backlight to compensate a characteristic variation of the LED due to a variation in a temperature. The color LED driver includes a driving constant voltage source 100 which supplies a predetermined driving constant voltage VD; a driving circuit 200 which converts the driving constant voltage VD of the driving constant voltage source 100 into a plurality of driving currents, for driving color LEDs, the plurality of driving currents including red LED driving current Ird, green LED driving current Igd and blue LED driving current Ibd; a temperature compensation unit 300 which compensates variations in the red LED driving current Ird and the green LED driving current Igd due to a variation in a temperature, among the plurality of driving currents from the driving circuit 200; and an LED unit 400 including a plurality of color LEDs which are turned on by the driving currents from the temperature compensation circuit 300 and the driving current from the driving circuit 200.