Current Mirror LED Driver for Temperature-Compensated Brightness
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Solution Overview
Problem
Semiconductor devices face challenges in maintaining stable current supply to loads like LEDs across varying temperatures, as existing solutions fail to effectively adjust current levels to ensure constant brightness and efficiency.
Innovation Solution
The semiconductor device employs a configuration of current sources and mirrors with specific temperature characteristics, including a constant voltage source and diodes with negative temperature coefficients, to generate currents that adjust positively with temperature, ensuring consistent LED brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional current supply circuits are used, then the circuit structure is simple, but the LED brightness decreases at elevated temperatures
Solution Approach 1:
The patent applies parameter changes by utilizing the temperature coefficient characteristics of different components. Specifically, it combines a first current source with positive temperature coefficient (increasing current with temperature) and a second current source with negative temperature coefficient (decreasing current with temperature). By adjusting the ratio of these opposing temperature effects, the circuit achieves net positive temperature compensation, ensuring LED brightness increases with temperature to counteract the natural brightness degradation of LEDs at high temperatures.
2Illumination intensity
If current is increased to maintain LED brightness at high temperatures, then brightness stability improves, but energy consumption increases
Solution Approach 1:
The patent optimizes energy consumption by precisely controlling the temperature compensation parameter. Instead of simply increasing current, it balances the positive temperature coefficient current source and negative temperature coefficient current source to achieve the minimum current increase necessary to maintain LED brightness. This parameter optimization ensures that energy consumption is minimized while still achieving the brightness stability objective.
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 configuration ensures that the current supplied to LEDs increases with temperature, maintaining constant brightness and preventing brightness reduction, even at elevated temperatures, thereby enhancing the semiconductor device's performance in temperature-varying environments.
Implementation Method 1
a second current mirror CM2 including a input end coupled to the second current source and an output end coupled to a second node
Data Source
AI summary
According to one embodiment, a semiconductor device includes a first current mirror having an output end coupled to a first node, a second current mirror having an output end coupled to a second node, a third current mirror having an input end coupled to the second node and an output end coupled to the first node, a fourth current mirror having an input end coupled to the first node, and an output driver that generate a current based on the fourth current mirror. A current flows to the first current source changes at a first ratio with respect to temperature, a current flows to the second current source changes at a second ratio having a negative correlation with respect to temperature, and an absolute value of the first ratio is smaller than that of the second ratio.