LED Driving Circuit Dynamic Current Adjustment for Efficiency
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Solution Overview
Problem
Current LED driving methods for LCD backlights have fixed driving current, leading to inefficient operation at non-maximum gray-scale brightness, as they cannot automatically adjust current values based on usage.
Innovation Solution
An LED driving method and circuit that dynamically adjust the current value and duty cycle of the LED driving current by selectively enabling pulse width modulation or direct current dimming modes based on a preset threshold value, allowing for two-stage brightness control and improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed driving current is used to drive LED, then the LED can operate at maximum gray-scale brightness, but the LED works in low efficiency area at non-maximum gray-scale brightness
Solution Approach 1:
The patent implements dynamic current adjustment by switching between PWM dimming mode and DC dimming mode based on the duty cycle value. When duty cycle is less than threshold, PWM mode is used with adjusted current; when duty cycle is greater than or equal to threshold, DC mode is used with proportional current reduction. This dynamic adaptation resolves the contradiction between fixed current operation and efficiency optimization.
Solution Approach 2:
The patent changes the driving current parameter based on the duty cycle parameter. By monitoring the duty cycle and adjusting the current value accordingly (either through PWM modulation or DC proportionality), the system optimizes LED efficiency across different brightness levels, transforming the fixed parameter problem into a variable parameter solution.
2Ease of operation
If PWM signal is used to drive LED for brightness adjustment, then backlight brightness can be dynamically adjusted, but driving current cannot be automatically adjusted according to LED usage
Solution Approach 1:
The patent introduces feedback by monitoring the duty cycle value and using this information to automatically adjust the driving current. The control circuit receives the PWM signal, extracts the duty cycle, and based on this feedback information, automatically selects the appropriate dimming mode and adjusts the current accordingly, achieving automated adaptation without manual intervention.
Solution Approach 2:
The system performs self-adjustment by automatically detecting the duty cycle and selecting the optimal working mode (PWM or DC) without external control. The LED driving circuit serves itself by using the duty cycle information to autonomously optimize its own operation, eliminating the need for external manual adjustment mechanisms.
3Use of energy by stationary object
If fixed driving current is used, then the circuit is simple, but power consumption cannot be optimized at different brightness levels
Solution Approach 1:
The patent segments the brightness control range into two regions: low brightness region (duty cycle < threshold) handled by PWM mode, and high brightness region (duty cycle ≥ threshold) handled by DC mode. This segmentation allows each region to be optimized independently, improving overall energy efficiency while keeping the control logic manageable through clear division of operational modes.
Data Source
AI summary
A LED driving method includes steps of: providing a first pulse width modulation (PWM) signal for determining a brightness of a LED; obtaining a duty cycle of the first PWM signal; and selectively enabling the LED to work with a PWM dimming mode or a direct current (DC) dimming mode according to a relative relationship between a magnitude of the obtained duty cycle and a preset threshold value. Since the LED is performed with a two stage brightness control by use of mixed dimming mode, the driving efficiency of the LED can be improved.