LED Driving Circuit PWM Frequency Control for Power Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid Crystal Displays (LCDs) face challenges in minimizing power consumption, especially when using Light Emitting Diodes (LEDs) as light sources, as existing technologies do not effectively manage the turning on and off of LEDs to optimize brightness and reduce power usage.
Innovation Solution
A light source driving circuit with a Pulse Width Modulation (PWM) controller that generates a light source control signal to periodically turn on/off LEDs, allowing them to be turned on again before being completely turned off, thereby adjusting the frequency of the signal to overlap falling and rising times, ensuring continuous light emission with minimal power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If LEDs are turned on and off periodically to control brightness, then power consumption is reduced, but the LED cannot be turned off completely before the next cycle starts, resulting in continuous light emission
Solution Approach 1:
The patent applies periodic action by using PWM to cycle the LED through on and off states at a high frequency. The LED is turned on during the rising edge and turned off during the falling edge of each PWM cycle, creating periodic action that reduces power consumption while maintaining the appearance of continuous light emission through persistence of vision.
Solution Approach 2:
The patent changes the frequency parameter of the PWM signal to a specific range (1 kHz to 100 kHz) where the LED's response time characteristics cause it to appear continuously illuminated. By adjusting this frequency parameter, the system achieves complete turning off between cycles while the human eye perceives continuous light, thereby reducing power consumption without sacrificing perceived brightness.
2Illumination intensity
If the frequency of the light source control signal is increased to maintain continuous appearance, then the LED appears continuously illuminated, but power consumption increases due to more frequent switching
Solution Approach 1:
The patent optimizes the frequency parameter to a specific range (1 kHz to 100 kHz) where the LED's response time characteristics create the illusion of continuous illumination. This frequency range is high enough to maintain continuous appearance through persistence of vision, yet low enough to minimize switching losses and keep power consumption acceptable for mobile devices.
3Use of energy by stationary object
If the LED is turned off completely between cycles, then power consumption is minimized, but the rising and falling times overlap causing incomplete turning off
Solution Approach 1:
The patent adjusts the PWM frequency and duty cycle parameters to control the timing of the LED's rising and falling edges. By optimizing these parameters, the system ensures that the LED's falling time and the next cycle's rising time do not overlap, allowing complete turning off between cycles while maintaining acceptable power consumption levels.
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 solution minimizes power consumption of LEDs, allowing for increased operability in mobile devices by maintaining brightness while reducing power usage, especially in battery-powered devices.
Implementation Method 1
Light Emitting Diodes (LEDs), which are more efficient than the fluorescent lamps in terms of power consumption power, weight, and brightness, may be used as light sources as well
Data Source
AI summary
A display device includes a display panel having a plurality of pixels for displaying an image, a light source on the display panel, and a light source driving circuit configured to drive the light source. The light source driving circuit for driving a light source includes a driving voltage generator configured to supply power to a light source, and a light source controller configured to generate a light source control signal for periodically turning on/off the light source, the light source being turned on again before being turned off completely.