LED Array Phase Shift PWM for Projection Luminance Control
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Solution Overview
Problem
Existing projection technologies face challenges in efficiently driving light emitting diodes (LEDs) to achieve accurate gradation display and prolong the lifetime of light emitting elements, as current methods either delay response time or lead to disproportionate light emission duration among LEDs.
Innovation Solution
The solution involves dividing an LED array into groups and controlling the number of LEDs emitting light to achieve desired luminance levels, rather than adjusting driving current, and using pulse width modulation with a phase difference to ensure consistent and efficient light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the driving current is adjusted in an analog manner to reduce luminance, then power consumption is reduced, but the response time is increased
Solution Approach 1:
The patent applies pulse width modulation (PWM) to control LED luminance by periodically switching the driving current on and off. Instead of using analog current adjustment which causes slow response, the system uses digital pulse signals with varying duty cycles to achieve both dimming and fast response. The PWM frequency is set higher than the LED's response frequency, enabling precise luminance control without response delay.
Solution Approach 2:
The patent changes the control parameter from analog current magnitude to digital pulse width (duty cycle). By varying the ON-time portion of the pulse signal while maintaining a fixed high-frequency switching rate, the system achieves luminance adjustment without the response time penalty associated with analog current control. This parameter transformation resolves the contradiction between energy efficiency and response speed.
2Loss of energy
If the number of light emitting diodes emitting light is reduced to achieve dimming, then power consumption is reduced, but the light emission duration of individual LEDs increases
Solution Approach 1:
The patent segments the LED array into multiple independently controllable groups or individual LEDs. Instead of reducing the number of active LEDs which increases emission duration and reduces reliability, the system uses PWM to control each segment's duty cycle. This segmentation enables all LEDs to operate with balanced, shorter emission durations while achieving overall dimming through reduced average power consumption.
Solution Approach 2:
By applying periodic PWM switching to multiple LED segments, the system ensures that each LED emits light for a controlled, limited duration within each cycle. The cumulative effect of many LEDs with short, periodic emission intervals achieves the desired luminance level while preventing any single LED from experiencing excessive emission duration and reduced lifetime.
3Ease of operation
If analog current adjustment is used for dimming, then gradual luminance control is achieved, but response speed decreases and gradation display accuracy is hindered
Solution Approach 1:
The patent replaces the mechanical/analog current control system with a digital pulse modulation system. Instead of continuously variable analog currents that are slow to respond, the system uses digital PWM signals that can be rapidly switched and precisely controlled. This substitution of control mechanism maintains ease of luminance adjustment while dramatically improving response speed and gradation accuracy through digital processing capabilities.
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 approach allows for improved response speed and even light emission distribution, enhancing the quality of projection images and extending the lifespan of all light emitting elements.
Implementation Method 1
a light source section including a plurality of light emitting elements (LEDs)
Data Source
Figure 1
Figure 2(A)~2(E)
Figure 3
AI summary
A projection apparatus (10) projecting images of respective color components sequentially includes a light source section (17 to 20) having a plurality (n) of light emitting elements (17) (where n is a natural number greater than one), and a driving control section (24, 23) for driving each of the (n) light emitting elements (17) making up the light source section (17 to 20), by a pulse width modulation scheme with a phase difference based on λ/n (where λ is a lighting period unit), in synchronism with a projection period unit of the image of each color component.