Phosphor-Converted LED Incandescent-Like Dimming
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Solution Overview
Problem
Phosphor-converted light emitting diodes (LEDs) do not exhibit dimming behavior similar to incandescent light sources, which is a user-preferred characteristic, due to differences in performance, particularly in color temperature changes with reduced power, leading to increased complexity and cost in drive electronics.
Innovation Solution
Incorporating a blue or near-UV LED with a green or greenish-yellow phosphor and a red phosphor, where the red phosphor's luminescence efficiency remains constant with excitation power, causing the Correlated Color Temperature to increase as output power increases, mimicking incandescent-like dimming behavior with reduced power, while maintaining constant power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pulse width modulation (PWM) is used to dim LEDs, then energy efficiency is improved, but the light output does not match incandescent-like dimming characteristics
Solution Approach 1:
The patent changes the electrical parameters applied to the LED by using alternating current (AC) instead of direct current (DC). The AC current is rectified to create a pulsating DC signal with specific frequency and amplitude characteristics that simulate incandescent bulb dimming behavior, allowing the LED to respond to dimming signals in a way that matches traditional incandescent expectations while maintaining PWM energy efficiency.
2Loss of energy
If incandescent bulbs are replaced with LEDs, then energy consumption is reduced, but existing dimming controls do not work properly
Solution Approach 1:
The patent creates an electrical signal pattern that copies the behavior of traditional incandescent bulb dimming. By rectifying AC power to create a pulsating DC signal with specific temporal characteristics, the system replicates how incandescent bulbs respond to PWM dimming controls, allowing existing dimming infrastructure to work seamlessly with LED replacements without requiring new control systems.
Solution Approach 2:
The invention transforms the electrical parameters from standard DC or simple AC waveforms into a specifically shaped rectified AC waveform. This parameter transformation allows the LED to interpret traditional dimming control signals in the same way incandescent bulbs did, maintaining compatibility across different lighting technologies while preserving energy efficiency benefits.
3Ease of operation
If direct current (DC) is used to power LEDs, then operation is simple, but dimming control compatibility is limited
Solution Approach 1:
The patent introduces dynamic waveform transformation by converting rectified AC into a pulsating DC signal with variable frequency and amplitude characteristics. This dynamic signal allows the LED to respond to different dimming control frequencies while maintaining simple DC-powered operation, effectively bridging between operational simplicity and dimming versatility through adaptive electrical characteristics.
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 allows for a phosphor-converted LED to exhibit incandescent-like dimming behavior with constant power efficiency and increased luminous efficiency at higher power input, matching warm white output at low drive powers and shifting to higher Correlated Color Temperature with increasing drive power, thus replicating the natural dimming of incandescent bulbs.
Implementation Method 1
A light emitting diode (LED) is an electroluminescent device that converts electrical energy to optical energy
Data Source
Figure 1A~2
Figure 3A~3B
Figure 4
AI summary
Phosphor-converted light emitting diodes comprising a blue or near-UV emitting semiconductor device, a yellow-green phosphor, and a red phosphor exhibit incandescent-like dimming behavior in that the Correlated Color Temperature of a white light output decreases with reduced brightness. In one aspect, a light emitting device comprises an LEO emitting blue light, a first phosphor excited by the blue light emitted by the LED and in response emitting green or greenish-yellow light, and a second phosphor excited by the blue light emitted by the LED and in response emitting red light.