LED Cooling Power Adjustment via Forward Voltage and Current
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Solution Overview
Problem
Projection-type display apparatuses using LEDs as light sources face excessive power consumption in cooling when adjusting brightness based on surrounding light conditions, as they often maintain constant cooling power regardless of varying applied power levels.
Innovation Solution
A system comprising a light detector, voltage detector, current detector, temperature detector, and controller that adjusts LED brightness and cooling power based on detected brightness, voltage, current, and case temperature to optimize cooling power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of applied cooler electric power is adjusted to maintain case temperature at maximum level when light source power is at upper limit, then the junction temperature will not exceed maximum junction temperature, but the amount of electric power consumed for cooling becomes greater than necessary when light source power is reduced
Solution Approach 1:
The patent applies dynamics by making the cooler electric power adjustment dynamic rather than static. The controller continuously adjusts the cooler electric power based on the actual light source electric power level, transitioning from a fixed maximum cooling approach to an adaptive approach that matches the actual thermal load, thereby reducing unnecessary power consumption when light output is reduced.
Solution Approach 2:
The patent changes the parameter of cooler electric power from a constant maximum value to a variable value that depends on the light source electric power level. By establishing a relationship where cooler power is adjusted proportionally to the light source power reduction, the system adapts cooling intensity to actual thermal conditions, resolving the contradiction between maintaining reliability and reducing energy waste.
2Use of energy by moving object
If the brightness of LEDs is adjusted depending on the brightness of the surrounding area, then the power consumption of the projection-type display apparatus is reduced, but the cooling power must be dynamically adjusted to maintain optimal junction temperature
Solution Approach 1:
The patent implements feedback control where the controller monitors the light source electric power level and uses this information to adjust the cooler electric power accordingly. This closed-loop feedback mechanism ensures that cooling power is automatically adapted to match the actual thermal load generated by the LEDs, maintaining optimal junction temperature while simplifying the control strategy through a direct cause-effect relationship.
Solution Approach 2:
The system applies self-service by using the information already available from the light source power control to automatically determine the appropriate cooling power level. The controller leverages the existing power adjustment signals to directly control the cooling system, eliminating the need for separate temperature sensors or complex thermal modeling, thereby reducing device complexity while maintaining effective cooling.
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 ensures appropriate cooling power consumption even when adjusting applied light source power, reducing unnecessary energy expenditure and maintaining optimal LED temperatures.
Implementation Method 1
Much of the applied electric power is converted into heat, which tends to increase the junction temperature Tj of the LEDs. If the junction temperature Tj of the LEDs goes higher than a certain level, then the light output power of the LEDs is abruptly reduced. Consequently, the projection-type display apparatuses which employ LEDs as a light source usually cool the LEDs so that the junction temperature Tj of the LEDs will not exceed a maximum junction temperature Tj(max).
Implementation Method 2
The LEDs are often cooled by a cooling means such as a Peltier device that is able to adjust the cooling power depending on the amount of applied electric power
Implementation Method 3
The LEDs have a low power conversion efficiency (WPE: Wall Plug Efficiency), which represents the ratio of light output power to applied electric power, in the range from about 5% to 15%. Much of the applied electric power is converted into heat
Data Source
AI summary
There is provided a projection-type display apparatus which solves the problem that when an amount of electric power applied to light sources is adjusted, the amount of electric power involved in the cooling of LEDs becomes greater than necessary. Coolers (107R, 107G, 107B) cool light sources (103R, 103G, 103B). Light sensor (111) detects the brightness of a surrounding area. Light case temperature detectors (112R, 112G, 112B) detect case temperatures which are the temperatures of cases of light sources (103R, 103G, 103B). Light source forward voltage detectors (113R, 113G, 113B) detect forward voltages of light sources (103R, 103G, 103B). Light source forward current detectors (114R, 114G, 114B) detect forward currents of light sources (103R, 103G, 103B). Adjuster (117) adjusts the amount of cooling power of coolers (107R, 107G, 107B) based on the forward voltage, the forward current, and the case temperatures.