13/10/2011

How does LED power work in the past 90s

With the advent of Dell Inspiron 1525 Battery power LEDs (> 0.25 W) in the late 90s and white LEDs, optics, especially in several areas changed significantly. Therefore, the effectiveness of these components have their size and mode of administration developed and / or improving the lighting in front of the old technologies (incandescent lamps with high pressure, high and low).


The electronics associated with these new components (LED) also had to adapt and offer new solutions to this strong growth to continue the development of new optical solutions to provide and maintain, especially for the optical performance of optimal power LED maintained.


In this paper we present two modes of energy are used, the LED driving DC and pulsed current.


However, it is important to note that many applications use a voltage mode LED control, namely the electronic management system is to control the current through the diode (which must be done) is connected, but evaluate the current- tension (stable) is applied to the connections of the Dell Inspiron 1545 Battery components.


These systems are robust and have a life are often more complex review of the performance, but also significant drawbacks. Therefore, a slight increase in flux through the voltage across an LED to a significant change in the way. In addition, LEDs are arranged in the flow of light and a given current and Dell Latitude D820 Battery voltage (Vf) are different, even within the same game.


These considerations and voltage mode control will be discussed in another paper.


Two Types of food


Power supplies and other regulatory authorities provide a fixed output voltage of the output current is a constant.


The LED should go by the current, ie, the electronic control to adjust the LED current through them, are prepared independently of the number of LEDs in series, to be conducted.


The two control modes are the most common:


DC-control PWM (Pulse)


2.1. DC control


The relationship between voltage and current supplied to light emitting diode (LED) is not linear. Therefore, a small increase in the voltage across the leads to a significant increase in the flow and thus the light output.More importantly, an excessive load on the results in damage to high-speed LED current Dell Latitude D620 Battery components.Therefore, the power control is better (for a control voltage) to control the flow of light output on the one hand, and secondly, to ensure that the current in the LED does not exceed the maximum threshold of LED.


In addition, the color coordinates of white LEDs, depending on the current font. Therefore, if a driver holds the LED in parallel (ie, a control voltage), the current through each LED is different and perhaps significant differences in chromaticity coordinates between each LED.


2.2. PWM


This type of control is the most commonly used for LED (among others) because they are not very sensitive to food PWM (Pulse Width Modulation).


It maintains the functionality of "priming" (change of flux LED), most of the LED driver. All these components are integrated in many cases by an inductance, capacitance, diodes, transistors, resistors and power usually accompanied.


Influence of the third power


Many Dell Inspiron 6400 Battery studies have been conducted to show the redshift of the LED based on a semiconductor junction temperature. Thus, it was Kish and arrow (2), Nakamura (3), Tamura (4), Hong et al (5) the red LED (AlInGaP), the maximum wavelength increases linearly with the resulting combination of the temperature. In general, LED red, green and blue have a different temperature sensitivity of the union, and the red LED is the most sensitive, followed by green and blue.


The current density also affects the spectrum of the LED (match-Muller et al., 2002), but also their effectiveness.Below, we have been on the influence of the Dell Inspiron 6000 Battery power LED (high power) study focused on research in the light (Rensselaer Polytechnic Institute in New York) has made.So let's see what kind of performance won (continuous or pulsed) spectrum LED by using a different intensity.


What interests us in the case of high brightness 1W LED currently available for various applications (backlight, lighting (map lights in the aircraft (Airbus A320) in the Railways (SNCF used)).


Their technology (blue + yellow phosphor or RGB LED), the effect of food is more or less pronounced.


3.1 The technology of phosphorus


The following graphs show a white LED (blue + yellow phosphor emission), the color change of coordinates for the different types of Dell Vostro 1500 Battery supply current (DC) and pulsed (PWM).Feed the same number of LED currents (35mA to 350mA, the rated current) shows that the change in color coordinates of a LED control (CC panel) is much more pronounced (dx> 0, 05 and Dy> 0, 15) with a control pulse (Dx> Dy 0.001 to> 0.004)


In addition, the development of the deviation of the color in the opposite direction, whereby the current flow, the color temperature of the LED (cool white), while the same increase in current in pulsed mode reduces the color temperature of the LED.


It should also be noted that the two events are in the color table in the same direction.


However, in the spectra of PWM DC-look


Notice is lit for the first time, the blue tip, characteristic peak of the white LED technology with a semiconductor blue + yellow phosphorus.


This change is the opposite, as the power mode (DC or PWM), but we also see that it is very important.Also in view of the red, ie the group of 620-660 nm, there is really no significant difference in the way two different streams for use.On the contrary, we see that the biggest difference in the range 530-580nm is.In this Dell Vostro 1700 Battery area is increasing the phosphorus supply when the power is reduced to a continuous supply. This evolution of the efficiency of phosphorus has not yet been investigated, and only a few lines of study may explain the phenomenon:


A decrease in temperature, the output of phosphorus


Drift wave lengths below would also be an explanation for the improved performance or phosphorus,Also in this 530-580nm range, decreases the contribution of phosphorus with a PWM power supply along the river.An interesting thing is to compare the emission spectrum of the LED with the response of the eyeThe curve of the eye (a) nm is combined with the "peak" of the LED emission around 550. And "in this area (500-600nm), where the eye is most sensitive to the two modes of Dell Inspiron 1521 Battery power cause the greatest shift of the spectrum, according to the current application.


Therefore measure the importance of leadership style and its impact on the emission spectrum of the LED (so that the color rendering and efficiency of these LEDs).


3.2 The RGB technology


We can use the same thought about RGB LEDs.


In the diagram 2 (Diag.2a and 2b) shows the evolution of the color coordinates of the two types of power supplies (DC PWM) after the current one.


A first step is to see that this Dell Inspiron XPS GEN 2 development is not in the same direction (as for the technology blue chips + P). To monitor the development of the curve almost perpendicular to the emission of black body, while the name of a control pulse (PWM) is almost. This leads to two questions:In continuous mode, the result is an "iso-CTC" and thus the current management has an influence on the color temperature of LEDs.


The development of the coordinates of the LED color when the control pulses for the different currents that set the color temperature (CCT) for various applications (hot or cold);If we look at the phosphorus spectrum technology now in both cases (continuous and pulsed), the downward trend of the peak at about 450-470nm is confirmed.


In fact, we have realized in the case of LED fluorescent only the 500-600nm range, a significant change in the spectrum of the flows of different foods.


In contrast, the red peak (630-660nm) is very variable in its intensity (relative) in a case like the others. To check the Dell Inspiron E1705 Battery DC, the variation is greater with a stabilization "of the summit at about 640 nm red. In PWM, the variation is less pronounced, but at the same time a slight tendency of the red peak. The development between the two modes is However, change.


The last point in relation to the green wavelength, the ongoing management of knowledge and leads to an increase in the drift toward a longer wavelength when the current decreases.


Management PWM differs from the current two points: First, the contribution of the current decreases with the green, but also to be noted that this decline is centered around 515 Nm.


Moreover, the overlap of the emission spectrum of the LED with the response of the eye


We clearly see that the contribution of green in the sense of color is important (overlap of the emission spectrum from green to the sensitivity of the eye). However,Dell Vostro 1500 Battery DC, the variation of the intensity of the green woodpecker is negligible compared with the top red. At the same time, even if the differences in peak intensity red is a very important contribution to the sense of color is much lower than for the woodpecker.


In summary therefore, the DC mode, the variation of the impact of the flute in the color coordinates, while the variation of the red peak, balanced, even a small contribution due to the sensitivity of the eye, a great influence the color coordinates of the LED. Dell Precision M6500 Battery DC always drive mode when the current decreases when moving to a green light.


This is one reason why Washington green is the color of the coordinates derived from low flows.


For PWM control, the resulting color in the opposite direction of that observed in DC. Therefore, a decrease in power, a shift to the red / orange


Figure 4 shows an overview of the color changes depending on the mode and the current audit.


Conclusions and comments quarter


RGB technology is more sensitive to a change in current consumption race, especially for red wines, which are monitored to be reduced to the role of the current fluctuations.A Dell Inspiron E1505 Battery PWM control is preferred for control (CC) if you want to play in the flow of the LEDs, without many of the color.Check whether the contribution of the red and green technologies in the RGB mode DC may be difficult and expensive.


A final important point is to make clear that these studies were performed in a trap of LEDs. Other Dell Inspiron 1720 Battery LEDs in many cases, could certainly lead to slightly different values​​, show similar trends, however.


 


 

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