ulv481x0p
Dołączył: 23 Lut 2011
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Skąd: England
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 Wysłany: Nie 4:02, 13 Mar 2011 Temat postu: High-power LED thermal solution ceramic |
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The - curve shown in Figure 1.1. Figure 1.1 LED? Curve can be seen from Figure 1 that,[link widoczny dla zalogowanych], when added to the voltage across the LED does not meet 3.4V before, with the increase. When added to the LED when the voltage reaches 3.4V, the change is small, increasing the voltage across the LED will only increase the current flowing through the LED, thus changing the LED brightness, LED increased until the maximum (350MA), LED to achieve maximum brightness. Which has been clamped in (3.4V) or so.
And the LED with temperature and hours of work change, change curve shown in Figure 1.2. Figure 1.2 The relative change of the temperature curve can be seen from Figure 1.2, with the temperature rise will gradually become smaller, on the contrary, when the temperature decreases, will increase. When the LED's temperature rose to 85 degrees, has become a 3.25V (3.4V-0.15V),[link widoczny dla zalogowanych], the opposite when the temperature dropped to -40 degrees LED becomes 3.6V (3.4V +0.2 V).
Therefore,[link widoczny dla zalogowanych], LED dimming, to get transferred to a fixed brightness LED, it is necessary to ensure a fixed, constant current control to be used is to say. There is another way: constant power control. It is also currently on the market generally used ASIC dimming way. But the constant power control has the inherent disadvantage.
2 Constant power control LED dimming 2.1 theoretical basis for constant power control using single-stage FLYBACK general topology, the basic block diagram shown in Figure 2.1. Figure 2.1 Diagram of constant power control can be seen from the diagram of switching power supply FLYBACK general than constant power program more than a dimmer signal control circuit for detecting the input SCR conduction angle and input voltage,[link widoczny dla zalogowanych], thus gives the corresponding dimming signal.
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