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High brightness LED features
Brightness (BRIGHTNESS) is generally meant by the amount of light. The relationship between mcd and CD is 1000mcd=1cd, where cd is the unit of luminous intensity, meaning “candlelight” is also called “international candlelight”, which is defined as: a fully radiated object with a surface area of 1/60cm of surface area, heated to Luminescence intensity at a melting point of platinum (1668 degrees). Compared with the early LED light-emitting diodes, the most remarkable feature of the new ultra-bright LEDs is that the brightness is increased by nearly a hundred times. The early LEDs have a luminous intensity of only a few ten to several tens of mcd, while the new LEDs have a minimum luminous intensity of 1500 mcd. Knowing the relationship between luminance and luminous intensity, the high-luminance LED refers to a high-luminance LED, which has the following characteristics compared with ordinary LEDs:
1, forward voltage - forward current characteristics
The high-intensity white and red LED VF-IF features the same characteristics as a typical diode. When the forward voltage is below 1.7 volts and below 2.8 volts, almost no current flows, but once the above two voltages are exceeded, the current Start to flow, in order to make the LED lighting voltage vary with each product, generally requires a voltage of about 1.7 volts ~ 4 volts.
2, forward current - relative luminosity characteristics
The brightness of the LED during DC drive is up to the design value of the product, and is usually linearly proportional to the current. When driving with a PWM pulse, the brightness of the LED is almost linear with Duty.
If the brightness of IF=20mA is 1, the relative photometric characteristics of IF are generated, then the current brightness of 2 times will not become 2 times. The main reason is to increase the current. The LED itself has self-heating characteristics, causing the temperature of the kit to rise, in other words, Part of the electrical energy is converted into thermal energy. In fact, the current that causes the LED to illuminate is not twice as large as the applied current.
3. Forward current adaptation value
In general, the adaptation forward current of most high-luminance LEDs is set to 20 mA regardless of the illuminating color. Although the specifications of the LEDs are not clearly described, generally the value is set to fully match the LEDs. Efficacy and reliability, that is to say, the items recorded in the specifications are all based on the 20 mA lighting. The same type of LED with the difference of LEDs, VF will be scattered and scattered, but this does not mean that the LED is a defective product or defective.