Basic terms of LEDs VF, IV, WL, IR interpretation and luminous flux conversion relationship
V represents the voltage.
F stands for positive.
I represents current.
R stands for reverse.
WL stands for wavelength.
Therefore: VF stands for forward voltage. Generally, the vf of red, yellow, orange and yellow green is 1.8-2.4v, and the vf of pure green, blue and white is 3.0-3.6v. IF is the forward current, and the IF of the small power LED is 20mA. IR is the reverse current,
Generally measured under the reverse voltage of 5v, the fraction is less than 10uA (microamperes), less than 5uA and 0uA several grades. WL is the wavelength of light. The visible light has its own wavelength. Different wavelengths correspond to different colors. For example, red light is generally 615-650 nm (nanometer), and blue light is generally 450-475 nm. White light is modulated by blue chip + phosphor, so there is no wavelength, measured by color temperature (yellow below 3000k, 3000k-7000k white, 7000k or more blue).
What does the Vf value of the LED mean? How does its size affect the LED?
Vf is the meaning of the forward voltage, but the larger the forward voltage, the larger the forward current. You see that as long as it is a small power led acknowledgment book will have a vf value, there is an If value, no matter how large the vf value, (red, yellow, yellow green, orange is generally 1.8v-2.4v, white, blue, green Generally 3.0v-3.6v). If both are 20mA. The two are complementary. For example, 2 white light, one is 3.0v, 20mA, one is 3.4v, 20mA, which means the first light, you give it 3.0v voltage, the current flowing through it is the normal rated current 20mA, but the first For two lights, you have to give it a voltage of 3.4v, and the current flowing through it is 20mA. Here Vf and If are not directly proportional; but a yellow light and a white light, such as the yellow light voltage is 2.0v, the white light voltage is 3.3v, this yellow light is at 2.0v voltage and this The white light flows through them at the voltage of 3.3v. The current is the same, both 20mA, where Vf and If are not proportional. Therefore, Vf and If are absolutely proportional to the case of the same lamp. When you use it, no matter how big the Vf is, just control the current flowing through all the lamps to 20mA.
LED basic terminology
Luminous flux (lm): The sum of the amount of visible light emitted by the source per second. For example, a 100 watt (w) bulb can produce 1500 lm, and a 40 watt (w) fluorescent lamp can produce 3500 lm of luminous flux. â—‡ Luminous intensity (cd): The luminous flux emitted by a light source in a unit solid angle, that is, the density of the luminous flux emitted by a light source in a spatially selected direction. The unit of light intensity is Cantra (cd), also known as candlelight. For example, 1 lumen of light emitted in a unit of three-dimensional angle is called 1 Cantera (1 cd). â—‡ Brightness: LED is a kind of illuminating device. Brightness refers to the illuminance per unit area. The unit is: candle/square meter, and the standard driving current of LED is 20mA.
Color temperature (k): expressed in absolute temperature (k=°C+273.15)K, that is, a black body is heated, and when the temperature rises to a certain extent, the color gradually becomes dark red-light red-orange-yellow-yellow-white-white-blue-white - Blue changes. When the color of a light source is the same as that of a black body, we refer to the absolute temperature of the black body at that time as the color temperature of the light source. For example, when the black body is heated to a deep red, the temperature is about 550 ° C, that is, the color temperature is 823 K.
Light efficiency (lm/w): The luminous flux emitted by the source divided by the power consumed by the source. It is an important indicator of energy saving in light sources.
Color rendering (ra): The degree to which a light source appears to the color of an object itself is called color rendering. That is the degree of realism of the color. The International Commission on Illumination CIE sets the sun's color rendering index to 100. The color rendering indices of various types of light sources vary. Such as: incandescent lamp ra ≥ 90, fluorescent lamp ra = 60 ∽ 90.
Viewing angle: Angle is divided into X axis (left and right) Y axis (upper and lower). When the center axis is 1 brightness, the left and right or up and down axis brightness is 1/2, the angle is the viewing angle; for example, 70 ° can be used. The viewing angle refers to 35 ° from the center point up and down or left and right.
Wavelength: the wavelength of the light emitted by the diode, generally red wavelength is 620-660nm, pure green 520-530nm, blue 470-480nm, yellow 580-890nm, yellow green 550-570nm, please refer to the chromaticity diagram, different The wavelength of the emitted light is different; the mixing of the two colors is different.
Quaternary system : A light-emitting diode made of four chemical elements of ALInGaP, which emits light between yellow-green/yellow/orange/red (wavelength 550-630nm), with high brightness and low attenuation. At present, the mainstream products of outdoor light-emitting diodes.
Pure green/yellow green: The traditional green LED is mainly yellow-green, with wavelengths from 550-570nm, low price, low brightness and fast decay. In 1994, Japan's Asian manufacturing company produced pure green (wavelength 520-530nm) price. High, high brightness, slow decay, widely used on outdoor displays, these two products have great differences, and must be clearly distinguished when designing.
Monochrome/double primary color/full color screen: The three primary colors are red/green/blue; if one of the three LEDs is included in one pixel tube, it is called full color display; if only red + green is called double primary color screen, If there is only one color such as red or yellow, it is called monochrome display, the monochrome display is mainly for playing pure text content, the double primary color is mainly for text + pattern + animation, and the full color screen is mainly for broadcasting video signals. .
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