With the decline in the cost of production of the LED, its use is becoming increasingly widespread applications covered range from handheld devices to the car, and then to architectural lighting. LED high reliability (service life of over 50,000 hours), high efficiency (> 120 lm / W), and near-instantaneous response capability makes it an attractive light source. 200mS response time compared to incandescent bulbs, LED luminous response time in just 5ns. Therefore, they have been in the brake lights of the car industry has been widely adopted.
The drive LED is not without its challenges. Adjustable brightness with a constant current to drive the LED, and how, regardless of the input voltage must be to maintain the current constant. This is just incandescent bulbs connected to a battery power compared to more challenging.led security light
The LED has a positive V-I characteristics similar to diodes. Lower than the LED turn-on threshold (white LED turn-on voltage threshold is about 3.5V), pass through the LED current is very small. Above the threshold value, the current will be the form of a forward voltage exponentially incremented. This allows desk lamp stereotyped as a voltage source with a series resistance, with a warning Description: This model is only valid only in a single work of DC current. If the DC current in the LED is changed, then the resistance of the model should also be immediately changed to reflect the new operating current. Large forward current LED power dissipation causes the device fever, this will change the forward voltage drop and dynamic impedance. It is very important to take full account of the thermal environment in determining LED impedance.
Laser printers and LED printers the light path principle
The imaging principle of a laser printer, and LED printer is substantially the same, are relying carrying the light exposure of the image signal of latent image formed on the photosensitive drum, while the image latent image in the absorption toner transferred to the print paper and the fixing to complete the print job. Their biggest difference is that a different type of light source and the optical system.portable lights
A light source of the laser printer is a high-power laser diode, not under control of the print signal, the laser tube emitting a laser beam according to the printing requirements, the laser beam through the focus lens, a projection on to a high-speed rotation of the multi-prism prism stop rotation, always change the reflection angle of the laser beam, thereby forming a single change in position of the spot beam, this beam after the the shaping change direction through the lens group, is formed on the photosensitive drum in the axial direction of reciprocating scanning laser, the photosensitive The drum exposure, the photosensitive drum is rotated in a single line photosensitive After the laser beam continues to the next row photosensitive photosensitive process to complete the photosensitive drum.
LED printers thousands of tiny LED light-emitting diodes are arranged in a queue, placed axially above on the photosensitive drum, corresponding to a physical resolution of each printer one light emitting diode under the control of the printing signal, the need to print part of the LED tube is lit, they produce light through the focusing head projected directly at the surface of the photosensitive drum, the photosensitive drum exposure, the photosensitive drum is rotated, LED re-lit, so that the next line photosensitive rechargeable fans request, after the completion of the single row photosensitive, thereby completing the photosensitive process.