Two control the brightness of LED

One is to change the current flowing through the led, the general LED tube to allow continuous current 20 mA or so, there is saturation in addition to the red LED, the other LED brightness is essentially proportional to the current flow.
Another method is to use the human visual inertia with a pulse width modulation method to achieve gray scale control, that is, periodic changes in pulse width (ie duty cycle), as long as the repeated cycle of light short enough (ie, refresh frequency is high enough), the human eye can not feel light-emitting pixels in the jitter. As the pulse width modulation is more suitable for digital control, so widely used computer to provide the RGB LED light today, almost all of the LED.
LED control system usually consists of the main control box, scan control board and display device has three major components. Main control box from the computer's graphics card to get a colored screen pixel luminance data, then re-assigned to the scan plate number blocks, each scan LED screen on the control board is responsible for a number of rows (columns), and each row (column) on the LED display control signal is transmitted with a serial manner. There are two serial transmission of display control signals: one is the centralized control panel scan grayscale pixels, scanning from the control panel box of the line pixel brightness value decomposition (ie, pulse width modulation), Then the opening of the line LED signals in pulses (light 1, off 0) by using serial transmission line to the corresponding LED on the control whether light. Devices used in this way less, but the serial transmission of data volume, because in a repeat cycle of light, each pixel in the 16 gray scale requires 16 pulses, required under the 256-level grayscale 256 pulses, the device operating frequency restrictions, can only do 16-level grayscale LED screen.
Another method is to scan the contents of the board is not a serial transmission switching signal for each LED but the brightness of an 8-bit binary value. Each LED has its own pulse width modulator to control the on time. Thus, in a repeating cycle of light, each pixel in the 16 gray scale only four pulses, 256 gray scale only 8 pulses, greatly reducing the frequency of serial transmission. In this method of decentralized control LED gray can be easily controlled with 256 levels of gray.

LED lighting market potential analysis

Today, LED lighting has surely become a mainstream technology. The technology is becoming more mature, one of the symbols is the large number of LED lighting standards and norms have been put forward. Stringent efficiency requirements already exist for quite some time and will continue rising. But Recently, LED lighting designer's work is more difficult, because to meet two requirements: both use dimmers for incandescent dimming control to achieve, but also to achieve high power factor performance for LED brightness adjustment, currently divided into analog dimming and PWM dimming, the following will be LED dimming of the relevant circumstances described. With the LED application market continues rapid growth, the continued expansion of the scope of application has led to the continuous improvement of product requirements, the LED terminal products in the LED brightness adjustment on this feature also appears to be very necessary. Also present, such as LED lamps and displays, etc. must focus on the link.
Dimming lighting systems are very common features. For the incandescent lamp, it can be easily achieved at low cost. LED lights dimming, but there are some difficulties, but for architects and residential users, the transition to LED lighting, dimming may not want to lose control should have advantages. This involves many types of LED lighting knowledge.
Power factor is a very important factor, because of the high power factor can reduce the loss of distribution network. Reduce electricity use on the environment impact of the most effective way to reduce waste, the regulatory agencies around the world are further efforts to strictly regulate their power factor. One example is the solid-state lighting Energy Star energy efficiency standards (09/12/07), which provides residential lighting products, power factor (PF) should be greater than 0.7, the commercial lighting products, power factor (PF) should be greater than 0.9.
LED lamps dimming most common, there are three, three dimming RGB LED light current skills are based on the change of the input dimming. According to different circuit system can be divided into imitation dimming and PWM dimming.
The first: This dimming method is by modulating the LED drive current to complete the LED lights dimming, the brightness of the LED chip and the LED drive current into a certain proportion of stakeholders, so we can adjust the LED drive current control LED lights light and dark.
The second: This dimming method is called pulse width modulation (PWM). The method is to adjust the drive current was through the square wave, the variable pulse width, pulse width modulation through the change of the modulated LED light continuously lit for the time, also change the input power to reach the energy saving, dimming goals. Frequency as usual at about 200Hz ~ 10KHz; because the human eye visual lag, do not feel in the dimming light generated in the process of shining phenomenon. This method has the advantage of dimming LED cooling can improve performance, defect-driven current overshoot the life of the LED chip must have some impact on China's lighting of the town of "Yuyao region rely on the local industrial advantages lighting company, fully leveraging" energy saving "www.jiek025.com characteristics, product design and development played the" Energy "brand, continued application of new energy saving technologies to develop products to meet market demand, according to statistics, the first export of energy-saving lamps, Yuyao April 2230 batch , the value of $ 50,060,000, up respectively 32.5% and 18.4%, ....
Third: This method is called to imitate dimming dimming dimming method or linear method. The kind of dimming method has the advantage: when the drive current linear growth or decreases, reducing the drive current overshoot during the life of the LED chip, and the dimming circuit of strong anti-nuisance. The flaw is the size of the drive current process of change is certainly the color temperature of LED chips have a certain impact.

LED lighting-to-date security standards

Currently on the market a wide range of energy-saving lamps, and more technologically advanced and more environmentally friendly to calculate the energy-saving LED lights. Data display, LED energy-saving 80% energy saving than incandescent lamps, fluorescent energy-saving lamps over 50%. LED lamps are energy saving, environmental protection advantages in lighting industry has become a major trend. The obvious advantage of energy-saving LED lamps can be reflected from the following aspects:
1 low-power, low power consumption: In general, LED display operating voltage is 2 to 3.6V, operating current is 0.02 to 0.03A. That is to say: it does not exceed power consumption of 0.1W;
2 Small: LED energy-saving lamps is basically a small chip is encapsulated in epoxy;
3 long life: the right current and voltage, up to 100,000 hours of their life, almost no maintenance. In addition, LED energy saving lamps are completely epoxy resin, it is more than light bulbs and fluorescent tubes are strong, light body and no loose parts, easy to damage;
4 high-brightness, low-calorie: ordinary incandescent and halogen lighting, although cheap, but the light efficiency is low, due to the thermal effect of light and vain power; LED lamps as lighting lamps, not only high luminous efficiency, and cold produce almost no heat source power;
5 Green: RGB LED light are made by the non-toxic materials, unlike fluorescent lamps containing mercury can cause pollution, but also can be recycled;
6.LED also has energy-saving lamps flicker, applicability, high stability, short response time, etc.;
As LED technology and products used by traditional lamps with different properties have been, so the current safety standards of general lighting is obviously not applicable. In this note about the current safety testing LED lighting requirements (to UL standards, for example).