Compared with the traditional lighting method, LED lighting has many unique places, mainly in the following: from the structural point of view, the traditional lighting source and the luminaire are separated, and the LED lighting can realize the integration of light distribution, heat dissipation and lamps in the structure. Functional design; from a functional point of view, only a small part of the traditional lighting can achieve dimming, and LED lighting can not only achieve brightness adjustment, but also achieve color and color temperature adjustment. In addition, LED lighting is more suitable for intelligent and digital control than traditional lighting methods, forming a complex lighting system.
Based on these characteristics of LED lighting, three models can be given, which are for the general illumination of LED, the intelligent control of LED lighting, the combination of LED lighting and solar wind energy, and illustrate some applications of electronic information technology in LED lighting.
Model 1: Power + Light Source
The working essence of modern electric light sources is to convert electrical energy into light energy, accompanied by a certain heat dissipation. Therefore, the LED general illumination model includes only the power supply and the light source. Under this model, only the switch control of the illumination can be realized, and the functions of dimming, communication, feedback, etc. of the illumination cannot be realized.
The power supply specifically refers to an AC-DC constant current type switching power supply. AC-DC refers to AC to DC conversion because the LED is actually a semiconductor diode that operates at DC voltage. Another characteristic of LED is that its working current approximation is an exponential function of the working voltage. A small fluctuation of voltage will cause a huge change of current. In severe cases, it will directly burn the LED. Therefore, to ensure the safe operation of the LED, the operating current must be constant. . Usually, the power supply of household appliances is constant voltage, and the characteristics of LEDs determine that it uses a constant current power supply. In order to improve the reliability of LED operation, we generally use an isolated switching power supply to achieve effective isolation between the LED and the utility grid. Corresponding to the switching power supply, there is also a type of linear power supply, which is rarely used now, because the switching power supply is more advantageous in terms of efficiency and volume. The current switching power supply technology can achieve a conversion efficiency of 85% or higher, a power factor of 0.95 or more, and a total harmonic of less than 15%. These indicators are also the basic requirements for our choice of switching power supplies.
The light source is the LED chip , which is the core component of LED lighting. In addition to electrical parameters such as operating current, tube pressure drop, etc., we are more concerned about its optical indicators, such as luminous flux, light efficiency, color temperature, color rendering index, light decay and so on. The optical performance of LEDs is closely related to their temperature. The increase in temperature causes problems such as reduced light efficiency, color temperature drift, and reduced lifetime. Therefore, heat dissipation technology is especially important in LED lighting. Thermodynamics tells us that there are only three ways to dissipate heat from objects: conduction, convection, and radiation. Since the LED chip is only fixed to emit visible light of a certain wavelength, there is no infrared radiation to dissipate heat. In the LED, it is mainly conduction heat dissipation, accompanied by a certain convection heat dissipation. Reducing the thermal conduction of LEDs and reducing the thermal resistance of each link, if necessary, using forced air cooling, are all considerations in thermal design.
Model 2: Power + Control + Light Source
Model 2 has one more control module than the model, which greatly enriches the function of LED lighting. If the model is a lighting product, then model 2 can be said to be a lighting system. Since the control module is added, the power supply becomes a constant-voltage switching power supply, but the operation of the LED light source still requires a constant current power supply. This part (constant current drive) is implemented together in the control module. Below, we focus on the control system of LED lighting.
The LED lighting control system can be large or small and has rich functions. Such as: wireless remote control dimming system, color temperature adjustable lighting system, RGB dimming color system, analog daylighting system, intelligent lighting system with DALI protocol, wireless street light control system based on ZigBee and GPRS. Through the phenomenon to see the essence, all these lighting control systems are built using embedded technology, communication technology, sensor technology, computer technology and power electronics technology in the field of electronic technology. It seems complicated and complicated. In fact, there are evidence to follow.
In order to clarify the context, we can divide the LED lighting control system into 8 levels, which are explained layer by layer. If we can do a good job at each level of technical solutions, then any complex control system can be easily implemented like "building blocks."
The eight levels of the LED lighting control system are: the power supply layer, the driving layer, the optical layer, the sensor layer, the negotiation layer, the letter layer, the layer, and the layer of implementation.
Power supply layer
The power supply layer provides an efficient and stable DC power supply for the entire control system. Different from the constant current power supply required for the operation of the LED light source, the constant voltage power supply is required for the operation of the control system. There are two ways to obtain the power supply of the power supply layer: one is obtained from the constant voltage power supply on the LED lighting fixture. This is a DC-DC (DC to DC) conversion because the voltage of the constant voltage power supply on the luminaire is usually very high. The voltage of the control system is very low, so a step-down conversion from DC to DC is required. Second, it is obtained from AC mains. This is an AC-DC (AC to DC) conversion. For safety, it is usually also made. Isolated switching power supply, because the power consumption of the control system is usually very low, so the constant voltage power supply here does not require high conversion efficiency.
Drive layer
As mentioned above, the power supply part of Model 2 is a constant voltage source, and the operation of the LED light source requires a constant current source. Therefore, there must be a constant current drive module in the control system to provide a constant current source for the normal operation of the LED light source. In the design of the constant current drive, a dedicated driver chip is generally used, and a certain peripheral circuit is matched.
The output of the driver chip usually has a string of LEDs, and the constant current output is the operating current of the LED. The higher the voltage range of the output, the greater the number of LEDs that can be carried. There are also exceptions where multiple LEDs are connected in parallel at the output. In this case, we need to connect a small resistor in series with each string of LEDs to achieve current shunting. The driver chip also typically has a PWM (Pulse Width Modulation) port for dimming control, which is the basis for intelligent lighting. The advantages and disadvantages of the constant current drive scheme are directly related to the reliability and service life of LED lighting. Therefore, research on LED drive technology is particularly important.
Dimming layer
LED lighting is easy to implement intelligent control because it is easy to implement dimming control. The realization of all intelligent functions is realized by the dimming function. The understanding of LED lighting dimming is not limited to adjusting the brightness of the light, but also includes adjusting the color temperature and color of the LED. This is also a major factor in the ability of LED lighting to subvert traditional lighting. The implementation of dimming technology is available in both analog and digital. Among them, digital dimming is mainly realized by PWM (Pulse Width Modulation) technology, which is the main means of LED dimming scheme. The PWM signal can be realized by programming the microcontroller to generate different duty cycles to achieve dimming of the LED illumination. Designing an integrated solution for LED "three-tone" (brightness, color temperature, color) is the focus of research at this level.
Sensor layer
The driver layer and dimming layer mentioned above are analyzed from the perspective of system output. Obviously, the sensor layer is the input to the intelligent system. It is like the eyes and ears of an intelligent system. It can sense changes in the external environment and translate these changes into electrical signals that are passed to the brain of the intelligent system, the central processor, for analysis and processing. In the field of lighting control, the sensors we care about mainly include: photosensitive sensors, which collect brightness information of natural light; human sensors, detect the presence of people near the lamps; temperature sensors, collect temperature information of the external environment; and currents when the system is working. Acquisition and analysis of voltage and other data.
Protocol layer
No rules, no standards. In order to achieve orderly coordination between the various modules within the intelligent lighting system, there must be a comprehensive set of "regulations" to convey instructions and perform operations. This system is the agreement of intelligent systems. In the current lighting industry, there are two mature protocols, one is the DALI (DigitalAddressablELightingInterface Digital Addressable Lighting Interface) protocol in lighting communication, and the other is the DMX512 protocol for RGB color control. Unfortunately, neither of these protocols is tailor-made for LED lighting. Research on LED lighting control related protocols is now also a hot spot, and there is no uniform standard in the world. This may be an opportunity for us!
Communication layer
In the field of electronic information, the transmission of protocols is implemented by using communication technology as a carrier. There are three main ways of communication in LED lighting: bus mode, power line carrier mode and radio frequency mode. The bus mode, with its mature technology, high reliability, simple networking and moderate cost, is the most widely used communication means, such as RS485 bus. The power line carrier mode is to transmit the protocol through the AC grid, eliminating the cost of repetitive wiring. It should be said to be an excellent means of communication. However, it has high requirements on the quality of the power grid. Given the serious harmonic pollution of China's power grid, whether this method is suitable for China's national conditions remains to be verified. Radio frequency, the hottest technology is ZigBee. It is an emerging short-range, low-rate, low-power wireless network technology.
Operation layer
This level implements the information interaction between the user and the system. For the design of human-computer interaction software, simple operation, friendly interface, easy maintenance and upgrade should be the primary consideration. Depending on the application, interactive software can be divided into two categories: one running on an embedded system and the other running on a PC.
System implementation layer
At this level, we are doing a global analysis and design of the control system, using the previous seven levels of research results to complete the construction of the entire system. In other words, the design of this level is based on the previous seven levels, which is a synthesis of the results of the first seven levels.
Shareconn development Co.,Ltd assemble series flat cables, we can accept small volume standard flat Cable Assemblies and customized Ribbon Cable Assemblies.
Our factory is qualified with ISO9001:2008, ISO13485:2003 and TS16949:2009 certificates, equipped with high-end automatic production equipment, like automatic crimping machines, automatic wire cutting and crimping machines, automatic crimping and tinned plate machines, etc. Meanwhile, we have our own laboratory to support the testing requirements from our suppliers and 100% checking before shipment. To assure the product and the comprehensive competence, we introduce high-level technical talents and management personnel as well as well-trained staff, and improve ourselves in many ways, like the quality, price, delivery, service, etc. Now, Shareconn has been the best supplier and partner for many customers.
Rainbow Flat Cable,Wire Rainbow Cable,Insulated Rainbow Flat Cable,Electronic Flat Ribbon Cable
Shareconn Development , http://www.share-conn.com