1 Introduction
Semiconductor lighting, also known as solid-state lighting, refers to the use of solid-state lighting devices as a light source, including LED (Light Emitting Diode) and OLED (Organic Light Emitting Diode, organic light-emitting diode), with small size, low power consumption, long life and high Brightness, environmental protection, durability, and controllability are ideal light sources for a wide range of applications. Semiconductor lighting is another revolution in lighting sources after incandescent and fluorescent lamps. Semiconductor lighting technology is developing rapidly, with a wide range of applications, strong industrial driving, and great potential for energy saving. It is recognized by all countries as the most promising high-efficiency lighting industry.
On September 22, 2009, the National Development and Reform Commission and other six ministries and commissions announced the "Opinions on the Development of Semiconductor Lighting Energy-Saving Industry" and clarified the "six-year plan" for the development of semiconductor lighting energy-saving industry. With the acceleration of the industrial restructuring and the transformation of the development mode, the semiconductor lighting energy-saving industry has ushered in a new period of development opportunities as an important measure for energy conservation and emission reduction. Due to the continuous advancement of technology, large-scale application of LED in the field of lighting is about to start. Investment institutions at home and abroad have turned their attention to the LED field, and the LED industry has become a hot spot for investment.
The LED lighting industry is still in its infancy, and various LED lighting technologies are still being further improved. China's LED industry needs to grasp the pulse of the market, actively expand the consumer market, and form a virtuous cycle of promoting technological innovation through market applications and driving market demand with technological innovation. Give full play to the advantages of LED, develop LED lighting equipment with special purpose, and actively expand the application range of LED lighting equipment.
2 contactless power supply technology
The feature of the contactless power supply technology is that the power supply terminal and the power supply terminal can transmit power to the power terminal without any physical connection. Short-range contactless power supply systems using electromagnetic waves in the millimeter to centimeter range have been applied. Mobile devices such as electric vehicles, deep water operations, robots, mining machinery, electric toothbrushes, mobile phones and notebooks, and even electronic medical devices implanted in the human body are also powered and charged by this technology. Therefore, short-range contactless power supply technology has broad application prospects.
Based on the principle of electromagnetic induction, the non-contact power supply technology comprehensively utilizes power electronics technology, magnetic field coupling technology, high-power high-frequency conversion technology, and realizes the isolation of transmission power system and power equipment by means of modern control theory and method. There is no direct contact between electricity, which satisfies the needs of special applications and improves the safety and reliability of power transmission. Therefore, the contactless power supply technology is a safe, reliable and flexible new technology for power access.
2.1 Basic principles
The contactless power supply system includes two parts: a power transmitting unit and a power receiving unit. The power transmitting unit is mainly composed of an AC/DC power supply circuit, a power amplification output circuit, a driving circuit, an oscillating circuit, a reference voltage circuit, a control protection circuit, and a transmitting coil L1 (transformer primary); the power receiving unit mainly includes a receiving coil L2 (transformer secondary) ), high frequency rectification filter circuit and load composition (as shown in Figure 1).
Figure 1 Structure diagram of contactless power supply system
When the contactless power supply system is working, the input terminal converts the AC mains power into a DC power through a full-bridge rectifier circuit, or directly supplies power to the system through a DC power terminal. The DC power is converted into a high-frequency AC power through an oscillation circuit and amplified by a power amplification output circuit. Coil L1. The electric energy is coupled to the receiving coil L2 through the transmitting coil L1, and the current output from the receiving coil L2 is converted into direct current by the high-frequency rectifying and filtering circuit to be supplied to the load.
2.2 Features and defects
Based on the non-contact power supply technology of electromagnetic induction principle, the transmitting coil and the receiving coil must have electromagnetic resonance with the same resonant frequency to transmit electric energy, and have the following main characteristics and defects: electromagnetic resonance is performed by means of "electricity, magnetic, magnetic and electric". Realizing the transmission of electric energy, and it is an open system, there must be the loss of electromagnetic radiation and energy. Therefore, the actual efficiency at close range is hard to exceed 80%, and the efficiency may be low in the long distance. Therefore, it does not meet the concept of energy saving.
The relationship between electromagnetic energy and distance is that the electric field strength is inversely proportional to the square of the distance, and the magnetic field strength is inversely proportional to the fourth power of the distance. Simple electromagnetic resonance is impossible to transmit over long distances. Usually at 1 meter, the efficiency does not exceed 1%. Therefore, it can only be used at close range, generally no more than 10 cm.
Electromagnetic resonance can penetrate non-metals but not metal. With this feature, it is possible to manufacture an instant charging or instant power supply with outstanding performance in terms of mobility, water resistance and isolation. This feature can also be applied to solve its own electromagnetic interference problem. Selecting an appropriate power supply frequency to make the system resonate, the electromagnetic wave frequency band of the power transmitting end has no interference or interference to normal communication and broadcasting, and does not cause harm to the human body or other organisms, and meets safety indicators.
In close-range electromagnetic resonance within a few centimeters, there is still a problem of high-voltage vibration: the voltage of the receiving circuit at load is very different from the voltage at no-load, often several times or even ten times, causing the receiving circuit At no load, the load circuit burns out due to a large increase in voltage. It is an important factor that is difficult to use in the current non-contact power supply technology of electromagnetic resonance.
3 Application of contactless power supply technology in LED lighting equipment
Existing LED lighting signs, LED lighting products, etc., usually use wired power supply and charging. Therefore, it is necessary to supply and charge by means of an interface and a wire in a wired manner, and it is necessary to install an interface and a wire on the illuminated signboard and the lighting device, resulting in overall waterproofing, anti-leakage performance and unreliability of the device. It cannot be used, installed, or stored in harsh environments for long periods of time, such as in water, in mines, or in continuously humid environments.
This paper explores the feasibility of non-contact power supply technology applied to LED lighting equipment, and puts the power receiving end of the contactless power supply system into the LED lighting equipment. Choose the appropriate LED driver technology to design LED luminaires that can be contactlessly powered or charged. The LED illuminating device has the characteristics of mobility, high water repellency and high isolation, and is suitable for safety signs and lighting in special places such as underwater operations, mine operations, flood fighting and disaster relief.
3.1 Application examples
3.1.1 LED illuminated signs
The non-contact power supply LED luminous signboard (shown in Figure 2) designed by this paper consists of internal non-contact power supply receiving unit, rechargeable battery, LED, LED drive circuit, system control circuit, flexible circuit board, and outer package transparent rubber sleeve. constitute. The external part is composed of a contactless power supply unit and a power source.
(1) Power transmission unit
Developed and produced by Domestic Tomorrow Technology Co., Ltd., VOX330MP05S and VOXRIOD are non-contact power supply chipsets at close range, which solves the problem of high voltage and high voltage that cannot be solved for a long time, so that the output voltage is basically maintained within a relatively stable voltage range.
VOX330MP05S is a high-power transmitting module chip for non-contact power supply of mains power supply. It can supply power directly to the chip after rectification of the mains. The working voltage range is large, the lowest can be as low as IOOV, the highest voltage is up to 400V, with up to 1A. Current carrying capability, typical operating circuit (shown in Figure 3). Ic internally has circuits such as oscillation, reference voltage, pulse width modulation, limiting, low voltage start, output boost and power output, which fully meet the special requirements of electromagnetic resonance; V0x330MP05s has low power consumption, large output current and high transmission efficiency of 70%. Above; the chip has an automatic current limiting circuit, the current is small when the circuit is no-load, and the output capacity under large load can be more than ten times that of no-load; the peripheral circuit of VOX330MP05S is simple, the main component has only one resistor and one capacitor. And ~ coil, so easy to use. Non-contact power supply can be realized by using the corresponding receiving module at the same time.
Figure 3 Power transmission unit