Analyze the wireless power supply technology of LED lighting products


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.

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.

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).

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. The coil L1 is coupled to the receiving coil L2 via 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 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 realizes electric energy by means of electricity, magnetism, magnetism and electricity. The transmission, and 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.


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.

1 Application example

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

(2) Power receiving unit

VOXRl0 is a matching receiver module chip specially designed for the VOX series of contactless power supply transmitter modules, which can provide a relatively stable center voltage for the receiving circuit. VOXRIO has internal reference voltage, limiting, low-voltage starting, output boosting and power output circuits, which fully meet the special requirements of electromagnetic resonance; and its own power consumption is small, the output current is large, the receiving efficiency is up to 80% or more; Voltage limiting circuit, the current is small when the circuit is no-load. The VOXR10 peripheral circuit is simple, and the main components have only one capacitor, one diode and one coil, so it is easy to use.

The power transmitting unit emits an electromagnetic wave, and the internal power receiving unit receives the electromagnetic wave and converts it into an alternating current, and then rectifies and converts the current into a direct current to charge the battery. A power transmitting unit can charge electromagnetic waves emitted by a plurality of internal power receiving units. Lithium batteries are generally used for rechargeable batteries, but lithium batteries have poor stability. Nickel-hydrogen batteries are used in environments with flammable and explosive gases and articles.


(3) LED circuit

An LED is connected in series with a resistor to form a basic unit. Several basic units can be connected in series, parallel, and hybrid mode; multiple LEDs are mounted in an array on a plane to form an LED dot matrix screen. The array has a variety of colors, which are divided into monochrome, two-color, and three-color. The LEDs are evenly distributed on the flexible circuit board in a matrix form, and can be arranged into a combination of indicators or warning icons to display light.

The LED control circuit uses a microprocessor control circuit to control the system with a remote control system, a touch control system, and a tact switch. It is simple to directly control the power supply with a micro button switch. The LED driving circuit can adopt a discrete component driving circuit and an integrated driving circuit.

(4) package

The outer package transparent rubber sleeve is used to protect the circuit of the whole non-contact power supply LED luminous sign board, and the entire non-contact power supply LED luminous sign circuit is firmly enclosed in the outer package transparent rubber sleeve without any interface, so the non-contact described in this paper The power LED illuminated sign has a highly reliable waterproof and anti-leakage performance. The sign can also be made into different shapes according to the needs of the user, and single-sided, double-sided, multi-faceted light display.

1.2 LED miner's lamp

According to relevant statistics, more than one-third of coal mine gas explosion accidents are caused by mine lamp failures, mainly due to defects in incandescent bulbs used in miner's lamps. The LED miner's lamp solves the safety hazard of incandescent bulbs and is widely used in coal mines. LED miner's lamp has greatly improved compared with miner's lamp with energy saving, safety and ease of use, but there are still some problems to be solved.

The mine is wet, watery, turbid, and dusty. The LED miner's lamp uses a nickel-hydrogen battery or a lithium battery as the power source, and the LED light-emitting diode is the light source. Once these components enter the water and enter the dust, they are easily damaged or even scrapped. The locking screw will rust after being wet, it is difficult to remove, and the bolt must be discarded, which wastes material costs and working hours. The charging interface is often ash-clogged, especially when the cement enters the charging interface and is solidified, it is difficult to remove, affecting the charging of the LED miner's lamp, and serious may be scrapped.

The design puts the electric energy receiving end into the LED miner's lamp, and the LED miner's lamp is firmly sealed by the transparent rubber sleeve, and the above problem can be solved by the non-contact power supply technology. The service life, explosion-proof performance and anti-static performance of the LED miner's lamp are improved, the scrap rate of the LED miner's lamp is reduced, the maintenance amount is reduced, and the practicability and safety reliability coefficient are increased.

2 System analysis and composition

For the design of LED lighting equipment using non-contact power supply technology, the design of the system should be considered from three angles: one is to improve the efficiency of the system as much as possible from the selection of the device and the circuit design; the second is to embed the non-contact RFID. (RadioFrequencyIdentification, radio frequency identification) technology, realize ID authentication mechanism to ensure system security; third, use MCU (MicroControlUnit, microcontroller) as the core part, generate the oscillation frequency required by the drive circuit, and also need to control the RFID component and The power receiving end performs information exchange. The power supply end and the power supply end can be powered by one-to-one, one-to-many, many-to-one, many-to-many, and network distribution.

The system consists of a power supply part and a work part (as shown in Figure 4). The power supply part is composed of an MCU and a power supply unit. The MCU detects the load position through the RFID transmitting unit. When the load is present, the power supply unit is turned on to supply power. The working part is composed of an MCU, an RFID component corresponding to the power transmitting end, an LED unit, a power receiving unit and a rechargeable battery. The power receiving unit mainly realizes receiving electric energy, and the power receiving coil receives electric energy, and is rectified and filtered to process the battery and The LED unit is powered. The peripheral circuit of the MCU includes a reset circuit, a reference voltage circuit, a serial port download circuit, a power supply and a ground, a button, an alarm, and the like. The man-machine dialogue interface of the system is realized by the display module. The working part, power supply part, power supply management, buttons, display and other functions are all controlled by the MCU.

The solution for realizing the LED lighting device using the contactless power supply technology is the above-mentioned integration, that is, a two-part configuration, which is a power transmitting end connected to 220V alternating current and a power receiving end for charging the battery of the LED lighting device. The LED lighting device to be charged is placed on the charger, and the charging switch provided at the power terminal is turned on, and the power transmitting end sends the verification information, and the power receiving end sends the confirmation message after receiving the verification information, and after the identity verification is passed, the control driving circuit starts to work. To achieve the transmission of electrical energy.

4 Conclusion

For the design of LED lighting equipment using non-contact power supply technology, firstly, the various indexes expected by the system should be set as the theoretical basis for testing the LED lighting equipment using non-contact power supply technology. Through continuous testing system, analysis of test results, and improvement measures, the system will eventually reach the preset targets. To consider the optical characteristics of LEDs and to make use of the characteristics of LED color diversity, design a reasonable power supply and control circuit, improve the stability of LED lighting equipment, and improve the efficiency of power supply. Control circuits must be developed in terms of centralized control, modularity, and system scalability. Due to the convenience and complete sealing, such LED lighting devices using contactless power supply technology will have a large application space.


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