日期：2012年8月7日

sbc led bulb and led design

When the output voltage may be higher than the input voltage may be lower than the discontinuous buck-boost converter peak current mode control LED driver is a good choice. However, this buck-boost converter used to drive design, the LED voltage change will change the LED current to LED open circuit will produce high output voltage, thereby damaging the converter. This article will discuss in detail this applied to the LED lights converter design, and describe a variety of overcoming the inherent shortcomings of the method.

sbc led bulb and led design

The light-emitting diode (LED street lights) applications have been for many years, with the latest technological advances, is becoming a strong competitor in the lighting market. The new high-brightness LED has a long life (100,000 hours) and high efficiency (about 30 lumens / watt). The past three decades, the LED light output brightness every 18 ~ 24 will double, and this growth momentum will continue, this trend is called Haitz law, which is equivalent LED Moore’s Law.

 

Figure 1a: LED connected in parallel. Figure 1b: LED series connection.
Electrically similar to the LED and diode is a one-way conductive (although the reverse blocking capability is not very good, high reverse voltage is very easy to damage the LED), similar to the conventional diode low dynamic impedance VI characteristics. In addition, LEDs are generally safe conduction of the rated current (rated current of the high brightness LED typically is 350mA or 700mA). Rated current, LED forward voltage drop of the difference may be relatively large, typically 350mA white LED voltage drop between 3 to 4V.

The drive LED controlled DC current. In order to make the long life of the LED, the LED current ripple must be very low, and high ripple current causes the LED to produce large resistive power consumption, reduces the LED life. LED driver circuit is the need for higher efficiency, because the overall efficiency depends not only on the LED drive circuit. Work in the current control mode switching converter is ideal drive options to meet LED applications with high power and high efficiency requirements.

Drive multiple LEDs also need careful consideration. For the following two reasons, is not recommended as shown in Figure 1a as parallel LED strings: dynamic impedance and forward voltage drop of each LED is not the same, if there is no external current circuit (current mirror), impossible to guarantee that flow through the LED the same current; an LED failure will make the LED string is disconnected, resulting in LED current is distributed between the rest of the LED string, which will lead to increased current in the LED string, and may damage the LED.

Therefore, a better approach is the LED in series. The disadvantage is that if one LED fails, the entire LED string will stop working. An easy way to let the rest of the LED string to continue working is a Zener diode (rated voltage greater than the maximum LED voltage) shown in each (or group) LED in parallel, as shown in Figure 1b. In this way, any one LED fails, its current will flow to the rest of the Zener diode LED string can still work.

The basic single-stage switching converter can be divided into three categories: the buck converter, boost converter and buck-boost converter. When the LED string voltage is lower than the input voltage, the buck converter (Figure 2a) is the ideal choice; when the input voltage is always lower than the string output voltage, the boost converter is more appropriate (Figure 2b); when The output voltage may be higher than may be lower than the input voltage (caused by changes in output or input), the buck-boost converter (Figure 2c) is more appropriate. The disadvantage of the boost converter, input voltage transients (allows input voltage increases and exceeds the output voltage) will result in the LED upstream a large current (low dynamic impedance load), thereby damaging the LED. Buck-boost converter can replace the boost converter input voltage transient does not affect the LED current.

Buck-boost converter works

LED driver for low voltage applications, the buck-boost converter is a good choice. A variety of reasons, some of which are listed below: They can be used above and below the voltage of the input voltage to drive the LED grow lights strings (boost and buck); high efficiency (it is easy to reach more than 85%); discontinuous suppress the input voltage changes of work mode (to provide good line voltage regulation); peak current control mode allows the converter to regulate the LED current, without the need for complex compensation (simplified design); very easy to implement linear and PWM LED dimming; switch transistor failure will not damage the LED.
Figure 2a: buck converter. Figure 2b: boost converter. Figure 2c: buck-boost converter.

However, this approach there are still two shortcomings: the peak current controlled and discontinuous current mode buck-boost converter is a constant power converter, so any changes will cause the LED current in the LED string voltage corresponding change ; Another problem is that LED open circuit condition in the circuit to produce damage to the high voltage of the converter; In addition, additional circuitry is required to a constant power converter into a constant current converter, and protection in the case of no-load converter.

Figure 3 for the lifting pressure converter application circuit diagram, the controller has built-in used to set the switching frequency of the oscillator. The beginning of the switching cycle, Q1 turns on. Due to the input voltage VIN added to the inductor, the inductor current (iL (t)) from zero (initial steady state) began to rise.

screw in led bulbs and led tree

As people work, study, leisure and entertainment environment, continuous improvement and beautification of the city, lighting engineering are constantly changed. Electronic fireworks trees as landscaping, lighting project is an important landscape, has been the focus. However, the existing electronic fireworks tree is a low-voltage small light bulb as a light source, and highlights the large power consumption, short life, easily damaged, and the lack of color, serious shortcomings in actual use.

LED is an excellent display, long life, energy-saving, high brightness, a variety of luminous colors, fast response and low driving voltage. Low-voltage small light bulbs replaced with LED lights source device simulation fireworks tree, not only can overcome its shortcomings, but also has power-saving, long working life, high brightness, multi-light-emitting color, fast response, etc., and save a lot of energy also can make the work of electronic fireworks more colorful and fascinating.

screw in led bulbs and led tree

Embedded microprocessor with LED display electronic fireworks tree controller is at the core, supported by appropriate drive circuit composed of. The controller can be under the control of the dedicated control software, the corresponding work.

 

A hardware circuit design

In order to ensure a good system to maintain performance and meet the system expansion requirements, LED flood lights electronic fireworks tree controller hardware circuit design, the modular design of the insert plate. The main control circuit board and the drive circuit board is divided into two flapper, each completed independent of the different functions of the two flapper in accordance with the geometric dimensions is equivalent to the size of the PCB design. An LED electronic fireworks tree controller requires only a main control circuit board and a number of pieces of the drive circuit board (depending on the size of the LED electronic fireworks tree). The main control circuit board to control the various driver circuit board through a custom bus. In practical work, the main control circuit board and the drive circuit board inserted in the “cage” rail between each flapper 26-pin flat cable to bus interconnect, and thus can be easily system expansion and system maintenance becomes simple and fast.

1.1 the main control circuit board design

LED electronic fireworks tree is embedded microprocessor 89C52 (IC5) core data bus only export the data of the data bus and address bus in the drive through the 74HC244 bus driver (IC1, IC2) should be into the interconnection bus in order to increase the anti-jamming capability of the system. Programmable gate array chip GAL16V8 (IC3) as the output of high-end chip address decoder can simplify the decoding circuit but also to ensure the uniqueness of each output chip address decoder. Hardware “watchdog” timer circuit using RC oscillator fluctuations in counter, the CMOS chip CD4060 (IC4) mainly consisting of C1, R1 and VD2 composed of a power-on reset circuit. Change the value of R2 or C3 can fine-tune the working hours of the “watchdog” timer, change the VD3 positive pin to the CD4060 output pin connection location can be multiplied to change the working hours of the “watchdog” timer. Jumper switch K1 is mainly used to simulate the display shells to launch the process of rate setting, the jumper switch K2 is given for the analog display shells at high altitude explosion speed. Bus interconnection can be achieved through a dedicated interface (Z1). LED electronic fireworks tree of the main control circuit board circuit diagram shown in Figure 1.

 

1.2 drive control circuit board design

The circuit of the drive circuit board circuit schematic shown in Figure 2. In order to facilitate system expansion, the drive circuit using slot structure design, each output flapper selection the four TPIC6B273 data latches, power driver and output. TPIC6B273 as the combination of 74LS273 and MC1413 (MC1413 only 7 channels output driver TPIC6B273 for 8-channel output driver), which is produced by the U.S. TI Company set eight data latches, power driver for one of the 8-channel D-type trigger device power output device has eight data latches, the composite data-driven output control. Therefore, the application circuit design of the device is very simple.

Figure 2, by comparison decoding chip 74HC688 (IC2) and a 2-4 decoder chip 74HC393 (IC6) and jumper switch K1 matched to complete the decoding of the variable address, and can select the output driver chip (IC1 IC3, IC4 and IC5), strobe, data latches. As a result of the six variable address decoder, LED electronic fireworks tree controller can be expanded to drive 26 = 64 driver board.

LED working status of the electronic fireworks tree is short-term dynamic work status, and selection of ultra-high brightness LED tubes as a light-emitting element, set its short-term transient operating current of 45mA (3 ~ 4 times the rated static operating current), mixed the average tube with colored LED voltage drop of 2.5 volts, the chip each output (load basis TPIC6B273, performance, and current limit) to drive three parallel (3 × 45 = 135mA <150mA), and (according to TPIC6B273 load voltage limit) 20 series LED (2.5 × 20 = 50V). Thus, every one of TPIC6B273 drive output can theoretically drive the LED is:  2.5 × 20  × 3 = 150. In fact, in order to work reliable derating choose to drive half the number of LED (80). Fireworks tree of each electronic driver board has four driver chips, each chip eight, each electronic fireworks tree driver board to drive the LED is: 80 × 8 × 4 = 2560. Can be the basis for the design of electronic fireworks the size of the tree (using the number of LED’s) to select a different number of drive circuit board.

2 control software design

LED electronic fireworks tree by the trunk (for analog display shells fired off process) and branches (for simulation display shells at high altitude explosion landscape) and two display parts. Electronic fireworks tree work at night, as the branches of the support body, the trunk has been extremely vague on the branches and trunks of different LED display light of the source of the controlled work will simulate the entire work process display shells from launch to explosion .

The main task of the electronic fireworks tree software design is the process of the work of the analog display shells (fired – explosion), especially in high-altitude explosion landscape. The design  first high-altitude landscape named (such as the dream world, earth red, sky full of stars, etc.)  drawing and designing their specific work processes and phenomena according to their landscape, and so to prepare the appropriate display software modules. An electronic fireworks tree 10 to 16 display modules can be designed to increase the display pattern. Enable the viewer to work long hours in order to protect the electronic fireworks tree boring, each work cycle randomly generate a display module order coexist in a linear table, the control procedures in order to check the data in the linear worksheet Decide which one module. Vary due to display the working status of the working module, Figure 3 gives only the main workflow of the electronic fireworks tree.

3 Conclusion

The LED electronic fireworks tree and its controller after prolonged use in the winter, summer and harsh environmental conditions proved that the system is reliable, prominent, obvious advantages.

shop led lighting and new white led

With the color LCD increasingly wide range of applications in handheld devices, the demand for compact and inexpensive white backlight, and more and more widely. Traditional program uses a cold cathode fluorescent lamp (CCFL) and electroluminescent (EL) panels, but these circuits for the current hand-held consumer products to large size, expensive, complex and other institutions of higher. At present, the recent development of LED technology has produced a white light LED. White LED lights and mass
Ship compared to the backlight has many advantages, including small size, low cost, low complexity and high reliability.

Today, a new generation of multi-functional cellular phone has been widely used in the domestic market. A new generation of mobile phones is not only compact size, and integration of more functions, such as PDA functions, to close / e-mail, text messaging services, as well as browse the Internet letter in a large size, rich colors on the monitor. Some mobile phone models
Also includes a frequency modulation (FM) radio. MP3 players, and even higher resolution digital cameras.

Whatever its function, the consumers, and always look forward to providing long-lasting battery life in handheld devices without increasing the size of the case. That is, not only in a small receiver with more features at the same time consume less power. Such a power management design is extremely demanding requirements. In response to the Peach war, manufacturers must address the following topics:

Power Manager IC (PMIC) on the basis of further deepen and broaden the application of trendy white LED technology and devices, to complete a new handheld or mobile phone supporting the best choice. This article presents a white LED trendy technology and devices to be introduced.

2, the white LED lamp is a new technology program

shop led lighting and new white led

2.1 compact non-inductive boost circuit MAX1759-regulation white bias current

Typical of the white LED forward voltage of about 3.5V ± 10%, only for the device to provide a positive bias to white light. Need to step-up circuit when the white light LED forward voltage than the battery voltage, the traditional solution is to use the boost circuit, through the ballast resistor provides bias for the LED, this program there are two defects: First, the white LED more the wide range of forward voltage variations can cause large changes in bias current, the brightness deviation; Secondly, the traditional step-up program have a DC path between input and output (even in the off state), so that does not work LED unnecessary consumption of battery current.

To overcome the above drawbacks, a new non-inductive boost circuit MAXl759 (regulator type buck / boost charge pump) is a compact solution, shown in Figure 1 circuit. The regulator type l / step-down charge pump (uMAX) package of small size, can provide 100mA output current. In accordance with the configuration in Figure 1, can be directly provide a stable bias current of white LED bias multiple parallel LED with good brightness distribution. MAXl759 circuit shutdown there is no DC path between input and output, users can take advantage of the input control backlight pass, breaking. The circuit also with a power-good (POK) output, whether it has been prepared to inform the microprocessor backlight good.

The huge export opportunities of all lighting, participating in the global competition to be innovative

A number of large technology enterprises successfully participated in the “siege” outside to the global LED lights industry chain, and increasingly occupy an important position. International predators have approaching from various quarters of this vast market of mainland China, the economic power of more growth in the Chinese folk from the land of China toward the United States and Europa, looking ahead, from the streets of Florida to skimming over the surface of the metropolis of France, all lighting from the glory of the Russian theater dancing to Tokyo Osaka. Light the spark of “Made in China” on the world map.

all lighting

Faced with the business opportunities also needs to innovate

At present, although the process of world economic recovery is slow, there are still many uncertainties. But overall, exports are still an important part of China LED companies to participate in global competition and market share, and there are tremendous business opportunities.

LED lamps huge export opportunities to participate in the global competition to be innovative Faced with business opportunities, how to quickly create new advantages to participate in global economic cooperation and competition? In the next five to ten years, China’s cost advantage will come to and end… New advantages for China’s participation in global economic cooperation and competition, changes in the mode of competition, we should shift from OEM mode to autonomous mode of technological innovation, market innovation, market innovation, management and organizational innovation model up, to achieve the technical content, value-added ability to shift from low-to high -end.

China LED products are exported mainly in the packaging and application aspects

In recent years, many LED companies, thousands of miles away overseas markets, but more like a fly freely vast. The Pearl River Delta and Yangtze River Delta region of LED manufacturing companies, many companies exports accounted for more than 50% to 70% proportion. Analysis of the industry, rapid export growth of the main reasons. First, the development of the domestic market is relatively speaking, and not mature; Second, A global scale, many countries are stepping up legislation to encourage the use of energy-saving light.  Meanwhile, the LED industry development is not only for all lighting and semiconductor industry which has a strategic leading role, but also lead to a series of end-consumer appliances, automobiles, mobile phones and other technological change, governments around the world to increase support to the LED industry policy.