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Interpretation of how to use high-pressure LED to improve the efficiency of LED bulbs
Use LED as light bulbs to replace the threaded screw-in incandescent bulbs has many advantages. In general, we will trumpet (5-9) of the LED in series, using a power supply to line voltage into low voltage (typically a few tens of volts), when the current is about 350 to 700mA. In determining how best to allow users with the line voltage isolation, we need careful consideration, on balance. We can achieve power in isolation, can also be installed in the LED process in such isolation. In some low-power design, LED physical isolation is a common approach, because it allows the use of lower cost non-isolated power supply.
Figure 1 shows a typical LED light alternative. The example of the power supply non-isolated power supply, the means to achieve user isolation voltage protection is embedded in the package rather than the power supply. Obviously, the power of the space is extremely small, and thus pose a challenge to the package. In addition, the power to be buried inside the package, thus preventing the heat, affecting the efficiency.
Figure 2 shows a 120-volt AC power through the LED-powered, non-isolated circuit. It contains a power for the buck power stage rectifier bridge. The buck regulator is an "upside-down version", the power switch Q2 in the circuit, while the circulation diode D3 is connected to power. The power switch conduction period, through a source resistance of the current regulation. Despite this very high efficiency (80% -90%), but there are several limitations of this circuit efficiency shortcomings. Turn the power switch must carry the full output current, while the power switch is off, the output current flows through the circulation diode. In addition, the current sense resistor R8 and R10 of the voltage of about 1 volt. 15 to 30 volts compared to the LED voltage drop across all three are great, and power efficiency will be a constraint. More importantly, these losses will promote bulb temperature. Ability of the LED light will gradually decrease, and this ability with the LED operating temperature are closely related. For example, 70oC conditions, LED light output by 30% of the time exceeded 50,000 hours, and in 80oC conditions, this time only 30,000 hours. As the bulbs are installed in some of the "tube" in which "tube" tend to impede the heat is not conducive to convection cooling, the heat problem is further complicated.
LED manufacturer LED series by the number of teams in a common substrate, to create a higher voltage of the light. The high pressure also brought light or have a lower cost or higher power supply efficiency. Using these high-pressure products, we only need to use a rectifier and a ballast resistor, in order to achieve more cost-effective power method. Although this power can produce very good power factor, but is inefficient because a large part of the input voltage are used in a steady flow resistor, resulting in 30% -50% of the LED power loss. However, it can be used for small volume, low-power applications. However, in some high-power applications, the low efficiency allowed to no avail. Figure 3 shows another alternative: the use of a boost power supply. Most of the circuit the same way as above. However, the switch, diode, and current detection loss is much smaller, bring up to 90% to 95% efficiency. In addition, the circuit also has a good power factor of 97%.
Figure 4 is described in Figure 1-2 Schematic diagram of the power of pictures. Even if the power output generated roughly the same, but there are some significant differences in size affect the power supply. Power boost inductor size was smaller, because of its lower storage requirements. Compared to the step-up power supply, power supply with a larger step-down resistor. The simulation of the load resistor as a resistor (Figure 2 R20), used to determine when to turn dimmer silicon controlled rectifier (SCR). Need to do this because of the dimmer switch in the Triac next to a component of electromagnetic interference (EMI) suppression capacitor, in the case of no-load power supply voltage is relatively higher. This will disrupt the power supply, leading to instability dimming. Shique not necessary to use the power boost, because the LED through the boost inductor connected to the input, to provide sufficient load, so the problem will not be a problem. Not shown in the back of the board, but as shown in the diagram, there are more low step-down power supply circuit. Therefore, the step-up power with lower power consumption, this LED bulb replacement, such as limited space applications is extremely important.
In short, because of its low power consumption, high-voltage LED, a small temperature rise characteristics, can help increase the spin-LED lamp life. It is through the use of alternative buck-boost power supply, thereby enhancing the power efficiency to achieve. Boost the power loss is about half the buck regulator. In addition, fewer components boost power, power factor better, smaller, and the use of a triac dimmer switch assembly is easier to achieve.
efficiency of 95% retail price of $ 5 LED bulb is no longer a dream
On the market today you can see the LED bulb is basically the maximum efficiency of only 90%, regardless of whether they use which is a leading international supplier of LED driver solutions or distributor of the program. If you tell people the only LED bulb can achieve 95% efficiency, basically all the people will ask you one: you say is part of the DC-DC conversion efficiency?
However, the efficiency of 95% of the LED bulb is really there in the industry, and the use of the program LED drivers from a local supplier, which is a long Express Shenzhen Optoelectronic Technology Co., Ltd., the company uses to its original Power architecture technology industry to achieve this miracle.
More to the point, long-pass optical transport technology Co., Ltd. Technical Director Wen Qiang Mao said: "The technology used to achieve 7W LED bulb, not only BOM cost is very easy to do within $ 5, and the power factor can be more than 90%. "
So long Express to power of the proposed architecture is how to do this it? Mao-Qiang Man, we remove the core concept of drive power required for traditional LED lighting transformer. Our approach is first developed in cooperation with the three optical standards of 12V or 24V high-voltage LED, then the LED constant-current protection circuit and LED chips packaged together with a few in order to minimize the LED bulb BOM cost. In fact, the architecture and Seoul Semiconductor s AC LED is almost, but we have not AC-DC rectifier is also integrated into the long-Express dedicated LED bulb module. Epistar the concept of high-voltage LED concept is almost with us, all with multiple high-voltage LED combination to effectively reduce the output and AC input voltage difference, so that we no longer need to use inefficient, high cost, larger and larger heat transformer.
Today the traditional LED bulb energy conversion efficiency mainly by the following two parts determine the efficiency of the product, that is: AC-DC conversion efficiency, and some parts of the DC-DC constant current efficiency. Although these two parts can separate the energy conversion efficiency of more than 90%, but the efficiency of the two parts together is difficult to over 90%. Power of architecture to effectively eliminate the AC-DC conversion part of the circuit, so the efficiency can be increased dramatically.
In terms of cost, the industry knows that the cost of LED light source is LED bulb costs a major factor in the high, so the industry has been in recent years through a variety of ways to reduce the cost of LED light source, such as the rising brightness LED light source, the use of flip technology development High power LED light source, the use of high technology development pressure LED, and the use of other alternative sapphire substrate technologies (such as silicon carbide, silicon, metal) to develop high-power LED.
The reason why many people in recent years, the industry invested a lot of manpower and resources to develop other substrate technologies LED die, because these substrate technologies can help improve the thermal performance of LED or LED brightness. For example, the silicon substrate thermal performance much better than sapphire, sapphire and silicon cost would be much lower than it attracted, including TSMC and Jiangxi Union Optical Company is committed to developing such a silicon-based LED die substrate, however, the text Mao Qiang said: "Based on the silicon substrate of the LED die is not enough technical maturity, while the sapphire industry because a lot of investment in previous years led to significant cost reductions, so the current silicon-based LED die substrate, the sales price actually Sapphire LED die with the first price of the same. "current long cooperation Fangsan An Optical Express sapphire substrate mainly developed LED die.
American Express has long developed two applications for LED light source optimized CYT300XX series of high-performance, high power factor, to the switching power supply of LED drivers, CYT300XX series of green power factor correction with a constant-current drivers allow the abolition of the traditional LED Bulbs application of the necessary input to output of electrolytic filter capacitor and high-frequency transformer, which greatly improves overall system life, and customers do not take into account when designing the conduction and radiation (EMI), the overall structure of the external system is very simple, which makes any LED Bulb Application developers can quickly introduce new products.
Wen Qiang Mao said: "After three years and a lot of testing and certification, we have now officially released CYT72xx series with the LED bulb module, customers can choose with no electrolytic capacitor dimming LED bulb program, also choose non-electrolytic capacitor dimming LED bulb program now, we can provide customers with maximum power of 7W LED bulb module components, and the price is very competitive. "
LED bulb sales in the rising current state, this one recently from the LED lighting market quickly. Mao-Qiang Wen said: "If a manufacturer of LED lighting in the next two years the market has not done it, it basically was eliminated, so in 2010 a lot of CFL energy saving lamp manufacturers are still waiting to see LED lighting market, but in 2011, almost all of the energy-saving lamp manufacturers rushed into the LED lighting market, because at this time do not enter this market, estimated at 2 years after they are essentially no foot to stand up. "