Generally believed that the excellent performance of the solid LED as a light source, white LED is the most promising. Therefore, many countries have invested heavily in actively high power, high efficiency white LED. There are already commercial lighting level white LED, the price is constantly declining.
1 white LED performance
(1) the characteristics of white LED
White LED lighting-class power for the W, 3 W, 5 W, 0 W, 5 W,
The so-called white LED lighting level is the single package, with a “W” 20 W and other products.
(2) the curve parameters of white LED
Can be seen from the curve: when added to the forward voltage is less than its threshold voltage, the forward current is very small, the brightness is very low. When added to the forward voltage on it exceeds the threshold voltage when, LED starts to conduct and emit light. With further increase the forward voltage, forward current of a sudden rapid increase in the brightness of light is gradually increased, the forward voltage and forward current showed a linear relationship basically, it is necessary to strictly control the forward current size, to prevent the use of the process exceeds its maximum current and seriously shorten its life, and even cause permanent damage.
(3) white LED in the shape of the structure
Common single-level white solar lighting package form factor.Because of its power consumption is higher, when the PN junction temperature to prevent the work
Life through high impact, heat can become safe and effective work of the main issues, while the output of white light to the chip taken out as effectively as possible to improve the luminous efficiency of LED is also a critical issue. High-power white LED is usually by a single or multiple chip package according to parallel or series model substrate in the same heat, showing the hexagonal appearance (Figure 2a). Of course, there are less power (W) is the use of white LED chip form (see Figure 2b), mainly for some special applications, such as digital cameras flash.
2 White LED Application
White solar lighting level to ensure not only be a good application, but also to obtain higher efficiency, the first is the need to meet certain application conditions, followed by the need to adopt suitable LED driver circuit to meet with the requirements of the parameters of work .
(1) application conditions
① drive circuit is a power supply for LED special power supply, to have a simple circuit structure, small footprint and high efficiency volume;
② output driver circuit parameters (current, voltage) with the LED to be driven to match the technical parameters to meet the requirements of LED and high precision constant current control and the right pressure limiting function. Multiple outputs, each road should be able to individually control the output;
③ with linearity better dimming capabilities to meet the different applications of the LED brightness adjustment requirements;
④ In the abnormal state (LED open circuit, short circuit, driver circuit fault), the circuit can be on the circuit itself, LED and users have the appropriate protection;
⑤ drive circuit work, electrical work on other less interference to meet the requirements related to electromagnetic compatibility.
(2) linear drive applications
Linear drive application is one of the most simple and most direct way to drive applications. White LED applications in lighting level, although there is low efficiency and poor regulation, but because of its circuit are simple, compact and can meet the general requirements, so in certain occasions used more often.
① VDD + power supply means limiting resistor R
Circuit has the advantage of simple structure and low cost.Resistor in series with the LED as the additional loss of large, linear power supply VDD and its power consumption is also large, so the two are added together the overall efficiency is low (“50%), plus LED current control accuracy is low, the brightness is not adjustable, it is generally only used in small power and short time according to
Specified occasions, such as LED flashlights, emergency lighting.
② steady power supply with current limiting resistor VDD + R + S mode electronic switch
The advantage is to not only improve the LED current control accuracy, and the LED’s brightness can also change the on-off switch S than to adjust. However, due to series resistance and linear steady flow of additional power losses are high, so the resulting overall efficiency is still low, the specific scope of application subject to greater restrictions.
(3) Switch drive applications
By switching drivers (Figure 4) can get a good current control accuracy and high overall efficiency. Driver application mode switching buck and the boost is divided into two broad categories.
① buck switch drive
Buck switch driver is higher than the LED supply voltage for the voltage or multiple LED driver in case of using parallel applications. The main principle is to use the circuit in accordance with the requirements of the electronic switch S off the resulting current chopper to get to meet the work requirements of LED forward current value, the negative feedback through the current (from the current sampling R0) such that flow through LED forward current stabilized at a certain range, and can be both a dimming function. Figure 4 is to play the role of the inductor L S and S open storage turns off when the continuous current role in order to reduce the flow through the LED forward current fluctuations.
② boost switch driver
Boost switch driver is less than the LED supply voltage for the voltage or the number of LED in series driven by the application of the case. The working principle of the circuit is the use in accordance with the requirements of the electronic switch S off the on-off effect. When the power supply V S to open storage inductor L, S L turns off the voltage polarity reversal on electric and power (DD) voltage V DD to get the overlay work to meet the requirements of LED forward current and forward voltage through the current negative feedback (from R0 to current sampling), so that
May flow through the LED’s forward current stabilized at a certain range, but can be both a range of dimming.
3 Conclusion
Some European countries such as Germany already use solar lighting power, the U.S. has in large quantities. China’s most prestigious research institutions solar photovoltaic system — Ministry of Education, Engineering Research Center of the technology have been listed in the “energy inventory”: the national annual increase of 50 million outdoor lighting, solar lighting can be accounted for ifthousandth year, the state could save nearly 700 million kWh of electricity, equivalent to the state to send a 00,000 kilowatts of power stations. We look forward to this is not the cleanest energy in the
A long time in the future to all households.
Can be used to replace the newly developed high-power solid shining general lighting devices, although subject to the current price, to a certain extent, restricted the application of the speed, but because of its excellent performance, with the development of technology continues to progress, can be predicted white LED lighting-class must have a good prospect. In this paper, its performance characteristics, drive parameters, drive requirements, drive circuit efficiency discussion, white LED lighting-class practical application has some reference value.
1 white LED performance
(1) the characteristics of white LED
White LED lighting-class power for the W, 3 W, 5 W, 0 W, 5 W,
The so-called white LED lighting level is the single package, with a “W” 20 W and other products.
(2) the curve parameters of white LED
Can be seen from the curve: when added to the forward voltage is less than its threshold voltage, the forward current is very small, the brightness is very low. When added to the forward voltage on it exceeds the threshold voltage when, LED starts to conduct and emit light. With further increase the forward voltage, forward current of a sudden rapid increase in the brightness of light is gradually increased, the forward voltage and forward current showed a linear relationship basically, it is necessary to strictly control the forward current size, to prevent the use of the process exceeds its maximum current and seriously shorten its life, and even cause permanent damage.
(3) white LED in the shape of the structure
Common single-level white solar lighting package form factor.Because of its power consumption is higher, when the PN junction temperature to prevent the work
Life through high impact, heat can become safe and effective work of the main issues, while the output of white light to the chip taken out as effectively as possible to improve the luminous efficiency of LED is also a critical issue. High-power white LED is usually by a single or multiple chip package according to parallel or series model substrate in the same heat, showing the hexagonal appearance (Figure 2a). Of course, there are less power (W) is the use of white LED chip form (see Figure 2b), mainly for some special applications, such as digital cameras flash.
2 White LED Application
White solar lighting level to ensure not only be a good application, but also to obtain higher efficiency, the first is the need to meet certain application conditions, followed by the need to adopt suitable LED driver circuit to meet with the requirements of the parameters of work .
(1) application conditions
① drive circuit is a power supply for LED special power supply, to have a simple circuit structure, small footprint and high efficiency volume;
② output driver circuit parameters (current, voltage) with the LED to be driven to match the technical parameters to meet the requirements of LED and high precision constant current control and the right pressure limiting function. Multiple outputs, each road should be able to individually control the output;
③ with linearity better dimming capabilities to meet the different applications of the LED brightness adjustment requirements;
④ In the abnormal state (LED open circuit, short circuit, driver circuit fault), the circuit can be on the circuit itself, LED and users have the appropriate protection;
⑤ drive circuit work, electrical work on other less interference to meet the requirements related to electromagnetic compatibility.
(2) linear drive applications
Linear drive application is one of the most simple and most direct way to drive applications. White LED applications in lighting level, although there is low efficiency and poor regulation, but because of its circuit are simple, compact and can meet the general requirements, so in certain occasions used more often.
① VDD + power supply means limiting resistor R
Circuit has the advantage of simple structure and low cost.Resistor in series with the LED as the additional loss of large, linear power supply VDD and its power consumption is also large, so the two are added together the overall efficiency is low (“50%), plus LED current control accuracy is low, the brightness is not adjustable, it is generally only used in small power and short time according to
Specified occasions, such as LED flashlights, emergency lighting.
② steady power supply with current limiting resistor VDD + R + S mode electronic switch
The advantage is to not only improve the LED current control accuracy, and the LED’s brightness can also change the on-off switch S than to adjust. However, due to series resistance and linear steady flow of additional power losses are high, so the resulting overall efficiency is still low, the specific scope of application subject to greater restrictions.
(3) Switch drive applications
By switching drivers (Figure 4) can get a good current control accuracy and high overall efficiency. Driver application mode switching buck and the boost is divided into two broad categories.
① buck switch drive
Buck switch driver is higher than the LED supply voltage for the voltage or multiple LED driver in case of using parallel applications. The main principle is to use the circuit in accordance with the requirements of the electronic switch S off the resulting current chopper to get to meet the work requirements of LED forward current value, the negative feedback through the current (from the current sampling R0) such that flow through LED forward current stabilized at a certain range, and can be both a dimming function. Figure 4 is to play the role of the inductor L S and S open storage turns off when the continuous current role in order to reduce the flow through the LED forward current fluctuations.
② boost switch driver
Boost switch driver is less than the LED supply voltage for the voltage or the number of LED in series driven by the application of the case. The working principle of the circuit is the use in accordance with the requirements of the electronic switch S off the on-off effect. When the power supply V S to open storage inductor L, S L turns off the voltage polarity reversal on electric and power (DD) voltage V DD to get the overlay work to meet the requirements of LED forward current and forward voltage through the current negative feedback (from R0 to current sampling), so that
May flow through the LED’s forward current stabilized at a certain range, but can be both a range of dimming.
3 Conclusion
Some European countries such as Germany already use solar lighting power, the U.S. has in large quantities. China’s most prestigious research institutions solar photovoltaic system — Ministry of Education, Engineering Research Center of the technology have been listed in the “energy inventory”: the national annual increase of 50 million outdoor lighting, solar lighting can be accounted for ifthousandth year, the state could save nearly 700 million kWh of electricity, equivalent to the state to send a 00,000 kilowatts of power stations. We look forward to this is not the cleanest energy in the
A long time in the future to all households.
Can be used to replace the newly developed high-power solid shining general lighting devices, although subject to the current price, to a certain extent, restricted the application of the speed, but because of its excellent performance, with the development of technology continues to progress, can be predicted white LED lighting-class must have a good prospect. In this paper, its performance characteristics, drive parameters, drive requirements, drive circuit efficiency discussion, white LED lighting-class practical application has some reference value.
