LED driver development review
[Source "High-tech LED - Technology and Applications" March issue Jiang Delai / Yao Xiaoli]
Foreword
As the energy crisis and climate warming become more and more serious, energy conservation has become a topic of global concern. Lighting is an important aspect of human energy consumption, accounting for about 20% of the world's total energy consumption. Therefore, research on green energy-saving lighting has received more and more attention. Light Emitting Diode (LED) is a semiconductor light-emitting device that converts electrical energy into light energy. As a new high-efficiency solid-state light source, LEDs have miniaturization, low power consumption, long life, environmental protection, and color. Rich, fast response, high efficiency and energy saving. At the same brightness, the power consumption is only one tenth of that of ordinary incandescent lamps. LED lighting has become the focus of attention in the field of lighting. The incalculable potential of the LED lighting market is bound to ignite the huge demand for energy efficient LED drivers.
Development of LED drive technology
LEDs are used in a combination of connections, serial, parallel, and series-parallel combinations. The series mode can achieve natural current sharing, but the reliability is low. One of the LEDs fails to open, and the whole lamp will fail. At the same time, for high-power applications, the driving voltage will be high and cannot meet the SELV voltage requirements, which will increase the insulation requirements of the lamps and increase the system cost. Parallel use reduces the drive voltage and meets the SELV voltage requirements, but requires current sharing, and the total output current is high and the drive conversion efficiency is low. Therefore, in practical applications, for small power, there are many in series. For medium and large power, choose the combination of series and parallel to achieve a balance between conversion efficiency and reliability.
The following focuses on multi-channel constant current drive techniques for serial-to-serial combination. The multi-channel constant current driving technology has experienced the scheme of constant voltage driver plus multiple constant current driver, multi-channel constant current driver and adaptive driver.
1). Single AC/DC constant voltage driver plus multi-channel DC/DC constant current driver
The traditional switching power supply is mostly based on constant voltage output. When the LED industry is just starting, it chooses AC/DC constant voltage power supply, with the current limiting module or non-isolated DC/DC constant current module. Because it is a non-integrated design, there will be performance matching and EMC compatibility issues when selecting, system efficiency is not optimized, and procurement and maintenance costs are also high.
2). Typical multi-channel constant current driver
The circuit uses PFC stage, isolated DC/DC constant voltage conversion stage and DC/DC constant current three-stage circuit (as shown in Figure 2). The integrated design allows the parameters to be optimized, and the overall efficiency of the LED driver is improved. However, since the three-stage circuit is still used, the efficiency is further limited. Secondly, the three-stage circuit increases the complexity of the circuit, which reduces the reliability of the driver to a certain extent and directly affects the service life of the LED lamp. Third, the use of three-level circuits has increased the material cost and manufacturing cost of the driver, and has become a paradox for the rapid development of LEDs.
For more information, please refer to the March issue of "High-tech LED-Technology and Applications" magazine
Advantages
Suitable for multiple operating wavelengths (1260nm – 1650nm); unstinted.
Equal splitter ratios for all branches.
Compact configuration; smaller size; small occupation space.
Good stability across all ratios.
Foreword
As the energy crisis and climate warming become more and more serious, energy conservation has become a topic of global concern. Lighting is an important aspect of human energy consumption, accounting for about 20% of the world's total energy consumption. Therefore, research on green energy-saving lighting has received more and more attention. Light Emitting Diode (LED) is a semiconductor light-emitting device that converts electrical energy into light energy. As a new high-efficiency solid-state light source, LEDs have miniaturization, low power consumption, long life, environmental protection, and color. Rich, fast response, high efficiency and energy saving. At the same brightness, the power consumption is only one tenth of that of ordinary incandescent lamps. LED lighting has become the focus of attention in the field of lighting. The incalculable potential of the LED lighting market is bound to ignite the huge demand for energy efficient LED drivers.
Development of LED drive technology
LEDs are used in a combination of connections, serial, parallel, and series-parallel combinations. The series mode can achieve natural current sharing, but the reliability is low. One of the LEDs fails to open, and the whole lamp will fail. At the same time, for high-power applications, the driving voltage will be high and cannot meet the SELV voltage requirements, which will increase the insulation requirements of the lamps and increase the system cost. Parallel use reduces the drive voltage and meets the SELV voltage requirements, but requires current sharing, and the total output current is high and the drive conversion efficiency is low. Therefore, in practical applications, for small power, there are many in series. For medium and large power, choose the combination of series and parallel to achieve a balance between conversion efficiency and reliability.
The following focuses on multi-channel constant current drive techniques for serial-to-serial combination. The multi-channel constant current driving technology has experienced the scheme of constant voltage driver plus multiple constant current driver, multi-channel constant current driver and adaptive driver.
1). Single AC/DC constant voltage driver plus multi-channel DC/DC constant current driver
The traditional switching power supply is mostly based on constant voltage output. When the LED industry is just starting, it chooses AC/DC constant voltage power supply, with the current limiting module or non-isolated DC/DC constant current module. Because it is a non-integrated design, there will be performance matching and EMC compatibility issues when selecting, system efficiency is not optimized, and procurement and maintenance costs are also high.
2). Typical multi-channel constant current driver
The circuit uses PFC stage, isolated DC/DC constant voltage conversion stage and DC/DC constant current three-stage circuit (as shown in Figure 2). The integrated design allows the parameters to be optimized, and the overall efficiency of the LED driver is improved. However, since the three-stage circuit is still used, the efficiency is further limited. Secondly, the three-stage circuit increases the complexity of the circuit, which reduces the reliability of the driver to a certain extent and directly affects the service life of the LED lamp. Third, the use of three-level circuits has increased the material cost and manufacturing cost of the driver, and has become a paradox for the rapid development of LEDs.
For more information, please refer to the March issue of "High-tech LED-Technology and Applications" magazine
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Advantages
Suitable for multiple operating wavelengths (1260nm – 1650nm); unstinted.
Equal splitter ratios for all branches.
Compact configuration; smaller size; small occupation space.
Good stability across all ratios.
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