Recent developments and prospects of new technologies for mass LED lighting

In 2013, it will be the year of mass lighting, LED lighting, design, production and marketing. The cost performance of mass lighting LED lamps will determine the vitality, competitiveness and mass productivity of newly developed affordable LED lamps; It is a common consumer electronic product that people all over the world can afford. Its retail price should be close to or lower than the price of current fluorescent energy-saving lamps. Therefore, a flat LED lamp solution with suitable design performance and competitive price performance is the key. Low-cost solution to the current low-voltage LED light source (LV LED) due to low voltage (VF) and high current (IF) working hot bottleneck has been solved without any solution; but the innovative multi-core package HVLED, its high voltage (VF), small current (IF) working conditions alleviate the heating degree of LED light source; LED drive constant current power chip through the efforts of Chinese and foreign power chip integrated circuit designers, high functional integration, application circuit is simple, cost-effective chips emerge one after another In recent years, the emergence of heat-conducting plastic radiators and plastic-coated aluminum radiators has solved the problem of isolation technology in the narrow space of LED lamps. Therefore, the mass-production and mass-marketing of mass-market LED lamps that can be afforded by ordinary people and used well is already very close!

LED lamp bead technology innovation changes

The innovation of LED lamp bead packaging technology has led to an increase in LED light efficiency every month. The price of LED lamp beads has been declining. High-voltage LED (HV LED) technology has become increasingly mature, and the heat of LED lamp cavity has become a reality. The LED light source modules for low-cost LED lamps are COB , COF and multi-core package HVLED. The cost of LED light source modules in the market is RMB1.00-0.80/W, among which COF and multi-core package HVLED may be preferred by cheap LED lamps.

LED packaging technology has the LED die package on the aluminum plate "COB" (chiponboard), without using a flip-chip goldsmith lines and lead eutectic growth technique "flip-chip and eutectic COB", the LED will The "COF" (chipon frame) with a core diameter bonded to a copper bracket eliminates the need for gold wires and packages, and is directly fabricated into an "ELC" (embedded LED chip) that can be used by the final customer in the LED manufacturing process. Packages 2, 3, 4, 6, and 8 LED dies in a "multi-core package HVLED" that combines N LED beads into HVLED applications. These six new LED packaging technologies have brought new ideas to LED luminaire design (Figure 1). The innovative packaging technology of LED light source guides the development of high-voltage and low-current LED light source, which reduces the heating degree of LED light source board. Therefore, the design of low-priced LED light fixture has a new choice. The typical COF product is shown in Figure 2, and the ELC product is shown in Figure 3.

Figure 1 LED lamp bead packaging new technology

Figure 2 COF typical products

Figure 3 ELC products

Non-isolated constant current drive power is becoming mainstream

The LED driver power supply for the mass illumination flat LED lamp has a non-isolated switch constant current source, a PSR isolation switch constant current source and a high voltage linear constant current source.

Non-isolated switch constant current source is suitable for high voltage, low current LED load applications, mainly multi-core package or N series HVLED light source. Non-isolated switch constant current power supply has the advantages of low cost, high efficiency, small size, non-isolated switch constant current power supply products use single winding inductance, which can reduce cost and improve production efficiency; built-in high-voltage MOSFETs of different sizes to improve the cost performance of application power supply; And PCB can be used in different power sources to reduce the inventory of production plants. A typical non-isolated switch constant current power supply circuit is shown in Figure 4. Since the functions of the chip are highly integrated, the application line is very simple. Figure 5 shows a 2.5-inch 3.5W (7X0.5W) LED downlight from PHILIPS. Its non-isolated switching constant current power supply uses the BP2802 chip from Shanghai Jingfeng Mingyuan. After the nuclear power accident, Japan also vigorously promoted the LED lamps of non-isolated switching constant current power supply. The main consideration is the utilization of efficiency. The Japanese government directly subsidizes 50% of the price when purchasing LED lamps, which is the source of power for the majority of people to choose LED lamps. . Many Chinese and foreign manufacturers of LED lamps pay attention to the efficiency of LED lamps. Therefore, non-isolated constant current driving power supplies have gradually become one of the mainstream of power supply for mass lighting LED lamps.

Figure 4 Typical non-isolated switch constant current power supply circuit

Figure 5 PHLIPS downlight with non-isolated switch constant current power supply

PSR isolated constant current power supply cost-effective

PSR (primary side control) isolated constant current power supply cost-effective and competitive, PSR isolated constant current power supply is suitable for high current, low voltage LED lamp beads, which is currently widely used low voltage LED (LVLED) lamp beads. Innovative design of PSR isolated constant current source chip, the function of high integration makes the application circuit very simple, resulting in simple structure design of the lamp, easy to over-safe; the algorithm innovation inside the chip makes it insensitive to the electrical parameters of the transformer, the transformer is reduced to Only 2 windings reduce cost and increase production efficiency; built-in high-voltage MOSFETs of different sizes increase cost performance. A typical PSR isolated constant current power supply circuit is shown in Figure 6. The BP3122 switching constant current source chip is used. The BOM cost of the 5W power supply is RMB 2.00. Shenzhen Guke Semiconductor has a monthly output of 6-10KK.

Figure 6 Typical PSR isolated constant current power supply circuit

High-voltage linear constant current driving power supply is simple and inexpensive

The high-voltage linear constant current driving power supply is a new-generation mass illumination LED driving power supply technology with high voltage and small current HVLED. It has no switching frequency from its own buck-boost. The application circuit has no magnetic components and no electrolytic capacitors; therefore, it has a high Efficiency, higher PF, lower THD; and easy to be compatible with thyristor dimmers; it operates at high voltages and low currents, so HVLED panels have lower heat generation.

In the high-voltage linear constant current power supply scheme, since there is no magnetic device such as a transformer and no electrolytic capacitor, the cost of the general switching constant current power supply can be saved by one-third, the application circuit is simple, and the cost is low; the introduction of the heat-conductive plastic heat sink solves the isolation. Safety technology issues, therefore, the application of high-voltage linear constant current source in integrated photovoltaic modules (or integrated photoelectric engines), cheap LED lamps will rapidly develop. A typical high voltage linear constant current drive power supply is shown in Figure 7.

Figure 7 Typical high voltage linear constant current drive power supply circuit

The high-voltage linear constant current source is a new power supply technology for segmenting LEDs. The mains is pulsating DC through bridge rectification. The pulsating DC envelope is equivalent to the AC sine wave, which is automatically changed according to the sine wave of the bus voltage. Switch the LED string and light up the three strings of LED beads in turn as the bus voltage rises. When the bus voltage rises and reaches the first LED on-voltage, MOS1 turns on and the LED1 string lights up; when the bus voltage continues to rise and reaches the sum of the first and second strings of LEDs, MOS2 automatically turns on, LED1 Simultaneously illuminate with the LED2 string; when the bus voltage continues to rise until the three strings of LEDs can be turned on, MOS3 turns on, and the LED1, LED2 and LED3 strings illuminate almost simultaneously. If the bus voltage drops, the process is reversed, and the segment conduction state is shown in the lower left panel of Figure 7.