LED lighting drive technology innovation and development

With incandescent, fluorescent, and energy-saving lamps gradually withdrawing from the lighting market, LED lighting sources and LED lighting fixtures are rapidly developing. With lightning speeds engulfing the world lighting market, the LED industry chain has flourished. The brightness of the LED lamp beads continues to increase, and the price gradually decreases; HVLEDs and flip chip LEDs open up new application technologies for LED lighting; LED driver power chips continue to be innovative, with more integrated functions, better price/performance ratio, and more convenient application; plastic-clad aluminum and high Thermally conductive plastic radiators provide a new space for innovative design of next-generation LED light sources and lamps.

Indoor LED light sources and lamps must be large-scale consumer electronics products will be mass production, with the Blue Ocean market. As the space for traditional lighting sources and luminaires is reserved for LED driving power, the driving power of LED lighting sources and luminaires must be made very compact. The driving power chips require a high degree of integration, and single-stage chips are the main requirements. The entire drive power solution is not only very concise, but also low in cost; the application circuit requires fewer peripheral devices, and the total number of chip+peripheral parts required for the LED drive power is less than 15, or even less than 10. The LED power driver circuit uses a delicate and compact transformer, inductor, and a lower electrolytic capacitor, and even the power driver circuit does not require an electrolytic capacitor, an inductor, or a transformer.

LED drive power main mode

At present, the driving power supply of indoor LED lighting sources and luminaires is divided into constant-current isolation and non-isolated driving, high-voltage linear constant-current driving, and several other modes. RC resistance and voltage reduction are inherently unfavorable due to their high power consumption, unsafe, and constant current. Factors have been eliminated. The advantages of RC RC resistor and buck driver are: simple circuit and low cost; its disadvantages are poor compatibility of the power grid, low output current, large power consumption, and insecurity. The advantages of switching constant current drive: stable performance, high efficiency, strong compatibility with the power grid, convenient function expansion, boost, buck, and buck-boost applications are convenient and free; its disadvantages are: large volume, complex production, and high cost. High-voltage linear constant current drive advantages: stable performance, easy automation production, no plug-in large savings in labor; its shortcomings: slightly lower lamp utilization, a slight residual frequency ripple. The main mode of indoor LED lighting drive is shown in Figure 1.

LED drive single-stage power chip requires built-in high-voltage MOS tube, line voltage compensation, source drive, over-voltage / over-current / over-temperature protection, open / short circuit protection and other LED lighting drive power necessary technology must be integrated in the single-stage chip in. The limited space of indoor LED lighting sources and luminaires defines the driving power supply chip as a single-stage chip. This requires a high degree of integration of the functions of the driver power supply chip, power control functions, and various protection functions integrated into the chip as much as possible to drive the power chip. The topology design technology must be innovative and continuously create new models to meet the innovative development of LED lighting drive technology.

Non-isolated constant current drive has become mainstream

The rise of thin plastic aluminum radiator technology and HVLEDs solves the problem of internal high-voltage leakage to the human body when the AC mains high-voltage power LED lamp is turned on, and the plastic aluminum radiator is solved simply and easily. LED light source and the interior of the lighting and high voltage isolation from the technical difficulties, the use of a simple application of non-isolated switching constant current drive power has become a common low-cost LED lighting and lighting mainstream power supply program. Non-isolated switching constant-current driving power supply chips have undergone several generations of development and updating, and now more integrated, simpler application circuits, lower application costs, and more cost-effective power supply.

In view of the fact that the HVLEDs light source reduces heat generation, the plastic aluminum heat sink simply solves the high and low voltage isolation in the LED lamps. The selection of the driving power source is based on constant current accuracy, power efficiency, and power factor compensation (PFC). The overall efficiency of the switching constant current power supply is generally 70%-88% due to the use of a transformer, and the power factor compensation is less than 0.9; the constant current accuracy of the non-isolated switching constant current power supply can reach 3%-5%, the power factor compensation is greater than 0.9, and the power supply efficiency Greater than 90%, therefore becoming the first choice for LED lighting fixtures. Non-isolated constant current power supplies are non-isolated switching constant current power supplies and high voltage linear constant current power supplies.

Non-isolated switching constant current driver power supply chip design has been highly integrated, and has required LED driver power supply functions such as wide voltage input, high precision constant current output, over current protection, over voltage protection, LED short circuit and open circuit protection, CS resistor short circuit The necessary functions such as protection and chip supply undervoltage protection have been integrated into a single-stage chip. Power output MOS transistors and constant current control are also integrated on a single chip. The application circuit is very simple and the peripheral parts can generally be controlled at 15 The following can help effectively control the material cost and production cost for the end customer.

The non-isolated switch constant current drive power supply application scheme is simple and cost-effective. As shown in Figure 2, the 5W LED bulb lamp power supply designed by non-isolated switching constant current source chip BP2831A, output DC80V, 60mA, including the main chip, the total circuit application of a total of 15 components, power efficiency at AC220V, full load Up to 92%, the power supply can pass EMC test. The PCB of this power supply can be as small as Φ18mm in diameter.