As incandescent lamps, fluorescent lamps, and energy-saving lamps have gradually withdrawn from the lighting market, LED lighting sources and LED lighting fixtures have developed rapidly, sweeping the world lighting market with lightning speed, and the LED industry chain has flourished. The brightness of LED lamp beads is constantly increasing, and the price is gradually decreasing. HVLEDs and flip-chip LEDs are developing new application technologies for LED lighting; LED driver power chips are constantly being introduced, more integrated functions, better cost performance, more convenient application; plastic aluminum and high Thermally conductive plastic heat sinks provide an innovative new design space for next-generation LED light sources and luminaires.
Indoor LED light sources and lamps are bound to be a large number of consumer electronics products, which will certainly be produced in large quantities and have a blue ocean market. Since the space for the conventional lighting source and the lamp reserved for the LED driving power source is very small, the driving power source of the LED lighting source and the lamp must be made very compact, and the driving power chip requires high performance integration, and the single-level chip is mainly required. The entire drive power solution is not only very simple, but also low cost; the application circuit requires fewer peripheral devices, and the total number of chips + peripheral parts requiring LED drive power is less than 15, or even less than 10. The LED power drive circuit uses a compact transformer, an inductor, a lower-level electrolytic capacitor, and even a power drive circuit that does not require an electrolytic capacitor, inductor, or transformer.
Figure 1 The main mode of indoor LED lighting drive
1 LED drive power main mode
At present, the indoor LED lighting source and the driving power supply of the lamp are divided into two modes: constant current isolation and non-isolated driving, high-voltage linear constant current driving, etc. The RC resistance-capacitance step-down is due to its large power consumption and unsafe, constant current and many bad The factors are already being phased out. The advantages of RC resistance-capacitor step-down drive: simple circuit and low cost; its disadvantages: poor grid compatibility, small output current, large power consumption and unsafe. The advantages of switching constant current drive: stable performance, high efficiency, strong grid compatibility, convenient function expansion, boost, step-down, buck-boost application are convenient and free; its disadvantages are: large volume, complicated production and slightly higher cost. The advantages of high-voltage linear constant current drive: stable performance, easy automatic production, no plug-ins and a lot of labor saving; its disadvantages: the lamp bead utilization is slightly lower, and there is a slight residual power frequency ripple. The main mode of indoor LED lighting drive is shown in Figure 1.
LED driver 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, etc. LED lighting drive power must be integrated in a single-chip chip in. The indoor LED lighting source and the narrow space of the luminaire limit the driving power chip to adopt a single-stage chip, which requires the function of the driving power chip to be highly integrated, the power control function and various protection functions are integrated into the chip as much as possible, and the driving power chip is driven. Topology design technology must be innovative, and new models must be created to meet the innovative development of LED lighting drive technology.
2 non-isolated switch constant current drive has become mainstream
The rise of thin plastic-clad aluminum radiator technology and HVLEDs technology solves the safety problem of internal high-voltage electric leakage when the AC mains high voltage is turned on and the LED lamp bead is turned on. The plastic aluminum radiator is simply and easily solved. LED light source and the internal high voltage and external isolation of the lamp are difficult. Therefore, the non-isolated switch constant current drive power supply with simple application circuit has become the mainstream power supply solution for general-purpose low-cost LED illumination source and lamp. Non-isolated switch constant current drive power chip has been developed and updated over several generations. Nowadays, there are more integrated functions, simpler application circuits, lower application cost, and more cost-effective power supply.
In view of the reduced heat generation of the HVLEDs, the plastic-coated aluminum radiator simply solves the high and low voltage isolation in the LED lamp. The selection of the driving power source is based on constant current accuracy, power supply efficiency, power factor compensation (PFC), and isolated. Switching constant current power supply is generally 70%-88% due to the use of transformer, power factor compensation is less than 0.9; non-isolated switching constant current power supply constant current accuracy can reach 3%-5%, power factor compensation is greater than 0. 9, the power efficiency is greater than 90%, so it has become the first choice for LED lighting. The non-isolated constant current power supply has two types of non-isolated switching constant current power supply and high voltage linear constant current power supply.
The non-isolated switch constant current driving power supply chip design has been highly integrated, and the functions required for the LED driving power supply, such as wide voltage input high precision constant current output, over current protection, over voltage protection, LED short circuit and open circuit protection, and CS resistance short circuit have been short-circuited. The necessary functions such as protection, chip power supply undervoltage protection, etc. have been integrated into a single-stage chip. The MOS tube and constant current control of the power output are also integrated on a single chip. The application circuit is very simple, and the peripheral parts can be generally controlled in 15 Below, it helps to effectively control material costs and production costs for end customers.
Figure 2 BP2831A non-isolated switch constant current source
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