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Design of high-efficiency LED lighting power supply based on bp2808

LED lighting has become the focus of attention for its characteristics of high energy saving, long life and environmental protection. In recent years, the manufacturing technology of high brightness LED light source has advanced by leaps and bounds, and its production cost has decreased steadily. Now, the use of LED light source as an energy-saving lighting source with high brightness, high efficiency, power saving and no carbon emission has become a massive demand in the world. An emerging industry manufacturing LED lighting equipment is rising, the industrial chain is improving day by day, and the technology is being updated day by day

bp2808 basic working principle

bp2808 is a constant current control chip that specifically drives LED light sources. Bp2808 works in the step-down system of continuous current mode. The chip controls the peak current and ripple current of LED light source, so as to realize the constant average current of LED light source. The chip uses very few external components to achieve constant current control, analog dimming, PWM dimming and other functions. The applied voltage range of the system is from 12VDC to 600vdc, and the maximum duty cycle can reach 100%; Suitable for AC 85v-265v wide voltage input, mainly used in non isolated LED lamp power drive system. Bp2808 adopts patented source drive and constant current compensation technology, which makes the current driving LED light source constant, and the change from AC 85v-265v is less than ± 3%. Combined with the driving system application circuit of bp2808 patented technology, the practical scheme of 18W LED fluorescent lamp makes the system efficiency higher than 90% in the AC range of 85v-265v. In the AC input range of 85v-265v, bp2808 can drive LED light source arrays from 3W to 36W, so it is widely used in lamp cups such as e14/e27/par30/par38/gu10 and LED fluorescent lamps

bp2808 has multiple LED protection functions, including LED open circuit protection, led short circuit protection and over temperature protection. Once the system fault occurs, the power supply system will automatically enter the protection state until the fault is removed, and the system will automatically re-enter the normal working mode. Multiplexed dim pins can be used for LED analog dimming, PWM dimming and dynamic temperature protection of lamp system. Bp2808 adopts s, and then calculates the area and area of each geometric shape and op8 package

typical scheme design for LED fluorescent lamp application

there are many power drive schemes for LED light source and light strip of LED fluorescent lamp. At present, the non isolation scheme is the mainstream because of its high efficiency, small size and low cost, while the majority of LED fluorescent lamp drive power supply is made of pwmled drive controller. In fact, traditional fluorescent lamps are non isolated

taking ac176v-264v full voltage input as an example, bp2808 is used as the main chip to design LED fluorescent lamps that fully meet the demands of environmental protection materials. When the load is low-power, multiple LED light sources, multiple strings, and multiple parallels, the design block diagram of the whole system scheme is shown in Figure 1. The whole circuit is composed of anti surge/lightning protection, EMI filtering, full bridge rectification, passive power factor correction (PPFC), starting voltage (including feedforward compensation, feed current power supply after startup, drive softening), constant current compensation, PWM control, source drive, LED light source array, sampling resistance, toff time setting, energy storage inductance, freewheeling diode and other parts

figure 1:18w LED fluorescent lamp system scheme design block diagram

led light source array is designed as 24 series and 12 series parallel schemes of 0.06w white LED (SMT or straw hat lamp), driving 288 low-power WLED, with a total power of 18W. The design circuit of full voltage 18W LED fluorescent lamp switch constant current source is shown in Figure 2, and the functions of each part are marked in red. In the figure, lightning resistance and EMI filtering constitute an EMC circuit, and the feed current power supply is realized by using the rectifier diode already made in the chip

figure 2:practical circuit diagram of 18W LED fluorescent lamp

seen from AC220V, the AC mains inlet is connected with 1A fuse F1 and surge/lightning resistant varistor VZ1; Next is EMI filter, which is composed of LD1, LC1, CX1 and CX2; Db1 is a full bridge rectifier with 4 high-voltage silicon diodes inside; CE1, CE2, R10, D2 ~ D4 form a passive power factor correction circuit; Bp2808 chip is started by R15 and R16. The resistance voltage is reduced by R17 and C3 feedforward compensation, and the patented constant current compensation circuit composed of DZ1, C2, R18 and bp2808 internal circuit is stabilized to supply power to bp2808 control circuit. After the system is started, because the static current of the control circuit itself is small, and there is a feed diode from out to VCC in the chip, it can provide working power to bp2808. At this time, the current passing through resistance R will be greatly reduced, Therefore, the total system power consumption is also greatly reduced, and the system efficiency is significantly improved. The patented source drive circuit is composed of MOS Q1, D6, RG, RT, RCS and bp2808 internal circuits, which is characterized by effectively reducing power consumption and improving constant current accuracy. The power circuit of the new standard gb/t16491-2008 "electronic universal testing machine" approved by the General Administration of quality supervision, inspection and quarantine and the national standards management committee in June 2008 reduces the current consumption of the system, especially the current similar to R in the traditional high-voltage differential power supply path, thereby reducing power consumption and improving efficiency. D6 and RG can make the on drive of the switch soft and the off drive strong, which can not only improve EMI, but also try not to sacrifice efficiency. The output filter capacitor C0 connected in parallel with the LED light source is used to reduce the current ripple on the LED light source

the CS terminal of bp2808 collects the peak current on the current sampling resistors RS1 ~ RS2, and the internal logic controls the pulse duty cycle of the out pin signal in a single cycle for constant current control. The output constant current is combined with the freewheeling circuit of d5 and LM1 to supply constant current to the LED light source. When the combination of LED light source array changes, the resistance value of resistance RS1 ~ RS2 will also change, so that the output current of the whole circuit can meet the requirements of LED light source array combination

the arrangement of PCB boards is the key to do a good job of products, so the wiring of PCB boards should be designed according to the requirements of power electronic safety specifications. This circuit can be used for T10 and T8 fluorescent tubes. Because the space size of the two tubes is different, the width of the two PCBs will be different. It is necessary to reduce the height of all parts in order to put T10 and T8 tubes. Figure 3 is the physical photo of T10 constant current source board. 30 components are installed on 0.8mm thick epoxy single-sided printed board

figure 3:physical photo of constant current source of 18W LED fluorescent lamp switch

if ac85v--264v full voltage input is designed, PFC should also be considered. The LED light source array can be designed into 12 series and 24 series parallel schemes of 0.06w white LED. Bp28 method for determination of bearing capacity of lubricants (4-ball method); 08 when designing the driving power supply of LED fluorescent lamp power supply, it is recommended to output voltage

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