With the optimization and popularization of insulating and heat dissipating materials, non-isolated driving solutions are the trend of the times. The practical significance of higher efficiency, in addition to reducing energy consumption, has increased the use of LED lamp beads, reduced costs, and provided power to consumers. At present, China's LED standard has not yet been established. Because of the fierce competition in the market, the current 3W isolation drive solution can reach very low cost, but there are some problems.
Introduction to the current mainstream 3W drive power supply
3WLED bulbs are one of the largest consumer demand markets. The current mainstream solution is 3×1W, each lamp is 3.3V300mA, and the load is formed by three lamp bead series. The output load is 10V/300mA. After the voltage is rectified and the output load voltage is quite different, the most suitable way is to drive the buck through the flyback isolation. However, the isolation circuit has a complicated structure, many devices, high cost, low efficiency, low reliability, and is not suitable for mass production. In contrast to the isolated circuit, the non-isolated circuit has a simple circuit, uses fewer devices, is small in size, has lower cost, and is more efficient. As the market demands cost and efficiency, non-isolated circuits are on the stage in the field of low-power LED drivers .
Figure 1 Schematic diagram of full-closed non-isolated buck constant current LED driver
DU8613 integrated switch simplifies the line to achieve full-loop 3W LED bulb constant current control
The DU8613 is a step-down constant current controller with continuous current operation mode. It has 3% constant current accuracy and integrates 500V high voltage MOSFET. It simplifies the peripheral circuit to a certain extent and sets the sampling resistor open circuit. Short-circuit protection, output over-current, short-circuit protection, over-temperature protection and other protection functions. The DU8613 is based on the TRUEC2 technology, which realizes a full-closed high-precision constant current control method, which is specifically used for 3W LED non-isolated bulb lamp driven chips. Figure 1 shows a step-down drive scheme implemented using the chip. The inductor current signal detected by the CS terminal of the chip of Figure 1 is processed by a patented technology, such as the TRUEC2 closed-loop constant current control module of Figure 2, to obtain an average value of the inductor current (ie, the output current). The chip controls the switching tube duty cycle by detecting the different average values ​​of the output currents, thereby implementing closed-loop control.
Figure 2 DU8613 internal function diagram
Figure 3 DU8613 bulb application physical map and its PCB layout
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