Constant current drive LED circuit based on LM2734

　　LM2734 is a 1A step-down voltage regulator. It uses the LM321 operational amplifier to obtain the voltage on the sampling resistor Rset, and combines it with other resistors and capacitors to form a complete and efficient high-power LED constant current drive circuit .
　　In the circuit, the sampling resistor Rset determines the design of the constant current drive circuit and has an important impact on the efficiency of the entire system. Therefore, the design parameters of Rset are crucial to saving energy. Generally speaking, if the LED driving current is required to change no more than 5% to 10% of the nominal value, then a resistor with an accuracy of 2% is sufficient. The typical fluctuation range of LED drive current is ±10%. Since the sampling resistor consumes a large amount of power, the use of smaller power chip resistors should be avoided. In addition, the LM3478 solution is suitable for constant current drive of multiple high-power LEDs, while the constant current drive design solution based on LM 5021 is targeted at the application of 220V AC /DC converters.