The Research On Non-isolated Constant Current Driver Chip For LED

Nowadays with the energy shortage and environmental pollution problems become more apparent, LED lighting compared with conventional lighting has high luminous efficiency, no pollution, etc., is becoming one of the most promising high-tech in recent years.LED lamps only when driven at a constant current in order to maximize the play to its performance, in addition to non-isolated driver has higher efficiency, lower costs, and therefore the research on non-isolated constant current driver chip for LED has important significance and application value.Through the research on LED constant current drive circuit analysis, using non-isolated BUCK structure to output the constant current, not only has the high conversion efficiency, but also adapt to the change in inductance and output voltage automatically, which could comply a real current output. Based on the volt-second balance of inductor under BUCK circuit, the circuit works in critical conduction mode, compared with PWM models it is more efficient. The main function modules of the chip including: bandgap reference circuit, high and low voltage compensation circuit, and the chip integrated a plurality of protection circuits in order to ensure the system work in the stable and secure enviroment, including clamp protection circuit, over current protection and leading edge blanking, over temperature protection circuit, over voltage protection circuit. The constant current driver chip includes two aspects with normal working mode: when power MOSFET integrated in the chip is turned on, the input voltage supply the inductor and capacitor and the load at the same time; and when the inductor current rises to the peak, the power MOSFET turned off, inductance and capacitance supply the load. Because of the inductor and capacitor charging and discharging is linear, thus achieved the true constant current output.Each sub-module circuit of the chip was completly simulated and analysised by CADENCE simulation tools, the overall circuit chip systematically is simulated when the chip peripheral circuit is designed. Theoretical analysis and the results of simulation show that the chip satisfy design specifications. Finally, according to chip layout, DRC, LVS verify the feasibility of the layout.