| Recently, LED has received enormous attention from our society and walked into the high-speed development mode as a green, fresh-new type of illumination source. LED embraces the increment in application due to its advantage over traditional illumination sources in pollution, high energy efficiency, longevity. The penetration of LED brings chance and challenge to its driver chip. Low power dissipation, high energy efficiency, high resolution and safety are the main concerns of the state-of-art LED driver chip.This article focus in design of a high-resolution output driving current, two-wing, violated AC-DC type LED drive chip. It can keep its output capacity of 300 mA output current and maximum 3 LEDs with 3V turn-on voltage between 85 V to 265 V of AC input magnitude. Firstly, a comprehensive analysis of AC-DC switch mode power supply based driver and its specifications table is given out. Secondly, modules such as band gap reference, power on reset circuit, secondary current zero cross detect, constant output current control circuit, PWM comparator, leading edge blanking circuit is designed and run for simulations. Protection regimes are also added: input under voltage lock out, CS pin protect, over temperature protection, open and short circuit protection. All the parameters in schematics and specifications have been verified in Cadence Design System. Meanwhile, the overall simulation of circuit within the chip combining with periphery circuit is accomplished and the result exhibits well performance of the circuit design and meets the demand of specification table.The design is fabricated on 0.8um 5V/40 V 2P2M high voltage BCD process. A series of actual test jobs is conducted on this chips with loading LEDs. DC test results satisfy all the specifications mentioned. Under the loading condition of 300 mA output current and 3 LEDs each with 3V working voltage, the max relative deviation of output current is smaller than +5% when input AC voltage changes from 85 V to 265 V. |
PDF Full Text Request