Design Of The LED Driver Chip Based On The Primary Side Feedback Control Technology

LED lights for its energy saving, environmental protection, high luminous efficiency, long life and good condenser property. It has been more and more widely used in industrial, transportation, and home lighting. However, in order to make LED lights to work properly play to their own advantages; it must be provided with the appropriate driver circuitry. PSR control LED driver is a new LED-driven approach rising in the past decade, comparing with the traditional secondary side feedback LED driven mode the control loop eliminates the optocoupler and TL431 chip, so the system cost and size is reduced, efficiency is improved.In view of the advantages of PSR control LED driver circuit, a primary side feedback control LED driver chip is designed which is used in low-power LED driver domain. The chip consists of: power supply module, soft start module, constant current control module, constant voltage control module, over-temperature protection module, logic control module and an output driver module. W hen the system operating in the constant current control period, the system uses a pulse frequency modulation(PFM) mode to realize of the constant current control to the output current; and when the system is operating in the constant voltage control mode, the system uses a pulse width modulation(PWM) mode to achieve constant voltage control of the output voltage, you can freely switch between the two control modes and mutually affect each other between. In order to sample the accurate output voltage, a circuit was designed in the chip to sample the output voltage at 2/3 times of the secondary side degaussing time. C hip frequency jitter module is also provided, the system operating frequency jitter within a certain range to reduce electromagnetic interference of the system and there is no effect on the output voltage and current.The chip based on the primary side feedback control LED driver chip design in this article is achieved by a company’s 0.5um 25 V BCD process. Us ing Spectre simulator of Cadence IC6151 platform for circ uit simulation, simulation results show that the chip can achieve constant voltage, constant current control over the full voltage range 90V~265V and the electromagnetic of the system is largely reduced.