Precision Parallel White Led Driver Circuit Design

The high precise parallel white LED driver is used for backlighting a color LCD. Recently, there are a lot of companies both at home and abroad that have already conducted in-depth researches in this regard. White LED is one kind of lighting devices driven by current. The intensity of LED illumination is proportional to the current through it. Parallel white LED driver provides the power to white LEDs and regulates the current intensity of them according to practical application.A high precise parallel white LED driver with finer current control precision and matching precision is analyzed and designed in the thesis. And the chip was tested after taped out successfully. There are two relatively independent sub-blocks in the system: self-adjusting charge pump and parallel LED current control driver. The charge pump automatically switches between 1x/1.5x modes based on the input voltage, to maintain correct output levels at a high power efficiency. The LED driver regulates the current of LEDs to a value configured by the outside control signal. The four LED output channels are current matched for consistent LED brightness. The chip was taped out successfully by using 0.5μm CMOS process with wide input voltage range of 2.7V to 5.5V. The driver has the quiescent current under 1μA and also has soft-start circuitry to limit inrush current flow at power up. The chip can be operated normally in the temperature range of -40℃to 85℃according to the simulation results. The brightness of the white LEDs can be controlled by using a DC voltage or a PWM signal applied to the pin with a few external components added. Compared with traditional pattern, the proposed circuit improves the control precision and LED-to-LED matching precision.The whole system analysis and sub-block design were proceeded to the function requirements. Typical sub-blocks were analysed emphatically such as Switch Capacitor Sampling/Holding Block, Brightness Control Block, Oscillator, Thermal Shut Down Circuit, PTAT and Bandgap Reference etc.Principle and operation of driver circuit are analyzed in the thesis. Based on that, the author simulated most of the sub-block circuits and whole chip circuit by applying EDA tools HSPICE. The simulation results indicate that the IC has achieved the expectation,...