Pulse Width Modulation Control Circuitry Design

My project is focused on the design and research of PWM switching power supply control circuitry that requires high efficiency and reliability. This chip incorporates almost all building blocks such as sawtooth oscillator, on-chip error amplifiers, 5V bandgap reference, deadtime control comparator, PWM comparator and output section. The pulse width modulation is accomplished by the comparison of the positive sawtooth voltage with two control signals. The internal linear sawtooth oscillator is frequency-programmable by two external components RT and CT. Both error amplifiers are used to sense power supply output voltage and current. In order to improve the reliability of this chip, the deadtime control comparator has an input offset which limits the maximum duty cycle of a given output. Its deadtime control pin is adjustable and can be connected for soft-start operation. The other comparator, PWM comparator provides a means for the error amplifiers to adjust the output pulse width. With output control grounded, this chip selects single-ended operation and with it connected to the reference line for push-pull operation. Now I have finished circuit design, simulation and layout design of this chip.This paper describes the design and research of this chip, based on top-down design method, comprehensively. In chapter two, I first point out the functional requirement of this chip and my idea for the design work. Then I make a detailed introduction of circuit design for each module. Chapter three focuses on the simulation work of this chip. From simulation results, we can see that my design fits the requirements. In chapter four, I introduce the layout design of this chip clearly.