Feedforward Control Voltage Type Pwm Dc Converter Ic Design

Power supply is the heart of the electronic devices. The performance of the electronic device is mainly determined by the supply capabilities. As one of the most widely used supply, the switch power supply, has replaced the conventional linearity power supply in the most of the occasions and become the first choice in the most application electronic devices with its advantages of more compact size, lower weight, and better efficiency. DC/DC converters have occupied the major market in small and mediate size electronic devices such as computers, mobile, portable device, etc.A power supply IC for OLED and other small electronic devices with dual voltage outputs is proposed in this thesis, which consists of two separate systems for simultaneous positive and negative output to satisfy the requirement that both voltage supplies are needed for driving OLED. A boost and negative converter are used for the generation of positive and negative output, respectively. Furthermore, the IC exhibits high integration level that very few external parts such as capacitances and inductances are needed.The internal power MOSFET integrated inside the IC is controlled by sampling the input and output voltage to control the output voltage. This IC uses the voltage–mode PWM to control the circuit. The feedback of the output voltage is the major control loop. To achieve better frequency response and disturbance rejection of the input voltage, a input voltage feed-forward system is introduced in control loop. The duty-cycle of PWM applied at the gate of power MOSFET is modulated by both input and output voltage. A high precision oscillator, PWM control module, protection module and power MOSFET are also integrated on the die. In order to reduce the power loss due to diode threshold voltage-drop, the synchronized commutate MOSFET is also integrated.The fundamentals of switch power supply are firstly introduced in thesis where the control module of positive output voltage is discussed in detail, which is followed by the sub-blocks simulation, the feed-forward system analysis. The whole system simulation by HSPICE indicates that the circuit will operate well when the input voltage ranges from 2.7 to 5.5V and the efficiency can up to 80%. The system will response quickly in one or two cycles and remain stable output voltage when a step disturbance is applied on input voltage.