The Design Of Current Mode DC-DC Converter With PWM Controlled

With the rapid development of electronic technology, the life of modern can't leave all kinds of electronic products, such as cellular phones, personal digital assistants, and notebook. Driven by the prevalence of semiconductor integrated circuits and all electronic circuits, the cost, and size of the electronic systems must be reduced as much as possible. Using advanced semiconductor processes can solve the solution of those problems. The performance requirements were cited to the direction of saving power and high efficiency. Battery is the only power source for portable equipment. In order to prolong the service time of these battery-operated equipments, ultra-low-power consumption is demanded. The main method that decreases the power losses is to higher the conversion efficiency and to lower the operating voltage. The stated intention is to create a new architecture that can make higher efficiency.The converter is a high frequency, current-mode step-up regulator. The integrated high-efficiency MOSFET and the IC's built-in soft-start function reduce the number of external components required while controlling inrush current. With its high closed-loop bandwidth performance, it provides fast-transient response to pulsed loads while operating with efficiencies over 85%.The traditional error amplifier and comparator replaced by sum-comparator. The internal power MOSFET minimizes the external component count while achieving high efficiency by incorporating a loss-less current-sensing technology.The oscillation can provide pulse for the chip, and as compensate current for current mode.Design a voltage reference, which can generate 1.25V voltage and source at least 50uA, guarantee the chip circuit in the appropriate bias condition. At the meantime, we can get several different kinds of voltage by using resistance to separate the voltage.Thinking of the unexpected situation, the thermal shutdown circuit forces to shut off entire circuit when the temperature surpasses 150oC, when the temperature recedes 135o C, the entire circuit wills works normally. In every module of a practical circuit, the enable-control is added to reduce the quiescent current as much as possible.The whole circuit designing based the model of the system, then confirm the need module and the correlative capability. In this case, we take 0.6um CMOS process from some foundry company. The simulation result will show that with the current-model control maximize fast-transient response and have the high close-loop bandwidth, higher efficiency, which can reach 87%.