| Power supply is one of the important elements of the electronic equipment; its influence on the stability and reliability of electronic equipments is becoming stronger and stronger. With the development of electronic technology, the type of electronic equipments is becoming more and more, therefore, the requirements for power supply are various. With advantages of simple structure, convenient regulation and high reliability, BUCK DC/DC converter is widely used in voltage step-down situation.BCD process is a novel one that combines DMOS and low voltage BiCMOS process together; its advantages are low power dissipation, high integrity and strong drive. According to design method of ASIC, operation principle of BUCK DC/DC converter and pulse width modulation technique of current mode, a monolithic BUCK DC/DC converter IC based on BCD process is designed, which is integrated with many function modules, such as band-gap reference voltage circuit, over-thermal protection circuit, error amplifier, voltage comparator, saw-tooth oscillator, bootstrap drive circuit, under voltage lockout circuit, current sensing circuit and over-current protection circuit, etc. all these circuit structures and operation principles are designed and simulated. This chip features its unique frequency conversion proection, which can reduce duty cycle and operation frequency so as to decrease short-circuit current and power dissipation and guarantee the safety of the power supply when output is short-circuited. When the EN pin is low voltage, the chip operates in shutdown mode and its static current and power dissipation is low, so it is easy to realize remote and timing control. This chip can constitute a BUCK DC/DC converter with a minimum number of external components; thus, it can be widely used in distributed power systems, battery chargers and pre-regulators for linear regulators.The feasibility and validity of design method and theory analysis are proved by the... |
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