Investigation On Zero-Cross In Efficiency Synchorous Boost Converter

With the development of electric and communication technology, portable power is increasingly becoming the most important application area for power semiconductor integrated circuits. High level of integration, high efficiency and low cost are the most desired features for portable power ICs.In view of the high efficiency of detection circuit current-mode power management chips or other electronic highway simulation applications, such as the incomparable role in the current academia, industry has invested a lot of energy on more mature detection methods and on relatively high-performance detection circuit.The purpose of the design is to widen the scope of the load with high efficiency, that is, not onlyverter can load range with high efficiency, that is, not only in the heavy-duty situations converter has high efficiency, but also improve the efficiency of light-load. When small or medium-sized power equipment is in the idle state, that is, light-load or no-load conditions, the PWM control mode jumps to pulse-skipping PFM mode automaticly, PSM model. When electrical equipment is dormant, the load of power chip is in light-load conditions, which means that the inductor current may be discharge to zero before next recharge cycles (Discontinuous Current Mode DCM mode), once the inductor current is zero, the regulator capacitance will be charged through the Synchronous rectifier (SR), at that time the inductor current jumps into reverse, this paper presents a zero-current detection circuit, when the inductor current value in a small, close the SR, the Schottky begin to work to extend the maximum working hours of the SR, and avoid the reverse inductor current to achieve maximum efficiency upgrade. Taking into account delay in the circuit, including the comparison of the zero-current conversion, logic delay, delay and driving circuit interrupters closed delay. If the threshold of the zero-current detection comparator is setted exactly when the inductor current is zero, inductor current flow backward will be likely to occurre, so advanced shutdown is taken into account. This paper will compare with zero-current threshold set in the inductor current of 50mA, when the inductor current drops to 50mA, zero-current comparators and overturned, the PMOS closed.Based on the zero-current detection circuit design specifications, the paper has described how to choose the control mode, how to choose resistance model, as well as switch and the size of a SR research, and to achieve a higher degree of accuracy, but has also carried out Resistance tuning, the final design of the proposed structure of the circuit, the principle of detailed analysis and system simulation.Finally system performance parameters, such as the performance of instability, parameters drift and degradation and so on, tolerance analysis is done to the structure of the design. It greatly reduced the workload of the establishment of circuit model and avoided the handling of complex computing, not only the realization of EDA technology-based generic circuit tolerance analysis technology and methods, but also to achieve circuit performance and reliability of the parallel design.