A Design For Zero-Detection Circuit Of Synchronous Rectification Buck DC-DC Converter

In1960s, switching power supply began to appear, the history of the development has been more than40years. Because of its higher efficiency, the switching power supply becomes the most widely application in various fields today instead of linear power supply. With the development of various types of electronic equipment, switching power supply begins to be smaller and more lightweight, it also requires less electromagnetic pollution, higher reliability, and higher efficiency. The contribution of switching power supply in the field of electronic equipment is more and more important, it has already become a part of the electronic equipments, its performance directly affects the performance of various kinds of electronic equipments.With the development of switching power supply, converter is playing an increasingly important role as a part of the switching power supply. Due to the high efficiency and low loss characteristics, The application of synchronous rectifier BUCK DC-DC converter in various fields becomes more and more widely. However, due to the impact of logic delay and parasitic and other factors, the current on the inductance of the converter in DCM mode easily produces the current intrusion phenomenon, so that the output voltage of the converter produces great fluctuations, it reduces the conversion efficiency of the whole system.To solve the problem, after understanding the current detection technology development and the current research situation, with the application background of synchronous rectifier BUCK DC-DC converter, combined with the characteristics of all kinds of classic design of current detection circuit, we researched and designed a zero current detection circuit. Based on the0.6μm CD, we simulated the zero crossing detection circuit designed in this thesis using Hspice software and compared and analyzed the simulation results.Through the analysis of simulation results, we know that the comparator gain is76dB, increased transmission delay is about0.1μs, and the conversion speed is very fast, it could be about85ns. the comparator has a very high sensitivity because of its high gain. The zero crossing detection circuit’s deviation of the current turning point during-40℃and125℃is only0.64mA, and the maximum deviation is only0.66%. It is proved that the influence of temperature is very little. The deviation of the current in different process corners is only1.19mA, the maximum deviation in the SS process deviates is only1.25%. It is proved that the dependence of zero crossing detection circuit on the process is very low. When the load current is50mA, inspection sampling precision is very high, it is about98.4%, it has stable performance. The circuit power loss is also very little, it is to be only24μA.The circuit is designed in this paper and the typical zero crossing detection circuit in the literature are compared, the results show that the resistance of the circuit designed in this paper on the temperature and process is higher, the detection accuracy is also higher, and the power consumption is lower, fully shows that the circuit designed in this paper is very successful. The design of the zero crossing detection circuit has high detection precision and good stability of the system during the change of process and temperature, and the power consumption is very low, so that the performance is excellent.