Design Of High Efficiency Low Ripple Buck DC-DC Power Chip

With the development of semiconductor technology,switching power management chip have entered the era of high integration.Various types of portable devices similar to mobile terminals have increasingly higher requirements for DC-DC conversion chips,high efficiency,low interference and low power consumption,and small size is the mainstream research direction of DC-DC switching power supply chip.This paper Taking the development status and future development trends of switching power supplies at home and abroad as the research background,and combining a large amount of related literature,a detailed analysis and research of high-efficiency DC-DC conversion chips is made.At the same time,combined with the joint project of the laboratory and the company,a buck DC-DC power chip with high efficiency and low ripple output was designed.It requires an input voltage range of 3V to 5.5V,a stable voltage of 1.8V,and a maximum output current of 1.5A.The switching frequency is 1.5MHZ,and the highest conversion efficiency must be greater than 90% Ripple output voltage should be less than 2mV.Firstly,This article describes the inductive volt-second balance rule in DC-DC converters,and then briefly analyzes the DC-DC topology,modulation method,control method,and performance indicators that need to be considered.After combining the product application environment and functional requirements,the system-level frame design of the chip is given,including the design of the main circuit modules such as the band-gap reference source,error amplifier,current sampling circuit,soft-start circuit and over-temperature protection.In particular,improvements have been made to the current sampling circuit,thereby improving the efficiency and stability of the chip.At the same time,the capacitor multiplying principle is used in the error amplifier and the soft start circuit to design the capacitor to achieve the purpose of small area and large capacitance.Then,in order to prevent the chip from being damaged at high temperature,a hysteresis of 15 ° C was introduced in the over-temperature protection circuit.All the above functional modules were simulated and verified with the help of Cadence platform,and the layout planning of each module of the power chip was carried out at the end.Get the actual layout.The WKD8009 DC-DC conversion chip is designed and simulated based on HuaRun Shanghua's 0.18?m BCD process.The following results are showed that the output voltage is basically stable at 1.8V within an input voltage range of 3V to 5.5V,with and without load,and the maximum conversion efficiency can reach 95.2 %,Ripple voltage is about 1.1mV.And test and verify the chip after tape-out,the test results indicate that the performance indicators of the chip have reached the design requirements.Compared with the work done by the predecessors,it is proved that WKD8009 has obvious advantages in conversion efficiency and ripple voltage.