Design Of Low Starting Voltage Boost Switching Converter Using COFT Control

In recent years,with the rapid increase in sales of battery-powered portable devices and wearable devices such as mobile phones,digital cameras,etc.,because portable devices themselves are developing towards high battery life and small size,they are very concerned about the die size and power consumption of DC-DC switching power supply.In addition,since the output voltage of several common batteries is related to their remaining energy,the low starting voltage means that the battery can continue to supply power at a lower remaining capacity,which can undoubtedly improve battery life.The ultra-wide input voltage range means that users can choose different types of batteries more freely according to the specific user environment and functions of the device.In general,chips with small area,low power consumption,low starting voltage,and wide power supply voltage range are more suitable for battery-powered portable devices.This dissertation designs a micro-power low-start-up Boost converter with constant off time?COFT?control for battery-powered portable devices and wearable devices.In order to achieve the purpose of minimizing the chip area,the chip uses a hysteresis comparator to achieve loop control the reason of avoiding complex loop compensation design:Compare the sampled voltage with the reference voltage.When the sampled voltage is lower than the reference.The LDMOS is on and a fixed peak current is used to modulate the TON time.When the sampled voltage is higher than the reference then the LDMOS is off for a fixed time.Because the peak current is fixed,the entire system is naturally stable,while simplifying the chip architecture and have the advantages of fast response speed of conventional COFT control.In order to achieve low starting voltage and wide power supply voltage range,use BJT to design the voltage comparator,PTAT current source,negative temperature coefficient current source,and 400ns ONESHOT.The Boost converter chip described in this dissertation is based on the 0.35?m BCD process design.This dissertation designs the sub-blocks that make up the above-mentioned converter,and gives the simulation and verification results of the sub-module and proposed Boost converter with spectre.The simulation results show that the boost converter chip inductor current limit is 100mA,T_OFF is 400ns,the startup voltage is as low as 1V,the supply voltage range is as wide as 1V¹5V,the output voltage can reach up to 40V,and the on-chip integrated 40V power tube,When the load current is above5mA,the conversion efficiency can be maintained above 80%,up to 86.9%.