Research And Design Of High Efficiency Current-limited Power-distribution Switch

With the development of power management technology and energy-saving technologies,most portable devices require a power-distribution switch.The work of the thesis starting around low power consumption,high efficiency,low cost and completed protection function,from the system structure definition,circuit design,pre-simulation verification,layout and post-simulation verification,a high efficiency current-limited power-distribution switch chip is proposed in this paper.First,this paper studies the principle and circuit structure of the conventional distribution switch.Then,aiming at the disadvantages of the large static current,low efficiency and no current-limited function of the conventional switch,combined with the design requirements of switching path and project requirements,a high efficiency current-limited power-distribution switch circuit is designed.The chip can improve the efficiency of the system by using the current-sense circuit with SENSEFET structure,and monitors the output current in real-time through the current-sense circuit to limit the maximum output current to prevent the breakdown of the power supply system caused by overload or short-circuit condition(users can program two independent current-limited thresholds between 500 mA and 2.5A via two external resistors).In addition,the chip also has overcurrent protection: to prevent the inrush current caused by transient overload;over-temperature protection: to prevent the internal temperature of the chip is too high to damage the chip;and under-voltage lockout function: to prevent the power supply voltage is too low to make the circuit abnormal.The design is based on 5V BCD process.The results show that the operating current of the circuit is 200?A.When the output current is 2A,the on-state resistance is only 32m?,and the efficiency is as high as 98.72%.The fast overcurrent response time is 1.5?s,which can turn off the power-distribution switch before the inrush current caused by transient overload.In this paper,there are two over-temperature protection mechanisms: the measured temperature thresholds are 135? and 155? respectively for the current-limited mode and non-current-limited mode.In addition,when the power supply voltage is lower than 4.05 V,the chip will enter the under-voltage lockout state.