Design Of Buck DC/DC Convertor Based On Adjustable Analog Feedback

At present, there is a rapid increasing market demanding for portable equipments, such as mobiles, digital camera, MP3, MP4, etc, which requires power management chip, especially DC/DC converter.In this paper, a buck DC/DC converter based on adjustable analog- feedback has been designed. On the base of the structure of conventional PWM voltage control mode DC/DC converter, we improve the PWM controller as adding another analog-feedback loop. The loop includes ramp generator and error amplifier through the phase detector and charge pump. And a new structure has been proposed: the sum-comparator has been substituted the ramp generator and error amplifier and the voltage-current circuit change the error voltage to the charge current of the capacitance. The feedback loop sampling the output voltage to control the charge time of the capacitance in ramp generator which reflects the duty circle of PWM signals. These improvements improve the stability of the DC/DC converter and increase the characteristic of the converter respond to output voltage. Also these improvements make the design structure simple and minish the area of the layout. The range of the input voltage of the converter is 3.3V-5.0V,and the output voltage includes two parts, one for the analog circuits and another for the digital circuits. The maximal output currents are 120mA and 300mA.Both are adjustable at the range of 1.53V-2.05V.The switch frequency is 1 MHz. The simulation results indicate that the maximal efficiency is 94.79%.The integrated simulation results prove all the design results are correct. The layout of the converter has been achieved using UMC 0.18um technology and tape-out.