一种频率可偏移的峰值电流控制电路设计

Design of a peak current control circuit with frequency shift

为了降低直流/直流(Direct Current/Direct Current,DC/DC)变换器在短路时电感电流平均值,设计了一种频率可偏移峰值电流控制电路。利用比较器检测输出电压变化,通过数字控制电路产生不同频率脉冲信号和控制信号,以控制斜坡补偿电路的斜率和频率,并提高系统稳定性和带载能力。当出现将输出电压被拉低的过流或短路情况时,通过数字控制产生的频移时钟来增加电感电流下降时间,从而降低变换器负载电流。基于0.25μm双极、互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)和双扩散金属氧化物半导体(Double Diffused Metal Oxide Semiconductor,DMOS)工艺设计电路并仿真,结果表明,在输入电压为12 V,输出电压为9 V的大占空比应用时,输出电压纹波为3.4 mV。当输出短路时,电感电流峰值为6 A,平均电流为2.32 A。设计电路在输出短路时的电感电流平均值较低。

In order to reduce the short circuit average current of an inductor in a direct current/direct current(DC/DC)converter,a peak current control circuit with frequency shift is designed.The comparator detects the changes of the output voltage,the digital control circuit generates pulse signals and control signals of different frequencies,and controls the slope and frequency of the slope compensation circuit,so as to improve the system stability and load capacity.When there is an over-current or short-circuit condition that pulls the output voltage down,a frequency shift clock is generated by digital logic to increase the inductor current decreasing time and reduce the converter load current.The circuit is designed based on 0.25μm bipolar,complementary metal oxide semiconductor(CMOS)and double diffused metal oxide semiconductor(DMOS)technology.The simulation result shows that when the input voltage is 12 V and the output voltage is 9 V,the output voltage ripple is 3.4 mV.When the output is short circuited,the peak inductor current is 6 A and the average current is 2.32 A.The average value of inductance current of the designed circuit is low when the output is short circuited.