PWM/PSM双模式高压异步整流BUCK电路

High voltage PWM/PSM dual-mode asynchronous BUCK converter

为了在全负载范围内取得高转换效率,提出一种根据占空比来自动实现模式跳转的脉冲宽度调制(PWM)/跨脉冲调制(PSM)双模式的低功耗、高压直流电压转换电路.它的输入电压为3～24V,输出电压为2.5～(VIN-0.5)V.当负载电流较大时,芯片采用开关频率为1MHz的PWM工作模式;当负载电流减小时,采用开关频率降低的PSM模式,从而保证了在全负载电流变化范围内的高转换效率.PWM到PSM模式的跳转采用简单逻辑及最小占空比电路实现,达到了模式的自动转换.电路采用CSMC公司的0.5μm 40V高压混合信号模型设计并完成流片加工.测试结果表明,在5V的输出下,当输入电压到达最大值24V时,芯片保持了55%以上的转换效率.芯片在2种模式间可以实现平稳过渡,具有良好的负载电流调整特性.

A BUCK converter with high input/output voltage and low power consumption,consisting of two working modes of pulse width modulation（PWM） and pulse skipping modulation（PSM）,was proposed in order to obtain high conversion efficiency in the whole load range.The converter automatically skips from PWM to PSM mode by detecting the duty cycle of switch pulse.The input voltage of the converter ranges from 3 V to 24 V,and the output voltage ranges from 2.5 V to（VI-0.5） V.The converter works in PWM-mode at a switching frequency of 1 MHz when the load current is large,and operates in PSM-mode with a reduced switching frequency if the load current is low,which makes a high efficiency in the whole load current range.The PWM/PSM dual-mode converter switches from PWM to PSM mode by limiting the minimum duty cycle,and the mode control circuit was easily realized by some logic gate and one-shot circuit.The chip was implemented by using the CSMC 0.5 μm 40 V mixed-signal process.Experimental results indicate that the efficiency is still higher than 55% when the output voltage is 5 V,even when the input voltage is 24 V which is the highest input voltage of this chip.The chip can smoothly alter mode and display good load regulation.