一种采用SCOVP技术的高频率稳定度Buck变换器

提出了一种采用单周期输出电压预测(SCOVP)技术的自适应导通时间(AOT)控制Buck变换器。该变换器可以在输入输出电压及负载变化时实现频率恒定,并可设置外部电阻使Buck变换器准确工作在高开关频率下。首先分析了传统AOT控制Buck变换器的开关频率产生漂移的原因,并提出了一种采用SCOVP技术的单脉冲计时器(OST)电路。其次通过单周期占空比预测输出电压信息,并根据预测的输出电压和负载电流补偿T_ON时间,实现了Buck的频率稳定。该变换器采用0.18μm BCD工艺进行电路设计。仿真结果表明,在2 MHz开关频率下,负载电流从1 A到5 A变化时,Buck变换器的最大频率变化Δf_SW仅13 kHz,负载平均频率变化Δf_SW/ΔILoad为3.24 kHz/A。同时,变换器频率设置准确度从88%提升到99.35%。

A High Frequency Stability Buck Converter with Single Cycle Output Voltage Prediction Technology

An AOT-control buck converter with Single Cycle Output Voltage Prediction(SCOVP) technique was proposed. Quasi-constant frequency operation with the input/output voltage and load variation was achieved. Furthermore, the switching frequency was set by off-chip resistor with improved accuracy. The switching frequency variation of the traditional AOT-controlled buck converter was analyzed, and an One-Shot Timer(OST) circuit with SCOVP technique was adopted. By predicting the output voltage through single duty cycle and load current, the operational frequency was stabilized. The converter was designed with in a 0.18 μm BCD process. Simulation results showed that only 13 kHz variation was realized with load current from 1 A to 5 A when the switching frequency was set as 2 MHz. Meanwhile, the switching frequency accuracy was enhanced from 88% to 99.35% with proposed SCOVP technique.