摘要
设计了一种基于自适应开启时间(adaptive on-time,AOT)控制的Buck型DC-DC控制器电路,利用输入电压前馈和输出电压反馈技术来获得开启时间,并提出了一种充电电流补偿和充电时间超前电路,校正了开启时间的线性度.AOT控制保证了转换器在无需内部振荡器的条件下,工作于固定频率脉冲宽度调制模式,并改善了输出电压的纹波特性.AOT控制使系统在负载阶跃时能够连续开启最小关断时间的开关周期或连续关断,从而快速调节电感电流,极大地提高了系统的瞬态响应速度.自动跳跃式脉冲频率调制模式,有效地改善了轻负载下的转换效率.芯片采用UMC0.6μm BCD工艺投片验证,并出了详细的测试结果.
A buck DC-DC controller based on adaptive on-time （AOT） control is presented in this paper. The adaptive on-time is achieved by input voltage feedforward and output voltage feedback,and the linearity of the on-time is corrected by the novel charging current compensation and charging time ahead circuits. The designed controller can operate at fixed frequency without an internal oscillator,which has better output voltage ripple. Simultaneously, the AOT controller will operate at the minimum off-time cycle or continuous shutoff when load steps,which greatly enhances the transient response speed of the system. In addition, the auto-skip PFM （pulse frequency modulation） mode boosts conversion efficiency during light load operation. The controller has been successfully fabricated with a UMC 0.6μm BCD process,and the detailed experimental results are shown at the end of the article.
