【摘要】 首先讨论了DC-DC转换器的功率损耗源,根据重载情况下PWM控制效率高而轻载情况下PFM控制效率高的特点,提出了全负载下实现PWM/PFM自动切换以降低功耗、提高电源效率的控制方法.将相加模式PWM、跳周期和限流相结合的PFM整合于一个系统中,使整个系统高效协调地工作,并在较大的负载变化范围内均具有高效率的优点.系统采用0.5μm CMOS工艺实现,对系统的仿真结果表明,系统正常工作,成功实现了PWM/PFM的自动切换,性能指标达到了设计要求.更多还原

【Abstract】 The sources of power dissipation of DC-DC converter are discussed firstly.The control methods of DC-DC converter such as pulse width modulation(PWM),pulse frequency modulation(PFM) and PWM/PFM hybrid control are analyzed together with their power efficiency.The result shows that PWM is of high efficiency with heavy load and PFM is of high efficiency with light load.So PWM/PFM automatic switching DC-DC converter is proposed to lower the power loss and improve the power efficiency.The switching is according to the variation of the load.The proposed system integrates summing mode PWM,skipping cycles and current limited PFM into one system.It makes the whole system work efficiently over a wide load variation.The whole system are designed,simulated and debugged with 0.5 μm complementary metal-oxide-semiconductor transistor(CMOS) process.The simulation results show that the system can work properly,and PWM/PFM automatic switching is achieved successfully.Its performance meets the design requirements.更多还原