The Research And Design Of High-Efficiency Dual-Output Charge Pump

As the fast development of portable electronic devices,the integrations of all kinds of low-power electronic chips have been more and more intensive;and the power management systems are required to be improved accordingly.Nowadays,the most challenges that power management designers face are the requirements of low cost,low volume,low power,high power efficiency and fast transient response in the applications of battery-powered portable devices.According to the research background,a high-efficiency dual-output charge pump IC chip is developed.This chip is a switched-capacitor DC/DC converter, which uses capacitors as energy-transfer elements instead of bulk inductors;thus this charge pump features advantages of small volume,low cost and low EMI.With input voltage between 2.1V～3.6V,this charge pump can simultaneously generate a constant boost voltage output of 5.0V and a constant buck voltage output of 1.8V,which can serve as supply voltages of analog circuits,digital circuits and mixed-signal circuits in an electronic device.The charge pump uses shared switched-capacitor-array as power stage;thus the on-chip MOSFET power switches and external capacitors can serve both output channels to save chip area and external devices.The thesis provides investigations and research of charge pump concepts,control schemes and analysis methodologies;and it proposes an accurate modeling approach for analysis of dual-output charge pumps,which is verified by simulation results that the relative error is below 0.5%.With the guidance of this model,a novel automatic gain-hopping control approach is proposed,which combines high efficiency of lower gain and boost voltage of higher gain together,so that the charge pump achieves fast transient response.Moreover the charge pump utilizes a digital state machine as control kernel circuit.This controller enables two stable output voltages,improves overall driving capacity and brings possibility of more output channels.The chip is realized by TSMC 0.35μm CMOS technology.The chip die size is 2.75mm×2.25mm.Experimental results reveal that the charge pump can provide synchronous outputs of 5.0V and 1.8V with fast transient response and high efficiency which meets the specification.In gain-hopping conditions,the charge pump improves average conversion efficiency of 10%and even 20%maximum,which is consistent with design expectations.