Research On High-Efficiency On-Chip Power Conversion Technology Based On Switched-Capacitor

With the advancement of integrated circuit design technology and manufacturing technology,traditional discrete power chips have been difficult to meet the needs of some applications.First,with the continuous development of So C technology,the power system is expected to be integrated with other circuit modules,so as to reduce the volume of the system and increase its power density.Second,with the reduction of the feature size of the integrated circuit process,the power I/O will occupy more I/O resources and crowd out the signal I/O,resulting in a "power wall" phenomenon.Therefore,it is an inevitable trend to complete power conversion on-chip.Third,the rise of So C system complexity and the wide application of multi-voltage domain technology,the use of discrete off-chip power supply means that a lot of PCB area will be increased.Using an on-chip power supply will reduce a lot of hardware cost and debugging cost.Switched Capacitor Power Converter(SCPC)has the advantages of easy integration,high power conversion efficiency,low electromagnetic interference,support for buckboost and negative voltage,and high-power density.Therefore,this dissertation takes SCPC as the research object,and conducts an in-depth study with the power conversion efficiency as the key indicator.It aims to realize an efficient and general SCPC highefficiency control strategy,and solve key scientific issues such as the static model of SCPC and the mechanism of efficiency enhancement technology.This dissertation studies the loss mechanism and static model of SCPC,proposes a design method with optimal power conversion efficiency,and proposes an optimized design scheme for key submodules.On these bases,this dissertation designs a SCPC chip with high efficiency.The following innovations have been achieved:1.A SCPC static model is proposed.Aiming at the problems of topology versatility,accuracy and analytical complexity in the existing static models,the equivalent output resistance model and the ripple model,and the difficulty of unifying the two models,the SCPC static model based on loss voltage analysis is proposed.The equivalent output resistance model is based on the basic charge transfer mechanism in SCPC,which is common to all SCPC topologies and does not need to assume infinite output capacitance.On the other hand,this dissertation establishes an output voltage ripple model based on the proportional current approximation method.Compared with traditional approximation methods,this model considers the charge transfer from flying capacitor to output capacitor during phase switching,so it is more accurate at medium and high switching frequencies.Experiments show that the error between the model value and the actual equivalent output resistance is within 15%,and the accuracy of the model is higher than that of the classical model at the intermediate frequency switching frequency,up to 20%.The model can accurately predict the output voltage ripple,which is much better than traditional ripple models in the middle and high switching frequency range.2.A driving loss optimization technique based on the driving voltage modulation mode is proposed.This technology replaces the switch size adjustment technology with the drive voltage modulation and floating voltage drive scheme,which can realize continuous switch on-resistance adjustment,and then achieve high-precision maximum efficiency point tracking.This technology utilizes load current sampling and a currentcontrolled oscillator to realize adaptive adjustment of switching frequency with the load circuit.Finally,a dual-loop control that simultaneously adjusts the driving voltage and switching frequency is realized,which improves the power conversion efficiency of SCPC.This scheme is applied to a two-phase voltage doubler.Simulation results show that the proposed drive loss optimization technique can increase efficiency by 18.9% and reduce ripple by 97% at very light loads compared to conventional PFM control.3.A minimum driving loss point tracking technique is proposed.This technology can adjust the switching frequency,switch size and driving voltage to the theoretical optimum in real time according to the load,so this method theoretically approaches the maximum efficiency of SCPC.The scheme has good topology compatibility and can realize the minimum driving loss point tracking of any topological structure at the same time,especially suitable for reconfigurable SCPC.A digital low-dropout linear regulator(LDO)and multiplexers are innovatively used as the control module to adjust the parameters of the SCPC,and the adaptive adjustment of "zero dynamic power consumption" and "zero response time" is realized in this dissertation.The scheme is applied to a multiphase SCPC with four voltage convertion ratios.The experimental results show that compared with the traditional PFM control mode,the minimum driving loss point tracking technology proposed in this dissertation can reduce the driving loss by 27% and increase the power conversion efficiency by 7.8%.4.A floating voltage drive circuit suitable for multi-phase interleaving control technology is proposed.Aiming at the situation of too many switches in SCPC controlled by multi-phase interleaving,an interleaving bootstrap technique is proposed.This technique periodically utilizes specific cells in a multiphase interleaved SCPC to provide bootstrap drive for other cells.The driving circuit can realize floating voltage driving of all power switches.Compared with the traditional floating voltage driving scheme,the hardware overhead of the proposed driving circuit is independent of the number of phases,and the driving voltage can be detected conveniently for accurate control.For N-phase interleaving SCPC,the number of switches and bootstrap capacitors in the proposed driving circuit is only 2/N times that of the traditional scheme.in the case of 8-phase interleaving,the number of components in the driving circuit can be saved by 75%.