Dynamic Reference Current Control Strategy Of Buck Converter Operating In Pseudo Continuous Conduction Mode

With the rapid development of power electronics, modem digital devices such as phones and laptops put a increasingly demand on its voltage regulator module, which requires better steady and dynamic performance of switching converter. Switching converters in continuous conduction mode (CCM) are usually applied in high-power applications, and their dynamic performance is comparatively poor. Switching converters in discontinuous conduction mode (DCM) exhibit better dynamic performance, but the current ripple and electro-magnetic interference (EMI) noise are usually worse than that of CCM converters.Boost converter operating in pseudo continuous conduction mode (PCCM) was proposed to solve the right-half-plane zero problem of CCM boost converter. PCCM converter is improved of good dynamic performance and easier approach to design the closed loop control. However, PCCM converter hasn’t been widely used because of its poor efficiency.Using state space averaging method, the mathematical mode! of PCCM buck converter is established in this paper. Relationships of circuit parameters and their influences on conversion efficiency are exhibited by mathematical expression. The mathematical model of PCCM buck converter provides a theoretical basis for the design and choice of dynamic reference current (DRC) control signal.One DRC control strategy is put forward and applied in PCCM buck converter in order to solve the poor efficiency of traditional PCCM buck converter with constant reference current (CRC) control under light load. Compared with CRC control, the DRC control reduces the reference current signal under the light load condition of the converter, reduces the duration time and the loss during the freewheeling stage, which expands load operating range, increased conversion efficiency under light load and improves the dynamic performance of PCCM converter. The theoretical analysis is verified by both simulation and experimental results.DRC control and V2 control are combined in PCCM buck converter, which is denoted as V2-DRC control. V2 control improves dynamic performance and DRC control increases light-load efficiency and load operating range. Compared with CRC control, DRC control slightly improves the dynamic performance of V2 control PCCM buck converter. The stability of V2 controlled PCCM buck converter is analyzed and its slope compensation is also discussed. Simulations and experiments are conducted to support theoretical analysis.