access icon free Analysing the effects due to discontinuous output-voltage ripple in a digitally current-mode controlled boost converter

Digital implementation of current-mode control (CMC) considers the outer voltage-loop in the digital domain, whereas the inner current-loop is kept either in the analogue domain in mixed-signal CMC (MCMC) or in the digital domain in fully digital CMC (DCMC). Under finite voltage-loop sampling, this study reports that the selection of sampling point can completely change the stability status of a boost converter with non-minimum phase behaviour, particularly in the presence of the effective-series-resistance of the output capacitor. A discrete-time framework is proposed for fast-scale stability analysis in a boost converter, operating under continuous conduction mode. Further, discrete-time small-signal models are derived and design guidelines are proposed for both MCMC and DCMC architectures with enhanced stability for fast transient performance. Keeping in mind software-controlled DCMC, a considerably large sampling delay is considered, and its effect on the performance and stability is discussed. A boost converter prototype is tested and various DCMC schemes along the proposed design techniques are implemented using a field-programmable-gate-array device.

Inspec keywords: digital control; electric current control; sampling methods; field programmable gate arrays; control system synthesis; discrete time systems; capacitors; power convertors

Other keywords: discrete-time small-signal models; fast transient performance; nonminimum phase behaviour; finite voltage-loop sampling; field-programmable-gate-array device; discontinuous output-voltage ripple; FPGA; DCMC architectures; sampling point selection; continuous conduction mode; design guidelines; mixed-signal CMC; software-controlled DCMC; effective-series-resistance; boost converter prototype; fast-scale stability analysis; MCMC architectures; output capacitor; analogue domain; sampling delay; stability status; outer voltage-loop; digitally current-mode controlled boost converter

Subjects: Capacitors; Other topics in statistics; Other topics in statistics; Current control; Logic circuits; Power electronics, supply and supervisory circuits; Control system analysis and synthesis methods; Discrete control systems

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