Enric Vidal-Idiarte

Current-Mode Control of a Coupled-Inductor Buck–Boost DC–DC Switching Converter

This paper deepens in the study of the recently described coupled-inductor buck-boost converter. The output voltage of this dc-dc converter can be regulated above and/or below its input voltage with high efficiency and wide bandwidth. The control of the input and/or output nonpulsating converter currents is addressed in this paper. The small-signal control-to-input/output-current transfer functions in open-loop permits the design of the respective average current-mode controllers. The combination of the input- and output-current controllers with an additional output voltage limiter loop is proposed as a method to regulate one of the currents while limiting the maximum values of the other two variables. The theoretical analyses have been validated by means of simulations and also experimentally on a 48-V 800-W purpose built-prototype. In particular, the frequency response measurements that have been carried out for a representative set of the converter operating points are in good agreement with the simulations.

Two-Loop Digital Sliding Mode Control of DC–DC Power Converters Based on Predictive Interpolation

Digital implementation of sliding-mode current control applied to dc-dc switching converters is analyzed and developed in this paper. It is based on an interpolation predictive strategy that avoids problems associated to continuous sampling process of the controlled variable and minimizes quasi-sliding effects. In addition to inherent advantages of digital implementation, as programmability, flexibility, complex calculation capability and noise immunity, the proposed strategy maintains robustness and has similar behavior than analog sliding-mode current control implementations. In order to obtain output voltage regulation, an outer proportional-integral digital output voltage control loop is added. Simulated and experimental results in a boost converter are in good agreement with the theoretical predictions.

Using magnetic coupling to eliminate right half-plane zeros in boost converters

A dynamic analysis of the boost converter with an output filter reveals that magnetic coupling between inductors allows transfer of the zeros to the left half-plane of the control-to-output transfer function. Similar results requiring smaller magnetic components are obtained by combining magnetic coupling with damping of the output filter. The analysis is based on the application of the Routh-Hurtwitzs criterion to the numerator of the transfer function in order to derive the design conditions for the converter parameters. A design example illustrates the procedure, and experimental results verify the theoretical predictions. The application of these techniques will allow the design of high efficiency voltage boost-based regulators with dynamic behavior similar to buck-derived structures.

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The design of a two-loop control for nonminimum phase-switching converters is presented in this letter. An internal sliding-mode control loop forces the converter inductor current to follow the reference established by

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Control Strategy for Switching Converters in Sliding-Mode Current Control

control of the output voltage in an outer loop. Simulations of both time and frequency responses of the output voltage show a faster and more robust behavior than in the case of a conventional approach using a PI controller in the external loop. Experimental results are in good agreement with the simulation predictions.

Loss-Free Resistor-Based Power Factor Correction Using a Semi-Bridgeless Boost Rectifier in Sliding-Mode Control

In this paper, a loss-free resistor based on a semi-bridgeless rectifier is proposed for power factor correction applications. This particular bridgeless rectifier type is composed of two different boost cells which operate complementarily during each half-line cycle. In case of two unbalanced inductors, many control techniques can produce different inductor current ripples during each half-line cycle that can result in the addition of a dc component to the line current. This paper demonstrates that the application of sliding-mode control by means of hysteretic controllers results in a first-order stable system that can mitigate these harmful consequences due to its capability to ensure the symmetry of the line input current waveform for both positive and negative half-line cycles. Thus, the system does not absorb any dc component from the grid and it is also capable of reducing dramatically the amplitude of the third harmonic. The theoretical predictions have been validated by means of PSIM simulations and experimentally on a prototype of 1 kW which has been controlled using only one sliding control surface.

Interleaved Digital Power Factor Correction Based on the Sliding-Mode Approach

This study describes a digitally controlled power factor correction (PFC) system based on two interleaved boost converters operating with pulsewidth modulation (PWM). Both converters are independently controlled by an inner control loop based on a discrete-time sliding-mode (SM) approach that imposes loss-free resistor (LFR) behavior on each cell. The switching surface implements an average current-mode controller so that the power factor (PF) is high. The SM-based digital controller is designed to operate at a constant switching frequency so that the interleaving technique, which is recommended for ac-dc power conversion systems higher than 1 kW, can be readily applied. An outer loop regulates the output voltage by means of a discrete-time proportional-integral (PI) compensator directly obtained from a discrete-time small-signal model of the ideal sliding dynamics. The control law proposed has been validated using numerical simulations and experimental results in a 2-kW prototype.

Self-oscillating interleaved boost regulator with loss free resistor characteristic

This paper presents an interleaved boost converter which reduces the pulsating nature of the output current and causes the switching ripple in the output voltage to decrease drastically. For a duty ratio of 50%, the circuit acts as a voltage doubler and its dc input impedance has a resistive characteristic. A sliding-mode controller without external reference guarantees stable and robust behavior for the switching regulator.

TSK-fuzzy controller design for a PWM boost DC-DC switching regulator operating at different steady state output voltages

A Takagi-Sugeno-Kang (TSK) fuzzy controller design for a PWM boost DC-DC switching regulator operating at different steady-state voltages is presented. On the other hand, the controller assigns different linear control laws according to the steady-state voltage value and limits their application to the small-signal perturbations. On the other hand the controller assures a proper start-up to reach the desired steady-state voltage by means of properly saturating the PWM according to the sliding-mode control principles. As a result, both equalized small-signal behaviour and a controlled start-up are achieved for different steady-state voltages, thus enhancing the regulator features. Simulation results for a current-controlled boost regulator operating at different steady-state voltages are presented to validate the approach.