1,720,984 research outputs found
Fully digital hysteresis modulation with switching-time prediction
No full textThis paper proposes a digital hysteresis-modulation technique based on switching-time prediction. Sampling controlled variables several times within a switching period, it ensures a dynamic performance comparable to that obtainable with analog hysteresis modulation. Compared to conventional digital hysteresis modulation, it avoids frequency jitter since it predicts switching transitions. Compared to hysteresis modulation based on the detection of the zero crossing of current errors, it avoids external analog circuits. Compared to pulsewidth-modulation (PWM) techniques, it ensures faster dynamic response. These advantages are obtained at the expense of increased signal-processing requirements and of control complexity. Switching-frequency stabilization and synchronization with an external clock can be obtained extending the techniques proposed for analog hysteresis modulations. The proposed predictive algorithm does not require knowledge of load parameters and only a rough estimation of the inductor value, which can be easily self-adjusted. The proposed solution is suited for high-performance current (or sliding-mode) control where the digital hardware has enough computational power to allow multiple samples within a switching period. The proposed modulation technique has been applied to a sliding-mode control of a single-phase uninterruptible power supply (UPS). Experimental results confirm the effectiveness of the proposed approach
Digital Control of single-phase Power Factor Preregulator suitable for Smart-Power Integration
No full textThis paper proposes a fully digital control of boost power factor preregulators (PFPs) with input voltage estimation that is suitable for smart-power integration. The proposed solution features a minimum pin count by avoiding direct sensing of the input voltage for the construction of the internal current reference signal and by sensing the output voltage through a direct sampling of the voltage across the power switch during its off interval at the line voltage peak. The control algorithm requires the estimation of the rectified input voltage, that is simply done by exploiting the integral part of the current loop PI regulator, and a PLL (phase-looked-loop) synchronization with the estimated line frequency for sampling the output voltage and rejecting the low-frequency output voltage ripple. The provisions needed to ensure correct output voltage sensing, even during transient and light-load conditions, are also discussed. Experimental results on a single-phase boost PFP show the properties of the proposed approach
Digital Control of single-phase Power Factor Preregulator based on current and voltage sensing at switch terminals
No full textThis paper proposes a fully digital control of boost power factor preregulators (PFPs) with input voltage estimation that is suitable for smart-power integration. The proposed solution features a minimum pin count by avoiding input voltage sensing for the generation of the internal current reference and by sensing the output voltage through the direct sampling of the voltage across the power switch during its off interval at the line voltage peak. The control algorithm requires the estimation of the rectified input voltage, that is simply done by exploiting the integral part of the current loop proportional–integral regulator, and a phase-looked-loop (PLL) synchronization with the estimated line frequency for sampling the output voltage and rejecting the
low-frequency output voltage ripple. The provisions needed to
ensure correct output voltage sensing, even during transient and
light-load conditions, are also discussed. Experimental results on
a single-phase boost PFP show the properties of the proposed
approach
“Transmitting apparatus of digital signals on a supply line of electronic devices and corresponding method ”
No full textA power converter having a noise component and a modulator configured to vary a frequency of the noise component of the power converter on the basis of a digital signal to be transmitted
Transmitting apparatus of digital signals on a supply line of electronics devices and corresponding method
No full textA power converter having a noise component and a modulator configured to vary a frequency of the noise component of the power converter on the basis of a digital signal to be transmitted
Prediction of Limit-Cycles Oscillations in Digitally Controlled DC-DC Converters using Statistical Approach
No full textFPGA control of SIMO dc-dc converters using load current estimation
No full textThis paper investigates a digital control for non-isolated single-inductor multiple output (SIMO) step-down DC-DC converters using load current estimation. The proposed control architecture has been applied for SIMO converters operating in continuous conduction mode (CCM), where there is a cross-regulation issue between output voltages. The adopted control includes a separate regulation of the common-mode and the generalised differential-mode output voltages for the input half-bridge and for the output switches respectively. Due to the differential-mode control loop dependence on the load current, an inductor current estimation is used to perform a variable gain for the differential-mode regulation. Moreover, a non-linear evaluation of the common-mode voltage have been investigated in order to improve the system dynamic response at different load conditions. Even if aimed to an integrated solution, experimental investigation has been performed using discrete components, implementing the digital control in a field programmable gate array (FPGA). Simulation results on a three output converter and experimental results on dual output converter (Vin=2.5÷5 V, Vo1=Vo2=0.9÷5 V, Io1=Io2=0÷0.6 A) confirm the proposed analysis
Analysis of multi-sampled current control for active filters
No full textThis paper investigates the multi-sampling
techniques applied to the current control in active power filter
applications. In active power filter applications with digital
control, the main bandwidth limitation derives from A/D
conversion time, calculation delays and the sample-and-hold
effect for the Digital-Pulse-Width Modulation (DPWM). Using
Field Programmable Gate Arrays (FPGAs) and fast A/D
converters for the control implementation, it is possible to
make the former two negligible with respect to the switching
period. Thus, the overall phase lag is dominated by the
DPWM, which can be strongly reduced by multiple sampling
approach, thus breaking bandwidth limitation of singlesampled
solutions. Moreover, as the multi-sampling approach
triggers nonlinear behaviors that can negatively impact the
filter compensating capabilities, a solution is proposed, based
on a simple digital filter, that linearizes the system behavior
and does not waste the multi-sampling phase boost property.
Simulation and experimental results on a 10 kVA prototype
confirm the theoretical expectations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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