Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm/sup 2/ of silicon area in a standard 0.5 /spl mu/ digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz.

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High-frequency digital PWM controller IC for DC-DC converters

This paper explores predictive digital current programmed control for valley, peak or average current. The control laws are derived for the three basic converters: buck, boost, and buck-boost. It is found that for each variable of interest (valley, peak or average current) there is a choice of the appropriate pulse-width modulation method to achieve predictive digital current control without oscillation problems. The proposed digital control techniques can be used in a range of power conversion applications, including rectifiers with power factor correction (PFC). Very low current distortion meeting strict avionics requirements (400-800 Hz line frequency) is experimentally demonstrated on a digitally controlled boost PFC employing predictive average current programmed control.

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Predictive digital current programmed control

EMG and EOG artifacts in brain computer interface systems: A survey

A control system and method for simultaneously regulating the operation of a plurality of different types of switching power converters. The system utilizes in regulating the power converters sampled data and nonlinear feedback control loops.

Power converter circuitry and method

In this paper, a digital control technique based on a two-loop predictive dead-beat control concept is developed for switchmode DC/DC power supply applications. The dead-beat control law is derived directly from the switching characteristic of the converter. With the inductor current reaching the reference in a single control period, the proposed technique results in much improved control performance. In addition, the design procedure is simple and does not require extensive tuning. Furthermore, the computational resources required for the calculation of the control algorithm are reduced by half as compared to a conventional digitized PI structure. Both experimental and simulated results are provided to validate the proposed concept.

High performance predictive dead-beat digital controller for DC power supplies

This paper reports on a novel method for quantifying the cortical activity of a patient during general anesthesia as a surrogate measure of the patient's level of consciousness. The proposed technique is based on the analysis of a single-channel (frontal) electroencephalogram (EEG) signal using stationary wavelet transform (SWT). The wavelet coefficients calculated from the EEG are pooled into a statistical representation, which is then compared to two well-defined states: the awake state with normal EEG activity, and the isoelectric state with maximal cortical depression. The resulting index, referred to as the wavelet-based anesthetic value for central nervous system monitoring (WAV/sub CNS/), quantifies the depth of consciousness between these two extremes. To validate the proposed technique, we present a clinical study which explores the advantages of the WAV/sub CNS/ in comparison with the BIS monitor (Aspect Medical Systems, MA), currently a reference in consciousness monitoring. Results show that the WAV/sub CNS/ and BIS are well correlated (r=0.969) during periods of steady-state despite fundamental algorithmic differences. However, in terms of dynamic behavior, the WAV/sub CNS/ offers faster tracking of transitory changes at induction and emergence, with an average lead of 15-30 s. Furthermore, and conversely to the BIS, the WAV/sub CNS/ regains its preinduction baseline value when patients are responding to verbal command after emergence from anesthesia. We conclude that the proposed analysis technique is an attractive alternative to BIS monitoring. In addition, we show that the WAV/sub CNS/ dynamics can be modeled as a linear time invariant transfer function. This index is, therefore, well suited for use as a feedback sensor in advisory systems, closed-loop control schemes, and for the identification of the pharmacodynamic models of anesthetic drugs.

Quantifying cortical activity during general anesthesia using wavelet analysis

In this paper, a digital control technique based on a predictive dead-beat control concept is developed for switch-mode DC/DC power supply applications. As compared to a conventional digital controller, the proposed technique offers much improved control performance. In addition, the design procedure is simplified and the computational resources required for the calculation of the control algorithm are significantly reduced.

One of the major disadvantages of digital control is the limited control loop bandwidth due to the inherent time delay introduced by the zero-order-hold effect and the computational time delay. To alleviate this problem, two practical and straightforward predictive schemes based on linear extrapolation are proposed. With the proposed schemes, the computational time delay of the control loop is compensated and the control loop bandwidth is increased. It is shown that, using the proposed techniques, the control loop bandwidth can be increased up to two times that of the conventional digital control loop. Also, the computational overhead needed to implement these techniques is kept to the minimum. A lab prototype system of a 1 kV full bridge DC power supply was set up for the proof of concept. The prototype system operated at 10 kHz and was controlled by a TI TMS320F240 DSP (20-MHz 16-bit fixed-point). Simulation and experimental results prove the validity of the proposed techniques.

Time delay compensation of digital control for DC switchmode power supplies using prediction techniques

This paper investigates a wavelet based denoising of the electroencephalogram (EEG) signal to correct for the presence of the ocular artifact (OA). The. proposed technique is based on an over-complete wavelet expansion of the EEG as follows: i) a stationary wavelet transform (SWT) is applied to the corrupted EEG; ii) the thresholding of the coefficients in the lower frequency bands is performed; iii) the de-noised signal is reconstructed. This paper demonstrates the potential of the proposed technique for successful OA correction. The advantage over conventional methods is that there is no need for the recording of the electrooculogram (EOG) signal itself. The approach works both for eye blinks and eye movements. Hence, there is no need to discriminate between different artifacts. To allow for a proper comparison, the contaminated EEG signals as well as the corrected signals are presented together with their corresponding power spectra.

Stéphane Bibian

Papers

High performance predictive dead-beat digital controller for DC power supplies

Quantifying cortical activity during general anesthesia using wavelet analysis

High performance predictive dead-beat digital controller for DC power supplies

Time delay compensation of digital control for DC switchmode power supplies using prediction techniques

A wavelet based de-noising technique for ocular artifact correction of the electroencephalogram