Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Multilevel inverters: a survey of topologies, controls, and applications

Linear PA Design. Conventional High-Efficiency Amplifier Modes. Class AB PAs at GHz Frequencies. Practical Design of Class AB PAs. Overdrive and the Class F Mode. Switching Mode Amplifiers for RF Applications. Switching PA Modes at GHz Frequencies. Signals, Modulation Systems, and PA Nonlinearities. Efficiency Enhancement Techniques. Power Amplifier Bias Circuit Design. Power Amplifier Architecture. PA Linearization Techniques.

RF Power Amplifiers for Wireless Communications

The generation of RF/microwave power is required not only in wireless communications, but also in applications such as jamming, imaging, RF heating, and miniature dc/dc converters. Each application has its own unique requirements for frequency, bandwidth, load, power, efficiency, linearity, and cost. RF power is generated by a wide variety of techniques, implementations, and active devices. Power amplifiers are incorporated into transmitters in a similarly wide variety of architectures, including linear, Kalm, envelope tracking, outphasing, and Doherty. Linearity can be improved through techniques such as feedback, feedforward, and predistortion.

Power amplifiers and transmitters for RF and microwave

A control circuit of a surgical device is disclosed. The control circuit includes a first circuit portion coupled to at least one switch operable between an open state and a closed state. The first circuit portion communicates with a surgical generator over a conductor pair to receive a control signal to determine a state of the at least one switch.

Surgical generator for ultrasonic and electrosurgical devices

The class E tuned power amplifier consists of a load network and a single transistor that is operated as a switch at the carrier frequency of the output signal. The most simple type of load network consists of a capacitor shunting the transistor and a series-tuned output circuit, which may have a residual reactance. Circuit operation is determined by the transistor when it is on, and by the transient response of the load network when the transistor is off. The basic equations governing amplifier operation are derived using Fourier series techniques and a high- Q assumption. These equations are then used to determine component values for optimum operation at an efficiency of 100 percent. Other combinations of component values and duty cycles which result in 100-percent efficiency are also determined. The harmonic structure of the collector voltage waveform is analyzed and related amplifier configurations are discussed. While this analysis is directed toward the design of high-efficiency power amplifiers, it also provides insight into the operation of modern solid-state VHF-UHF tuned power amplifiers.

Idealized operation of the class E tuned power amplifier

Switch-peak-current commanding current-mode control produces asymmetrical operation when used in capacitively coupled symmetrical dc/dc converters. This paper discusses the causes and effects of asymmetry, gives an analytical model, and proposes a negative-feedback corrector to eliminate the asymmetry. Test results on a 150-W off-line halfbridge converter prove the effectiveness of the recommended solution.

http://ieeexplore.ieee.org/iel7/7067112/7067113/07067160.pdf

How to use current-mode control with capacitively coupled half-bridge converters

Chapter 3 describes the different Class-F techniques using lumped and transmission-line elements including a quarterwave transmission line. Highly efficient Class-F operation of the power amplifier can be obtained by applying biharmonic or polyharmonic modes when an additional single-resonant or multi-resonant circuit tuned to the odd harmonics of the fundamental frequency is added to the load network. An infinite number of odd-harmonic resonators results in an idealized Class-F mode with a square voltage waveform and a half-sinusoidal current waveform at the device output terminal providing ideally 100% collector (or drain) efficiency. The Class-F mode with a quarterwave transmission line resulting in ideal voltage and current waveforms is analyzed for shunt and series connections of the quarterwave line. In Class-F power amplifiers analyzed in the frequency domain, the fundamental and harmonic load impedances are optimized by short-circuit termination and open-circuit peaking to control the voltage and current waveforms at the device output to obtain maximum efficiency. The effects of the transistor saturation resistance and parasitic shunt capacitance are described. Design examples and practical RF and microwave Class-F power amplifiers are given and discussed.

Class-F Power Amplifiers

Publisher Summary
The highly efficient operation of power amplifier can be obtained by applying biharmonic or polyharmonic modes when an additional single-resonant or multi-resonant circuit tuned to the odd harmonics of the fundamental frequency is added into the load network. An infinite number of odd-harmonic resonators result in an idealized Class-F mode with a square voltage waveform and a half-sinusoidal current waveform at the device output terminal. In Class-F power amplifiers analyzed in frequency domain, the fundamental and harmonic load impedances are optimized by short-circuit termination and open-circuit peaking to control the voltage and current waveforms at the device output to obtain maximum efficiency. This chapter analyzes different Class-F techniques using lumped and transmission-line elements, including a quarter-wave transmission line. The effect of the saturation resistance and parasitic shunt capacitance is demonstrated in the chapter. The design examples and practical radio frequency (RF) and microwave Class-F power amplifiers are discussed in the chapter.

Chapter 3 – Class-F Power Amplifiers

Publisher Summary
This chapter presents the different configurations of Class-D power amplifiers—the increased efficiency of which is a result of employing the active device as switches. The switched-mode power amplifiers with resistive load of different configurations, which can be considered driver power amplifiers, are discussed. The current-switching and voltage-switching configurations based on complementary and transformer-coupled topologies are analyzed. The effect of the saturation resistance, rectangular and sinusoidal driving signals, finite transition time, and parasitic shunt capacitance and series inductance is demonstrated. The practical design examples of voltage-switching and current-switching Class-D power amplifiers intended to operate at high frequencies and microwaves are described in the chapter.

Chapter 2 – Class-D Power Amplifiers

Class-E dc/dc converters can operate at high switching frequencies with very low switching power losses. Using commercially available power transistors and diodes, Class-E converters can operate at switching frequencies in the low-MHz range, with efficiencies of about 85%. Previous papers dealt with the circuit parameter values needed to obtain high-efficiency operation and output-voltage regulation, and with the static control characteristic of the Class-E dc/dc converter cell. Here we extend the analysis to include the dynamic control characteristics and further information about the static characteristics. The theoretical predictions are verified by experimental measurements on a 40-watt 1.5-MHz converter.

Nathan O. Sokal

Papers

How to use current-mode control with capacitively coupled half-bridge converters

Class-F Power Amplifiers

Chapter 3 – Class-F Power Amplifiers

Chapter 2 – Class-D Power Amplifiers

Small-signal dynamic analysis of regulated Class-E DC/DC converters