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

The new class of amplifiers described is based on a load network synthesized to have a transient response which maximizes power efficiency even if the active device switching times are substantial fractions of the a.c. cycle. The new class of amplifiers, named `Class E,' is defined and is illustrated by a detailed description and a set of design equations for one simple member of the class. For that circuit the authors measured 96 percent transistor efficiency at 3.9 MHz at 26-W output from a pair of Motorola 2N3735 TO-5 transistors. Advantages of Class E are unusually high efficiency, a priori designability, large reduction in second-breakdown stress, low sensitivity to active-device characteristics, and potential for high-efficiency operation at higher frequencies than previously published Class-D circuits.

Class E-A new class of high-efficiency tuned single-ended switching power amplifiers

The previous literature on tuned power amplifiers has not made clear the fundamental differences between amplifiers in which the output device acts 1) as a current source, or 2) as a switch. Previous circuits have often operated in contradiction to their design assumptions, resulting in the need for “cut-and-try” design. The new class of amplifiers deseribed here is based on a load network synthesized to hWe a transient response which maximizes power efficiency even if the active device switching times are substantial fractions of the ac cycle. The new class of amplifiers, named “Class E; 1 is defined and is iflustnated by a detailed description and a set of design equations for one simple member of the class. For that circuit the authors measured 96 percent transistor efficiency at 3.9 MHr at 26-W output from a pair of Motorola 2N3735 TO-5 transistors. Advantages of Class E are unusually high efficiency, a priori designability, large reduction in second-breakdown stress, low sensitivityy to activedevice characteristics, and potential for high-efficiency operation at higher frequencies than pI eviously published Class-D circuits. Harmonic output and power gain are comparable to those of conventional amplifiers.

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Class of High-Efficiency Tuned Switching Power Amplifiers

A power amplifying and signal processing system for modulated carrier signals separately processes the amplitude component of the system input signal and the component of frequency or phase or both frequency and phase, and later recombines the separately processed components to provide an output signal. The amplitude and phase transfer functions of the system can be accurately controlled. The input signal is fed to a power amplifier whose output provides the output for the system. The input and output signals of the system are fed by separate paths to a comparator which compares those signals and emits an error signal to a controller. The controller regulates the amplitude and phase, or both, of the power amplifier''s output to null the error signal. One or both of the signal paths to the comparator may have in it a non-linear function generator which acts upon the signal fed by that path to the comparator. The system may also have a frequency translator and phase shifter interposed between the system input terminal and the power amplifier''s input to shift the frequency or phase or both of the signal applied to the power amplifier''s input.

Amplifying and processing apparatus for modulated carrier signals

Near-optimum dynamic regulation of a dc-dc converter is obtained by adding feed-forward of output current and input voltage to a current-mode controller. The results are a) near zero output impedance and audio susceptibility, from dc to nearly the switching frequency, b) much reduced magnitude, duration, and energy content of the output-voltage transient after a transient change of output current or input voltage, and c) smaller size and lower cost for the output filter capacitor. Feed-forward is applicable to both forward and flyback types of converters and to all types of current-mode control. The cost of feed-forward for a forward-type converter is a low-power resistor and a current sensor; a flyback-type converter needs also an analog multiplier-divider integrated circuit (IC). A description is given of the control loop, conditions to achieve extremely good transient response, calculation of the peak deviation of the output voltage for a step load change, practical methods for current feed-forward, and experimental results. The theoretical predictions are in excellent agreement with the experimental results. In the experiments, adding output-current feed-forward reduced the transient deviations of output voltage by factors of 6.7 in magnitude, 50 in duration, and 335 in energy content. The added components were a 1/4-W resistor and a 12-mm ferrite toroid with a 10-turn winding.

Nathan O. Sokal

Papers

Class E-A new class of high-efficiency tuned single-ended switching power amplifiers

Power amplifiers and transmitters for RF and microwave

Class of High-Efficiency Tuned Switching Power Amplifiers

Amplifying and processing apparatus for modulated carrier signals

Near-Optimum Dynamic Regulation of DC-DC Converters Using Feed-Forward of Output Current and Input Voltage with Current-Mode Control