Duty Ratio Of Switch Research Articles

Nonlinear-carrier control for high-power-factor rectifiers based on up-down switching converters

In this paper, nonlinear-carrier (NLC) control is proposed for high-power-factor rectifiers based on flyback, Cuk, Sepic, and other up-down power converters operated in the continuous conduction mode (CCM). In the NLC controller, the switch duty ratio is determined by comparing a signal proportional to the integral of the switch current with a periodic nonlinear-carrier waveform. The shape of the NLC waveform is determined so that the resulting input-line current follows the input-line voltage, as required for unity power factor rectification. A simple exponential carrier waveform generator is described. Using the NLC controller, input-line voltage sensing, error amplifier in the current-shaping loop, and multiplier/divider circuitry in the voltage feedback loop are eliminated. The simple high-performance controller is well suited for integrated-circuit implementation, Results of experimental verification on a 150 W flyback rectifier are presented.

PWM-controlled series compensation with low harmonic distortion

The paper describes a pulse width modulation (PWM)-controlled series compensator with continuously variable reactance, employing simple PWM duty ratio control. Each phase of the compensator comprises a switched reactor and parallel capacitor. The duty ratio control gives a wide range of capacitive and inductive compensation. The harmonics created by the switched reactor have been analysed. The switched reactor and parallel capacitor have been simulated with a range of switching frequencies and duty ratios. With appropriate choice of capacitor and reactor. A scaled-down experimental model of the compensator has been simulated and constructed. The harmonics have been found to be small even with the switching frequency of the controlled turn-off switches as low as 400 Hz. A large step change in duty ratio from maximum capacitive compensation to inductive compensation shows the rapid dynamic response of the compensator with a fast settling time. This demonstrates that the proposed compensator should be considered as another useful FACTS controller for series compensation.

Nonlinear-carrier control for high-power-factor boost rectifiers

Novel nonlinear-carrier (NLC) controllers are proposed for high-power-factor boost rectifiers. In the NLC controllers, the switch duty ratio is determined by comparing a signal derived from the main switch current with a periodic, nonlinear carrier waveform. As a result, the average input current follows the input line voltage. The technique is suitable for boost converters operating in the continuous conduction mode. Input voltage sensing, the error amplifier in the current-shaping loop, and the multiplier/divider circuitry in the voltage feedback loop are eliminated. The current-shaping is based on switch (as opposed to inductor) current sensing. The NLC controllers offer comparable or improved performance over existing schemes, and are well suited for simple integrated-circuit implementation. Experimental verification on a 240 W rectifier is described.

Low Frequency Characterization of PWM Converters

Low frequency components of states or outputs in pulse-width modulation (PWM) dc and ac converters can be characterized by differential equations called describing state-space equations. These equations are derived by inspection of converter topology and use of switching functions and duty ratios. Their steady-state and small-signal dynamic solutions show how energy-storage elements in a converter/load system shape the frequency response of conversion functions established by the switches.

Class E tuned power amplifier with nonsinusoidal output voltage

An analysis is presented of the amplifier for a limiting case when the load network does not contain a series-resonant output circuit and the output voltage is non-sinusoidal. For optimum operation with any switch-duty ratio, the author has determined the current and voltage waveforms, the collector current and collector-emitter peak values, the output power, the power-output capability, and the load-network component values. The spectrum of the output voltage is given for a switch-duty ratio of 0.25, 0.5, and 0.75. Close-approximation equations are given for transistor power losses and collector efficiency. The experimental and theoretical results are in very good agreement. The measured collector efficiency is 95%. The circuit has practical applications, e.g., in high-efficiency switching-mode DC-to-DC converters used in DC power supplies for microcomputers or communication equipment.

A multiinput type converter for an uninterruptible dc power supply

AbstractLow‐power uninterruptible dc power supplies have been used widely. These are powered by several types of power sources with differing voltages, e.g., commercial ac power sources as well as batteries. A multi‐input‐type converter is developed to simplify circuit configuration and realize a low‐loss power system.This paper presents a method of designing a multiinput transformer as well as the operation principle of a multiinput‐type uninterruptible power supply and the circuit technology required for it. The power supply can be realized if the transformer primary winding‐turn ratio is designed considering the input voltage variation range and the voltage‐drop in the transformer primary circuit. The fact that the switching‐duty ratio must be changed drastically and that the switching transistor loss is inclined to increase in a multiinput‐type converter causes some problems. It is shown that the application of a collector current proportional drive circuit to the forward‐type converter or a base resistor switching circuit to the flyback‐type converter is effective in reducing the converter loss and the converter can be simplified by using most of the converter circuits in common.

Exact analysis of class E tuned power amplifier with only one inductor and one capacitor in load network

Presents an exact analysis of that amplifier, an accurate and simple design procedure, and experimental results which confirm the theoretical analysis. The following performance parameters are determined for optimum operation with any switch duty ratio: the current and voltage waveforms, the peak values of collector current and collector-to-emitter voltage, the output power, the power-output capability, and the component values of the load network. The output harmonic spectrum is given for several values of switch duty ratio. The transistor power losses and collector efficiency are also estimated. The measured collector efficiency was over 95 percent with 3 W output power at 1 MHz, using a BSX60 TO-39 transistor.

Low-Frequency Characterization of Switched dc-dc Converters

Averaging techniques are developed to represent buck, boost, and buck-boost types of switched dc-dc converters by approximate continuous models. Simple analytical expressions in terms of the circuit components are derived for the characteristic transient and frequency responses of time-average(continuous) power-stage models for use in designing and understanding the behavior of corresponding switched power stages. Novel conclusions include the dependence of effective circuit component values upon switch duty ratio and the existence of a real positive zero in certain transfer functions. Responses from analog computer simulations of the switched and averaged powerstages agree well and, in turn, confirm the analytic predictions. High-order systems can be analyzed by the averaging technique without a commensurate increase in complexity.