Shin-ichi Motegi

A single-phase buck-boost AC-to-DC converter with high-quality input and output waveforms

This paper describes a new single-phase buck-boost power factor correction (PFC) converter with output-voltage-ripple-free operation. The rectifier is operated by two modulators which obtain PFC and the ripple-free operation, respectively. The modulator controls the buck-boost switch to obtain PFC. On the other hand, another modulator controls squire-value of instantaneous-inductor-current to perform the ripple-free operation. In both modulation, space or time-integral-value of the input and output currents in each modulation period is controlled directly and indirectly, respectively. Thus, modulation errors or distortions of the currents are eliminated even if the DC-inductor-current produces large ripples. The theories and combination technique of the modulators, implementation and experimental results are shown.

Comparison of the characteristics between buck and buck-boost high-power-factor converters with pulse-space-modulation

The current-fed high-power-factor converters (buck and buck-boost converters) have several advantages, such as no lower-limit of the output-voltage control range and no rush-current of the input-current. However, the single-phase current-fed high-power-factor converter with PWM (pulse width modulation) produces undesirable lower order harmonics in the input-current. Thus, the PWM requires a bulky and costly inductor connected in the DC-side of the current-fed converter to reduce the DC-inductor-current ripples. To overcome the problem, the authors have proposed PSM (pulse-space-modulation). This paper describes a comparison of the characteristics (THD (total harmonic distortion of the input-current), the power factor and reducing DC-inductors inductance) between buck and buck-boost high-power-factor converters applying PSM. The buck-boost converter has many advantages over the buck converter in the input current waveform, power factor and reducing DC-inductors inductance. To illustrate the validity of the theory, experimental results obtained from a 1.2 kW setup and computer simulation results are shown.

A single-phase buck-boost PFC converter with output-voltage, ripple-reducing operation

This paper describes a new single-phase buck-boost power-factor-correction (PFC) converter with output-voltage, ripple reducing operation. The converter consists of a conventional buck-boost PFC converter and an additional switch to obtain a freewheeling mode of the dc inductor current, and is operated by two modulators. The first modulator controls the buck-boost switch to obtain PFC. The other modulator controls the square value of the instantaneous dc inductor current to perform the output-voltage-ripple-reducing operation. In the two modulations, the time integral value of the input and output currents in each modulation period are controlled directly and indirectly, respectively. Thus, modulation errors or undesirable distortions of the input current and output voltage ripple are eliminated even if the dc inductor current produces large ripple in a low-frequency range. The theories and combination techniques for the two modulators, implementation, and experimental results are described.

A new single-phase high-power-factor converter with buck and buck–boost hybrid operation

In recent years, a wide variety of high-power-factor converter schemes have been proposed to solve the harmonic problem. The schemes are based on conventional boost, buck or buck-boost topology and their performance, such as output voltage control range in the boost and buck topology or efficiency in the buck boost topology are limited. To solve this, the authors propose a single-phase high-power-factor converter with a new topology obtained from a combination of buck and buck-boost topology. The power stage performs the buck and buck-boost operations by a compact single stage converter circuit while the simple controller/modulator appropriately controls the alternation of the buck and buck-boost operation and maintains a high quality input current during both the buck and buck-boost operations. The proposed scheme results in a high performance rectifier with no limitation of output voltage control range and a high efficiency. In this paper, the principle and operation of the proposed converter scheme are described in detail and the theory is confirmed through experimental results obtained from a 2[kW] prototype converter.

An Experimental Study on a PWM Method without Dead-Time Error for Three-Phase Voltage-Fed Inverter

Voltage-fed inverters have dead-time to protect against short-circuit of the DC-link voltage. Dead-time distorts ACoutput voltage and decreases DC-link voltage utilization. To overcome these problems, the authors propose a novel PWM method without voltage error caused by the dead-time of the converter. In this paper, the principle and theoretical operation of the proposed PWM method are described in detail and the theory is confirmed through experiment results.

Proposal of Inrush Current Prevention Circuit without Electrical Relay

Generally, in electric equipment, a large inrush current flows in the capacitor when the power is turned on. The inrush current causes deposition of terminals and switches, melting of fuses, and so on. Therefore, conventional inrush current prevention circuits using an electrical relay and a controller are provided. However, the use of electrical relay enhances concern about an increase in cost and charge-time. In order to solve these problems, this paper proposes the inrush current prevention circuit without electrical relay. In this paper, the authors examine the effectiveness of the proposed circuit from experimental results.