Mantaro Nakamura

Inductor snubber-assisted series resonant ZCS-PFM high frequency inverter link DC-DC converter with voltage multiplier

A variety of high voltage DC power supplies employing the high frequency inverter have difficulty in achieving soft switching considering a quick response and no overshoot response under the wide load conditions which are used in a medical-use X-ray high voltage generator ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1.25 A, respectively. The authors develop a soft switching high voltage DC power supply designed for X-ray power generator applications, which uses lossless inductor snubber-assisted series resonant inverter circuit topology with a multistage voltage multiplier instead of a conventional high voltage diode rectifier connected to the secondary side of a high frequency high voltage transformer with a large turns ratio. A constant on-time dual mode frequency control scheme operating under a principle of zero-current soft switching commutation is described. Introducing the multistage voltage multiplier, the secondary side of turn numbers and stray capacitance of high voltage high frequency transformer is greatly reduced. It is proved that the proposed zero current switching (ZCS) DC-DC high voltage converter topology with dual mode frequency modulation mode control scheme can obtain good transient response and steady-state performance in high voltage X-ray tube load. The effectiveness of this high voltage converter with a high frequency link is evaluated and discussed on the basis of simulation analysis and observed data in experiment.

Performance evaluations on soft-switching boost power converter with a single auxiliary passive resonant snubber

This paper presents boost and buck and buck-boost circuit topologies of high-frequency soft switching transition PWM chopper type DC-DC high power converters with a single auxiliary passive resonant snubber. In the proposed boost power converter circuits operating under the principle of ZCS turn-on and ZVS turn-off commutation schemes, the capacitor and inductor in the auxiliary passive resonant circuit works as lossless snubber which is more effective to reduce the DC load side power recovery feedback-based switching losses of active power switch for high frequency switching and control. In addition to this, the switching voltage and current peak stress as well as EMI and RFI noises can be basically reduced by this single passive resonant snubber. Moreover, it is proved that converter topologies with a passive resonant snubber are capable of solving some problems of conventional hard switching PWM processing based on high-frequency pulse modulation principle of operation, the simulation results of this converter are discussed as compared with the experimental ones.

High frequency PWM boost chopper-fed DC-DC converters with coupled-inductors

In this paper, an advanced two quadrant PWM chopper type DC-DC converter with high boost voltage ratio using coupled inductors and low switch peak voltage stress is proposed for new type parallel processing UPS applications in addition to new energy interface systems. Moreover, a soft switching boost chopper-fed DC-DC converter with high step-up voltage conversion ratio is also proposed. These two boost chopper circuit topologies are evaluated and compared on the basis of simulation and experimental results.

High frequency link transformer secondary side control DC-DC power converter

This paper presents a novel topology of a voltage source zero-voltage switching (ZVS) high frequency inverter type DC-DC power converter with a transformer link, which incorporates zero-current switching (ZCS) mode synchronous phase shifted PWM active power switches into the diode arms of a full-bridge or center tapped rectifier. By implementing the proposed power converter, switching and conduction dissipated power losses of all the active power devices can be reduced which is based on circulating and idling current flowing through a high frequency transformer link compared with the previously-developed soft-switching full-bridge inverter type DC-DC power converter with a phase-shifted PWM scheme in the high frequency transformer primary side. This converter has been assessed on the basis of the simulation operating analysis and performance analysis, together with some experimental results of 2 kW-40 kHz breadboard set up.

High Efficiency Low Noise SMPS System - DC-DC Converter Side

Improvement of DC-DC converter side in SMPS system is discussed in this paper. A novel forward type soft switching DC-DC converter topology with neutral point inductor connected auxiliary resonant snubber (NPC-ARS) circuit is presented in this paper for the switching mode power supply applications. Its circuit operation and its performance characteristics of the forward type soft switching DC-DC converter is described and discussed on the bases of experimental results.

Active auxiliary resonant snubber-assisted soft-switching PWM inverter with optimum gate pulse pattern sequences and its PV-system application

This paper presents an advanced circuit topology and optimum gate pulse patterns for the voltage source bridge type soft-switching PWM inverter, which incorporates a novel active auxiliary bridge commutation leg, associated quasiresonant snubbers as the improved ARCP snubber. In this voltage source type PWM inverter, all the main power switches and the auxiliary power switches can achieve the zero voltage soft-switching (ZVS) or the zero current soft-switching (ZCS). And the periodic steady state circuit operation of this quasiresonant bridge leg link snubber including the auxiliary switch is required to achieve the soft-switching commutation. The complete soft-switching commutation is possible only by determining the gate timing of the main switches and the auxiliary switches, and the circuit parameter design. So the special resonant current and the current and voltage sensor control circuit to achieve soft-switching commutation are not necessary for this resonant snubber. In addition, the optimum gate pulse pattern to minimize the power losses of the resonant snubber treated here. The DC divided middle point composed of the electrolytic capacitor is unnecessary.

A pulse current regenerative auxiliary resonant bridge leg link snubber-assisted three-phase soft switching PWM inverter

In this paper, a novel circuit topology of active auxiliary edge resonant snubber suitable for high power soft switching PWM inverter applications, which has some salient features as compared with previously developed auxiliary resonant commutated pole (ARCP) snubber is proposed in order to minimize the switching power losses of IGBTs in addition to the switching surge related electromagnetic noises in three-phase power conversion circuits on the basis of the sinewave PWM inverter and sinewave PWM PFC rectifier as well as bi-directional PWM converter used as the battery energy storage system. This resonant snubber-assisted inverter suitable for high power conversion is described and discussed on the basis of soft switching transition and commutation operation of the high efficient pulse modulated inverter. The working principle and operating characteristics of this active auxiliary snubber circuit are described, together with the practical design procedure of this unique edge resonant snubber. This paper shows actual efficiency vs. output power characteristic of three-phase soft switching PWM double converter system designed for 10 kVA UPS composed of three phase soft switching PWM rectifier and inverter. The total actual efficiency of three phase soft switching PWM double converter is 88.6% as compared with that of hard switching double converter is 87.0% under a rated load.

Development of digital optimum predictive control implementation for gradient magnetic field current controller in MRI system

This paper presents a digital control scheme for a four-quadrant high frequency PWM chopper type power conversion amplifier. It is the gradient magnetic field current pattern generator which is designed for medical use MRI. The main research objective of this paper is to propose the current control implementation in gradient magnetic coil (GC), which is driven by a high frequency PWM DC-DC converter system with a four-quadrant output scheme. The current pattern required for GC should follow up in accordance with any desired current pattern. In this current amplifier system, the current servo controller employs the optimum type-1 predictive control strategy, which has the advantages for the multiple input voltage and output current. The dynamic and steady state performances of the current PWM amplifier are described and evaluated on the basis of simulation analysis.

A novel switching regulator with active commutation PWM rectifier

This paper presents a new prototype of phase-shifted transformer parasitic components-assisted ZVS-PWM DC-DC converter with choke input type DC smoothing filter which incorporates ZCS active power switches in series with each rectifier diode in high-frequency transformer secondary-side. This efficient DC-DC converter with a wide ZVS operation ranges which is suitable for high-power applications can achieve soft-switching operation under a condition of no circulating current. Its operating principle and unique features are described. The steady-state operating characteristics of the proposed DC-DC converter topology are illustrated and discussed on the basis of the simulation and some experimental results of 2 kW-40 kHz breadboard set up.

Transformer parasitic inductor component-assisted soft-commutation DC-DC converter with rectifier side active power switching control scheme

This paper presents a new prototype of phase-shifted ZVS-PWM DC-DC converter with choke input type smoothing filter which has two active power switches in rectifier side. The wide ZVS area at primary side and ZCS area at secondary side by using the parasitic inductor component of a high-frequency transformer can be achieved by this converter. Its operation principle and features are explained and compared with those of the previously-developed ZVS-PWM DC-DC converter. The steady-state operating characteristics of the proposed converter topology are illustrated and discussed on the basis of the simulation results and experimental ones. Finally, another converter with capacitor input type smoothing filter which operates under a principle of this converter is explained herein.