Jung G. Cho

A general circuit topology of multilevel inverter

A generalized circuit topology of multilevel voltage source inverters which is based on a direct extension of the three-level inverter to higher level is proposed. The circuit topologies up to five-level are presented. The proposed multilevel inverter can realize any multilevel pulsewidth modulation (PWM) scheme which leads to harmonic reduction and provides full utilization of semiconductor devices like GTOs, especially in the high power range where high voltage can be applied. The capacitor voltage balancing problem is discussed and a circuit remedy for such a problem is given.<<ETX>>

Novel soft switching PWM converter using a new parallel resonant DC-link

A novel soft switching pulsewidth modulated (PWM) converter for high-frequency AC/DC and/or DC/AC power conversion is presented by using a parallel resonant DC-link (PRDCL) and by adopting single-phase soft switching (SPSS) technique. The PRDCL provides variable link pulse position as well as variable link pulse width, which is a quite different feature from the other resonant DC-links, and thus the PWM capability can be increased. The SPSS technique is adopted for further enhancement of PWM capability. Moderate combination of two soft switching operations enables the conventional space vector PWM technique to be used. Due to distinctive advantages, including true PWM capability, minimum device voltage stresses, and reasonable additional device count, the proposed converter can be operated in a wide power range (20-200 kW). Operational principles, analyses, and the realization of a space vector PWM of the proposed converter are presented. Simulation results are shown to verify the operational principle.<<ETX>>

Soft-switched matrix converter for high frequency direct AC-to-AC power conversion

Abstract A soft-switched matrix converter is proposed using the zero voltage switching technique in some resonant pole inverters. A high operating frequency with safe and efficient switching improves the dynamic and spectral performances and simplifies the protection logics and snubber networks. Further, it can be implemented using simple analogue circuits, having similar transfer characteristics to those of the modern pulse width modulated matrix converters, such as maximum voltage transfer ratio and unity input displacement factor. Analyses, design and simulation results are presented to verify the operating principle.

Novel off-line zero-voltage-switching PWM AC/DC converter for direct conversion from AC line to 48 VDC bus with power factor correction

An offline zero-voltage-switching (ZVS) PWM AC-DC power converter for single-stage preregulation in distributed power systems is proposed. The converter provides both input power factor correction and direct conversion from a 110-220-V AC line to a 48-V DC bus with a single power stage. Compared to the conventional two-stage approach (a boost rectifier followed by an offline DC-DC step-down converter), the proposed approach reduces the loss of one power stage. A new simple auxiliary circuit provides the zero-voltage-switching (ZVS) condition to all semiconductor devices without imposing additional voltage and current stresses and loss of PWM capability. The operational principle, analysis, control of the proposed power converter, and simulation results for a 1-kW prototype are presented.<<ETX>>

Single-cycle resonant converters: a new group of quasi-resonant converters suitable for high-performance DC/DC and AC/AC conversion applications

A novel resonant switch and a family of zero-current and zero-voltage mixed-mode switching quasi-resonant converters (QRCs) called single-cycle resonant converters (SCRCs) are proposed to improve the performance of the conventional QRCs. The SCRCs, which include two active switches operated with zero-current switching (ZCS) and zero-voltage switching (ZVS), respectively, show very simple operation and ease of control and analysis, and they overcome the limited load range characteristics of the conventional ZCS QRCs. The SCRCs can be applied even for a high-frequency AC chopper by replacing unidirectional switches with bidirectional ones. Steady-state operation and characteristics of the buck-type SCRCs are analyzed and compared with those of the buck-type full-wave QRC (FW-QRC). Experimental results at a a 200 kHz, 1 kW level are shown to verify the operational principle and characteristics. >

Cyclic quasi-resonant converters: a new group of resonant converters suitable for high performance DC/DC and AC/AC conversion applications

The conventional resonant switch and quasi-resonant converters (QRCs) are generalized with regard to the viewpoint of a switch cell. A new resonant switch and a new family of resonant converters, the cyclic resonant switch (CRS) and cyclic quasi-resonant converters (CQRCs), are proposed as a part of the generalized topologies of QRCs. The CQRCs show very simple operation and easy control and analysis. They overcome the limited control range characteristics of the conventional QRCs and they can be applied for an AC chopper as well as a DC/DC converter. Steady-state operations and characteristics of the buck-type CQRC are analyzed and verified experimentally for a 200 kHz, 1 kW power level.<<ETX>>

A generalized quantum resonant converter using a new quantum resonant module

For the generalization of quantum resonant converters, new quantum resonant modules, which are a quantum series resonant module (QSRM) and a quantum parallel resonant module (QPRM), are proposed. The QSRM and QPRM are modeled as an equivalent inductor and an equivalent capacitor, respectively. The models of the proposed modules are useful in deriving the practical family of quantum resonant converters corresponding to the conventional PWM converters. The AC/AC quantum resonant converters are useful in high-performance applications. The concept of modules and the validity of the modeling are confirmed by the experiment. >

Program-controlled soft switching PRDCL inverter with new space vector PWM algorithm

A soft switched space vector PWM inverter is developed using new parallel resonant DC-link (PRDCL). This PRDCL can operate on variable DC-link pulse position and width resulting in enhanced PWM capability, which is superior to other resonant DC-links. A new space vector algorithm is presented suitable for this PRDCL inverter. The suggested algorithm is able to eliminate narrow PWM pulses that impede DC-link operation. This PWM control, however, requires complex and precise timing sequences in relation to PRDCL operation, which is nicely solved by adopting a new programmed controller with a buffer and a programmable timer.

Novel high efficiency base drive using zero voltage switching converter

A small size and high efficiency base drive scheme using a high frequency partial resonant converter with zero voltage switching (ZVS) is proposed. By using this base drive, the performance of switching power transistors is enhanced to some extent because the transistor can be lightly saturated in accordance with the load condition owing to easy control capability of transistor base current.<<ETX>>