Switching devices capable of handling more than 800 V exhibit relatively large switching loss. A new current feedback Bi-MOS consisting of a Bipolar Junction Transistor, MOS-FET and current transformer is proposed in this note. The new device reduces switching loss in 100 kHz operation and is expected to result in a DC-DC converter efficiency greater than 90%.

This paper describes configuration and operation of a high-frequency link resonant inverter using cycloconverter techniques. In this inverter, a resonant link high-frequency voltage generated in a primary resonant inverter is isolated by a high-frequency transformer, then directly converted into a resonant link low-frequency voltage in a cycloconverter. The switching losses and surge voltage levels can be reduced by making all switches in the primary inverter and the cycloconverter operate at zero voltage. The relationship between characteristic impedance of the resonant circuit and the conversion efficiency, and the distortion factor characteristics of the output voltage waveforms are discussed by comparing of analytical and experimental results.

A highly reliable and highly efficient fuel-cell energy system is being developed that can run on various fuels and is suitable for a cogeneration system for telecommunications facilities. In this system, electrical power supplants the mains power and heat energy is used for air conditioning. Using this fuel-cell power plant as an emergency generator and ensuring the reliability of telecommunications requires the use of alternate fuels. This plant can run on liquefied petroleum gas(LPG)if the pipeline gas supply stops. Fuel substitution characteristics, and DC and AC interconnection characteristics have been experimentally demonstrated for connections by using a 200-kW phosphoric acid fuel cell and a 150-kW engine generator.

A fuel cell energy system is under development for supply of generated electrical energy to telecommunications equipment. It is a cogeneration system; the heat energy recovered is used to cool the telecommunications equipment. For this system, a method is described for controlling a new DC interconnection converter. Its DC interconnection characteristics are also discussed. The new converter controls its input current to the fuel cell rated current at maximum and can operate stably even when the fuel cell voltage decreases. This allows good DC interconnection characteristics to be obtained in both the steady state and the transient state.