The purpose of this report is to have a general view of the present status on research, development and demonstration of fuel cells in addition to their principle and characteristics. Among a few kinds of fuel cells, PAFC has almost reached at the semi-commercial stage, and large efforts have now been given for realizing the PAFC as cogeneration plant using the biogas from garbage and beer brewery process. MCFC is on the way of the demonstration stage with a large scale system under the ledership of NEDO and MITI in Japan. With respect to SOFC several organizations have been taking part in its research and development projects for the purpose of developing super-high efficient power system. PEFC is becoming more and more attractive in expectation of being especially realized as fuel cell propulsion system for electric vehicles and also as residential co-generation devices. A large number of companies have recently entered into the fields related to PEFC system development including fuel delivery infrastructure.

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Catering for the variety of the requests of modern illuminating technology, the various type of discharge arc lamps, such as fluorescent, mercury, sodium, etc., are utilized according to each merit respectively, and therefore the lamp operating circuits for them have to be provided with various configurations and capacities. However, it seems that the common requirements for these circuitperformances are sufficient ignition and reignition voltage, efficient ballastting function and adaptability to operating conditions, for example, line voltage fluctuation, surrounding temperature variation, etc.
Recently, some new lamp operating circuits and/or systems by means of semiconductor devices have been developed to satisfy the above requirements in smaller size, lighter weight and higher efficiency. A new discharge lamp operating circuit described in this paper also belongs in the category, and the experimental results have successfully demonstrated the advantages as follows.
(1) By supplying a lower d. c. source voltage, d. c. 12 V, for example, the lamp of a. c. 100 V ratings can be operated without a transformer.
(2) Sufficient ignition and reignition voltage can be always secured.
(3) It is also possible to adapt this circuit to various kinds of types and ratings of discharge lamps by frequency control.
(4) The drooping characteristics of voltage-ampere relationship of this circuit and also capability of higher frequency operation results in the elimination or reduction of ballast loss and the rise of lamp efficiency. Thus, consequently the overall efficiency can be significantly improved.
(5) The circuit is fit for lamp power regulation, constant current control, automatic dusk, dawn control, etc.

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