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Ihis paper descrites a new control methcd for a high-frequency link inverter using cycloconverter techniques a d discusses its cutput voltage characteristics.In t h i s mthcd, the cyclmverter ccnverts a high frequency voltage to a low frequency voltage by operating in three mcdes: positive rectifying d e , negative rectifying d e and free-&eeling mode. Pulse width dulation (€'"I control is performed at the cycloconverter.Numerical analysis and experiments show that the cutput voltage can be proportionally controlled by a reference voltage and that the cut@ i-mmmics can be decreased to a sufficient low level.A surge reduction circuit is presented for the inverter. This circuit can effectively reduce the switching surge. High ccnversion efficiency of over 90% is obtained under an output pxer of 1 kW. 1.In recent years, m y low prw uninterruptible power supplies (UPSs) of less than 5 kVA have been used to protect quipnent such as p e r m 1 cnnputers, word processors and loa1 area network terminals, fran failures and tenprary disturbances of the cannercia1 AC p e r supply. As these upss are often installed in offices, decreasing in size and weight of UPSs has teccme an iIIprtant goal.The size and weight of a UPS can be reduced by using a high-frequency link inverter, in which the l w frequency transformer is replaced by a high frequency one using high frequency switching techniques. Conventional highfrequency link inverters use three powerconversion stages: a Cc to high-frequency AC cmversion stage, a high-frequency AC to CC conversion stage and a Dc to lar-frequency AC CUIversion stage. Since these omversion stases are cawcted in cascade, the Conversion loss becanes large.The number of conversion stages can be decreased by utilizing cyclaxxlverter techni attain a high-frequency link inverter m' Fs). l h i s papr descrites a new m t r o l methd for a high frequency link inverter using cycloconverter techniques, and discusses its output voltage characteristics. CIRCUIT m G € i R A T I a AND CPERATICN Circuit OxfiqurationThe basic circuit configuration of the high-flink inverter is sham in Fig. 1. ' Ihe main circuit is rrmposed of a prinary inverter circuit, a high-frequency transforner, a cyclooomrerter circuit and an AC filter. S5 -,S are bidirecti-1 ordoff switches thraqh whicfl current can f l w in both directions. 'Ihe block diagram of the m t r o l circuit is Skmn in Fig. 2 . This control circuit is canp e d of an oscillator (OSC), a FiM signal generation circuit and logic circuits for the prinary inverter and for the cycloaxlverter. All these circuits are s y n c h i z e d by the oscillator signal. Primry w cycloconverter AC Filter Imerter Transformer s -s . uidirecti-1 switcher 5 8' Fig. 1 Basic configuration of the high frequency link inverter. PWH signal generation circultFig. 2 Block diagram for the m t r o l circuit.

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