DC-AC converting arrangement for photovoltaic system

Claim 1

In a power supply system for supplying power to a load by switching between a commercial power source and a photovoltaic system, a DC-AC converting arrangement comprising: a DC-AC converting section for producing an output by subjecting a DC electric power from a solar cell array to a DC-AC conversion, said DC-AC converting section having a higher converting efficiency when its output voltage is high; detecting means for sensing an output voltage of said DC-AC converting section; operation control means, coupled to said DC-AC converting section, for stopping operation of said DC-AC converting section at a time point when the output voltage of said DC-AC converting section, sensed by said detecting means, is lower than a predetermined reference value below which said DC-AC converting section functions at a reduced efficiency; and switch means, responsive to the stopping of the operation of said DC-AC converting section, for immediately supplying the commercial power to the load.

Claim 4

A system providing alternating current (AC) power to a load from direct current (DC) power produced by a solar cell array or from a commercial power supply developing a commercial power output, comprising: means for converting the DC power into an AC power output; switching means for selectively applying said AC power output or a commercial power output to a load; means for detecting a voltage of said AC power output produced by said means for converting; and operation control means, connected to said means for detecting, for comparing the detected voltage of the AC power output to a reference value and applying a suspension signal to said means for converting when the detected AC power output falls below said reference value, said suspension signal halting operation of said means for converting; said switching means being responsive to the halting of operation of said means for converting in response to said suspension signal to immediately convert said commercial power supply to said load.

Claim 5

A system providing alternating current (AC) power to a load from direct current (DC) power produced by a solar cell array or from a commercial power supply developing a commercial power output, comprising: means for converting the DC power into an AC power output; switching means for selectively applying said AC power output or a commercial power output to a load; means for detecting a voltage of said AC power output produced by said means for converting; and operation control means, connected to said means for detecting, for comparing the detected voltage of the AC power output to a reference value and applying a suspension signal to said means for converting when the detected AC power output falls below said reference value, said suspension signal halting operation of said means for converting; said switching means being responsive to the halting of operation of said means for converting in response to said suspension signal to immediately convert said commercial power supply to said load.