Circuit for converting solar energy into AC power

Claim 1

A circuit for converting solar energy into ac power supplementary to household ac power, comprising the combination of: a plurality of solar photovoltaic cells chosen to be as nearly identical as possible; means for connecting said cells in parallel in one or more groups of a certain number of cells, each group having a group short-circuit current, such that when illuminated the group's short-circuit current exceeds a value of application interest; means for connecting said groups of parallel-connected cells in series forming an ensemble such that the open-circuit voltage of the ensemble is 5-20% greater than an absolute value of a peak voltage of the household ac power; four units of switching devices each of which can be operated to pass a current in one direction and having a positive and a negative electrode, the units being connected in a bridge configuration in which the positive electrodes of two units are electrically connected at a first terminal, the negative electrodes of the two other units are electrically connected at a second terminal, and in which one unit of said two units is connected to one unit of said other two units, through a third terminal, the other unit of said two units being connected to the other unit of said other two units through a fourth terminal; means for connecting the ensemble comprising the series connected groups of parallel solar cells to said bridge with the positive voltage terminal of the ensemble connected to the first bridge terminal and the negative voltage terminal of the ensemble to the second bridge terminal; an isolation transformer having a primary coil and a pair of input terminals and at least four low voltage secondary output coils which are isolated from one another and from the primary coil, each having a pair of output terminals; means for connecting the third and fourth terminals of said bridge to the terminals of the primary coil of the transformer; plug which can be plugged into the ac power line; and means for connecting the output terminals of each secondary coil across a pair of control electrodes of the switching devices such that in use the voltages on the control electrodes of the devices on the opposite arms of the bridge have the same ac phase as each other and a phase which is 180° different from the ac phase on the control electrodes of the other two switching devices on adjacent arms of the bridge.