Abstract: A regulating circuit controls current flow from a photovoltaic power source (20) to a storage battery (38) to improve the conversion of solar energy to electric energy. Two transistors (22, 30) are switched on and off at high frequency to regulate the average current flow to the battery. A pulse-width-modulator control chip (42) varies the on-time of each transistor independently to provide separate control of source voltage and circuit output voltage. The source is regulated to produce maximum power and the output voltage is regulated to provide an optimum battery charging voltage. The maximum available energy is transferred from the source to the battery, thereby improving the conversion efficiency of the system.

Abstract: A switching network for improving the conversion efficiency of a photovoltaic power supply comprises a variable coupling circuit for coupling an array of photovoltaic cells to a load resistance. The combined effective impedance of the network and load is varied to match the value required for maximum output power. A switching transistor (22) which connects the source module (20) to the load (30) is pulse-width modulated with a variable duty cycle determined by the control signal from the sensor circuit. A photovoltaic cell (32) similar to those comprising the photovoltaic power module (20) is used to track variations in the ambient light intensity. The open-circuit voltage of a sensor cell (32) is used to determine the proper value of duty cycle required for maximum power transfer. The output voltage of the module (20) is sampled and compared with the proper value to produce a control signal.