System comprising a photovoltaic cell and a luminous intensity measuring device and method for measuring luminous intensity received by the photovoltaic cell

A method for measuring the luminous intensity received by a photovoltaic cell whose output is electrically connected to an electrical energy storage unit via a DC-DC converter and to an external capacitor arranged in parallel to said DC-DC converter, said measuring method being implemented by means of a device for measuring said luminous intensity, whose input terminal is connected to an output terminal of the photovoltaic cell in parallel to the DC-DC converter and to the external capacitor;

• said measuring method including the following steps:
• A) Connecting a variable resistor between said input terminal of the measuring device and an earth terminal, said variable resistor being arranged to take various values within a plurality of determined resistance values and being programmed by a control unit of the measuring device, and selecting an initial resistance value.
• B) Discharging or charging the external capacitor if the voltage across the external capacitor terminals is higher than a reference voltage, respectively lower than said reference voltage, until the voltage across the terminals of external capacitor is substantially equal to the reference voltage.
• C) Determining whether said input terminal voltage increases or decreases between a first instant, when said voltage is substantially equal to the reference voltage following step B), and a second subsequent instant given said the control unit.
• D) Repeating steps B) and C), either decreasing the value of the variable resistor if the result from step C) in a preceding iteration indicates an increase in said voltage at the input terminal and if the value of the variable resistor in the preceding iteration did not correspond to the minimum value of said plurality of resistance values, or increasing the value of the variable resistor if the result from step C) in a preceding iteration indicates a decrease in voltage at the input terminal and if the value of the variable resistor in the preceding iteration did not correspond to the maximum value of the plurality of resistance values, and performing step D) until the determination, within said plurality of resistance values, of a successive first resistance value and second resistance value at which said output voltage change detector respectively detects a decrease in voltage and an increase in voltage at said input terminal, or, if appropriate, until it is determined that the current supplied by said photovoltaic cell to said output terminal is either lower than the reference voltage divided by the maximum value of said plurality of resistance values, or higher than the reference voltage divided by the minimum value of said plurality of resistance values.