Pulsed solar panel light current-voltage characterization based on Zener diode

Application of Zener diode for light current-voltage (LIV) characterization of a solar panel is reported. A typical solar panel is simply a configuration of large number of solar cells connected in series. In order to characterize solar panel light current-voltage (LIV) response, a pulsed light source uniformly illuminates the solar panel, and its current-voltage response is measured using either one of three approaches: variation of resistance, current, or voltage across its output. In this paper, the solar panel LIV data acquisition system is based on variation of computer-controlled direct current (DC) power supply in conjunction with a Zener diode. At the start of the measurement, power supply voltage is set to zero and is slowly increased to balance the solar panel voltage. As power supply voltage becomes larger than solar panel voltage, it becomes reverse-biased under light illumination. The solar panel voltage is reduced to zero and its short-circuit current (Isc) value is measured. For the open-circuit voltage (Voc) measurement, no current must flow through the circuit. Ideally, this condition requires an infinite resistor in the measurement circuit. In order to approximate the infinite resistor for Voc measurement, a Zener diode was investigated. A Zener diode has the ideal characteristic that under reverse bias conditions, it allows no current flow until its breakdown voltage is reached. The breakdown voltage of Zener diodes is configurable over a broad range. Solar panel LIV measurements were successfully demonstrated over a voltage range of up to 22 V.