Embodiments of this application disclose a design of an inverter and a design of a combiner box, to reduce maintenance costs of a photovoltaic device. According to the inverter or the combiner box provided in the embodiments of this application, when electroluminescence (EL) defect detection is performed on the photovoltaic device, a reverse charging circuit integrated into the inverter or integrated into the combiner box is used to output a direct current to a to-be-tested photovoltaic string of the photovoltaic device. Whether the to-be-tested photovoltaic string has defects is determined based on a light emission status of the to-be-tested photovoltaic string. By using the foregoing designs, maintenance engineers do not need to modify wiring terminals of the photovoltaic device when performing EL defect tests on the photovoltaic device. This helps reduce maintenance costs of the photovoltaic device.