An optimizer, comprising: a conversion unit, wherein an input end of the conversion unit is configured to be connected to at least one photovoltaic module, and perform power conversion on the connected photovoltaic module; a control unit, configured to control the conversion unit; and an auxiliary power source, an energy storage unit, and a first unidirectional conduction unit that are electrically connected between the conversion unit and the control unit, wherein the auxiliary power source is configured to provide a working voltage for the control unit, the energy storage unit is configured to provide electric energy for the auxiliary power source or the control unit, and the first unidirectional conduction unit is configured to prevent the electric energy of the energy storage unit from falling with a decrease of a voltage of the photovoltaic module, characterized in that the control unit is further configured to perform current-voltage IV curve scanning for voltage segments, wherein the voltage segments are obtained by segmenting a range of an output voltage of the photovoltaic module corresponding to the optimizer from an open-circuit voltage to a preset minimum voltage, and at least two voltage segments are obtained through division, wherein two endpoints of a first voltage segment of the voltage segments obtained through division are respectively the open-circuit voltage and a threshold voltage of the photovoltaic module, wherein the threshold voltage of the photovoltaic module is less than a minimum voltage needed by the auxiliary power source for working, and a range from the threshold voltage of the photovoltaic module to the preset minimum voltage is divided into at least two voltage segments. a conversion unit, wherein an input end of the conversion unit is configured to be connected to at least one photovoltaic module, and perform power conversion on the connected photovoltaic module; a control unit, configured to control the conversion unit; and an auxiliary power source, an energy storage unit, and a first unidirectional conduction unit that are electrically connected between the conversion unit and the control unit, wherein the auxiliary power source is configured to provide a working voltage for the control unit, the energy storage unit is configured to provide electric energy for the auxiliary power source or the control unit, and the first unidirectional conduction unit is configured to prevent the electric energy of the energy storage unit from falling with a decrease of a voltage of the photovoltaic module, characterized in that the control unit is further configured to perform current-voltage IV curve scanning for voltage segments, wherein the voltage segments are obtained by segmenting a range of an output voltage of the photovoltaic module corresponding to the optimizer from an open-circuit voltage to a preset minimum voltage, and at least two voltage segments are obtained through division, wherein two endpoints of a first voltage segment of the voltage segments obtained through division are respectively the open-circuit voltage and a threshold voltage of the photovoltaic module, wherein the threshold voltage of the photovoltaic module is less than a minimum voltage needed by the auxiliary power source for working, and a range from the threshold voltage of the photovoltaic module to the preset minimum voltage is divided into at least two voltage segments.