Control circuit, power conditioner including the control circuit, and photovoltaic system

A power conditioner, comprising:

• a chopper circuit formed by connecting at least two switch elements in a series;
• a capacitor connected in parallel to the chopper circuit;
• and
• a control circuit that controls an ON/OFF status of the switch elements in the chopper circuit to control charging and discharging of the capacitor, wherein the control circuit comprises:
• a measurement controller that measures an inter-end voltage of a capacitor, wherein the measurement controller includes a differential amplifier circuit that differentially amplifies the inter-end voltage of the capacitor;
• and
• a circuit controller that performs a control operation from a measurement output of the measurement controller, wherein the circuit controller calibrates an in-phase component in an output of the differential amplifier circuit as an in-phase error and performs the control operation from a calibrated measurement output from the differential amplifier circuit,
• wherein one of at least two inputs to the differential amplifier circuit is a voltage from a ground of one of the capacitor electrodes when a DC voltage is charged from the one capacitor electrode to the capacitor through one of the switch elements of the chopper circuit during an ON period of the switch element, and the other is a voltage from the ground of the other capacitor electrode.