An electric circuit for controlling charging of a battery, comprising: a semiconductor switch that is inserted in a switching object line that is connectable on a battery side to a secondary battery and on a system side to a system, the semiconductor switch comprising a first semiconductor switch that controls a supply of power in a first direction of the switching object line, and a second semiconductor switch that controls a supply of power in a second direction reverse to the first direction; and converting means comprising first converting means for controlling the opening and closing of the first semiconductor switch, and second converting means for controlling the opening and closing of the second semiconductor switch, the first converting means being configured to convert an input voltage input to an input side terminal of the first converting means to a first predetermined output voltage and to output the first output voltage from an output side terminal of the first converting means, and the second converting means being configured to convert the input voltage input to an input side terminal of the second converting means to a second predetermined output voltage and to output the second output voltage from an output side terminal of the second converting means, wherein an output side negative terminal of the first converting means is connected to the switching object line on the battery side, and an output side positive terminal of the first converting means is connected to a terminal that controls an opening and closing of the first semiconductor switch; and an output side negative terminal of the second converting means is connected to the switching object line on the system side, and an output side positive terminal of the second converting means is connected to a terminal that controls an opening and closing of the second semiconductor switch. a semiconductor switch that is inserted in a switching object line that is connectable on a battery side to a secondary battery and on a system side to a system, the semiconductor switch comprising a first semiconductor switch that controls a supply of power in a first direction of the switching object line, and a second semiconductor switch that controls a supply of power in a second direction reverse to the first direction; and converting means comprising first converting means for controlling the opening and closing of the first semiconductor switch, and second converting means for controlling the opening and closing of the second semiconductor switch, the first converting means being configured to convert an input voltage input to an input side terminal of the first converting means to a first predetermined output voltage and to output the first output voltage from an output side terminal of the first converting means, and the second converting means being configured to convert the input voltage input to an input side terminal of the second converting means to a second predetermined output voltage and to output the second output voltage from an output side terminal of the second converting means, wherein an output side negative terminal of the first converting means is connected to the switching object line on the battery side, and an output side positive terminal of the first converting means is connected to a terminal that controls an opening and closing of the first semiconductor switch; and an output side negative terminal of the second converting means is connected to the switching object line on the system side, and an output side positive terminal of the second converting means is connected to a terminal that controls an opening and closing of the second semiconductor switch.