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 (12-1) that controls a supply of power in a first direction of the switching object line, and a second semiconductor switch (12-2) that controls a supply of power in a second direction reverse to the first direction; and converting means comprising first converting means (23-1) for controlling the opening and closing of the first semiconductor switch (12-1), and second converting means (23-2) for controlling the opening and closing of the second semiconductor switch (12-2), the first converting means (23-1) being configured to convert an input voltage input to an input side terminal of the first converting means (23-1) to a first predetermined output voltage and to output the first output voltage from an output side terminal of the first converting means (23-1), and the second converting means (23-2) being configured to convert the input voltage input to an input side terminal of the second converting means (23-2) to a second predetermined output voltage and to output the second output voltage from an output side terminal of the second converting means (23-2), wherein an output side negative terminal of the first converting means (23-1) is connected to the switching object line on the battery side, and an output side positive terminal of the first converting means (23-1) is connected to a terminal that controls an opening and closing of the first semiconductor switch (12-1); and an output side negative terminal of the second converting means (23-2) is connected to the switching object line on the system side, and an output side positive terminal of the second converting means (23-2) is connected to a terminal that controls an opening and closing of the second semiconductor switch (12-2). 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 (12-1) that controls a supply of power in a first direction of the switching object line, and a second semiconductor switch (12-2) that controls a supply of power in a second direction reverse to the first direction; and converting means comprising first converting means (23-1) for controlling the opening and closing of the first semiconductor switch (12-1), and second converting means (23-2) for controlling the opening and closing of the second semiconductor switch (12-2), the first converting means (23-1) being configured to convert an input voltage input to an input side terminal of the first converting means (23-1) to a first predetermined output voltage and to output the first output voltage from an output side terminal of the first converting means (23-1), and the second converting means (23-2) being configured to convert the input voltage input to an input side terminal of the second converting means (23-2) to a second predetermined output voltage and to output the second output voltage from an output side terminal of the second converting means (23-2), wherein an output side negative terminal of the first converting means (23-1) is connected to the switching object line on the battery side, and an output side positive terminal of the first converting means (23-1) is connected to a terminal that controls an opening and closing of the first semiconductor switch (12-1); and an output side negative terminal of the second converting means (23-2) is connected to the switching object line on the system side, and an output side positive terminal of the second converting means (23-2) is connected to a terminal that controls an opening and closing of the second semiconductor switch (12-2). <EOS>