Capacitor device

A capacitor device comprising:

• a capacitor unit;
• a charge circuit for charging the capacitor unit, the charge circuit being configured to be connected to a main power supply;
• a temperature detector for detecting a temperature of the capacitor unit or a temperature around the capacitor unit;
• a reference voltage circuit including a constant-voltage power supply and a voltage-dividing circuit for dividing a voltage of the constant-voltage power supply and outputting a reference voltage that is a constant voltage;
• a comparator circuit comparing a voltage proportional to a voltage of the capacitor unit with the reference voltage so as to cause the charge circuit to operate such that the voltage of the capacitor unit reaches a full-charge voltage;
• and
• a control circuit for determining the full-charge voltage,
• wherein the voltage-dividing circuit includes:
• a first resistor and a second resistor connected in series to the first resistor at a node;
• and
• a first variable resistor unit connected in parallel to the first resistor, the first variable resistor unit including a third resistor and a first semiconductor switching element connected in series to the third resistor, wherein the voltage-dividing circuit outputs the divided voltage from the node and
• wherein the control circuit is operable to:
• determine the full-charge voltage to be a predetermined high-temperature full-charge voltage by turning off the first semiconductor switching element when the detected temperature exceeds a reference temperature;
• and
• determine the full-charge voltage to be a predetermined low-temperature full-charge voltage that is higher than the predetermined high-temperature full-charge voltage by turning on the first semiconductor switching element when the detected temperature is not higher than the reference temperature.