| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply unit with built-in electric double-layer capacitors wherein the safeties to their overchargings and dischargings are considered thoughtfully and their instantaneous charging or discharging currents are made large. SOLUTION: A voltage sensing portion 11 senses the voltage applied across positive and negative terminals 5A, 5B of electric double-layer capacitors 1 connected in series with each other. The voltage applied across the terminals 5A, 5B or the electric double-layer capacitors 1 is increased when the capacitors 1 are charged excessively. A voltage comparing portion 19 decides whether the voltage applied across the terminals 5A, 5B exceeds an upper limit voltage or not. In the meantime, the voltage applied across the terminals 5A, 5B of the electric double-layer capacitors 1 is decreased when the capacitors 1 are discharged excessively. A voltage comparing portion 15 decides whether the voltage applied across the terminals 5A, 5B drops beyond a lower limit voltage or not. The comparison results of the voltage comparing portions 19, 15 are sent to a control portion 21 of a charge/discharge limiting switch 7 to perform the ON/OFF of the switch 7. |
