| 摘要 |
PURPOSE:To operate the switching element on the side of a high potential positively even if a power supply voltage is fluctuated by providing a voltage comparator, which compares the terminal voltage of a capacitor with a preset reference voltage, and limiting a charging current to the capacitor at the preset value. CONSTITUTION:The series circuit of a plurality of switching elements S1 and S2 is connected between both ends of a DC power supply E. A capacitor C1, which serves as a driving power supply, is connected to the switching element S1 in parallel through charge-controlling switching elements Q1, Q3 and Q4. The terminal voltage of the capacitor C1 is compared with the preset reference voltage in a voltage comparator. The voltage comparator turns OFF the charge controlling switch elements Q1, Q3 and Q4 when the terminal voltage reaches the reference voltage. The charging current to the capacitor C1 is limited to the preset value. Therefore, even if the power supply voltage E is fluctuated, the switching element S1 on the high-potential side can be operated without fail. |
