| 摘要 |
PURPOSE:To improve the hysteresis characteristic by eliminating the insertion of speed control resistance means into a discharging circuit of a capacitor, thereby improving the discharging characteristic of the capacitor. CONSTITUTION:When a foot switch SW is closed, a charging circuit of a capacitor C1 is formed through a diode D6, a transistor TR1 and a diode D9. When the voltage of the capacitor C2 reaches the prescribed value, a diac DA is conducted, a triac TA is conducted, and a motor M is energized. The diodes D6, D9 are interrupted at the end of each cycle of the AC power source, diodes D7, D8 are conducted, and a discharging circuit of the capacitor C1 is formed through the diode D7, resistor R6, transistor TR1 and the diode D8. The conductivity of the transistor TR1 is controlled in response to the depression of a foot switch SW. |
