| 摘要 |
PURPOSE:To quicken the turn-on operation by providing a voltage limit circuit inserted between secondary windings of a current transformer for positive feedback whose secondary induced current directions are made opposite to each other so as to reduce a reset voltage of the current transformer. CONSTITUTION:The voltage limit circuit 20 has a parallel circuit comprising a capacitor 21 and a Zener diode 22 connected in parallel therewith and a diode 23 connected in series with the parallel circuit, the parallel circuit is connected in parallel with a diode 6 forming a positive feedback current path and the diode 23 is connected in parallel with a Zener diode 5 via the resistor 24. Then a reset voltage generated at the secondary winding of the current transformer is limited to a prescribed level by the voltage limit circuit 20 at turn-off state of the semiconductor switch and the stored charge of the capacitor of the voltage limit circuit charged is supplied as the drive power of the semiconductor switch. Thus, the reset voltage of the current transformer is reduced to quicken the turn-on. |
