| 摘要 |
PURPOSE:To prevent the bad effect of a parasitic capacity by short-circuiting temporarily the primary winding of a driving pulse transformer of one of a pair of transistors which are turned on and off alternately when the other transistor is turned off. CONSTITUTION:When a transistor TRQ3 is turned on at a time point t1, a TRQ1 is turned off. Then both TRQ1 and Q2 are turned off. When a TRQ4 is turned off at a time point t2, the TRQ2 is turned on. At the same time, a TRQ3' is turned on for a short time at a time point t2. Thus a primary winding N1 of a pulse transformer T1 is short-circuited substantially with the TRQ3 and Q3' while the electric charge of a parasitic capacity Cob1 is discharged as a current ic via the TRQ2. Therefore both ends of a secondary winding N2 are also short-circuited equivalently, and no reverse voltage is produced even in case the discharge current ic flows to the winding N2. Thus the transformer T1 is never adversely energized. This can avoid such a malfunction where the TRQ1 is turned on. |
