| 摘要 |
PURPOSE:To enable to obtain two phase control modes for a thyristor by a method wherein changing-over between two thyristor trigger circuits is controlled in accordance with conduction or nonconduction of a switching element. CONSTITUTION:When ON-angle of the thyristor TH is to be controlled, a transistor Q3 is provided as a switching element SW in the trigger circuit to obtain a curve II as shown in the figure, and it is made as the mode change-over element. Namely the circuit is so constituted as when the transistor Q3 constituting the switching element SW is in OFF-state, the second thyristor trigger circuit 2 containing an SBS (silicon bilateral switch) Q5 operates, the first thyristor circuit 1 containing a PUTQ0 stops its operation, and when the transistor Q3 is in ON-state, the second thyristor trigger circuit 2 containing the SBSQ5 stops its operation, and the first thyristor trigger circuit 1 containing the PUTQ0 operates. Accordingly no discrepancy, etc., of change- over timing between two curves I and II in the figure is generated, and smooth changing-over can be performed. |
