GB1327440A - Thyristor circuit arrangement - Google Patents

Abstract

1327440 SCR control circuits AUTOELEKTRONIK AG 18 Nov 1970 [20 Nov 1969] 54849/70 Heading H3T [Also in Division F1] An SCR 6 is triggered on by the current surge into a capacitor C2 when another SCR 5 turns on, C2 being discharged by a circuit including for example R2, D2, R4, D6, and both the charging and discharging of C2 being controlled by a switch U. The switch U is driven by rotation of an internal combustion engine whose ignition is effected by the SCR 6, which discharges a capacitor C3 into a transformer 7 driving a spark-gap F. Assuming a capacitor Cl to be initially charged, the opening of contacts 3a, 3b removes the earth connection from D6 cathode and allows current from Bt to flow into C2 through R5, D3, R4, R8, R2 until gate G5 of SCR 5 is positive enough to turn on SCR 5. This enables C1 to discharge via a transformer winding 2c and the SCR 5 into C2. The sudden current thus produced in R7 produces the igniting signal for SCR 6. A pulse is also applied via winding 2c to a transistor T, which is thus turned on. When it subsequently blocks and turns off again, an induced voltage across the primary 1a of a transformer 1 recharges C1 through D1, and the secondary 1b recharges C3, ready for the next cycle. Before the next cycle however, contacts 3a. 3b close to discharge C2 through R2, D2, R4, D6 to earth; the time constants being made large enough to ensure that contact bounce of 3a, 3b does not erroneously re-energize SCR 5.