| 摘要 |
1306858 Thyristor switching circuits INTERNATIONAL BUSINESS MACHINES CORP 4 June 1970 [13 June 1969] 26957/70 Heading H3T In a circuit in which an electrically operated device 10 is energized from a source of cyclically varying unidirectional voltage via a control device of the type which can be triggered into a low resistance state in which it remains until the voltage across it falls below an extinction value (thyristor 30), selectively operable means are provided to bias the control device so that it remains in its low resistance state despite a fall in the main source voltage below the extinction level. The electrically operated device 10 is an electromagnet and there are a number n of them, each with an associated thyristor 30-1 ... 30-n, and a common biasing means which comprises a transistor 44 for connecting an auxiliary supply terminal + via diodes 50-1 ... 50-n to the anodes of the thyristors. The electromagnets are actuating magnets in a character printer. The object is to maintain each thyristor/magnet circuit conducting for many cycles of the supply. Instead of the supply arrangements shown 12 ... 26, a bridge rectifier with an untapped transformer may be used, or a half wave rectifying circuit. |
