| 摘要 |
To trigger thyristors (Th) and triacs, pulse transmission circuits which are electrically separated from the thyristors and triacs, and supply powerful trigger pulses of up to 3A within 1 mu s, are required. For this purpose, pulse transformers (5) with ferromagnetic cores are used, their primary winding (6) being connected in series to a pulse start raising circuit (4) which has a capacitor (C) to increase the steepness of a square input pulse (8). If special steps were not taken, at the end of the input pulse (8) the current through the primary winding (6) would revert to 0, and the magnetic induction of the pulse transformer (5) would revert to the remanence value along a hysteresis curve. To radically change the magnetic induction of the pulse transformer (5), and thus generate a powerful trigger pulse for the thyristor (Th) from the square input pulse (8), the magnetisation of the pulse transformer (5) is reversed at the end of the input pulse (8), so that the magnetic induction reverts to approximately 0. For this purpose, the energy of the capacitor (C), which discharges itself via a resistor (R2), a controllable electronic valve (FET), a reversing resistor (R3), and the primary winding (6), is used. When a new input pulse (8) is received, the controllable valve (FET) is blocked. <IMAGE>
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