| 摘要 |
A control circuit (5) for controlling current through a load (3) comprises a first terminal (7) for connection to an alternating voltage source (1), a second terminal (9) for connection to the load (3) and a thyristor-type device (11) having a gate terminal (11), connected between the first and second terminals. Voltage regulation means (21) is provided for converting alternating voltage into a direct voltage and is connected between the first and second terminals in parallel with the thyristor-type device (11). Gate current supplying means is provided to supply current to the gate of the thyristor-type device (11), the gate current supplying means being powered by the voltage regulation means (21) and including a variable input device (13) operable to vary a voltage waveform at the gate (19) of the thyristor-type device (11) in order to vary the voltage waveform provided at the second terminal (9). The gate current supplying means is arranged to supply, within a first half-cycle of an alternating voltage applied to the first terminal (7), a first voltage waveform at the gate (19) of the thyristor-type device (11) to supply a gate current to place the thyristor-type device (11) in a conducting state followed by a second voltage waveform to supply a gate current to maintain the thyristor-type device (11) in a conducting state. |
