Vapour discharge tube interference filter - has diode in series with capacitor shunted by a high value resistance

摘要

The suppressor filter is designed to shut a semiconductor switch (3) fed with rectified pulses from a rectifier bridge circuit (7, 8, 9, 10). The control circuit of the switch is arranged so as to obtain a variable conducting effect, which is achieved by the combination of a diode (20) connected in series with a capacitor (21) shunted by a relatively high valve resistance (22). The time constant of the resistance capacitance network (19) is slightly less than the period of duration of the rectified pulse. The filter is useful for devices such as a light dimmer, an electronic speed control device for an engine etc. The active control element, typically a thyristor, is protected against discharges producing damage through thermal overload.