Apparatus for continuous control of electric devices according to the phase chopping principle, especially light dimmer, and the use of such apparatus

摘要

An apparatus for stepless control of electric loads by the phase-angle principle includes a semiconductor switch element with main electrodes. A trigger circuit furnishes turn-on pulses for triggering the switch element and includes a detector for the polarity of an instantaneous value of an alternating voltage to be switched, a turn-on pulse pregenerator circuit for furnishing turn-on pulse suggestions, a switch and driver unit, and a decision stage. The decision stage may allow or prevent the turn-on pulse suggestions to be switched through to the switch element, as a function of whether an output signal of the detector has changed its polarity between two of the turn-on pulse suggestions. The decision stage may furnish a blocking signal at least at one input for preventing the turn-on pulse suggestions from being switched through to the switch element, upon the appearance of two turn-on pulse suggestions within one half-wave of the alternating voltage to be switched and in the absence of a turn-on pulse suggestion during one entire half-wave of the alternating voltage to be switched. For brightness control, a transformer has a secondary winding connected to an incandescent bulb and a primary winding connected to one pole of an alternating voltage source and to one main electrode, while another pole of the voltage source is connected to another main electrode.