Electronic load switching circuit with harmonic suppression - has switching pulse generator coupled to asynchronous voltage generator

摘要

The circuit coupling the load (1) to the mains network (2,3) has an electronic switching element (4) coupled via its control electrode to a pulse generator (5,6,7) synchronised with the mains frequency. This pulse generator (5,6,7) is coupled to a second providing a periodic voltage which is asynchronous with the mains frequency. Pref. the switching element comprises a triac (4) with the control pulse generator (5,6,7) comprising a resistor (5), a capacitor (6) and a diac (7) coupled to the trigger of the triac (4). The other electrode of the diac (7) is coupled to the junction between the resistor (5) and the capacitor (6), receiving the pulses from the asynchronous generator (8). The latter is pref. supplied from the mains via a diode rectifier bridge. The circuit has a reduced level of harmonics upon chopping of the load current to adjust the power.