Device for low-loss switching-load reduction in pulsating operation

摘要

A switch-off unloading network (AEW) for an electronic switch (S) is formed by a series circuit of a parallel capacitor (CP) and a parallel diode (DP) in parallel with the switch (S), the output of which switch is connected via a bridge capacitor (CB) and a bridge diode (DB) in parallel to a freewheel diode (DF). A series circuit of a charging diode (DL) and a charging coil (LL) connects the parallel branch with the bridge branch (CP, DP; CB, DB). The capacitors (CP, CB) are effective in parallel during the switch-off. During subsequent switch-ons, they (CP, CB) are recharged and are connected in series. The switch-off unloading network (AEW) is thereby again prepared for switching off and no intrinsically associated losses arise. In pulsating operation, the current through the freewheel diode (DF) is zero if the switch (S) is not yet switched on. A blocking diode (DS) prevents the parallel capacitor (CP) from being recharged from the difference of the input voltage (U) and the load voltage and the bridge capacitor (CB) from being charged from the load voltage. In the event of subsequent switching on, the parallel capacitor (CP) would otherwise no longer be discharged and a voltage deteriorates the efficiency of the switch-off unloading network (AEW) or makes it ineffective for the switch (S). <IMAGE>