and suppression impedance 10 is serially connected between the filter inductor 6 and one terminal here illustrated as the positive terminal of the filter or storage capacitor 8 as shown the anode of scr 12 is connected to the filter inductance 6 and additionally to one terminal of impedance 10 the cathode of the scr is connected in common to one terminal here illustrated as the positive terminal of storage capacitor 8 and additionally to suppression impedance 10 the gate or control terminal of scr 12 is connected to its cathode terminal through gate bias resistor 14 the gate is additionally connected to the collector terminal of first control transistor 18 as shown the base of first transistor 18 is connected through resistor 24 to its emitter terminal the latter being further connected to input terminal b a second control transistor 20 has its collector connected to the base of 18 through resistor 22 and emitter connected in common to the other end terminal of capacitor 8 and to the negative output terminal 9 the base of transistor 20 is connected to the anode of control zener diode 16 the cathode of zener 16 is connected to one terminal here shown as the positive terminal of capacitor 8 through resistor 17 a protection diode 26 has its anode connected to the positive terminal of the storage capacitor 8 and its cathode connected to the emitter of first control transistor 18 still referring to fig1 in a quiescent state capacitor 8 is substantially uncharged and scr 12 is in a nonconductive turned off state similarly soft start control circuit 2 in the quiescent state has first and second transistors 18 and 20 and zener control diode 16 in a non conductive turned off state upon applying an initial.