Abstract: An electrical converter for supplying electrical power to a load from a d.c. source and which includes semi-conductor switching means for converting a direct input current to an alternating current and output transformer means fed with the alternating current for changing the magnitude of the output voltage with respect to the input voltage, wherein the semiconductor means includes transistor means connected with a drive transformer means in a configuration which provides for switching in response to saturation of at least a part of the drive transformer means, and the drive transformer means includes a winding connected in the main current circuit of the transistor means in a configuration providing current feed-back to a drive branch of the circuit connected to a control electrode of the transistor means to increase the response of the transistor means to drive signals derived from the input current and effectively provide a forced D.C.