A very simple portable 12 250V converter can be built using electronic diagram below. This 12 250V converter is designed for portable use with a 12 V car battery. The circuit requires only six transistors, a transformer and some capacitors and resistors and allows to power small consumers. A built astabil multivibrator T1 and T2 generates a rectangular wave at a frequency of 50 Hz. As T1 and T2 drive alternative exit stage system also works in "push-pull". When T1 lead by passing a current T3: T5 and that it engages the latter transistor connects to a half battery of 12 V secondary winding of the transformer Tr When T2 network drive, T6 transistor coupled to the battery the other half of the network adapter. If it is used for output stages 40 411 RCA transistors, the current through secondary winding can be up to 10 A, giving a power output of 180 watts. If you use 2N3055 transistors, power output will be about 90 watts. Since the output transistors are driven to saturation, they have very high mounted radiators.
Although circuit is simple construction and has high efficiency disadvantage is rectangular output voltage which, in the absence of a regulator is dependent on task: small loads, the output voltage is 250 V ac (not working properly for the engine speed control, light dimmers, televisions, hi-fi equipment.