Push-pull applications makes a more reliable waveform output than that of a flyback converter. Thus it can be used. The below circuit have a push-pull transformer, with two Switching transistors, whose base feedback is collected from the transformer itself (self oscillating).
This one has output power of upto 18Watt stated at 12V, though we can see the output is coupled by a series capacitor/diode here.The transformer has 5 lines at input section. Central connector goes to +VE supply, through a L1 inductor coil. It absorbs the spikes due to the switching of transformer.
L1 should be 10mH to 100mH wit ferrite core. There two power stage pins, and two feedback goes to each of transistor’s collector, base.
The initial base feeding is done by a 220 Ohm resistor to the base of any of the transistor, having a capacitor of 104(0.1uF) to the other transistor. This technology can be used for similar CFL lighting/ mobile charging etc applications which does rectify the input power to DC.
The most advantage of this circuit is that this circuit glows CFL even at huge battery discharge. Experiments show, Light stays till battery voltage goes down to 5V. It’s not safe to run appliances upto that discharge level, as that would lead ‘sulphation’ to the battery plates.
Here is used D880 or 1351 transistor for a output of 18Watt, but similarly we can use 2N3055 transistor in this setup with a big transformer to make output of upto 100W.
Front side of the PCB
Back side of the PCB
The cost of whole parts is low compared to the total setup cost, We can arrange parts for it within 40 rupees to 80 rupees for quality, And the total kit is normally sold in spare parts shop at 60~150. (Appx 1.3~3 USD)