Half-bridge push-pull converter to convert 12 volt to higher voltage
There are assembled circuits available which reduces the complexity of this circuit and might improve the efficiency. Search for "EG7500 Inverter switching power driver board compatible KA7500 TL494" to find them.
I am able to light up a 60W light bulb without rectifier secondary site in use. But when using the rectifier the efficiency drops to ~50%.