This is the circuit diagram of inverter for 8W fluorescent lamp. The circuit is build based ZTX652 transistor, and used to drive an 8W fluorescent lamp from a 12V source. The inverter will work from 10V to 16.5V DC supply, attaining efficiencies up to 78% thus making it suitable for use in on-charge systems such as caravans / mobile homes/ RVs as well as periodically charged systems such as roadside lamps, camping lights or outhouse lights etc.
The 270W and 22W resistors bias a ZTX652 transistor into conduction, in which the positive feedback provided to the transistor by W1 drives it into saturation, therefore using the supply voltage across W2. This makes a magnetising current to build up in W2 until finally the transformer’s ferrite core saturates. When this happens, the base drive provided to the transistor by W1 decays, triggering the transistor to immediately turn off.
Until the fluorescent tube strikes, the transformer is only loaded by the tube heater filaments which provide only a minimum load. Thus once the transistor turns off the transformer ‘rings’ for half a cycle at a frequency governed by the windings’ inductance and the 0.068mF capacitor, reversing the magnetising current and switching the transistor on again. This ‘ring’ induces a high voltage pulse across the fluorescent tube that will trigger it to strike as soon as the heaters have warmed up.
The moment the tube has struck, it loads the transformer heavily, swamping this ringing action and so significantly cutting down the peak voltage induced across W2 as well as the transistor. This extends the non-conducting period of the inverter cycle and during this period, energy stored in the transformer in the form of magnetising current is dumped into the fluorescent tube. When all of this energy has become dumped, the voltage on the transistor collector drops and it switches on once more.
Inverter for 8W Fluorescent Lamp, Download these documents for your project reference: