The circuit shown has been designed to drive an 8W fluorescent lamp from a 12V source, using an inverter based on the ZTX652 transistor. The inverter will operate from supplies in the range of 10V to 16.5V, 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. Other features of the inverter are:

• it oscillates at an inaudible 20kHz
• it includes reverse polarity protection

How does the circuit operate?
The 270W and 22W resistors bias a ZTX652 transistor into conduction, where the positive feedback given to the transistor by W1 drives it into saturation, thus applying the supply voltage across W2. This causes a magnetising current to build up in W2 until the transformer’s ferrite core saturates. When this happens, the base drive given to the transistor by W1 decays, causing the transistor to turn off.

Read more: 8W fluorescent lamp inverter

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