Discrete 1x18w Hf-tl Ballast

A description is given of a 1x18W HF-TL ballast and evaluation board (PR37692) which is able to drive a T8 TL- D lamp. The ballast, which is a Voltage Fed Half Bridge Inverter, has been designed for a nominal mains input voltage of 230Vrms±15%. The bipolar power switching Transistor BUW85 is driven by a Discrete driver circuit and a small driver transformer with a Multihole Binocular Core (MHB2). The free running frequency is approximately 45kHz. The system incorporates EMC filtering and a start-up and protection circuit. In the underlying report a description is given a of 1x18W HF-TL ballast and evaluation board. The ballast is a self-oscillating Voltage Fed Half Bridge Inverter, which has been developed to drive one 18W (T8) TL-D lamp. The circuit has been designed for a nominal input voltage of 230Vrms±15%, 50-60Hz and an input voltage range of 160-265Vrms. One of the key components is the BUW85 power switching Transistor but also the BUX85 CAN equally well be applied. The power switching Transistor is driven by a Discrete driver circuit, consisting of BYD33D Diodes and a small driver transformer with a Multihole Binocular Core (MHB2). This transformer determines, together with the ballast coil and the ignition capacitor, the free running frequency of approximately 45kHz. The printed circuit board (PR37692) contains a mains Filter to fulfil all EMC requirements but, since the power dissipated is less than 25W, a preconditioner is not incorporated.
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