| 摘要 |
The invention is concerned with a fluorescent tube driver arranged to be supplied by a direct voltage source (particularly a voltage source less than 50 volts, preferably 24 volts nominal) and having a tube drive output in the range 10 to 100 watts of arc power (preferably 10 to 40 watts) with a frequency of oscillation in the range 15 to 50 KHz (preferably 32 KHz nominal), the driver comprising an arc waveform transformer (22), the primary winding (23) of which is supplied with a variable drive current derived from the low voltage source (15), and the secondary winding (25) of which is adapted to be connected to the electrodes (13, 14) of a fluorescent tube (12), such that in use an alternating tube arc current will flow through the secondary winding and tube. The drive includes a closed loop control system (31-44) provided for maintaining substantially constant the tube arc current by varying the amplitude of the arc current waveform without varying the pulse width. This extends the tube life and reduces the wasted heat. The arc transformer driver (24) and arc current are selected to give a symmetrical arc waveform with a constant waveform duty cycle in the range 90 to 95 %, and a tube arc power less than 90 % of the rated tube power, and to maintain at a constant value in the range 1.3 to 1.5 the arc crest factor. |
