| 摘要 |
<p>The fluorescent tube (20), supplied by this device, comprises electrodes (21, 22) having each two connection ends (21a, 21b; 22a, 22b). A direct current source (31) is connected to one of the ends (21a, 22a) of each electrode (21, 22) through an induction coil (23) and an electronic switching circuit (32, 33) to automatically adjust the current (IR) to a given rated value. Switches (24, 25) are used for periodically inverting the current circulation direction (IL) through the fluorescent tube (20). The other ends (21b, 22b) of the electrodes (21, 22) are connected to an electronic switch (26) which may be controlled by a control signal (U26) generated by a control device (27). This control signal (U26) controls the switch (26) with a pulse frequency of at least 50 Hz, for opening and closing it periodically. When the switch (26) is closed, the electrodes are heated and the fluorescent tube (20) is shunted, whereas during the opening, the induction coil (23) induces a voltage sufficient to light the tube. The control device (27) comprises means to modify the ratio between the closing duration and the opening duration of the switch (26), thereby allowing the luminosity of the fluorescent tube (20) to be controlled.</p> |
