| 摘要 |
<p>An energy saving dimming system for driving one or more gas discharge lamps (14) together with their ballasts (13) and starters (15), from an A.C. supply (16) whereby the flow of current from the A.C. supply to the lamp and starter assemblies is interrupted for example by the opening of an A.C. switch (1) and a low impedance flywheel path substituted, for example by the closing of a second A.C. switch (12). The control ensures that one such interruption period commences when the polarity of the A.C. SUPPLY (16) changes, but ends when the tube currents signaled by (58 and 59) fall below a threshold. Further interruptions may be added to limit initial current build up for a short period before allowing a longer period of normal conduction prior to the next reversal of the A.C. Supply (16). The A.C. switches may be protected from high voltage spikes by steering diodes (2, 3, 4 and 5) which route current to and from capacitors (9 and 10) connected in parallel with suppressors (8 and 11).</p> |
