| 摘要 |
An electronic ballast (10) for powering at least one gas discharge lamp (30) includes a current-fed resonant inverter (300) and a load shed circuit (600). Inverter (300) ordinarily powers the lamp at a first level. When a load sh ed command is sent by the electric utility and received by an associated load shed receiver within the ballast (10), load shed circuit (600) causes the inverte r to reduce the lamp power from the first level to a second level. Preferably, lo ad shed circuit (600) includes an isolation circuit (620) and a bidirectional switch (640) that is coupled in parallel with a return ballasting capacitor (388) within inverter (300). In the absence of a load shed command, bidirectional switch (640) effectively shunts return ballasting capacitor (388), which causes the lamp to be powered at the first level. In response to a load shed command, bidirectional switch (640) ceases to shunt return ballasting capacitor (388) , thereby causing the lamp power to be reduced to the second level.
|
