| 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 shed 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 inverter to reduce the lamp power from the first level to a second level. Preferably, load 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.
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