Electronic ballast with load shed circuit
First Claim
1. A ballast for powering at least one gas discharge lamp, the ballast comprising:
- a current-fed resonant inverter adapted for connection to the at least one gas discharge lamp and operable to provide a lamp power to the lamp, the lamp power having a first value and a second value, wherein the second value is less than the first value; and
a load shed circuit coupled to the inverter and operable, in response to a load shed command, to cause to the inverter to reduce the lamp power from the first level to the second level, wherein;
the current-fed resonant inverter comprises;
a pair of input terminals adapted to receive a substantially direct current (DC) voltage;
a first output terminal and a return output terminal, wherein the first output terminal and the return output terminal are adapted for connection to the lamp; and
a first ballasting capacitor and a return ballasting capacitor, wherein the first ballasting capacitor is coupled to the first output terminal, and the return ballasting capacitor is coupled to the return output terminal; and
the load shed circuit comprises;
an isolation circuit adapted for coupling to a load shed receiver; and
a bidirectional switch coupled to the isolation circuit, the bidirectional switch including first and second output connections coupled in parallel with the return ballasting capacitor.
2 Assignments
0 Petitions
Accused Products
Abstract
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.
21 Citations
25 Claims
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1. A ballast for powering at least one gas discharge lamp, the ballast comprising:
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a current-fed resonant inverter adapted for connection to the at least one gas discharge lamp and operable to provide a lamp power to the lamp, the lamp power having a first value and a second value, wherein the second value is less than the first value; and a load shed circuit coupled to the inverter and operable, in response to a load shed command, to cause to the inverter to reduce the lamp power from the first level to the second level, wherein; the current-fed resonant inverter comprises; a pair of input terminals adapted to receive a substantially direct current (DC) voltage; a first output terminal and a return output terminal, wherein the first output terminal and the return output terminal are adapted for connection to the lamp; and a first ballasting capacitor and a return ballasting capacitor, wherein the first ballasting capacitor is coupled to the first output terminal, and the return ballasting capacitor is coupled to the return output terminal; and the load shed circuit comprises; an isolation circuit adapted for coupling to a load shed receiver; and a bidirectional switch coupled to the isolation circuit, the bidirectional switch including first and second output connections coupled in parallel with the return ballasting capacitor. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A ballast for powering at least one gas discharge lamp, the ballast comprising:
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a current-fed resonant inverter adapted for connection to the at least one gas discharge lamp and operable to provide a lamp power to the lamp, the lamp power having a first value and a second value, wherein the second value is less than the first value; and a load shed circuit coupled to the inverter and operable, in response to a load shed command, to cause to the inverter to reduce the lamp power from the first level to the second level, wherein; the inverter comprises; a pair of input terminals for receiving a source of substantially direct current (DC) voltage; a first output terminal and a return output terminal, wherein the first output terminal and the return output terminal are adapted for connection to the at least one gas discharge lamp; an output transformer having a primary winding and a secondary winding; and a first ballasting capacitor and a return ballasting capacitor, wherein the first ballasting capacitor is coupled between the secondary winding and the first output terminal, and the return ballasting capacitor is coupled between the secondary winding and the return output terminal; and the load shed circuit comprises; an isolation circuit coupled to a load shed receiver; and a bidirectional switch coupled to the isolation circuit, the bidirectional switch including first and second output connections, wherein the first output connection is coupled to the return output terminal, and the second output connection is coupled to a junction of the secondary winding and the return ballasting capacitor. - View Dependent Claims (8, 9, 10, 11)
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12. A ballast for powering a lamp load comprising at least one gas discharge lamp, the ballast comprising:
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a current-fed resonant inverter, comprising; a first output terminal and a return output terminal, wherein the first output terminal and the return output terminal are adapted for connection to a first gas discharge lamp; and a first ballasting capacitor and a return ballasting capacitor, wherein the first ballasting capacitor is coupled to the first output terminal, and the return ballasting capacitor is coupled to the return output terminal; and a load shed circuit adapted for connection to a load shed receiver, the load shed circuit having output connections coupled in parallel with the return ballasting capacitor, wherein the load shed circuit is operable; (i) in the absence of a load shed command, to provide an approximate short circuit between the output connections, thereby shunting the return ballasting capacitor and causing the inverter to operate the lamp at a first power level; and (ii) in response to a load shed command, to cease to provide an approximate open circuit between the output connections, thereby ceasing to shunt the return ballasting capacitor, thereby causing the inverter to operate the lamp at a second power level that is less than the first power level. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A ballast for powering at least one gas discharge lamp, the ballast comprising:
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an inverter, comprising; input terminals for receiving a source of substantially direct current (DC) voltage; an output transformer comprising a primary winding and a secondary winding; a first output terminal and a return output terminal adapted for connection to a first gas discharge lamp; a first ballasting capacitor coupled between the secondary winding and the first output terminal; and a return ballasting capacitor coupled between the secondary winding and the return output terminal; and a load shed circuit, comprising; an isolation circuit comprising an optocoupler, wherein the optocoupler is adapted for coupling to a load shed receiver; a bidirectional switch coupled to the isolation circuit, the bidirectional switch comprising; a first output connection and a second output connection, wherein the first output connection is coupled to the first output terminal, and the second output connection is coupled to a junction of the secondary winding and the return ballasting capacitor; and a first transistor and a second transistor, each transistor having a gate, a source, and a drain, wherein;
the gate of the first transistor and the gate of the second transistor are coupled to each other and to the isolation circuit;
the source of the first transistor is coupled to the source of the second transistor and to a circuit common;
the drain of the first transistor is coupled to the second output connection; and
the drain of the second transistor is coupled to the first output connection. - View Dependent Claims (23, 24, 25)
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Specification