Multiple voltage ballast

Abstract

A ballast and method for operating a ballast includes a switch or other circuit for connecting and disconnecting a voltage multiplier to a rectifier circuit. A control circuit for controlling the switch senses an input voltage and connects the voltage multiplier to the rectifier circuit when an input voltage falls below a selected voltage level.

1 - 19 . (canceled) 
     
     
         20 . A ballast circuit comprising:
 a full wave bridge circuit;   a voltage multiplier component coupled to the bridge circuit;   a switch for changing the full wave bridge circuit to a half wave bridge circuit; and   a control circuit coupled to the switch for changing a configuration of the switch at a selected voltage.   
     
     
         21 . The ballast circuit of  claim 20  wherein the switch is coupled to the voltage multiplier. 
     
     
         22 . The ballast circuit of  claim 21  further including a drive circuit for driving a load and wherein the switch is configured to couple the multiplier to the drive circuit substantially when the switch changes the full wave bridge to a half wave bridge. 
     
     
         23 . The ballast circuit of  claim 21  wherein the switch is a TRIAC. 
     
     
         24 . The ballast circuit of  claim 23  wherein the TRIAC is a first TRIAC and further including a second TRIAC wherein the second TRIAC is configured to be activated by an optical signal. 
     
     
         25 . The ballast circuit of  claim 20  wherein the control circuit is a voltage sensing circuit. 
     
     
         26 . The ballast circuit of  claim 25  wherein the voltage sensing circuit includes a capacitor. 
     
     
         27 . The ballast circuit of  claim 25  wherein the voltage sensing circuit includes a delay circuit. 
     
     
         28 . The ballast circuit of  claim 25  wherein the voltage sensing circuit includes an inverter to turn the switch on when the voltage sensed by the voltage sensing circuit is lower than a threshold voltage input to the full wave bridge circuit. 
     
     
         29 . The ballast circuit of  claim 20  further including a drive circuit for driving a load and wherein the control circuit is coupled to a circuit in the drive circuit. 
     
     
         30 . The ballast circuit of  claim 29  wherein the control circuit is coupled to a switch in an inductor circuit. 
     
     
         31 - 34 . (canceled) 
     
     
         35 . A method of controlling a ballast circuit the method comprising:
 applying an AC voltage to an input circuit, rectifying the AC voltage to a DC signal, changing a switch configuration when the AC voltage passes a first voltage level so that the DC signal is applied to a multiplier circuit.   
     
     
         36 . The method of  claim 35  wherein changing the switch configuration includes changing the AC voltage when the AC voltage is greater than 180 volts. 
     
     
         37 . The method of  claim 35  further including opening the switch when the AC voltage is greater than 180 volts. 
     
     
         38 . The method of  claim 35  further including rectifying AC voltage with a full wave rectifier circuit when the voltage is at a first level and the switch is in a first configuration, and rectifying an AC voltage with a half wave rectifier when the voltage is at a second level different from the first level, and the switch is in a second configuration. 
     
     
         39 . The method of  claim 35  further including changing the switch configuration using an optical input signal. 
     
     
         40 . The method of  claim 35  further including changing the switch configuration by changing the state of a TRIAC. 
     
     
         41 . The method of  claim 35  further including changing the switch configuration by changing the state of an optical TRIAC. 
     
     
         42 . The method of  claim 35  further including sensing a voltage level of the AC voltage at the input circuit. 
     
     
         43 . A method of controlling a ballast circuit, the method comprising applying an AC voltage to an input circuit of a normal power factor ballast coupled to a load, sensing the level of the AC voltage and changing a configuration of the ballast between the input circuit and the load as a function of the AC voltage level. 
     
     
         44 . The method of  claim 43  further including activating a multiplier circuit. 
     
     
         45 . The method of  claim 44  wherein activating the multiplier circuit deactivates a portion of a rectifier circuit. 
     
     
         46 . (canceled)