Limited current circuit for electro-luminescent lamp inverter

Abstract

A current limiting device includes a constant current source circuit constructed and arranged to be connected to a direct current input voltage source and to regulate electrical current and a resonance source circuit receiving current from the constant current source circuit. The resonance source circuit is constructed and arranged to be electrically connected with an electro-luminescent (EL) lamp so that the EL lamp receives alternating current. The constant current source circuit and the resonance source circuit are constructed and arranged such that when current flows from the constant current source circuit to the resonance source circuit and to the EL lamp, a maximum peak current received by a user contacting an output of the device or contacting the EL lamp is less than about 0.7 mA.

1 - 18 . (canceled) 
   
   
       19 . A method of compensating for decay of an electro-luminescent (EL) lamp, the method including:
 providing an inverter having a constant current limiting circuit constructed and arranged to be connected to a direct current input voltage source and to regulate electrical current, the inverter also including a resonance source circuit receiving an output voltage from the constant current source circuit, the resonance source circuit providing an alternating current output voltage to the EL lamp, and   as the EL lamp ages, increasing the output voltage from the constant current source circuit and thus the output voltage from the resonance source circuit, thereby compensating for a decay of the EL lamp.   
   
   
       20 . The method of  claim 19 , further including changing a current setting of the constant current source circuit to dim the output voltage of the resonance source circuit. 
   
   
       21 . The method of  claim 19 , wherein the resonance source circuit includes a transformer with a separate winding electrically connected to the EL lamp and output ground, 
   
   
       22 . The method of  claim 19 , wherein the constant current source circuit includes a transistor, an emitter of the transistor is connected to the input voltage source, a current sensor is connected to a collector of the transistor, a first amplifier is connected with the current sensor to amplify a pass current, a resistance divider, establishing a reference voltage, is connected to a positive input of a second amplifier, a negative input of the second amplifier being connected to an output of the first amplifier, a base of the transistor is connected to an output of the second amplifier to complete a constant current feedback loop defined by the current source circuit.