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.

Description

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic of a current limiting device for an inverter of an EL lamp, provided in accordance with the principles of the invention.

Claims

1. A current limiting device comprising: a constant current source circuit constructed and arranged to be connected to a direct current input voltage source and to regulate electrical current, anda resonance source circuit receiving current from the current source circuit and being constructed and arranged to be electrically connected with an electro-luminescent (EL) lamp so as to receive alternating current,wherein the constant current source circuit and the resonance source circuit are constructed and arranged such that when current flows from the 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.

2. The device of claim 1, wherein the constant current source is one of a linear or high frequency switching type circuit.

3. The device of claim 1, wherein the constant current source circuit is a constructed and arranged to maintain a substantially constant direct current.

4. The device of claim 1, wherein the constant current source circuit includes 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.

5. The device of claim 4, wherein the resonance source circuit includes a three phase transformer, a first phase is connected to an output of the current source circuit, a current limiting resistor and the emitter of the transistor, a second phase is coupled to the base of the transistor through a capacitor, and the third phase is a separate winding constructed and arranged to be electrically connected to the EL lamp and output ground.

6. The device of claim 1, in combination with the EL lamp, wherein the resonance source circuit includes a transformer with a separate winding electrically connected to the EL lamp and output ground.

7. The device of claim 1, wherein the maximum peak current received by the user is about 0.2 mA.

8. The device of claim 1, wherein the device is part of an inverter for powering an EL lamp.

9. A current limiting device comprising: means, constructed and arranged to be connected to a direct current input voltage source, for regulating electrical current, andmeans, receiving current from the means for regulating, for electrically connecting with an electro-luminescent (EL) lamp so that the EL lamp receives alternating current,wherein the means for regulating and the means for electrically connecting are constructed and arranged such that when current flows from the means for regulating to the means for electrically connecting 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.

10. The device of claim 9, wherein the means for regulating is one of a linear or high frequency switching type circuit.

11. The device of claim 9, wherein the means for regulating is constructed and arranged to maintain a substantially constant direct current.

12. The device of claim 11, wherein the means for regulating is a constant current source circuit including 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 constant current source circuit.

13. The device of claim 12, wherein the means for electrically connecting includes a three phase transformer, a first phase is connected to an output of the current source circuit, a current limiting resistor and the emitter of the transistor, a second phase is coupled to the base of the transistor through a capacitor, and the third phase is a separate winding constructed and arranged to be electrically connected to the EL lamp and output ground.

14. The device of claim 9, in combination with the EL lamp, wherein the means for electrically connecting includes a transformer with a separate winding electrically connected to the EL lamp and output ground.

15. The device of claim 9, wherein the maximum peak current received by the user is about 0.2 mA.

16. The device of claim 9, wherein the device is part of an inverter for powering an EL lamp.

17. A method of limiting current of an inverter associated with an electro-luminescent (EL) lamp, the method including: providing an inverter constructed and arranged to convert direct current input voltage to an alternating current output voltage to power an EL lamp,providing a current limiting circuit within the inverter, andensuring that when the EL lamp is powered by the inverter, the current limiting circuit limits a maximum peak current received by a user contacting an output of the inverter or contacting the EL lamp to less than about 0.7 mA.

18. The method of claim 17, wherein the current limiting circuit includes a constant current source circuit and a resonance source circuit fed by the current source circuit, the constant current source circuit being constructed and arranged to keep the direct current at a substantially constant valve, the resonance source circuit including a transformer having a winding that is electrically connected separately with the EL lamp such that when the user makes contact with the inverter output or the EL lamp, current will not draw from the constant current source circuit to the user.

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, andas 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.