Inductive-resistive fluorescent apparatus and method

• US 6,100,653 A
• Filed: 12/22/1998
• Issued: 08/08/2000
• Est. Priority Date: 10/16/1996
• Status: Expired due to Term

• Current Assignee: Carol A. Lovell, Estate of Walter Carl Lovell
• Original Assignee: Tapeswitch Corporation (Inductotherm Group)
• Inventors: Lovell, Walter C., Duhon, Edward, Brooks, Sheldon B., Geiger, Dana
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Lee, Wilson
• Application Number:
  US09/218,473
• Time in Patent Office: 595 Days
• Field of Search: 315/291, 315/248, 315/246, 315/41, 315/39, 315/46, 315/224, 315/307
• US Class Current: 315/307
• CPC Class Codes: H01J 61/56 One or more circuit elements structurally associated with the lamp
• CPC Class Codes: H05B 41/16 in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies
• CPC Class Codes: H05B 41/24 in which the lamp is fed by high frequency ac, or with separate oscillator frequencyH05B41/26 takes precedence
• CPC Class Codes: H05B 41/2821 by means of a single-switch converter or a parallel push-pull converter in the final stage H05B41/285 takes precedence

Abstract

A fluorescent illuminating apparatus includes a translucent housing having a chamber within which a fluorescent medium is supported and electrical connections configured to provide an electrical potential across the chamber. An inductive-resistive structure is fixed sufficiently proximate to the housing to induce fluorescence in the fluorescent medium when an electric current is passed through the inductive-resistive structure while an electric potential is applied across the electrical connections of the housing. Preferred inductive structures for use with the present invention include elongate tape structures having a substrate with a conductive-resistive coating. A method of inducing fluorescence comprises passing a current through an inductive structure which is adjacent a fluorescing medium in an amount sufficient to induce fluorescence in the fluorescing medium in the presence of an electrical potential imposed on the fluorescing medium. An alternating current drive circuit for illuminating the fluorescent lamp includes a source of rippled/pulsed DC voltage, a polarity-reversing circuit and a controller connected to the polarity-reversing circuit which periodically generates a signal to reverse the polarity of the voltage applied to the lamp.

Claims

1. A fluorescent illuminating apparatus comprising:

a fluorescent lamp including;

a translucent housing having a chamber for supporting a fluorescent medium, said housing having first and second ends;

electrical connections on said housing to provide an electrical potential across said chamber, said connections being in the form of first and second electrical terminals;

a fluorescent medium supported in said chamber; and

first and second electrodes respectively at said first and second ends of said translucent housing, said first and second electrodes being respectively electrically interconnected with said first and second electrical terminals;

an inductive-resistive structure fixed sufficiently proximate said housing of said lamp to induce fluorescence in said fluorescent medium when an electric current is passed through said inductive-resistive structure while an electric potential is applied across said housing, said inductive-resistive structure having third and fourth electrical terminals thereon;

a source of rippled/pulsed DC voltage having two output terminals, a first of said output terminals of said source being electrically connected to said third electrical terminal, said source being electrically configured to produce a direct current exhibiting a rippled/pulsed voltage between said output terminals;

a polarity-reversing circuit having two input terminals and two output terminals, a first of said input terminals of said polarity-reversing circuit being electrically interconnected with said fourth electrical terminal, a second of said input terminals of said polarity-reversing circuit being electrically interconnected with a second of said output terminals of said source, a first of said output terminals of said polarity-reversing circuit being electrically interconnected with said first electrical terminal, a second of said output terminals of said polarity-reversing circuit being electrically interconnected with said second electrical terminal, said polarity-reversing circuit alternating a polarity of a voltage between the output terminals of said polarity-reversing circuit in response to at least one control signal; and

a controller operatively connected to said polarity-reversing circuit, said controller generating said at least one control signal for alternating the polarity of the voltage between said output terminals of said polarity-reversing circuit.

2. The apparatus of claim 1, wherein said polarity-reversing circuit is an H-bridge including first and second input connections, first and second output connections, and first and second control inputs, said H-bridge comprising:

first, second, third and fourth field effect transistor (FET) devices, each FET device having a gate terminal, a source terminal and a drain terminal, said drain terminals of said first and second FET devices being electrically interconnected together and forming said first input connection, said source terminals of said third and fourth FET devices being electrically interconnected together and forming said second input connection, said source terminal of said first FET device being electrically interconnected with said drain terminal of said third FET device and forming said first output connection, said source terminal of said second FET device being electrically interconnected with said drain terminal of said fourth FET device and forming said second output connection, said gate terminals of said first and fourth FET devices being electrically interconnected together and forming said first control input, and said gate terminals of said second and third FET devices being electrically interconnected together and forming said second control input.

3. The apparatus of claim 2, further comprising a sense circuit operatively connected to said fluorescent lamp, said sense circuit generating a sense signal corresponding to a measured current passing through said fluorescent lamp.

4. The apparatus of claim 3, further comprising a comparator having first and second inputs and an output, said first input being operatively connected to said sense signal, said second input being operatively connected to a reference signal corresponding to a predetermined lamp current, said comparator generating an output signal in response to a difference between said measured lamp current and said predetermined lamp current, said output signal being operatively connected to said controller.

5. The apparatus of claim 3, further comprising:

an analog-to-digital converter (ADC) operatively connected to said sense circuit, said ADC converting said sense signal into a digital representation of said measured lamp current; and

a comparator including first and second inputs and an output, said first input being operatively connected to said ADC and said second input being operatively connected to a digital representation of a predetermined reference lamp current, said comparator generating an output signal in response to a difference between said measured lamp current and said reference lamp current.

6. The apparatus of claim 5, wherein said controller is a microcontroller capable of running applications programs, and wherein said analog-to-digital converter and said comparator are embedded in said microcontroller.

7. The apparatus of claim 4, wherein said sense circuit comprises:

a transformer having a primary winding and a secondary winding, said primary winding being operatively connected in series with said fluorescent lamp; and

a rectifier operatively connected to the secondary winding of said transformer, said rectifier generating said sense signal.

8. The apparatus of claim 4, wherein said sense circuit comprises:

a sense resistor operatively connected between said second input connection of said H-bridge and said second output terminal of said source of rippled/pulsed DC voltage; and

a voltage subtracter-multiplier circuit having first and second inputs and an output, said first and second inputs of said subtracter-multiplier circuit being operatively connected across said sense resistor, said subtracter-multiplier circuit generating said sense signal in response to a voltage difference across said sense resistor.

9. A method of driving a fluorescent lamp, comprising the steps of:

providing a source of rippled/pulsed direct current (DC) electrical potential;

passing a current through an inductive-resistive structure adjacent said fluorescent lamp in an amount sufficient to induce fluorescence in the presence of said electrical potential imposed on said fluorescent lamp; and

delaying the application of said electrical potential to said fluorescent lamp for a predetermined time period until said electrical potential reaches a level appropriate for illuminating said fluorescent lamp.

10. The method of claim 9, further comprising the step of:

periodically reversing the polarity of the rippled/pulsed DC electrical potential applied to said fluorescent lamp, thereby producing an alternating current lamp drive voltage having a predetermined duty cycle.

11. The method of claim 10, further comprising the steps of:

measuring a current passing through said fluorescent lamp;

providing a control circuit which is responsive to said measured lamp current, said control circuit being capable of varying the duty cycle of said lamp drive voltage;

comparing said measured lamp current with a predetermined reference current indicative of a brightness level of said fluorescent lamp; and

varying the duty cycle of said lamp drive voltage until said measured lamp current is substantially equal to said reference current.

12. An alternating current drive circuit for illuminating a fluorescent lamp having a quantity of gaseous material contained therein, said drive circuit comprising:

a source of rippled/pulsed DC voltage having two output terminals, said source being electrically configured to produce a direct current exhibiting a rippled/pulsed voltage between said output terminals;

a polarity-reversing circuit having two input terminals and two output terminals, a first of said input terminals of said polarity-reversing circuit being electrically connected to a first of said output terminals of said source, a second of said input terminals of said polarity-reversing circuit being electrically connected to a second of said output terminals of said source, and said fluorescent lamp being electrically interconnected between said output terminals of said polarity-reversing circuit, said polarity-reversing circuit alternating a polarity of a voltage between the output terminals of said polarity-reversing circuit in response to at least one control signal; and

a controller operatively connected to said polarity-reversing circuit, said controller periodically generating said at least one control signal for alternating the polarity of the voltage between said output terminals of said polarity-reversing circuit thereby substantially eliminating gas migration of said gaseous material within said fluorescent lamp.

13. The apparatus of claim 12, wherein said polarity-reversing circuit is an H-bridge including first and second input connections, first and second output connections, and first and second control inputs, said H-bridge comprising:

first, second, third and fourth field effect transistor (FET) devices, each FET device having a gate terminal, a source terminal and a drain terminal, said drain terminals of said first and second FET devices being electrically interconnected together and forming said first input connection, said source terminals of said third and fourth FET devices being electrically interconnected together and forming said second input connection, said source terminal of said first FET device being electrically interconnected with said drain terminal of said third FET device and forming said first output connection, said source terminal of said second FET device being electrically interconnected with said drain terminal of said fourth FET device and forming said second output connection, said gate terminals of said first and fourth FET devices being electrically interconnected together and forming said first control input, and said gate terminals of said second and third FET devices being electrically interconnected together and forming said second control input.

14. The apparatus of claim 12, further comprising a sense circuit operatively connected to said fluorescent lamp, said sense circuit generating a sense signal corresponding to a measured current passing through said fluorescent lamp.

15. An alternating current drive circuit for illuminating a fluorescent lamp, said drive circuit comprising:

a source of rippled/pulsed DC voltage having two output terminals, said source being electrically configured to produce a direct current exhibiting a rippled/pulsed voltage between said output terminals;

a polarity-reversing circuit having two input terminals and two output terminals, a first of said input terminals of said polarity-reversing circuit being electrically connected to a first of said output terminals of said source, a second of said input terminals of said polarity-reversing circuit being electrically connected to a second of said output terminals of said source, and said fluorescent lamp being electrically interconnected between said output terminals of said polarity-reversing circuit, said polarity-reversing circuit alternating a polarity of a voltage between the output terminals of said polarity-reversing circuit in response to at least one control signal;

a controller operatively connected to said polarity-reversing circuit, said controller generating said at least one control signal for alternating the polarity of the voltage between said output terminals of said polarity-reversing circuit;

a sense circuit operatively connected to said fluorescent lamp, said sense circuit generating a sense signal corresponding to a measured current passing through said fluorescent lamp; and

a comparator having first and second inputs and an output, said first input being operatively connected to said sense signal, said second input being operatively connected to a reference signal corresponding to a predetermined lamp current, said comparator generating an output signal in response to a difference between said measured lamp current and said predetermined lamp current, said output signal being operatively connected to said controller.

16. The apparatus of claim 15, further comprising:

an analog-to-digital converter (ADC) operatively connected to said sense circuit, said ADC converting said sense signal into a digital representation of said measured lamp current; and

a comparator including first and second inputs and an output, said first input being operatively connected to said ADC and said second input being operatively connected to a digital representation of a predetermined reference lamp current, said comparator generating an output signal in response to a difference between said measured lamp current and said reference lamp current.

17. The apparatus of claim 16, wherein said controller is a microcontroller capable of running applications programs, and wherein said analog-to-digital converter and said comparator are embedded in said microcontroller.

18. The apparatus of claim 15, wherein said sense circuit comprises:

a transformer having a primary winding and a secondary winding, said primary winding being operatively connected in series with said fluorescent lamp; and

a rectifier operatively connected to the secondary winding of said transformer, said rectifier generating said sense signal.

19. The apparatus of claim 15, wherein said sense circuit comprises:

a sense resistor operatively connected between said second input connection of said H-bridge and said second output terminal of said source of rippled/pulsed DC voltage; and

a voltage subtracter-multiplier circuit having first and second inputs and an output, said first and second inputs of said subtracter-multiplier circuit being operatively connected across said sense resistor, said subtracter-multiplier circuit generating said sense signal in response to a voltage difference across said sense resistor.