HK1121286B - Inductively powered gas discharge lamp - Google Patents

Description

Inductively operated gas discharge lamp

Priority requirement

This application claims priority from U.S. provisional application No 60/705,012 entitled "Coil Arrangement for aGas Discharge Lamp" filed on 3.8.2005.

Background

Gas discharge lamps are very popular in providing illumination. For example, they are used in offices, homes, factories, auditoriums, and passenger aircraft.

One of the most functional types of gas discharge lamps is the inductive drive described in U.S. Pat. No. 6,731,071 entitled "inductively powered Lamp Assembly". The lamp includes a coil within the envelope to drive each filament or electrode. Each coil is inductively coupled to a power source within the socket (texture). Optionally, the filaments are provided with a preheating circuit to preheat the filaments before the lamp is started. The circuit includes a switch that closes to provide preheat current to the filaments. After the filaments are sufficiently preheated, the switch is opened to provide a voltage for igniting (strike) the lamp.

In non-inductively driven lamps (i.e., including conventional contact pins extending from the lamp envelope), heating of the filament is common. Heating of the filaments reduces the voltage required to ignite and maintain illumination of the lamp. In addition, heating of the filament allows increased control over dimmability of the lamp. Changing the brightness of a fluorescent lamp requires changing the voltage applied to the lamp. However, reducing the voltage applied to the lamp reduces the current through the filament, thus changing the temperature of the filament. If the filament temperature drops too low, the lamp will extinguish because the arc between the filaments cannot be maintained. Accordingly, ballast circuits have been developed to dim fluorescent lamps by increasing the current through the filaments as the voltage applied to the lamp drops. These circuits enable the lamp to be dimmed over a wide range. Unfortunately, this solution is not directly suitable for inductively driven lamps.

Inductively driven gas discharge lamps have the ability to provide a filament.

Disclosure of Invention

The aforementioned problems are solved by a gas discharge lamp comprising a driving induction coil for driving the lamp and a heating induction coil for heating the filament or electrode. As disclosed, the first and second drive coils provide power to the first and second filaments of the lamp in a conventional manner. In addition, the first and second heater coils supply heating currents to the first and second electrodes so that the filament can be preheated before a lighting voltage is applied to the filament through the driving coils.

In a further aspect of the invention, the drive coils and the heating coils are controlled in a coordinated manner to provide dimming. The voltage applied to the electrodes by the driving coils is inversely proportional to the current applied to the electrodes by the heating coils. Thus, the lamp is inductively driven and dimmable.

These and other objects, advantages and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings.

Drawings

FIG. 1 is an inductively coupled gas discharge lamp;

fig. 2 shows an inductive connector portion of a gas discharge lamp;

fig. 3 shows a circuit diagram of a gas discharge lamp and a lamp holder;

fig. 4 shows a socket connector for a gas discharge lamp;

FIG. 5 shows an end view of a gas discharge lamp;

FIG. 6 shows an additional configuration of a coil for a gas discharge lamp;

FIG. 7 shows an apparatus for assisting in the alignment of a gas discharge lamp;

fig. 8 shows a circuit for driving an inductively coupled gas discharge lamp; and

fig. 9 shows a second circuit for driving an inductively coupled gas discharge lamp.

Detailed Description

A gas discharge lamp constructed in accordance with the present embodiment of the invention is illustrated in the drawings and is indicated at 10.

As shown in fig. 1, the lamp 10 has a pair of inductive connector portions 11, 12 on an envelope 15. The inductive connector portion 12 has a power coil 14 and a heater coil 16. The inductive connector portion 11 is similar to the inductive connector portion 12. The conductive strip 18 connects the inductive connector portion 11 to the inductive connector portion 12. Although the physical embodiment of the lamp 10 illustrated is a straight tube, the lamp may have any kind of physical construction, as is known in the art.

A conductor 18 is formed on the interior of the lamp 10. According to one embodiment, the conductor 18 is a strip of conductive paint applied to the inside of the lamp 10. According to another embodiment, the conductor 18 is a metal strip attached to the inside of the lamp 10 with an adhesive. A layer of insulating material may then be applied over the conductors 18. Alternatively, the conductor 18 may be a conductive wire extending from the inductive connector portion 11 to the inductive connector portion 12 inside the lamp 10 or along the outside of the lamp 10.

When the inductive connector portions 11, 12 are formed entirely within the lamp 10, then the lamp 10 may be completely sealed. Alternatively, the inductor connector portions 11, 12 may be placed on the lamp tube in a manner similar to that used in end connectors of conventional gas discharge lamps.

The inductive connector portion 12 is shown in more detail in figure 2. The drive coil 14 is connected to the heater coil 16 through a capacitor 20. The heater coil 16 is connected to a filament 22.

Fig. 3 shows a schematic circuit diagram for the lamp 10 in a lamp holder. The filaments 22, 24 are connected in series with the heater coils 16, 28. The drive coils 14, 32 are connected to the filaments 22, 24 through capacitors 20, 36. The drive coils 14, 32 are electrically coupled to each other by the conductor 18.

The ballast heater coils 38, 40 inductively provide power to the heater coils 16, 28, while the ballast power coils 42, 44 inductively provide power to the power coils 14, 32. The ballast power coils 42, 44 and ballast heater coils 38, 40 are connected to an inverter 46, and the inverter 46 is connected to a power source 48. The inverter 46 and power supply 48 may be any known inverter and power supply gas discharge lamp. For example, the inverter 46 may be a two transistor half bridge inverter.

In operation, the inverter 46 first supplies power to the ballast heater coils 38, 40 to heat the filaments 22, 24. After a predetermined period of time, the inverter 46 reduces power to the ballast heater coils 38, 40 and energizes the ballast power coils 42, 44, causing an arc between the filaments 22 and 24. After ignition, the power supplied by the inverter 46 is reduced for steady state operation of the lamp 10.

Preheating the filaments extends the life of the filaments and thus the life of the lamp. The preheat current is typically the highest level of current experienced by the filament. After preheating, the preheating current can be almost completely eliminated if a full operating voltage is applied to the lamp.

Because the heater coils 16, 28 are coupled across the filaments 22, 24, heating of the filaments is separate from the power supplied to the filaments to maintain the arc within the lamp. Thus, a control circuit (not shown) is used to regulate the heating of the filament for different situations. The construction and design of the control circuit will be apparent to those skilled in the art in light of this disclosure.

In the present embodiment, the control circuit enables dimming of the lamp. As is well known, a gas discharge lamp will extinguish if both the voltage between the filaments and the filament temperature drop to a level at which the arc within the lamp cannot be maintained. By heating the filaments, an arc within the gas discharge lamp can be maintained even if the potential between the two filaments is reduced.

During lamp dimming, the resonant circuit will operate substantially non-resonant to reduce the voltage across the lamp. By maintaining or increasing the filament heating current while decreasing the lamp voltage, it is possible to have a very low dimming level. If additional stability or dimming range is required because of different lamp types, the preheat may be increased as the lamp voltage decreases to provide stable non-flickering light.

In addition, filament heating during steady state operation may vary as the lamp ages, thus increasing the effective life of the lamp. As the lamp ages, the filament sputters and removes the coating to the wall of the lamp. This substance on the lamp wall adsorbs mercury and causes contamination. When mercury is reduced or the lamp interior gas is contaminated, the lamp becomes difficult to start and the stability of the lamp at normal operating voltages may be adversely affected. By sensing the lamp operating voltage, the control system can adjust to changes in lamp impedance. For example, when it is determined that the lamp is difficult to start or unstable in the run mode, the system may change the heating pattern by increasing the preheat current or preheat duration. This increase in time or preheat current will help to adjust for system instability.

According to an embodiment of the invention, the ignition voltage at which an arc is initiated between the first electrode and the second electrode is measured, for example when it is determined that the lamp is difficult to start or unstable in the run mode; and optionally to change the heating profile as a function of the ignition voltage for use in subsequent lamp starting.

The ballast power coil 44 and the ballast heater coil 38 are included within the fixture connector 50. Similarly, ballast power coils 42 and ballast heater coils 40 are included within fixture connector 52.

The fixture connector 52 is shown in fig. 4. The fixture connector 52 includes a ballast heater coil 40 coaxial with a ballast power coil 42. The ballast heater coil 40 and the ballast power coil 42 are coaxial. Thus, the fixture connector 52 slides over the inductive connector 12, thereby placing the ballast heater coil 40 near the heater coil 28 and the ballast power coil 42 near the power coil 32.

As shown in fig. 2, the drive coil 14 is positioned circumferentially along the outer periphery of the outer wall of the enclosure 15. The drive coil 14 may be on the inside of the enclosure 15 or on the outside of the enclosure 15. The heater coil 16 is placed in or out of a plateau 17 extending from the capsule 15. The plateau 17 is generally cylindrical and coaxial with the outer wall portion 19 of the envelope 15. A different configuration than the coaxial arrangement of the ballast heater coils 38 and the ballast power coils 42 may be satisfactory. An example is shown in fig. 5.

Fig. 5 shows an end view of an alternative embodiment 10 ' of the lamp, in which the drive coil 14 ' and the heater coil 16 ' are coplanar and placed within the top of the envelope 15. Similarly, a socket for a socket connector would have a coplanar ballast drive coil and a coplanar ballast heater coil.

FIG. 6 shows an end view of another alternative embodiment 10 "of a lamp including a plurality of heating coils. The drive coil 14 "is positioned around the periphery of the end of the lamp 10. The heater coils 16a ", 16 b", 16c ", and 16 d" are located within the power coil 14 ". The drive coil 14 "and the heater coils 16 a", 16b ", 16 c", and 16d "are coplanar. In this configuration, the heater coils 16a ", 16 b", 16c ", and 16 d" are connected in parallel with the filament.

Fig. 7 shows an arrangement for maintaining alignment of the ballast power coils, ballast heater coils, heater coils and power coils. The socket connectors 80, 82 include magnetic materials 84, 86. The sensing conductor parts 11, 12 comprise magnetic material 92, 94. The magnetic materials 84, 86, 92, 94 are a combination of magnets and other magnet materials to cause alignment.

Alternatively or in addition to the magnet, the inductor conductor part and the socket connector are provided with an interlocking key mechanism. According to another embodiment, the socket connectors 80, 82 comprise springs or other resilient mechanisms adapted to hold the lamp 10 in place relative to the socket connectors 80, 82. It will be apparent to those skilled in the art that many different mechanisms may be used to hold the lamp 10 in place relative to the fixture connectors 80, 82 such that the ballast power coils 42, 44 are proximate the power coils 32, 14, respectively, and the ballast heater coils 40, 38 are proximate the heater coils 28, 16, respectively.

Fig. 8 shows an alternative circuit configuration for driving an inductively coupled gas discharge lamp. In this configuration, the microcontroller 100 is coupled to and controls two driver circuits 102, 104. The driver circuit 102 is used to drive the coils 42, 44, while the driver circuit 104 is used for the heater coils 38, 40. When the power supplied by the driver circuit 102 to the drive coils 42, 44 is reduced, the driver circuit 104 increases the power supplied to the heater coils 38, 40, thus providing additional heating to the electrodes.

Fig. 9 shows a further alternative circuit for driving an inductively coupled gas discharge lamp. The microcontroller 110 is coupled to and controls the driver circuit 112 and the switch 116. The switch 116 couples the power provided by the driver circuit 112 to the drive coils 42, 44 and the heater coils 38, 40. The amount of power provided to the drive coils 42, 44 or the heater coils 38, 40 is controlled by the microcontroller 110. When the amount of power supplied to the drive coils 42, 44 decreases, the amount of power supplied to the heater coils 38, 40 increases. The increased power to the heater coil 118 increases the temperature of the lamp electrodes.

What has been described above are those current embodiments of the present invention. Various substitutions and changes may be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles "a," "an," "the," or "said," is not to be construed as limiting the element to the singular.

Claims (36)

1. A gas discharge lamp comprising:

an envelope containing a discharge gas;

a first electrode within the enclosure;

a second electrode within the envelope;

a first inductive drive coil coupled to the first electrode capable of receiving power from an inductive power supply providing power to the first electrode; and

a first induction heater coil connected to the first electrode capable of applying a heating current to the first electrode, the first induction heater coil capable of receiving power from an induction power source,

wherein the first induction heater coil and the first induction drive coil are coplanar.

2. The gas discharge lamp of claim 1, further comprising: a capacitor in series with the first inductive drive coil.

3. The gas discharge lamp of claim 2, further comprising: a second inductive drive coil connected to the second electrode and capable of receiving power from an inductive power supply.

4. The gas discharge lamp of claim 3, further comprising: a second induction heater coil connected to the second electrode and capable of receiving power from an induction power source.

5. The gas discharge lamp of claim 1, further comprising: a capacitor coupled to the first inductive drive coil, the first inductive drive coil and the capacitor forming a resonant circuit.

6. The gas discharge lamp of claim 5, wherein the resonant circuit is one of a series resonant circuit and a parallel resonant circuit.

7. The gas discharge lamp of claim 4 wherein the first inductive drive coil, the second inductive drive coil, the first inductive heater coil, the second inductive heater coil, and the capacitor are included within the envelope such that the envelope is not penetrated.

8. The gas discharge lamp of claim 1 wherein the first inductive heater coil is included within an outer perimeter of the first inductive drive coil.

9. The gas discharge lamp of claim 3 wherein the first induction heater coil is included within an outer perimeter of the first induction drive coil and the second induction heater coil is included within an outer perimeter of the second induction drive coil.

10. The gas discharge lamp of claim 3, further comprising a conductor connecting the first inductive drive coil to the second inductive drive coil.

11. The gas discharge lamp of claim 10 wherein the conductor is within the envelope.

12. The gas discharge lamp of claim 11 wherein the conductor is a film of conductive material attached to the envelope.

13. A gas discharge lamp comprising:

a sealed envelope containing a discharge gas;

a first electrode and a second electrode within the enclosure;

first and second drive coils coupled to the first and second electrodes, respectively, the first and second drive coils adapted to supply power to the first and second electrodes, respectively; and

a first heating coil and a second heating coil coupled to the first electrode and the second electrode, respectively, the first heating coil and the second heating coil being adapted to supply heating currents to the first electrode and the second electrode, respectively,

wherein the first heating coil and the first driving coil are coplanar.

14. The gas discharge lamp of claim 13, further comprising a first magnetic material proximate the first electrode and a second magnetic material proximate the second electrode.

15. The gas discharge lamp of claim 14, further comprising a conductive material connecting the first drive coil to the second drive coil.

16. The gas discharge lamp of claim 15 wherein the conductive material is secured to the envelope.

17. The gas discharge lamp of claim 13 wherein the first drive coil is on an outer wall of the envelope.

18. The gas discharge lamp of claim 17, wherein the gas discharge lamp has a mesa portion that is substantially coaxial with an outer wall of the envelope, and a first heater coil for heating the first electrode is positioned in the mesa portion.

19. A method of operating a dimmable inductively driven gas discharge lamp, comprising:

providing a gas discharge lamp having an envelope containing a discharge gas, the lamp further having a first electrode and a second electrode, a first drive coil coupled to the first electrode, a second drive coil coupled to the second electrode, a first heater coil coupled to the first electrode, and a second heater coil coupled to the second electrode;

providing power to the first and second drive coils sufficient to ignite an arc between the first and second electrodes;

reducing power to the first drive coil and the second drive coil to dim the lamp; and

power is added to the first heater coil and the second heater coil to increase the current through them, and thus increase the temperature of the first electrode and the second electrode,

wherein the first heater coil and the first drive coil are coplanar.

20. The method of claim 19, wherein power is switched between driving the lamp and heating the first and second electrodes.

21. A method of operating a gas discharge lamp comprising:

providing a gas discharge lamp having an envelope containing a discharge gas, the gas discharge lamp further having a first electrode and a second electrode, a first drive coil connected to the first electrode, a second drive coil connected to the second electrode, a first heater coil for heating the first electrode, and a second heater coil for heating the second electrode;

applying power to the first heater coil and the second heater coil to provide a heating pattern to the first electrode and the second electrode;

applying power to the first drive coil and the second drive coil to provide a voltage sufficient to ignite the lamp;

measuring a lighting voltage at which an arc is initiated between the first electrode and the second electrode; and

selectively varying the heating profile as a function of the ignition voltage, for use in subsequent lamp starting,

wherein the first heater coil and the first drive coil are coplanar.

22. The method of claim 21, further comprising: the lighting voltage is stored.

23. The method of claim 22, further comprising: the previous lighting voltage is compared with the current lighting voltage.

24. A lamp holder for an inductively driven gas discharge lamp having a first electrode and a second electrode, the lamp holder comprising:

a first lamp holder part adapted to receive a first part of the lamp, said first lamp holder part having a first driving primary coil adapted to supply power to a first electrode for operating the gas discharge lamp, and a first heating primary coil adapted to supply power to the first electrode for heating the first electrode; and

a second lamp holder part adapted to receive a second part of the lamp, said second lamp holder part having a second driving primary coil adapted to supply power to the second electrode and to operate the gas discharge lamp, and a second heating primary coil adapted to supply power to the second electrode to heat the second electrode,

wherein the first heating primary coil and the first driving primary coil are coplanar.

25. The lamp socket of claim 24, wherein the first driver primary coil is disposed circumferentially around an outer periphery of the first portion.

26. The lamp socket of claim 25, wherein the second portion has a top portion and the first heating primary is located on the top portion.

27. The lamp socket of claim 25, wherein the first heating primary coil is disposed around the outer periphery of the second portion.

28. A gas discharge lamp comprising:

an enclosure;

a first electrode within the enclosure;

a drive coil for inductively receiving power from the first primary coil, the drive coil being connected to the first electrode; and

a heater coil for inductively receiving power from the second primary coil, the heater coil being connected to the first electrode,

wherein the drive coil and the heater coil are coplanar.

29. The gas discharge lamp of claim 28 wherein the envelope has a top portion and the drive coil is located within the top portion.

30. The gas discharge lamp of claim 29, wherein the heater coil is located within the top portion.

31. The gas discharge lamp of claim 30, wherein the power coil is coaxial with the heater coil.

32. The gas discharge lamp of claim 28, wherein the envelope has a curved wall and the drive coil is arranged circumferentially around the curved wall.

33. The gas discharge lamp of claim 28, wherein the gas discharge lamp has a first cylindrical portion and a second cylindrical portion, the first cylindrical portion being coaxial with and separate from the second cylindrical portion.

34. The gas discharge lamp of claim 33, wherein the drive coil is circumferentially disposed about the first cylindrical portion.

35. The gas discharge lamp of claim 34, wherein the heater coil is disposed around the second cylindrical portion.

36. The gas discharge lamp of claim 35, wherein the first cylindrical portion is longer than the second cylindrical portion.