High frequency inductive lamp and power oscillator

• US 6,313,587 B1
• Filed: 11/05/1999
• Issued: 11/06/2001
• Est. Priority Date: 01/13/1998
• Status: Expired due to Fees

• Current Assignee: Fusion Lighting, Inc.
• Original Assignee: Fusion Lighting, Inc.
• Inventors: Ola, Samuel A., Dymond, Lauren E. Jr., Grimm, William G., Turner, Brian P., Simpson, James E., Tsai, Peter, Kirkpatrick, Douglas A., Gitsevich, Aleksandr, MacLennan, Donald A., Kipling, Kent, Trimble, William C.
• Primary Examiner(s): Philogene, Haissa
• Application Number:
  US09/434,310
• Time in Patent Office: 732 Days
• Field of Search: 315/248, 315/307, 315/267, 315/344, 315/209 R, 315/224, 315/244, 315/283, 315/276, 315/DIG. 7, 315/157
• US Class Current: 315/248
• CPC Class Codes: H01J 61/025 Associated optical elements
• CPC Class Codes: H01J 61/12 Selection of substances for gas fillings; Specified operating pressure or temperature
• CPC Class Codes: H01J 61/125 having an halogenide as principal component
• CPC Class Codes: H01J 61/52 Cooling arrangements; Heating arrangements; Means for circulating gas or vapour within the discharge space heating or cooling arrangements to promote ionisation for starting H01J61/54
• CPC Class Codes: H01J 61/523 Heating or cooling particular parts of the lamp
• CPC Class Codes: H01J 65/044 the field being produced by a separate microwave unit
• CPC Class Codes: H01J 65/048 the field being produced by using an excitation coil
• 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: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and I or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to adjust the driving frequency of the oscillator.

Claims

1. A lamp apparatus, comprising:

a discharge lamp;

an RF power source connected to the discharge lamp for providing RF power at a driving frequency; and

a control circuit for controlling the driving frequency of the RF power source,

wherein the discharge lamp operates in a first tuning state during lamp ignition and a second tuning state during lamp operation, and wherein the control circuit comprises a timing circuit which sets the driving frequency in accordance with the first tuning state for a pre-determined period of time and thereafter sets the driving frequency in accordance with the second tuning state.

2. A lamp apparatus, comprising:

a discharge lamp;

an RF power source connected to the discharge lamp for providing RF power at a driving frequency;

a control circuit for controlling the driving frequency of the RF power source; and

a detector for detecting a lamp operating parameter, wherein the detector is configured to provide a signal to the control circuit in accordance with the detected parameter.

3. The lamp apparatus as recited in claim 2, wherein the lamp operating parameter comprises one of a light output level, an RF power reflection, and a light color.

4. The lamp apparatus as recited in claim 2, wherein the detector comprises a photo-detector positioned to receive light from the discharge lamp, and wherein the lamp operating parameter comprises one of a light output level and a light color.

5. The lamp apparatus as recited in claim 2, wherein the detector comprises a circulator connected in between the RF power source and the discharge lamp, and wherein the lamp operating parameter corresponds to an RF power reflection.

6. The lamp apparatus as recited in claim 2, wherein the detector comprises a six port directional coupler connected in between the RF power source and the discharge lamp and configured to detect forward and reflected power, and wherein the lamp operating parameter corresponds to said forward and reflected power.

7. A lamp apparatus, comprising:

a discharge lamp;

an RF power source connected to the discharge lamp for providing RF power at a driving frequency; and

a control circuit for controlling the driving frequency of the RF power source,

wherein the RF power source comprises an oscillator and wherein the control circuit is configured to delay initiation of active control until after the oscillator starts.

8. A lamp apparatus, comprising:

a discharge lamp;

an RF power source connected to the discharge lamp for providing RF power at a driving frequency; and

a control circuit for controlling the driving frequency of the RF power source,

wherein the RF power source comprises an oscillator and wherein the control circuit is configured to step an operating frequency of the oscillator through a range of frequencies to find a resonant frequency.

9. A lamp apparatus, comprising:

a discharge lamp;

an RF power source connected to the discharge lamp for providing RF power at a driving frequency; and

a control circuit for controlling the driving frequency of the RF power source,

wherein the RF power source comprises an oscillator and wherein the control circuit is configured to adjust an operating frequency of the oscillator to minimize reflected power.

10. A method of operating a lamp apparatus which includes a discharge lamp and a variable frequency RF power source connected to the discharge lamp, the method comprising:

determining an amount of RF power reflected from the discharge lamp back to the RF power source; and

adjusting the frequency of the RF power source to reduce the amount of reflected RF power detected.

11. The method of operating a lamp apparatus as recited in claim 10, wherein the step of adjusting comprises:

(a) adjusting the frequency of the RF power source within a pre-determined range until the discharge lamp is determined to be near a resonant frequency of the discharge lamp; and

(b) subsequently adjusting the frequency of the RF power source until the amount of reflected RF power is detected to be below a pre-determined threshold.

12. The method of operating a lamp apparatus as recited in claim 11, wherein each adjustment of the frequency of the RF power source is maintained for a pre-determined period of time, and wherein the amount of adjustment made in step (a) is relatively larger than the amount of adjustment made in step (b).

13. The method of operating a lamp apparatus as recited in claim 10, wherein the steps of determining and adjusting comprise:

(a) setting the frequency of the RF power source at one end of a pre-determined frequency range;

(b) delaying any adjustment of the RF power source frequency for a period of time;

(c) determining if RF power is being provided to the discharge lamp, and, if not, returning to step (b);

(d) determining an amount of reflected RF power;

(e) in approximately equal time intervals;

(1) if the amount of reflected RF power is below a first threshold, returning to step (e) without adjusting the frequency of the RF power source, where the first threshold correspond to a minimum reflected RF power condition;

(2) adjusting the frequency in accordance with a pre-determined direction of adjustment and a pre-determined amount of adjustment, wherein if the adjustment causes the frequency of the RF power source to go outside of the pre-determined range, the frequency of the RF source is set at one end of the pre-determined range;

(3) determining a new amount of reflected RF power and comparing the newly determined amount with the immediately previously determined amount;

(4) if the amount of reflected power is above a second threshold or if the change in the amount of reflected power is less than a third threshold, returning to step (e) for further adjustment of the frequency of the RF power source, where the second threshold corresponds to a relatively high amount of reflected RF power indicating a poor match condition and wherein the third threshold corresponds to an insignificant amount of change of the amount of reflected RF power; and

(5) if the change in the amount of reflected RF power is above a fourth threshold, reducing the pre-determined amount of adjustment made in step (2) and returning to step (e), where the fourth threshold corresponds to a significant amount of change in the reflected RF power indicating the frequency of the RF power source is near to a resonant frequency of the discharge lamp.