WO2004114362A2 - Low voltage gas discharge lamp - Google Patents

Abstract

A low cost reflector compact fluorescent lamp with extended long life electronic ballast is disclosed to operate satisfactorily at an elevated temperature range in insulated ceiling and airtight fixtures such as downlight to replace highly inefficient, unreliable, reflector lamps presently used. The construction of pyramid type top spiral compact fluorescent lamp with special cathode material, filled gas, advanced amalgam, protected multi layered phosphor could operate with a suitable single stage, multi resonant, high power factor, dimming electronic ballast. Technology used to achieve low cost and low profile characteristics of the ballast is single stage, zero energy storage inverter, complementary drive, and high displacement Piezoelectric transformer components.

Description

LOW VOLTAGE GAS DISCHARGE LAMP Cross-Reference to Related Applications

This application claims priority of Indian Patent Application Serial No. 621/MUM/2003, filed June 13, 2003, the disclosure of which is hereby expressly incorporated herein by reference. Field of the Invention

The present invention generally relates to a low voltage, gas discharge lamp, and more particularly to a low cost, pyramid type, top spiral compact fluorescent lamp suitable for high temperature environments such as in insulated ceiling and airtight light fixtures. Background of the Invention

Utility companies and energy providers set strict requirements for power quality drawn from the lighting products. Electronic ballasts for gas discharge lamps should typically satisfy the following requirements: (i) Power-factor (PF) of at least 0.9; (ii) THD of less than 33 percent; (iii) Lamp current crest factor of less than 1.7; (iv) Flicker of less than 2 percent; (v) Constant power delivery over the entire cycle of the power line; and

(vi) Low inrush current to allow large number of lamps to operate simultaneously without affecting the circuit breaker and without fuse overrating.

Conventional off-line rectifiers have a very large electrolytic capacitor located beyond a diode rectifier circuit which function as smoothing filters. These electrolytic capacitors cause harmonic distortion of the current waveforms as the capacitors charge. This charging time, or conduction angle, is very small if a large capacitor is used. Moreover, the capacitor should charge in a short period of time. This causes a large current output from the rectified power line source. These current spikes increase the harmonic content of the power source, and when large number of lamps using such inefficient ballasts are operated from the power line, this increased harmonic distortion causes a poor power factor in the power source. Electricity supply authorities do not accept such situation because it interferences with other electrical circuits.

Many prior art techniques use single stage power factor corrector circuits to reduce cost by providing a high frequency feedback from output to input of the power converter. A large circulating current within the oscillator circuit, however, causes large amount of power dissipation in the switching components.

Two different types of ballasts are presently used to drive fluorescent lamps - Magnetic and Electronic. The ballasts function as current regulators to control the power delivered to lamps. Electronic ballasts are essentially high frequency inverters which drive the lamp. Fluorescent lamps with electronic ballasts typically deliver more light output than lamps using magnetic ballasts because the electronic ballasts operate at higher frequencies. Consequently, they have higher efficiency and conserve energy without causing appreciable flicker.

Conventional techniques for improving power factor include passive power factor correction using wave shaping technologies. Such techniques are inexpensive and reliable, but require the use of a very large inductor. Active power factor correction circuits use boost converters, which require elaborate noise filtering and complex and expensive circuits. Additionally, conventional single stage converters are used for low cost electronic ballasts. In such single stage resonant oscillatory circuits, a portion of the resonant energy is fed back from the output to the input of the converter to achieve a near sinusoidal current from the power line. This, however, results in very high circulating currents causing high power dissipation in the inverter circuit.

Accordingly, it is desireable to provide a simple, low cost, single stage or single chip electronic ballast and a suitable lamp to achieve high power factor, low distortion, dimming and multiple power output that satisfies industry requirements. It is further desireable to provide a configuration that is adaptable to all power line voltages and all kind of lamps. It is also desirable to provide a low profile suitable for conventional lamp holders. Summary of the Invention

The present invention provides an electronically controlled, high efficiency, long life compact fluorescent reflector lamp to replace conventional incandescent and fluorescent reflector lamps of different wattages used today, for example, in high temp environments of insulated ceiling and air tight light fixtures. The present invention further provides a high power factor, low cost dimmable electronic ballast to operate the present lamp without an electrolytic capacitor and withstand high temperature operation at low cost. In one embodiment, a configuration according to the present invention meets power quality standards such as high power factor of more than 0.95, low distortion of less than 10 percent, wide dimming range, high efficiency, long life, low inrush current, high lumen maintenance, excellent color rendering, high lumen output of more than 100 lumens per watt, and low voltage, cool operation, all over a temperature range of -25°C to more than 60°C.

The technology used in a lamp according to certain embodiments of the present invention can withstand the severe conditions in insulated ceiling and air tight fixtures by employing an advanced amalgam of lead, tin, and goldbismuth in multiple tubes, a protected multi-layer phosphor and protected alumina coating, a special cathode material and impedence, and controlled vapor pressure with special fill gas that enables the lamp burner to achieve excellent lumen maintenance, high lumen output, extended long life, cool operation, high efficacy, selected color and wide temperature operation without blackening of the lamp.

The ballast technology used according to certain embodiments of the present invention provides independent cathode drives for providing ignition and running voltages suitable for the above-mentioned lamp technology employing a single stage, multiple resonant, zero energy storage topology which eliminates the use of electrolytic capacitors and allows wide temperature operation.

These and other features of the configuration will become apparent and be further understood upon reading the detailed description provided below with reference to the following drawings. Brief Description of the Drawings:

Figures 1 through 3 are side views of components of a lamp according to embodiments of the present invention which can be expandable vertically or horizontally for desired power output or dimension.

Figure 3 A is a side view of components of an embodiment of a lamp configuration according to the present invention. Figure 4 is a schematic diagram of a prior art ballast circuit.

Figure 5 is a schematic diagram of a single stage, low cost, low profile, high performance, dimmable electronic ballast.

Figure 6 is a schematic diagram of a conventional triac dimmer. Figure 7 is a schematic diagram of another embodiment of a low profile, low cost ballast with no electrolytics.

Figure 8 is a schematic diagram of a single chip hybrid piezoelectric ballast according to another embodiment of the present invention. Detailed Description of Exemplary Embodiments

While the present invention is susceptible to various modifications and alternative forms, exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the device to the particular forms disclosed, but on the contrary, the intention is to address all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure as defined by the appended claims.

Figure 1 illustrates one embodiment of a top spiral compact fluorescent lamp in a pyramid shape. As indicated by arrows H and W, the overall height or width of the lamp may be readily configured for different power outputs, different housing shapes, and various optical characteristics from different lighting fixtures. Additionally, this construction resistances pull out forces without use of cements to secure the envelope to the base, and improves the heat transfer characteristics to the reflector as further described below. Still referring to Figure 1, the lamp 5 generally includes a low resistance thick cathode material 1, 2 which is inserted into lamp 5 at its ends. Two tubulations 3, 4 are also included at the ends of lamp 5. The multiple tubulations or tubes 3, 4 ensures sufficient availability of mercury at higher or lower temperatures than lamps having a single tube. Tubes 3, 4 respectively include an advanced amalgam 3 a, 4a as described below.

Tubes 3, 4 essentially consitute pumping mechanisms (employing the interior pressure changes that result from thermal variations of lamp 5) for supplying mercury to the interior of lamp 5 when the existing mercury is polluted as a result of phosphor falling out into the gas. When the phosphor falls out, UN rays are allowed to escape, thereby reducing the visible light emitted from lamp 5. Amalgam 3a, 4a are formed as pellets and disposed within tubes 3, 4 to replace conventional mercury pellets. Amalgam pellets 3a, 4a include a ratio of goldbismuth, tin, lead and mercury. The goldbismuth component of amalgam pellets 3 a, 4a do not react to the phosphor, which increases the lumen maintenance of lamp 5 (i.e., results in increased lumens for over a greater temperature range than conventional lamps). The amalgam pellets 3a, 4a (in conjunction with tubes 3, 4) thus function to provide a substantially continuous flow of mercury alloy to facilitate mercury ionization.

In one embodiment of the invention, each amalgam pellet 3 a, 4a includes the following percentages of the various components, using a processing temperature of between approximately 60°C and 125°C (preferrably approximately 85°C):

Lead: 25-50% (preferably approximately 35%) Tin: 25-75% (preferably approximately 25%)

GoldBismuth: 35-45% (preferably approximately 40%)

Mercury: 0.1-1% (preferably approximately 1%)

The gas contained within lamp 5 is a mixture of argon and krypton (conventional fluorescent gas) and xenon, which keeps the gas cool over the operating range of lamp 5, provides controlled vapor pressure, radiates a minimum amount of infrared. The desired low voltage operation of lamp 5 is partially enabled by the cool operation of the gas, which results in lower pressure and correspondingly lower voltage requirements. Additionally, the addition of xenon improves the color temperature of lamp 5. In other words, the addition of xenon in the above-described composition causes the gas to provide light that is closer to white light on a conventional color temperature scale. To avoid local discharge, a buffer gas such as neon may be provide at, for example, 2.5 Torr at room temperature. Suitable combinations of argon, krypton, xenon, and neon are as follows:

Argon Krypton Xenon Neon 37% 50% 12% 1%

28% 57% 13% 2% The xenon may be added with a partial pressure of 38 Torr at room temperature.

Another possible combination includes approximately 50% each of argon and krypton. Also, xenon could be provided in an amount of 12-18% of the argon/krypton combination, but the higher xenon content results in more expensive gas.

Lamp 5 further includes a protective, multi-layer phosphor with protected alumina coating. The alumina coating is a thin alumina layer (preferably approximately 230 microns) which is disposed within lamp 5 below and above the conventional RGB phosphor. The alumina coating prevents the phosphor from falling out into the gas, but is porous enough such that UN wavelengths are permitted to pass. Thus, the porosity of the alumina coating and its composition simultaneously permits UN transfer through the exterior of lamp 5, while inhibiting phosphor fallout into the interior of lamp 5 from the conventional RGB phosphor layer. Additionally, lamp 5 includes a pentaphosphor (such as that manufactured by

Ganga Phospher) which uses more than three standard RGB phosphor types of phosphors blended together with a conventional base material and bonding compound for high lumen maintenance and lumen output. The pentaphosphor is an additional layer of phosphor on the interior side of the alumina layer which increases the efficiency of the lamp by providing an additional phosphor layer, thereby emitting more light. The pentaphosphor layer weight is approximately one milligram per centimeter. The pentaphosphor tends not to fall out into the gas because it is adhered to the alumina layer. The pentaphospor provides a diffused extended area of cross section inside the glass tube, which increases lumen output. This diffused phosphor is adhered to the surface and very little migration of phosphor occurs toward the mercury palette to avoid contamination. As is well known in the art, non-pollution of mercury extends the lumen maintenance of lamp 5.

It should be further understood that the interior surface of lamp 5, unlike the glossy, smooth interior of conventional lamps, is etched by introducing hydrofluoric acid (HF) into the interior of lamp 5. The HF acid removes the smooth interior surface of the glass (which is lead-free to permit the introduction of the above- described gas), thereby increasing the surface area to which the phosphor can adhere. As explained herein, the life of lamp 5 depends primarily on the characteristics of cathodes 1, 2 (i.e., the material that creates the free electrons). Most fluorescent lamps are prepared with the two thoriated tungsten filaments and a glass to metal seal with same expansion coefficient. Generally the expansion coefficient of the cathode material is not same as ceramic. Hence the life of the lamp is decreased with thermal cycles. Deactivation occurs when there is no electron emission from the cathode. The composition of cathode material described below provides more field emission and use a minimal quantity of mercury, if necessary. Cathodes 1, 2 are configured with sufficient cathode material on a larger surface area bounded by a Thorium Oxide material to enhance the life of the cathode, hence enhancing the life of lamp 5 to more than 20,000 hours.

More specifically, lamp 5 includes a thicker filament (approximately 20 times) as compared to conventional filaments, which permits lower voltage operation as result of decreased resistance. Additionally, the increased thickness of the filament provides additional surface area for adherence by Thorium Oxide (the loosely bonded material forming a powder coating on the tungsten filament that provides free electrons when the filament is heated), more current capacity, and improved manufacturability. As compared to a 500 to 10,000 ohm filament, filaments of the present invention have resistances between 1 and 5 ohms. The material used in one embodiment of the invention includes proportions of Barium Oxide (1 mol. g), Strontium Oxide (0.8 mol. g), and Calcium Oxide (0.8 mol. g).

Referring now to Figures 1 through 3, unlike various CFL reflector products, the configurations shown are designed to avoid, among other things, the following characteristics: 1) Inadequate light output and beam spread;

2) Excessive lamp length that causes fit and glare problem in recessed do nlights; and

3) Reduced lumen output and lamp life resulting from high lamp and ambient temperature when operated within insulated ceiling and airtight recessed downlights.

Figure 2 illustrates a configuration 8 including a lamp 9, a reflector 10 and a built-in low profile ballast 12. Electronic ballast 12 is a compact unit attached to heat sink aluminum reflector 10. A reflector dome 14 (shown in dotted lines) concentrates light beams toward the front of configuration 8. Reflector dome 14 is substantially conical in shape and extends outwardly from base 16 into the interior of the pyramid shape of lamp 9 to reflect light in a parallel fashion or parallel beam as indicated in the figure. The overall height of configuration 8 may be, for example, 6.26 inches for R

40 lamps and 5.24 inches for R 30 lamps. Lamp 9 is attached to base 16 and electronic ballast 12 with the aid of heat conducting resin as is further described below. Reflector structure 10 helps in directing the light in a forward direction, minimizing internal reflection mid glare. Figure 3 depicts an alternative reflector 10' which is substantially conical in shape.

Because the paraboloid aluminum reflector configuration is essentially fixed in the market, a lamp is needed to provide either wide flood, narrow flood or beam lighting. Current lamps are not configured to provide these various options. The paraboloid aluminum reflector requires either a point light source to provide these various beams, or a lamp with a shape that follows the curvature of the paraboloid. The pyramid shape of lamp 9 when directed outwardly from base 16 provides a wide flood. If reflector 10 opening is extended, for example, by rotating reflector 10 onto threads 18, the width of the flood can be narrowed. More specifically, the Fresnel lens 20 of Figure 2 is removably attached to the opening of reflector 10. Conventional such lenses are typically flat. Lens 20 is formed in the shape of a dome. By moving reflector 10 and lens 20 toward and away from base 16, the beam can be focused or diffused. If the pyramid shape is inverted, and all of the connecting components are reversed, then the light reflected off the interior of reflector 10 is directed in a parallel fashion to produce a beam. As should be apparent from the foregoing, the pyramid structure of lamp 9 permits maximum reflection of the light toward the front of configuration 8. A minimum air gap is maintained between metal reflector 10 and lamp 9 to increase and enhance the heat transfer and light transfer from the light source (lamp 9) to metal reflector 10. This construction maximumizes surface area availability for increase light output. The inverted pyramid configuration discussed above is in substantially continuous contact with metal reflector 10, thereby further enhancing heat sinking. Such inverted pyramid lamps (constructed in coaxial manner), provide even more light output from the same package. This construction of lamp 9 occupies substantially the total area of reflector 10, and appears as a substantially solid light source filled inside reflector 10. The construction of reflector 10 and the ballast (further described herein) satisfies the requirements of shape and size of the existing incandescent and halogen reflector lamps like PAR38, R30, R40, R22 and MR16 etc. In an alternate embodiment, additional layers of lamps may be embedded within an exterior layer of lamp 9. In one configuration, all of the plurality of lamps may be connected in parallel such that only one lamp works at time. When the first lamp burns out, the next lamp in the parallel chain is activated and works automatically, thereby extending the overall life of the lamp by the multiple lives of the individual lamps making up the composite. Additionally, such a configuration provides a visual indication of lamp failures (i.e., monitoring). Alternatively, the lamps may be connected to a conventional combiner which permits simultaneous operation of the plurality of lamps, thereby increasing the possible wattage from a single package. Additionally, lamps with various colors may be used in a combination to provide any composite color in the spectrum. Finally, by having a plurality of simultaneously operating lamps, the dimming range of the composite lamp is increased. For example, a single lamp may have a lower limit dimming setting of 5% to 10% of maximum. With a multiple configuration, the composite dimming range may be increased by deactivating one or more of the lamps in the composite. The present invention provides a reflector lamp configuration that operates satisfactorily in an extended temperature range from -20°C to 60°C ambient. This wide temperature operation is facilitated, in part, with heat management technology using remote heat sinking and heat circulation technology. Components of the heat management technology are shown in Figure 3 A. As shown, lamp 9 is connected to base 16 which includes a metallic housing 21, an internally positioned metal disk or ring 22, and a conducting fluid or paste 24 is disposed at the yoke of lamp 9 (a portion of the lamp that is excited and creates the highest temperature) to remove heat from this high temperature area of the lamp. Paste 24 is also in contact with metallic ring 22 which transfers heat to metallic reflector 10 of the lamp. The composition of the conducting fluid is as follows: beryllium oxide, which is an excellent heat conductor and electrical insulator. As should be apparent from the figure, in the standard inverted orientation of the lamp configuration, heat from lamp 9 rises toward the heat management components, further increasing their efficiency.

Figure 4 schematically illustrates a prior art electronic ballast. A single stage electronic ballast uses conventional offline rectifiers and capacitive smoothing filters 114 located near the bridge rectifier (diodes 105, 106, 107, 108). Smoothing capacitor 114 causes harmonic distortion of the current wave forms during periods in which the voltage across capacitor 114 is lower than the rectified output voltage. During this time, capacitor 114 tries to charge to the peak value. This charging time and the angle of conduction are very small for a large electrolytic capacitor 114. These spikes of current increases the total harmonic distortion and cause poor power factor in the supply line. This situation is not acceptable by the electric utility companies because it causes interference with other electronic and electrical equipment. As mentioned above, passive power factor correction techniques use large number of rectifiers and electrolytic capacitors increasing not only the cost but the size of the ballast. Passive power factor correctors also cause intermodulation of the power line frequency with the high frequency output of the ballast, causing flicker. Active power factor corrected electronic ballasts are complex and expensive to produce.

A self oscillating bridge inverter uses bipolar transistors 124, 125 and a current transformer 119 to supply high frequency power to the lamp through the resonant circuit 111 and 115. A large filter capacitor 114 after the bridge rectifier decreases the power factor and increases the harmonic distortion. Capacitor 114 also breaks down at high temperature. Hence, prior art circuits are unreliable and unsuitable.

Figure 5 illustrates one embodiment of a single stage, high power factor, low distortion electronic ballast with a dimming facility according to the present invention. A half bridge inverter comprising of bipolar transistors 224, 225 is a self-oscillating type. The circuit includes a series resonant oscillator circuit comprising a primary resonant capacitor 214 across the lamp 216 and a primary resonant inductor 218 in series with the lamp 216 to ignite and limit the arc current of the lamp 216. Also included is a current feedback transformer Tl having windings 219, 230 and 227 is responsible for self-oscillation at a predetermined frequency determined by the values of primary inductor 218 and primary capacitor 214. Lamp 216 is connected across the primary resonant circuit. As soon as lamp 216 is ignited by the series resonant circuit 218, 214, resonant capacitor 214 is shorted by conducting lamp 216. An auxiliary resonant circuit is formed by primary inductance 218 and auxiliary capacitor 210, which is connected across a voltage isolation diode 211. The energy of this circuit is stored and released in a periodical manner and is always higher than the rectified voltage. Thus, variable DC voltage is available across the DC bus due to the natural integration of the variable DC voltage and rectified power line voltage. Therefore, during the positive half cycle of the voltage supplied by the power line, the DC bus voltage will be sufficient to sustain the oscillation and produce a voltage high enough to sustain the arc current of lamp 216.

Auxiliary voltage generated by second series resonant circuit 218, 210 is always added to the power line voltage and this instantaneous magnitude supplies the variable DC voltage to maintain the ignition and arc current even at different conduction angles of the dimmer 236. The auxiliary resonant circuit 218, 210 is tuned to the same frequency or near the same resonant frequency of the primary oscillator (as the frequency of oscillation of the main resonance circuit) to generate a high power factor, low distortion, and flicker free dimming. Voltage separating diode 211 allows the charging of the energy storage capacitor 235, which is a polypropylene non-electrolytic capacitor, when the DC voltage rises above a certain magnitude. Hence, a constant DC voltage is developed across this storage capacitor 235.

Since the energy storage capacitor 235 is not only charged by the power line but also by the auxiliary resonant circuit, the current drawn from the sinusoidal power line becomes proportionate to the voltage wave form of that power line. The result is a reduced inrush current from the power line.

During the operation of the dimmer circuit, the conduction angle of the power source is changed by a phase controller dimmer 36. The waveforms no longer remain sinusoidal from the power mains. Despite the change of conduction angle, the voltage separating diode 211 provides relatively constant DC voltage across the energy storage capacitor 235. The cathode voltages proportionally increase during the phase control regulation of the power line voltage. The frequency of oscillation of the oscillatory resonant circuit 218, 210 automatically goes down. Additionally, the duty cycle of switching transistors 224, 225 is automatically decreased during the portion of each half cycle. Energy is always stored and released by the auxiliary resonant circuit 218, 210 not only for power factor correction, but also for dimming needs. Power is drawn from the power source at a power factor of approximately 99%. Thus, Figure 5 illustrates a simple, low cost, low component count electronic ballast suitable for all power line voltages and frequencies.

Figure 6 illustrates a conventional triac dimmer with phase control dimming. The resistor 302 changes the conduction angle of the triac 304 and provides the mains power to the reflector lamp 306 at different conduction angles by changing the phase angle through time constant 302, 303. Inductor 301 and capacitor 305 provide in line filtration.

Figure 7 illustrates a low profile, low cost ballast with no electrolytic capacitors. It provides very high power factor of approximately 0.99, low distortion of less than 10%, and dimming ability from 10% to 100%. This embodiment has a low component count, and hence, a low cost. The circuit includes a six pin hybrid IC (depicted with dotted lines) with three peripheral components. Since this is a zero energy storage electronic ballast, it offers high efficiency compared to other electronic ballasts. Diodes 401, 402, 403, 404 in the bridge configuration supply the rectified pulsating DC voltage to the complementary inverter transistors 411, 412. Self oscillating inverter uses a feedback current transformer 409, 413 to supply a high frequency to a series resonance circuit 414, 415. Reflector lamp 416 is connected across resonant capacitor 415 to be ignited by the high voltage at ignition and subsequently low voltage for running. It should be understood that the ballast and gas discharge lamp configurations taught herein can operate in a low voltage range of 20 through 40 volts, but in any event under 65 volts. Capacitors 417, 418 block the DC path and provides a virtual ground to the inverter circuit.

Figure 8 illustrates a single chip hybrid Piezoelectric transformer based electronic ballast. Its low profile enables the ballast to be mounted inside the lamp base. High displacement Piezoelectric transformer 515 along with a single stage DC to AC inverter efficiently converts the mains voltage into an AC voltage of high frequency. Transformer 515 generates high voltage sufficient to start a compact fluorescent lamp 517. Transformer 515 begins resonating by the initial pulse. Transistor 514 is a power MOSFET and, along with inductor 513, provides the resonant frequency of the Piezoelectric transformer 515. Diodes 503, 504, 505, 506 form a bridge rectifier which supplies pulsating DC voltage to the oscillator. Capacitor 507 is an optional polypropylene capacitor for filtering high frequency pulses. Zener diodes 511, 512 provide the clamp voltage of 10 volts for safe operation of transistor 514. Resistors 509, 510 provide the bias for the self oscillating inverter ballast.

As should be apparent from the foregoing, each component in the lamp burner may be monitored and controlled for over and under temperature. For example, if one or both of the lamp filaments break, then a capacitor (for example, 0.001 microfarads) connected across the lamp shorts across the lamp to indicate a failure. Pairs of opposing protection diodes may be connected across each of the pairs of filament leads. These diodes maintain some current flow through the lamp even if one filament is broken to provide an indication (by dimming) that the lamp has failed (or is failing). Consequently, deactivation in this manner does not spoil the lamp.

As should also be apparent from the foregoing, the lamp configurations of the present invention reduce EMI and RFI by providing electrostatic and electromagnetic shielding for burner, ballast, and fixture. More specifically, the metal components (reflector, base, ballast exterior, etc.) reduce such emissions. As should also be apparent from the foregoing, the present invention addresses the problem of high temperature electrolytic capacitors. A major problem with conventional CFL-R lamps is their very short ballast / lamp life, which is due primarily to the fact that they cannot withstand the very high temperatures of the recessed downlight operating environment which can reach 125C. One component of these lamps that is a primary cause of early lamp failure is the electrolytic capacitor, which typically is rated for only 105C for standard low cost component. The present federal program such as PNNL technology procurement program has required that all these reflector lamp products for IC/AT fixtures use capacitors rated at a minimum of 125C. To avoid this situation, the present invention uses no electrolytic capacitors in the various designs.

It should be understood that the present invention provides a primary feature low cost dimming and constitutes the only diminable CFL-R lamp available without extra cost. In addition, the present invention accomodates two or more models: both an R40 and an R30.

In various embodiments of the invention, the electronic ballast contains a first series resonant circuit to ignite the lamp providing high voltage resonance and limits the arc current through the inductance. The second resonant network is formed by the same inductance and a separate isolation capacitor across the isolation diode, and provides the high voltage due to resonance across the lamp even when the triac dimmer provides a low conduction angle at different settings. An instantaneous magnitude of a current drawn from the alternating voltage source is substantially proportional to an instantaneous magnitude of the voltage of the alternating voltage source. The second resonant frequency is near or equal to the frequency of oscillation of the primary resonant oscillator, each of the alternately conducting transistors having a duty cycle associated with the conduction angle. The duty cycle is automatically modulated in proportion to the instantaneous amplitude of a voltage equal to the difference of instantaneous amplitude of the constant DC voltage and instantaneous amplitude of the voltage supplied by the rectified low frequency alternating voltage source. The frequency of oscillation of the primary resonant oscillator is considerably faster than half -cycle frequency of the alternating voltage source. An instantaneous magnitude of a current drawn from the alternating voltage source is substantially proportional to an instantaneous magnitude of the voltage of the alternating voltage source.

As should also be apparent from the foregoing, the present lamp comfiguration has universal mains input: either 220 Volts or 110 Volts at 50 Hz or 60 Hz or 400 Hz (for railways, trucks buses, etc.). Moreoever, the same lamp using the present ballast topology can give any wattage from 9 watts to 85 watts in R-40 and PAR38 enclosures. This topology of the ballast will allow the lamps to be of any wattage from 9W to 250W to replace HID lamps and high power cartridge lamps and troffers, shoplights, studio lights, T8, T5, T12 lamps, tanning bed lamps, etc. Moreoever, the topology of the ballast allow the lamp configuration to be used as a toolless retrofit for existing sodium vapor, metal halide, mercury vapor HID lamps without removing their existing magnetic ballast because of its ability to cancel the inductive reactance effect of the existing magnetic choke in the existing lighting circuits. Finally, it should also be apparent from the foregoing that the rectifier circuit can be either in the form of a full-wave rectifier bridge or a doubler circuit. Test results of the present invention demonstrate the following: 1) Lumen efficiency: more than 100 lumens per watt 2) Temperature range of operation - 30°C to 65°C

3) The power output 9 w to 35w

4) Power factor better than 0.95

5) Total harmonic distortion less than 17%

6) Wide diffirning range: 13 % to 100% 7) Flicker: less than 2%

8) Inrush current: less than 1.8 amp

9) Color rendering index: more than 85%

10) Longer life: more than 20,000 hours

The foregoing description of the invention is illustrative only, and is not intended to limit the scope of the invention to the precise terms set forth. Although the invention has been described in detail with reference to certain illustrative embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.

Claims

CLAIMS:

1. A lamp, including: an enclosure; and a gas contained within the enclosure; the gas having an operating voltage for emitting light that is below 65 volts.