Patent Grant
7030573
1. Field of Invention
The present invention generally relates to high intensity discharge (HID) lamps and more specifically to a high intensity strobe lamp assembly and method that produces strobe illumination without electromagnetic interference (EMI).
2. Brief Description of the Related Art
By way of background to the ensuing discussion of the related art to the present invention, and in connection with the description of the invention hereinafter, set out below is a glossary of relevant terminology.
As used herein, a “high intensity discharge (HID) lamp” means a lamp using a ballast to generate an electrical charge and to regulate voltage and current, which produces illumination when an arc of electrical energy passes across an arc gap, through gas contained in the lamp. Examples of HID lamps include, without limitation, metal halide lamps, compact metal halide lamps, pulse-start metal halide lamps, high pressure sodium lamps, white high pressure sodium lamps, mercury vapor lamps, and low-pressure sodium lamps.
The term “incandescent lamp,” as used herein, means a lamp that produces illumination by heating of an internal filament to generate radiant light.
The term “fluorescent lamp,” as used herein, means a lamp that uses phosphorus material to produce light when a gas is activated to energize the phosphorus material.
The term “harmful EMI,” as used herein, means electromagnetic radiation generated at a frequency≧1 MHz that produces undesirable interference with the operation of electrical/electronic equipment.
The term “continuous current,” as used herein in reference to an HID lamp, means an electrical current, e.g., a direct current (DC) or an alternating current (AC), which is uninterrupted across an arc discharge of a HID lamp throughout the powered operation of such lamp.
The term “strobe,” as used herein in reference to a lamp, means a lamp that produces intermittent discrete bursts of visible light (“strobing emissions”) in a cyclic and repetitive manner, wherein successive bursts are separated by periods of lamp operation with no visible light emission or with light emission that is of substantially lower intensity than the bursts of visible light (“non-strobing operation”).
The term “powered operation,” as used herein in reference to a strobe lamp, means electronic operation of the strobe lamp producing strobing emissions and non-strobing operation.
The strobing process has been conventionally carried out by cyclically and repetitively turning the power to a lamp on (with current flow to the lamp) and off (with zero currernt flow to the lamp), in an alternating and repetitive cycle.
Many types of lamps have the capability to be operated as strobe lamps. Such lamps include halogen, LED, incandescent, fluorescent and high intensity discharge (HID) lamps. HID lamps are particularly preferred for strobing applications, due to the higher energy efficiency of HID lamps (lumens emitted per watt of input power) than other lamps.
HID lamps, however, have a significant disadvantage in strobe operation. Once the arc discharge of the HID lamp is disrupted during turn-off of the current to the lamp, the lamp cannot restart without a significant time delay, which may in some cases be as long as one minute, unless a high voltage (e.g., on the order of 30 kV–50 kV) is applied to the lamp. When such high voltage is applied to a non-powered HID lamp, however, electromagnetic interference (EMI) signals are generated in the MHz and GHz range. Because most electronic devices operate in the MHz and GHz range, the EMI that is generated (in turn-on of the HID lamp by impressing high voltage thereon) can cause damage to or malfunction of electronic devices that are in proximity to the HID lamp EMI source.
The prior art metal halide strobe light systems that produce such deleterious EMI effects include the metal halide lamp strobe system of U.S. Pat. No. 6,501,231, wherein high voltage power, e.g., at 30 kV, is cyclically applied to the lamp to produce strobing action.
Such lamps as a result of their high-EMI output cannot be utilized in environments containing sensitive electrical/electronic equipment whose operation would be compromised by EMI exposure.
Environments of such type include aircraft environments in which HID strobe lamps as a result of their luminous intensity are highly desirable for exterior lighting of the aircraft, but in which sensitive avionics equipment are susceptible to malfunction and failure as a result of the deleterious EMI radiated by these lamps during their switch-on.
Efforts have been made in the prior art to reduce EMI from HID lamps by shielding approaches. For example, U.S. Pat. No. 5,530,634 describes a shielding arrangement in which an EMI-emissive area is covered with a metal foil. Shielding, however, increases the cost and complexity of the lamp system, is labor-intensive to install, and is susceptible to deterioration and mechanical failure, with consequent adverse effect on electrical/electronic equipment in the environment of the EMI-emitting HID lamp.
There is therefore a continuing need in the art for HID lamps that are free of deleterious EMI effects.
The present invention relates to a high intensity strobe lamp assembly and method that produces strobe illumination without deleterious electromagnetic interference (EMI).
In one aspect, the invention relates to a high intensity discharge strobe lamp assembly, comprising a high intensity discharge lamp having an arc gap that is energizable for strobing emission, and circuitry that is constructed and arranged to (i) deliver power to the high intensity discharge lamp from a power supply for powered operation including strobing emissions and non-strobing operation, (ii) supply current continuously to the arc gap of the high intensity discharge lamp during said powered operation so that a flux of electrons across the arc gap is maintained during said strobing emissions as well as said non-strobing operation, and (iii) generate no deleterious EMI during said powered operation.
In another aspect, the invention relates to a high intensity discharge strobe lamp assembly as described in the preceding paragraph, operatively coupled with a power supply for said powered operation, and disposed at a location in proximity to electrical and/or electronic equipment that would produce electromagnetic interference with said equipment if deleterious EMI were generated at said location.
A further aspect of the invention relates to a vehicle including electrical and/or electronic equipment susceptible to electromagnetic interference from deleterious EMI, and a high intensity discharge strobe lamp assembly as described hereinabove.
Yet another aspect of the invention relates to a structural installation including electrical and/or electronic equipment susceptible to electromagnetic interference from deleterious EMI, and a high intensity discharge strobe lamp assembly as described hereinabove.
A still further aspect of the invention relates to a method of producing strobe illumination from a high intensity discharge lamp having an arc gap that is energizable for strobing emission, said method comprising (i) delivering power to the lamp for powered operation including strobing emissions and non-strobing operation, (ii) supplying current continuously to the arc gap of the high intensity discharge lamp during such powered operation so that a flux of electrons across the arc gap is maintained during the strobing emissions as well as the non-strobing operation, and (iii) generating no deleterious EMI during such powered operation.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.
The present invention relates to a high intensity discharge strobe lamp assembly that produces strobe illumination without the incidence of EMI emissions that have limited the utility of prior art HID strobe lamps in EMI-sensitive applications.
In one preferred embodiment, the HID strobe lamp assembly of the present invention is utilized for exterior aircraft lighting applications, to provide high-visibility strobe illumination during operation of the aircraft, without adverse impact of EMI effects on the on-board avionics instrumentation of such aircraft, e.g., navigational and communications systems, fuel and engine monitoring equipment, electromechanical systems for landing gear and aircraft control surface elements, telemetry systems, etc.
The present invention is based on the discovery that a current may be applied continuously to the arc gap of a high intensity discharge strobe lamp, throughout the powered operation of the lamp including strobing emissions and non-strobing operation, so that a flux of electrons is maintained across the arc gap during the intervals of powered operation when strobing emissions are not being actively generated by the lamp assembly.
By maintaining an electron flux across the arc gap during non-strobing periods of powered operation, a substantially reduced voltage, typically below 1500 volts, is required to energize the lamp for production of strobing emissions. By way of example, an HID lamp assembly of the present invention may be operated with a turn-on voltage for strobing emission on the order of about 1000 volts, rather than the 30 kV–50 kV levels that are required for turn-on of strobing emission in conventional HID strobe lamp assemblies. As a result of such reduction of the level of the energizing voltage for initiating strobe emission, a lamp assembly of the invention operating at a strobing emission turn-on voltage of 1000 volts exhibits no EMI in the megaHertz-gigaHertz spectrum.
In a specific embodiment of the invention, the control circuitry for the HID strobe lamp assembly includes a dimmer circuit that is constructed and arranged to dim the HID lamp when an input signal having a low duty cycle is applied to the lamp, e.g., an input signal with a 10–20% duty cycle, and to produce strobing emission when an input signal having a high duty cycle is applied to the lamp, e.g., an input signal having a 50% duty cycle, wherein the low duty cycle and high duty cycle operations are alternatingly and repetitively carried out for powered operation of the HID lamp to produce strobe illumination, without generating deleterious EMI.
In another specific embodiment of the invention, the HID strobe lamp assembly includes circuitry that is constructed and arranged to generate strobe illumination and provide continuous current to the arc gap of an HID lamp. Such circuitry includes a first circuit that when switched on ignites and provides continuous current to the lamp, maintaining the lamp in a dimmed powered operation (non-strobe operation) state. The circuitry is arranged so that the first circuit then is switched off and a second circuit of the circuitry is switched on. The second circuit flashes the lamp by applying a higher voltage sufficient to generate strobe emissions from the lamp, while maintaining flow of continuous current to the lamp. Following the flashing of the lamp by the second circuit, the second circuit is switched off and the first circuit again is switched on, and the cycle then is continued, in an alternating and repeating manner, of powered operation involving strobe emission followed by non-strobe operation, followed by strobe emission, etc., to provide sustained strobe illumination without the incidence of deleterious EMI.
Specific features and aspects of the invention will be more fully appreciated by the ensuing discussion of illustrative aspects, features and embodiments of the invention.
Referring now to the drawings,
The HID strobe lamp assembly of
When the alternating current signal is varied, the two mosfets 12 and 14 alternatingly and repetitively turn on and off in reciprocal relationship to one another, so that while one of such mosfets is on, the other is off. In this circuit, when the input voltage is at a high stage, mosfet 12 is on and mosfet 14 is off. In such configuration, the current will flow through the input windings 21a of transformer 20. When the input voltage is at a low stage, mosfet 14 is on and mosfet 12 is off, causing the current to reverse direction. The input source, mosfets and associated transformer thus form a push-pull circuit 11 generating an alternating current.
Referring again to the
An ignitor circuit 40, having transformer 30 associated therewith, connects across the lamp 35 for ignition thereof. A switch (not shown in
When the input source 15 has a high state, e.g., a 50% duty cycle, the power transformed from the input windings 21a to the output windings 21b of transformer 20 will transfer power to the lamp 35 for strobe emission, and when the input source 15 has a low state, e.g., a 10–20% duty cycle, the lamp is dimmed for non-strobing powered operation.
Thus, to effect powered operation of the lamp, involving repeating cycles of sequential strobing emission and non-strobing operation, the duty cycle of the input signal is intermittently varied from the low state to the high state, e.g., from a low state duty cycle of about 10–20% to a high state duty cycle of about 50–60%.
During powered operation, the lamp receives continuous current, i.e., electron flow across the arc gap of the lamp is not disrupted, but continues through both of the repeating steps of strobing emission and non-strobing operation.
The circuitry shown in
The circuit of
The circuitry in
The simmer circuit 75 includes a switch 82 that is in series with output windings 74 and the lamp 35, and is selectively actuatable to turn the simmer circuit 75 on and off, depending on the closed or open character of the switch, respectively.
The switch 82 generally may be of any suitable type, including, without limitation, electrical switches, transistors, diodes, digital logic, and relays.
Dimmer circuit 71 connects output windings 70 with the lamp 35. The dimmer circuit 71 when actuated applies a suitable voltage, e.g., a voltage on the order of 100 volts, on the lamp 35.
The dimmer circuit 71 includes switches 72 and 90 and the ignitor circuit 80.
Switch 72 is in series with the output windings 70 and the ignitor circuit 80, and functions to electrically connect or disconnect the windings 70 to the ignitor circuit 80 and the lamp 35.
Ignitor circuit 80, similar to ignitor circuit 40 of
Switch 90 is in series with the ignitor, and functions to electrically connect the ignitor circuit 80 to, or disconnect it from, simmer circuit 75, dimmer circuit 71 and the lamp 35.
Neither switch 72 nor 90 is concurrently closed when switch 82 is closed because both circuits 71 and 75 deliver power to the lamp 35. Thus, when switches 72 and 90 are closed, switch 82 is open, and vice versa.
When switches 72 and 90 are closed, windings 70 and the ignitor circuit 80 are electrically connected to lamp 35. This will apply a continuous current, e.g., of about 0.5 amps, and voltage, e.g., of about 100 volts, to the lamp 35. When switches 72 and 90 are closed, switch 82 is open, to electrically disconnect the windings 74 from the lamp 35.
When switch 82 is closed, switches 72 and 90 are open. Thus, windings 70 and the ignitor circuit 80 are electrically disconnected from the lamp 35, while a voltage, e.g., of about 1 kV, and current, e.g., in a range from about 10–30 mA, from output windings 74 are applied to lamp 35. This switching of electrical power does not disrupt the arc discharge of the lamp 35. Additionally, because there has been continuous current flow to the lamp and the arc discharge of the lamp has not been disrupted, such application of power to the lamp, e.g., a voltage of 1 kV and a current of 10–30 milliamps, will cause the lamp to flash for strobing emission without delay.
Logic unit 92, shown in
Similar to the gate voltages 16 and 18 of the lamp assembly schematically depicted in
In the
To ensure stability of the ignitor circuit, a feedback circuit 200, as shown in
The logic units in the lamp assembly embodiments illustratively described hereinabove may be of any suitable type, and may be operatively arranged in any suitable manner to effect the powered operation of the HID strobe lamp in the lamp assembly involving a repetitive sequence of strobing emission and non-strobing operation steps, whereby flashing of the strobe lamp occurs without deleterious EMI emission.
As a result, the HID strobe lamp assembly of the invention can be used in applications and end-use environments containing sensitive electrical/electronics equipment which would otherwise be susceptible to interference, malfunction and failure from deleterious EMI if conventional HID strobe lamps were employed.
The invention therefore contemplates the deployment of HID strobe lamp assemblies on aircraft and on and/or within other vehicles and structural installations containing or including EMI-sensitive electrical/electronic componentry and equipment, without impediment to the operation of such componentry and equipment.
It will be apparent from the foregoing that the HID strobe lamp assembly of the invention provides a simple and readily fabricated device for strobe illumination that avoids the need of the prior art for long delay periods between successive strobing emissions of an HID lamp, or the high voltage turn-on conditions that are otherwise necessary to initiate strobing emissions and that concurrently produce deleterious EMI. By providing a strobe lamp assembly that is characterized by short periods of non-strobing operation between successive bursts of strobing emissions, with low-voltage operation, and an absence of any deleterious EMI, the present invention achieves a substantial advance in the art of strobe illumination.
While the invention has been described herein with reference to specific features and illustrative embodiments, it will be recognized that the utility of the invention is not thus limited, but rather extends to and encompasses other features, modifications and alternative embodiments as will readily suggest themselves to those of ordinary skill in the art based on the disclosure and illustrative teachings herein. The claims that follow are therefore to be construed and interpreted as encompassing all such features, modifications and alternative embodiments within their spirit and scope.
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| Number | Date | Country | |
|---|---|---|---|
| 20050231132 A1 | Oct 2005 | US |
