Patent Publication Number: US-7221105-B2

Title: Electromagnetic radiation emitting bulb and method using same in a portable device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This Application claims priority from a U.S. Provisional Application having Ser. No. 60/329,480 filed on Oct. 15, 2001, now abandoned and an International Application having Application No. PCT/US02/33234 filed on Oct. 15, 2002. 

   FIELD OF THE INVENTION 
   The present invention relates generally to a single bulb unit which emits electromagnetic energy. In certain embodiments, Applicant&#39;s bulb produces visible light. In other embodiments, Applicant&#39;s bulb emits electromagnetic radiation in one or more non-visible portions of the spectrum, such as infrared radiation and/or ultraviolet radiation. 
   BACKGROUND OF THE INVENTION 
   Low voltage light bulbs typically comprise one or more incandescent elements in a glass envelope. At best, such incandescent bulbs have short lifetimes. In addition, such incandescent light bulbs are fragile, and if dropped have even shorter lifetimes. In addition, these incandescent light bulbs are inefficient at converting electric energy into visible light, i.e. photons. The brightness of an incandescent light bulb is generally ay function of the voltage applied. In flashlight applications, to get a brighter light one needs to use more batteries. However, a different low voltage incandescent light bulb is required for each discrete number of battery cells. 
   Alkaline batteries typically provide a voltage of about 1.5 volts per cell. An incandescent bulb that is designed to be powered by one cell will burn out if powered by two or more cells in series. On the other hand, a bulb designed to operate using 4.5 volts, provided for example from three alkaline cells in series, will not produce much light if powered by a single cell. When powered by two cells such a device will produce a light having a yellowish cast due to the lower temperature filament. When powered by a single cell the light emitted from such a device will be very dim. Therefore, in order to provide sufficient light output, a different light bulb is needed for each combination of battery cells. 
   The required multiplicity of light bulbs is further compounded with use of rechargeable batteries. Nickel Cadmium cells (NICAD, for example, typically have a voltage of about 1.2 volts per cell. A bulb designed for use with three alkaline cells, however, will not provide sufficient light if powered by three NICAD cells. Thus, a different light bulb is required for each combination of NICAD cells. Needless to say, a single bulb using incandescent technology that can be usefully operated over a large input voltage range would be highly desirable. Applicant&#39;s invention comprises such a light bulb. 
   It is known in the art that light emitting diodes, i.e. LEDs, can overcome some of the limitations inherent with incandescent light bulbs. However, the applied voltage must be high enough to overcome the characteristic voltage drop of the LED. Typically, a preferred method to operate an LED is to use a voltage higher than the turn on voltage of the LED, and to limit the current through the LED with a current limiting resistor. This requires using a voltage higher than that actually required by the LED. Such a method, however, prevents LEDs from being used as lighting elements with very low voltage systems. In addition to voltage-related problems, light emitting diodes can be destroyed by driving too much current through the device. Thus, use of an LED requires adjustment of both the voltage and current supplied to that LED. 
   Prior art LED light bulbs are designed for use with only one specific voltage. This specified voltage must necessarily exceed the voltage drop of the LED. In addition, these prior art devices include one or more LEDs in combination with one or more dropping resistor(s) to limit the current to the LED(s). Typically such prior art LED light bulbs require three battery cells in series to provide more than four volts to light a white LED. 
   The difficulties inherent with use of such prior art LED light bulbs are also compounded if rechargeable batteries are used. As noted above; Nickel Cadmium cells (NICAD) typically have a voltage of about 1.2 volts per cell. Using three such NICAD cells only provides about 3.6 volts, which is marginal for some white LEDs. Use of four cells, however, can result in premature LED device failure. Therefore, use of NICAD cells to power an LED light bulb requires four NICAD cells in combination with one or more current limiting resistors. Such a combination is necessarily designed for a specific voltage based upon the voltage drop of the LED and the current limiting resistor(s). 
   Thus, use of such prior art LED light bulbs is subject to constraints almost identical to use of incandescent bulbs. What is needed is an LED light bulb that can be used over a wide range of input voltages. Such a device can be used interchangeably with, for example, a flashlight using one, two, or three, batteries, where those batteries may be of the non-rechargeable or rechargeable type. Applicant&#39;s invention comprises such an LED light bulb. 
   SUMMARY OF THE INVENTION 
   Applicant&#39;s invention includes a bulb, comprising a housing; one or more power input terminals disposed on that housing; a voltage converter disposed within the housing, where the voltage converter is electrically connected to the one or more power input terminals; and one or more electromagnetic radiation emitting elements/devices disposed within the housing, where the one or more electromagnetic radiation emitting elements/devices are electrically connected to the voltage converter. 
   Applicants&#39; invention further includes a method to emit electromagnetic radiation from a hand-carried device composing Applicant&#39;s bulb and one or more battery cells. Applicant&#39;s method supplies first DC power having a first voltage from the one or more battery cells to the bulb, converts within the bulb the first DC power to second DC power having a second voltage, supplies within the bulb the second DC power to one or more electromagnetic radiation emitting elements/devices, and emits electromagnetic radiation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood from a reading of the following detailed description taken in conjunction with the drawings in which like reference designators are used to designate like elements, and in which: 
       FIG. 1  is a block diagram of a first embodiment Applicant&#39;s bulb; 
       FIG. 2  is a block diagram of a second embodiment of Applicant&#39;s bulb; 
       FIG. 3  is a graph showing the voltage supplied over time by one or more batteries to the lighting element of a prior art light bulb; 
       FIG. 4  is a graph showing the intensity of light emitted over time by prior art light bulbs using the voltage of  FIG. 3 ; 
       FIG. 5  is a graph showing the voltage supplied over time by one or more batteries to the lighting elements of Applicant&#39;s bulb; 
       FIG. 6  is a graph showing the intensity of electromagnetic radiation emitted over time by Applicant&#39;s bulb; 
       FIG. 7  is a first embodiment of the form factor of Applicant&#39;s bulb; 
       FIG. 8  is a second embodiment of the form factor of Applicant&#39;s bulb; 
       FIG. 9  is a third embodiment of the form factor of Applicant&#39;s bulb; 
       FIG. 10  is a fourth embodiment of the form factor of Applicant&#39;s bulb; 
       FIG. 11  is a graph showing the frequency of a first and second AC power produced by Applicant&#39;s bulb; 
       FIG. 12  is a flow chart summarizing the steps of Applicant&#39;s method to emit electromagnetic radiation from a portable device using Applicant&#39;s bulb; 
       FIG. 13  is a block diagram showing an embodiment of Applicant&#39;s bulb that includes a microprocessor; and 
       FIG. 14  is a block diagram showing the components of Applicant&#39;s bulb disposed on a flexible substrate. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   This invention is described in preferred embodiments in the following description with reference to the Figures, in which like numbers represent the same or similar elements. The invention will be described as embodied in an apparatus and method to provide a portable light-emitting assembly, i.e. a flash light. The following description of Applicant&#39;s apparatus and method is not meant, however, to limit Applicant&#39;s invention to portable devices or to devices emitting visible light, as the invention herein can be applied generally to electromagnetic radiation emitting devices. 
   Referring now to  FIG. 1 , apparatus  100  includes housing  190 , voltage converter assembly  110 , and one or more electromagnetic radiation emitting devices  120 . In certain embodiments, electromagnetic radiation emitting devices  120  are capable of emitting visible light. By “visible-light,” Applicant means radiation having a frequency of about 10 14  hertz to about 10 15  hertz. In certain embodiments, one or more electromagnetic radiation emitting devices  120  comprise one or more incandescent elements. In certain embodiments, one or more electromagnetic radiation emitting devices  120  comprise one or more light emitting diodes (“LED”). In certain embodiments, one or more electromagnetic energy emitting devices  120  comprise a combination of one or more incandescent elements and one or more LEDs. 
   In certain embodiments, electromagnetic energy emitting devices  120  comprise one or more pulsed laser diodes. Available peak output power ranges from 5 W to 175 W when operated a 160 ns pulse width. Significant increases in peak power are attainable at shorter pulse widths. Applicant&#39;s laser diode bulb is useful for use in, without limitation, laser range finding, speed determination, light detection and ranging (“LIDAR”), optical fusing, collision avoidance, high speed switching, and weapons simulation. In certain of these laser diode embodiments, electromagnetic energy emitting devices  120  emit radiation having wavelengths of about 805, 870, 905, 1550 nanometers, and combinations thereof. 
   In certain embodiments, Applicant&#39;s bulb includes one or more electromagnetic energy emitting devices  120  which emit radiation in the microwave frequency spectrum, i.e. frequencies from about 10 8  hertz to about 10 11  hertz. In certain embodiments, Applicant&#39;s bulb includes one or more electromagnetic energy emitting devices  120  which emit radiation in the infrared frequency spectrum, i.e. frequencies from about 10 11  hertz to about 10 14  hertz. In certain embodiments, Applicant&#39;s bulb includes one or more electromagnetic energy emitting devices  120  which emit radiation in the ultraviolet frequency spectrum, i.e. frequencies from about 10 15  to about 10 16  hertz, and combinations thereof. 
   In certain embodiments, voltage converter assembly  110  converts DC power having a first voltage to DC power having a second voltage. In other embodiments, voltage converter assembly  110  converts AC power having a first voltage to DC power having a second voltage. In certain embodiments, the first voltage is greater than the second voltage. In certain embodiments, the AC input power has a voltage between about 12 volts and about 250 volts. In certain embodiments, the second voltage is greater than the first voltage, i.e. voltage converter assembly  110  comprises what is sometimes called a “boost” converter. 
   In certain embodiments, voltage converter assembly provides a regulated output. By “regulated output,” Applicant means the nominal output voltage changes less than about plus or minus 10 percent during operation as long as the input voltage is within a specified range. In certain embodiments, assembly  10  comprises a step-up/step-down converter which provides a regulated output of about 5V where the specified input voltage range is between about 0.8V and about 6V. 
   Referring now to  FIG. 12 , in step  1210  Applicant&#39;s light bulb provides DC power having a first voltage to converter  110 . In step  1220 , Applicant&#39;s light bulb converts that input DC power into AC power having the first voltage and a first frequency. Referring to  FIG. 11 , curve  1110  shows that first AC power having voltage V 0  and frequency  1120 . In certain embodiments, frequency  1120  is greater than about 10,000 hertz. In certain embodiments, frequency  1120  is greater than about 100,000 hertz. In certain embodiments, frequency  1120  is greater than about 500,000 hertz. 
   In step  1230 , Applicant&#39;s light bulb transforms the first AC power into second AC power having the first frequency and a second voltage. In step  1240 , Applicant&#39;s light bulb rectifies the second AC power into second DC power having the second frequency. 
   In certain embodiments, voltage converter  110  comprises one or more capacitors for transferring charge to boost the voltage. In certain embodiments, converter  110  uses inductors as energy storage elements to boost the voltage. 
   In certain embodiments, in step  1250  Applicant&#39;s light bulb regulates the second DC power provided by converter  110 . Referring to  FIG. 2 , in certain embodiments converter  110  includes device  210  comprising an NCP1402 SN50T 2, which is a DC to DC converter with a voltage regulator. In the embodiment of  FIG. 2 , converter  110  further includes a 47 microhenry inductor  220  and an On Semiconductor MBR0520LT1 Schottky diode  230 . 
   In certain embodiments, in step  1260  Applicant&#39;s light bulb filters the second DC power. In certain embodiments, Applicant&#39;s apparatus  110  further includes capacitor  240  to filter out a residual AC ripple component of the second DC power provided by converter  210 . In certain embodiments; capacitor  240  comprises a low ESR Tantalum capacitor. In certain embodiments, capacitor  240  can be eliminated because the flicker of the lighting device will be well above human perception due to the high switching frequency of the converter  120 . 
   In certain embodiments, in step  1270 , Applicant&#39;s light bulb converts the second DC power to third DC power having a lower current. Referring again to  FIGS. 1 and 2 , the one or more light emitting devices  120  of  FIG. 1  comprise LEDs  255 ,  265 , and  275 , in  FIG. 2 . The embodiment of  FIG. 2  includes resistors  250 ,  260 , and  270 , that limit current through LEDs  255 ,  265 , and  275 , respectively. In certain embodiments, LEDs  255 ,  265 , and  275 , are closely matched in voltage drop, and therefore, a single resistor is used for all three LEDs. In certain embodiments, resistors  255 ,  265 , and/or  275 , comprise a negative temperature coefficient to limit the current through the LEDs with increasing temperature. This is desirable if the LEDs are operated at a high current level close to the design point of those LEDs. 
   The value of the current limiting resistors is determined by several factors including the output voltage converter  110  ( FIG. 1 ). By designing the output voltage of the regulator to substantially match the voltage drop of the LEDs, the power lost in the current limiting resistors is minimized. Additionally the current density in the inductor can be used as a limiting factor in the maximum power delivered by the converter to limit the current through the LEDs. 
   An alternative embodiment of the invention uses current sources in place of the current limiting resistors. The current source or sources could also be integrated on a single substrate with the DC to DC converter in the optimal design. Likewise, the current sources could be separate components. 
     FIG. 14  shows embodiment  1400  of Applicant&#39;s apparatus  100  using the components of  FIGS. 1 and 2 . Flexible circuit substrate  1410  comprises a non-electrically conductive polymeric film. In certain embodiments, substrate  1410  comprises a polyimide film. In certain embodiments, substrate  1410  comprises a polyamideimide film. Substrate  1410  comprises one or more circuit tracks and one or more power conductors disposed thereon. As those skilled in the art will appreciate, the circuitry and power conductors may be formed using conventional techniques. Substrate  1410  includes three portions separated by two fold lines. Portion  1420  comprises a first end segment, portion  1430  comprises a middle segment, and portion  1440  comprises a second end portion. Fold line  1425  is disposed between, end portion  1420  and middle portion  1430 . Fold line  1435  is disposed between end portion  1440  and middle portion  1430 . 
   Inductor  220  is disposed on end portion  1420 . Diode  230 , converter  210 , and capacitor  240  are disposed on the middle portion  1430 . One or more LEDs  1450  are disposed on portion  1440 . Substrate  1410  can be folded along fold lines  1425  and  1435 , and then disposed with the base portion of Applicant&#39;s light bulb. In the embodiment of  FIG. 14 , a single resistor  250  ( FIG. 2 ) limits the current to the LEDs. Although  FIG. 14  shows use of two fold lines, in other embodiments Applicant&#39;s flexible substrate  1410  includes more than two fold lines. In certain embodiments, Applicant&#39;s flexible substrate  1410  includes a single fold line. 
   Other packaging embodiments include using a wire lead frame. In these embodiments, the entire assembly is inserted in and soldered to, a metal base portion. That base portion is then encapsulated with a non-conductive filler. Such an encapsulant comprises, for example, an epoxy resin. In other embodiments, the components of  FIG. 2  are disposed on a custom lead frame, and that entire assembly is then encapsulated in a polymeric material. That encapsulated device is then inserted into the base component of Applicant&#39;s apparatus. 
   In certain embodiments, the base assembly comprises a single, molded, three-dimensional circuit substrate. In these embodiments, components  110 ,  150 ,  160 ,  170 ,  180 , and optionally  1310 , are disposed internally within that molded portion, and contacts  130  and  140  are disposed on the surface of that molded portion. 
   The performance of Applicant&#39;s flashlight comprising light bulb  110  differs dramatically from prior art hand-carried lighting devices. As those skilled in the art will appreciate, the voltage level provided by a series of batteries decreases over time. Referring now to  FIG. 3 , curve  310  represents the voltage level of DC power provided by a series of batteries. Early on at time T 0 , the DC power has a voltage. V 0 , where at time T 0  the one or more batteries have been used for about one percent (1%) of their useful lifetimes. At time T 1 , where time T 1  comprises about 90 percent of the batteries&#39; maximum useful lifetime, that voltage has decreased to voltage V 1 . 
   As a general matter, the voltage provided by one or more battery cells is inversely proportional to the duration of use.  FIG. 3  shows a linear relationship between the voltage provided as a function of time. In certain embodiments, that relationship may be more complex, i.e. a quadratic function, a cubic function, and the like. 
   Referring now to  FIG. 4 , curve  410  represents the intensity in Lumens of the visible light emitted from one or more light emitting elements/devices receiving the DC power of curve  310  ( FIG. 3 ). Initially, i.e. at time T 0 , the one or more light emitting elements/devices emit visible light having an intensity L 0 . However, at time T 1  that intensity has diminished to level L 1 , where L 1  is less than 50 percent of L 0 . As a general matter, the intensity of radiation emitted provided by an electromagnetic energy emitter powered by one or more battery cells is inversely proportional to the duration of use.  FIG. 4  shows a linear relationship between the intensity of radiation emitted as a function of time. In certain embodiments, that relationship may be more complex, i.e. a quadratic function, a cubic function, and the like. 
   Referring now to  FIG. 5 , curve  510  represents the voltage level of the DC power provided to one or more light emitting elements/devices  120  ( FIG. 1 ) by converter assembly  110  ( FIG. 1 ). Initially, i.e. at time T 0 , the DC power provided has a voltage V 0 . At time T 1 , where time T 1  comprises about 90 percent of the batteries&#39; maximum useful lifetime, that voltage is still substantially equal to voltage V 1 . By substantially equal, Applicant means within plus or minus about ten percent (10%). Referring now to  FIG. 6 , curve  610  represents the intensity in Lumens of the visible light emitted from one or more one or more light emitting elements/devices receiving the DC power of curve  510  ( FIG. 5 ). Initially, i.e. at time T 0 , the one or more light emitting elements/devices emit visible light having an intensity L 0 . At time T 1  that the one or more light emitting elements/devices emits visible light having intensity L 1 , where L 1  is substantially equal to L 0 . By “one or more light emitting elements/devices,” Applicant means one or more incandescent elements, one or more LEDS, or combinations thereof. 
   Referring again to  FIG. 1 , power input terminals  130  and  140  are disposed on the surface of housing  190 . Although  FIG. 1  shows power input terminals  130  and  140  disposed on the same side of housing  190  and adjacent to one another, the configuration of  FIG. 1  is not limiting. In certain embodiments, power input terminals  130  and  140  are located on different sides/surfaces of housing  190 . In certain embodiments, power input terminals  130  and  140  comprise portions of a single power input plug or module. In certain embodiments, housing  110  further comprises a base portion and a cover portion. 
   Power input terminal  130  is attached to conductor  150 . Conductor  150  is disposed within housing  190  and interconnects with power converter assembly  110 . Power input terminal  140  is attached to conductor  160 . Conductor  160  is disposed within housing  190  and interconnects with power converter assembly  110 . As those skilled in the art will appreciate, the base portion may be configured as necessary to engage with any one of the plurality of well-known industry standard socket light bulb socket types. 
   In certain embodiments, the components disposed within and on housing  100  occupy the same physical form and volume as do standard incandescent light bulbs, and engage in standard sockets to fit into standard lighting fixtures such as flashlights and lanterns. The lamp base can be either a stamped metal that is used in “flashlight” bulbs today, such as an Edison screw style or a bayonet base, for example. In certain embodiments, power input terminals  130  and  140  are disposed on the outer surface of the base portion, and conductors  150  and  160  along with converter assembly  110  are internally disposed within the base portion. 
   In certain embodiments Applicant&#39;s light bulb apparatus includes a translucent or transparent cover for the lighting elements. In these embodiments, the cover portion surrounds and protects the one or more light emitting elements/devices. In certain embodiments, converter  110  may be disposed within the cover portion of Applicant&#39;s light bulb. 
   In certain embodiments, the cover portion diffuses the light emitted from the one or more light emitting elements/devices  120 . Such a cover portion diffuses and combines the light emitted by the one or more light emitting elements/devices to provide a pleasing appearance. In the embodiments where the entire unit is constructed as a plastic injection molding the plastic cover is just a design element of the whole. The plastic cover can also be made to have a decorative appearance when the bulb will be decorative in function. 
   For example,  FIG. 7  shows embodiment  700  of Applicant&#39;s apparatus which includes bayonet mount base portion  710  and cover portion  720 . As those skilled in the art will appreciate, embodiment  700  is first pushed into a compatible socket and then twisted until locked in that socket. 
     FIG. 8  shows embodiment  800  of Applicant&#39;s apparatus which includes a regular or a mini-candelabra screw mount comprising base  810 . Cover portion  820  is formed in the shape of a candle flame. Referring now to  FIG. 13 , in certain embodiment  1300  Applicant&#39;s apparatus further includes microprocessor  1310  disposed between voltage converter  110  and plurality of LEDs  120 . Microprocessor  1310  receives the filtered, regulated DC power from converter  110  and supplies that DC power to individual LEDs based upon a program  1340  disposed within microprocessor  1310 . In certain embodiments, program  1340  provides DC power to individual LEDs comprising plurality of LEDs  120  such that the visual output of apparatus  1300  appears to comprise a candle flame. U.S. Pat. No. 5,924,784 teaches a method and apparatus to emit visible light simulating the appearance of a candle flame, and is hereby incorporated herein by reference. U.S. pending application having Ser. No. 09/783,374 teaches circuitry 
   By “microprocessor,” Applicant means a device that provides DC power to one or more, but not continuously to each, individual LED comprising plurality of LEDs  120 . In certain embodiments, microprocessor  1310  comprises a computer processor in combination with computer code, i.e. a combination of computer hardware and software to provide DC power to one or more, but not continuously to each, individual LED comprising plurality of LEDs  120 . In certain embodiments, microprocessor  1310  comprises an application specific integrated circuit comprising “firmware” to provides DC power to one or more, but not continuously to each, individual LED comprising plurality of LEDs  120 . 
     FIG. 9  shows embodiment  900  of Applicant&#39;s apparatus which includes screw-in mount base portion  910  and cover portion  920 . As those skilled in the art will appreciate, embodiment  900  is inserted into a compatible socket and rotated until locked in that socket. As those skilled in the art will appreciate, in certain embodiments base portion  910  has a size commonly referred to as a “medium” size. That medium size is larger in diameter than either the candelabra mount or mini-candelabra mount of  FIG. 8 . In certain embodiments base portion  910  has a size commonly referred-to as a “mogul” size, where that mogul mount has a diameter greater than the medium mount. 
     FIG. 10  shows embodiment  1000  of Applicant&#39;s apparatus which includes a two pin mount base portion  1010  and cover portion  1020 . As those skilled in the art will appreciate, base configuration  1010  is often used in, for example, projector bulbs, low voltage track lighting, and cable lighting systems. 
   While the preferred embodiments of the present invention have been illustrated in detail, it should be apparent that modifications and adaptations to those embodiments may occur to one skilled in the art without departing from the scope of the present invention as set forth in the following claims.