AU2008100631B4 - Improved High Intensity LED Flashlight - Google Patents

Description

AUSTRALIA Patents Act 1990 Complete Specification Innovation Patent High Intensity LED Flashlight The following statement is a full description of this invention, including the best method of performing it known to us: High Intensity LED Flashlight Background During the past decade (1998 to 2008) there have been improvements in high performance flashlights (torches). Early flashlights used plain Incandescent, Krypton, Xenon or Halogen miniature incandescent globes. In the late 1990's the first white LED based flashlights appeared, mostly based upon 1 or more white 3mm or 5mm diameter LEDs of low power (usually less than 1 watt and mostly with a current requirement of 20 50ma). To move to significantly higher power it is necessary to get rid of the heat in order to maintain the reliability of the LED(s), so the packages of the new High Brightness LEDs (HB LEDs) have become more complex, and adapted for heat dissipation. Packages for state-of-the-art high power LEDs bear little resemblance to early LEDs (see, for example fig 3 for pictures of early low power LEDs). Fig 4 shows a late model HB LED emitter, and fig 5 shows a late model multi-die emitter mounted on a Metal cored printed circuit board which assists in draining the heat away from the LED emitter. Up until the late 1990's, most high performance flashlights used Krypton, Xenon, or Quartz Halogen globes as a source of white light illumination. About the year 2001, Welch Allyn Corporation (USA) released compact low voltage metal halide (MH) ballast/lamp assemblies, which were taken up firstly by underwater flashlight manufacturers to bring a new high performance in underwater lighting for scuba divers. Compact MH lighting provided a big boost in the efficiency and output of light, which lessened the need for scuba divers to carry bulky battery packs. Following on from the scuba diving field, compact MH lights were also adapted for bicycle use, finding a market especially in off road mountain bike type applications. Whilst compact MH lighting was a big step forward there were problems with the fragility of the MH lamps and the associated ballasts. Other manufacturers have produced compact MH assemblies since, but a more reliable, robust and efficient solution has been found by the use of white HB LEDs, which can have lifetimes of up to 50,000 hours. It is only in the years 2006-2007 that the manufacturers of white HB LED's have been able to substantially increase the reliability and output power of these white HB LED's, so that white HB LED's consuming 8-21 watts of power and producing output light levels of 200 to 1100 lumens have been made available. Additionally, there recently is the capability to make HB LED's with emitters that have multiple dice that are individually addressable electrically and which can have different colours of light output from each of the individual dice of an emitter.

Brief description of the drawings/attachments Fig 1 is an example of a common Tactical type flashlight utilizing a white high brightness LED. Fig 2 is an example of the applicants' prior art halogen diving flashlight with remote battery pack. Fig 3 is a collection of earlier type (Non-High Brightness) LEDs in the common sizes of 5 mm, T1.3/4, 3 mm and T1 packages. (The third LED from the right is a Tri-colour LED). Fig 4 is a Seoul Semiconductor (SSC) white P4 HB LED emitter (single die emitter). Fig 5 is a 4 dice (2 series-2 parallel) emitter mounted on a star shaped printed circuit board (pcb). Fig 6 is a 6 dice (3 series-2 parallel) emitter mounted on a star shaped pcb. Fig 7 is a SSC P7 emitter- a multi-die white HB LED emitter (with 4 parallel dice). Fig 8 is a Cree XLamp-MCE electrically individually addressable die (4 dice) LED emitter. Fig 9 is a Perkin Elmer "Build Your Own colours" emitter with 4 electrically individually addressable dice. Fig 10 is an example of a Boost type solution for the electronic driver circuit using a Zetex ZXSC400 boost switching regulator. Fig 11 is an example Buck type solution for the electronic driver circuit using a National Semiconductor LM3401 Buck switching regulator.

Detailed description and preferred embodiments HB LED's are usually composed of 1 or more "dice" placed in a single emitter. Single die white HB LED emitters are presently limited in their output, and as of May 2008, the highest output single die white emitter known to the Applicants is a Cree XRE7090 (240 lumens at 1,000ma driving current). Fig 4 shows a Seoul Semiconductor (SSC) SSC P4 emitter- a single die 4 white HB LED with power requirements of 3.6v dc 1000ma to produce 240 lumens of light (This is the same emitter as used in the Cree XRE7090). Higher brightness white HB LED's are available which utilize multiple dice 5, 6 and 7 arranged in a single emitter housing. The usual voltage range for a single White LED die is about 3.2 to 3.6v dc. For multiple dies in a single emitter housing, the dice have previously been arranged in a series configuration, or series-parallel configuration whereby the individual die are all connected electrically internally and only one external electrical connection method is possible. For example, the Osram Ostar white HB LED's use a series-parallel configuration 5, 6. A 12-watt white Ostar emitter has 6 dice in a 3 series-2 parallel configuration 6 resulting in an 11.7v 1000ma power requirement and a lumens output of 400 lumens. As only one possible electrical connection is possible the designer of a flashlight is limited to providing a supply of 11.7v dc. Fig 5 shows a 4 dice (2 series-2 parallel) HB emitter mounted on a star shaped pcb and fig 6 shows a 6 dice (3 series-2 parallel) emitter mounted on a star shaped pcb. Recently (February 27, 2008), Seoul Semiconductor Corporation (SSC) released a very high performance white HB LED- the SSC P7 fig 7, that has high efficiency of output power. The currently highest available output in a SSC P7 HB LED is a "C bin" selection, which has a maximum output of 900 lumens when driven at its recommended maximum power of 3.6v dc and 2800ma. This provides an efficiency of about 90 lumens for each watt of power consumed. It would seem that the main market for this type of HB LED is replacing incandescent bulbs in buildings, as the output of this LED is higher than a standard 60-watt incandescent bulb. This level of efficiency outperforms most other manufacturer's white HB LED's, which currently feature up to approximately 50 lumens per watt efficiency. The arrangement of the dice in the emitter in a SSC P7 is a "quad die all in parallel" (internally connected dice, not electrically individually addressable). That is, the 4 dice used are wired in parallel 7 and mounted in the same single emitter fig 7- the first HB LED available to be produced in this design. This has resulted in a more reliable and easier to power (from a lower voltage) HB LED. However, the higher current needed to drive this lower voltage has proven to be a problem for portable flashlight design as few battery pivvoI IU 1I1%LI V1 11% UI IV I % UILn %,Uo I 1 U n I oAIOL L Vi VVIUo LvI lu l U1 VVIuI 11 1 LI un0 VVAry tL-.VV voltage, but High constant current). Additionally, the use of very high power HB LED's in flashlights used above water presents very significant problems with the amount of heat generated when running the flashlights at full power. The issues of driving and heat removal for an underwater flashlight using a "quad die all in parallel SSC P7 led" are addressed by the applicants Australian innovation patent application no: 2008100451 "Improved Underwater LED Flashlight". Fig 7 shows a SSC P7 emitter- a multi-die white HB LED emitter (with 4 parallel dice) with power requirements of 3.6v dc 2800ma to produce 900 lumens of light. Fig 8 shows a Cree XLamp-MCE emitter- a multi-die white HB LED emitter (with 4 electrically individually addressable dice) with power requirements of 3.5v dc 700ma per die to provide an output of 200 lumens per die (advance notice by Cree as of May 27, 2008)- giving a total output of 800 lumens per emitter. Fig 9 shows a Perkin Elmer Aculed multicolour HB LED emitter with 4 differently coloured electrically individually addressable dice mounted within a single emitter. Prior art for white HB LED flashlights has been to place 1, 2 or more separate single die HB LEDs in a flashlight, thus taking up more space when multiple LEDs are used and making the overall diameter of the flashlight larger. Additionally, this has made it very difficult to provide a focusing/angle function to the flashlight as each separate white HB LED emitter has to have its own lense/reflector system which all have to operate dependently and in unison. Conversely, with a single-emitter multiple-die HB LED, the overall dimensions are much smaller than when using multiple LEDs, and only one lense/reflector system needs to be incorporated to provide focusing/angle capability, thus keeping the complexity, manufacturing difficulty, size and price minimized, when compared to, say, 3 or 4 smaller output HB LEDs each with a single die. Fig 1 is an example of a common Tactical type flashlight utilizing a single white HB LED, and fig 2 shows an example of the Applicants' prior art halogen diving flashlight with remote battery pack 2. In the field of portable flashlights, no flashlight utilizing one or more HB LED's with electrically individually addressable dice in a single emitter currently exists.

One of the advantages of using HB LED's with individually addressable dice within a single emitter is that the voltage requirements can be varied to assist manufacture and also a consumer's availability of batteries. For example, in a Cree XLamp MC-E, the 4 dice in a single emitter could be wired in Series producing a power requirement at full load of 4x3.5=14v dc 700ma. Alternatively, the dice could be all wired in parallel (requiring power of 3.5v dc 2800ma (4x700ma=2800ma). Or any other combination of series and parallel (eg: "2 series- 2 parallel" 2x3.5vdc 2x 700ma = 7.Ovdc 1400ma). This flexibility of power requirement can assist the manufacturer in reducing multiple designs across a range of flashlights/battery configurations and make it easier for a consumer to use the most economical batteries rather than those batteries that fit a normal fixed voltage/current HB LED. The flexibility of electrically individually addressable dice also provides multiple uses of the Flashlight such as a multi-colour signaling strobe unit, as the individual dice in the emitter can be operated in a Flash mode. A Flash mode is a short high brightness pulse and with HB led's can actually be at a higher current than the normal operating conditions for continual use, thus providing a suitable emergency type strobe beacon type function. An S.O.S. signal for example could be pre-programmed in the Flashlight to be accessed through the normal switching of the Flashlight. A further advantage exists in that when multiple electrically individually addressable dice in a single emitter are used, there exists the redundancy that should one or more of the dice in the emitter fail prematurely, then the other dice can continue to function, which can be advantageous in an emergency situation or when a user is on an extended mission/exploration. Other advantages are available when using dice of different colours which are each electrically individually addressable within a HB LED emitter. Such an HB LED emitter is currently available from Perkin Elmer Corporation (USA) under their ACULED (4 dice in a single emitter) model range. The ACULED models are available as stock items and also as DYO (Do Your Own) designs. A DYO design allows the flexibility to order an ACULED with any combination of 4 colours in the 4 dice of the emitter. The colours could be all the same, or any combination from White, Ultra-Violet (UV), Blue, Green, Red, and Infrared (IR) available in various tints. Thus an all White, or perhaps all Red design could be used. Alternatively, 3 White dice could be used, with the 4th die Red; and the 4th Red die being used in an emergency flashing sequence. Another design could be, say, 2 White dice and 2 UV dice; with the 2 White dice being used during a scuba diver's night diving and switching to the 2 UV dice to illuminate special UV Fluorescing corals only visible in the dark with a UV stimulating source.

A further variation for Military applications could see all 4 dice of different colour with usage as follows: White for general illumination, Red or Green to preserve the user's night vision for reading of maps and signaling, IR for covert night vision signaling with IR night vision equipment. Additionally a Programmed sequence of signals in any combination of colours/intervals could be used: such program being either pre-programmed by the manufacturer or programmed by the individual user. Another use would be for Firefighters and Emergency Workers in situations of smoke or chemical clouds. In different fire/smoke/chemical situations the composition of the smoke/cloud/chemicals can attenuate the standard "white" light beam, and in these situations it can be advantageous to be able to switch to a Yellow light output which often provides a better light penetration than "white" light. Of course, a flashlight with the invention could also be supplied with any combination of colours if the conditions were known for a particular range of uses in advance. There also exists the "ultimate" solution of being able to produce a full spectrum of colours from an emitter comprised of at least 3 dice of say Red, Green, and Blue colours, to give a RGB type output when suitably driven. Another example would be a for a Police/Investigative type flashlight using multiple colours whereby the electrically individually addressable dice of the HB LED(s) emitter are White, UV(A), UV(B) and Red. The White could be for general use, the two UV types could be selectively used for detecting forensic type material such as blood and semen stains, and the Red could be used to preserve the user's night vision. Alternatively a Green colour could be substituted for one of the other colours to assist in Blood detection. Once the choice of using HB LED(s) with electrically individually addressable dice in a single emitter is made, the method of electrically driving the HB LED(s) needs to be considered. There are at least 4 ways to electrically drive a HB LED 1 By direct voltage, with or without a "dropping resistor", from a battery(s). 2 By boosting the voltage from a source that is lower than that required by the HB LED. (Boost configuration) 3 By reducing the voltage from a source that is higher than the HB LED voltage. (Buck configuration) 4 By a combination of reducing and boosting the voltage when the source is higher than the HB LED voltage, but perhaps lower later on when the battery voltage drops through use. (Eq: Buck-Boost, SEPIC, Flvback, Invertina, or other variations).

In all cases though, the drive current should be limited to that recommended for the particular HB LED being used, and preferably predominantly regulated at a Constant Current to maintain even brightness during the run time. In method 1 above, it is difficult to achieve this and can result in efficiency losses and either lower than optimum output of light, or damage to the emitter. A variation of the Buck circuit is to use a Voltage Regulator circuit arranged to produce a constant current, however this is less than optimal as it often wastes/burns off the excess voltage as extra heat which then has to be dispersed away. Even if a Low Drop Out Voltage Regulator is used to more closely match the voltage of the HB LED, this can still present problems as most batteries will drop in voltage during use and this will affect the output of the light. This type of circuit is less efficient in general than the normal Buck Switching type circuit, or the Boost, Buck-Boost, SEPIC, etc.. type circuits. As a single White LED die usually needs about 3.2-3.6v dc, a Boost circuit utilizing a voltage less than say 3.6v dc, would normally only be built with 1-3 alkaline or nickel cadmium(Nicd)/ nickel metal hydride (Nimh) battery cells of at least AA, or more preferably sub-C, C or D size. A typical D size Nimh cell has about 9ah capacity resulting in a 3-cell pack (3.6v dc) providing a run time for a 10-watt HB LED of about 3 hours after allowing for circuit inefficiencies. Such a battery pack would be useful for a 4 dice-single-emitter White LED underwater flashlight with the electrically individually addressable dice connected in any combination of parallel, series, or series/parallel, and the Boost circuit providing the appropriate voltage-current requirements. Preferably a voltage higher than 3.6v would be used (or that voltage higher than the method of connecting the electrically individually addressable dice of the emitter) so that a Buck circuit configuration could be implemented, which is in general more efficient and simpler in design than Boost, Boost-Buck, SEPIC, or other boosting type circuits. A voltage maximum of 12 volts dc is a useful and safe limit for general purposes, however higher dc voltages can be used if the requirement is for very long running time or if the higher voltage is more readily available. Suitable battery configurations would be 4 or more Alkaline disposable cells of C or D size: 4 or more AA to F size nickel cadmium or nickel metal hydride cells: or preferablv at IIUCO L Z_-I..ILI HIUH I I IV.I I % I JI I VL JV~. CA G1 U Zr V 1 I I I I1II1 II lIi HUH I I %.CAVpA%.ILY CAH I CaH I JIUU 11 1 series (or series-parallel and 4 or more cells) for a minimum output voltage that is in general at least 0.5v dc higher than the way the electrically individually addressable dice of the emitter are electrically connected. It should also be remembered that it is good design practice to allow for the lower part of the batteries voltage cycle when calculating the voltage requirements. Thus, it is normal to consider the low voltage cut-off point of 0.9v dc per cell when designing with nickel metal hydride batteries so that the batteries are protected from damage before being drained below 0.9v/cell towards the end of a run. The preferred embodiment for a hand held "High Intensity Led Flashlight" with White HB LED(s) and electrically individually addressable dice for each single emitter(s) would use a pair of Lithium Ion 18650 cells (each 3.6v dc. 2400ma) wired in series with the usual inbuilt safety protection circuit, and the electrically individually addressable dice of the emitter being powered in parallel with the option of individual powering of each of the dice of the emitter supervised by a microprocessor cpu chip. The preferred battery configuration embodiment for a Remote battery pack type White HB LED with electrically individually addressable dice for each single emitter(s) in a flashlight is 8 sub-C or C cell Nickel metal hydride cells wired in series producing an output of 9.6-10.0v dc with a capacity of 3300-4500mah . For a Nickel metal hydride design it would be advantageous to provide a "low voltage cut-off" in the driver electronic circuit to protect the batteries from deep discharge, which can quickly damage nickel metal hydride batteries. Referring to fig 2 again, substitution of the halogen lamp head 1 depicted, with a similar sized aluminium lamp head with White HB LED and electrically individually addressable dice (running a single Cree XLamp MC-E at full output of 800 lumens) results in virtually no change in overall size of the unit, but the running time for, the flashlight increases about 330% from 50 minutes to about 165 minutes with similar light output. An example of a Boost type circuit utilizing a Zetex brand ZXSC400 LED driver boost converter chip is shown in fig 10. In fig 10 the circuit is configured to provide the drive power for a 4 dice-electrically-individually addressable-emitter 8 with the dice Series connected (The LED emitter is shown schematically with only the main series connections for the wiring). The battery supply voltage is in the range 5.5-8.0v dc, and the output is 14v dc nominal, 700ma constant current.

/-% I IU I 1 ICAI 1,I I PUI IL V.I I I I I %F ,V.UIU U01 CA L.JVVOI.JL %.,II %'U IL U LIIIZ.II I J I I IUI LIVI~ IU ~ ~ J~ chips/circuits. In this design, 4 separate ZXSC400 chips/circuits could individually power the 4 individual dice of a 4 dice electrically individually addressable emitter such as a Perkin Elmer ACULED fig 9. Depending on the voltage/current requirements of the colours of the electrically individually addressable dice used in the HB LED, slightly different peripheral components for each ZXSC400 circuit could set the appropriate constant current for each of the individual dice. This may be necessary as different colours of HB LED require different voltages. (eg: IR-1.2v dc, Red-2.2v dc, White 3.6v dc, etc...). A PIC16F688 cpu microprocessor chip could be used to read the switch(s) input from the user and then individually control the 4 dice to provide different colours and/or different signals such as Constant ON, Flash, Strobe, S.O.S. etc... The PIC16F688 microprocessor could be factory preprogrammed to read the users input signals and control the LED dice individually as required. It is also possible to use a single driver ic that can individually control the 4 dice in a 4 dice emitter thus reducing the complexity of using 4 individual sub-circuits. A Buck type solution for the electronic driver circuit is shown in fig 11, which shows a preferred circuit and all the components using a National Semiconductor LM3401 Buck switching regulator to provide an output current of 2800ma to drive an electrically individually addressable quad die White HB LED at 9.8 watts (the 4 dice in the emitter wired in a parallel configuration: 3.5v dc 2800ma) power input to give 800 lumens of white light output. The input voltage is in the range of 6-12v dc in the design of fig 11, but those skilled in the art would see that the circuit components could be adjusted for different voltage input/output ranges and different current outputs, as well as utilizing other manufacturers Buck type switching regulators or other future HB LED electrically individually addressable dice emitters. The design in fig 11 will run a Cree XLamp MC-E quad die White HB LED at 2800ma at full output of 800 lumens for the full battery capacity. Additionally, instead of/or in addition to the switch/cpu arrangements mentioned previously, a series of magnetic reed switches could be arranged on the driver printed circuit board, positioned to be operated via a rotary ring and magnet assembly around the flashlight. Upon rotating the rotary ring to a selective position, each magnetic reed switch is activated in turn selectively activating the signal for the particular colour/action needed. The other main problem associated with HB LED's is that they produce a lot of heat that must be carried away from the LED emitter very quickly, otherwise damage will occur to the LED reducing its lifetime and light quality dramatically.

rI IUCAL OiIF\ %i.,CAI I L)IU UOIUU II..I LI 1 l VVOI CAI G4 U %.,VI.J lLI U%.,LII..I I V..J LI I I IICA~I lI~jI IL I.U L V.J CA predominantly metal casing such as aluminium, along with mounting the HB LED(s) with a silicon or similar heat sink mounting paste (eg: "Artic Silver"), helps considerably in removing the heat from the heat sink/LED arrangement. Occasionally the user may use the flashlight in excessively warm conditions and the heat sink will not function as well as normal. Use of a thermistor or temperature sensor electronic integrated circuit can provide a feedback arrangement to the driver circuit to reduce the input power to the HB LED and the resultant heat generated and thus protect the HB LED from damage. The thermistor can be directly connected to the appropriate driver pin of the LED driver ic chip to provide a feedback from the temperature of the HB LED emitter and to respond by reducing the drive current and hence the temperature of the emitter to prevent damage to the emitter. Alternatively, or in addition, a cpu microprocessor such as a PIC16F688 could receive the feedback signal from a thermistor and adjust the drive current via control of the led driver ic, or alternatively by generating an appropriate Pulse Width Modulation (PWM) signal to vary the light output and hence the current consumption (ie: heat generated). It should be noted that some available off the shelf HB LED driver ic's have an inbuilt PWM function which can simplify the design process of reducing the current consumption proportionately to the heat generated and thus keep the emitter temperature within a safe range. An arrangement of "fins" on the outside of the preferably aluminium flashlight casing will provide an enhanced high efficiency heat drain from the HB LED(s) emitter, and thus the flashlight described will run at full capacity and full battery capability and with reduced tendency to overheat which would require reducing the light output of the flashlight. With the contradictory requirements of heat dissipitation and high output but not overheating, there is the option of providing an electrically individually addressable HB LED(s) emitter flashlight with "moderate" light output that in general will not overheat the flashlight in normal use (ie: not at the full capable output of the HB LED), and a "Peak" mode/switch that momentarily provides full output for a short time. Such a use would be most favorable in a "Tactical" situation as encountered by Police or Military forces where often a very bright output is needed for only a few seconds or maybe a minute or two. Generally speaking this very brief use of the HB LED emitter in this mode will not cause serious damage to the HB LED. An example would be a Tactical type Flashlight with all white electrically individually addressable dice on the HB LED(s) emitter (say a Cree XLamp MCE), that is set to run at say 350-500ma for normal use, and momentarily at the full load of 700ma (series connection of the dice). The "Peak" output could be accessed by a separate switch on the flashlight or alternatively via the main switch. An example of LI11 IVI.ULFUL VYI I1I I U0II I j CA IIC01 IIIJI IL VYILI I LI11 11UO1UIL III VI LII.II OH U CA %'..JI1 ZXIL..0I I IVI%..JL.. would be a "moderate" output of 450 lumens, and a "Peak" output of 800 lumens. There are generally 2 typical types of configurations of flashlights: those that are self contained with the housing, lamp, switch(es), electronics and batteries all in the one case (eg: fig 1); and less commonly, those with remote attached battery packs (eg: fig 2), where the Lamp head contains a housing with or without associated electronics and switch(es), a cable attaching the lamp head to the battery pack, and the battery pack containing the batteries and maybe electronics/switch(es). The purpose of the remote type system is to enable large battery capacities to be conveniently carried to provide a light weight hand piece, and to attach the remote battery case around the users waist or to be attached to the users equipment. A remote battery pack can provide very long running times of 10 or more hours. The above description of the invention reveals the advantages and methods of how to produce a reliable, High Intensity HB LED Flashlight utilizing a HB LED(s) with electrically individually addressable dice in the emitter(s). The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. For example, the functions provided by the electronic driver circuit may operate in Boost mode and also in Buck-Boost mode. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.