AU2008100451A4 - Improved Underwater LED Flashlight - Google Patents

Description

00

E

0 0

(N

j? in

O-

AUSTRALIA

Patents Act 1990 Complete Specification Innovation Patent Improved Underwater LED Flashlight The following statement is a full description of this invention, including the best method of performing it known to us: Improved Underwater LED Flashlight gO 00 Background During the past decade (1998 to 2008) there have been improvements in underwater Sflashlights, which are typically used by scuba divers.

Up until the late 1990's, most high performance underwater flashlights used krypton or quartz halogen globes as the source of illumination. About the year 2001, Welch Allyn In Corporation (USA) released compact low voltage metal halide (MH) ballast/lamp 0 assemblies, which were taken up by underwater flashlight manufacturers to bring a new performance in underwater lighting for scuba divers. Compact MH lighting provided a big o O boost in the output of light, which lessened the need for scuba divers to carry bulky battery c packs.

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 High Brightness Light Emitting diodes (HB LED), 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.

Brief description of the drawings/attachments Fig 1 is an example of the applicants' prior art halogen diving flashlight with remote battery pack.

Fig 2 is a Seoul Semiconductor (SSC) white P4 HB LED emitter.

Fig 3 is a 4 die (2 series-2 parallel) emitter mounted on a star shaped printed circuit board (pcb).

Fig 4 is a 6 die (3 series-2 parallel) emitter mounted on a star shaped pcb.

Fig 5 is a SSC P7 emitter- a single die white HB LED emitter (with 4 parallel dice).

Fig 6 is an example Buck type solution for the electronic driver circuit using a National Semiconductor LM3401 Buck switching regulator.

00oO 0Detailed 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 Shighest output single die white emitter is a Cree XRE7090 (240 lumens at 1,000ma driving current). Fig 2 shows a Seoul Semiconductor (SSC) SSC P4 emitter- a single die 4 white V- HB LED with power requirements of 3.6v dc 1000ma to produce 240 lumens of light (This 0 is the same emitter as the Cree XRE7090).

Higher brightness white HB LED's are available, which utilize multiple die (dice) 3,4 and 00 O arranged in a single emitter housing. The usual voltage range for a single LED die is c, about 3.2 to 3.6v dc. For multiple dies in a single emitter housing, the dice have been arranged in a series configuration, or series-parallel configuration. For example, the Osram Ostar white LED's use a series-parallel configuration 3, 4. A 12-watt white Ostar emitter has 6 dice in a 3 series-2 parallel configuration 4 resulting in an 11.7v 1000ma power requirement and a lumens output of 400 lumens.

Fig 3 shows a 4 die (2 series-2 parallel) emitter mounted on a star shaped pcb and fig 4 shows a 6 die (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 5, that has hitherto unmatched 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 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 other manufacturer's white HB LED's, which currently feature up to approximately 50 lumens per watt efficiency.

The arrangement of the emitter in a SSC P7 is a "quad die all in parallel". That is, the 4 dies used are wired in parallel 7 and mounted in the same single emitter fig 5- 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 powered electronic drive circuits currently exist to provide the full power in this way (Low voltage, but High constant current). Additionally, the use of 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.

00 0 C Fig 5 shows a SSC P7 emitter- a single die white HB LED emitter (with 4 parallel dice) with power requirements of 3.6v dc 2800ma to produce 900 lumens of light Prior art for white HB LED diving 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 V- difficult to provide a focusing/angle function to the flashlight as each separate white HB 0 LED emitter has to have its own lense/reflector system which all have to operate dependently.

00 Conversely, with a single multiple die HB LED, the overall dimensions are much smaller than using multiple LEDs, and only one lense/reflector system needs to be incorporated to provide focusing/angle capability, thus keeping the complexity, size and price minimized.

Fig 1 shows an example of the applicants' prior art halogen diving flashlight with remote battery pack 2.

In the field of diving flashlights, no diving flashlight capable of being waterproof deeper than 15 meters, utilizing one or more HB LED's of parallel arranged dice in a single emitter currently exists.

The invention described in this application provides solutions to this problem enabling the manufacture of reliable powerful underwater flashlights with reliable high efficiency parallel die HB LED emitter(s).

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. (Eg: Buck-Boost, SEPIC, Flyback, Inverting, 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 regulated at a Constant Current to maintain 00 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 wastes/burns off the excess V) voltage as extra heat which then has to be dispersed away. Even if a Low Drop Out 0 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 00 S output of the light. This type of circuit is less efficient in general than the normal Buck N Switching type circuit, or the Boost, Buck-Boost, SEPIC, etc.. type circuits.

As a single LED die is usually 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/ nickel metal hydride 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 an 8-cell pack (9.6v dc) providing a run time for a 10-watt HB LED of about 8 hours after allowing for circuit inefficiencies.

More preferably, a higher voltage than 3.6v would be used 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, 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 preferably at least 2-Lithium Ion cells of "18650 size and 2400mah minimum capacity" arranged in series (or series-parallel and 4 or more cells) for a minimum output voltage of 7.2 v. The preferred embodiment for a "Handheld" HB LED parallel die emitter(s) underwater flashlight 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 preferred embodiment for a Remote battery pack type HB LED parallel die emitter(s) underwater flashlight is 8 sub-C or C cell Nickel metal hydride cells wired in series. 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.

00 C Referring to fig 1 again, substitution of the halogen lamp head 1 depicted, with a similar sized aluminium HB LED parallel die lamp head results in virtually no change in overall size of the unit, but the running time for, the flashlight increases about 300% from minutes to about 145 minutes with similar light output.

A Buck type solution for the electronic driver circuit is shown in fig 6, which shows a preferred circuit and all the components using a National Semiconductor LM3401 Buck 0 switching regulator to provide an output current of 2800ma to drive a quad die HB LED at watts power input to give a 900 lumen white light output. The input voltage is in the Srange of 6-12v dc in the design of fig 6, 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 parallel dice emitters. This design will run the SSC P7 quad die HB LED at 2800ma at full output of 900 lumens for the full battery capacity.

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.

A heat sink can be used for this purpose, and construction of the underwater flashlight out of a predominantly metal case such as aluminium, along with mounting the HB LED with a silicon or similar heat sink mounting paste (eg: "Artic Silver"), helps considerably in removing the heat from the heat sink/LED arrangement as the water outside the flashlight acts to considerably remove the heat from the aluminium flashlight. Occasionally the user may use the flashlight on land or in excessively warm water and the heat sink will not function as well as when submerged in normal (15-30 degrees Celsius) water. 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 protects the white HB LED from damage.

An arrangement of "fins" on the outside of the preferably aluminium flashlight casing will provide an enhanced high efficiency heat drain, 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.

In construction of the flashlight housing for scuba diving use, it is usual to provide at least meters pressure proof design, 100 meters preferably, and 200+ meters occasionally.

O0 O-ring sealing and a generally circular design are the most preferred design for pressure 0 C proofing underwater diving flashlights. A design compression of 15-25% for the o-rings is sufficient to provide a 100-meter pressure proofing capability underwater.

In addition there are generally 2 typical types of configurations of underwater flashlightsthose that are self contained with the housing, lamp and batteries all in the one case, and those with remote attached battery packs (eg: see fig where the Lamp head contains a V- housing with or without associated electronics, a cable attaching the lamp head to the 0 battery pack, and the battery pack containing the batteries and maybe electronics. The purpose of the remote type system is to enable large battery capacities to be carried by a 00 Sscuba diver to provide a light weigh hand piece, and to attach the remote battery case around the divers waist or attached to the diver's scuba tank. A remote battery pack can provide very long running times of 10 or more hours underwater.

The above description of the invention reveals how to produce a reliable, high output HB LED type flashlight for scuba divers.

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 abovedescribed 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.