`
`IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
`
`In re Patent of:
`
`Lebens et al.
`
`U.S. Patent No.:
`
`6,095,661
`
`
`
`Issue Date:
`
`August 1, 2000
`
`Appl. Serial No.:
`
`09/044,559
`
`Filing Date:
`
`March 19, 1998
`
`Title:
`
`METHOD AND APPARATUS FOR AN L.E.D.
`
`FLASHLIGHT
`
`
`PETITION FOR INTER PARTES REVIEW OF UNITED STATES PATENT
`NO. 6,095,661 PURSUANT TO 35 U.S.C. §§ 311–319, 37 C.F.R. § 42
`
`
`Exhibit LG-1006
`
`U.S. Patent No. 4,499,525 (“Mallory”)
`
`

`

`[11] Patent Number:
`t9)
`United States Patent
`
` Mallory [45] Date of Patent:
`
`4,499,525
`Feb. 12, 1985
`
`[54] CONSTANT ILLUMINATION FLASHLIGHT
`.
`Inventor: Henry R. Mallory, Greenwich,
`Conn.
`[73] Assignee: Duracell Inc., Bethel, Conn
`nee:
`”
`,
`[21]
`App
`21] Appl. No.: 331,432
`[22] Filed:
`Dec. 16, 1981
`[SU]
`Ent, Ch3 oo eeeeteceseeeneeererentees F21V 23/00
`[52] US. C1.cee ecectesesesestenenssseees 362/157; 315/307;
`.
`323/299
`[58] Field of Search ............. 320/2, 13, 21; 323/282,
`323/284, 299; 362/205, 206, 208, 157; 363/124;
`315/307, 310, 311
`
`[75]
`
`[56]
`
`.
`
`Primary Examiner—William H. Beha, Jr.
`Attorney, Agent, or Firm—Ronald S. Cornell; Israel
`Nissenbaum
`[57]
`ABSTRACT
`.
`.
`A power supply circuit for generating a power pulse
`train for an incandescent bulb in a flashlight which
`results in a relatively constant illumination output from
`the flashlight despite the decline in output voltage from
`a battery power supply therefor during discharge. The
`power supply circuit operates to compensate for the
`lower output voliage from the battery power supply by
`increasing the duty cycle of the pulse train to provide
`References Cited
`wider pulse widths therein, and eventually the wider
`U.S. PATENT DOCUMENTS
`pulse widths merge into a DC power supply near the
`3,525,924
`8/1970 Atterholt ............
`-3073~ end of the useful service life of the battery power sup-
`......
`3,777,247 12/1973 Zellmer......
`eee 362/208 x
`_—~PLY-
`4,144,557
`3/1979 Kerr et al.
`ee 323/299 X
`4,230,970 10/1980 Potter et al.
`4,237,405 12/1980 Kells woe seeeeeeeee 323/299 X
`
`4,242,629 12/1980 Shuey oo... eeseesseeteeeeeeeee 323/282
`4,326,161
`4/1982 Kreinberg «oo... eee 323/299
`
`2 Claims, 3 Drawing Figures
`
`I4
`
`ropa Oo BOTMPS37008)
`24(4pF)
`20(MPS3702S)
`
`a:
`71
`
` —
`
`i8(MPS3702S)
`
`lO(PR2)
`
`i6(92PUO!)
`
`Exhibit LG-1006 Page 1
`
`LGELEM0002933
`
`Exhibit LG-1006 Page 1
`
`

`

`U.S. Patent
`
`Feb.12,1985
`
` Sheetlof2
`
`4,499,525
`
` lO(PR2)
`
`16(92PU01)
`
`
`
`44(MN9080 OR MN9I80)
`
`FIG.3
`
`Exhibit LG-1006 Page 2
`
`LGELEM0002934
`
`Exhibit LG-1006 Page 2
`
`

`

`U.S. Patent
`
`Feb. 12, 1985
`
`Sheet2of2
`
`4,499,525
`
`50
`
`OUTPUT
`
`40
`
`aoO
`
`LUMENS
`
`CONTINUOUS HOURS OF SERVICE
`
`FIG.2
`
`Exhibit LG-1006 Page 3
`
`LGELEM0002935
`
`Exhibit LG-1006 Page 3
`
`

`

`1
`
`4,499,525
`
`CONSTANT ILLUMINATION FLASHLIGHT
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates generally to a flashlight
`for providing a relatively constant illumination output
`overthe useful service life of batteries employed therein
`despite the relatively poor voltage maintenance charac-
`teristics of the batteries during discharge. More particu-
`larly the subject invention pertains to a simple and inex-
`pensive circuit for incorporation in a flashlight which
`providesa relatively constant power supply to an incan-
`descent bulb therein over substantially the entire useful
`service life of the flashlight batteries. The circuit gener-
`ates a pulse train for the incandescent lamp and provides
`a relatively constant power supply by varying the duty
`cycle thereof by generating pulses having a greater
`pulse width as the voltage from the power supply bat-
`teries declines.
`2. Discussion of the Prior Art
`Traditional batteries employed as a power supply for
`incandescent flashlights have very poor voltage mainte-
`nance characteristics over their useful service life. Tra-
`ditional batteries of the kind discussed herein typically
`include aqueous electrolyte, manganese dioxide batter-
`ies such as zinc carbon or zinc chloride batteries or
`manganese alkaline batteries. As an example, a conven-
`tional zinc carbon commercially designated 908 battery
`provides only four to four and one half hours of contin-
`uous service, with an initial illumination outputofforty-
`five lumens and a changein illumination overits useful
`life of approximately five to one, thereby producing an
`output near the end ofits service life of only nine lu-
`mens. Moreover, as the battery discharges the lower
`voltage results in a substantial filament color changein
`the incandescent bulb from an initial white light output
`to a noticeably yellow light output, which is considered
`to be a negative factor from a consumer acceptance
`point of view.
`Lithium based batteries now under extensive devel-
`opment in the art do not exhibit a four or more to one
`ratio decline in output voltage over their useful service
`life because of voltage maintenance characteristics
`which are vastly superior to zinc carbon, zinc chloride
`and manganese alkaline batteries. In view thereof,
`it
`would be desirable to provide a development such that
`traditionally powered flashlights remain competitive
`with the newly developing lithium powered lighting
`products.
`SUMMARYOF THE INVENTION
`
`is a primary object of the present
`it
`Accordingly,
`invention to provide a power supply circuit operated
`from a battery power supply which provides a rela-
`tively constant power output to a load over substan-
`tially the entire useful service life of the battery despite
`the relatively poor voltage maintenance characteristics
`thereof during discharge.
`A further object of the subject invention is the provi-
`sion of a circuit of the aforementioned type designed to
`powera load in the form of an incandescent bulb for a
`flashlight such that the result is a relatively constant
`iHumination output from the flashlight over the useful
`service life of the batteries employed therein.
`Yet another object of the present invention is a power
`supply circuit of the subject kind which operates almost
`entirely in a
`substantially nondissipative manner,
`
`20
`
`25
`
`40
`
`45
`
`50
`
`35
`
`60
`
`65
`
`2
`thereby resulting in a power supply circuit having very
`little internal powerloss.
`In accordance with the teachings herein, the present
`invention provides a circuit for generating a power
`pulse train for a load in the form of an incandescent bulb
`in a flashlight which results in a relatively constant
`illumination output from the flashlight despite the de-
`cline in output voltage from a battery power supply
`therefor during discharge. The power supply circuit
`basically operates to compensate for the lower output
`voltage from the battery power supply by increasing
`the duty cycle of the pulse train to provide wider pulse
`widths therein, and eventually the wider pulse widths
`merge into a DC power supply near the end of the
`useful service life of the battery power supply.
`Thecircuit includes a drive transistor having its emit-
`ter and collector coupled in series with the incandescent
`bulb and the battery power supply. A controlcircuit is
`coupled to the base of the drive transistor in a mannerto
`cause it to generate a pulse train in which the duty cycle
`thereof is
`increased by providing pulses having a
`greater pulse width as the voltage from the battery
`power supply declines during discharge.
`In this ar-
`rangementthe rated voltage of the incandescent lampis
`preferably approximately half the rated voltage of the
`battery supply, which is normally an aqueous electro-
`lyte manganese dioxide battery. The drive transistoris
`selected to have a high beta characteristic and is driven
`in a nondissipative mode in whichit is either in a fully
`conductive, saturated state or in a nonconductivestate,
`such that power dissipation in the drive transistor in
`partially conductive modes is avoided.
`In a preferred embodiment, the control circuit com-
`prises first and second control transistors coupled to-
`gether in a complementary manner such that only one
`control transistor is conducting at a time. An output of
`the first control transistor is coupled to the base of the
`drive transistor to drive it in a saturated mode when the
`first control transistor is conducting. The second tran-
`sistor functions as an inhibit transistor having an output
`thereof coupled to the base ofthe first control transistor
`to render it nonconductive whenthe inhibit transistoris
`conducting. An RC timing network is coupled to the
`base of the inhibit transistor to control the frequency of
`the pulse train generated by the circuit. In greater de-
`tail, the drive transistor comprises an NPN transistor,
`and the first and second control transistors are PNP
`transistors coupled in a common emitter circuit. The
`common emitter connection is coupled directly to the
`anode of the battery while the collector of the first
`control transistor is coupled to the base of the drive
`transistor. At least one diode functions as a voltage
`threshold circuit, and is coupled between the collector
`of the drive transistor and the base of the inhibit transis-
`tor, such that when the voltage of the threshold circuit
`is exceeded, the inhibit transistor is turned on, which
`results in both the first control transistor and the drive
`transistor being rendered nonconductive.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing objects and advantages of the present
`invention for a circuit for a constant illumination flash-
`light may be more readily understood by oneskilled in
`the art with reference being had to the following de-
`tailed description of several preferred embodiments
`thereof, taken in conjunction with the accompanying
`drawings, in which:
`
`Exhibit LG-1006 Page 4
`
`LGELEM0002936
`
`Exhibit LG-1006 Page 4
`
`

`

`4,499,525
`
`3
`FIG. 1 is an electrical schematic of a first embodi-
`ment of a circuit for a constant illumination flashlight
`constructed pursuant to the teachings of the present
`invention;
`FIG. 2 illustrates two curves of illumination output
`versus continuous hours of service, thefirst of whichis
`for a typicalprior art flashlight and the second of which
`is for a flashlight incorporating the circuit of FIG. 1;
`and
`FIG.3 illustrates an electrical schematic, with only a
`difference in component selection, for a second exem-
`plary embodiment of a circuit for a constant illumina-
`tion flashlight constructed pursuant to the teachings
`herein.
`
`DETAILED DESCRIPTION OF THE
`DRAWINGS
`
`Referring to the drawings in detail, FIG. 1 is an elec-
`trical schematic of a first embodiment ofa circuit de-
`signed to provide a substantially constant power output
`to a load in the form of an incandescent bulb 10, which
`in this embodiment is a commercially designated PR2
`bulb in standard usage in two D cell flashlights. A PR2
`bulb is normally rated at 2.38 volts and 500 millamps.
`The power supply therefor in this circuit is a 6 volt
`manganese dioxide battery 12, commercially designa-
`tion 908, which is a typical commercially available lan-
`tern battery with spring contacts on top thereof. The
`battery 12 is connectedin series with bulb 10 through an
`on-off switch 14 and the emitter and collector of an
`NPNdrive or pass transistor 16, commercial designa-
`tion 92PU01. In an arrangementofthis type, the lamp
`10 is selected to have approximately one half the rated
`voltage of the battery, primarily because operationis in
`a pulsed mode rather than a typical prior art DC mode.
`Transistor 16 is selected to have a high beta (8) char-
`acteristic, and its base current required during conduc-
`tion is approximately 10% of its emitter to collector
`current, which in the operation of the disclosed circuit
`is less than 500 milliamps. Accordingly, a base current
`of 30 milliamps or lessis sufficient to cause fully satu-
`rated conduction of the transistor 16.
`The pulsed conduction of transistor 16 is controlled
`by a circuit including first and second control transis-
`tors 18 and 20 which are connected in a common emit-
`ter arrangement, with the common emitters being cou-
`pled directly to the positive terminal or anode of battery
`12. The control
`transistors 18 and 20 are connected
`together in a complementary manner such that only one
`transistor at a time is conducting. The first control tran-
`sistor 18 is coupled by its collector to the base of drive
`transistor 16 to turn the latter on in a fully saturated,
`conductive mode when controltransistor 18 is conduct-
`ing. Transistor 18 is selected to supply an emitter cur-
`rent of 50 milliampsor less to the base of drive transistor
`16 to drive the latter in a fully saturated mode. The
`second control transistor 20 functionsas an inhibit tran-
`sistor relative to the first control transistor 18, with the
`collector of inhibit transistor 20 being coupled to the
`base ofthe first control transistor 18 to render the latter
`nonconductive when inhibit transistor 20 is conducting.
`Commercially designated MPS3702S PNP transistors
`are suitable for the first and second control transistors
`18 and 20.
`An RC timing network comprising resistor 22 and
`capacitor 24 is coupled to the base of inhibit transistor
`20, and their values control the frequency of the pulse
`train generated by the power supply circuit. The fre-
`
`4
`quency of the pulse train should be higher than the
`retinal persistence of the human eye such thatit appears
`to the user of the flashlight that the illumination there-
`from is constant. In general, the frequency of the gener-
`ated pulse train should be greater than 50 hertz, and 5
`kilohertz is a good practical frequency for a flashlight
`powersupply circuit of this type. In the illustrated em-
`bodiment resistor 22 is rated at 1.8 kilo-ohms while
`capacitator 24 is rated at 5 microfarads and 3 volts.
`A voltage threshold circuit in the form of three di-
`odes 26 is coupled between the collector of drive tran-
`sistor 16 and the base of inhibit transistor 20, and func-
`tions in a manner to turn inhibit transistor 20 on when
`the voltage at the drive transistor 16 exceeds the prede-
`termined threshold of the diodes 26. In this circuit each
`diode 26 has a threshold of 0.8 volts, and accordingly
`the cumulative threshold voltage of the three diodes in
`series is 2.4 volts. In alternative embodiments, other
`types of threshold circuits could be utilized. For exam-
`ple, each diode could have a lesser or greater threshold
`voltage, and moreorless diodes could be utilized, or in
`some circuits zener diodes may be suitable.
`Theresistors 28, 30, 32 and 34 are selected to establish
`suitable biasing voltages throughout the circuit, and
`their values in this circuit are shown in parentheses in
`FIG. 1. A capacitor 36 has been added to the circuit as
`it results in improved performance thereof, but is not
`necessary for its operation. The constant power supply
`circuit of the present invention is shown in FIG. 1 as
`being encompassed by dashed line 38, while the more
`conventional components of a flashlight are shown
`outside the dashed line 38. However, it should bereal-
`ized that in a conventionalflashlight, a PR2 bulb would
`not be utilized with a 908 battery as this type of bulb is
`not designed to accept the full DC powerof a fully
`charged 908 battery.
`The circuit operates as follows. Closure of switch 14
`applies operational voltages to transistor 18 which re-
`sults in its conduction and the application of a conduc-
`tive voltage and current to the base of drive transistor
`16, which results in it being switched into a saturated
`conductive state, thereby applying almost the full volt-
`age of battery 12 (minus a small voltage drop of approx-
`imately 4 volt across transistor 16) across lamp 10 at the
`leading edge of a pulse in the pulse train. Transistor 16
`continues conducting until the voltage at its collector
`exceeds the threshold of 2.4 volts of the three series
`connected diodes 26, at which time an activating volt-
`age is applied through diodes 26 and resistor 28 to the
`base of inhibit transistor 20, thereby causing saturated
`conduction of transistor 20 and also charging of capaci-
`tor 24. Conduction of transistor 20 applies a reverse bias
`to the base of control transistor 18, thereby terminating
`its conduction and also terminating conduction of drive
`transistor 16 at the trailing edge of a pulse in the pulse
`train. Capacitor 24 discharges through resistor 22,
`thereby removing the forward bias voltage from its base
`and terminating conduction of inhibit
`transistor 20.
`Termination of conduction of inhibit transistor 20 al-
`lows control
`transistor 18 to conduct again,
`thereby
`driving transistor 18 into saturated condition at
`the
`leading edge of the next pulse in the pulse train, etc.
`The circuit continues supplying a power pulse train
`to lamp 10 in this manner as the voltage supplied by
`battery 12 gradually declines because of its constant
`discharge. A decline in voltage of battery 12 results in a
`decrease in the amplitude of the voltage of each pulse
`(as that amplitude is slightly less than the voltage sup-
`
`15
`
`20
`
`35
`
`40
`
`45
`
`30
`
`35
`
`60
`
`65
`
`Exhibit LG-1006 Page 5
`
`LGELEM0002937
`
`Exhibit LG-1006 Page 5
`
`

`

`4,499,525
`
`S
`
`5
`6
`plied by battery 12). However, a decline in voltage of
`high illumination output produced by the prior art ap-
`battery 12 also resuits in a concurrent increase in the
`proach.
`FIG. 3 is an electrical schematic of a second exem-
`time duration after initiation of the leading edge of a
`pulse, for the collector of transistor 16 to reach the
`plary embodiment of a circuit for a constant illumina-
`tion flashlight designed to produceslightly over twice
`threshold voltage across diodes 26, and hence a concur-
`the illumination output as the first embodiment from a
`rent increase of the pulse width of each pulse in the
`six volt
`lantern battery 44, commercia) designation
`train. The increase in pulse Width increases the duty
`MN9080 or MN9180, which is approximately twice as
`cycle of the pulse train and compensates for the lower-
`large as the 908 battery of the first embodiment. This
`ing of the voltage amplitude of the pulse train, such that
`circuit is designed to operate with a higher power lamp
`a substantially constant amount of poweris supplied to
`incandescent
`lamp 10 despite the gradual decline in
`46, commercial designation PRL2, rated at 2.75 volts
`voltage supplied by battery 12 as it discharges. The
`and 950 milliamperes, because of the higher power
`throughput of
`the circuit. The increased current
`pulse width of each pulse will gradually increase until
`the battery voltage declines to a point (at substantially
`through the circuit also requires a higher power drive
`the end ofits useful service life) at which the threshold
`transistor 48, commercial designation TIP29 or equiva-
`of diodes 26 is not exceeded, thereby resulting in contin-
`lent. The operation of this circuit is substantially the
`uous conduction of drive transistor 16. After reaching
`same as the operation of the first embodiment, and ac-
`this point, the circuit cannot compensate for a further
`cordingly will not be explained separately in detail
`herein. The following Table II supplies technical data
`decline in the output voltage of battery 12,
`thereby
`on the operation of the circuit of FIG. 3. This data was
`resulting in a gradual decrease in the power supplied to
`derived from measuring the illumination output of lamp
`lamp 10.
`The following Table I supplies technical data on the
`46, the voltage output of battery 44, and the frequency
`operation of the circuit of FIG. 1. This data was derived
`of the output pulse train. The average current of the
`pulse train and the power figures were then derived
`from measuring the illumination output of bulb 10, the
`voltage output of battery 12 and the frequency of the 25 from the measured parameters.
` TABLEII
`BATTERY
`LAMP VOLTS
`POWER SUPPLY
`LUMENS
`TRUE
`pC
`DC
`DC
`
`VOLTS KHZ=WATTSMA WATTS LUMENS AVER. RMS
`
`
`
`6.0
`5203.12
`«2.73
`24.6
`154
`1.00
`7.88
`5.75
`5423.12
`237
`158
`271.
`1.08
`7.60
`5.50
`578
`3.58
`23.3
`163
`2.69
`1.02
`6.45
`5.00
`6803.25
`22.5
`1.76
`2.68
`(1.08
`6.92
`45
`M8
`3.37
`22.9
`196-269
`1,12
`6.80
`4.0
`g50
`3.40
`24.5
`2.27.
`2.74
`1.06
`7.21
`35
`1045
`3.66
`28.8
`2.85
`2.86
`cont.
`7.87
`3.25
`1035
`3.36
`24.7
`2.74
`2.78
`com.
`7.35
`3.0
`998
`2.99
`17.2
`2.51
`2.52
`cont.
`5.75
`
`915 2.29 6.5 2.02 2.04 cont,2.5 2.84
`
`
`
`
`
`
`
`output pulse train. The average current of the pulse
`train and the powerfigures were then computed on the
`basis of these measurements.
` TABLEI
`Lumens
`per
`Watt
`Lumens
`Khz
`Watts
`MA
`Volts
`75
`10.8
`5.2
`1.44
`228
`6.3
`73
`10.3
`5.2
`141
`235
`6.0
`6.89
`9.3
`5.7
`1.35
`245
`5.5
`6.56
`8.6
`6.1
`1.31
`262
`5.0
`6.21
`VT
`7.2
`1.24
`310
`4.0
`6.37
`79
`6.5
`1.24
`412
`3.0
`6.72
`8.4
`Cont.
`1.25
`498
`2.5
`
`
`
`
`
`442 188 Cont, 3.62.0 4.09
`
`45
`
`FIG.2 illustrates two curvesofillumination output of
`a flashlight bulb versus continuous hours of service. A
`first curve 40 showsthe illumination output ofa typical
`prior art flashlight wherein a six volt zinc carbon lan-
`tern battery, commercial designation 908, is discharged
`directly through a suitable incandescent lamp, such as a
`908 commercial designation bulb. A second curve 42
`illustrates the illumination output produced by bulb 10
`in the circuit of FIG. 1. As illustrated by these curves,
`the constant illumination circuit produces about twice
`the useful service hours as the prior art approach. Of
`course, as also illustrated by the curves this increase in
`useful service hours is achieved bysacrificing the initial
`
`65
`
`While several embodiments and variations of the
`present invention for a circuit for a constant illumina-
`tion flashlight are described in detail herein, it should be
`apparentthat the disclosure and teachings of the present
`invention will suggest manyalternative designs to those
`skilled in the art. For instance, the circuits could be
`easily modified to provide a flashing illumination out-
`put.
`Whatis claimed is:
`1. A portable flashlight designed to provide a rela-
`tively constant illumination output over the useful ser-
`vice life of the battery power supply therefor, despite a
`relatively poor battery maintenance characteristic dur-
`ing discharge, comprising an incandescent
`lamp for
`providing illumination, a circuit for providing relatively
`constant electrical power to the incandescent lamp over
`substantially the entire useful life of at least one power
`supply battery, having a relatively poor voltage mainte-
`nance characteristic during discharge, said circuit in-
`cluding a drive transistor having the incandescent lamp
`coupled in series with the emitter and collector of the
`drive transistor and further coupled in series with said
`battery power supply, said circuit further including a
`control circuit including first and second control tran-
`sistors coupled in a complementary manner such that
`only one control transistor is conducting at a time, said
`first control transistor being coupled to the base of said
`
`Exhibit LG-1006 Page 6
`
`LGELEM0002938
`
`Exhibit LG-1006 Page 6
`
`

`

`4,499,525
`
`7
`drive transistor, to drive it into a saturated conductive
`mode when said first control transistor is conducting,
`and said second control transistor being an inhibit tran-
`sistor having a drive output thereof coupled to the base
`of said first control transistor to turn it off when said
`inhibit
`transistor is conducting, wherein said control
`circuit causes said drive transistor to generate a current
`pulse train in which the duty cycle thereofis increased,
`by providing current pulses having a greater pulse
`width to compensate for a lesser pulse amplitude, as the
`voltage from the power supply declines during its dis-
`charge to provide relatively constant electrical power
`to the incandescent lamp over substantially the entire
`useful life of the battery power supply, wherein said
`drive transistor has a relatively high beta characteristic
`and is driven by said control circuit in a non-dissipative
`
`8
`mannerin substantially either a fully conductive state or
`a fully non-conductive state to produce the pulsetrain,
`whereby powerdissipation in the drive transistor dur-
`ing partially conductive modes is substantially elimi-
`nated, and wherein an RC timing network is coupled to
`the base of said inhibit transistor for controlling the
`frequency of the pulse train generated by the circuit.
`2. A portable flashlight as in claim 1, wherein said
`drive transistor comprises an NPN transistor, and said
`first and second control transistors comprise PNP tran-
`sistors coupled in a common emitter circuit, coupled
`directly to the anode ofsaid at least one battery, with
`the collector of said first control transistor coupled to
`the base of said drive transistor.
`*
`*
`a
`*
`*
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Exhibit LG-1006 Page 7
`
`LGELEM0002939
`
`Exhibit LG-1006 Page 7
`
`