United States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,741,048
`
`Eccleston
`[45] Date of Patent:
`Apr. 21, 1998
`
`
`U500574 1 O48A
`
`
`
`
`..
`
`.
`
`5/1976 Nilsson et a1. .......................... 188/112
`7/1976 Tomecek et a].
`.. 303/24 c
`8/1976 Miller ...............
`340/753 X
`9/1976 Abrams et a].
`..
`...... 303/20
`9/1976 Tomecek et a1.
`.. 303/21
`6/1977 Eden ......................................... 303/24
`9/1977 Grossner et a1
`....................... 188/112
`4/1973 Bull et a1.
`303/106
`6/1978 Fleming et a].
`318/314
`8/1978 Hamby et al.
`318/318
`10/1978 Morton et a].
`318/341
`4/1979 Fukuma et al.
`318/317
`2/1980 Govaert et a].
`...... 363/21
`5/1981 Kawada et a1.
`318/434
`......
`5/1981 Kawada et a].
`......................... 318/434
`.
`.
`(L151 continued on next page.)
`FOREIGN PATENT DOCUMENTS
`0166670
`“1986 European Pat. Ofi.
`................... 13/74
`OTHER PUBLICATIONS
`
`3,955,652
`3,967,863
`3,978,371
`3,981,542
`3,981,544
`4,030,756
`4.050550
`4,084,859
`4,096,422
`4,104,570
`4,119,898
`4,151,450
`4,187,536
`4,268,781
`4,268,782
`
`[54] CONTROLLER FOR ELECTRIC BRAKING
`SYSTEM
`
`[75]
`
`Inventor: Lam-y Eccleston. Marshall, Mich.
`-
`.
`-
`~
`[73] ASSlgnec' $3353: fifgt'lnmmg Company.
`6
`S
`'
`1“ '
`
`[21] Appl. N0.: 350,499
`_
`Filed:
`
`[22]
`
`Dec. 6, 1994
`
`Related US. Application Data
`
`[63] Continuation of Ser. No. 218,837, Mar. 28, 1994, aban-
`doned, which is a continuation of Ser. No. 129,799, Sep. 30,
`1993, abandoned, which is a continuation of Ser. No.
`877,323, Apr, 30, 1992, abandoned, which is a continuation
`ofSer. No. 563,505,Aug. 7. 1990, Pat. No, 5,149,176, which
`18 a continuation-in-part 0f SCI. No. 390,617, Aug 7, 1989:
`P“ N“ 510501931
`
`[51]
`Im. c1.6 ...................................................... B60T 13/72
`[52] us. Cl. ................................................... 3113/7; 303/20
`
`[58] Field of Search
`................... 303/3, 15. 7. 20:
`188/112 R. 112 A: 340/753. 754
`‘
`,
`‘
`References Cited
`
`[56]
`
`US. PATENT DOCUMENTS
`
`2/1969 Thiele ....................................... 317/27
`3,427,506
`
`4/1969 Kelley
`.. 307/11
`3,437,826
`5/1969 Mason
`........ 318/331
`3,447,055
`
`7/1969 Cooper ..
`........ 318/332
`3,457,487
`
`12/1970 Rusch
`318/341
`3,551,774
`
`4/1971 Jacob
`303fl
`3,574,414
`
`6/1971 Reeves ..
`318/332
`3,584,282
`8/1971 Thiele
`318/341
`3,596,810
`
`8/1971 Blomenkamp
`................. 340/62
`3,601,794
`
`12/1971 Gurwicz ...............
`307/252 M
`3,629,615
`
`.......... 303/20
`6/1973 Pokrinchak et al
`3,738,710
`
`8/1973 Delay et a1.
`340/753 X
`3,754,121
`
`..
`12/1973 Podlewski et a].
`303/21 EB
`3,778,118
`12/1973 Marshall .................. 188/3 R
`3,780,832
`
`. 318/317
`12/1974 Smith
`3,855,511
`
`3,855,520 12/1974 Stich .....
`323/19
`9/1975 Lang et a].
`180/103
`3,908,782
`
`9/1975 Pittet, Jr. et a1.
`.
`.. 303/24
`3,909,075
`4/1976 Pittet, Jr. et a].
`......................... 303/24
`3,953,084
`
`.
`,4.1.21
`P
`D
`Id bMt
`1.19 ,
`.
`6
`83%;? “1g“ 5“ y
`0 0w 3
`85 pp 3
`“Linear Integrated Circuits," by Unitrode Integrated Cir-
`cuits.
`SemiConductor Products And Systems, 1985 by SGS Tech—
`nology and Service.
`Schaltnetztei1e—Motorsteuerungen und ihre speziellen Bau-
`teile, 1982 by Dr. AIfred Hiithig Verlag Heidelberg.
`
`Primary Examiner—Matthew C. Graham
`Attorney, Agent, or F[rm—Price. Heneveld, Cooper. DeWitt
`& Litton
`
`[57]
`
`ABSTRACT
`
`A vehicle brake controller includes a variable pulse—width
`modulator operating at a constant frequency and with a
`variab1e pulse width to provide control pulses to a MOSFET
`element which acmates vehicle braking. The controller
`further includes a visual indicator which displays diflerent
`colors to representatively indicate the amount of current
`applied to the brakes. and also to indicate whether an
`operable connection exists between the electronic controller
`and the vehicle brakes.
`
`12 Claims, 3 Drawing Sheets
`
`
`
`
`
`Curt - Exhibit 1015 - l
`
`Curt - Exhibit 1015 - 1
`
`

`

`5,741,048
`Page 2
`
`US. PATENT DOCUNIENTS
`
`4,291,259
`4,384.241
`4,389,602
`4,398,252
`
`9/1981 Marnmoto et a1.
`..................... 318/139
`5/1983 Stillhard .........
`318/317
`
`
`6/1983 Post ..
`318/341
`8/1983 Frail ........................................ 364/426
`
`4,688,029
`4,721,344
`4,726,627
`4,799,126
`4.856.850
`5,032.821
`
`.................. 340/753 X
`8/1987 Kawasaki et a].
`303/20
`1/1988 Frait et al.
`......
`
`303/20
`2/1988 Frait et al.
`
` 1/1989 Kruse et a1. . .. 361/101
`
`
`8/1989 Aichele et al.
`........................... 303/20
`7/1991 Domanico et a].
`..................... 350/440
`
`Curt - Exhibit 1015 - 2
`
`Curt - Exhibit 1015 - 2
`
`

`

`US. Patent
`
`Apr. 21, 1998
`
`Sheet 1 of 3
`
`5,741,048
`
`
`
`Curt - Exhibit 1015 - 3
`
`Curt - Exhibit 1015 - 3
`
`

`

`US. Patent
`
`Apr. 21, 1998
`
`Sheet 2 of 3
`
`5,741,048
`
`IZV
`
`FIG.2
`
`Curt - Exhibit 1015 - 4
`
`Curt - Exhibit 1015 - 4
`
`

`

`US. Patent
`
`Apr. 21, 1998
`
`Sheet 3 of 3
`
`5,741,048
`
`
`
`Curt - Exhibit 1015 - 5
`
`Curt - Exhibit 1015 - 5
`
`

`

`5.741.048
`
`1
`CONTROLLER FOR ELECTRIC BRAKING
`SYSTEM
`
`CROSS-REFERENCE TO RELATED
`APPUCATILON
`
`BACKGROUND OF THE INVENTION
`
`10
`
`15
`
`20
`
`25
`
`30
`
`This application is a continuation of application Sen No.
`08/218.837 filed on Mar. 28, 1994. now abandoned which
`was a continuation of prior application Ser. No. 08/129.799
`filed on Sep. 30. 1993 (now abandoned), which was a
`continuation of prior application Ser. No. 07/877.323 filed
`on Apr. 30. 1992 (now abandoned), which was a continua-
`tion of prior application Ser. No. 563.505 filed on Aug. 7.
`1990 (now U.S. Pat. No. 5,149,176), which application is a
`continuation-in-part of prior application Ser. No. 390.617
`flied Aug. 7. 1989 now U.S. Pat. No. 5.050.937.
`
`2
`a given situation. On the other hand, where pulsating brake
`excitation is utilized, variable-frequency systems usually
`include some actuation frequencies which unfortunately
`complement or reinforce resonant frequencies in the vehicle
`5 braking systems (whether mechanical, electro-mechanic証
`or electromagnetic in nature), with the result being
`instability, brake chatter. etc. Indeed, even pulse width-
`modulated (variable-pulse-width) constant-frequency sys-
`tems sometimes utilize operational frequencies which have
`such adverse characteristics, and are likely to have other
`disadvantages as well.
`One common incident of practically all state of the art
`electronic 玩ake-system controllers is the fact that they
`utilize, and in fact require. interconnection with the vehicle
`brake light circuit. This is conventionally felt to be essential
`in such systems. because it is widely thought that the
`contr（皿er must be kept disabled. i.e.. in a condition where it
`is not capable of providing braking excitation, except for the
`specific instances when either the manu証 control switch is
`'Fhis invention relates to controllers for elecirically-
`actuated or else the towing vehicle brakes are actually being
`actuated braking systems, such as those used to apply the
`applied. as verified by the presence of the brake light signal.
`The main reason underl戸ng this conviction is the fact that
`brakes on towed vehicles (i.e.. trailers) in response to
`the stability of prior art inertial sensors and control circ血ts
`commands from the towing vehicle. More particularly. the
`invention relates to electronic controllers for braking sys-
`has not been sufficiently reliable under any and all potential
`tems of the general type just noted which operate in response
`operating conditions to preclude inadvertent and undesired
`to inertial sensors and/or manually-actuated switches or the
`brake actuation under various conditions, for example. in
`like to energize the electric brake-actuation components of
`response to such extraneous effects as rough road surfaces.
`such systems in a particular controlled manner.
`etc.
`While using the tow vehicle brake II帥tsign証for the
`In the past. electric 比ake-system controllers have pro-
`gressed from relatively simple and crude circuiいV血chwere
`purpose just noted did prove to be a reasonably effective
`measure for coping with the problem of inadvertent brake
`little more than manually-variable power switches, operated
`actuation, this measure nonetheless created a number of
`directly by the driver, to various types of comparatively
`problems itself, as well as involving at least some inherent
`improved and more sophisticated systems which apply
`uncertainties. For example, mechanical or electrical failure
`either continuous or pulsing drive excitation to the electro-
`in the brake light circuit entirely extraneous to actual towing
`magnetic brake shoe actuators located at the trailer wheels.
`vehicle performance could result in the loss of all trailer
`For example. U.S. Pat. No. 3.738.710 shows a series current
`35
`braking. Furthermore, with the increasing sophistication of
`re魯」lator which integrates an 鼠こtuation signal obtained from
`modem-day ve駈cles, the brake light circuit has grown
`the tow血g ye粒cle brake iiゆt circi血and applies continuol昭
`increasin母y complex. since it is now directly intercoupled
`braking excitation whose magnitude is basically propor-
`with such other systems as electronic cruise controls; anti-
`tion証to the length of time the towing vehicle brakes are
`skid braking systems; etc.. and as a res皿t each such system
`actuated, or in any event, proportional to the length of time
`40 becomes more interdependent and subject to failure or
`the brake lights are energized in the towing vehicle. Most
`malfunction caused by the others. Furthermore, while cruise
`other control circuits for electric brakes apply pulsing cxci-
`controls, anti-skid braking systems. etc.. are usually built
`tation to the brake-actuating electromagnets. since it is
`into the tow vehicle at the factory. this is not true of trailer
`widely thought that such pulsing excitation helps obviate
`brake controllers, which are aftermarket devices installed by
`lock-up or s亙dding of the trailer brakes. Some such con-
`others. Thus, with the increasing comple虹ty of vehicles and
`trollers utilize a constant pulse-width applied at varying
`systems related to their brakes and brake-light actuation
`frequencies which increase in accordance with the amount
`systems. it becomes increasingly more difficult, as well as
`more ris珂 and potentially damag蛇. to physically breach
`of braking desired, while others utilize a constant-frequency
`variable-pulse-width form of excita止n, for similar reasons.
`the ねctory-installed wiring in order to 血terconnect the
`For example. see prior U.S. Pat. Nos. 3,909.075 and 3.953,
`50
`brake light circuit with aftermarket devices.
`084. addressed to the second such type of system, together
`In addition, prior art electronic controllers for electric
`with U.S. Pat. No. 3.967.863, which is directed to the first
`brake systems have had a number of other disadvantages and
`such type of system. all of which utilize both inertial-sensing
`limitations, in particular operating inefficiencies attended by
`and inanually-actuatable input devices and apply braking
`the use of excess power and the production of excess heat.
`excitation as a function of whichever such device is con-
`Thus, typical prior art systems utilize resistive-type current-
`sensors for 山tecting the presence of excess braking current
`trolhng.
`and initiating various forms of interruptors. for safeり
`While all of the aforementioned state of the art-type
`systems no doubt have their individual advantages and
`purposes. and to prevent controller burn-out. Further, state
`favorable features, most also involve cert証n characteristic
`of the art controllers utilize inefficient drive components
`limitations or undesirable characteristics. For example. con-
`60 such as bi-polar power transistors and the like, thereby using
`tinuous braking excitation is indeed likely to promote trailer
`excess power and requiring extensive heat-dissipation
`brake lock-up, and that is a most undesirable event since it
`means. i.e., heat sinks.
`brings about a marked decrease in braking efficiency and
`loss of operator control. Further, the mere length of time
`during which the brake light circuit happens to be energized
`may very well not accurately represent the desirable mag-
`nitude of braking force to 比 applied to the trailer brakes in
`
`45
`
`55
`
`65
`
`BRIEF DESCRIPt'ION AND FEATURES OF THE
`PRESENT INVENTION
`The present invention effectively resolves many. indeed
`most, of the problems described above which characterize
`
`Curt - Exhibit 1015 - 6
`
`

`

`5.741.048
`
`o
`I
`
`4
`FIG. 2 is a schematic circuit diagram showing a second
`embodiment of an electronic controller in accordance with
`the invention.
`FIG. 3 is a schematic circuit diagram showing a further
`S embodiment of an electronic controller in accordance with
`the invention.
`
`3
`prior art controllers. In accordance with the invention, new
`and more effective controllers are provided through the
`combined effect of a number of 血stinct features which vary
`in both concept and implementation from those found in
`prior art devices, and w血ch combine synergistically to
`provide electronic brake controllers which are both more
`effective and more efficient than those utilized heretofore.
`DESCRIPTION OF THE PREFERRED
`More particularly, the controllers of the present invention
`EMBODIMENTS
`are both more stable and more responsive to important
`Referring now to drawings. and the illustrative embodi-
`braking system criteria than prior controllers, and at the
`ments depicted therein, a first controller circuit is shown in
`same time they are far more energy-efficient and cooler in
`FIG. 1. the upper portion of the circ血t, designated generally
`operation. while 証so providing operation証 characteristics
`by the numeral 10. comprises the braking current control
`which avoid undesirable interaction with tow vehicle brak-
`portion of the circuit, while the lower portion, generally
`ing systems. More specific証ly considered, some of the more
`5designated by the numeral 12. comprises the novel braking
`1
`salient attributes of the present controllers include an
`current display-generation means. Referring first to the
`optional new form of interface for interconnecting with the
`braking current control portion of the circuit 10. the control
`tow vehicle 比ake hgm circuit, new and novd variableー
`circuit generally includes a detection and control portion 14
`pulse-width fixed repetition rate circuits which operate at
`shown at the left and, proceeding toward the right. includes
`high efficiency. effectiveness, and stability, and a new form
`20 a dual-slope integrator section 16. a variable-p吐se-width
`ofレaking current controller output driver 印ass element）げ
`modulator 18 which includes an integrated circuit 20 and
`垣帥efficiency, coupled with new concepts in braking cur-
`logic switch means 22 (both described in more detail
`rent detection and display, for increased operator awareness,
`hereinafteかand an ou中ut stage 24 comprising 山e afore-
`effectiveness, and operational flexibility.
`mentioned MOSFET elements, which may be single or
`In a still more particular sense, the present invention
`25 double in form as described hereinafter. As shown, the
`provides a new form of electronic controller for electric
`ouやut stage 24 has an ouやut conductor 26 which comprises
`braking systems which features a constant-frequency.
`the connection to the towed vehicle (trailer) brake actuators.
`variable-pulse-width mod吐ator which 血terac加 with the
`here symbolized 句the large induct加e winding labeled
`vehicle braking system through an N-channel power
`"LI ." it being understood that in actu祖 practice there will be
`MOSFET. which is the control element for the braking
`30 a number of individual such inductances in parallel. each
`current supplied to the electromagnets that actuate the
`comprising the electromagnet w駈ch actuates one set of
`brakes. The operation証 frequency for the controller is such
`brakes at one wheel, all wheels usually being controlled
`as to avoid resonance problems in the braking assemblies of
`simultaneously and 血a substanti証りidentical fashion・
`the trailer previously encountered in other systems. while at
`With first reference to the detection and control portion 14
`the same time facilitating efficient and effective component
`35 of the circuit 10. elements Dl and Q1 symbolize the
`operation. The N-channel power MOSFET acting as the pass
`signal-generating portions of the inertial sensor noted above.
`element has extremely low forward or "on" resistance, and
`which is most preferably in accordance with that described
`improves the efficiency of the output stage by on the order
`in copending application Ser. No. 07/390.280. ified May 24.
`of about ten times, in comparison to prior art systems. and
`1989. While an appropriate signal could, of course, be
`circuit efficiency is further augmented by the implementa-
`'10 provided by other than electro-optical elements, the latter do
`tion of a novel braking current-sensing technique. in which
`provide a preferred embodiment of the invention, particu-
`the voltage drop across the power MOSFEr during conduc-
`larly in combination with the inertial sensor of the copend-
`tion is sensed and used as a control signal. thereby elimi-
`ing application just described. Thus, in a preferred
`nating the lossy and heat-producing series resistances uti-
`embodiment, element Di comprises an infrared light-
`lized heretofore.
`45 emitting diode, and element Qi comprises a corresponding
`In accomplishing the foregoing goals. a novel power
`photoiransistor (both of which may desirably be imple-
`supply is utilized for driving the N-channel MOSFET. which
`mented by use of Motorola components MLED 71 and
`constitutes a distinct departure from prior art electric brake
`MRD 701. respectively). As will be understood, the basic
`controller concepts.
`purpose of circuit portion 14 is to provide an analog control
`Furthermore, the controller in accordance herewith may
`50 signal corresponding in magnitude to the extent of trailer
`optionally feature in combination with the aforementioned
`braking desired, and thus an integral portion of circuit 14 is
`constant-frequency variable-pulse-width circuit operation, a
`a manual switch Si. by which the towing vehicle operator
`new and novel MOSFEF interface for interconnecting with
`may manually initiate measured braking effects on the trailer
`the towing vehicle brake-light actuation circuit to avoid
`whenever desired, apart from the operation of the towing
`some of the significant problems and potential problems
`55 vehicle brakes and the corresponding inertial effects. In the
`encountered by users and manufacturers in interfacing with
`most preferred embodiment in accordance herewith, switch
`the towing vehicle brake light circuitry.
`Si comprises a membrane-type "touch pad" switch of an
`The foregoing features and attributes of the invention wifi
`appropriate commercially-available type. the use of which in
`become more apparent after contemplation of the ensuing
`such a braking controller is believed to constitute a novel
`more det証led description, particularly when considered with
`60 and desirable feature in and of itself. Apart from this.
`and in light of the accompanying drawings.
`however, it will be observed that both the inertial sensor
`components and the manually-actuated components are
`effectively coupled between mutually-shared supply and
`ground conductors 28 and 30. respectively, through poten-
`65 tiometers R2 and R3. respectively, with an interconnecting
`line 31 extending between the lower-voltage side of each
`such poten泳〕meter. As will be understood, potentiometer R2
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`In the accompanying drawings:
`FIG. 1 is a schematic circuit diagram showing a 鉦st
`embodiment of an electronic controller in accordance with
`the invention.
`
`Curt - Exhibit 1015 - 7
`
`

`

`5.741.048
`
`15
`
`10
`
`6
`5
`ment is accomplished, in the embodiment under
`is merely for the purpose of adjusting the operational range
`consideration, by use of a floating-ground "flying" power
`of the photoiransistor Qi. to avoid circuit performance
`supply which, in effect, doubles the available power level, so
`variation as a function of manufacturing tolerances in the
`as to make it possible to use N-channel MOSFET devices as
`optical components. Potentiometer R3. on the other hand,
`comprises a gain control for the entire control circuit 10.
`5output stages Q2 and Q3 (for example, by use of the
`commercially-av証lable N-channel devices identified as
`since it acts to set the level at which signals from the
`detection portion 14 are provided to the integrator portion
`#SMPSON05). Logic switch 22 thus functions as an integral
`16.
`part of this "flying" power supply by performing the nec-
`The du止slope integrator 16 comprises basic証ly capaci-
`essary switching, in conjunction with a "pull-up" circuit
`tor Cl. resistors R4 and RS. and diode D2; also, this
`comprising capacitor CS and diode D7. As illustrated, these
`integrating section works in conjunction with another inte-
`components are connected across output stages Q2 and Q3,
`grat血g section comprising capacitor C3 and re証戚or R7,血
`and between twelve volt supply conductor 28 and the
`a manner described more fully hereinafter. More
`floating ground conductor 30. the latter in fact providing the
`particularly. the signal from the detection and control section
`excitation appearing on output conductor 26 noted
`14 of the circuit is coupled from the movable con組ct of
`previou訂y. leading to the brake-actu証加n electromagnets
`potentiometer R3 to the first integrating section just no比d
`Li.
`and, due to the polarity of diode D2, together with the
`Somewhat more particularly. the operation of control
`operational characteristics of integrated circuit Ui. this
`circuit 10 is as follows. Internally, the non-inverting input of
`results in a comparatively slow and gradu司increase in
`the operational amp in integrated circuit Ui is tied to a 3.75
`control voltage (determined in essence by the time constant
`20 volt reference and, as noted above, the dual-slope integrator
`established by both resistors R4 and R5. together with
`16 connected between the detector and control section 14
`capacitor Cl). but with a much faster 直scharge time estab-
`and the PWM section 15 is connected to the inverting input
`lished in essence, by the value of only resistor R5 and
`of IC U!. i.e., on pin 3. Thus, in response to control voltages
`capacitor Cl, resistor R4 having been shunted out of opera-
`from circuit 14 calling for the application of braking current.
`the collector 可the internal op amp in IC U! is pulled down
`tion by diode D2). Preferably, the value of resistor RS is on
`25
`the order of only about fifteen percent of that of resistor R4.
`and divided by potentiometer R3. current being applied
`such that the charging time constant of the integrator is about
`through resistors RS and R4 at a rate determined by the
`1.5 seconds, whereas the discharge time is about 0.1 second.
`longer time constant of the dual-slope integrator 16. The
`Integrated circuit U! is utilized as a comparatively simple
`output of the internal op amp in IC Ui appears on pin 4
`30 山ereof. which is 山us affected by the time constant of 山e
`pulse-width modulator, and may be implemented by use of
`the commercial IC No. 5561, which basically includes an
`network including capacitor C3 and resistor R7. which
`internal operational amplifier, comparator, and sawtooth
`forms a second integrator. Thus. initially, current is drawn
`wave generator. As utilized in the present applic雌旬n. the
`out of the summing point represented by the inverting
`inverting input of the internal operation amplifier (pin 3) is
`terminal of the internal op amp. whose output thus responds
`coupled to integrator 16. in particular to the "low" side of
`35accordingly. The op amp output appearing on pin 4 is
`capacitor Cl. and to the common junction of resistor R7 and
`applied internally to a comparator which conducts a con-
`capacitor C3. The output of such internal "op amp" appears
`tinuing comparison of that signal to a standard sawtooth
`on pin 4, and is connected to the opposite common junction
`wave form, so as to continually change the proportion of
`of capacitor C3 and resistor R7. It will be observed that
`conduction. In accordance with the present application. a
`positive operating voltage ("B+") for the entire control
`40 pulse-repetition rate of approximately 300 Hz is chosen, to
`circuit 10 is provi山d on the aforementioned supply con-
`best complement the braking systems being actuated (i.e.. to
`best accommodate brake magnet peホrmance with maxim証
`ductor 28 which, among other connections, is coupled to pin
`1 of integrated circuit U!. As will be explained subsequently
`isolation from natural mechanical resonances typically
`血more detail, control circuitl'utilizes a "flying" power
`encountereの． Accordingly, the output from the PWM （に
`45 Ui). appearing on pin 7. constitutes a repetitive p吐se whose
`supply concept. in which conductor 30 functions as a
`width is a んnction of the control signal from circuit portion
`floating ground. and it will be noted that the latter is coupled
`14, as a function of the intern証 comparison with the
`to pin S of IC Ui through conductor 34. The primary output
`from integrated circuit U! appears on pin 7 thereof, and this
`aforementioned sawtooth wave. This output from pin 7 is
`is coupled to the logic switch means 22 by conductors 32
`inverted through the analog switch stage 22 and applied to
`(and its interconnecting branches 3乙1. 32b. 3ル, which are
`so the gate of output MOS 弔I' Q2 (and, where used, the second
`also connected to the B+ supply line 28 through resistor
`MOSFET Q3). to provide brake-actuating excitation on
`output conductor 妬.
`RU).
`The logic switch means 22 may be implemented, in
`As noted above, previous systems have used PNP
`accordance with the embodiment here under discussion, by
`transistors, with the emitter connected to battery positive
`a four-part analog switch, e.g., the commercially-available
`55 and the collector to the brake magnets. which in turn connect
`element designated by the identifier "CD4066." the four
`to ground. The base drive is applied by puffing base current
`operational components of which are illustrated separately
`from the transistor to ground. The base current out of the
`for conve血ence in FIG. 1 and designated "U2a. U2b. U2c."
`base causes collector current to flow, thereby energi血ng the
`brake magne飴. It would be somewhat analogous to this to
`etc. Basically. this compound switch operates in conjunction
`with the output from the pulse-width modulator (pin 7 of
`60 use a P-channel MOSFET in such circumstances, since one
`U!) to control conduction of the MOSFET output transistor
`could configure the circuit much the same as with the PNP
`Q2 (and, where higher levels of current are needed, a second
`transistor, with the source connected to battery positive and
`such MOSFET designated here as Q3. which is to be
`the drain connected to the brake magnets, which in turn
`understood as being optional, depending upon the level of
`connect to ground. However. P-channel MOSFETs of suf-
`current output needed).
`65 ficiently low "on" resistance and current-handling capacity
`As indicated previously, the output stages Q2 and Q3 are
`are simply not available as of this point in time. Paralleling
`preferably N-channel devices, whose use in this environ-
`higher-resistance devices would work, but the cost would be
`
`Curt - Exhibit 1015 - 8
`
`

`

`5.741.048
`
`5
`
`0
`1
`
`25
`
`30
`
`7
`8
`through resistor Rul and diode DS. plus resistor R6 and
`prohibitive. Accordingly, the present invention utilizes an
`N-channel MOSFET. even thouゆ this requires a substan-
`diode D3. which are coupled between pins 2 and 3 of the
`PWM IC U! and the logic switch 22. the output from the
`tially different and more involved circuit configuration. The
`configuration required is that of a sou衣】e-follower, but this
`PWM IC, on pin 7. being applied through logic switch 22 to
`the output transistors in stage 加. Thus, the circuit operates
`configuration requires that the MOSFET gate always be
`to inject current into pin 3 of the pulse-width modulator U!
`driven positive with respect to the source in order to cause
`when the duty cycle exceeds the selected level, and this
`conduction. Because the source rises to very near battery
`reduces the pulse-width from the PWM stage. It is. in effect,
`positive when the MOSFET is turned on, it is necessary that
`negative feedback, which establishes the maximum duty
`the gate be driven to a potential greater than battery poten-
`cycle of circuit Ui.
`tial. That is. an N-channel MOSFET requires that the gate be
`driven positive with respect to the source to cause conduc-
`Circuit duty cycle as a function of output current is an
`tion of the MOSFET. In a norm証 grounded-source
`important 旬nction played by the logic switch 22. Thus.
`when gate drive of output transistors Q2 and Q3 is applied
`configuration. gate drive is simply applied from a normal
`using section U2c of logic switch 22. section U2b is turned
`five to twenty volt source. The load would then be connected
`15 off as a clamp and section U2d is turned on as a voltage
`between the drain and the positive supply. and power would
`sensor, being connected to brake actuation line 妬 through
`be delivered any time the gate was above threshold. In the
`conductor 36 to the common connection node of output
`present case, it is required that the brake magnets operate
`against ground. mostly because of tradition in the automo-
`transistors Q2. Q3. and conductor 26. This in effect senses
`the voltage across output transistors Q2 (and, where used.
`tive industry. The high end must therefore be driven positive
`with respect to battery potenti証
`Q3), and applies the sensed voltage back as a signal to pin
`20
`6 of the PWM (i.e.. integrated circuit Ui). That voltage level
`Accordingly. where the preferred N-channel MOSFET
`is proportion証 to the current flow through the vehicle
`devices are utilized, so as to provide maximum circuit
`brakes, with a typical "on" resistance of an extremely low
`efficiency and minimum losses, the operational parameters
`level. The sensed voltage drop across Q2 and Q3 should be
`encountered in typical vehicle-trailer environments. involv-
`referenced to the MOSFET source, and therefore both U!
`ing a positive-ground twelve volt power supply. requires a
`and U3 are operated from the same flying supply, with their
`pull-up, "flying" supply which in effect doubles the available
`negative terminals common to the source. Because U2 is
`voltage level to provide above-rail drive to the MOSFET
`driven from U!, it 証so is referenced to the flying source.
`gate. In the circuit configuration shown in FIG. 1. the
`Accor血ngly, the pulse-width modulator 41 will turn off if
`MOSFEF gate supply is referenced to the voltage applied to
`current exceeds a pre-set limit, thereby establishing a
`supply conductor 28. but at a level which is effectively
`selected duty cycle which corresponds directly to the level
`increased through the operation of capacitor C4 and diode
`of current flow through the trailer brake electromagnets.
`D6. which is series-connected in supply line 28. Thus, when
`Furthermore, such turnoff provides an effective short-circuit
`output transistor Q2 (and Q3. where used) is non-
`protection for the brake magnet actuation line, Accordingly.
`conducting. capacitor C4 charges to the level present on
`35if the ou印ut transistors for any reason overheat and their
`conductor 28 through diode D6, through a charge path which
`conducting resistance rises accordingly. the current limit for
`includes the brake magnet coils Li. When the output tran-
`excitation to the brake magnets will be cut back
`sistors are turned on and conduct, the supply effectively rises
`correspondingly, to maint証n circuit performance.
`with the source because diode D6 then allows the positive
`The same voltage sensed and applied to the p吐se-width
`terminal of capacitor C4 to "bootstrap" up to a value of twice
`the applied B+. Since the gate drive for output MOSFETs Q2 40 modulator Ui as a measure of output current, as just
`
`and Q3 is supplied from conductor 28. through resistors R13
`described, is also applied to the display circuit 12, which
`and R14. the foregoing charge state of capacitor C4 causes
`preferably comprises an LED bar-graph driver U3. for
`example of the type known as an LM3914. which includes
`a corresponding supply condition to be present as gate drive.
`Of course, other voltage-doubling circuits are known and
`an internal voltage divider and a set of ten comparators. The
`resulting function is that as the voltage across ou叩ut Iran-
`could be used, but most others utilize more expensive
`compo