Abstract:
Improved light emitting diode (LED) vehicle headlamps having a dedicated daytime running lamp (DRL) component are described. In various embodiments, a combination Low Beam/DRL headlamp is provided, which uses pulse width modulation (PWM) detection to determine which of the two internal LED light sources (Low Beam or DRL) is powered on. If the Low Beam/DRL headlamp detects a PWM signal on the Low Beam voltage input then it switches to drive the DRL LEDs. If, alternatively, it detects a steady state input voltage then it switches to drive the Low Beam LEDs.

Description:
BACKGROUND 
       [0001]    A daytime running lamp (DRL, also referred to as a daytime running light) is a lighting device mounted on the front of a vehicle (automobiles and trucks), which typically emits white light. DRLs are intended for daytime use, to increase the visibility of the vehicle in daylight. Mandated in many countries, including Canada, DRLs automatically switch on when the engine is running (e.g., when the ignition key is turned, or optionally when the vehicle is moving forward or the forward gear is engaged), and turn off when the parking lights or headlights are switched on. 
         [0002]    Depending on prevailing regulations and vehicle equipment, the daytime running light function may be implemented by functionally specific lamps, by operating the low beam headlamps or fog lamps at full or reduced intensity, by operating the high beam headlamps at reduced intensity, or by steady-burning operation of the front turn signals at full or increased intensity (en.wikipedia.org/wiki/Daytime running lamp). 
         [0003]    Various studies have shown that daytime running lights reduce daytime accidents by making vehicles more conspicuous to other road users (e.g., to drivers of other vehicles and particularly to more vulnerable road users such as pedestrians, bicyclists, and motorcyclists). The greatest benefits are found with the more severe accidents, such as head-on and intersection crashes and collisions with pedestrians and cyclists (members.optusnet.com.au/carsafety/paine_drl_nrma_racv.pdf). However, various disadvantages have been identified, including waste of energy (increased fuel consumption), glare from wet roads, and increased frequency of lamp failure (e.g., when an existing low beam, high beam, or turn signal lamp is used for the DRL function and is run down faster due to the additional usage). 
         [0004]    Improved DRLs, which can increase the performance and effectiveness of these devices and as well as the safety benefits thereof, are needed. 
       SUMMARY 
       [0005]    The present invention provides, in various embodiments, an improved light emitting diode (LED) vehicle headlamp having a dedicated daytime running lamp (DRL) component. In some embodiments, the invention provides a combination Low Beam/DRL headlamp. 
         [0006]    In some embodiments, the Low Beam/DRL headlamp uses pulse width modulation (PWM) detection to determine which of the two internal LED light sources (Low Beam or DRL) is powered on. If the Low Beam/DRL headlamp detects a PWM signal on the Low Beam voltage input then it switches to drive the DRL LEDs. If, alternatively, it detects a steady state input voltage then it switches to drive the Low Beam LEDs. 
         [0007]    In some embodiments, the Low Beam/DRL headlamp requires no direct connection to the battery; rather, it operates off the Low Beam voltage input. It uses the Low Beam voltage input to determine if it is a dynamic input voltage (driving a DRL mode of operation) or a steady state input voltage (driving a Low Beam mode of operation), while additionally using that voltage input to power the Low Beam or DRL Beam LEDs embodied in the headlamp. 
         [0008]    In some embodiments, the Low Beam/DRL headlamp makes no attempt to determine if it is entering into a start-up condition; rather, it continually analyzes the input voltage for the Low Beam input (steady state) or DRL input (dynamic) and drives the appropriate beam based on that input. 
         [0009]    In some embodiments, the invention provides a daytime running lamp (DRL) component for a vehicle headlamp comprising: a support; at least one first LED mounted to the front of the support, said at least one first LED configured and arranged to output daytime running light under daylight conditions when the vehicle&#39;s engine is turned on; a clear lens mounted above the at least one first LED; at least one second LED mounted to the back of the support, said at least one second LED configured and arranged to output low beam head light when the low beam is turned on by the vehicle operator via a first vehicle switch; a three-contact power connector comprising a low beam contact, a high beam contact, and a ground; and a control circuit for operating the DRL component, said control circuit comprising a pulse width modulation (PWM) detection circuit configured to continuously monitor input voltage, to activate the at least one first LED when a PWM signal is detected on the low beam contact, and to activate the at least one second LED when a steady state voltage is detected on the low beam contact or the high beam contact. 
         [0010]    In some embodiments, the invention provides a dual beam headlamp, comprising a DRL component as described above mounted inside a headlamp chamber having a reflective inner back wall. 
         [0011]    In some embodiments, the invention provides a four lamp head light system, comprising two dual beam headlamps as described above, and two high beam lamps. 
         [0012]    In some embodiments, the invention provides a triple beam headlamp, comprising a DRL component as described above mounted inside a headlamp chamber having a reflective inner back wall and at least one third LED configured and arranged to output high beam head light when the high beam is turned on by the vehicle operator via a second vehicle switch. 
         [0013]    In some embodiments, the invention provides a two lamp headlight system, comprising two triple beam headlamps as described above. 
         [0014]    In some embodiments, dual beam or triple beam headlamp(s) as described above are configured to be mounted to a commercial truck, a motorcycle, and/or a recreational vehicle (RV). 
         [0015]    Additional features and advantages of the present invention are described further below. This summary section is meant merely to illustrate certain features of the invention, and is not meant to limit the scope of the invention in any way. The failure to discuss a specific feature or embodiment of the invention, or the inclusion of one or more features in this summary section, should not be construed to limit the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The foregoing summary, as well as the following detailed description of the preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the lighting devices of the present application, there are shown in the drawings preferred embodiments. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
           [0017]      FIG. 1A  shows a close-up front view of a DRL of the present invention, according to some embodiments.  FIGS. 1B-C  show back and side views of the DRL of  FIG. 1A , respectively. 
           [0018]      FIG. 2  is an exemplary diagram showing how the components of the DRL are assembled, according to some embodiments. 
           [0019]      FIG. 3A  shows a front view of a combination Low Beam/DRL headlamp of the present invention, according to some embodiments.  FIG. 3B  shows a top view of the device of  FIG. 3A . 
           [0020]      FIG. 4  shows a block diagram of an exemplary control circuit, according to some embodiments. 
           [0021]      FIGS. 5A and 5B  show a schematic diagram of the Low Beam/DRL headlamp circuit, according to some embodiments. 
           [0022]      FIG. 6  shows a front view of the Low Beam/DRL headlamp of  FIG. 3A , wherein a dynamic input voltage is applied to activate the DRL Beam LED output. 
           [0023]      FIG. 7  shows a front view of the Low Beam/DRL headlamp of  FIG. 3A , wherein a steady state input voltage is applied to activate the Low Beam LED output. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Certain localities require certain vehicles to have daytime running lights. In some systems, halogen-type low beam headlamps are used to produce a dimmer low beam light output that meets the DRL requirements. However, such systems have various disadvantages, including increased fuel consumption and increased lamp failure. 
         [0025]    In various preferred embodiments of the invention, a lighting device is provided having one or more light emitting diodes (LEDs) that are configured to be used specifically for DRL functionality, rather than operating an existing halogen lamp at reduced intensity to meet the designated DRL function as described above. Without wishing to be bound by theory, it is believed that isolating the DRL function specifically within the headlamp chamber increases the functionality of the DRL, furnishes stronger noticeability of illumination by its directionality, and hence augments safety during daytime driving. 
         [0026]      FIG. 1A  shows a close-up front view of a DRL component  100  of the present invention, according to some embodiments. Four DRL LEDs  122  are positioned behind a textured clear lens  104 . The DRL component includes two holes  130  to facilitate screw mounting inside a headlamp chamber.  FIGS. 1B-C  show back and side views of the DRL component of  FIG. 1A , respectively. As shown in  FIG. 1B , one or more low beam LEDs, such as low beam LED  140 , can be included on the back of the DRL component. Power connectors for DRL LEDs  122  and low beam LED  140 , such as the four-pin connectors shown at  124  and  126  respectively, can be mounted to a connector support  114  and secured by screw  128 . As shown in  FIG. 1C , in some embodiments, the main body of the DRL component is configured in an L shape comprising an obtuse angle, so that when the DRL component is mounted inside the headlamp chamber and activated the DRL beam emitted therefrom is directed in a downward-sloping direction. 
         [0027]      FIG. 2  is an exemplary diagram showing how the components of DRL component  200  are assembled, according to some embodiments. On the front face, four LEDs  222  on support  206  are mounted to central support  208  via screw  210  and covered by a textured clear lens  204 . Faceplate  202  is fitted thereto and secured to central support  208  via screw  212 . On the back face, PCB  216  is secured to central support  208  via screws  218 , and connector support  214 , with power connectors  224  and  226 , is secured to central support  208  by a screw (shown in  FIG. 1B  at numeral  128 ) fitted through hole  220 . Central support  208  comprises a light, strong, and/or economical material, such as, but not limited to, aluminum. 
         [0028]    In certain preferred embodiments, textured lens  204  comprises an array of raised rounded ridges aligned lengthwise on the outer surface of lens  204 . In other embodiments, other texture patterns may be used, on the outer and/or inner surface of the lens. Textured lens  204  can comprise any shape. In some embodiments, the shape and/or texture pattern of lens  204  may be selected, for example, according the number, arrangement, and/or type of DRL LEDs as described below, and/or other criteria. 
         [0029]    In some embodiments, the DRL component is part of a dual beam headlamp that provides both a DRL function and a low beam headlamp function.  FIG. 3A  shows a front view of a Low Beam/DRL headlamp device  390  of the present invention, according to some embodiments, with DRL component  300  isolated within headlamp chamber  350 , which preferably has a multi-faceted, reflective inner back wall as shown. The device comprises a 4″×6″ rectangular integrated dual beam head light. In various embodiments, the device includes one of more of the following features: Five (5) LEDs, Auto Select 12/24 VDC Dual Voltage, Polycarbonate Lens with Hard Coating Shell, Standard 3 Blade OEM Connector.  FIG. 3B  shows a top view of the device of  FIG. 3A , showing headlamp lens  360  and headlamp outer shell  370 , as well as power cord  380 . Shell  370  comprises a light, strong, and/or economical material, such as, but not limited to, aluminum. Dimensions of the device shown are approximately 6.6″×4.2″×3.6″. In some embodiments, the Low Beam LEDs comprise one LUXEON® MZ (an undomed multi-die LED, http://www.lumileds.com/uploads/447/DS136-pdf, as shown, e.g., at  FIG. 1B  numeral  140 ) and the DRL LEDs comprise four LUXEON® Z LEDs. The Low Beam LEDs are selected and configured to output a light pattern to meet U.S. Department of Transportation Low Beam Requirements and the DRL LEDs are selected and configured to output a light pattern to meet U.S. Department of Transportation DRL Requirements. Different numbers, arrangements, and types of LEDs may be used for each lighting function, which also meet these requirements. For example, in some embodiments, the DRL LEDs can comprise one LUXEON® MZ LED. 
         [0030]    In some embodiments, Low Beam/DRL headlamp  390  is part of a four lamp system comprising two Low Beam/DRL headlamps and two High Beam headlamps. In some embodiments, the Low Beam/DRL headlamps have power connectors comprising three contacts, a Low Beam contact, a High Beam contact, and a Ground. In some embodiments, the three contacts comprise three pins/blades. In some embodiments, each Low Beam/DRL headlamp has a three-pin connector having a Low Beam pin, a High Beam pin, and a Ground. If a PWM Signal is input on the Low Beam pin then the DRL Beam is energized within the headlamp. If either the Low Beam pin or the High Beam pin have a steady state voltage then the Low Beam is energized within the headlamp. 
         [0031]    When started, vehicles equipped with the four lamp system described above output a PWM signal to the two Low Beam/DRL headlamps&#39; Low Beam pins. When the vehicle operator switches on the Low Beam via a first vehicle switch then the vehicle applies a steady state voltage to the two Low Beam/DRL headlamps&#39; Low Beam pins. When the vehicle operator switches on the High Beam via a second vehicle switch then the vehicle applies a steady state voltage to the two Low Beam/DRL headlamps&#39; High Beam pins. Additionally, when the vehicle operator switches to High Beam the two High Beam headlamps are also energized with a steady state voltage. 
         [0032]      FIG. 4  shows a block diagram of the Low Beam/DRL headlamp circuit according to some embodiments, including High Beam contact  402 , Low Beam contact  404 , PWM Detection circuit  406 , DRL LED Driver and Application circuit  410 , DRL LEDs  416 , NOT gate  412 , Low Beam LED Driver and Application circuit  408 , and Low Beam LEDs  414 . 
         [0033]    PWM Detection and Switching Overview: This circuit either detects a steady state voltage to control the Low Beam LEDs or a PWM input to drive the DRL LEDs. The DRL Detection takes advantage of the PWM signal comprising many AC signals at different frequencies and amplitudes added together to form the PWM Square Wave signal DRL Voltage input. This results in an immediate detection of the rising edge of the PWM DRL Voltage input. 
         [0034]      FIGS. 5A and 5B  show a schematic diagram of the Low Beam/DRL headlamp circuit, according to some embodiments, with circuit blocks indicated, including PWM Detection circuit  506 , Switching  512 , Low Beam LED Driver and Application circuit  508 , Low Beam LED  514 , DRL LED Driver and Application circuit  510 , and DRL Beam LEDs  516 . PWM Detection and Switching of the Low Beam/DRL headlamp is described in further detail below, with reference to  FIGS. 5A and 5B . 
         [0035]    DC Input Voltage: R 22  and R 23  form a voltage divider that outputs 93.6% of the Low Beam Input Voltage to the AC Coupling Capacitor C 20 . C 20  operates as an AC Coupling Capacitor that blocks DC Voltage. Once the DC Voltage is blocked, the capacitors C 21  and C 22 , if charged, will be discharged by R 24  and R 25  and the transistors base resistors R 26  and R 39 . A full discharge of these capacitors will occur in 0.1 seconds or less. Thus, the maximum delay from the time a vehicle driver switches the DRL to Low Beam switch to the time of the actual switch over is less than one tenth of a second. With zero current from the base to emitter at the Bipolar Junction Transistor Q 5 , it will open the circuit from the resistor R 27  to ground. Consequently, with no current flowing from R 27  to ground, the PNP transistor Q 6  will open the connection from the internal power supply voltage VDD to the PWM Dimming Pin of IC 2 . A grounded PWM pin of IC 2  represents a duty cycle of 0% making the LED Driver IC 2  dim the output to 0% or off. Additionally, the cease of current at the resistor R 39  causes Q 8  to turn off to allow the V-IN input Voltage to be divided by R 3  and R 4  to then cause a constant Voltage to the LED Driver IC 1  Dimming input which is equivalent to 100% Duty Cycle which causes full brightness output to the Low Beam LEDs. 
         [0036]    PWM Input Voltage: R 22  and R 23  form a voltage divider that outputs 93.6% of the Low Beam Input Voltage to the AC Coupling Capacitor C 20 . C 20  operates as an AC Coupling Capacitor that passes the PWM Voltage signal while removing any DC offset. Additionally, the capacitor C 20  together with the diode D 8  work together to create a DC bias shift on the output. During the negative part of the cycle the diode D 8  will conduct and charge the capacitor C 2 . During the positive part of the cycle the diode D 8  is reversed biased and the output is therefore V(C 20 )+Vin. At high frequency, the DC offset V(C 20 ) is approximately Vin minus the forward bias Voltage of diode D 8 . Diode D 9  works in conjunction with diode D 8  by eliminating any negative value caused by the forward bias Voltage of diode D 8 . Additionally, C 20  functions with R 24  and R 25  to form an RC High Pass Filter. 
         [0037]    Using the RC High Pass Filter Equation f(cut-off) puts the cutoff frequency to be 14 Hz for the example shown. With the voltage rectification caused by capacitors C 21 , C 22  and the Zener diode ZD 2 , this results in a positive DC Voltage equal to the ZD 2  Zener diode clamping voltage of 5.6 V in the example regardless of the 9.5 to 36 Volt range at the input. This voltage meets required Emitter-Base Voltage V(EBO) of the bipolar junction transistors Q 5  and Q 8 . Current flowing at the base of the NPN Transistor Q 5  will turn it on. This grounds the PNP transistor Q 6  base to meet the required Emitter Base Voltage V(EBO) of the PNP transistor Q 6  which cause the emitter input of the PNP transistor Q 6  to be conducted to the collector of the PNP transistor Q 6  to connect the LED Driver IC 2  reference Voltage output to the PWM Dimming pin of the LED Driver IC 2 . The constant Voltage to the LED Driver IC 2  PWM Dimming input is equivalent to a 100% duty cycle which causes a full brightness output to the DRL LEDs. 
         [0038]    Below 100 Hz PWM input the RC High Pass Filter attenuates the signal which propagates through the rest of the circuit. Below the 14-Hz Cutoff Frequency a sharp attenuation occurs reducing the rectified Voltage to near zero Volts which shuts off the DRL Beam and turns on the Low Beam of the Low Beam/DRL headlamp. 
         [0039]    For frequencies above the 14-Hz Stop Band, the circuit operates as follows. C 20  changes the offset voltage of the Low Beam Pin PWM Input Voltage to zero. The diode D 8  then corrects the offset voltage to be Vin minus the forward bias voltage of D 8 . The diode D 9  then compensates for the diode D 8  Forward Bias Voltage drop to raise the harmonic signal voltages above ground. C 21  and C 22  then operate to rectify the signal that is clamped by the Zener Diode ZD 2  to limit the input voltage to Q 5  to the clamping voltage of the Zener diode ZD 2 . R 24  also functions with the Zener Diode ZD 2  to conduct the voltage that is greater than the ZD 2  clamping voltage. When the rectified input voltage at C 21  is greater than the Zener Diode ZD 2  clamping voltage the voltage to Q 5  will be constant due to ZD 2 . If the rectified input voltage at C 21  falls below the Zener Diode ZD 2  clamping voltage then R 24  and R 25  form a voltage divider that inputs  91 % of the rectified input voltage at C 21 . 
         [0040]    The system uses the LED Driver Integrated Circuits IC 1  and IC 2  dimming pins as on/off switches. 
         [0041]    Automotive industry headlight PWM Input Voltages are typically well above 14 Hz. If the frequency is below 14 Hz it will in practice be a DC Input Voltage which will operate as already described. This assures that there will not be cases where the Low Beam Pin PWM Input Voltage is of a low enough frequency to falsely trigger Q 5  or Q 8  by being at or near their forward bias Voltages. 
         [0042]    Low Beam and DRL LED Driver and Application Circuit: Once selected by the PWM Detection Output and Switching Circuit the respective LED Driver and Application circuit drives its respective LEDs to either energize the Low Beam or the DRL Beam LEDs. 
         [0043]      FIG. 6  shows a front view of the Low Beam/DRL headlamp of  FIG. 3A , wherein a dynamic input voltage is applied to activate the DRL Beam LED output. DRL LEDs on the front face of the DRL component light up behind the textured lens to provide daytime running light inside the headlamp chamber, directed forward as shown. 
         [0044]      FIG. 7  shows a front view of the Low Beam/DRL headlamp of  FIG. 3A , wherein a steady state input voltage is applied to activate the Low Beam LED output. With reference to  FIG. 1B , low beam LED  140  on the back face of the DRL component is lighted to provide low beam light directed toward the reflective back wall of the headlamp chamber. 
         [0045]    In some embodiments, the DRL component is part of a triple beam headlamp that provides a DRL function, a low beam headlamp function, and a high beam headlamp function. In some embodiments, the triple beam headlamp device comprises a 7″ round or a 5″×7″ rectangular integrated triple beam head light. The 7″ round head light has a 7″ diameter. The 5″×7″ rectangular head light has dimensions of approximately 7.9″×5.6″, in some embodiments. Each device has two sections. The Low Beam mode illuminates one section (Low Beam LEDs on) and the High Beam mode illuminates both sections (Low Beam and High Beam LEDs on). In various embodiments, the triple beam device includes one of more of the following features: Nine (9) LEDs, Auto Select 12/24 VDC Dual Voltage, Polycarbonate Lens with Hard Coating Shell, Standard 3 Blade OEM Connector. The Low Beam LEDs are selected and configured to output a light pattern to meet U.S. Department of Transportation Low Beam Requirements, the High Beam LEDs are selected and configured to output a light pattern to meet U.S. Department of Transportation High Beam Requirements, and the DRL LEDs are selected and configured to output a light pattern to meet U.S. Department of Transportation DRL Requirements. Different numbers, arrangements, and types of LEDs may be used for each lighting function, which meet these requirements. 
         [0046]    In some embodiments, the triple beam headlamp is part of a two lamp system comprising two triple beam headlamps. In some embodiments, the triple beam headlamps have power connectors comprising three contacts, a Low Beam contact, a High Beam contact, and a Ground. In some embodiments, the three contacts comprise three pins/blades. In some embodiments, each triple beam headlamp has a three-pin connector having a Low Beam pin, a High Beam pin, and a Ground. If a PWM Signal is input on the Low Beam pin then the DRL Beam is energized within the headlamp. If the Low Beam has a steady state voltage the Low Beam is energized within the headlamp. If the High Beam has a steady state voltage the Low Beam and the High Beam are energized within the headlamp. 
         [0047]    When started, vehicles equipped with the two lamp system described above output a PWM signal to the two triple beam headlamps&#39; Low Beam pins. When the vehicle operator switches on the Low Beam via a first vehicle switch then the vehicle applies a steady state voltage to the two triple beam headlamps&#39; Low Beam pins. When the vehicle operator switches on the High Beam via a second vehicle switch then the vehicle applies a steady state voltage to the two triple beam headlamps&#39; High Beam pins. 
         [0048]    While there have been shown and described fundamental novel features of the invention as applied to the preferred and exemplary embodiments thereof, it will be understood that omissions and substitutions and changes in the form and details of the disclosed invention may be made by those skilled in the art without departing from the spirit of the invention. Moreover, as is readily apparent, numerous modifications and changes may readily occur to those skilled in the art. Hence, it is not desired to limit the invention to the exact construction and operation shown and described and, accordingly, all suitable modification equivalents may be resorted to falling within the scope of the invention as claimed. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.