Low loss input channel detection device for a direct current powered lighting system

A device used with a direct current power source for energizing a lamp. The device includes a plurality of input channels selectively connected to the power source for providing current to the lamp. For each input channel, the device includes a corresponding current sensing component connected to the input channel, and a corresponding bypass switch connected in parallel with the current sensing component. Each current sensing component produces a measurable signal as a function of current that is provided by the corresponding input channel. The device includes a controller connected to the current sensing components and the bypass switches. The controller identifies the input channel that is providing current to the lamp as a function of the measurable signals and controls the bypass switches based on the identified input channel. Particularly, the controller operates each bypass switch in a closed mode when the corresponding input channel is the identified channel so that current provided by the corresponding identified input channel bypasses the current sensing component.

BACKGROUND

The invention relates generally to an input channel detection device for use with a lighting system. More particularly, the invention relates to a detection device for use with a headlamp system of a motor vehicle.

Current headlamp systems include a battery (broadly, power source), an input selection switch for allowing a user to select between the high beam and low beam operation modes, a high beam input channel, a low beam input channel, and one or more headlamps (e.g., a driver side headlamp and a passenger side headlamp). Each headlamp has a low beam lamp element and a high beam lamp element. When the user selects the high beam operation mode via the input selection switch, the high beam input channel is connected to the battery to provide current to the headlamps for energizing the high beam lamp element. Similarly, when the user selects the low beam operation mode via the input selection switch, the low beam input channel is connected to the battery to provide current to the headlamps for energizing the low beam lamp element.

When an electronic power regulation module is used with the current headlamp system, a detection device must be used in order to detect which input channel is supplying power so that the headlamps may be operated in the appropriate high beam or low beam mode. For example, an OR′ing diode or a resistor may be inserted into each input channel. The voltage on the power supply side of each diode or resistor may be monitored to determine which line is supplying the power. However, the addition of the detection component results in significant power loss.

SUMMARY

Embodiments of the invention improve the efficiency of multi-input lighting systems by minimizing the voltage drop and power loss which has been associated with detecting an input power supply channel that is selected for energizing a light source. Additionally, an embodiment of the invention provides a detection device having reverse polarity protection and overvoltage protection for components of the detection device.

DESCRIPTION

Embodiments of the invention include a device (hereinafter referred to as the “detection device”) for use with a lighting system, such as a headlamp system of a motor vehicle, for detecting a power supply channel (broadly, “input channel”) that is selected for energizing a light source (hereinafter referred to as “lamp”). The detection device is configured to minimize voltage drop and power loss which may result from detecting the power supply channel. Additionally, an embodiment of the detection device provides reverse polarity protection and overvoltage protection for components of the detection device.

Referring toFIGS. 1,2, and3, detection devices are used with a lighting system having a direct current (DC) power source, an input selection switch, a plurality of input channels (channel1. . . channel N) and a lamp. The input selection switch may have a user interface for allowing a user to select the input channel. The input selection switch connects the power source to a selected one of the plurality of input channels. The selected input channel provides power to the lamp for energizing the lamp. The lighting system may also include a driver connected between the input channel and the lamp for regulating the power provided to the lamp via the selected input channel.

For example, the lighting system may be a headlamp system of a motor vehicle which may be operated in a high beam mode or a low beam mode. The headlamp system includes a battery (broadly, power source), an input selection switch for allowing a user to select between the high beam and low beam operation modes, a high beam input channel, a low beam input channel, and one or more headlamps (e.g., a driver side headlamp and a passenger side headlamp). Each headlamp has one or more low beam lamp elements (“low beam lamp element”) and one or more high beam lamp elements (“high beam lamp element”). For example, each of the headlamps may be one or more light emitting diodes (LEDs) or high-intensity discharge lamps. When the user selects the high beam operation mode via the input selection switch, the high beam input channel is connected to the battery to provide current to the headlamps for energizing the high beam lamp element. Similarly, when the user selects the low beam operation mode via the input selection switch, the low beam input channel is connected to the battery to provide current to the headlamps for energizing the low beam lamp element.

FIG. 1illustrates an exemplary detection device100used with a lighting system to energize a lamp according to an embodiment of the invention. For convenience, the detection device100is illustrated and described herein as including a first input channel (illustrated as channel1) and a second input channel (illustrated as channel N). However, the detection device100may include more than two input channels and is not limited to having a particular number of input channels. The first and second input channels are mutually exclusively connected by the line selection switch104to the power source102for providing current to the lamp108for energizing the lamp108. In particular, the first input channel is selectively connected to the power source102for providing current to the lamp108for operating the lamp108in a first operating mode or the second input channel is selectively connected to the power source102for providing current to the lamp108for operating the lamp108in a second operating mode. In one embodiment, the input selection switch104of the lighting system may be additionally configured for selectively disconnecting both input channels from the power source102so that no current is provided to the lamp108and the lamp108operates in an “off” mode.

A current sensing component110is connected to at least one of the input channels, such as the second input channel, between the power source102and the lamp108for producing a measurable signal indicative of (i.e., a function of) the current provided to lamp driver106by the second input channel. In one embodiment, the current sensing component110is a diode and the measurable signal is a voltage signal measured on the power source102side of the diode. As explained in detail below, the measurable signal is used to determine (e.g., identify, detect) which of the input channels (e.g., the first input channel, second input channel) is providing current to the lamp108so that the lamp108can be operated in the appropriate (e.g., selected) operating mode. It is to be understood that additional or alternative current sensing components (e.g., resistor, transformer) and corresponding measurable signals may be used for detecting the input channel.

In the illustrated embodiment, a bypass switch112is connected to the second input channel in parallel with the current sensing component110. In one embodiment, the bypass switch112is a p-type metal-oxide-semiconductor field-effect transistor (MOSFET). The current sensing component110may be an intrinsic body diode of the MOSFET. In another embodiment, other types of transistors or switches known in the art may be used. The bypass switch112has a closed mode in which it is closed circuited and conducts and an open mode in which it is open circuited and does not conduct. The bypass switch112operates in the open mode when the second input channel is not determined to be providing current to the lamp108. The bypass switch112operates in the closed mode when the second input channel is determined to be providing the current to the lamp108. In the closed mode, the bypass switch112conducts the current provided by the second input channel so that the current bypasses the current sensing component110and is delivered to the lamp108. By bypassing the current sensing component110in the closed mode, the bypass switch112reduces the voltage drop and the power dissipated in delivering power from the power source102to the lamp108via the second input channel. In the open mode, the bypass switch112does not conduct the current provided by the second input channel so that no current is delivered to the driver and the lamp108via the current sensing component110.

A controller114(e.g., microcontroller114, microprocessor, programmable logic controller114) is connected via a controller114input to the power source102side of the current sensing component110for monitoring/receiving the measurable signal produced as a function of current being provided by the second input channel and the current sensing component110. For example, the measurable signal having a value at or near 0 Volts (or other pre-determined voltage which is less than the voltage as supplied from the power source) measured at the indicates that no current is flowing in the second input channel and thus the second input channel is not providing current to the lamp108. Accordingly, when the measurable signal has a value of 0 Volts, the controller114identifies that the first input channel may be providing current to the lamp108. The measurable signal having a pre-determined value greater than zero indicates that current is flowing in the second input channel and thus the second input channel is providing current to the lamp108. Accordingly, when the measurable signal has a value in a particular range of the pre-determined value, the controller114identifies that the second input channel is providing current to the lamp108.

The controller114is connected via a controller output to the bypass switch112for controlling the mode of the bypass switch112based on the identified input channel. In particular, the controller114provides a switch control signal to the bypass switch112via the controller114output which controls the mode of the bypass switch112. In one embodiment, the controller114is configured to maintain the bypass switch112in the open mode unless the controller114determines that the second input channel is providing current to the lamp108. Thus, the controller114monitors the measurable signal and provides a switch control signal to the bypass switch112for maintaining the bypass switch112in the open mode until the measurable signal indicates that the second input channel is providing current to the lamp108(e.g., the value of the measurable signal changes from 0 V to the predetermined value) upon which the controller114provides a switch control signal to the bypass switch112to operate the bypass switch112in the closed mode.

In one embodiment, the controller is configured to periodically reassess the identified input channel. In particular, after the bypass switch112has been operating in the closed mode for a defined period of time, the controller briefly opens the bypass switch112(i.e., operates the bypass switch in the open mode) to determine whether the second channel is still providing current to the lamp108. The measurable signal is monitored during the brief open mode operation. When the value of the measurable signal drops to 0 V, the controller114determines that the second input channel is no longer providing current to the lamp108and provides a signal to operate the bypass switch112in the open mode.

In one embodiment, the controller114is also connected via another controller114output to the lamp108for controlling the operating mode of the lamp108when the lamp108is receiving current via an input channel. In one example, the first and second channels are connected to anode of lamp108via the driver for providing the current needed to operate the lamp108in the first or second operating mode, respectively. The controller114provides a lamp108control signal to the lamp108to indicate (i.e., control, select) the operating mode of the lamp108based on the input channel that was identified by the controller114as providing the current. For example, the lamp108may include first set of one or more components (e.g., lamp108element(s) of a lamp108, one or more lamp108s, a current limiter) that are activated for operating in the first operating mode and a second set of components (which may include one or more elements from the first set of components) that are activated for operating in a second mode. The controller114provides a lamp108control signal to the lamp108to control which set of components is to receive the current based on the input channel identified as providing the current. If neither input channel is actually providing current to the lamp108(e.g., “off” operating mode), the lamp108will not be energized regardless of the lamp108control signal since the lamp108control signal does not provide power for energizing the lamp108. For instance, if the controller114identifies the first input channel as providing current to the lamp108because the measurable signal value is 0V, and indicates that the operating mode is the first operating mode via the control signal, the lamp108still operates in the appropriate operating mode (“off operating mode) since the lamp108does not receive current for energizing the lamp108.

In one embodiment, the detection device100may include a control switch (not illustrated), such as a transistor, connected between the controller114output and the bypass switch112for adjusting the control signal for operating the bypass switch112. For example, the controller114may be configured to generate a control signal having a low current or voltage value when the controller114determines that the bypass switch112should be operated in the open mode and to generate a control signal having a high current or voltage value when the controller114determines that the bypass switch112should be operated in the closed mode. The control switch operates in an open mode when it receives the control signal having the low value and operates in a closed mode when it receives the control signal having the high value. Accordingly, the control switch modifies the control signal to have a value of zero when the controller114determines that the bypass switch112should be operated in the open mode since the control switch does not conduct the control signal.

In one embodiment, the detection device100may include an over voltage component (not illustrated) for regulating high voltage signals (broadly “electrical signals”) from being received by the bypass switch112. For example, the detection device100may include a diode (e.g., Zener diode) connected across the bypass switch112from the controller114side of the bypass switch112to the driver106side of the bypass switch112. The diode protects the bypass switch112from receiving potentially damaging high voltage signals which may be generated between the controller114and the switch.

In one embodiment, the first input line may be used for providing power to the lamp for energizing the lamp in a plurality of operating modes. The second input line may be used for controlling the lamp to operate according to one of the plurality of operation modes of the lamp.

FIG. 2illustrates an exemplary detection device200used with a lighting system to energize a lamp108according to another embodiment of the invention. The first and second input channels are selectively connected by the input selection switch104to the power source102for providing current to the lamp108for energizing the lamp108. In particular, the first input channel is connected to the power source102for providing current to the lamp108for operating the lamp108in a first operating mode and the second input channel is connected to the power source102for providing current to the lamp108for operating the lamp108in a second operating mode.

A first current sensing component202is connected to the first input channel between the power source102and the lamp108for producing a first measurable signal as a function of the current provided by the first input channel. A second current sensing component204is connected to the second input channel between the power source102and the lamp108for producing a second measurable signal as a function of the current provided by the second input channel. In one embodiment, the current sensing component110is a diode and the measurable signal is a voltage signal measured on the power source102side of the diode. As explained in detail below, the measurable signal is used to determine (e.g., identify, detect) which of the input channels (e.g., the first input channel, second input channel) is providing current to the lamp108so that the lamp108can be operated in the appropriate (e.g., selected) operating mode. It is to be understood that additional or alternative current sensing components (e.g., resistor, transformer) and corresponding measurable signals may be used for detecting the input channel.

In the illustrated embodiment, a first bypass switch206is connected to the first input channel in parallel with the first current sensing component202. Similarly, a second bypass switch208is connected to the second input channel in parallel with the second current sensing component204. In one embodiment, the first and second bypass switches206,208are p-type metal-oxide-semiconductor field-effect transistors (MOSFETs). The first and second current sensing components may each be an intrinsic body diode of the corresponding MOSFET. In another embodiment, the first and/or second bypass switch may include another type of transistor or switch known in the art. Each of the bypass switches206,208has an open mode and a closed mode. The first bypass switch206operates in the open mode when the first input channel is not determined to be providing current to the lamp108. Likewise, the second bypass switch208operates in the open mode when the second input channel is not determined to be providing current to the lamp108. The first bypass switch206operates in the closed mode when the first input channel is determined to be providing the current to the lamp108. Likewise, the second bypass switch208operates in the closed mode when the second input channel is determined to be providing the current to the lamp108. In the closed mode, the first and second bypass switches,206and208, conduct current being provided by the respective first or second input channel so that the current bypasses the respective current sensing component202,204and is delivered to the lamp108. By bypassing the current sensing components202,204, the bypass switches reduce the voltage drop and the power dissipated in delivering power from the power source102to the lamp108via the input channels.

A controller210(e.g., microcontroller, microprocessor, programmable logic controller210) is connected via a first controller210input to the power source102side of the first current sensing component202for monitoring/receiving the first measurable signal produced as a function of current being provided by the first input channel and the first current sensing component202. The controller210is also connected via a second controller210input to the power source102side of the second current sensing component204for monitoring/receiving the second measurable signal produced as a function of current being provided by the second input channel and the second current sensing component204. For example, the first or second measurable signal having a value of 0 Volts (or other pre-determined voltage which is less than the voltage as supplied from the power source) indicates that no current is flowing in the respective first or second input channel. Accordingly, when the first measurable signal has a value of 0 Volts, the controller210is configurable to determine that the first input channel is not providing current to the lamp108. Likewise, when the second measurable signal has a value of 0 Volts, the controller210is configurable to determine that the second input channel is not providing current to the lamp108. The first or second measurable signal having a pre-determined value greater than zero indicates that current is flowing in the respective first or second input channel. Accordingly, when the first measurable signal has a value in a particular range of a first pre-determined value, the controller210identifies that the first input channel is providing current to the lamp108. Likewise, when the second measurable signal has a value in a particular range of a second pre-determined value, the controller210identifies that the second input channel is providing current to the lamp108.

The controller210is connected via a controller210output to the bypass switches for controlling the modes of the bypass switches based on the identified input channel. According to the illustrated detection device200, the controller210is connected via first and second controller210outputs to the first and second bypass switches206,208, respectively. The controller210provides a first switch control signal to the first bypass switch206via the first controller210output for controlling the mode of the first bypass switch206. Likewise, the controller210provides a second switch control signal to the second bypass switch208via the second controller210output for controlling the mode of the second bypass switch208. In one embodiment, the controller210is configured to maintain each of the bypass switches in the open mode unless the controller210determines that the input channel connected to the bypass switch is providing current to the lamp108.

In one embodiment, the first and second input channels are mutually exclusively connected to the power source. Accordingly, the controller210monitors the first and second measurable signals and provides first and second switch control signals, respectively, to the first and second bypass switches206,208for maintaining the bypass switches206,208in the open mode unless the first measurable signal indicates that the first input channel is providing current to the lamp108(e.g., the value of the first measurable signal changes from 0 V to the first predetermined value) or unless the second measurable signal indicates that the second input channel is providing current to the lamp108(e.g., the value of the second measurable signal changes from 0 V to the first predetermined value). Responsive to such an indication by the first measurable signal, the controller210provides a first switch control signal to the first bypass switch206to operate the first bypass switch206in the closed mode. Additionally, the controller210provides a second switch control signal to the second bypass switch208to operate the second bypass switch208in open mode. The first bypass switch206and the second bypass switch208are maintained in the closed mode and open mode, respectively, unless the second measurable signal indicates that the second input channel is providing current to the lamp108. Responsive to such an indication, the controller210provides a first switch control signal to operate the first bypass switch in the open mode and provides a second switch control signal to operate the second bypass switch in the closed mode. The controller210is configured for performing operations for the second input channel and components connected thereto which respectively correspond to the operations described in this paragraph for the first input channel and first input channel components.

In another embodiment, the first and second input channels can be concurrently connected to the power source. Accordingly, the controller210monitors the first measurable signals and provides first switch control signal to the first bypass switch206for maintaining the first bypass switches206in the open mode unless the first measurable signal indicates that the first input channel is providing current to the lamp108(e.g., the value of the first measurable signal changes from 0 V to the first predetermined value). Responsive to such an indication, the controller210operates the first bypass switch206in the closed mode. The controller is configured to periodically reassess the identified input channel. Thus, after the first bypass switch206has been operating in the closed mode for a defined period of time, the controller briefly opens the bypass switch206(i.e., operates the bypass switch in the open mode) to determine whether the first channel is still providing current to the lamp108. The first measurable signal is monitored during the brief open mode operation. When the value of the measurable signal drops to 0 V, the controller114determines that the second input channel is no longer providing current to the lamp108and provides a signal to operate the first bypass switch206in the open mode. The controller210is configured for performing operations for the second input channel and components connected thereto which respectively correspond to the operations described in this paragraph for the first input channel and first input channel components.

Referring to a detection device300illustrated inFIG. 3, in another embodiment, the controller302is connected via a single a controller302output to the first and second bypass switches206,208for controlling the modes of the bypass switches based206,208on the identified input channel. In particular, the controller302provides a single switch control signal via the controller302output for controlling both of the bypass switches206,208. An inverting component304is connected between the controller302and the first bypass switch206for receiving the switch control signal, inverting the switch control signal, and providing the inverted switch control signal to the first bypass switch206. For example, the bypasses switches may be configured so that they operate in the open mode when they receive a low control signal from the controller302and operate in the closed mode when they receive a high control signal. Accordingly, when the controller302identifies that the first input channel is providing current, the controller302generates a switch control signal having a first value (e.g., a low current/voltage value). The inverting component304inverts the switch control signal provided to the first bypass switch206. As such, the first bypass switch206receives a switch control signal having a high value and thereby operates in the closed mode. The second bypass switch208receives the switch control signal having the first value (e.g., low value) and thereby operates in the open mode. Likewise, when the controller302identifies that the second input channel is providing current, the controller302generates a switch control signal having a second value (e.g., a high current/voltage value). The inverting component304inverts the switch control signal provided to the first bypass switch206. As such, the first bypass switch206receives a switch control signal having a low value and thereby operates in the open mode. The second bypass switch208receives the switch control signal having the second value (e.g., high value) and thereby operates in the closed mode.

Referring toFIGS. 2 and 3, in one embodiment, the controller210,302,302is also connected via another controller output(s) to the lamp108for controlling the operating mode of the lamp108when the lamp108is receiving current via an input channel. In one example, the first and second channels are connected to anode of lamp108via the driver106for providing the current needed to operate the lamp108in the first or second operating mode, respectively. The controller210,302provides a lamp108control signal to the lamp108to indicate (i.e., control, select) the operating mode of the lamp108based on the input channel that was identified by the controller210,302as providing the current. For example, the lamp108may include first set of one or more components (e.g., lamp108element(s) of a lamp, one or more lamps, a current limiter) that are activated for operating in the first operating mode and a second set of components (which may include one or more elements from the first set of components) that are activated for operating in a second mode. The controller210,302provides a lamp108control signal to the lamp108to control which set of components is to receive the current based on the input channel identified as providing the current. If neither input channel is actually providing current to the lamp108(e.g., “off” operating mode), the lamp108will not be energized regardless of the lamp108control signal since the lamp108control signal does not provide power for energizing the lamp108. In one embodiment, the controller210,302may additionally indicate that the lamp108is to be operated in the “off mode” when the controller210,302determines that neither of the input channels are providing current based on the first and second measurable signals.

In one embodiment, the detection device200,300may include a first and/or second control switch (shown inFIG. 4andFIG. 5), such as a transistor, connected between the controller output provided for the respective first and/or second bypass switch208for adjusting the control signal for operating the bypass switch. For example, the switch control signal may have a low current or voltage value when the controller210,302determines that the bypass switch should be operated in the open mode and the switch control signal may have a high current or voltage value when the controller210,302determines that the bypass switch should be operated in the closed mode. The control switch operates in an open mode when it receives the control signal having the low value and operates in a closed mode when it receives the control signal having the high value. Accordingly, the control switch modifies the switch control signal to have a value of zero for operating the bypass switch in the open mode since the control switch does not conduct the control signal.

In one embodiment, the detection device200,300may include a first and/or second over voltage component (shown inFIG. 4andFIG. 5) for regulating high voltage signals (broadly “electrical signals”) from being received by the respective first and/or second bypass switch206,208. For example, the detection device200may include a diode (e.g., Zener diode) connected across the bypass switch from the controller side of the bypass switch to the driver106side of the bypass switch. The diode protects the bypass switch from receiving potentially damaging high voltage signals which may be generated between the controller210,302and the switch206,208.

Although the detection devices200,300have been described as having two input channels, it is to be understood that the detection devices200,300may have greater than two input channels and is not limited to having any particular number of input channels. Each additional channel (hereinafter referred to as “a third channel) is selectively connected the power source102for providing current to the lamp108or other output device. For example, the first and second input channels may be used to energize a headlamp of motor vehicle and the third input channel may be used to energize a lamp for a vehicular accessory. In another example, the third input channel may be used for providing power to a vehicular speed control device, a windshield wiper control device, a windshield washer device, a turn signal, or other output device associated with the vehicle.

A third current sensing component is connected to the third input channel between the power source102and the lamp108or output device. The third current sensing component produces a third measurable signal as a function of current provided by the third input channel. A third bypass switch connected to the third input channel in parallel with the third current sensing component. The third bypass switch has an open mode and a closed mode. The third bypass switch has a closed mode for bypassing the third current sensing component and conducting current provided by the third input channel for energizing the lamp or output device.

The controller210,302is connected to the first, second, and third (i.e., additional) current sensing components and the first, second, and third (i.e., additional) bypass switches. The controller210,302identifies the input channel that is providing current as a function of the measurable signals (e.g., first, second, third) and for controlling the mode of the bypass switches based on the identified input channel. In particular, the controller210,302controls each bypass switch to operate in the closed mode when the input channel connected to the bypass switch is the identified channel. The controller210,302controls each bypass switch to maintain the open mode when the input channel connected to the bypass switch is not the identified channel.

As noted above, the detection devices100,200,300may be used with a headlamp system of a motor vehicle for identifying the input channel providing current to a headlamp and operating the headlamp in a corresponding operation mode.FIG. 4is a circuit diagram of a detection device400as illustrated inFIG. 3in an embodiment in which the detection device is used with a headlamp system of a motor vehicle for energizing a high beam element or a low beam element of a headlamp. In particular, a high beam input channel HB and a low beam input channel LB are selectively connected via a line selection switch to a power source for providing current to the headlamp. The detection device identifies whether the high beam input channel HB or the low beam channel LB is supplying current and accordingly energizes a high beam element of the headlamp or a low beam element of the headlamp.

A high beam current sensing component (i.e., diode) is connected to the high beam input channel HB and a low beam current sensing component (i.e., diode) is connected to the low beam input channel LB. A microcontroller is connected to the power source side of the high beam and low beam current sensing components. The microcontroller monitors the voltage, via voltage divider components V1and V2, at the power source side of each of the current sensing components to determine which line is supplying power for the headlamp. Components R15and R16form a 5:1 voltage divider V1for dividing the voltage at the power source side of the high beam current sensing component. Components R25and R26similarly form a 5:1 voltage divider V2for dividing the voltage at the power source side of the low beam current sensing component.

A high beam bypass switch is connected in parallel with the high beam current sensing component (collectively represented as Q1) and a low beam bypass switch is connected in parallel with the low beam current sensing component (collectively represented as Q2). According to the illustrated detection device, Q1and Q2are each a p-type metal-oxide-semiconductor field-effect transistors (broadly “bypass switch”) having a body diode (broadly “current sensing component”). For example, Q1and Q2may be the FDD6637 35V P-Channel Power Trench MOSFETs available from Fairchild Semiconductor Corporation.

When the microcontroller identifies an input channel (i.e., high beam input channel or low beam input channel) that is providing current, the microcontroller provides a switch control signal via a microcontroller output for controlling the operation modes of the high beam and low beam bypass switches. In particular, each bypass switch is operated in the closed mode when the input channel connected to thereto is the identified channel, and each bypass switch is maintained in the open mode when the input channel connected to said bypass switch is not the identified channel. Accordingly, when the high beam input channel is providing current for the headlamp the high beam bypass switch is closed thereby conducting the current so that the current bypasses the high beam current sensing component. Likewise, when the low beam input channel is providing current for the headlamp the low beam bypass switch is closed thereby conducting the current so that the current bypasses the low beam current sensing component. As such, the bypass switches reduce the voltage drop and power loss resulting from passing the current through the current sensing components.

Circuit components D3R2, D6, R2, and Q5(collectively referred to as inverter component I1) are connected between the microcontroller and the low beam bypass switch for inverting the switch control signal before it is received by the low beam bypass switch. Circuit components R12, R13, R14, and Q3(broadly “high beam control switch”) are connected between the microcontroller switch output and the high beam bypass switch and drive the gate of the high beam MOSFET (i.e., bypass switch). The components (R12, R13, R14, and Q3) shift the voltage level of the switch control signal for operating the high beam bypass switch according to the determined operating mode. Circuit components R22, R23, R24, and Q4(broadly “low beam control switch”) are connected between the inverter component I1and drive the gate of the low beam MOSFET (i.e., bypass switch). The components (R22, R23, R24, and Q4) shift the voltage level of the inverted switch control signal for operating the low beam bypass switch according to the determined operating mode. Thus, the inverter component I1and the gate drive circuitry for the high beam and low beam MOSFETs allow a single microcontroller output (via switch control signal) to simultaneously operate both the high beam and low beam bypass switches in opposite modes (e.g., open mode and closed mode).

The gate drive circuitry for the high beam and low beam MOSFETs also provides input reverse polarity protection by causing the high beam and low beam MOSFTETs to open. The high beam and low beam control switches, Q3and Q4, are each a bipolar junction transistor (BJT). For example, the control switches may each be the 2N3904 NPN general purpose amplifier and switch available from Fairchild Semiconductor Corporation.

Additional voltage protection is achieved by the current sensing diodes and diodes D4and D5. The current sensing diodes provide reverse polarity protection by preventing current from flowing toward the power source in each input channel. Diodes D4(e.g., broadly “high beam overvoltage protection component”) and D5(broadly “low beam over voltage protection component”) are connected between the gate and the drain of the high beam and low beam MOSFETs, respectively. In particular, diodes D4and D5are each Zener diodes provide overvoltage protection by preventing the voltage at the gate of the corresponding MOSFET from exceeding 14 V.

FIG. 5is a partial block and circuit diagram of a detection device500as described in connection withFIG. 4and a vehicular headlamp system for use therewith according to an embodiment of the invention. The headlamp system includes a battery (e.g., 12 Volts) and an input line selection switch (not shown). The input line switch connects either the high beam input channel or the low beam input channel to the battery for providing current to the headlamp508. In the illustrated embodiment, the headlamp508is comprised of two sets of light emitting diodes (LEDs). A first set of LEDs includes a first string of LEDs510and a second set of LEDs includes the second string of LEDs512. It is to be understood that the first and second sets of LEDs may include other combinations of the LEDs, including additional strings of LEDs that are not illustrated. For example, the first set of LEDs may include the string of LEDs510and the second set of LEDs may include the first and second strings of LEDs510,512. Additionally, it is to be understood that the LEDs of the first and second sets are not limited to LEDs arranged in one or more strings. For example, the LEDs may be arranged as a chip, a set of chips packed in a package, a grouping of packaged chips, an array of chips or packages, and/or other configurations.

The current from the battery is filtered (e.g., removing noise, electromagnetic interference) via filtering component F1or F2respectively connected to the high beam or low beam input channel. The current is then passed via the input channel through the detection device500and additional filtering components L1, C15, and C41to a driver506. The driver506regulates the current being provided to the LEDs510,512and, specifically, provides constant current to the LEDs510,512. For example, the driver may be a constant current LED driver (e.g., A54201B) available from Osram Sylvania. The constant current from the driver506is provided to the anode of the headlamp508.

As discussed in connection withFIG. 4, the detection device500identifies whether the high beam input channel or the low beam input channel is providing the current for the headlamp508and controls the LEDs510,512accordingly. In particular, the microcontroller has one output for controlling a first string LEDs510and another output for controlling a second string of LEDs512. When the microcontroller identifies that the low beam input channel is providing current for the headlamp508, the microcontroller closes a switch connected to the first string of LEDs510and maintains open a switch connected to the second string of LEDs512in order to energize the first set of LEDs510and thereby operate the headlamp508in low beam operating mode. When the microcontroller identifies that the high beam input channel is providing current for the headlamp508, the microcontroller maintains open the switch connected to the first string of LEDs510and closes the switch connected to the second string of LEDs512in order to energize the second set of LEDs512and thereby operate the headlamp in high beam operating mode.