Multiregulator circuit and lamp

[0002] This invention relates to circuits for operation over a range of voltages, more particularly for a vehicle lamp circuit that provides lighting over a range of voltages.

[0003] Other aspects, objects, and advantages of the present invention appear more clearly on reading the following best mode for carrying out the invention, given by way of example and made with reference to the accompanying drawings, in which:

[0004] FIG. 1 shows a schematic of the circuit to operate a marker lamp over a range of voltages.

[0005] FIG. 2 shows a schematic of the circuit with additional components to operate a clearance, stop/tail lamp.

[0006] FIG. 3 shows a front view of a lamp with the incorporated circuit.

[0007] For the purpose of promoting an understanding of the present invention, reference will be made to embodiments of a multivoltage circuit, as well as embodiments of a marker and a clearance/tail/stop lamp, as illustrated in the drawings. However, it should be understood that these embodiments are not presented to represent a limitation on the invention. Other vehicle lamps and other electronic components could provide additional embodiments which would fall within the spirit and scope of the invention described herein. Referring now to the drawings in detail, for the ease of the reader, like reference numerals designate identical or similar parts throughout the drawings.

[0008] FIG. 1 illustrates a multiregulator circuit that can operate over a wide range of operating voltages. In particular, the circuit shown in FIG. 1 is an embodiment of a dual regulator circuit that can be used to power a marker lamp for vehicles. As will be discussed in more detail hereinbelow, in this embodiment, the operating voltage of the circuit is approximately 10 to 50 volts.

[0009] As shown in FIG. 1, input voltage is applied to line 6 through diode rectifier 7 to the IN terminal of adjustable three-terminal regulator 8. Adjustable three-terminal regulator 8 is configured as a voltage regulator. Specifically, regulator 8 is connected to two resistors 9 and 10 that act as voltage dividers. As mentioned above, in the embodiment shown here, the input voltage of the circuit is approximately 10 to 50 volts. However, the circuit can operate at higher voltages provided the voltage drop from input to output of the individual adjustable threeterminal regulators does not exceed 40 volts. If necessary, the use of larger or more efficient heat sinks can manage any increased heat generated by higher voltages and larger voltage drops.

[0010] In the embodiment described herein, regulator 8 is regulated at approximately 18 volts by resistors 9 and 10. One of ordinary skill in the art will readily appreciate that regulator 8 can be regulated at a variety of voltages by selecting different values for resistors 9 and 10.

[0011] Thus, the example used herein is not meant to limit the embodiments of the invention to an 18-volt voltage regulator. Adjustable three-terminal regulators, such as an LM317T manufactured by National Semiconductor, can serve as voltage regulator 8 described herein. One of ordinary skill in the art will readily appreciate, however, that, in addition to the LM317T regulator, other types and models of three-terminal adjustable regulators can be used in alternate embodiments of the instant invention. The output from voltage regulator 8 is applied to a second adjustable three-terminal regulator 12, which is configured to be a current regulator. Resistor 13 in series with regulator 12 sets the output current of current regulator 12. In the embodiment shown in FIG. 1, the output of current regulator 12 is then applied to light source 14. Light source 14 can be an incandescent bulb, a single light emitting diode, an array of light emitting diodes or a plurality of light emitting diode arrays.

[0012] In the embodiment disclosed herein, current regulator 12 is set to approximately 50 mA by resistor 13. However, one of ordinary skill in the art will readily appreciate that current regulator 12 can be regulated at a variety of currents by selecting different values for resistor 13. Thus, the example used herein is not meant to limit the embodiments of the invention to a 50-mA current regulator. Adjustable three-terminal regulators, such as an LM317LZ manufactured by National Semiconductor, can serve as current regulator 12 described herein. One of ordinary skill in the art will readily appreciate, however, that, in addition to the LM317LZ regulator, other types and models of three-terminal adjustable regulators can be used in alternate embodiments of the instant invention.

[0013] The dual regulator circuit illustrated in FIG. 1 allows lamps, or other electrical devices, to operate over a wide range of input voltages. In one embodiment, a lamp, such as a vehicle marker lamp, which incorporates the dual regulator circuit of FIG. 1, can operate over an approximate range of 10 to 50 volts. The lamp comprises light source 14, as well as a housing (not shown), a lens cover (not shown), and a circuit board (not shown) comprising input and output lines connecting the lamp to the circuit shown in FIG. 1. In one embodiment of such a lamp, the housing can be removably secured to a vehicle. Moreover, as mentioned above, light source 14 can be an incandescent bulb, a single light emitting diode, an array of light emitting diodes or a plurality of light emitting diode arrays. In an alternate embodiment, potting material (not shown), such as an epoxy, may be used to hold light source 14 and the circuit board in place, as well as to seal the lamp from water and environmental damage.

[0014] At voltages below 20 volts, voltage regulator 8 passes the input voltage through with losses. Provided there is enough voltage to drive light source 14 and current regulator 12, the current through light source 14 will be limited to the amount dictated by the value of resistor 13. At higher voltages, voltage regulator 8 limits the voltage applied to current regulator 12 to the voltage determined by resistors 9 and 10. In some cases a heat sink (not shown) is required for voltage regulator 8. The heat sink can be made of any material capable of adequately dissipating the heat generated at the maximum operating voltage under the most severe operating conditions. In one embodiment, the heat sink is made of zinc. In another embodiment, the heat sink is made of aluminum. In one embodiment, the heat sink is located between the lens cover and the circuit board with the light emitting diode(s) attached to it. When the heat sink is disposed in this way, portions of the heat sink will be cut to define a hole(s) to allow light to pass through. In an alternate embodiment, the heat sink is placed under the circuit board.

[0015] FIG. 2 illustrates another embodiment of a multiregulator circuit with additional components that can operate over a wide range of input voltages. In this embodiment, the multiregulator circuit can be used to power a stop/tail/clearance lamp for vehicles. The circuit shown in FIG. 2 is similar to the circuit in FIG. 1. However, the circuit in FIG. 2 comprises additional circuitry to produce a controlled change in the resistance of an additional circuit, thereby providing a varying current. In the embodiment described herein, the varying current provides the increase or decrease of light intensities that is required for the stop/tail lamp function.

[0016] With respect to the clearance function of a combined stop/tail/clearance lamp, the circuit in FIG. 2 is similar to the circuit in FIG. 1. Specifically, adjustable three-terminal regulator 8 is configured as a voltage regulator, wherein resistors 9 and 10 regulate the output voltage. Then, current passes from voltage regulator 8 through a second adjustable three-terminal regulator 12, which is configured to be a current regulator. Current regulator 12 then supplies a constant current to light source 23. Similar to the circuit illustrated in FIG. 1, the circuit shown in FIG. 2 comprises resistor 13, which sets the current in current regulator 12. The current through light source 23 will be limited to the amount dictated by the value of resistor 13. Changing the value of resistor 13 changes the values set for current regulator 12.

[0017] As with light source 14, light source 23 can be an incandescent bulb, a single light emitting diode, an array of light emitting diodes or a plurality of light emitting diode arrays. For example, in one embodiment, light source 23 is the center light emitting diode array of a vehicular stop/tail/clearance lamp. The center light emitting diode array is composed of a single light emitting diode and performs the clearance lamp function, wherein the clearance function of the lamp utilizes a constant current. In this embodiment, the current requirement for the center light emitting diode is approximately 35 mA to 50 mA, depending on the type of light emitting diode used. One of ordinary skill in the art will readily appreciate that advances in light emitting diode technology may allow lower current requirements that may modify the embodiments described herein while remaining within the scope and spirit of the present invention. In addition, other lamps or electrical devices that operate more efficiently with a constant current can utilize the circuit described hereinabove.

[0018] The multiregulator circuit shown in FIG. 2 also provides power for the stop/tail function of the combined stop/tail/clearance lamp. In the circuit shown in FIG. 2, the tail lamp voltages are applied through diode rectifier 7 and the stop lamp voltages are applied through diode rectifier 15. The tail and stop lamp voltages are combined at the input of voltage regulator 8, so that the circuit becomes active if either a stop lamp or a tail lamp voltage is applied. Current passes from voltage regulator 8 to adjustable three-terminal regulator 18. Adjustable three-terminal regulator 18 is configured as a second current regulator to supply current to light source 22 for the stop/tail function. In one embodiment, the main light emitting diode array for the stop/tail functions of the lamp is composed of two series strings of three light emitting diodes. It should be understood, however, that changes in the configuration of the light emitting diode array, such as the use of a single light emitting diode, to produce stop/tail lamp functions are within the scope and spirit of this invention.

[0019] Diode rectifier 16 applies voltage to a transistor switch 17, such as a general purpose NPN transistor manufactured by numerous manufacturers, including National Semiconductor. Transistor switch 17 has a collector connected to the gate of P-channel MOSFET 19. In the embodiment shown here, MOSFET 19 is used to remove or add resistor 20 to the circuit by sensing voltage levels. A logic level version of MOSFET 19 can be used to assure that MOSFET 19 will turn on and off at the lower voltages, particularly voltages in a range of approximately 4 to 10 volts.

[0020] When transistor switch 17 is activated, MOSFET 19 is turned on, which shunts resistor 20 effectively removing it from the circuit. With resistor 20 removed from the current path, more current will travel to light source 22. When the circuit in FIG. 2 is used in a vehicular stop/tail lamp, engaging the stop lamp voltage turns activates transistor switch 17, which then turns on MOSFET 19. The increased amperage that results when MOSFET 19 shunts current around resistor 20 will cause the stop/tail lamp to shine more brightly for the stop lamp function.

[0021] Removing the stop lamp voltage turns off transistor switch 17, which allows the gate of MOSFET 19 to go high, thereby turning it off. When MOSFET 19 is turned off, the previously shunted resistor 20 is effectively added to the circuit. When both resistors 20 and 21 are utilized in series, the added resistance reduces the current to produce dimmer tail lamp illumination.

[0022] MOSFETs identical to or similar to part no. IRF-7204 manufactured by International Rectifier can serve as MOSFET 19 described in this embodiment of the instant invention. However, one skilled in the art will readily appreciate that other MOSFETs manufactured by other manufacturers could be used. Moreover, it should be understood that the use of MOSFET 19 is intended as an example only and other electrical components that perform substantially the same function could be used.

[0023] It should be recognized that the instant invention is not limited to the embodiments shown in FIGS. 1 and 2. Additional adjustable three-terminal regulators, each combined with appropriate resistors, may be added in series to the circuits shown in FIGS. 1 and 2 to reduce voltage input in a step down process. The additional adjustable three-terminal regulators may be configured as either voltage regulators or current regulators.

[0024] FIG. 3 shows the circuit of FIG. 2 on circuit board 24 for a vehicle lamp. One of ordinary skill in the art will readily appreciate that the simplicity of the multiregulator circuit disclosed herein allows for a slim design for a vehicular marker or stop/tail/clearance lamp or other lamp.

[0025] Although, for convenience, embodiments of the present invention have been described herein, it will be apparent to those skilled in the art that many variations of this invention can be made without departing from the spirit of the invention as claimed.