Compact A.C. powered LED light fixture

A compact LED light fixture includes an LED circuit board whose top surface mounts one or more LED's and an A.C. LED Driver circuit. An input circuit board is mounted on an underside of the mounting platform. Unconditioned A.C. power from electrical cables positioned in a wire way is conducted by an electrical connector to the top surface the LED circuit board, then across and down through the top surface of the LED circuit board to the input circuit board where the A.C. power is conditioned and then conducted back through the LED circuit board to the A.C. LED driver.

FIELD

The subject disclosure relates to LED electric lighting fixtures, and more particularly to compact A.C. powered LED electric lighting fixtures.

DESCRIPTION OF RELATED ART

Various LED electric light fixtures have been constructed in the past, for example, such as those disclosed in U.S. Pat. Nos. 7,726,840 and 8,864,347, both assigned to Tempo Industries, LLC.

SUMMARY

According to an illustrative embodiment, a compact LED light fixture comprises a wireway having first and second sides and a bottom surface defining a longitudinally extending channel for receiving at least first and second electrical cables. A longitudinally extending circuit board mounting platform is mounted to the wireway. The circuit board mounting platform carries an LED circuit board carrying one or more LEDs and an A.C. LED Driver circuit. An input circuit board is located in the wireway beneath the circuit board mounting platform and includes circuitry configured to receive an unconditioned A.C. line signal and to supply a conditioned A.C. line signal to the A.C. LED driver circuitry on the first circuit board. In an illustrative embodiment, an electrical connector transfers unconditioned A.C. power from the first and second electrical cables in the wireway to first and second electrically conductive power pins which extend through the LED circuit board. The unconditioned A.C. power is then conducted across the LED circuit board by electrical conductor traces formed thereon and then down through the LED circuit board to input terminals of the input circuit board.

The illustrative embodiments result in a light fixture having a much lower profile than other constructions, e.g. ¾″ high instead of 1½″ high. Additionally, the location of the input circuit board may be changed, for example, to allow for mounting optics and to also facilitate ease of replacement of the board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An illustrative embodiment of a compact A.C. powered LED light fixture11is illustrated inFIG. 1. The fixture11includes a wireway13, an electrical connector15, electrical cables or leads16,18, an input circuit board17, an LED circuit board mounting platform21, and an LED circuit board23. In one embodiment, the wireway13may be an aluminum extrusion, while the mounting platform21may be a metal casting formed of, for example 380 alloy aluminum. In one embodiment, a screw19attaches the input circuit board17to the underside of the LED mounting platform21. In one embodiment, heights H1and H2may be 0.33 and 0.80 inches, respectively.

The LED circuit board23mounts one or more LEDs or LED modules, e.g.24on a top surface31thereof, and has a pair of power pins25,27, which depend from an undersurface of the circuit board23, and which further pass through the board23and appear on its top surface311. The pair of pins25,27is positioned to pass through a hole or aperture35in the circuit board mounting platform21and to electrically connect with the electrical connector15and with a pair of conductor traces on the LED carrying circuit board23, as described in further detail hereafter. In various embodiments, a suitable lens component or components may be configured to cover the LEDs24.

As seen inFIG. 2, the input circuit board17carries circuitry which receives A.C. power, e.g. 120 volts A.C., at input terminals41,42and provides conditioned power at output terminals43,44to A.C. LED Driver circuitry50located on the LED circuit board23in order to illuminate the LEDs24.

Power flow in an illustrative embodiment is illustrated schematically inFIG. 2. Unconditioned A.C. input power (e.g. a line voltage of 120 volts A.C.) is transferred by the electrical connector15from cables or leads16,18to the electrical pins25,27, as indicated schematically by a first vertical dashed line29. This unconditioned A.C. power is then conducted across the LED circuit board23by a pair of electrical conductor traces illustrated schematically by a horizontal dashed line30on the top surface311of the circuit board23to an electrical connector37. In one embodiment, pins41a,42a,43a, and44aof the electrical connector37are soldered to the LED circuit board23, thereby attaching the connector37to the circuit board23. Power is conducted from the LED circuit board23via pins41a,42a, to a mating connector39mounted on the input circuit board17, as illustrated by a second vertical dashed line31. As mentioned above and described in further detail below, the input circuit board17conditions the unconditioned A.C. power and supplies a conditioned A.C. power signal to the A.C. LED Driver circuitry50through the combination of connectors37and39and pins43a,44a, as indicated by a third vertical dashed line34.

FIG. 4illustrates how the circuit board mounting platform21and the wire way13mate and attach together according to an illustrative embodiment. As illustrated inFIG. 4, the wireway13has respective vertical side surfaces59,61, which turn inwardly at their upper ends to respectively form a pivot point63and a horizontal support surface65. The left side of the circuit board mounting platform21has a groove56formed therein at pivot point63to facilitate attachment of the mounting platform21to the wire way13. A horizontally extending surface67is formed at the right side of the mounting platform21and rests on the support surface65. In one embodiment, the groove56on the left edge of the mounting platform21is mated at an angle with the pivot point63and then rotated downwardly to establish an interlocking relationship or engagement between the mounting platform21and the wireway13. At this point, the respective mounting screws53are inserted at opposite ends of the mounting platform21and bite into the inner side of the wireway13to firmly hold the assembly together.

FIG. 4further illustrates electronic components54,55,57mounted to the input circuit board17and an internally threaded boss20, which is formed on the underside of the mounting platform21and into which the mounting screw19is threaded. In one embodiment, the circuit board mounting platform21has a generally rectangular depression or channel41shaped to receive the LED circuit board23.

FIGS. 5 and 6further illustrate one embodiment of the electrical connector15, which includes a bottom receptacle holder115, and a snap-in female receptacle holder117. The bottom receptacle holder115works in cooperation with the snap-in female receptacle holder117to insert and hold two female electrically conductive insulation piercing pins120that respectively pierce electrical cables16,18. The two connector components contain a mating internal conductor structure having a pair of openings126which electrically connect with respective mating pins25,27.

In assembly of the fixture, the pins25,27shown inFIG. 2are soldered or otherwise attached to the LED circuit board23, which is then attached to the circuit board mounting platform21by heat transmissive double-sided tape or other attachment mechanism such that the pins25,27protrude from the bottom of the mounting platform. The pins41a,42a,43a,44aof the connector37are then inserted through the mounting platform21and through suitable openings in the circuit board23and soldered to the circuit board23. The connector39is soldered in place on the input circuit board17and mated with the connector37, whereafter the input circuit board is attached to the outside bottom surface of the mounting platform21by the mounting screw19. The connector15may thereafter be mated with the pins25,27, and the wire way13may then be attached to the mounting platform21using screws53as described above.

The illustrative embodiments result in a light fixture having a much lower profile than other constructions, e.g. having an overall height H3of ¾″ high (FIG. 3), instead of, for example, 1½″ high. Additionally, the location of the input circuit board17may be changed, for example, to allow for mounting optics and to also allow ease of replacement of the circuit board17. In illustrative embodiments, the reduced profile is achieved in part by the longitudinal separation of connection functions by allocation of selected connector functions to connectors15and pins2527and to connectors37,39along with the layout of conductor paths to facilitate that separation.

An illustrative embodiment of the input circuitry mounted on the input circuit board17is shown inFIG. 7. As shown, the unconditioned A.C. input on input lines41,42is connected to pins2and3of a diode bridge BR1. The input circuitry further includes a bidirectional Transorb Diode (TVS) D17connected across pins1and4and a MOV (metal oxide varistor), RV1, connected across pins2and3of the diode bridge BR1. A fuse F1is also provided in one of the input signal lines.

With respect to operation of the circuit of FIG. [4]7, the A.C. LED driver51(FIG. 9) requires protection against external high voltage spikes and current surges. The input current is limited by the fuse F1, which in one embodiment may be rated for 1 Amp at 250 VAC. Right after the fuse F1, any transient voltage spikes are clamped by the MOV, RV1.

The input A.C. voltage is rectified by the Diode Bridge, BR1to 120 Hertz from 60 Hertz. In one illustrative embodiment, the peak voltages are clipped/reduced by the Diode Bridge BR1to about 86 Vpeak from 115 Vpeak. In such an embodiment, the input voltages can fluctuate between 110 to 120 Vrms. An illustrative rectified input voltage Vin is illustrated inFIG. 8.

The bidirectional Transorb Diode (TVS) D17provides a secondary voltage clamp in case some voltage spikes get through the MOV, RV1. Once the input voltage passes the input circuit, the voltage across terminals101,103(FIG. 9) is about 100 VDC, 72 mA, 7.20 Watts in one embodiment.

FIG. 9shows illustrative circuitry50located on the LED circuit board23for controlling the light output of a number of LEDs designated D1, D2, D3. . . D16. In the circuit ofFIG. 9, the positive input voltage Vin is supplied to a first terminal of resistors R1, R2, and to the anodes of LEDs D1, D2, D3, D4. The negative input at terminal103is connected to an input CS of the A.C. LED Driver51and through a first terminal of a resistor R4to a ground terminal GND of the A.C. LED Driver51. The second terminal of the resistor R3is also connected to a second terminal of the resistor R1and to an RHOLD terminal of the Driver51. Respective terminals TP2, TP5, have a capacitor C1connected thereacross and connected to RHOLD and GND, respectively. In one embodiment, the A.C. LED Driver51may be a Magna Chip part no. MAP9002 available from MagnaChip Semiconductor Ltd., 891, Daechi-Dong, Kangnam-Gu, Seoul, 135-738 Korea.

The circuitry ofFIG. 9functions as follows: the AC driver51from MagnaChip is based on the principle of driving LEDs by turning on different groups or stages of LEDs using a stepping up and stepping down voltage from zero to 120 VAC or 220 VAC, as illustrated inFIG. 10. For illustrative 120 Vrms systems, the number of LEDs depends on the stack up of the LED's forward voltages. In one embodiment, it is desirable that the stacked forward voltages come as close to the 120 Vpeak as possible. In one embodiment of the illustrative circuit ofFIG. 9, Nichia 24 Volt LEDs are used in series and parallel.FIG. 9illustrates four LEDs in series (D1, D5, D9& D13) and LEDs connected in parallel with each of those LEDs D1, D5, D9, D13. The LEDs in parallel are used to control the currents flowing through each LED. As the numbers of LEDs are added or removed in parallel, the amount of current distributed into the LED is reduced or increased proportionally. Hence, the light output for the LEDs in each stage can be adjusted.

In the illustrative circuit ofFIG. 9, there are three stages. The first stage of LEDs (D1, D2, D3, D4, D5, D6, D7, & D8) turns on first. Potential flickering of the light output for this stage can be controlled by using a dimmer with low end trimming. For example, a Lutron MAELV-600P can be used to cause the LEDs to stay on when power is initially applied. The second stage to turn on is D9, D10, D11, and D12. LEDs D13, D14, D15, D16are in the last stage to turn on. Once turned on, each stage remains on until the voltage level falls below the turn-on voltage for the particular stage. As illustrated inFIG. 10, the corresponding peak voltages for each stage in the illustrative embodiment are respectively, 60, 80 and 100 volts.

In illustrative embodiments of the circuit ofFIG. 9, the voltages across the LEDs are about 73 VDC (without using a dimmer) and 61 VDC with a dimmer, and the LEDs are operating at a total wattage of about 5.18 Watt. The power across the LEDs will be less when using a dimmer since all dimmers have some loss. In various embodiments, the LEDs will see different power levels depending on the dimmer.

The Map9002 driver51has the capability to monitor when the input signal reaches the zero crossing points and to compensate for the loss of signal to keep the LEDs from flickering or blinking. The zero crossings are detected by the RHOLD pin.

The MAP9002 driver51is recommended to operate at 8 Watts. In the illustrative circuit ofFIG. 9, R4is the power setting resistor, and at 13 Ohms, the power across the LEDs is about 5.18 Watt at 72% efficiency. The driver chip has a small metal plate on the bottom for heat sinking.