Abstract:
An energy efficient under-cabinet lighting system with a low profile switch mode power supply complying with Class 2 requirements. This power source is enclosed in a container to provide constant current to an array of light emitting diodes LEDs that are characterized by long life and low power usage. The system is designed to replace existing under-cabinet fluorescent lamp fixtures. A diffuser minimizes pixelization. The unit is also equipped with a safe-charge USB port that can safely charge lithium-ion batteries of accessories like tablets and cellphones with no danger of overheating their batteries.

Description:
This is a continuation-in-part of application Ser. No. 12/284,559 filed Sep. 23, 2008. Application Ser. No. 12/284,559 is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates generally to lighting and more particularly to an energy savings under-cabinet lighting system having a USB port and using Light Emitting Diodes (LED&#39;s). 
     Description of the Problem 
     There is a need for saving more energy in these under-cabinet luminaries using specifically designed integral power supply with low power consumption to provide power to the Energy Saving LED&#39;s. This invention is an energy saving under-cabinet lighting system. 
     A light emitting diode (LED) is a semiconductor device that creates light using solid-state electronics A diode is composed of a layer of electron nch material separated by a layer of electron deficient material which forms a junction Power applied to this junction excites the electrons in the electron rich material leading to photon emission and the creation of light. Depending on the chemical composition of the semiconductor layers, the color of light emission will vary within the visible range of electromagnetic spectrum. 
     LED&#39;s are much more energy efficient than their incandescent and fluorescent lamps LED&#39;s are very energy efficient producing up to 90 percent light output with very little heat dissipation. Also, LED lighting technology includes features such as less energy consumption, long service life, high quality light, and suitability for cold temperature operation In addition, LED&#39;s do not contain mercury and are environment friendly 
     In addition, there is a great need to place a USB port on the surface of lighting fixtures to charge accessories such as laptops, tables and cellular telephones. However, charging lithium-ion batteries has fire hazard problems in that, if they receive too much charging current, they overheat. It would be very advantageous to have a lighting system with a USB port that can safely charge accessories without the danger of overheating. 
     Generally there are 2 types of power supplies, magnetic and electronic switch mode In this lighting system, the switch mode electronic power supply is used for energy efficiency, low profile, and light weight, to provide power to LED&#39;s. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an energy saving under-cabinet luminaries using an energy efficient switch mode power supply optimized to provide maximum power to the LEDs while remaining within UL class 2 requirements of the Power Supply. These luminaries have a safe USB charging port that can safely charge lithium-ion batteries of accessories. 
     The present invention provides an energy saving under-cabinet Luminaire consisting of an enclosure, Class 2 integral power supply to provide power LEDs arranged in a special pattern to effectively replace 8 W, 13 W and 15 W fluorescent lamps or equivalent halogen lamps resulting in 50% of energy savings. Every component is individually optimized to save energy. The simplicity of the power supply using very few components greatly improves the reliability of this lighting system. The power supply is isolated and coupled to the LEDs so that it has a power factor of at least 90%. 
     A specially angled diffuser to converge the light output from the lighting system of the working area of the under-cabinet. The lenses of the LEDs are so chosen that the inner array near the wall has 30 degrees spread, and the outer array away from the wall has 60 degree spread to achieve more light in the working area of the under-cabinet. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       Attention is directed to several figures that illustrate features of the present invention: 
         FIG. 1  shows the full exploded view of the entire LED under-cabinet unit lamp unit with all components marked. 
         FIG. 2A  shows the front view of a first type of quick input connector for easy electrical connections. 
         FIG. 2B  shows the front view of a second type of quick output connector for easy electrical connections. 
         FIG. 3A  shows the front view array of layout of the LED&#39;s on a printed wiring board for 56 LED boards. 
         FIG. 3B  shows the front view array of layout of the LED&#39;s on a printed wiring board for 80 LED boards. 
         FIG. 4  shows the wiring of 80 LED&#39;s in series parallel circuit. 
         FIG. 5  shows the wiring of 56 LED&#39;s in series parallel circuit. 
         FIG. 6  shows the schematic diagram of the circuit of the LED Power Supply with components marked. 
         FIG. 7  shows the construction details of the output transformer of the LED Power Supply. 
         FIG. 8  shows a view of the LED under-cabinet unit lamp unit with a USB port. 
         FIG. 9  is a schematic diagram of a power supply for the USB port with a safe charging feature. 
     
    
    
     Several drawings and illustrations have been presented to aid in understanding the present invention. The scope of the present invention is not limited to what is shown in the figures. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the preferred embodiment, as illustrated in  FIG. 1 , the main components are the input power connector  8 , coupled to an external power cord  9 , an enclosed SMPS power supply  3 , providing the necessary voltage and content current to the LED&#39;s  6 , a simple resistive dimmer potentiometer switch  2 , to reduce the current to the LED&#39;s to create dimming effect, a main on/off switch  4 , and an output connector  5  to link the unit with an external interconnect cord  10  to another unit. 
     The unit can be used with quick connectors for electrical safety.  FIG. 2A  shows the front view of a first type of quick input connector for easy electrical connections, while  FIG. 2B  shows the front view of a second type of quick output connector. The connector in  FIG. 2A  has a round/square configuration, while the connector in  FIG. 2B  has a round/round configuration. 
     Two LED configurations can be used, the first with 56 LEDs and the second with 80 LED&#39;s. The 56 LEDs put out enough light output to replace an under-cabinet light fixture using one F8T5 (8 W) fluorescent lamp or equivalent lamp. This is shown in  FIG. 3A . The 80 LEDs put out enough light output to replace and under-cabinet fixture using one F15T8 (15 W) or F13T5 (13 W) fluorescent lamp as shown in  FIG. 3B . The numbers  56  and  80  are chosen to be cost effective. These numbers can change depending on growth of LED technology resulting in cost reduction by using fewer LED&#39;s with higher lumens per watt.  FIG. 4  shows a schematic of the 80 LED circuit, while  FIG. 5  shows a schematic of the 56 LED circuit. In each case, there is a current-limiting resistor  13  in series with the array and a capacitor  14  in parallel with it. 
     The design of the power supply is so chosen to put out 30 VDC maximum and still come under Class 2 requirements of Underwriters Lab (UL Inc.) Standard 1310 by limiting the voltage and current for safety considerations without compromising the optimum performance. An embodiment of such a class 2 power supply is schematically illustrated in  FIG. 6 . 
     The first stage of power supply has an input stage filter network consisting of a metal oxide varistor  17 , rated at 150V for surge suppression, a safety current limiting fuse  27  rated ½ A 250 VAC, and an across-the-line capacitor  6 , rated 22 pF at 250V to absorb the transients. 
     The second stage is a full wave bridge rectifier consisting of a bridge rectifier  18 , with four diodes, rated 1 Amp. 400V with a filter capacitor  20 , rated 4.7 uF, 400V. 
     The third stage is a is a feeder network coupling the rectified AC voltage to an integrated control chip  21  which determines the pulse width after converting the rectified voltage to a high frequency chopped voltage. 
     The processed signal is fed to the transformer  26  with a ferrite core having the following construction: 
     Primary Windings: 
     Wind 18T on the magnet core EFDI5 FROM Pin I to Pin 3 by 0.15 enamel. 
     Secondary Windings: 
     Wind 135T on the magnet core EFDI5 FROM Pin 2 to Pin 4 by 0.2 mm enamel. 
     Wind 32T on the magnet core EFDI5 FROM Pin 8 to Pin 5 by 0.2 mm×3 enamel. 
     An auxiliary secondary has 7 turns of 0.15 mm enameled copper wire. This winding is also used in the feed back circuit to regulate the output voltage and current. 
     The transformer  26  steps down the input high voltage pulses to low voltage pulses. The diode  28 , rated 1 Amp. 400V is a rectifier which is coupled to a resistor  32  rated 5.1 ohms through inductor  29 . 
     An output filter network consists of a resistor  34  rated 10 Ohms coupled to a capacitor  35  rated 680 pF 150V in series coupled to parallel capacitors  36  and  39  rated 220 uF 50V to smooth out the ripple in the output waveform. Output filter choke  29  is coupled between capacitor  37  and diode  28 . This choke stores magnetic energy to provide a constant output current and voltage to LED&#39;s. 
     Resistor  38  rated 44 k ohms ½ w, is connected to choke  29 . Choke  29  and a parallel capacitor  33  rated 470 uF 30V form the output filter network. 
     An adjustable reference zener diode  30  is provided to regulate output voltage and current. This zener is coupled to the power supply through resistors  32  and  38 , rated 5.1 k Ohms and 44 k ohms respectively. 
     The turn on reference voltage is determined by resistors  32  and  38 . When the output exceeds the set voltage, the zener diode  30  provides a turn on signal to opto-isolator  40 , model PC8  17  which is coupled to capacitor  23  rated 22 pF 50V which is further coupled to pin 5 of  21  to regulate the output. Capacitor  22  rated 68 pF 50V provides the timing frequency for oscillations. 
     Diode  24  rated 1 Amp. 700V is coupled to the transformer auxiliary winding of transformer  26  and capacitor  25  rated 47 uF 16 V. This network provides start up current for the transformer oscillations. Capacitor  37  rated 100 uF 50 V provides necessary filtering of the output voltage by reducing the output ripple. 
     The LED&#39;s are laid out in a Flame retardant Printed Wiring Board (PWB) as shown in  FIGS. 3A and 3B  and convert the electric power input into visible white light to illuminate the under-cabinet area. The output coupling connector  10  shown in  FIG. 1  may be used to couple another unit as needed. 
       FIG. 7  is an illustration of output transformer segments, primary  41 , auxiliary winding  42  and secondary  43 . 
       FIG. 8  shows a view of a fixture with a USB port  50 . The USB port is conveniently located for safe charging of accessories. The present invention can also be equipped with a polycarbonate plastic diffuser  51  shown in  FIG. 8  that is about 2 mm thick of the type of translucent plastic called LEXAN™ made by General Electric and others. This diffuser is used for dispersion of dots pixualization from the LED in order to obtain uniform lighting. This reduces the Dot Matrix LED lighting. The optimum distance from the LEDs to the diffuser has been found to be 17 mm which makes the light more uniform and greatly reduces the pixualization further reducing the Dot Matrix LED lighting. 
       FIG. 9  shows a schematic diagram of an embodiment for a USB port power supply: The 120V, 60 Hz power from the mains has input fusible resistors R 1  rated 1 ohm, 1 watt. It is then rectified by a bridge rectifier Dl. The rectified signal is filtered by a capacitor C 2  rated 6.8 uF 400V. The filter network is π (PI) filter formed by C 1 , R 1  and C 4  and further filtered by choke L 1  and capacitor C 2 . These filters also help to reduce Electro Magnetic Radiation (EMI) back to the input mains by conduction process. The filtered output is coupled to a ferrite core high frequency transformer T 1 . The transformer is further coupled to Control IC chip U 1 . This controls the pulse width and frequency of rectified waves of the Primary of transformer T 1 . 
     There is a feed winding (pins 4 and 5) set up through a potential divider circuit formed by resistors R 6  and R 7  that is coupled to chip U 1 . This controls the output voltage constant 5 VDC by controlling the pulse width. The secondary of the transformer (pins 6 and 10) is stepped down low voltage pulses and further smoothly rectified by a diode D 8  rated 2 Amp 50 V. This signal is then fed to a capacitor C 51  further smoothes the ripple and coupled to capacitor C 52  through a series filter inductor choke L 10 . Across the output terminals pin 1 and pin 4 an indicator LED is connected in parallel with a series current limiting resistor R 56  rated 470 Ohms ½ W. The output voltage is a regulated 5 VDC. 
     The 5 VDC output is connected to pins 1 and 4 of the USB connector (outer pins). The output pin 1 is connected to a series positive temperature coefficient (PTC) thermistor to regulate and limit the charging current to a safe value of approximately 400 mA. Excessive charging current will result in overheating the lithium-ion batteries resulting in a fire hazard. The lithium-ion batteries have a very high charge density. So, charging current should be limited to safe value between 300-400 mA for typical charging a laptop or a cellphone. The PTC thermistor PT 1  typically offers less than 1 ohm under operating normal current and the Resistor value increases to very high value to limit the charging current 
     The thermistor PT 1  is operated under self heating mode. In this mode, it is in series connected with the battery load. It heats up as the current increases until it reaches a critical temperature Tc; then the resistance increases by large amount thereby reducing the current. So it acts as safe cut off regulator reducing the hazard created by excessive charging current to the battery. 
     The Thermistor PT 1  is so chosen in such a way that the typical resistance is approximately 0.3 ohm at 25 degrees C. at non-trip current (Int), and the value increases to 1-2 k Ohms or more at around 450 mA at trip current (It). This feature of the present invention positively prevents the batteries in the charging accessory from overheating by providing over-current protection. 
     The 5 VDC output is voltage is further divided to approximately to 2.5 VDC by potential dividers formed by resistors R 52  and R 54 , rated 10 k Ohms ½ w which couples to pin 2 of the USB Port. Resistors R 53  rated 10 k Ohm ½ W and R 55  rated 10 k Ohm ½ W form another potential divider that couples to pin 3 of the USB port. In this embodiment of the power supply, the pins do not transfer any data since no data is stored or delivered by the under-cabinet luminaire. 
     The power supply from the mains 120 VAC 60 Hz, can also be connected to the convenient outlet. 
     Several descriptions and illustrations have been presented to aid in understanding the present invention. One with skill in the art will realize that numerous changes and variations may be made without departing from the spirit of the invention. Each of these changes and variations is within the scope of the present invention.