Abstract:
An integrated system for supplying direct current and brightness dimming for light emitting diodes (LEDs) comprising: an LED driver power supply for supplying a constant direct current; an array of one or more LEDs; and an integrated programmable LED current pulse width modulation (PWM) dimming controller; wherein the integrated programmable LED current pulse width modulation (PWM) dimming controller comprising: a front control panel for controlling the brightness of the array of one or more LEDs; and an LED current PWM dimming module.

Description:
COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material, which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     FIELD OF THE INVENTION 
     The present invention relates generally to light emitting diode (LED) drivers. More specifically, the present invention relates to the brightness dimming control circuitry of LED. 
     BACKGROUND 
     Traditionally, incandescent and fluorescent lights have been the primary source of artificial illumination. However, significant advances in the light emitting diode (LED) technology have made the light output of LEDs not only for indicator applications but also sufficient for general illumination. 
     LEDs are a type of semiconductor device requiring direct current (DC) electricity input source for operation. Conventional LED lighting unit comprises a LED driver power supply, a dimming module, a dimming controller panel, and arrays of LEDs. The LED driver power supply takes an external electricity power input source and convert to a constant direct current output, feeding the dimming module and in turn the LEDs. For land and building use, the external power source is usually an alternative current electricity power source. In such conventional LED lighting unit, one limitation is that the choice of LED driver power supply used must be carefully matched with the capacity of the LEDs, as the maximum current driving the LEDs is fixed by the LED driver power supply based on its type and capacity. 
     One common type of dimming module is the low frequency Pulse-width Modulator (PWM). The average value of current fed to the load LEDs is controlled by turning a switch between the power input and load on and off at a fast pace. The longer the switch is on compared to the off periods, the higher the current supplied to the load is. Thus, the current supplied to the LEDs is I min ≦I LED ≦I Driver , where I LED  is the current supplied to the LED; I Driver  is the direct current output of the LED driver power supply; and I min  is minimum current that the PWM dimming module can output. The switching frequency of this type of PWM dimming module is usually controlled by a separate dimming controller panel. One disadvantage of this arrangement is the complicated wiring and installation. Another disadvantage is the relatively high cost associated with a separate dimming controller panel. 
     U.S. Patent Application Publication No. 2007/0097043 discloses a LED driver aims to improve the efficiency of LED by adjusting the feeding current in correlation with the LED temperature. In this disclosure, although a control circuit is used to adjust the feeding current to the LED, this control circuit is to maintain a constant chromaticity and/or luminosity of the LED and is not meant to be used to adjust the brightness of the LED. 
     U.S. Pat. No. 6,586,890 discloses a driver circuit for LEDs using pulse width modulation (PWM). It also uses current feedback to adjust power to the LEDs and provides a full light and a dim mode. The disclosed driver circuit aims to provide good regulation and efficiency while the current feedback is to maintain operation at the LEDs&#39; nominal current. But the disclosed system is not an integrated system providing both a constant D/C and user-adjustable dimming functionality. 
     SUMMARY 
     It is an objective of the presently claimed invention to provide an integrated LED driver, dimming, and control system that eliminates complicated wiring and the high cost associating with using separate components for the dimming control panel and the PWM unit. 
     It is a further objective of the presently claimed invention to provide the feature of a configurable maximum LED feeding current from a constant DC power supply such that LEDs of different types and capacity can be used without the need of matching LED drivers. 
     In accordance with various embodiments, the presently claimed programmable LED current PWM dimming controller integrates a light dimming control front panel with a PWM dimming module. The integrated light dimming control front panel can be one of the types of light dimming control panel including a mechanical-analog dial type control, a mechanical-analog slider type control, and an electronic-digital type control. Because light dimming control front panel is integrated with the PWM dimming module, only two sets of electrical wires are needed for the LED driver power supply current input connection and LED feeding current output connection. 
     In accordance with one embodiment, the presently claimed programmable LED current PWM dimming controller includes a trim pot or selector with a constant current DC-DC buck converter for stepping down the maximum LED feeding current, such that different types of LEDs can be driven by the same LED driver power supply; particularly in the case where the LED driver is supplying a constant DC current that is higher than LEDs&#39; rated maximum input current. 
     In accordance with another embodiment, the presently claimed programmable LED current PWM dimming controller can provide an automatic compliance LED voltage feeding from one LED to a maximum number of LEDs where the aggregate voltage drop is within the range of V in −2V, where V in  is the feeding voltage to the one or more LEDs that are connected in series. 
     In accordance with another embodiment, the presently claimed programmable LED current PWM dimming controller includes the feature of over current protection (OCP), over voltage protection (OVP), over temperature protection (OTP), open and short circuit protection. 
     In accordance with another embodiment, the presently claimed programmable LED current PWM dimming controller includes the feature of LED thermal sensing with LED over temperature current compensation and shutdown. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are described in more detail hereinafter with reference to the drawings, in which 
         FIG. 1  shows a block diagram schematically illustrating a LED lighting system including an embodiment of a programmable LED current PWM dimming controller; 
         FIG. 2  shows a block diagram schematically illustrating an embodiment of a programmable LED current PWM dimming module; 
         FIG. 3  shows a block diagram schematically illustrating the wiring configuration between the programmable LED current PWM dimming module and a mechanical-analog control front panel; 
         FIG. 4  shows a block diagram schematically illustrating the wiring configuration between the programmable LED current PWM dimming module and a electronic-digital control front panel; and 
         FIG. 5  illustrates schematically the circuitry of an embodiment of a programmable LED current PWM dimming module. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, system and apparatus of programmable LED current PWM dimming controller and the like are set forth as preferred examples. It will be apparent to those skilled in the art that modifications, including additions and/or substitutions may be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation. 
     Referring to  FIG. 1 . In accordance with various embodiments the presently claimed programmable LED current PWM dimming controller  104  integrates a light dimming control front panel  105  with a PWM dimming module  107 . The light dimming control front panel  105  can be one of the types of light dimming control panel including a mechanical-analog dial type control, a mechanical-analog slider type control, and an electronic-digital type control. The control front panel  105  can be own low cost design or a third party standard product. The control front panel  105  is attached to the backend PWM dimming module  107  via a slot-in interface  106 . Because light dimming control front panel  105  is integrated with the PWM dimming module  107 , only two pairs of electrical wires  103  and  108  are needed for the LED driver current input connection and LED feeding current output connection respectively. 
     In accordance with one embodiment, the PWM dimming module  107  features a low frequency 1 kHz to 3 kHz pulse current dimming output. 
     In accordance with another embodiment, the PWM dimming module  107  features an automatic compliance LED voltage feeding from one LED to a maximum number of LEDs where the aggregate voltage drop is within the range of V in −2V, where V in  is the feeding voltage to the one or more LEDs that are connected in series. 
     Still referring to  FIG. 1 . In accordance with one embodiment, the presently claimed programmable LED current PWM dimming controller includes a trim pot or selector  109  connected to a built-in constant current DC-DC buck converter for stepping down the maximum LED feeding current, such that different types of LEDs  110  can be driven by the same LED driver power supply  102 ; particularly in the case where the LED driver power supply is supplying a constant DC current that is higher than LEDs&#39; rated maximum input current. For example, when coupled with a LED driver power supply that is rated at maximum output current of 3 A, the available maximum constant current supplying the LED can be from 60 mA to 3 A. 
     In accordance with another embodiment, the PWM dimming module  106  also includes circuitries for over-current protection (OCP), over-temperature protection (OTP), over-voltage protection (OVP), open circuit and short circuit protection. Optionally, the PWM dimming module  107  can include external LED thermal sensing circuitry with LED over-temperature current compensation and shutdown functions. 
     Referring to  FIG. 2 . In accordance with one embodiment, the PWM dimming module includes a 1˜10V voltage source and control input/output module  201  for receiving input signal from an analog type light dimming control front panel and providing a control signal for the processing unit  206  for controlling the pulse width modulation signal characteristic. The PWM dimming module also includes a voltage regulator  202  for maintaining a constant voltage level on the input voltage V in  from the LED driver power supply; an over-voltage protection module  204 ; and an over-temperature protection module  205 . The input voltage V in , along with the PWM signal are fed into the constant current DC-DC buck converter  203  for any current step down as programmed. The current step down is programmed through a trim pot or selector  207 . 
     Referring to  FIG. 3 . In accordance with one embodiment, analog type light dimming control front panel  300  is connected to the PWM dimming module  301 . Both components are integrated as a single unit, where the light dimming control front panel  300  is at the front and the PWM dimming module  301  is at the back as a black box. The analog type light dimming control front panel  300  provides analog control signal via DC-Ctrl+ and DC-Ctrl− wire connection to the MCU of the PWM dimming module. 
     Referring to  FIG. 4 . In accordance with one embodiment, digital type light dimming control front panel  400  is connected to the PWM dimming module  401 . The digital type light dimming control front panel  400  can also include an IF/IR Receiver  404  for remote control functionality. The digital type light dimming control front panel  400  includes a MCU  405  for generating PWM signal for dimming the LEDs. 
     In accordance with one embodiment, the electrical specification of the PWM dimming module is as follows: 
     Input Voltage (V in ) Range: 
     
         
         
           
             12˜48V (V in &gt;LED V f +2V)
 
Output Voltage (LED V f ) Range:
 
             2.7˜48V (Auto Compliance up to LED V f )
 
Adjustable Max. LED Current:
 
             150 mA˜3 A (selectable by trim pot/selector)
 
Power Efficiency:
 
             Typically 85% and up to 95%
 
LED Current Regulation:
 
             +/−1%
 
PWM Dimming Frequency:
 
             1 kHz (Analog dimming) 
             100˜3 kHz (PWM dimming)
 
Dimming Ratio:
 
             1:256 (@ 0˜10V, DC-Ctrl+/− input) 
             1:1000 (@ &lt;1 kHz, PWM input) 
             1:500 (@ &gt;1 kHz˜3 kHz PWM input)
 
+5V Output Current:
 
             100 mA (+/− 10%)
 
DC-Ctrl +/− Input Current:
 
             0V @ 0% LED Current 
             +10V @ 100% LED Current
 
PWM-IN Input Voltage:
 
             2˜5V (high level) 
             0˜0.4V (low level) 
           
         
       
    
     The foregoing description of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art. 
     The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalence.