Abstract:
An apparatus operable in a wet environment for controlling the brightness and color of a solid state light emitting diode, lamp assembly which is adapted to be coupled to an AC source for supplying an AC signal. A plurality of switching devices are connected in series with the lamp assembly and light emitting diodes. The switching devices are operative in either a first state, wherein significant current flowing through the lamp assembly is prevented or a second state wherein current flow through the lamp assembly is substantially undisturbed. User controls provide lamp assembly brightness and color input signals to a controller. Also included is a controller means for receiving lamp assembly brightness and color input signals from the user controls, and for switching the switching devices between the first and second states in a predetermined sequence for inducing pulse width modulation signals to the lamp assembly. The isolation means for electrically isolating the user controls from the AC source, includes an electrical current barrier.

Description:
RELATED APPLICATIONS  
       [0001]    The applicant claims priority of provisional application 60/255919, filed Dec. 18, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to light emitting diodes and associated methods of color and brightness control. More particularly, the present invention relates to a controller and pulse width modulator that employs current modulation which operates to vary the relative color and brightness of each of a red, green and blue light emitting diode for use in a wet or electrically hazardous environment.  
         BACKGROUND OF THE INVENTION  
         [0003]    Bathing appliances such as hot tubs, swimming pools, shower units and hydromassage bath fixtures often employ a means of under water lighting to create a desired ambience in the bathing environment. As “ambience” is a subjective description generally relating to color and brightness, it is not possible for one light type to satisfy every users&#39; desired settings.  
           [0004]    Prior art underwater bathing lamps are known to utilise electric incandescent bulbs and insulation means. However, such systems often lack the ability to control brightness and are not capable of controlling color output.  
           [0005]    It is not practical to install numerous lighting appliances, each with a different brightness and color. Therefore, a means of adjusting the desired parameters of brightness and color would be a desirable feature.  
           [0006]    Furthermore, an electrical, incandescent lighting system installed in a wet environment is considered to be hazardous due to the possibility of electrical energy used to power the light “leaking” into the bathing water and creating a shock hazard.  
           [0007]    Another known system includes an arrangement of fiber optics which channel light to outlets located through out the bathing system structure. A bright, white light source is forced into the fiber optic at a location sufficient far away from the bath water that no electric shock hazard will result. The white light transmitted through the fiber optic to the bath water may be made to change color by inserting a color wheel element in between the light source and the entrance to the fiber optic. Rotating the color wheel inserts different colors of filter into the light path, thereby changing the light beam at the bathing appliance. Such systems generally have limited functionality or excessive cost for the features provided.  
           [0008]    Alternatively, a triad (meaning a single light source of red, green blue combination or a grouping of any number or combination of red, green and blue light source, typically light emitting diodes) of high luminous output red, green and blue light emitting diodes installed in a suitable chassis and lens assembly may be fitted into the bath structure. When such an arrangement of light emitting diodes are connected to a controller and pulse width modulator, the output light brightness and color may be adjusted over a very large setting range, creating a useful “ambience”.  
           [0009]    A triad grouping of red, green and blue, light emitting diodes coupled to a controller and pulse width modulator provides an effective arrangement for providing adjustable brightness and color of light to a bather in a bathing appliance. As an alternate embodiment, it is possible to use any plurality of colored light source to converge or mix the primary output colors and produce non-primary colored light. However, the power necessary to operate the triad of light emitting diodes or other light source may still be sufficiently great to create a shock hazard to a bather operating the light system&#39;s controls or through electrical “leakage” from the chassis assembly, while in the bathing system. Thus, the bather will be in danger of electrocution if not protected from the electric source of the light emitting diodes while operating the light controls or simply being immersed in the bathing water. This creates a practical dilemma as the user cannot convey his commands to the light controller without “bridging” the electrical isolation barrier, putting himself at risk of shock.  
           [0010]    Accordingly, it is an object of the present invention to provide a light control system having a triad of light emitting diodes with red, green and blue luminous output, or control apparatus and pulse width modulator incorporating associated methods to control color and brightness of the light for installation in wet, electrically hazardous bathing environments.  
           [0011]    Accordingly it is an object of the present invention to provide an improved lighting brightness and color controller.  
           [0012]    A further object of the present invention is to provide a solid state lamp assembly consisting of a triad of red, green and blue light emitting diodes.  
           [0013]    A further object of the present invention is to provide a controller utilising a pulse width modulator and switching device coupled to each of the red, green and blue light emitting diodes individually.  
           [0014]    A further object of the present invention is to provide a lighting system controller that is safely operable by a bather immersed in water.  
           [0015]    A further object of the present invention is to provide an improved method for controlling the brightness and color of a solid state lamp assembly consisting of a triad of red, green and blue light emitting diodes.  
         SUMMARY OF THE INVENTION  
         [0016]    To protect the bather from electric shock, the electrical energy driving the first, second and third light emitting diodes and user control is sufficiently isolated from the bather by providing impedance isolation of the control circuits from the electrically conductive bath water. Impedance isolation may be preferably implemented utilising an impedance protected, stepdown, isolation transformer.  
           [0017]    According to the invention, there is provided an apparatus operable in a wet, electrically hazardous environment, for controlling the brightness and color output of a solid state lamp assembly consisting of a triad of red, green and blue light emitting diodes, which are adapted to be coupled to a controller for supplying a dc control signal, the apparatus comprising:  
           [0018]    a first switching device coupled to a first light emitting diode, a second switching device coupled to a second light emitting diode and a third switching device coupled to the third light emitting diode, each of the switching devices being operative in a low impedance state thereby enabling current to flow through the associated light emitting diode of each switching device and a high impedance state thereby preventing significant current flow through the associated light emitting diode of each switching device;  
           [0019]    a pulse width modulator for switching each switching device between its high and low impedance state;  
           [0020]    user controls for providing lamp brightness and color input signals;  
           [0021]    a controller means for receiving the lamp brightness and color signals from the user controls and for controlling the pulse width modulator, in turn switching each switching device between its high and low impedance states in a sequence for inducing a change in relative brightness between the first, second and third light emitting diodes; and  
           [0022]    isolation means for electrically isolating the user controls from the AC source, wherein the isolation means includes an electrical current barrier.  
           [0023]    In an embodiment of the invention, there is provided an apparatus operable in a wet, electrically hazardous environment, for controlling the brightness and color output of a solid state lamp assembly consisting of a triad of red, green and blue light emitting diodes, which are adapted to be coupled to a controller for supplying a dc control signal, the apparatus comprising:  
           [0024]    a first switching device coupled to a first light emitting diode, a second switching device coupled to a second light emitting diode and a third switching device coupled to the third light emitting diode, each of the switching devices being operative in a low impedance state thereby enabling current to flow through the associated light emitting diode of each switching device and a high impedance state thereby preventing significant current flow through the associated light emitting diode of each switching device;  
           [0025]    a pulse width modulator for switching each switching device between its high and low impedance state;  
           [0026]    user controls for providing lamp brightness and color input signals;  
           [0027]    a controller means for receiving the lamp brightness and color signals from the user controls and for controlling the pulse width modulator, in turn switching each switching device between its high and low impedance states in a sequence for inducing a change in relative brightness between the first, second and third light emitting diodes; and  
           [0028]    a first, second and third switching means comprising first, second and third respective transistors and wherein the first transistor is connected in series with the first light emitting diode and has a first base input connected to the pulse width modulator “A” output channel means and the second transistor is connected in series with the second light emitting diode and has a second base input connected to the pulse width modulator “B” output channel means and the third transistor is connected in series with the third light emitting diode and has a third base input connected to the pulse width modulator “C” output channel means and where pulse width modulator input channels “A”, “B” and “C” are respectively connected to the controller means.  
           [0029]    According to the invention, there is further provided a method for controlling the brightness and color output of a solid state lamp assembly consisting of a triad of red, green and blue light emitting diodes, which are adapted to be coupled to a controller for supplying a dc control signal, the apparatus comprising:  
           [0030]    a first switching device coupled to a first light emitting diode, a second switching device coupled to a second light emitting diode and a third switching device coupled to the third light emitting diode, each of the switching devices being operative in a low impedance state thereby enabling current to flow through the associated light emitting diode of each switching device and a high impedance state thereby preventing significant current flow through the associated light emitting diode of each switching device;  
           [0031]    a pulse width modulator for switching each switching device between its high and low impedance state;  
           [0032]    user controls for providing lamp brightness and color input signals;  
           [0033]    a controller means for receiving the lamp brightness and color signals from the user controls and for controlling the pulse width modulator, in turn switching each switching device between its high and low impedance states in a sequence for inducing a change in relative brightness between the first, second and third light emitting diodes; and  
           [0034]    isolation means for electrically isolating the user controls from the AC source, wherein the isolation means includes an electrical current barrier means;  
           [0035]    the method comprising the steps of:  
           [0036]    (a) detecting a user input control signal comprising lamp color and brightness data  
           [0037]    (b) generating a series of pulse width modulator control variables  
           [0038]    (c) activating pulse width modulator with control variables, enabling current to flow through a first, second and third switching device in turn enabling a grouping of red, green and blue light emitting diodes, which are series connected to their respective first, second and third switching devices.  
           [0039]    Other advantages, objects and features of the present invention will be readily apparent to those skilled in the art from a review of the following detailed description of the preferred embodiment in conjunction with the accompanying drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]    The embodiments of the invention will now be described with reference to the accompanying drawings, in which;  
         [0041]    [0041]FIG. 1 is a schematic of the prior art under water lamp, utilising an isolation transformer mean;  
         [0042]    [0042]FIG. 2 is a schematic of the prior art under water lamp, utilising an optical fiber;  
         [0043]    [0043]FIG. 3 is a schematic of one preferred embodiment of the solid state lamp controller of the present invention;  
         [0044]    [0044]FIG. 4 is a wave form diagram of the voltage signal output of three channels of a pulse width modulator which, when connected to suitable switching devices and a grouping of red, green and blue Light Emitting Diodes, (LEDs) provides the correct signal ratios for the LEDs to output white light. The wave forms depict timing diagrams for light intensity at nearly full power and at approximately 50% power; and  
         [0045]    [0045]FIG. 5 is a flow chart illustrating the pulse width modulator control sequence of the controller of the present invention.  
         [0046]    With respect to the above drawings, similar references are used in different Figures to denote similar components. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]    Referring to FIG. 1, there is shown an embodiment of a prior art electrical, incandescent, under water lamp system. In this embodiment an incandescent lamp  45  is connected to the secondary windings  17  of isolation transformer  15 , through series current limiting fuse  30 . The primary windings  19  of isolation transformer  17  are connected to a source of AC mains voltage  10  through current limiting fuse  20  and are electrically isolated from the secondary windings  17  by ground shield  25 . A ground shield  25  completely encloses primary winding  19  and is firmly connected to safety ground  27  to prevent any leakage current from primary winding  19  entering secondary winding  17 , and causing a shock hazard. Current limiting fuses  20  and  30  are designed to open should the transformer enter a fault condition which may damage the insulation inherent in windings  17  and  19 .  
         [0048]    Incandescent lamp  45  is housed in a suitable chassis  40  which is installed in the bathing appliance wall  35 . The light output lens  50  contains a suitable metal apparatus that is in turn firmly coupled to a redundant safety ground  55 .  
         [0049]    While this prior art embodiment is considered to be electrically safe, its construction is often expensive due to the large capacity of isolation transformer  15  required to power incandescent lamp  45 . Further, such embodiments offer little if any practical means for lamp brightness or color control.  
         [0050]    The prior art embodiment shown in FIG. 1 is typical of most underwater lamp assemblies, varying only in electrical capacity and construction means.  
         [0051]    Referring to FIG. 2, there is shown a second embodiment of a prior art underwater lamp system. In this embodiment, the incandescent lamp  45  is coupled to secondary winding  117  of simple isolation transformer  115 . Primary winding  119  of isolation transformer  115  is series coupled to over-current fuse  120  and connected to an AC source  10 . The light output  46  of lamp  45  is coupled into optical fiber  80 . Light emerges  48  from optical fiber  80 . Optical fiber  80  is placed in a suitable housing  90 , which is in turn mounted in the bath appliance wall  35 . Light emerges through lens  91 .  
         [0052]    An optional color wheel  70  may be installed in-between lamp  45  and optical fiber  80 . This wheel can be manually operated or driven by motor  60  through series connected switch  65 . When switch  65  is closed, current flows from the secondary winding  117  of transformer  115  into motor  60 . Motor  60  is suitably designed to rotate color wheel  70  to permit different color filters  71 ,  72  to pass in front of lamp beam  46  and convert filtered output light  47  to the color of lens  71 .  
         [0053]    The use of optical fiber  80  provides an electrical isolation means sufficient to prevent electrocution and results in a simplified isolation transformer  115  and housing  90  as compared to the embodiment shown in FIG. 1. Additionally, the use of optical fiber  80  allows for a color wheel  71  to provide a crude means of color control.  
         [0054]    The use of optical fiber, color wheels, and complex isolation transformers as noted in FIG. 1 and FIG. 2 is a drawback. Adding such components increases the cost, weight and installation complexity of these prior art lamp systems. Also, the ability to set the “ambience level” of brightness and color is very crude and not generally suitable in the market.  
         [0055]    Now referring to FIG. 3, there is shown an embodiment of the solid state underwater lamp controller  200 . An advantage of the controller  200  is that it does not require the use of incandescent lamps, complex shielded, isolation transformers or mechanical color wheels to generate light and modify its brightness or color. The present invention utilises a solid state lamp assembly which is implemented by red, green and blue light emitting diodes  160 ,  161  and  162 , respectively. Suitable devices for light emitting diodes  160 ,  161 ,  162  would be high optical brightness LEDs or groupings of lower power devices. For example, the lamp assembly could utilise a quantity of 3 red, 4 green and 5 blue light emitting diodes. The present invention varies the brightness of light emitting diodes  160 ,  161 ,  162  in relation to each other by a pulse width modulation technique, which is implemented by controller  130  and pulse width modulator  140 , which are preferably combined in a microcontroller integrated circuit. One preferred microcontroller is the Motorola MC68HC705GP20 device operating at a crystal frequency of 4 MHz. Such an arrangement of crystal and microcontroller will provide for the orderly processing of input stimuli received from user control  110  and output control to attached peripheral devices such as transistor switch “A”  150 . As an alternative, the transistor means may comprise a field effect transistor. By way of example, the user input control  110  may be comprised of input switches or a radio receiver device. The orderly processing of such inputs and outputs are completed by execution of the flowchart patterns shown in FIG. 4. A person skilled in the art will be familiar with microcontrollers such as the Motorola MC68HC705GP20, transistors, field effect transistors, input switches and radio receiver devices.  
         [0056]    As described above, the present invention does not require a complex or expensive isolation transformer system owing to the low power requirements of the light emitting diodes  160 ,  161 ,  162 . One preferable embodiment of the logic power supply  105  is provided by an impedance protected, step-down transformer.  
         [0057]    The red, green and blue light emitting diodes  160 ,  161 ,  162  may be mounted in a suitable housing that allows their respective light output to converge and “mix”. By varying the brightness in relationship to one another, it is possible to generate an homogenous beam comprising most colors of the visible spectrum. Additionally, if the brightness ratio between the respective light emitting diodes remain the same, but the output optical power is decreased in unison, brightness of the output beam can also be controlled, without modifying color. Obviously if differing numbers of light emitting diodes are utilised or if the optical output power varies, the pulse width modulation ratio between light emitting diodes will have to be adjusted accordingly. A person skilled in the art will be familiar with the use of a pulse width modulator to vary the optical output power of a single light emitting diode. Adjusting the relationship between the triad of a red, green and blue light emitting diode “set” is more complex and will now be explained by reference to the graphical relationship showing the controller and pulse width modulator signals in FIG. 4.  
         [0058]    Referring to FIG. 4, a graphical representation of pulse width modulation for a fixed color of white and varying the brightness between 100% and 50% is shown, by way of example. Waveforms (a), (b) and (c) show a digital representation of one time cycle for three synchronised pulse width modulators discussed earlier. Waveforms (a), (b) and (c) represent pulse width modulator outputs  141 ,  142  and  143  and are the control signals for the red, green and blue light emitting diodes (LED) respectively. Now referring to waveform (a), the start of the first timing cycle  320  indicates that the red LED is activated  305  for approximately 50% of the first timing cycle  320  and deactivated  310  for the remaining 50% of first timing cycle  320 . In a similar manner, the green LED control signal shown in waveform (b) is activated for slightly more time  335  than the red LED described in waveform (a) and deactivated  340  for less time than the red LED described in waveform (a). The sum of the activated time  335  and deactivated time  340  of waveform (b) equalling one timing cycle  320 . And in a similar manner, the blue LED shown in waveform (c) is activated for slightly more time  355  than the red or green LEDs shown in waveform (a) and (b) respectively and deactivated for less time  360  than either the red or green LEDs. The sum of the activated time  355  and deactivated time  360  of waveform (c) equalling one timing cycle  320 . Although the exact characteristics of each physical red, green and blue LED will vary, it is known that the optical power of each color of LED and the apparent intensity due to the response of the human eye to that color, will vary. The example shown in FIG. 4, waveforms (a), (b) and (c) typifies an example where the convergence of the red  160 , green  161  and blue  162  optical outputs will cause a response in the human eye of color “white”. Furthermore, the intensity of the light output for the color white is shown to be near the maximum, because, in this example, the blue  162  LED is activated  355  for nearly 100% of the first timing cycle  320  of waveform (c). Increasing the activation duration of each of red, green and blue to 100% of the first timing cycle would result in greater brightness, but of some different color owing to the different intensity ratios output by the respective LEDs.  
         [0059]    Now as further shown in FIG. 4, there is shown a set of waveforms (d), (e) and (f) which represent pulse width modulator outputs  141 ,  142  and  143  respectively, which also output the color “white” but at an intensity of approximately 50% of that shown in waveforms (a), (b) and (c), described above. By way of this example, the red LED pulse width modulator control signal  141 , shown in waveform (d) is now modified to activate  400  for a time approximately 50% of the time in  305 . Furthermore, the red LED pulse width modulator  141  is deactivated  405  for a time period approximately twice as long as  310 , the sum of activated time  400  and deactivated time  405  being equal to the first timing cycle time  320 . In a similar manner, green LED pulse width modulator control signal  142 , shown in waveform (e) is now modified such that the activated time  410  and deactivated time  415  are approximately 50% and 200% of the respective time control signals  335  and  340 . And in a similar manner, blue LED pulse width modulator control signal  143  is now modified such that the activated time  420  and the deactivated time  425  are approximately 50% and 200% of the respective time control signals  355  and  360 . In this manner, the ratio of activated to deactivated time of waveform (d) is approximately 50% that of waveform (a), as is the ratio of activated to deactivated time of waveform (e) to that of waveform (b) and, as is the ratio of activated to deactivated time of waveform (f) to waveform (c). The resulting reduction of activated time by approximately 50% results in a similar decrease in brightness of approximately 50%. Simultaneously, the proportion of activated time  400 ,  410  and  420  must remain the same as the proportion of activated time  305 ,  335  and  355  to maintain the same color. By way of further example, the ratio of activated time  305  to activated time  335  and activated time  305  to activated time  355  must remain the same as reduced brightness, activated time  400  to activated time  410  and activated time  400  to activated time  420 , to maintain the same color.  
         [0060]    The appropriate ratios described above may be calculated using an algorithm or determined by previous empirical experimentation, with the results stored in the controller  130  means.  
         [0061]    A person skilled in the art will understand the methods of color mixing and intensity utilising the primary colors of red, green and blue to create alternate colors. Further, a person skilled in the art will understand how a controller and pulse width modulator will provide the control ratios described.  
         [0062]    Referring to FIG. 5, a flow chart of the pulse width modulator sequence  500  of the controller  130  is shown. The entry point TURN OFF PULSE WIDTH MODULATOR  141 ,  142 ,  143 , step  510  will cause the controller  130  to disable the pulse width modulator  140  which will cause output “A”  141 , output “B”  142  and output “C”  143  to deactivate, which will cause switch “A”  150 , switch “B”  151  and switch “C”  152  to enter a high impedance state, disabling the flow of current in red LED  160 , green LED  161  and blue LED  162 . Ensuring that switches  150 ,  151  and  152  are in their off state will turn off the lamp.  
         [0063]    In the IS LAMP REQUESTED ON? step  520 , the controller  130  will monitor the user control input signal  110 . The controller  130  will not advance to the next step until the user requests the lamp to be turned on. The lamp will remain in the off state by the controller executing the loop consisting of TURN OFF PULSE WIDTH MODULATOR  141 ,  142 ,  143 , step  510  and IS LAMP REQUESTED ON? step  520 . When a user selection has been detected in step  520  by user input signal  110 , the controller will advance to CALCULATE APPROPRIATE RATIOS OF PULSE WIDTH MODULATOR OUTPUTS  141 ,  142 ,  143  TO PROVIDE DESIRED LAMP CONTROL AND BRIGHTNESS step  530 , which will be executed.  
         [0064]    In the DETERMINE APPROPRIATE RATIOS OF PULSE WIDTH MODULATOR OUTPUTS  141 ,  142 ,  143  TO PROVIDE DESIRED LAMP CONTROL AND BRIGHTNESS step  530 , the controller will determine the pulse width modulator ratios necessary to provide the desired lamp brightness and color. The data will be based on empirical experimentation with the results forming the controller structure. One preferred embodiment of the appropriate modulator ratios used by controller  130  and pulse width modulator  140  would be to store the data derived from the experimentation described above inside a microcontroller, with integral pulse width modulator. A person skilled in the art would be familiar with the nature of storing data inside such a microcontroller device. The controller will now load the pulse width modulator with the resulting LED ratio data by executing SET PULSE WIDTH MODULATOR TO APPROPRIATE, DETERMINED VALUES step  540 .  
         [0065]    In the SET PULSE WIDTH MODULATOR TO APPROPRIATE, DETERMINED VALUES step  540 , the pulse width modulator will immediately start a first timing cycle  320  with outputs  141 ,  142 ,  143  cycling between their respective on/off ratios, as previously described above and shown in FIG. 4. When any of pulse width modulator outputs  141 ,  142  or  143  are activated, the correspondingly connected switches  150 ,  151  or  152  will enter their low impedance state, causing current to flow in their respectively, series connected light emitting diodes. As previously discussed, the output light from the triad of light emitting diodes  160 ,  161  and  162  will be placed in a manner to combine or “mix” the resulting output light. The user will see the output light beam as a approximately homogenous color of selected brightness. The pulse width modulator must have a timing duty cycle  321  sufficiently fast to prevent “flicker” of the red, green and blue LEDs,  160 ,  161  and  162 , respectively. The pulse width modulator will execute SET PULSE WIDTH MODULATOR TO APPROPRIATE, DETERMINED VALUES step  540  and return to IS LAMP REQUESTED ON, step  520  where upon the pulse width modulator sequence  500  of the controller  130 , is repeated.  
         [0066]    Numerous modifications, variations and adaptations may be made to the particular embodiments of the invention described above without departing from the scope of the invention, which is defined in the claims.