Abstract:
The invention relates to a LED, and more particularly, to provide a circuit and a modulator to more efficiently drive a LED resulting in improving the matching between power source and LED, lowering LED junction temperature and emitting brighter, richer and more natural colors in a more capacitive way.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates to a LED, and more particularly, to provide a circuit and a modulator to more efficiently drive a LED resulting in improving matching between power source and LED, lowering LED junction temperature and emitting brighter, richer and more natural colors in a more capacitive way. 
       BACKGROUND INFORMATION 
       [0002]    Solid state devices such as LEDs are subjected to very limited wear and tear if operated at low currents and at low temperatures. The most common symptom of LED (and laser diode) failure is the gradual lowering of light output and loss of efficiency. With the development of high-power LEDs the devices are subjected to higher junction temperatures and higher current densities than that of the traditional devices. Those problems stress on the material and may cause early light-output degradation. Like other lighting devices, LED performance is temperature dependent. 
         [0003]    LED is a very high-frequency loading up to x-band or higher so that it is very hard to find a power source to come up with this high frequency, which means that serious unmatching between power source and LED exists. Serious unmatching between power source and LED and unproperly to drive LED causes very low electricity-optic-conversion rate, which means the most electrical power contributes to heat causing high LED junction temperature and only very small portion of the electrical power is converted into light. If the matching between power source and LED is improved, then electricity-optic-conversion rate can be improved leading to lower LED junction temperature, brighter light and less electrical power consumed. 
         [0004]    LED is current-driven device, a current is observed when LED emits light, and LED is also a voltage-sensing device, a small change in driving voltage produces large amount of current which could fatally destroy the LED. To properly drive a LED is very important as well. Better matching between power source and LED and more properly driving a LED are revealed in the present invention. 
       SUMMARY OF THE INVENTION 
       [0005]    It&#39;s a first objective to provide a modulated LED which is formed by the coupling of a modulator with a LED. 
         [0006]    It&#39;s a second objective to provide an open circuit device as the modulator with the LED. 
         [0007]    It&#39;s a third objective to provide a circuit by employing the modulated LED to improve the matching between power source and LED results in lowering LED junction temperature and emitting brighter, richer and more natural colors in a more capacitive way. 
         [0008]    It&#39;s a fourth objective to more efficiently drive a LED without needing to change the illuminating structure of the LED. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]      FIG. 1  has shown an open circuit device; 
           [0010]      FIG. 2  has shown a LED driving circuit having an open circuit device; 
           [0011]      FIG. 3   a  has shown an I-V curve of the LED driving circuit shown in  FIG. 2  of which the discharge starting voltage of the open circuit device is smaller than the light-emitting starting voltage of the LED  20 ; 
           [0012]      FIG. 3   b  has shown an I-V curve of the LED driving circuit shown in  FIG. 2  of which the discharge starting voltage of the open circuit device is equal to the light-emitting starting voltage of the LED  20 ; 
           [0013]      FIG. 4  has shown a LED driving circuit having two open circuit devices; 
           [0014]      FIG. 5  has shown a LED driving circuit having an open circuit device; 
           [0015]      FIG. 6  has shown a voltage current characteristic of a typical tunnel diode; 
           [0016]      FIG. 7  has shown a LED driving circuit having a tunnel diode; 
           [0017]      FIG. 8  has shown a LED driving circuit having two tunnel diodes; and 
           [0018]      FIG. 9  has shown an open circuit device having a third terminal disposed between the first terminal and the second terminal of the open circuit device. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    An open circuit device, a tunnel diode, a LED and the Budden Tunneling Factor are respectively introduced in advance. 
       Open Circuit Device 
       [0020]    An open circuit device comprises a first terminal and a second terminal separating the first terminal by an open gap having an open gap width d and an electrical discharge between the first terminal and the second terminal of the open gap can take place and at least one of the first terminal and the second terminal is a discharge electrode of the electrical discharge. The first terminal and the second terminal are not limited in the present invention, for example, they can be conductors or semiconductors. 
         [0021]      FIG. 1  has shown an open circuit device  10  comprising a first terminal  101  and a second terminal  102  separating the first terminal  101  by an open gap  103  having an open gap width d. The open circuit device  10  is driven by a voltage v. By properly adjusting the voltage v across the open gap  103 , the frequency of the voltage v, and the open gap width d, an electrical discharge between the first terminal and the second terminal of the open circuit device  10  can take place and at least one of the first terminal  101  and the second terminal  102  is a discharge electrode of the electrical discharge. The shapes of the first terminal  101  and the second terminal  102  are not limited, for example, the shape can be point or surface. A surface can be viewed as formed by a plurality of points (or called “micro needle array” in the present invention). 
         [0022]    A medium disposed in the open gap  103 , an ionization condition at the open gap  103 , the thermal variation at the open gap  103 , the shapes of the two terminals  101 ,  102  and the materials made of the two terminals  101 ,  102  can also play important roles in the electrical discharge and add more uncertainties to the electrical discharge. The impedance (including resistance, capacitance and inductance) between the first terminal  101  and the second terminal  102  of the open circuit device  10  chaotically randomly varies between zero and infinity and electrical discharge route between the first terminal  101  and the second terminal  102  may chaotically randomly vary as well. 
         [0023]    For example, the medium disposed in the open gap  103  can be a gas such as air or inert gas for isolating the two terminals  101 ,  102  from outside environment against oxidizing. Or, the medium disposed in the open gap  103  can be a third terminal which can be used to receive an input electrical field to change the frequency response of the open circuit device. An open circuit device shown in  FIG. 9 , a third terminal  108  is disposed between a first terminal  101  and a second terminal  102  of the open circuit device. An electrical field applied to the third terminal  108  will change the charges on both the first terminal  101  and the second terminal  102  resulting in changing the frequency response of the open circuit device. The third terminal  108  can neighbor the first terminal  101  and the second terminal  102  as long as an application of an electrical field on the third terminal  108  can vary the impedance between the first terminal  101  and the second terminal  102  resulting in varying the frequency response of the open circuit device. The impedance variation of the open circuit device implies the variation of the frequency response of the open circuit device. 
         [0024]    An ion-release device disposed at the open gap  103  can release or produce ions if excited by an electrical field at the open gap  103 , which will also get involved in the conductivity between the first terminal  101  and the second terminal  102  resulting in playing an important role in the electrical discharge. The ion-release device is a device which can release or produce ions if excited by an energy field such as electrical field, thermal field or magnetic field. The ion-release device is not limited in the present invention, for example, it can be a CNT, C 60  derivatives or graphene which can produce ions under an excitation of an electrical field. 
         [0025]    An initial electrical discharge between the first terminal  101  and the second terminal  102  of the open circuit device  10  starts to take place at a “discharge starting voltage”. An electrical discharge between the first terminal  101  and the second terminal  102  of the open circuit device  10  takes place at a “discharge voltage”. 
         [0026]    The behavior of the electrical discharge of the open circuit device  10  is very complicated, which can be proven by its I-V curve. Making the complicated behavior simple, the complicated behavior of the electrical discharge of the open circuit device  10  includes a periodical PDR (Positively Differential Resistance), NDR (Negatively Differential Resistance) and a constant resistance. When a voltage built at the open gap  103  of the open circuit device  10  reaches the discharge starting voltage of the open gap  103 , then an initial electrical discharge at the open gap  103  starts to take place causing current to flow through the first terminal  101  and the second terminal  102  and the voltage across the open gap  103  drops to present a NDR. The voltage at the open gap  103  will drop to a level unable to keep the initial electrical discharge, then the electrical discharge stops at the open gap  103  causing no current to flow between the first terminal  101  and the second terminal  102  and a voltage at the open circuit device  10  will be built again to present a PDR until reaching to a next discharge voltage for a next electrical discharge. The PDR and the NDR will periodically proceed with its current between zero and a value. For the purpose of convenience, a periodical PDR and NDR can also be called “tunneling” in the present invention. The term “tunneling” is also a more conventional term known by the people skilled in the art. 
         [0027]    The electrical discharge at the open gap  103  of the open circuit device  10  has characterized its chaotically random impedance varying between zero and infinity and its periodical PDR and NDR. Please also notice that a discharge voltage may be different from its previous discharge voltage. Once a voltage across the open gap  103  reaches a discharge starting voltage, an initial electrical discharge starts to take place, and with the voltage going up, the frequency response of the electrical discharge of the open circuit device  10  keeps changing. The electrical discharge at the open gap  103  is not limited, for example, it can be an electrical corona discharge or electrical glowing discharge. 
         [0028]    Some experiments have shown this periodical PDR and NDR (or tunneling) can take place at two slightly touching metals at a very low voltage, even lower to 0.2 volt. The open circuit device includes a loose connection such as touching or slight touching connection between its first terminal and second terminal, in other words, an open gap exists between two touching or slightly touching terminals. For example, two touching or two slightly touching conductors can be viewed as an example of an open circuit device in the present invention. A connection between two terminals without open gap is not an open circuit device, for example, a soldering between two conductors can be viewed to have no open gap so that it is not an open circuit device in the present invention. 
         [0029]    The first terminal and the second terminal of an open circuit device are not limited in the present invention, for example, they can be conductors or semiconductors. 
       Tunnel Diode 
       [0030]    The tunnel diode is known by heavily doping the semiconductor materials used in forming a junction which is called tunnel junction in the present invention. The tunnel diode is a heavily doped junction diode that has a negative resistance at very low voltage in the forward bias direction, due to quantum-mechanical tunneling. The tunnel diode has a region in its voltage current characteristic where the current decreases with increased forward voltage, known as its negative resistance region.  FIG. 6  has shown a voltage current characteristic of a typical tunnel diode where the negative resistance region between V p  and V v  is shown.  FIG. 6  has shown that current starts to decrease at V p  where the negative resistance region begins. The V v  where the negative resistance region begins is called “tunnel starting voltage” for tunnel diode in the present invention. The junction of the tunnel diode is called tunnel junction in the present invention. 
       LED 
       [0031]    LED has a p type region and a n type region separated by a junction or a LED junction. The p type region is dominated by positive electric charges and the n type region is dominated by negative electric charges. When a LED is forward biased (switched on), electrons are able to recombine with electron holes (or holes in short) within the LED, releasing energy in the form of photons. Photon releasing or light emitting is the result of the recombination of electrons and holes in the LED device. 
         [0032]    The recombination of electrons and holes excited by a forward bias implies short circuit of which the voltage across the forward biased LED drops and its resistance becomes lowered to present NDR, which can be viewed as a discharge. With the forward bias removed, the voltage across the junction is re-built up and its resistance becomes higher to present PDR, which can be viewed as a charge. 
         [0033]    A forward voltage exciting a LED to start an initial light-emitting is called light-emitting starting voltage. A chosen sufficient forward voltage to optimally drive a LED to emit light is called working voltage of the LED in the present invention. 
         [0034]    For example, if a forward bias equal to the working voltage is applied to a LED at a frequency and each forward bias is applied at a time when the active region of the LED is recovered to a significant level after its previous recombination, then the LED will be characterized more like as a capacitive loading and has time to rest by this periodical charges and discharges. If a LED is operated more like a capacitive loading, then the LED will more efficiently transform the electricity into an optical energy with more virtual power and less real power, more particularly, it will consume less power, emit brighter light and produce less heat. 
         [0035]    The bandwidth of LED is very high up to x-band or higher depending on its emitting colors so that it is very hard to find a power source to come up with this high frequency. The problem can be solved by the present invention. A LED is known as laser diode if light emitted by the LED is a coherent light characterizing very narrow bandwidth. The term “LED” used in the present invention includes laser diode. 
       The Budden Tunneling Factor 
       [0036]    K. G. Budden considered the wave equation in the form (1) 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                            
                           2 
                         
                          
                         E 
                       
                       
                          
                         
                           x 
                           2 
                         
                       
                     
                     + 
                     
                       
                         ( 
                         
                           
                             β 
                             x 
                           
                           + 
                           
                             
                               β 
                               2 
                             
                             
                               η 
                               2 
                             
                           
                         
                         ) 
                       
                        
                       E 
                     
                   
                   = 
                   0 
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where E stands for an energy wave and x stands for the wave travelling distance of the energy wave E. If the value x is very small, then the term 
         [0000]    
       
         
           
             β 
             x 
           
         
       
     
         [0000]    dominates the wave equation. Budden concluded that when the number of wavelengths (travelling distance) is small, appreciable tunneling occurs through the evanescent region and when the value of x is too large, no tunneling occurs. For the purpose of convenience, the number of wavelengths for the appreciable tunneling governed by the wave equation above is called “Budden distance” in the present invention. 
       Circuit 
       [0037]      FIG. 2  has shown a first circuit which comprises a LED  20 , an open circuit device  21  and a driver  214  electrically connected in series with each other. The LED  20  and the open circuit device  21  are driven by the driver  214 . The LED  20  is simply expressed by a p-type device  201 , a n-type device  202  and a pn junction  203  or a LED junction  203  formed by the contact of the p-type device  201  and the n-type device  202 . The open circuit device  21  comprises a first terminal  211  and a second terminal  212  separating the first terminal  211  by an open gap  213  having an open gap width d. A distance w shown in  FIG. 2  is between the open gap  213  of the open circuit device  21  and the LED junction  203 . The distance w is a characteristic length which can be measured between the first terminal  211  of the open circuit device  21  and the LED junction  203  as shown in  FIG. 2 . 
         [0038]    Assuming the shapes of the first terminal  211  and the second terminal  212  are point (or needles), in other words, a point-to-point electrical discharge between the first terminal  211  and the second terminal  212  of the open circuit device  21 . For the purpose of convenience, assuming the open gap width d of the open gap  213  formed by the first terminal  211  and the second terminal  212  of the open circuit device is fixed. 
         [0039]    The driver  214  having a specific baseband provides a forward bias no higher than a chosen working voltage of the LED  20  across the LED  20  and the open circuit device  21 . The driver  214  periodically not continuously provides power to the LED  20  so that the LED  20  has time to rest and consumes less power as expected. 
         [0040]    The carrier of the open circuit device  21  should be carried on the forward bias between the light-emitting starting voltage, which is a voltage to initially turn on the LED  20  to emit light, and the working voltage, which is a voltage to optimally drive the LED to emit light, so that the discharge starting voltage of the open circuit device  21  should be lower than or equal to (or no higher than) the light-emitting starting voltage of the LED  20  to make sure the electrical discharges of the open circuit device  21  take place at the forward bias between the light-emitting starting voltage and the working voltage of the LED  20 . LED is a current driven device so that significant current can be observed between the light-emitting starting voltage and the working voltage of the LED  20 . 
         [0041]      FIG. 3   a  has shown the I-V curve seen at the open circuit device  21  of the first circuit of  FIG. 2 . A V 1 , V 2  and V 3  shown in  FIG. 3   a  and  FIG. 3   b  are respectively the discharge starting voltage of the open circuit device  21 , the light-emitting starting voltage of the LED  20  and the working voltage of the LED  20 .  FIG. 3   a  has shown V 1  is lower than V 2  and  FIG. 3   b  has shown V 1  is equal to V 2 .  FIG. 3   a  has shown the driver  214  provides a voltage to first reach the discharge starting voltage of the open circuit device  21  to start an initial electrical discharge and the voltage provided by the driver  214  will keep going up to the light-emitting starting voltage of the LED  20  to turn on the LED  20  to emit light and then the voltage from the baseband will keep going up until the working voltage of the LED  20  is reached. 
         [0042]      FIG. 3   a  has shown the frequency response  365  of the open circuit device  21  is carried on the forward bias between the light-emitting starting voltage V 2  and the working voltage V 3  of the LED  20 . The modulation between the light-emitting starting voltage and the working voltage of the LED  20  presents very high frequency currents between zero and a value characterized by the open circuit device as earlier revealed. 
         [0043]    If the distance w between the open gap  213  of the open circuit device  21  and the LED junction  203  shown in  FIG. 2  is large enough, then the high-frequency carrier  355  of the modulation between the light-emitting starting voltage and the working voltage seen in  FIG. 3   a  will very possibly be dissipated in the other energy form such as heat or radiation before being significantly delivered to the LED junction  203  so that the distance w between the open gap  213  of the open circuit device  21  and the LED junction  203  is critical. 
         [0044]    A modulated power waveform is obtained by the modulation of the waveform of the open circuit device  21  and the waveform of the driver  214 , and a bandwidth of the modulated power waveform is the multiplication of the bandwidth of the open circuit device  21  and the bandwidth of the driver  214 , and the bandwidth of the modulated power waveform should be high enough to cover the bandwidth of the LED  20  for increasing matching chances between the bandwidth of the modulated power waveform and the bandwidth of the LED  20 . 
         [0045]    To improve the matching between the modulated power waveform and the impedance of the LED  20  are (1) the distance between the open gap of the open circuit device and the LED junction is within a Budden distance associated with the modulated power waveform so that appreciable tunneling occurs at the LED junction and (2) the bandwidth of the modulated power waveform should be high enough to cover the bandwidth of the LED  20  for increasing the matching chances between them. If the matching between the modulated power waveform and the waveform of the LED  20  is improved, then the LED  20  will benefit lower junction temperature and emit brighter light in a more capacitive way. 
         [0046]    The high-frequency modulated power waveform can be viewed as propagating energy wave. The modulated power waveform can be viewed as E in the wave equation and the energy of the modulated power waveform should be delivered to and responded by the LED junction  203  so that the distance between the open gap  213  of the open circuit device  21  and the LED junction  203  is critical as indicated earlier. The distance w between the open gap  213  of the open circuit device  21  and the LED junction  203  shown in  FIG. 2  should be within a Budden distance associated with the modulated power waveform so that the appreciable tunneling excited by the modulated power waveform takes place at the LED junction  203 . The open circuit device  21  functions as a modulator coupling in very close distance with the main loading LED  20  to deliver high frequency current tunneling into the LED junction  203 . 
         [0047]    The tunneling taking place in the LED junction  203  by the modulated power waveform contains very high-frequency currents which swing between zero and a non-zero value. Zero current is the result of no electrical discharge between the two terminals  201 ,  202  of the open circuit device  21  and stands for no recombination of electrons and holes to emit no light for the LED to rest. Current with the non-zero value stands for a significant recombination of electrons and holes to emit light. Obviously, the light-emitting of the LED is dominated by the tunneling excited by the modulated power waveform which capacitively drives the LED having advantages as revealed earlier. 
         [0048]    The smaller distance w is, the larger tunneling takes place in LED junction  203 , in other words, the modulated power waveform delivers the most power within its first wavelength propagation or 0≦w≦1 wavelength of the modulated power waveform or 0≦w≦1 wavelength of the LED junction  203 . w=0 means that the open gap  213  of the open circuit device  21  is right located at the LED junction  203 . 
         [0049]    The bandwidth of the modulated power waveform is designed to match the known bandwidth of the LED, in other words, the bandwidth of the modulated power waveform is decided by the bandwidth of the LED  20  and the bandwidth of the LED  20  is known so that the wavelength of the modulated power waveform can also be expressed in term of the wavelength of the LED  20  and the Budden distance associated with the modulated power waveform can be expressed in term of the known frequency response of the LED junction because frequency is inversely proportional to wavelength. 
         [0050]    A thermal generated in the LED junction  203  of the LED  20  can be propagated to the nearby open circuit device  21  to further increase the uncertainty to its electrical discharge, for example, the geometric shapes and the material properties of the first and second terminals  211 ,  212  of the open circuit device  21  might be varied to the thermal causing the behavior of the electrical discharge of the open circuit device to be more unpredictable. For example, its frequency responses, the discharging routes between its two terminals  211 ,  212  and discharge voltage randomly vary in a more unpredictable way resulting in a more complicated resistance patterns between the first terminal  211  and the second terminal  212  of the open circuit device  21 . 
         [0051]    The tunneling excited by the modulated power waveform contains a lot different high-frequency currents to excite different points in the LED junction  203  to emit lights and the frequency responses of two or more light-emitting points in the LED junction  203  can correlate with each other to produce more frequency responses or optical resonances resulting in emitting brighter, richer and broader bandwidth color in a more capacitive way. The bandwidth of the driver  214  is adjustable for dimming light up or down. 
         [0052]    LED has two sides by each of which can be disposed an open circuit device.  FIG. 4  has shown a second circuit that comprises a first open circuit device  41 , a second open circuit device  42  and a driver  414  and a LED  40  electrically connected in series with each other of which the LED  40  sits between the first open circuit device  41  and the second open circuit device  42 . The first open circuit device  41  has a first open gap  413  with a first open gap width d 1  and the second open circuit  42  has a second open gap  423  with a second open gap d 2 . The LED  40  has a LED junction  403 . 
         [0053]    A modulated power waveform is formed by the modulation of the waveform of the first open circuit device  41 , the waveform of the second open circuit devices  42  and the waveform of the driver  414  and a bandwidth of the modulated power waveform is the multiplication of the bandwidths respectively of the two open circuits  41 ,  42  and the bandwidth of the driver  414  so that the bandwidth of the modulated power waveform can be a lot higher than that of the first circuit with single open circuit device. 
         [0054]      FIG. 4  has shown that a first distance w 1  is the distance between the first open gap  413  and the LED junction  403  and a second distance w 2  is the distance between the second open gap  423  and the LED junction  403 . Each of the w 1  and w 2  should be within a Budden distance associated the modulated power waveform so that the appreciable tunnelings excited by the modulated power waveform takes place at the LED junction  403 . 
         [0055]    The modulated power waveform delivers the most power within its first wavelength propagation or 0≦w 1 , w 2 ≦1 wavelength of the modulated power waveform or 0≦w 1 , w 2 ≦1 wavelength of the LED junction  403 . w 1 =0 means that the first open gap  413  of the first open circuit device  41  is right located at the LED junction  403 . w 2 =0 means that the second open gap  423  of the second open circuit device  42  is right located at the LED junction  403 . The bandwidth of the driver  414  is adjustable for dimming light up or down. 
         [0056]    The open circuit in the first circuit and the second circuit respectively of  FIG. 2  and  FIG. 4  has also advantaged that once electrons jumping from a first side to a second side over its open gap the electrons carrying the frequency response of the loading (the LED junction) will not reversely jump back from the second side to the first side over its open gap to the driver, which eliminates the noise from the high-frequency loading (the LED junction  203 ) to cause interference to the power source (the driver  214 ). 
         [0057]    As revealed earlier, the shapes of the first terminal and the second terminal of the open circuit can be surfaces which can be viewed as constructed by a plurality of points or a micro-needle array, in other words, a surface-to-surface discharge can be viewed as micro-needle-array-to-micro-needle-array discharges. A surface-to-surface discharge or a micro-needle-array-to-micro-needle-array discharges allows bigger current discharge (bigger power discharge). 
         [0058]      FIG. 5  has shown both a first terminal  521  and a second terminal  522  of an open circuit device  52  in surface shape and an open gap  523  between the first terminal  521  and the second terminal  522  of the open circuit device  52  is seen. A w 6  is the distance between the open gap  523  of the open circuit device  52  and a LED junction  503 . 
         [0059]    Each of the open circuit device  21  shown in  FIG. 2  and  FIG. 4  can be respectively substituted by a tunnel diode. The open circuit device  21  of  FIG. 2  is substituted by a tunnel diode  71 , which is shown in  FIG. 7 . The tunnel diode  71  has a tunnel junction  713  and a distance w 3  is between the tunnel junction  713  and the LED junction  203  and the w 3  is smaller than its the Budden distance associated with its modulated power waveform. 
         [0060]    The first open circuit device  41  and the second open circuit device  42  of  FIG. 4  are respectively substituted by a first tunnel diode  81  and a second tunnel diode  82 , which is shown in  FIG. 8 . The first tunnel diode  81  has a first tunnel junction  813  and the second tunnel diode  82  has a second tunnel junction  823 . 
         [0061]    A distance w 4  is between the first tunnel junction  813  and the LED junction  403  and a distance w 5  is between the second tunnel junction  823  and the LED junction  403 . The w 4  and w 5  are smaller than a Budden distance associated with its modulated power waveform. 
         [0062]    In nowadays technology, the bandwidth of the tunnel diode is narrow compared to that of the open circuit device and the tunnel starting voltage of the tunnel diode is not as low as that of the open circuit device. The LED in the invention is not limited and the color emitted by the LED is not limited, for example, the “LED” used in the present invention includes laser diode. The present invention has characterized to improve the efficiency of LED without needing to change the illuminating structure of the LED.