Abstract:
A light-emitting system comprises: a first power input terminal and a second power input terminal; an insulating substrate; a first light-emitting-diode string formed on the insulating substrate comprising at least three light-emitting diodes placed sequentially in a first direction to allow a current flow through the at least three light-emitting diodes of the first light-emitting-diode string generally in the first direction; a second light-emitting-diode string formed on the insulating substrate comprising at least three light-emitting diodes placed sequentially in a second direction to allow a current flow through the at least three light-emitting diodes of the second light-emitting-diode string generally in the second direction; a third light-emitting-diode string comprising at least three light-emitting diodes placed sequentially in a third direction to allow a current flow through the at least three light-emitting diodes of the third light-emitting-diode string generally in the third direction.

Description:
PRIORITY 
     This application claims the benefit of priority of and is a continuation of U.S. application Ser. No. 12/246,786, filed Oct. 7, 2008 now U.S. Pat. No. 8,704,241, which is a continuation-in-part application of U.S. application Ser. No. 11/245,255, filed Oct. 7, 2005, now issued as U.S. Pat. No. 7,474,681, and U.S. application Ser. No. 11/609,538, filed Dec. 12, 2006 now U.S. Pat. No. 8,487,321. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to light-emitting systems. 
     BACKGROUND 
     Light-emitting diodes (LEDs) are diodes that emit light when an electric current is supplied to the p-n junctions of the diodes. Compared to traditional bulbs, light-emitting diodes may provide one or more benefits, such as durability, longevity, portability, low power consumption, absence of harmful substances, such as mercury, etc. The application of LEDs may include typical illumination, traffic signal lights, vehicles, flash lights, back-light modules for display devices, projectors, outdoor displays, etc. 
     Many light-emitting systems using light-emitting devices such as light-emitting diodes are designed for DC (direct-current) applications. Therefore, it may be desirable to have light-emitting systems that may be operated with AC currents, DC currents, or currents that may flow in either direction into light-emitting systems. 
     BRIEF SUMMARY 
     In one exemplary embodiment, the present disclosure is directed to a light-emitting system. The system may include a first power input terminal and a second power input terminal for receiving an external power input to the light-emitting system; a first light-emitting-diode string comprising at least three light-emitting diodes placed sequentially in a first direction to allow a current flow through the at least three light-emitting diodes of the first light-emitting-diode string generally in the first direction; and a second light-emitting-diode string comprising at least three light-emitting diodes placed sequentially in a second direction to allow a current flow through the at least three light-emitting diodes of the second light-emitting-diode string generally in the second direction, The first light-emitting-diode string and the second light-emitting-diode string may be serially coupled between the first power input terminal and the second power input terminal, and the first direction may be substantially vertical to the second direction. 
     In another exemplary embodiment, the present disclosure may be directed to a light-emitting system. The system may include a first power input terminal and a second power input terminal for receiving an external power input to the light-emitting system; a first light-emitting-diode string comprising at least three light-emitting diodes arranged in a first direction to allow a current flow through the at least three light-emitting diodes of the first light-emitting-diode string generally in the first direction; and a second light-emitting-diode string comprising at least three light-emitting diodes arranged in a second direction to allow a current flow through the at least three light-emitting diodes of the second light-emitting-diode string generally in the second direction. The first light-emitting-diode string and the second light-emitting-diode string may be serially coupled between the first power input terminal and the second power input terminal, and the first light-emitting-diode string and the second light-emitting-diode string may be arranged in non-parallel directions. 
     In another exemplary embodiment, the light-emitting system includes a first power input terminal and a second power input terminal for receiving an external power input to the light-emitting system; an insulating substrate; a first light-emitting-diode string formed on the insulating substrate comprising at least three light-emitting diodes placed sequentially in a first direction to allow a current flow through the at least three light-emitting diodes of the first light-emitting-diode string generally in the first direction; a second light-emitting-diode string formed on the insulating substrate comprising at least three light-emitting diodes placed sequentially in a second direction to allow a current flow through the at least three light-emitting diodes of the second light-emitting-diode string generally in the second direction; a third light-emitting-diode string comprising at least three light-emitting diodes placed sequentially in a third direction to allow a current flow through the at least three light-emitting diodes of the third light-emitting-diode string generally in the third direction; wherein the first light-emitting-diode string, the second light-emitting-diode string and the third light-emitting-diode string are serially coupled between the first power input terminal and the second power input terminal, and the first direction is substantially perpendicular to the second direction, wherein the light-emitting diodes in the same string are separated from one another and electrically connected to one another through a plurality of conductors, and the second light-emitting-diode string and the third light-emitting-diode string are arranged in a non-parallel manner. 
     In another exemplary embodiment, the light-emitting system includes an insulating substrate; a first power input terminal and a second power input terminal for receiving an external power input to the light-emitting system formed on the insulating substrate; a first light-emitting-diode string formed on the insulating substrate comprising at least three light-emitting diodes arranged in a first direction to allow a current flow through the at least three light-emitting diodes of the first light-emitting-diode string generally in the first direction; and a second light-emitting-diode string formed on the insulating substrate comprising at least three light-emitting diodes arranged in a second direction to allow a current flow through the at least three light-emitting diodes of the second light-emitting-diode string generally in the second direction, a third light-emitting-diode string comprising at least three light-emitting diodes arranged in a third direction to allow a current flow through the at least three light-emitting diodes of the first light-emitting-diode string generally in the third direction, wherein the first light-emitting-diode string, the second light-emitting-diode string and the third light-emitting-diode string are serially coupled between the first power input terminal and the second power input terminal, and the first light-emitting-diode string and the second light-emitting-diode string are arranged in non-parallel directions, and the second light-emitting-diode string and the third light-emitting-diode string are arranged in non-parallel directions, wherein the light-emitting diodes in the same string are separated from one another and electrically connected to one another through a plurality of conductors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic cross-sectional view of a light-emitting device, consistent with certain disclosed embodiments; 
         FIG. 1B  is an enlarged schematic cross-sectional view of the light-emitting device illustrated in  FIG. 1A , consistent with certain disclosed embodiments; 
         FIGS. 2A and 2B  are schematic diagrams illustrating an exemplary AC light-emitting device with different emitting states, consistent with certain disclosed embodiments; 
         FIGS. 3A and 3B  illustrate an exemplary equivalent circuitry for the device illustrated in  FIGS. 2A and 2B , consistent with certain disclosed embodiments; 
         FIG. 4  is a top or bottom view diagram illustrating AC light-emitting devices on a chip, consistent with certain disclosed embodiments; 
         FIGS. 5A and 5B  are schematic diagrams illustrating an exemplary AC light-emitting device with different emitting states, consistent with certain disclosed embodiments; 
         FIGS. 6A and 6B  illustrate an exemplary equivalent circuitry for the device illustrated in  FIGS. 5A and 5B , consistent with certain disclosed embodiments; 
         FIG. 7  is an exemplary equivalent circuitry for a tri-layer, AC light-emitting device, consistent with certain disclosed embodiments; 
         FIG. 8  illustrates an exemplary circuit diagram of a light-emitting system, consistent with certain disclosed embodiments; 
         FIG. 8A  illustrates an exemplary circuit diagram of a light-emitting system, consistent with certain disclosed embodiments; 
         FIGS. 9A and 9B  illustrate schematic diagrams of exemplary implementations of the light-emitting system illustrated in  FIG. 8  or  8 A, consistent with certain disclosed embodiments; 
         FIGS. 10A and 10B  illustrate schematic diagrams of exemplary implementations of the light-emitting system illustrated in  FIG. 8  or  8 A, consistent with certain disclosed embodiments; 
         FIG. 11A  illustrates an exemplary circuit diagram of a light-emitting system, consistent with certain disclosed embodiments; 
         FIG. 11B  illustrates an example of a flip-chip light-emitting system coupled to an AC input, consistent with certain disclosed embodiments; 
         FIG. 11C  illustrates an exemplary circuit diagram of a light-emitting system, consistent with certain disclosed embodiments; 
         FIG. 12A  illustrates an exemplary circuit diagram of a serial coupling having forwardly-coupled Zener and light-emitting micro diodes, consistent with certain disclosed embodiments; 
         FIG. 12B  illustrates an exemplary circuit diagram of a parallel coupling having reversely-coupled Zener and light-emitting micro diodes, consistent with certain disclosed embodiments; 
         FIG. 13A  illustrates an exemplary circuit diagram of a serial coupling having oppositely-coupled Zener diodes and a light-emitting micro diode, consistent with certain disclosed embodiments; 
         FIG. 13B  illustrates an exemplary circuit diagram of a parallel coupling having oppositely-coupled Zener diodes and a light-emitting micro diode, consistent with certain disclosed embodiments; and 
         FIG. 14  illustrates an exemplary circuit diagram of a light-emitting system with Zener diodes, consistent with certain disclosed embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Light-emitting systems may be designed in various forms or for various applications. For example, a light-emitting system may be made on a chip or with a combination of two or more chips. A light-emitting system may be configured to generate white light or light in other colors and may be configured to accept AC power, which may drive the system to emit light during both positive and negative cycles. In other words, the system may emit light full-time or continuously from a viewer&#39;s standpoint, regardless of the direction of input currents. 
       FIG. 8A , a drawing similar to  FIG. 8  discussed below but with different element designations, illustrates an equivalent-circuit representation of a light-emitting system, which is similar to the system in  FIG. 8 . Referring to  FIG. 8A , light-emitting system  800 A may include first power input terminal I 1  and second power input terminal I 2  for receiving an external power input, which may be an AC power input as illustrated, a DC input, or a mixture of both. Light-emitting system  800 A may also include five rectifying devices RD 1  through RD 5 . First rectifying device RD 1  may be coupled between first power input terminal I 1  and first intermediate contact O 1 . First rectifying device RD 1  may be configured to allow a current flow from first power input terminal I 1  to first intermediate contact O 1 . The second rectifying device RD 2  may be coupled between second power input terminal I 2  and first intermediate contact O 1 . Second rectifying device RD 2  may be configured to allow a current flow from second power input terminal I 2  to first intermediate contact O 1 . Third rectifying device RD 3  may be coupled between second intermediate contact O 2  and second power input terminal I 2 . Third rectifying device RD 3  may be configured to allow a current flow from second intermediate contact O 2  to second power input terminal I 2 . Fourth rectifying device RD 4  may be coupled between second intermediate contact O 2  and first power input terminal I 1 . Fourth rectifying device RD 4  may be configured to allow a current flow from second intermediate contact O 2  to first power input terminal I 1 . Fifth rectifying device RD 5  may be coupled between first intermediate contact O 1  and second intermediate contact O 2 , and may be configured to allow a current flow from first intermediate contact O 1  to second intermediate contact O 2  and to emit light in response to the current. 
     As shown in  FIG. 8A , the five rectifying devices RD 1 -RD 5  may be arranged in a bridge rectifier circuit. When an alternating-current (AC) input is received from power input terminals I 1  and I 2 , the AC input current may flow through RD 1 , RD 5 , and RD 3  in one half cycle (of positive polarity) and may flow through RD 2 , RD 5 , and RD 4  in the other half cycle (of negative polarity). As an example, a first input current flowing from first power input terminal I 1  to second power input terminal I 2  may flow through first, fifth, and third rectifying devices RD 1 , RD 5 , and RD 3 . A second input current flowing from second power input terminal I 2  to first power input terminal I 1  may flow through second, fifth, and fourth rectifying devices RD 2 , RD 5 , and RD 4  allowing light-emitting system  800 A to emit light in response to both the first and second input currents. 
     In one embodiment, the fifth rectifying device may include one or more light-emitting micro diodes. In other words, the bridge rectifier circuit may function to rectify the AC input into a direct current going through RD 5 , so that the current may flow through the light-emitting micro diode(s) and allow the light-emitting micro diode(s) in RD 5  to emit light during both positive and negative cycles of the AC input. 
     In one embodiment, one or more of first, second, third, and fourth rectifying devices RD 1 -RD 4  may include one or more light-emitting micro diodes each having one or more active layers. In some embodiments, fifth rectifying device RD 5  may include two or more light-emitting micro diodes coupled in series, parallel, or in a combination thereof. In some examples, one or more of first, second, third, and fourth rectifying devices RD 1 -RD 4  may include one or more Schottky diodes (Schottky barrier diodes) or a combination of one or more Schottky diodes and one or more light-emitting micro diodes. The Schottky diode(s) may provide different rectifying or current characteristics in some applications. Different rectifying devices may have different numbers of light-emitting diodes or Schottky diodes and the numbers of light-emitting diodes or Schottky diodes of first, second, third, and fourth rectifying devices RD 1 -RD 4  may be the same or not. 
     In some embodiments, the total number of light-emitting micro diode(s) in first, second, third, and fourth rectifying devices RD 1 -RD 4  may be approximately 1 to 2.5 times of the number of light-emitting micro diode(s) in fifth rectifying device RD 5 . In certain embodiments, the ratio may be approximately 1.5 to 2 times. In some embodiments, the effective size of the light-emitting micro diode(s) in one or more of first, second, third, and fourth rectifying devices RD 1 -RD 4  may be approximately 0.5 to 1.5 times of the effective size of the light-emitting micro diode(s) in fifth rectifying device RD 5 . In certain embodiments, the ratio may be approximately 0.8 to 1.2 times. 
     In embodiments where Schottky diodes are used, the total number of the Schottky diode(s) in first, second, third, and fourth rectifying devices RD 1 -RD 4  may be approximately 0.125 to 1 time of the number of light-emitting micro diode(s) in fifth rectifying device RD 5 . In certain embodiments, the ratio may be approximately 0.25 to 0.8 time. Additionally, when Schottky diodes are used, the effective size of the Schottky diode(s) in one or more of first, second, third, and fourth rectifying devices RD 1 -RD 4  may be approximately 0.1 to 0.4 time of the effective size of the light-emitting micro diode(s) in the fifth rectifying device. In certain embodiments, the ratio may be approximately 0.2 to 0.3 time. 
     In some embodiments, one or more of first, second, third, and fourth rectifying devices RD 1 -RD 4  may include one or more reversely-coupled Zener diode(s) for circuit protection. Additionally, light-emitting system  800 A may include one or more capacitors coupled between first and second input terminals I 1  and I 2 . The light-emitting system may be formed on a single substrate. Alternatively, different portions of light-emitting system  800 A may be formed on two or more separate substrates and then combined together. For example, some or all of the rectifying devices may be formed on a second substrate, which is then mounted to a first substrate having some or all of the conductive paths formed thereon to make conductive couplings to those rectifying devices. Other devices or parts, such as Zener diodes or capacitors, if used, can be formed on one of the first substrate and the second substrate. As another example, the rectifying devices or some of their diodes may be formed on two different substrates and combined using flip-chip or wafer-bonding techniques. 
     The light-emitting system illustrated above may be formed on a substrate with a bridge-circuit connection. In one embodiment, the bridge-circuit connection may have four or more circuit branches, such as branches RD 1 -RD 4 , and may be provided over the substrate. Each of the branches may have two terminals. The system may have one or more light-emitting micro diodes coupled between the two terminals of each branch, as illustrated in  FIG. 8A . The bridge circuit connection may be configured to receive an alternating current input from first and second power input terminal I 1  and I 2  to enable at a first group of the light-emitting micro diodes, such as those in branches RD 1 , RD 5 , and RD 3 , to emit light during positive cycles of the alternating current input, and to enable a second group of the light-emitting micro diodes, such as those in branches RD 2 , RD 5 , and RD 4 , to emit light during negative cycles of the alternating current input. 
     In one embodiment, one or more Zener diodes may be provided in one or more of the four branches and be coupled, in a serial coupling, a parallel coupling, or both, with the light-emitting micro diodes in one or more branches. In one embodiment, one or more Schottky diodes may be provided in one or more of the four branches and be coupled, in a serial coupling, a parallel coupling, or both, with the light-emitting micro diodes in one or more branches. In one embodiment, the bridge-circuit connection may have a central branch, such as RD 5 , which may have one or more light-emitting micro diodes. Central branch RD 5  may be coupled between first intermediate contact O 1  between first branch RD 1  and second branch RD 2  and second intermediate contact O 2  between third branch RD 3  and fourth branch RD 4 . Central branch RD 5  may be configured to allow a current flow from first intermediate contact I 1  to second intermediate contact I 2  and to emit light in response to the current flow. 
     Similar to the system illustrated above, certain relationship may exist between the total number or effective area of the light-emitting micro diode(s) in the four branches and the number or effective area of the light-emitting micro diode(s) in the central branch. In some embodiments, one or more branches illustrated in  FIG. 8  may have one or more forwardly- or reversely-coupled Zener diode. Referring to  FIG. 14 , in one embodiment, one or more Zener diodes, such as Zener diode  330 , may be coupled between first power input terminal I 1  and ground. Additionally, one or more Zener diodes, such as Zener diode  340 , may be coupled between second power input terminal I 2  and ground. 
     Referring to  FIG. 12A , one or more Zener diodes, such as Zener diode  310 , may be forwardly coupled, in a series coupling, with one or more light-emitting micro diodes, such as light-emitting micro diode  312 , in one embodiment. Referring to  FIG. 12B , one or more Zener diodes, such as Zener diode  320 , may be reversely coupled, in a parallel coupling, with one or more light-emitting micro diodes, such as light-emitting micro diode  322 , in one embodiment. In some embodiments, when multiple Zener diodes are used, two or more Zener diodes may be oppositely-coupled in series with each other. Referring to  FIG. 13B , Zener diodes  310 A and  310 B may be oppositely-coupled in series with each other and also coupled in series with one or more light-emitting micro diodes, such as light-emitting micro diode  312 , in one embodiment. Referring to  FIG. 13B , Zener diodes  320 A and  320 B may be oppositely-coupled in series with each other and also coupled in parallel with one or more light-emitting micro diodes, such as light-emitting micro diode  322 , in one embodiment. 
       FIG. 1A  is a schematic cross-sectional view of light-emitting micro diodes  20   a  and  20   b  on semiconductor substrate  1 . The diodes illustrated may belong to one single AC light-emitting device in this embodiment. In one embodiment, the AC light-emitting device may include substrate  1 , AC micro diode light-emitting module  2  formed on substrate  1 , and conductive structure  3  having conductors  30   a ,  30   b , and  30   c  for providing an electrical connection between micro diodes  20   a  and  20   b . In one embodiment, substrate  1  can either be the base of the chip as mentioned above or an insulating substrate with a material such as A1 2 O 3 , GaAs, GaP, SiC, etc. 
       FIG. 1B  is an enlarged view for illustrating light-emitting module  2  having micro diodes  20   a  and  20   b . In one embodiment, each micro diode  20   a  and  20   b  may include one or more active layers as illustrated. For example, referring to  FIG. 1B , micro diode  20   a  as illustrated has upper active layer  200   a  and lower active layer  201   a . Micro diode  20   b  as illustrated has upper active layer  200   b  and lower active layer  201  b as shown in the  FIG. 1B . The active layers are light-emitting active layers, which may be sandwiched between two neighboring layers, such as a p layer and an n layer for each active layer. In one embodiment, those neighboring p and n layers may be coupled with corresponding electrodes, such as  202   a ,  202   b ,  203   a ,  203   b ,  204   a ,  204   b ,  205   a  and  205   b . By applying a current to active layers  200   a ,  201  a,  200   b  and  201   b  through electrodes  202   a ,  202   b ,  203   a ,  203   b ,  204   a ,  204   b ,  205   a  and  205   b , the active layers may emit light. 
     Exemplary operations of the AC light-emitting device may be illustrated with reference to  FIGS. 2A ,  2 B,  3 A and  3 B.  FIGS. 2A and 2B  illustrate an AC light-emitting device with an AC input at two different emitting states.  FIGS. 3A and 3B  illustrate equivalent circuitry of the AC light-emitting device respectively corresponding to the AC light-emitting device illustrated in  FIGS. 2A and 2B . Referring to  FIGS. 2A and 2B , each active layer, such as upper active layer  200  and lower active layer  201 , may be similar to a light-emitting diode having a p-n (i.e. p-n junction) structure. A conductive structure  3  may be formed to provide a parallel electrical connection between upper active layer  200  and lower active layer  201  of micro diode  20 . All of the upper active layers may be electrically connected in series, as shown in  FIGS. 3A and 3B . Similarly, all of the lower active layers may also be electrically connected in series. 
     With reference to  FIGS. 2A and 3A , during the positive-half cycles of the AC input, the upper active layers (e.g., upper active layer  200 ) of the micro diodes (e.g., micro diode  20 ) are forward biased. As a result, a current flows through the upper active layers (e.g., upper active layer  200 ) of the micro diodes (e.g., micro diode  20 ) to allow them to emit light, as illustrated in  FIG. 3A . Similarly, with reference to  FIGS. 2B and 3B , during the negative-half cycles of an AC input, the lower active layers (e.g., lower active layer  201 ) of the micro diodes (e.g., micro diode  20 ) are forward biased. As a result, a current flows through the lower active layers (e.g., lower active layer  201 ) of the micro diodes (e.g., micro diode  20 ) to allow them to emit light, as illustrated in  FIG. 3B . As illustrated in  FIGS. 3A and 3B , the upper and lower active layers of each micro diode (e.g., upper active layer  200  and the lower active layer  201  of the micro diode  20 ) may be similar to two light-emitting diodes (LEDs) with oppositely-biased directions for receiving the current from either positive or negative half cycles of an AC input. The design may allow an AC light-emitting device to emit light during both the positive and negative half cycles of the AC input to the device and may enable the active layers of micro diodes to take turns in emitting light between the positive and negative half cycles of the AC input. For example, all of the upper active layers may emit light during a positive half cycle of an AC input and all of the lower active layers may emit light during a negative half cycle of the AC input. 
     As shown in  FIG. 4 , when a number of micro diodes (e.g., micro diode  20 ) interlacing with one another are arranged on a chip and receive an AC input, the different areas or different diodes of the light-emitting surface of the chip may take turns emitting light, at a certain frequency, such as 60 Hz. The micro diodes may be arranged to emit light at the same or different wavelengths. That means the micro diodes may generate the same or different colors. A chip having multiple micro diodes may be configured to emit light in different colors at different timings, different areas, or different timings and areas. The various configurations can modify the chip to emit light that is the result of mixed colors, thereby offering numerous variations in colors or other visual effects. For example, micro diodes emitting light at different wavelengths may be configured as having an upper active layer emitting green light and a lower active layer emitting red light. The AC light-emitting device may generate light having a mixed color from mixing green and red lights. Specifically, if green light having a wavelength of 495 to 570 nm (for the upper active layer) is used together with red light having a wavelength 620 to 750 nm (for the lower active layer), the mixed light effect of the upper lower active layers may be similar to the white light of black body radiation. Accordingly, the disclosed device may provide an improved light-emitting device that can emit light during full cycles of an AC input. It may also provide a device that can be adjusted to selectively emit a monochromatic light or mixed colors of light according to the user&#39;s implementations, applications or requirements. Therefore, various embodiments consistent with the present invention may offer advantages over the prior art technique in some applications. 
       FIGS. 5A and 5B  illustrate another application of the AC light-emitting device consistent with the invention, with their corresponding equivalent circuitry illustrated in  FIGS. 6A and 6B . As an example, each active layer (e.g., each of upper active layers  200   c ,  200   d  and lower active layers  201   c ,  201   d ) may be similar a light-emitting diode (LED) having a p-n structure. In the illustrated structure, the upper active layers  200   c  and  200   d  and the lower active layers  201   c  and  201   d  of micro diodes  20   c  and  20   d  are coupled in parallel, and the micro diodes  20   c  and  20   d  are coupled in series through conductive structure  3 . 
       FIG. 5A  and its corresponding equivalent circuitry  FIG. 6A  illustrate the light-emitting status of the AC light-emitting device during the positive half cycles of an AC input. During the positive half cycles of the AC input, certain active layers of adjacent micro diodes  20   c  and  20   d  may be forward biased, such as upper active layer  200   c  of micro diode  20   c  and lower active layer  201   d  of micro diode  20   d . Consequently, the positive half cycle of the AC input as illustrated by the arrow in  FIG. 6A  passes through different active layers of micro diodes  20   c  and  20   d  to activate certain different active layers, such as upper active layer  200   c  of micro diode  20   c  and lower active layer  201   d  of micro diode  20   d , to emit light. Similarly, during the negative half cycles of the AC input as shown in  FIG. 5B  and its corresponding equivalent circuitry in  FIG. 6B , certain active layers of adjacent micro diodes  20   c  and  20   d  may be forward biased, such as the upper active layer  200   d  of micro diode  20   d  and lower active layer  201   c  of micro diode  20   c . The negative half cycle of the AC input, as illustrated by the arrow in  FIG. 6B , passes through different active layers of micro diodes  20   c  and  20   d  to enable certain different active layers, such as upper active layer  200   d  of micro diode  20   d  and lower active layer  201   c  of micro diode  20   c , to emit light. 
     As illustrated the equivalent circuitry in  FIGS. 6A and 6B , the active layers in each micro diode, such as upper active layer  200   c  and lower active layer  201   c  in micro diode  20   c , may be similar to two light-emitting diodes stacked together. The embodiment differs from the embodiment depicted in  FIGS. 2A ,  2 B,  3 A and  3 B in that the different active layers of micro diodes  20   c  and  20   d  take turns emitting light during the positive or negative half cycles of the AC input. A number of micro diodes may be arranged in an interlacing manner on a chip to be driven by an AC power input, so that the light-emitting surface of the chip may emit light at both positive and negative cycles regardless of the direction of an input current. 
     Similarly, micro diodes  20   c  and  20   d  as described above may emit light with the same or different wavelengths to display the same or different colors. In other words, the micro diodes emitting different colors may be configured in numerous ways, such as with variations in emitting timing, region, or both, to generate desired color or visual effects. Additionally, upper active layers  200   c  and  200   d  and lower active layers  201   c  and  201   d  may emit light of different colors at a higher frequency, such as 120 Hz (2 times of 60 Hz). For a frequency exceeding highest human-recognizable frequency of 100 Hz, a more even or soft visual effect of mixing light or colors may be provided. Accordingly, the light-emitting device employed in this embodiment may comply with users&#39; needs to flexibly adjust colors of emitting light and may produce more even or soft visual effects. 
       FIG. 7  illustrates an exemplary equivalent circuitry of an AC light-emitting device with micro diodes having three active layers. When applying a positive half-cycle of an AC input as shown by the arrows, each active layer along the current path will emit light. The same occurs to the active layers that are part of the current path for the current from a negative half-cycle of an AC input. In one embodiment, the three-layer structure is implemented by having a first layer L 1  emit green light, a second layer L 2  emit blue light, and a third layer L 3  emit red light. Green, blue and red lights are three primaries that can be combined to produce white light. 
     Referring to  FIG. 7 , the colors produced during the positive half-cycles of an AC input may appear in the order (following the arrow from left to right) of blue, green, green, red, blue, green, green, red. The colors produced during the negative half cycles of the AC input may also appear in the same order of blue, green, green, red, blue, green, green, red, but the current flows from right to left to activate the other two blue and two red diodes. Those diodes do not activate during the positive half-cycle, but the green diodes do activate and emit light during both the negative and positive half-cycles. The exemplary configuration is based on the fact that the human eye needs more green in order to perceive white. In this embodiment, the AC light-emitting device can be configured to employ and match different colors to achieve an overall desired color effect. As an example, for a three-layer structure to have an effect of producing white light, one may mix green light at a 535 nm wavelength, blue light at a 460 nm wavelength, and red light at a 630 nm wavelength. When three or more active layers are used to mix light, color temperature may be adjusted. In some examples, one or more active layers can be made non-luminous to vary the light mixing for various applications or requirements. 
     Referring to  FIG. 8 , micro diodes can be configured in a bridge rectifier configuration. Each micro diode in the bridge rectifier configuration may have one or more active layers. Each active layer, which is similar to a light emitting diode as discussed above, may be electrically connected. In one embodiment, a light-mixing system may mix colors from multiple diodes or layers. 
     Also, as illustrated in  FIG. 8 , the light-emitting system may have first circuit C 1 , second circuit C 2 , third circuit C 3 , fourth circuit C 4  and fifth circuit C 5 . The colors of the emitted light and the number of active layers (light emitting diodes) may be varied by users depending on their requirements or application. In one embodiment,  10  active layers may be placed in one or more of first circuit C 1 , second circuit C 2 , fourth circuit C 4 , and fifth circuit C 5 , and 22 active layers may be placed in circuit C 3 . In this circuit structure arrangement, the number of the active layers required to sustain a reverse-biased voltage is about half the number of active layers to conduct a forward-biased voltage. Therefore, the number of active layers (light emitting diodes) required to be used in this light emitting system may be reduced. Therefore, if a structure has a plurality of active layers that are subject to a reverse-biased voltage from an AC input, the reverse-biased voltage may be evenly absorbed or distributed to prevent shorting or break-down caused by excessive reverse-biased voltage. In one embodiment, one active layer can sustain about 10-15 volts of reverse-biased voltage. 
     The configuration of second circuit C 2 , third circuit C 3  and fourth circuit C 4  may be the path for the positive half cycle of an AC input illustrated in  FIG. 9A , and the configuration of fifth circuit C 5 , third circuit C 3  and first circuit C 1  may be the path for the negative half cycle of an AC as illustrated in  FIG. 9B . The configuration in one embodiment allows third circuit C 3  to be a current path for both the positive and negative half cycles of an AC input. This may provide the effect of continuous light emitting to viewers. The conductive electrodes or terminals E 1  and E 2  may be connected with an AC input to provide the input to circuits C 1 -C 5 . 
     In one embodiment, because the active layers of the third circuit C 3  can emit light during either the positive or negative half cycles of alternating current, the number of active layers used in other implementations, which only emit light half of the time, can be reduced. For example, the number of active layers used in other techniques may requires 22 layers for each of the positive and the negative half cycles of alternating current, making a total number of 44. In contrast, the embodiment only employs a total number of 22 active layers in third circuit C 3  (or fifth circuit RD 5  in  FIG. 8A ) to achieve the effect of full-timely continuous light emitting. 
     In some embodiments consistent with the present invention, active layers (or micro diodes) may be arranged as a bridge light-emitting system illustrated in  FIG. 8 . The system may be constituted by micro diodes having multiple active layers arranged as a bridge rectifier as illustrated. Multiple bridge rectifiers may be electrically coupled to each other provide a larger light-emitting system. For example, a plurality of bridge rectifiers or bridge light-emitting units may be arranged in a matrix as illustrated in  FIGS. 10A and 10B  in a chip. In one example, the number of active layers in the bridge light-emitting units B 1  may be greater in the central region than that in the peripheral region. At the two diagonal corners of the matrix, two conductive electrodes E 3  and E 4  may be provided for connecting the system with an AC input. 
     The circuit configuration as described above can also be applied to an alternating current light emitting device composed of micro diodes, wherein each micro diode has a single active layer, such as forming one or more bridge rectifiers or bridge light emitting units composed of a plurality of light emitting diodes on a substrate, micro diodes being arranged in a bridge rectifier configuration and being electrically connected to each other through a conductive structure, thereby making the micro diodes to take turns to emit light during the positive and negative half cycles of alternating current. Alternatively, it can include a plurality of bridge light emitting units electrically connected to one another, each bridge light emitting unit being disposed as a part of a matrix, wherein the number of the bridge light emitting units is greater in the central region than in the peripheral region to thereby achieve a full-timely and more even light emitting effect. Additionally, it further includes a step of disposing two conductive electrodes E 3  and E 4  on the two diagonal corners of the matrix, each conductive electrode E 3  and E 4  being serially connected to each bridge light emitting unit to provide a connection of to alternating current. 
     In another embodiment consistent with the present invention, the light-emitting device may include a mounting body or be combined with a mounting substrate. For example, the conductive structure may be formed separately from the light-emitting units on the mounting substrate. Alternatively, the mounting substrate can include a plurality of light-emitting units electrically connected to one another by the conductive structure on the mounting substrate, each light-emitting unit disposed as a part of a matrix to thereby achieve a full-time and even light-emitting effect. Additionally, it may include a step of disposing two conductive electrodes on the two diagonal corners of the matrix, each conductive electrode serially connected to each light-emitting unit (e.g., light-emitting unit  800 ) to provide a connection to an AC input. 
     The visual effect of mixing light may be provided by disposing a plurality of light-emitting micro diodes on circuit C 3  or other circuits, in a parallel or serial connection or a combination of both types of connections. As shown in  FIG. 11A , three groups of light-emitting micro diodes are electrically connected in parallel. For example, the light-emitting micro diodes of groups G 1 , G 2  and G 3  may be arranged on circuits C 30 , C 31  and C 32  respectively. The light-emitting micro diodes of each group may be electrically connected in series as illustrated, in parallel, or in both types of arrangements. In an exemplary embodiment, the light-emitting micro diodes of each group may have the same wavelengths in emitting light. For example, referring to  FIG. 11A , light-emitting micro diodes L 1 , L 2  and L 3  each may have one active layer. Each active layer may emit light at the same wavelength. Alternatively, each active layer may emit light at different wavelengths. The light-emitting micro diodes from different groups may emit light at different wavelengths. For example, Group G 1  may emit green light, group G 2  may emit blue light, and group G 3  may emit red light. In one embodiment, the mixing light may be controlled by adjusting the operating voltages. 
     In one embodiment consistent with the present invention, as shown in  FIG. 11B , a first micro diode F 1  having one active layer may emit red light. A second micro diode F 2  having one active layer may emit green light. The first and second micro diodes combined with a flip-chip or wafer bonding technique and may be electrically connected through conductive electrodes P 1  and P 2 , thus providing a visual effect of mixing light. 
     In another embodiment consistent with the present invention, each light-emitting micro diode on circuit C 3  may have two or more active layers as shown in  FIG. 11C . The active layers of each light-emitting micro diode may emit light having the same or different wavelengths. A plurality of light-emitting micro diodes may be serially and electrically connected on circuits C 33  and C 34  respectively. Light-emitting micro diodes in circuits C 33  and C 34  may be electrically connected in parallel. Accordingly, the visual effect of emitting mixed light is achieved. The number of active layers, the number of micro diodes, and variations in serial and parallel connections of the active layers and micro diodes may be implemented in either circuits C 1 -C 5  in  FIG. 8  or rectifying devices RD 1 -RD 5  in  FIG. 8A . The variations, in combination with the variations in the light-emitting colors of the diodes, may accommodate different applications, different operational voltages, different visual or color effects, and other characteristics desired under different circumstances. 
     The active layers (or LEDs) may be implemented in switch circuits, signaling circuits, or other circuits without adding external load. A plurality of active layers may be configured in a parallel connection, a serial connection, or both for various lighting applications. Moreover, the devices or systems disclosed in various embodiments may be implemented in LCD (liquid crystal display) backlight devices, such as example illustrated in U.S. Publication Numbers 20050001537, 20040246696, and 20040333583. The active layers can also be implemented with a variety of manufacturing processes, such as the 5φ LED conducting wire stand glue-irrigating packaging process; the Super Flux conducting wire stand glue-irrigating packaging process; the Flip-Chip, ceramics and aluminum substrate manufacturing processes; the PPA point-gluing, injection packaging process; the metal shell packaging process, etc. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the light-emitting systems and devices. It is intended that the embodiments described be considered as exemplary only, with the true scope of the embodiments being indicated by the following claims and their equivalents.