LED light module and series connected light modules

Abstract

A lighting module with improved reliability including a pair of LEDs connected in parallel and with the same polarity and a method for making the said light module are disclosed. The parallel LEDs with the same polarity will increase the reliability of the light module and make it suitable for use in light strings where a relatively large number of such light modules are connected in series and where the failure of one such light module will cause the failure of the entire light string. A light string made of such light modules and a method for making the light string are also disclosed.

1. An apparatus, comprising:
 a plurality of  light module, modules connected in series to form at least a portion of a light string that is driven by an alternating power source, said light modules comprising:
 a first light emitting diode having a first set of electrical characteristics comprising a first forward voltage drop; and 
 a second light emitting diode connected directly to said first light emitting diode in parallel such that said first light emitting diode and said second light emitting diode have the same polarity, said second light emitting diode having selected to have a second set of electrical characteristics comprising a second forward voltage drop that are different from said first set of electrical characteristics, such that said first light emitting diode carries substantially all of the current that is conducted through said light module, while said second light emitting diode remains unused until said first light emitting diode fails to conduct said current, wherein each of said first light emitting diode and said second light emitting diode have a total current rating sufficient to carry all of said current conducted through said light module. 
 
 
     
     
       2. An apparatus as claimed in  claim 1 , comprising:
 a plurality of light modules that are connected in series to form at least a portion of a light string that is driven by an alternating power source, said light modules comprising:
 a first light emitting diode having a first set of electrical characteristics comprising a first forward voltage drop; and 
 a second light emitting diode connected directly to said first light emitting diode in parallel such that said first light emitting diode and said second light emitting diode have the same polarity, said second light emitting diode having a second set of electrical characteristics, comprising a second forward voltage drop, that are selected to be substantially similar to said first set of electrical characteristics, comprising said first voltage drop, such that said first light emitting diode and said second light emitting diode carry a substantially equal amount of the current that is conducted through said light module, wherein at least one of each of said first light emitting diode and said second light emitting diode has have a maximum total current rating sufficient to carry all of said current conducted through said light module but and are not selected to have different electrical characteristics. 
 
 
     
     
       3. An apparatus as claimed in  claim 2 , further comprising a light-diffuser covering said first and said second light emitting diodes. 
     
     
       4. An apparatus as claimed in  claim 2 , wherein said light module further comprises:
 a third light emitting diode that is connected to said first and said second light emitting diodes, in parallel, but with opposite polarity; and 
 a fourth light emitting diode that is connected to said first and said second light emitting diodes, in parallel, but with opposite polarity. 
 
     
     
       5. An apparatus as claimed in  claim 2 , wherein said first and said second light emitting diodes have substantially the same forward voltage drop over the operating range of said light module. 
     
     
       6. An apparatus as claimed in  claim 5 , further comprising a heat sink thermally connected to both said first and said second light emitting diodes. 
     
     
       7. An apparatus as claimed in  claim 1 , further comprising a plurality of additional light modules as claimed in  claim 1 , connected together in series and connected to said light module in series. 
     
     
       8. An apparatus as claimed in claim  7  1, wherein the number of said plurality of additional light modules and said light module that are connected together in series is selected such that the sum of the minimum operating voltage of each of said plurality of additional light modules and said light modules is less than or equal to the voltage available to supply said apparatus. 
     
     
       9. An apparatus as claimed in  claim 8 , wherein the minimum operating voltage of a light module is the greater of the minimum operating voltage of said first light emitting diode and the minimum operating voltage of said second light emitting diode. 
     
     
       10. An apparatus as claimed in  claim 8 , wherein said number of light modules that are connected together in series is selected such that the sum of the maximum operating voltage for each of the light modules is greater than or equal to said voltage available to supply said apparatus. 
     
     
       11. An apparatus as claimed in  claim 10 , wherein the maximum operating voltage of a light module is the lesser of the maximum operating voltage of said first light emitting diode and the maximum operating voltage of said second light emitting diode. 
     
     
       12. An apparatus as claimed in  claim 10 , further comprising means for limiting said current flowing through to light module. 
     
     
       13. An apparatus as claimed in  claim 12 , wherein said means for limiting current comprises a resistor connected in series with said light module. 
     
     
       14. An apparatus, comprising:
 a plurality of light module, modules that form at least a portion of a light string that is driven by an alternating power source, said light modules comprising:
 a first polarized photon-emitting semiconductor device having a first set of electrical characteristics comprising a first forward voltage drop; and 
 a second photon-emitting semiconductor device connected directly to said first photon-emitting semiconductor device in parallel such that said first polarized photon-emitting semiconductor device and said second polarized photon-emitting semi-conductor device have the same polarity, said second polarized photon-emitting semiconductor having a second set of electrical characteristics comprising a second forward voltage drop that are different from said first set of electrical characteristics, such that said first polarized photon-emitting semiconductor device carries all of the current that is conducted through said light module, while said second polarized photon-emitting semiconductor device remains unused until said first polarized photon-emitting semiconductor device fails to conduct said current, wherein each of said first polarized photon-emitting semiconductor device and said second photon-emitting semiconductor device have a total current rating sufficient to carry all of said current conducted through said light module. 
 
 
     
     
       15. An apparatus as claimed in  claim 14 , wherein at least one of said first photon-emitting semiconductor device and said second photon-emitting semiconductor device has a maximum total current rating sufficient to carry all current conducted through said light nodule, but are not selected to have different electrical characteristics. 
     
     
       16. An apparatus as claimed in claim  15  14, wherein said first and said second photon-emitting semiconductor device have substantially the same forward voltage drop over the operating range of said light module. 
     
     
       17. A method of forming at least a portion of a light string from a plurality of light module modules that are connected together in series, comprising:
 providing a first light emitting diode that has a first set of electrical characteristics comprising a first forward voltage drop; and 
 connecting a second light emitting diode directly to said first light emitting diode in parallel to form said light module, such that said first light emitting diode and said second light emitting diode have the same polarity, said second light emitting diode having a second set of electrical characteristics comprising a second forward voltage drop that are different from said first set of electrical characteristics, such that said first light emitting diode carries substantially all of the current that is conducted through said light module, while said second light emitting diode remains unused until said first light emitting diode fails to conduct said current, wherein each of said first light emitting diode and said second light emitting diode have a total current rating sufficient to carry all of said current conducted through said light module. 
 
     
     
       18. The method of  claim 17  wherein at least one of said first light emitting diode and said second light emitting diode have a maximum total current rating sufficient to carry all current conducted through said module, but are not selected to have different electrical characteristics.