Single LED string lighting
View Patent ↗A solid state lighting unit constituted of: a control circuitry; a single string of light emitting diodes, the single string constituted of a plurality of sections each comprising a plurality of light emitting diodes; and a plurality of bypass paths each responsive to the control circuitry, each of the plurality of bypass paths arranged to provide bypass to a particular one of the plurality of sections, wherein the control circuitry is operative to identify an open circuit condition of a particular one of the plurality of sections, and activate the bypass path arranged to bypass the open circuit section, thereby providing light through sections not exhibiting an open circuit condition.
1. A solid state lighting unit comprising:
a control circuitry;
a single string of light emitting diodes, said single string constituted of a plurality of sections each comprising a plurality of light emitting diodes;
a plurality of bypass paths each responsive to said control circuitry, each of said plurality of bypass paths arranged to provide bypass to a particular one of said plurality of sections; and
a boost converter, said single string of light emitting diodes arranged to receive the output of said boost converter,
wherein said boost converter comprises:
an inductor;
a first electronically controlled switch responsive to said control circuitry and arranged to draw current through said inductor when said first electronically controlled switch is closed; and
a first diode, a first end of said first diode coupled to said inductor and said first electronically controlled switch, said first diode arranged to pass current from said inductor when said first electronically controlled switch is open,
wherein said control circuitry is operative to identify an open circuit condition of a particular one of said plurality of sections, and activate said bypass path arranged to bypass said open circuit section, thereby providing light through sections not exhibiting an open circuit condition.
2. A solid stage lighting unit according to claim 1 , wherein said single string of light emitting diodes is arranged such that a substantially uniform illumination is provided in the event of said open circuit condition of said particular one of said plurality of sections.
3. A solid state lighting unit according to claim 1 , further comprising a current sensor in series with said single string of light emitting diodes, said control circuitry arranged to control said boost converter responsive to a current flow through said single string of light emitting diodes sensed by said current sensor.
4. A solid state lighting unit according to claim 1 , further comprising a second electronically controlled switch arranged in series with said single string of light emitting diodes and responsive to an output of said control circuitry, said second electronically controlled switch enabling current flow through said single string of light emitting diodes when closed and blocking the flow of current through said single string of light emitting diodes when open.
5. A solid state lighting unit according to claim 1 , wherein said inductor is constituted of a two-winding coupled inductor, and wherein a primary winding of said two-winding coupled inductor is connected to said first electronically controlled switch, and
wherein said boost converter further comprises a second diode whose first end is coupled to a first end of a secondary winding of said two-winding coupled inductor; and
wherein a second end of said first diode is connected to a second end of said secondary winding, and wherein said single string of light emitting diodes arranged to receive the output of said boost converter is coupled to the second end of said second diode.
6. A solid state lighting unit according to claim 5 , further comprising a first capacitor and a second capacitor, a first end of said first capacitor connected to the second end of said first diode, a second end of said first capacitor connected to an electrical common point, said second capacitor connected between the first end of said first capacitor and the second end of said second diode.
7. A solid state lighting unit according to claim 1 , further comprising:
a second diode;
a first capacitor; and
a second capacitor,
wherein said inductor is constituted of a two-winding coupled inductor, and wherein a first end of the primary winding of said two-winding coupled inductor is coupled to said first electronically controlled switch, and wherein the anode of said first diode is coupled to said first end of said primary winding and the cathode of said first diode is coupled to a first end of said secondary winding of said two-winding coupled inductor, and wherein the anode of said second diode is connected to a second end of said secondary winding of said two-winding coupled inductor, and wherein a first end of said first capacitor is coupled to the cathode of said first diode and a second end of said first capacitor is coupled to a electrical common point, and wherein said second capacitor is coupled between the cathode of said first diode and the cathode of said second diode, and
wherein said single string of light emitting diodes is coupled to the cathode of said second diode thereby receiving the output of said boost converter.
8. A solid state lighting unit according to claim 1 , wherein said boost converter provides a voltage in excess of 80 volts DC.
9. A solid state lighting unit according to claim 1 , wherein said single string of light emitting diodes is arranged as a backlight for a liquid crystal display exhibiting a minimum diagonal dimension of 25 centimeters.
10. A solid state lighting unit according to claim 9 , wherein said single string of light emitting diodes are constituted of white light emitting diodes.