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US 8,427,071 B2Granted
Light emitting diode driving device with a simple structure and an enhanced efficiency
AssigneeNational Cheng Kung University
InventorsTsorng-Juu Liang, Wei-Ching Tseng, Jiann-Fuh Chen
Life of this patent
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Abstract
An LED driving device includes: an LED circuit having an input side for receiving a driving current corresponding to an AC input voltage from an external power source when the magnitude of a driving voltage across the input side is greater than a predetermined value; and a clamp circuit coupled between the input side of the LED circuit and the external power source, and permitting the driving current to pass through for clamping the magnitude of the driving current to a predetermined current level and for clamping the magnitude of the driving voltage to a predetermined voltage level.
Claims17
A light emitting diode (LED) driving device comprising:
- an LED circuit having an input side for receiving a driving current corresponding to an AC input voltage from an external power source when the magnitude of a driving voltage across said input side is greater than a predetermined value;
- and
- a clamp circuit coupled between said input side of said LED circuit and the external power source, said clamp circuit permitting the driving current to pass through for clamping the magnitude of the driving current to a predetermined current level and for clamping the magnitude of the driving voltage to a predetermined voltage level
- wherein said clamp circuit includes:
- a first diode having an anode adapted to be coupled to the power source, and a cathode;
- a first transistor having a first end coupled to said cathode of said first diode, a second end, and a control end coupled to said input side of said LED circuit;
- a first current limiting unit coupled between said second end and said control end of said first transistor;
- a second diode having an anode coupled to said input side of said LED circuit, and a cathode;
- a second transistor having a first end coupled to said cathode of said second diode, a second end, and a control end adapted to be coupled to the power source;
- and
- a second current limiting unit coupled between said second end and said control end of said second transistor.
8 more elements
A light emitting diode (LED) driving device comprising:
- an LED circuit having an input side for receiving a driving current corresponding to an AC input voltage from an external power source when the magnitude of a driving voltage across said input side is greater than a predetermined value;
- and
- a clamp circuit coupled between said input side of said LED circuit and the external power source, said clamp circuit permitting the driving current to pass through for clamping the magnitude of the driving current to a predetermined current level and for clamping the magnitude of the driving voltage to a predetermined voltage level;
- wherein said clamp circuit includes:
- a first diode having an anode, and a cathode coupled to said input side of said LED circuit;
- a first transistor having a first end coupled to said anode of said first diode, a second end, and a control end adapted to be coupled to the power source;
- a first current limiting unit coupled between said second end and said control end of said first transistor;
- a second diode having an anode, and a cathode adapted to be coupled to the power source;
- a second transistor having a first end coupled to said anode of said second diode, a second end, and a control end coupled to said input side of said LED circuit;
- and
- a second current limiting unit coupled between said second end and said control end of said second transistor.
8 more elements
A light emitting diode (LED) driving device comprising:
- an LED circuit having an input side for receiving a driving current corresponding to an AC input voltage from an external power source when the magnitude of a driving voltage across said input side is greater than a predetermined value;
- and
- a clamp circuit coupled between said input side of said LED circuit and the external power source, said clamp circuit permitting the driving current to pass through for clamping the magnitude of the driving current to a predetermined current level and for clamping the magnitude of the driving voltage to a predetermined voltage level;
- wherein said clamp circuit includes:
- a first transistor having a first end adapted to be coupled to the power source, a second end, and a control end;
- a second transistor having a first end coupled to said input side of said LED circuit, a second end coupled to said control end of said first transistor, and a control end coupled to said second end of said first transistor;
- and
- a current limiting unit coupled between said control end of said first transistor and said control end of said second transistor.
5 more elements
Dependencies are inferred from the claim text.