Open loop magnetic boost LED driver system and method

Details Open loop magnetic boost LED driver system and method Open loop magnetic boost LED driver system and method

2005-09-13

2005-09-13

Dinh, Trinh Vo (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Impedance or current regulator in the supply circuit

C315S247000, C323S288000

Reexamination Certificate

active

06943504

ABSTRACT:
Current is delivered to a load using an open-loop boost circuit topology that is suitable for LED driver applications. An inductor in the circuit is charged when a transistor is active during a first operating phase. The inductor delivers current to the load when the transistor is inactive during a second operating phase. A ramp circuit is enabled by a feed-forward circuit that detects when the inductor enters the charging cycle. The charging time of the inductor is controlled by a comparator that selectively disables the transistor in response to the ramp voltage. The slope of the ramp is adjusted by an external component (e.g., a resistor) such that the charging time is inversely proportional to the square of the input voltage. The value associated with the inductor can be relatively small, and the boost circuit is arranged to operate over a wide range of operating frequencies.

REFERENCES:
patent: 6577512 (2003-06-01), Tripathi et al.
patent: 6586890 (2003-07-01), Min et al.
patent: 6760238 (2004-07-01), Charych
“LM2704 Micropower Step-up DC/DC Converter with 550mA Peak Current Limit,”National Semiconductor Corporation,2003 (4 pgs.).
“LT1932 Constant-Current DC/DC LED Driver in ThinSOT,”Linear Technology Corporation, (4 pgs.).

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