Boost LED driver not using output capacitor and blocking diode

Details Boost LED driver not using output capacitor and blocking diode Boost LED driver not using output capacitor and blocking diode

2011-04-05

2011-04-05

Tran, Thuy Vinh (Department: 2821)

Electric lamp and discharge devices: systems

Condenser in the supply circuit

Arc machining

C315S246000, C315S307000

Reexamination Certificate

active

07919928

ABSTRACT:
An LED driver is disclosed that boosts an input voltage to drive any number of LEDs in series. The driver includes a switch-mode current regulator that supplies regulated current pulses to the LEDs. No high voltage output capacitor is used to smooth the current pulses, so the LEDs are turned on any off at the switching frequency. Also, no blocking diode between the switching transistor and the LEDs is used. The cathode of the “bottom” LED in the string is connected to ground via a current sense resistor. In parallel with the sense resistor is connected an RC filter using a small, low voltage filter capacitor. The RC filter provides a substantially smooth feedback voltage for the current regulator to control the duty cycle of the switching transistor so that the feedback voltage matches a reference voltage.

REFERENCES:
patent: 6285139 (2001-09-01), Ghanem
patent: 7122971 (2006-10-01), Yeh et al.
patent: 7550934 (2009-06-01), Deng et al.
patent: 7671575 (2010-03-01), Suzuki et al.

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