Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Reexamination Certificate
2008-04-02
2009-06-23
Vu, David Hung (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
C315S2090SC, C315S247000, C315S312000
Reexamination Certificate
active
07550934
ABSTRACT:
An LED driver drives one or more strings of series-connected LEDs. A feedback voltage at a sense resistor is detected by an op amp, and the op amp controls the conductivity of a MOSFET in series with the LEDs to regulate the peak current. The MOSFET is also controlled by a PWM brightness control signal to turn the LEDs on and off at the PWM duty cycle. A boost regulator provides an output voltage to the string of LEDs. A divided voltage at the end of the string of LEDs is regulated by the boost controller to keep the divided voltage constant. When an LED becomes an open circuit, the boost regulator controller is immediately decoupled from the regulator's switching transistor. If an LED shorts, the boost regulator reduces its output voltage, and the duty cycle of the brightness control signal is automatically increased.
REFERENCES:
patent: 7423389 (2008-09-01), Lee
patent: 7439945 (2008-10-01), Awalt et al.
patent: 2007/0114951 (2007-05-01), Tsen et al.
patent: 2008/0150449 (2008-06-01), Wang et al.
Deng Qi
Qiu Weiguang
Le Tung X
Micrel Inc.
Ogonowsky Brian D.
Patent Law Group LLP
Vu David Hung
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