Charge pump drive circuit for a light emitting diode
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United States of America Patent
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Sep 18, 2007
Grant Date -
Jun 28, 2007
app pub date -
Dec 27, 2005
filing date -
Dec 27, 2005
priority date (Note) -
Expired
status (Latency Note)
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Abstract
Through operated alternately between a charging phase and a discharging phase, a charge pump converts an input voltage source into a drive voltage for being supplied to a light emitting diode. A current setting unit determines a reference current. A current regulating unit has a current regulating terminal and a feedback detecting terminal. The current regulating terminal is coupled to the light emitting diode so as to control a current flowing through the light emitting diode to be proportional to the reference current. The feedback detecting terminal provides a feedback signal representative of a current regulation characteristic voltage. Based on a difference between the feedback signal and a reference voltage source, an error amplifier generates an error signal. A variable resistance unit is coupled between the input voltage source and the charge pump for adjusting a variable resistance in response to the error signal.
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