| 摘要 |
A LED driver arrangement includes a switching-mode stage (12) to produce a drive current for feeding one or more LEDs (L) from a DC input (10) and a current sensor (18) sensitive to the current fed to the LEDs (L) for producing a feedback signal indicative of the intensity of the drive current fed thereto. The feedback signal is compared with a reference value indicative (20, 22) of a LED current as requested by a user, in order to generate a control signal (32) able to drive control circuitry (26, 28, 30) in order to obtain such LED current. Control circuitry (26, 28, 30) sensitive to the control signal (32) controls the switching-mode stage (12) so that the drive current fed to the LEDs (L) corresponds to the LED current as requested by the user. An opto-coupler (34) is provided to feed the control signal (32) to the controller circuitry (26, 28, 30). The opto-coupler (34) is configured to saturate when the drive current fed to the LEDs (L) reaches a minimum level. An auxiliary supply voltage (Vaux1) for the control circuitry (26, 28, 30) is derived from an auxiliary winding of a magnetic device of the switching-mode stage (12). The auxiliary supply voltage (Vaux1) is kept above a minimum level by the opto-coupler (34) and the associated biasing circuitry (341, 342), when such opto-coupler (34) is saturated, thus keeping the control circuitry on.
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