My customer investigating low cost LED driver IC.
Is it possible to use ADP1614 as a LED Driver with its adjustable current limit function?
If yes, can I obtain reference circuit for 5 white LEDs in series?
Thank you for your support.
Please refer to the following schematic for driving LEDs in series using the ADP1614:
At no load condition (LED remove or broken), the LED string removes the pathway from the output to Feedback Pin of ADP1614, the voltage at the feedback VFB was pulled to ground, so the converter increases its duty cycle to maintain the correct voltage on the feedback pin which causes the output voltage rising to the maximum. To solve the problem, a Zener diode (Z1) is needed from the output to the FB pin to create an alternate pathway when the LEDs were removed or broken. The voltage of the Zener need to be higher than the normal output voltage so that there is no current flows through it during normal operation. Also, the voltage of theZener need to be lower than the allowed maximum voltage.
Connect a sense resistor between the LED branch and GND. The output current tolerance depends on the accuracy of Rsense. ILED=VFB/Rsense, VFB=1.245V.
For other components selection, please download the design tool ADP1614 Boost Designer, input the input voltage range, output voltage and max output current, the tool you provide you the BOM and the estimated performance.
Just for your information, ADP1649, ADP1650, ADP1653 and ADP1655 and ADP1660 have LED short-circuit and open-circuit protection function for LED drive.
Here is an article on Converting a Buck Regulator into a Smart LED Driver, some of the tricks also can be applied to a Boost circuit.
Thank you very much for your detailed explanation.
I understand the circuit.