MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC
MP4031 Rev.1.03 www.MonolithicPower.com 19
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APPLICATION INFORMATION
Components Selection for Triac dimming
application
It is the same with MP4030, please refer to
AN055 for detailed information.
Components Selection for Analog dimming
application
The bleeding and damping circuit are not needed
in analog dimming application.
The analog dimming signal V
A_DIM
is divided by
R1 and R2, and then connected to CS/DIM pin.
The selection of the current sense resistor ( Rs )
is the same with MP4030, it is determined by the
full-load output current. A 1kΩ resistor is
recommended for R1, which is much bigger than
Rs, so will not influence the output current when
the dimmer is not connected. R2 is determined
by the V
A_DIM
, it can be calculated by the following
equation approximately:
A_DIM_MAX
R1
*V 0.8V
R1 R2
=
+
This equation can get a min R2 to make sure the
output current will be at full load with max
dimming signal
A_DIM_MAX
V . In most application,
R2 need to be increased to enlarge the dimming
ratio.
And other components’ selection can refer to
AN055.
