OSRAM OPTOTRONIC Constant current LED power supplies with 3DIM - Manual (Page 17)

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LEDset APPLICATIONS
3.2. Local dimming
3.2.1. Potentiometer application
If an application requires the dimmability of a luminaire, a sim-
ple and economical solution can be to implement a local dim-
ming function by a logarithmic or linear potentiometer. In this
case, the term “local dimming” refers to the possibility to set
the current of a single luminaire system by a potentiometer.
The LEDset interface has been designed for the application
of standard potentiometers with standard rated resistances
of 47 kΩ or 50 kΩ and a tolerance of ±20 %.
Using a potentiometer with a nominal value within this range
allows dimming by changing the current from Inom
max
(at Vset > 10 V but less than 11 V) to 0 mA (at Vset < 1 V) or
higher, taking account of the Imin limit and the turn-off
capability (see cases I and II in chapter 2.2.2.).
Note 1: Potentiometers with nominal values lower than
47 kΩ - 20 % do not provide the complete dimmable range of
the output current. Nominal values higher than 50 kΩ + 20 %,
however, can enable the device to reach the range of Vset
> 11 V, changing the output current setting to Imin or 0 %
(see table 1).
Note 2: Local dimming means that the used dimming device
is a single-insulated potentiometer or a potentiometer that
is part of a multifunctional device and needs to be double-
insulated from the parts related to the mains potential if the
application is SELV-classifi ed (see general note on insulation
in chapter 2.3.4).
Suitable potentiometers for this application are for example:
• Vishay P16 NP 47K 20 % A (linear potentiometer)
• Vishay P10 YM AG 47K 5 % (medium-cost potentiometer)
• Tyco CB10KH473ME (low-cost potentiometer)
Figure 8: Local dimming – potentiometer application.