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Dynadimmer working principe
Dynadimmer offers two options: time-based and location-based.
The time-based option does not compensate for seasonal changes
and starts executing the Dynadimmer profile as soon as power is
applied to the driver. This option is best suited for applications with
fixed power-on/off timing.
However, in most outdoor applications the timing will vary per season
and the dimming schedule should thus be adapted accordingly. For this
Philips has introduced the programmable Dynadimmer feature which
simply uses the driver power-on time duration as reference.
Based on the average power-on time of the previous periods, the
driver is able to estimate the current time of day and uses this as a
virtual clock time which serves as reference for the dimming schedule
programmed by the user.
The Dynadimmer feature relies on a regular power-on time from one
night to the next. Typically, the power-on time is based on sunset and
sunrise and its duration will vary gradually throughout the seasons.
The Dynadimmer therefore calculates the power-on time average of
the five last preceding stable nights. A stable night is regarded as a
night with a power-on time of at least four hours within a tolerance of
one hour that equals the latest calculated average power-on time. This
implies that after first installation the Dynadimmer will need three
stable nights to be able to calculate the virtual clock time required
for the programmed dimming schedule. During this synchronization
phase the Dynadimmer will not dim the light output for the first
three nights.
Depending on geographical location or on the application, the switch-
on time is not always evenly distributed around midnight. To be able
compensate for the difference in sunrise and sunset over a time zone,
the user can set his geographical location in both western or eastern
direction.
For example if the sunset in Berlin is at 19:00 this will be in Poland at
18:25 and in Portugal 19:35. To be able to synchronize the absolute
clock time with a photocell controlled system in Poland the offset
should be set at -25 minutes and for Portugal +35 minutes.
By default the mid position of a time zone (in above time-zone this will
be close to Berlin) will be selected; in most cases this default value will
be accurate enough.
The midnight shift option is of course not available when the Time
based option has been selected.
Since the frequency of the power grid is used the accuracy of timing is
very high and is typically far within 1%. Nearby luminaires
connected on the same on/off cycle and programmed with the
same Dynadimmer schedule will dim down and up simultaneously.
In
normal
operation
mode
(after
the
synchronization
phase)
the Dynadimmer will handle maintenance or short power
interruption in correct ways, thus preventing dimming schedule
disruptions.
Design-in Guide - Philips Xitanium LED Xtreme driver
34
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