Philips eS21, Руководство по установке и эксплуатации

Страница: 10 / 30

Installation & Operation Guide
eS21 LED Raceway
8
DIMMER SYSTEM FUNDAMENTALS
DIMMER SYSTEM FUNDAMENTALS
1. eS21 IGBT Dimmers
The eS21 dimmers are multi-mode units that automatically analyzes its connected load and picks the most
appropriate dimming technique. Depending on the load, the dimmer will use either Reverse Phase Control (RPC) or
Forward Phase Control (FPC). Whenever possible, the dimmer will choose RPC because of the advantages it offers in
terms of reduced lamp noise and increased regulation accuracy. Both techniques control the average power applied to
the load by limiting current flow to only certain portions of each power line half cycle.
Forward Phase Control
Forward Phase Control is the technique used by all previous electronic dimmers, although earlier implementations
have been far less sophisticated than eS21 dimmers. This scheme only allows current to flow during the latter portion
of each half cycle. As the relative duration of the conducting portion is increased, so is the average power applied to
the load, and hence its brightness.
Reverse Phase Control
Reverse Phase Control, on the other hand, limits current flow to the early portions of each half cycle. The dimmer
monitors the power applied to the load in real time during the half cycle and adjusts its switch-off point as needed to
regulate the light output.
When switching-off the output in each half cycle, it is important to control the slope of the falling wave form so as to
minimize the acoustic noise made by the lamp filament, and the radio frequency noise radiated by the dimmer.
Previous dimming technologies accomplished this by placing a large coil of wire in series with the output of the
dimmer. The unique power stage in eS21 dimmers allows this function to be performed directly in the dimmer. By
stretching this fall time out to 400 or even 650 µS, eS21 dimmers achieve exceptionally quiet operation without high
insertion losses, and without the line distortion caused by inductors.
Note: Some manufacturers sometimes refer to "Forward Phase Control" as "Leading Edge" and "Reverse Phase
Control" as "Trailing Edge."
2. eS21 LED Raceway Modules
Dimmer Modules
Each eS21 LED Raceway Dimmer Module contains a dual dimmer assembly (2.5kW) with power shared between the
two dimmers within the module. Each dual dimmer module includes two Focus/LED Indicator buttons (see
Figure
1 ), that functions as both focus adjustment control and status indicator for its dimmer.
Vo
lt
s
Time
Power Line FPC (50% Conduction) RPC (50% Conduction)
Fall Time