a d v a n c e d i l l u m i n a t i o n . c o m
P u l s a r 3 2 0 M a n u a l
P u l s a r 3 2 0 M a n u a l
4.1.1 Duty Cycle:
The ratio of the time the light head is “on” (pulse
width, Pw) to the time it is “off” (period, Tp). Calculated as (Pw / Tp) x 100.
The result is expressed in percent. The Signatech II feature of the Pulsar
320 allows the Pulsar 320 to limit the maximum duty cycle based on the
characteristics of the driven light head.
4.1.2 Latency:
The time between the receipt of a trigger signal and
initiation of the output drive pulse. The latency is the sum of the rise-times
and propagation delays within the trigger processing circuitry. This time is
purposely kept to a minimum.
4.1.3 LED and Light head Characteristics:
Many factors contribute
to the operational parameters of an LED light head. To optimize Pulsar
320/light head operation, these characteristics are stored as part of the
information provided to the Pulsar 320 by the Signatech II circuit within
the light head. Some of the variables that affect how the light head can be
driven are outlined below.
4.1.3.1 LED Forward Voltage:
The forward voltage drop across an LED
(VFWD) depends upon the nature of the semiconductor junction and the
current through the LED. The specified VFWD for an LED is usually given
at its recommended operating current. Please note that when driven by
high current pulses, VFWD can increase by 10 to 20 times. For this reason
voltage levels at the Pulsar 320 output can be as high as 100 volts.
4.1.3.2 LED Thermal Resistance:
A measure of temperature difference
between the LED junction and the LED connection to an external heat sink.
Overheating of the junction is the primary cause of failure in LEDs. The
value of the LED thermal resistance, combined with the heat sink thermal
resistance and the overall thermal time constant determine the maximum
pulse width, pulse current, and duty cycle of the light head.
4.1.3.3 LED Voltage Slope:
The relationship between VFWD and the
forward current IFWD, used by Signatech II to calculate the voltage required
to provide the desired current.
4.1.3.4 Light head Characteristics:
Also contained within the data
provided by Signatech II to the Pulsar 320 are the number and type of LEDs
in each string and the number of parallel strings connected to each channel.
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