PP420 LED lighting controllers - User Manual
7
PP420 heat output
The PP420 controller has a linear circuit to produce constant current
output. This section explains how to calculate the heat output from the
PP420 and what measures you can take to manage it.
7.1
Heat output per channel
For a continuous output current, the heat output is given by:
Heat output =
I
O
x (V
S
- V
L
)
Where:
I
O
= Output current set by the user
V
S
= Supply voltage across VS1+ and GND
(for output 1)
V
L
= Voltage across the light LD1+ and LD1–
(for output 1)
This is usually easy to calculate as the voltage across the light is normally
the voltage rating of the light as declared in its specification. Alternatively
you can measure it using a voltmeter.
For a pulsed output, the heat output is given by:
Heat output =
I
O
x duty cycle x (V
S
- V
L
)
Where:
I
O
= Output current set by the user
V
S
= Supply voltage
V
L
= Voltage across the light
And duty cycle is defined as:
Duty cycle = WP x FT
Where:
W
P
= Pulse width in seconds
F
T
= Trigger frequency in Hz
When overdriving, the voltage across the light is more difficult to identify. In
most cases, you can use the voltage rating of the light.
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