Thermal Constrains; 1.Heatsink Performance - powersoft IpalMod User Manual

Thermal constrains

This device must be correctly heatsinked for proper and
reliable operation.
The built-in fans and an appropriate external passive
heat sink guarantee by design thermal efficiency and
reliability.
Proper heatsink planarity is strongly suggested to al-
low thermal transfer from the module's bottom plate to the
heatsink; a thermal compound may be used, but it is not
strictly necessary.
In order to ensure proper ventilation of the module, rea-
sonable spacing of at least 100 mm must be left between
the frame of the unit and any side component or surface of
the enclosure.
The module has been designed to fit into a loudspeaker
cabinet: please refer to FIGURE 1
IN FIGURE 1 HEATSINK FINS ARE SET HORIZONTALLY
(WRONG!) ONLY FOR DESCRIPTIVE PURPOSE.
All configuration showed in
proper module placing and cooling. We suggest to posi-
tion the module vertically with respect the ground in order
to take advantage of the chimney effect for ventilation and
heat dissipation.
In FIGURE 1.a the module and the loudspeakers share
the same room into the cabinet. This is the dafault place-
ment solution: it allows good ventilation because of woofer
diaphragm movement and high air volume; be aware of
magnetic field interaction: place the module far enough from
loudspeakers magnet in order to prevent fans blockage.
FIGURE 1.b shows the more efficient cooling configura-
tion, even if it is less effective against dust and moisture
that can get into the module. By allowing external air flow,
it is possible to reduce the fins width on the heatsink by
maintaining good cooling performances.

8 : 1.Heatsink performance

Here we suggest a rule of thumb to calculate the thermal
resistance of the heatsink.
The absolute thermal resistance of the heatsink is the
temperature difference (kelvin or celsius) across it structure
when a unit of heat energy flows through it in unit time (watt).
For seek of simplicity, a heatsink with low thermal resistance
offers high heat dissipation, as well as a low electric resist-
ance allows high current flow through a conductive wire.
In order to define the maximum allowed thermal resist-
ance for the heatsink let assume the following:
f e as the amp module efficiency
f cf as the crest factor of the audio signal
f W as the peak power delivered by the module
max
f T as the highest ambient temperature
amb
f T as the highest operating temperature
mod
2 | IpalMod | User guide
for proper module placing.
FIGURE 1 are viable for
100 mm
3.94 inch
Be aware of
magnetic leakage
FIGURE 1: Cooling solutions (for descriptive purpose the
heatsink fins are set in wrong direction);
a) Module and loudspeaker into the same chamber;
b) Module in a separate vented chamber.
The thermal resistance of the heatsink derives from the fol-
lowing formula:
R =
th
Dissipated power
The maximum dissipated power can be calculated as:
Dissipated power =
For example, stating an efficiency of 80%, 6 dB crest factor
and 3400 W peak power, the dissipated heat is:
3400 (1 - 0.8)
4
8
MIN.
a
b
T - T
mod amb
W (1 - e)
max
cf
= 170 W