23 June 2005
HE104MAN-V8 Manual
Tri-M Engineering
Tel:
800.665.5600, 604.945.9565
1407 Kebet Way, Unit 100
Fax:
604.945.9566
Port Coquitlam, BC V3C 6L3
E-mail:
info@tri-m.com
Canada
Web site:
www.tri-m.com
15
2.10 HE104 Efficiency and Heat Dissipation Calculation
The average efficiency for the +5V output of the HE104 is 90 percent. The efficiency, however, at any
specific input voltage, output load and ambient temperature many be higher or lower. Typical
efficiency is between 88 and 94 percent. Best efficiency occurs at mid input voltage ranging from16
to 18V, mid output loads are from 20 to 30 watts and a low heat sink temperature. The input voltage
and output load is determined by the system application. This leaves only the heat sink temperature
that System Intergrators adjust to maximize efficiency. Either the forced flow fans, which thermally
couples the HE104 heat sink to enclosures or external heat sinks can improve the efficiency of the
HE104. An improvement of 3 to 4 percent, can be obtained by good thermal management in which
the results are 35 percent less heat dissipated.
A. Heat Dissipated (HD) = Input Power – Actual Load
Where Input Power = Input Voltage * Input Current and Actual Load = +5V load +(+12V load)
+(-5V load) + (-12V load) (Load measured in watts)
B. Estimated Heat Dissipated (ESD) can be calculated based on 90 percent efficiency:
EHD = {+5V load + [(+12V load) +(-12V load)]/0.9} * 0.1
C. If the Battery Input option is installed or the Reverse Diode Protection (RDP) option installed
additional heat will be dissipated.
RDPD = Total Load/Input Voltage *0.7V (diode drop)
D. If the Battery Charger Option is installed the heat dissipated from it will vary according to the
current charge current. Maximum heat dissipation will occur when charging at maximum
current and can be estimated by:
BCD= Maximum Charge Current * Charge Voltage * 0.2
(Based on 80 percent efficiency)
