Specifications

Circuit Operation Description
Samsung Electronics 5-5
5-1-3(B) THE RELATION BETWEEN POWER CONSUMPTION AND POWER CONVERSION Efficiency
The power consumption and the power conversion efficiency of SMPS affect protection against heat and
system operation much.
[ If the power conversion efficiency of 100W SMPS is 70%, is the power loss of internal circuit 30W? ]
Output power consumption Po is determined by the multiplication of DC output voltage Vo and output
current Io. Input power consumption Pi is determined by the addition of output power consumption
Po and internal power loss of SMPS Pl.
Provided that the power conversion efficiency is _,
If the power conversion efficiency of 100W SMPS is 70%, the internal power loss is about 42.8W by
Equation (1). If the power conversion efficiency of 400W SMPS for 42"SD is 82%, the internal power loss
is 87.8W by Equation (1). Table 4 shows internal power loss as a function of output power for various
power conversion efficiencies.
Table 4. Power Conversion Efficiency vs. Internal Power Loss
0
20
40
60
80
100
120
140
160
180
200
120 140 160 180 200 240220 260 280 300
50%
60%
90%
70%
80%
η
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η
=
η
=
η
=
η
=
Internal
Power
Loss ( W)
Direct Current Output Power (W)