EPR-68 Datasheet, PDF (20/28 Pages) Power Integrations, Inc. – Engineering Prototype Report for EP 68 - 6.6 W DC-DC Flyback Converter Using DPA-Switch- (DPA423G)

EP68 3.3 V, 2 A DC-DC Power Supply
19-Jul-2005
11 Thermal Performance
The temperatures of key components were recorded using T-type thermocouples. Two
of the four thermocouples were soldered; one directly to a SOURCE pin of the DPA423G
(U1) and the other to the cathode of the output rectifier (D1). The other two
thermocouples were glued; one to the transformer (T1) core, on the center leg, and the
other to the case of the first (of the two) high-ripple output capacitor (C7).
The unit was operated at full load, at 36 VDC, 48 VDC and 57 VDC, in free convection
within a small enclosure.
The results show adequate thermal margin, considering an additional ambient rise of
+28 °C, equivalent to operating at an ambient of 50 °C. At 36 VDC, full load, within an
enclosure at 50 °C ambient, this equates to a DPA423G case temperature of 79 °C. This
is well below the recommended maximum case temperature of 100 °C.
Figure 24 is an infrared thermograph taken at nominal-line (48 VDC).
Measured Temperature (°C)
Item
36 VDC 48 VDC 57 VDC
Ambient
22
22
22
DPA423G (U1)
51
51
53
Transformer core (T1) 75
75
75
Output Rectifier (D1)
63
61
61
Output Capacitor (C7) 45
43
43
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