DF04M Просмотр технического описания (PDF) - STMicroelectronics
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DF04M Datasheet PDF : 42 Pages
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AN1262 APPLICATION NOTE
Table 22. (continued)
VR
ηT
Vspike
VCC
VF
VBF
Pre-design Choices
120 V
0,9
80 V
12 V
0.6 V
3V
Bridge rectifier selection.
An integrated bridge (DF06M, 4x1A/600V, GI) has been selected.
Reflected voltage
Transformer efficiency
Leakage inductance overvoltage
L6590 supply voltage
Secondary diode forward drop
Bridge Rectifier + EMI filter voltage drop
Input Bulk Capacitor.
From table 5, in order for the valley voltage on the input cap to be around 90 V, a minimum capacitance of about
27 µF should be used. A standard 22 µF/400V electrolytic capacitor will be chosen. After few iterations, the (1)
cycle converges at Vinmin = 84.9V, Tc = 2.11 ms. From eqn. 2, VDCmin = 103.2 V.
Table 23b) shows the results of a second step of calculations, aimed at checking that no limit of the device is
violated. The result is OK.
Operating conditions @ Vin = VDCmin and thermal check.
The results are listed in table 23c). With these data the power dissipated by the L6590 is calculated and the
result is shown in table 23d).
From eqn. 3, the maximum junction-to-ambient thermal resistance needed for reaching thermal balance at Tj =
125 °C is 51.2 °C/W. From the diagrams of fig. 21 it is possible to see that this can be obtained with about 1 cm2
copper area on the PCB.
Figure 21. L6590 Family Packages Junction-to-Ambient Thermal Resistance
[°C/W]
52
51
50
49
48
47
1 Oz 2 Oz
MINIDIP
Rthja vs. PCB copper area
[°C/W]
56
54
52
50
48
1 Oz 2 Oz
SO16W
Rthja vs. PCB copper area
46
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Pdiss = 1.4 W
[cm^2]
46
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Pdiss = 1.4 W
[cm^2]
34/42
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