Experimental results

AN2623

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4.6

Thermal measurement and global efficiency

One of the most critical parts of the power supply is the MOSFET. As previously seen at the

end of Section 3.4: Power transformer design and MOSFET choice a heatsink is necessary.

To verify the correct thermal behavior of the MOSFET, it was checked at maximum load and

maximum input voltage. The device reaches the thermal steady state of 94 °C.

Figure 12 shows the global efficiency in function of the input voltage for two values of load.

From the graph, we can conclude that the board has good efficiency. In absolute terms the

The technical requirements for this converter have been respected.

Figure 12.

Efficiency of the system

Table 3.

Bill of material

Item

Quantity

Reference

Properties

1

1

1

TL 431 STMicroelectronics part

2

2

CB1

47 nF X2 Cap

CA1

47 nF X2 Cap

31

CT1

4.7 nF

4

1

C1

270 µF, ESR=42 m

Ω, 50 V, electrolytic capacitor

5

2

C2

100 µF, 450 V, electrolytic capacitor

C3

100 µF, 450 V, electrolytic capacitor

6

1

C4

330 µF, 450 V, electrolytic capacitor

7

1

C5

2.2 nF, Y1 Cap

81

C6

33 nF

9

1

C7

10 µF, 20 V electrolytic capacitor

10

1

C8

6 nF

11

2

C9

100 pF ceramic capacitor

C10

100 pF ceramic capacitor

12

1

C11

22 µF, 25 V, electrolytic capacitor

13

1

C12

1 nF ceramic capacitor

76.00

77.00

78.00

79.00

80.00

81.00

82.00

83.00

84.00

85.00

86.00

87.00

88

220

290

Input voltage (V)

Load=4.5A

Load=2.3A