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6 Selection of a DC/DC voltage converter (power module)

6.1 What makes the difference?

6 Selection of a DC/DC voltage converter (power module)

6.1 What makes the difference?

There are several factors to consider when selecting a power module. The require-

ments are essentially determined by the application, i.e. the supply side and load side,

as well as the ambient conditions.

Crucial points for selection:

• Input voltage range

• Output voltage range

• Output current/power

• Ambient temperature

• Package type

• EMC

• Output ripple

• Switching frequency

• Efficiency

• Options (additional functions)

The power modules from Würth Elektronik eiSos GmbH & Co KG can be used in almost

every application, as they have a wide input and output voltage range. The efficiency

is usually >85% and the power modules have hardly any thermal derating (Fig. 6.1),

which is an attribute of the construction.

This means that the maximum output current can be provided at the maximum

ambient temperature without an external heat sink.

Fig. 6.1: Thermal derating taking the example of order code 171020601

Thermal derating

Ambient temperature

Thermal Derating:

OUT

= 3,3 V @ θ

= 19,6 °C/W

Ambient Temperature [°C]

2,5

2,0

1,5

1,0

0,5

50 60 70 80 90 100 110 120

Output Current [A]

= 12 V

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6 Selection of a DC/DC voltage converter (power module) 6.1 What makes the difference? 6 Selection of a DC/DC voltage converter (power module) 6.1 What makes the difference? There are several factors to consider when selecting a power module. The requirements are essentially determined by the application, i.e. the supply side and load side, as well as the ambient conditions.
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6 Selection of a DC/DC voltage converter (power module) 6.1 What makes the difference? High efficiency and low power losses are the most important considerations in the selection of a DC/DC converter. The efficiency curve, see datasheet, plays a major role and, as shown in the graph (Fig. 6.2), the optimum operating point is mostly found in the mid range area of the output current (red box). If too little power is taken from the power module, it works in the inefficient discontinuous mode.
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6 Selection of a DC/DC voltage converter (power module) 6.1 What makes the difference? Fig. 6.3: Output voltage ripple @ 5 V taking the example of order code 171020601 A further important point that should be considered in module selection is EMC. Many DC/DC voltage converters do have interference-suppressing components integrated to reduce interference, but further, external filters may be necessary to comply with the relevant EMC standards.