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I have a DCP010512BP 5->12V DC-DC Converter from Texas Instruments. With a supply voltage of 5.00V on Vin and a 4.7uF ceramic cap across the output, I read the output voltage as 21.0V with a digital mulimeter with no loading applied.

This is obviously way out of spec for the output voltage of 12V +/- 10%.

Could the ripple noise be somehow affecting my multimeter, or is this kind of behaviour expected when unloaded?

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    \$\begingroup\$ I'm adding as a comment because I don't have much valuable specific info, but yes, completely unloaded switching boost supplies can output much higher than nominal when unloaded. Definitely expected behavior with certain topologies. \$\endgroup\$
    – scld
    Commented Sep 12, 2013 at 3:45
  • \$\begingroup\$ Thanks Chris, it seems to behave more as expected with some load applied. \$\endgroup\$
    – Damien Walsh
    Commented Sep 16, 2013 at 17:51

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According to the datasheet, the output voltage will only be within 15% of its nominal value for load currents that are ≥10% of the maximum load. See Note (2) on page 3.

The issue with light loads is leakage inductance in the transformer, which causes an unwanted "flyback" effect from the excess stored energy.

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  • \$\begingroup\$ Does certainly seem to be dependent on load. Thanks! \$\endgroup\$
    – Damien Walsh
    Commented Sep 16, 2013 at 17:52

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