I have a 24V power supply line which I would like to transform to 5V (<1A) in order to supply my chips. Voltage regulators would waste a lot of energy in this range. I looked at some datasheets of such switching regulators e.g. TSR1-2450. On page 1 it is stated that an efficiency of 92% can be achieved.

How is the energy loss calculated?

I would understand it that way: Regulation from 24V to 5V@1A results in 5W maximal output. With 92% efficiency the circuit would need

5W*1.08 = 5.4W

  • \$\begingroup\$ 5W / 0.92 actually, so a little bit over 5.4W. \$\endgroup\$
    – ocrdu
    Jan 27, 2021 at 11:53
  • 2
    \$\begingroup\$ The data sheet says Efficiency up to 92% - so expect less. \$\endgroup\$
    – Andy aka
    Jan 27, 2021 at 11:56

1 Answer 1


That's correct.

$$ P_{IN} = \frac {P_{OUT}} {eff} = \frac 5 {0.92} = 5.43 \ \text W $$

Be aware that the efficiency will drop off somewhat at lower loads.

  • \$\begingroup\$ so the loss follows a curve (similar to electronics.stackexchange.com/questions/149218/…)? Since the datasheet is rather short I can assume, that the 92% is measured a the best point in the curve. \$\endgroup\$
    – v3xX
    Jan 27, 2021 at 12:29
  • \$\begingroup\$ I'd say that marketing would go for the peak figure, so yes. \$\endgroup\$
    – Transistor
    Jan 27, 2021 at 13:03
  • \$\begingroup\$ My circuit operates at 700mA. As long as the 1A are guaranteed I can\ must live with the losses. \$\endgroup\$
    – v3xX
    Jan 27, 2021 at 14:13

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