AN3286 datasheet(38/42 Pages) STMICROELECTRONICS

38 / 42 page

Test equipment and measurement of efficiency and light load performance

AN3286

38/42

Doc ID 17998 Rev 1

the UUT at light load conditions), but at heavy load conditions, when the UUT input current

increases, the error introduced in the measurement with this setting can be relevant.

Figure 52.

Suggested connection for low power measurements

(switch in position 1)

In this case, it is advisable to connect the switch shown in Figure 51 to position 2 (see

simplified scheme in Figure 52); the UUT’s input voltage is measured directly to the UUT’s

input terminal and the input current does not affect the measured input voltage.

Figure 53.

Suggested connection for high power measurements

(switch in position 2)

With this setting, the measurement error is introduced by the shunt resistance of the

voltmeter, which is not infinite, that then causes a leakage current inside the voltmeter itself.

This current is measured by the ammeter together with the UUT’s input current, but the error

AN3286 Datasheet(PDF) 38 Page - STMicroelectronics