AN3028 datasheet(33/37 Pages) STMICROELECTRONICS

33 / 37 page

AN3028

Test equipment and measurement of efficiency and low-load performance

Doc ID 16135 Rev 1

33/37

least 30 minutes (warm-up period) immediately prior to conducting efficiency

measurements.

After this warm-up period, the AC input power shall be monitored for a period of 5 minutes to

assess the stability of the UUT. If the power level does not drift by more than 5% from the

maximum value observed, the UUT can be considered stable and the measurements can

be recorded at the end of the 5-minute period.

If AC input power is not stable over a 5-minute period, the average power or accumulated

energy shall be measured over time for both AC input and DC output.

Some wattmeter models allow integrating the measured input power in a time range and

then measuring the energy absorbed by the UUT during the integration time. The average

input power is calculated by dividing by the integration time itself.

Figure 34.

Connections of the UUT to the wattmeter for power measurements

DISPLAY

AVG

WATT METER

SOURCE

U.U.T

(Unit Under test)

INPUT

Multiplier

Voltmeter

Ammeter

OUTPUT

Switch

AN3028 데이터시트(PDF) 33 Page - STMicroelectronics