AN2950 datasheet(17/37 Pages) STMICROELECTRONICS

17 / 37 page

AN2950

Testing the board

Doc ID 15494 Rev 1

17/37

Figure 22.

Input voltage averaged efficiency vs load

In version 2.0 of the ENERGY STAR® program requirements for single voltage external

AC-DC power supplies(a), the power supplies are divided into two categories: low-voltage

power supplies and standard power supplies with respect to the nameplate output voltage

and current. To be considered a low-voltage power supply, an external power supply must

have a nameplate output voltage of less than 6 V and a nameplate output current of more

than or equal to 550 mA.

The following tables report the EPA energy efficiency criteria for AC-DC power supplies in

active mode for standard models and low voltage models respectively.

The criteria are plotted in Figure 23, where the red line depicts the criteria for the standard

model and the blue line the criteria for the low voltage model. The PNO axis uses a

logarithmic scale.

Refer to Chapter : References.

Table 11.

Energy efficiency criteria for standard models

Nameplate output power

(Pno)

Minimum average efficiency in active mode

(expressed as a decimal)

0 to = 1 W

= 0.48

× Pno + 0.140

> 1 to = 49 W

= [0.0626 × In (Pno)] + 0.622

> 49 W

= 0.870

Table 12.

Energy efficiency criteria for low-voltage models

Nameplate output power

(Pno)

Minimum average efficiency in active mode

(expressed as a decimal)

0 to = 1 W

= 0.497 × Pno + 0.067

> 1 to = 49 W

= [0.075 × In (Pno)] + 0.561

> 49 W

= 0.860

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