AN3028 datasheet(18/37 Pages) STMICROELECTRONICS

18 / 37 page

Burst mode and output voltage ripple

AN3028

18/37

Doc ID 16135 Rev 1

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

AC-DC power supplies (see References), the power supplies are divided in two categories:

low-voltage power supplies and standard power supplies with respect to the nameplate

output voltage and current. An external power supply, in order to be considered a low-

voltage power supply, needs to have a nameplate output voltage lower than 6 V and a

nameplate output current greater than or equal to 550 mA.

The tables below show the EPA energy efficiency criteria for AC-DC power supplies in active

mode for standard models and for low voltage models respectively.

The criteria are plotted in Figure 22, where the red line is the criteria for the standard model

and the blue line is the criteria for the low-voltage model. The PNO axe is in logarithmic

scale.

Figure 21.

Input voltage averaged efficiency vs. load

a) without self-supply (J2 selected)

b) with self-supply (J and J2 not selected)

Table 10.

Energy efficiency criteria for standard models

Nameplate output power

(Pno)

Minimum average efficiency in active mode

(expressed as a decimal)

0 to = 1 watt

= 0.48*Pno+0.140

> 1 to = 49 watts

= [0.0626 * In (Pno)] + 0.622

> 49 watts

= 0.870

Table 11.

Energy efficiency criteria for low-voltage models

Nameplate output power

(Pno)

Minimum average efficiency in active mode

(expressed as a decimal)

0 to = 1 watt

= 0.497 *Pno+0.067

> 1 to = 49 watts

= [0.075 * In (Pno)] + 0.561

> 49 watts

= 0.860

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