AN2690 datasheet(14/31 Pages) STMICROELECTRONICS

Part #	AN2690

Description	This application note describes the characteristics and the features

PDF	31 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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14 / 31 page

Functional check

AN2690

14/31

Figure 12.

Frequency foldback circuit

Equation 1

Equation 2

Figure 13 and 14 show the input power consumption and the efficiency of the board working

at light-load conditions, for example when a power supply is powering a laptop during

power-saving operation.

As shown, the input power consumption is always very low and the efficiency remains

significantly high even at output power levels where normally the power supply’s efficiency

drops.

L6566A

OSC

R42

COMP

VREF

R74

R70

osc

210

⋅

R42

-----------------

≈

fold

back

–

210

R42

-----------

–

⎝⎠

⎛⎞

⋅

≈

Figure 13.

EVL6566A-75WADP o/p power vs.

input power at light load

Figure 14.

EVL6566A-75WADP light-load

efficiency

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

Pin [W]

230Vac-50Hz

115Vac-60Hz

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

Pout [W]

230V-50Hz

115V-60Hz

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