AN4205 datasheet(21/23 Pages) STMICROELECTRONICS

Part #	AN4205

Description	The most recent developments in energy savings fit perfectly

PDF	23 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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21 / 23 page

AN4205

Test results

Doc ID 023929 Rev 1

21/23

Figure 15.

Main signals of the output stage

●

Figure 14 shows the details of the linear current regulation. When the value of VB (base

voltage of bipolar Q1) rises, VGS of the Power MOSFET M2 decreases and the IDS

(IOUT) current decreases. That allows fixing the current variations to approximately

350 mA.

●

Figure 15 shows the features of the output stage main signals. The IOUT ripple current

(red waveform) is very low and the VDS average value is around the voltage threshold

fixed by specification:

Targeting higher energy conservation, the main features of the LED driver result in an

almost constant IDS (IOUT) current, ensuring a very long lifetime for the LED components

and a regulated VDS signal in order to minimize the power losses during linear regulation

which is the most important feature of the LED driver because it compensates for the cost of

efficiency of the standard.

AM16381v1

DS average

()

Dground

VR2

300mV

∼

–

AN4205 Datasheet(PDF) 21 Page - STMicroelectronics