HVLED815PF datasheet(20/36 Pages) STMICROELECTRONICS

Part #	HVLED815PF

Description	Offline LED driver with primary-sensing and high power factor up to 15 W

PDF	36 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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20 / 36 page

Device description

HVLED815PF

20/36

Doc ID 023409 Rev 4

4.5

Constant current operation

Figure 16 presents the principle used for controlling the average output current of the

flyback converter.

The voltage of the auxiliary winding is used by the demagnetization block to generate the

control signal for the internal MOSFET switch Q. A resistor R in series with it absorbs a

current equal to VILED/R, where VILED is the voltage developed across the capacitor CLED

capacitor.

The flip-flop's output is high as long as the transformer delivers current on secondary side.

This is shown in

Figure 17.

Figure 16.

Current control principle

Figure 17.

Constant current operation: switching cycle waveforms

AM13566v1

VILED

Icled

DMG

ILED

Iref

CLED

DEMAG

LOGIC

Aux

Rf b

Rdmg

From CS pin

To PWM Logic

AM13567v1

IPRIM

IREF

ISEC

ICLED

VILED/R

TONSEC

HVLED815PF Datasheet(PDF) 20 Page - STMicroelectronics