HVLED815PFTR datasheet(23/36 Pages) STMICROELECTRONICS

Part #	HVLED815PFTR

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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23 / 36 page

HVLED815PF

Device description

Doc ID 023409 Rev 4

23/36

Figure 18.

Voltage control principle: internal schematic

4.7

Voltage feed-forward block

The current control structure uses the VCLED voltage to define the output current, according

to equation

6 on Section 4.5. Actually, the constant current comparator will be affected by an

internal propagation delay TD, which will switch off the MOSFET with a peak current than

higher the foreseen value.

This current overshoot will be equal to:

Equation 8

The previous terms introduce a small error on the calculated average output current set-

point, depending on the input voltage.

The HVLED815PF implements a line feed-forward function, which solves the issue by

introducing an input voltage dependent offset on the current sense signal, in order to adjust

the cycle-by-cycle current limitation.

The internal schematic is shown in

Figure 19.

AM13568v1

Rdmg

Aux

Rf b

From CS pin

To PWM Logic

COMP

DMG

S/H

DEMAG

LOGIC

2.5V

HVLED815PFTR Datasheet(PDF) 23 Page - STMicroelectronics