AN4350 datasheet(13/34 Pages) STMICROELECTRONICS

Part #	AN4350

Description	High power factor LED driver with constant voltage regulation based on HVLED815PF

PDF	34 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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13 / 34 page

DocID025181 Rev 1

13/34

AN4350

Circuit description and design guidelines

where the previous transfer functions are:



Gpwm is the internal PWM modulator gain (Gpwm = 0.5)



Gps(s) is the power stage transfer function (transformer and output filter)



Gfp is the feedback gain between the VOUT and DMG pin



Gsh(s) is the internal sample and hold transfer function



Gea(s) is the error amplifier transfer function (COMP pin network)

Figure 5. Equivalent small signal voltage control loop schematic

The power stage transfer function is calculated considering the transfer function of

a standard flyback converter:

Equation 23

Equation 24

Equation 25

Gps s



Go ps



z1 ps

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





z2 ps

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

–







pps

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





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

Go ps

---

-------

ROUT

RSENSE

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

1dP

–

1dP

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



z1 ps

ESR COUT



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

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