AN4346 datasheet(24/33 Pages) STMICROELECTRONICS

No. de pieza	AN4346

Descripción Electrónicos	10 W wide range - high power factor - isolated LED driver using HVLED815PF

PDF	33 Pages

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Fabricante Electrónico	STMICROELECTRONICS [STMicroelectronics]

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Electrical waveform

AN4346

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DocID025107 Rev 1

3.3

ILED pin modulation with the input mains voltage

Referring to Figure 30, a voltage VX proportional to the input rectified mains is summed on

the average voltage present on the ILED pin trough the CLED capacitor generating

a voltage reference proportional to the input voltage (AC coupling).

Equation 3

The ILED pin voltage is internally divided (Gi) and then compared with the CS pin voltage,

generating a primary current proportional to the input voltage reaching the high power factor

condition.

The average value of ILED pin is not depending from the VIN input voltage (AC coupling), as

a consequence the desiderated output current can be programed trough the current sense

resistor Rsense in according to the following relationship (see the HVLED815PF datasheet

for more details).

Equation 4

where n is the primary-to-secondary transformer ratio (n = Np/Ns = 190/42), VCLED the

equivalent internal voltage (VCLED(typ) = 0.2 V) that include R, Iref parameters.

VIN pk pk

–

RAC L

RAC H RAC L

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



ILED

---

VCLED

Rsense

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



190

----------

0.2V

1.0



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



0.453A

AN4346 Datasheet(PDF) 24 Page - STMicroelectronics