AN4496 datasheet(4/18 Pages) STMICROELECTRONICS

Il numero della parte	AN4496

Spiegazioni elettronici	How to get a high power factor with the HVLED815PF device

PDF	18 Pages

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Produttore elettronici	STMICROELECTRONICS [STMicroelectronics]

Homepage	http://www.st.com

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4 / 18 page

ILED pin

AN4496

4/18

DocID026370 Rev 1

In case of sinusoidal mains voltage, if the input current is in phase and with the same

waveform of the input voltage (i.e.: HPF and THD > 30%), the Equation 1 becomes:

Equation 2

Where VILEDavg is the average voltage on the ILED pin, obtained by integration

(

ILED >> 1 / 2 *  * fIN) of the ILED current in an external capacitor.

Figure 4 shows the calculated and measured values of the voltage VILED vs. VIN with

VR = 102 V; the measurements are made on the board EVLHVLED815W10F at VOUT

nominal (22 V, VR = 102 V). The difference between the curves, when the VIN increases, is

due to increasing of switching frequency and then greater power transferred in valley

skipping (not TM) . Figure 5 shows the calculated and measured values of the voltage VILED

vs. VIN with VR = 70 V and VR = 122 V; the measurements are made on the same board

EVLHVLED815W10F changing the number of the LED and then VOUT and VR.

Figure 4. VILED at VR = 102 V (VOUT= 22 V)

Figure 5. VILED at VR = 70 V (VOUT = 15 V)

and VILED at VR = 122 V (VOUT = 26 V)

AN4496 Scheda tecnica(PDF) 4 Page - STMicroelectronics