AN4496 datasheet(8/18 Pages) STMICROELECTRONICS

Part #	AN4496

Description	How to get a high power factor with the HVLED815PF device

PDF	18 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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8 / 18 page

ILED pin

AN4496

8/18

DocID026370 Rev 1

Figure 7. Equivalent pin ILED modulation circuitry in low input voltage range

In the high range (185 V - 265 V) the transistor Qr is saturated and the circuit in Figure 6

becomes as that in Figure 8. The value of KACH is from Equation 9:

Equation 14

Where VINminH is the high range minimum RMS input voltage and the value used for  and

Vdrp are the values at the VINminH.

The value of Rpc + Rpe to obtain the selected value of KACH the will be:

Equation 15

The resistors Rr1, Rr2 and Rr3 implement a voltage divider. In parallel to the Rr3 is placed

a capacitor Cr3 that filters the voltage ripple. When this voltage is greater than the sum of Dr

Zener voltage (VZ_Dr) and the base - emitter voltage of Qr (VBE_Qr), the transistor Qr starts

to switch on. The emitter resistor reduces the gain of Qr and permits a linear transition

between the low and the high range, that allows to work without hysteresis and reduces the

THD in the transition range (132 V -175 V).

AN4496 Datasheet(PDF) 8 Page - STMicroelectronics