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| AN4496 Datasheet, PDF (16/18 Pages) STMicroelectronics – How to get a high power factor with the HVLED815PF device | |||
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Designing a high PF wide range LED driver with the HVLED815PF
2.9
OVP protection
In Section 2.1 on page 10 the selected value VOUT_OVP = 29 V, then:
Equation 35
AN4496
Real value used:
Rfb = 16kï
2.10
AC modulation
To obtain the high power factor and low THD, a signal proportional to rectified mains is
applied to the ILED pin.
The other components of the network that switching the range can be calculated, but the
non-linear behavior of Qr due the modulation of the Qr collector requires a fine tuning of the
network; using the next recommended value for the components, the only value to be
calculated is R3 to optimize the modulation at 85 - 90 V.
Equation 36
With:
Rp1 = Rp2 = 180 kï
Rps = 120 kï
Rpc = 51 kï
Rpe = 15 kï
Rr1 = Rr2 = 120 kï
Rr3 = 62 kï
Cr3 = 4.7 µF
Dr = BZV55-C20
Qr = MMBTA42
16/18
DocID026370 Rev 1
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