AN2870 datasheet(34/41 Pages) STMICROELECTRONICS

34 / 41 page

Designing with L6585DE

AN2870

34/41

Equation 49

These charges must be replaced during the subsequent ON time of the low side transistor:

Equation 50

End of life detection

Blocking capacitor to GND configuration

In case of blocking capacitor to ground configuration the tracking mode is suggested. In

order to set this mode a resistor placed between EOLP and GND is needed: its value has to

be chosen as follows:

●

220 k

Ω < R

eolp < 270 kΩ → VW = 240 mV

●

22 k

Ω < R

eolp < 27 kΩ → VW = 150 mV

EOL pin biasing proceeds as follows:

The blocking capacitor mean voltage is half of the PFC output voltage and the CTR pin

voltage is equal to:

Equation 51

Therefore the voltage divider connected between Cblock and EOL pin should have a divider

factor equal to:

Equation 52

A capacitor placed in parallel with the lower resistor and placed near the IC helps to keep

low the high frequency residual noise.

boot

gate

−

min

DeadTime

pre

boot

⎟

⎠

⎞

⎜

⎝

⎛

−

⋅

⎥

⎦

⎤

⎢

⎣

⎡

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛ Δ

−

⋅

−

OVP

out

CTR

⋅

OVP

out

CTR

eol

⋅

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