AN2982 datasheet(20/31 Pages) STMICROELECTRONICS

Part #	AN2982

Description	This application note describes the STEVAL-ILB005V2 demonstration board equipped with the L6585DE lighting controller

PDF	31 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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20 / 31 page

Ballast stage design

AN2982

20/31

Doc ID 15599 Rev 1

2.4

End of life detection

In this design the blocking capacitor to ground configuration is chosen.

Figure 13.

Blocking capacitor to ground topology

The tracking configuration with a window of amplitude equal to 240 mV is selected,

connecting EOLP to ground with REOLP = 240 kΩ.

The EOL pin detects the blocking capacitor voltage by means of a voltage divider that, in

normal conditions, sets its voltage to the same value as the CTR pin:

Equation 50

Choosing the total upper resistor value equal to Reol1 = 1.36 MΩ (2x680 kΩ), and with the

steady-state value of the blocking capacitor voltage equal to Vout/2, the lower resistor is

calculated as:

Equation 51

A Ceol = 10 nF capacitor is used to filter the lamp frequency, maintaining the ripple. The

obtained cutoff frequency is calculated higher than 100 Hz, but lower than 49 kHz.

Equation 52

EOL

ctrh

ctrl

out

CTR

←

→

−

EOL

OUT

EOL

eol

eol2

20 k

796

eol

⋅

≈

AN2982 Datasheet(PDF) 20 Page - STMicroelectronics