AN2870 datasheet(31/41 Pages) STMICROELECTRONICS

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AN2870

Designing with L6585DE

31/41

Equation 38

And the power rating to:

Equation 39

The real maximum inductor current and lamp voltage can be calculated considering the

maximum threshold value and the tolerances related with value of Rhbcs and Lres.

The design of the inductor proceeds as indicated in Eq 7.

The resonance capacitor is preferably a metallized polyester film capacitor. Blocking

capacitor is around ten times the resonant one: a value greater or equal to 100 nF for the

polyester capacitor is usually chosen.

Parameters setting

In order to fix the run frequency and the preheating frequency, the following curves can be

used. Each curve is related with a particular capacitor value, therefore a capacitor value

must be firstly chosen. The resistances corresponding Frun and Fpre can be graphically

found and are respectively Rrun and the parallel between Rrun and Rpre.

Figure 16.

Oscillator characteristic curves

lamp

RMS

hbcs

≈

hbcs

RMS

hbcs

⋅

≈

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