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Christoph Haederli - Les thèses en ligne de l'INP - Institut National ...

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48 ML Converter Topologies<br />

Medium switching frequ<strong>en</strong>cy (f_base = 2kHz)<br />

Normalized total FC <strong>en</strong>ergy<br />

9<br />

8<br />

7<br />

6<br />

5<br />

4<br />

3<br />

2<br />

1<br />

0<br />

4 8 12 16 20 24 28 32 36 40 44 48<br />

N = levels - 1<br />

MC<br />

SMC<br />

ANPC 1 SCx+FCx<br />

ANPC 2 FCx+SCx<br />

ANPC 3 FCx+FCx<br />

M2LC<br />

Figure 43, Normalized total flying capacitor <strong>en</strong>ergy at medium switching frequ<strong>en</strong>cy (f base = 2 kHz)<br />

and average <strong>de</strong>vice switching frequ<strong>en</strong>cy limitation<br />

At a <strong>de</strong>vice switching frequ<strong>en</strong>cy of 2 kHz, the transition point where the M2LC becomes more<br />

favorable is at N=42. The appar<strong>en</strong>t output switching frequ<strong>en</strong>cy at this point is 84 kHz. For those<br />

values, output filtering is not a big issue any more for most applications. The <strong>de</strong>sign point for the<br />

switching frequ<strong>en</strong>cy is rather giv<strong>en</strong> by the effici<strong>en</strong>cy versus flying capacitor dim<strong>en</strong>sioning tra<strong>de</strong> off<br />

in this case.<br />

The transition point scales linearly with the switching frequ<strong>en</strong>cy. Accordingly, at 5 kHz, the<br />

transition point is expected around N=105.

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