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

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ML Converter Topologies 41<br />

f<br />

C<br />

sw<br />

= k f<br />

(12)<br />

I<br />

f _ sw<br />

*<br />

NT<br />

sw _ base<br />

I<br />

N<br />

I<br />

FC _ max SP FC _ max<br />

FC _ max<br />

0<br />

= =<br />

=<br />

(13)<br />

Mk1U<br />

DC<br />

Mk1U<br />

DC<br />

fsw<br />

Mk1U<br />

DC<br />

f<br />

sw _ basek<br />

f _ sw<br />

I<br />

FC _ max<br />

IFC<br />

_ maxN<br />

Mk<br />

f _ sw<br />

Mk<br />

f _ sw<br />

C1 = =<br />

= C0<br />

(14)<br />

k U f Mk U f N N<br />

1<br />

DC sw _ base<br />

1<br />

DC<br />

sw<br />

N<br />

C = 0<br />

C1<br />

(15)<br />

Mk f _ sw<br />

N<br />

C 0 refers to the actual capacitance required, taking into account the level over interleaving and<br />

the applied switching frequ<strong>en</strong>cy. C 1 is a g<strong>en</strong>eric value <strong>de</strong>p<strong>en</strong>ding on maximum curr<strong>en</strong>t, maximum<br />

voltage ripple and base switching frequ<strong>en</strong>cy. It can be se<strong>en</strong> from (15) that a reduction of the<br />

number of cells can be comp<strong>en</strong>sated with higher switching frequ<strong>en</strong>cy. With a total number of k<br />

flying capacitors, we get the total <strong>en</strong>ergy in the flying capacitors:<br />

E<br />

tot<br />

=<br />

k<br />

∑<br />

x=<br />

1<br />

C0U<br />

2<br />

2<br />

x<br />

=<br />

k<br />

∑<br />

C1NU<br />

2Mk<br />

2<br />

x<br />

x=<br />

1 f _ sw<br />

(16)<br />

A constant shall be <strong>de</strong>fined as follows to compare differ<strong>en</strong>t topologies without taking into<br />

account any absolute values from a giv<strong>en</strong> operating point.<br />

E<br />

tot<br />

I<br />

U<br />

2<br />

C1U<br />

DC<br />

FC _ max DC<br />

= K<br />

E _ cap<br />

= K<br />

E _ cap<br />

(17)<br />

2<br />

2k1<br />

f<br />

sw _ base<br />

(18) follows directly from (16) and (17).<br />

2<br />

k<br />

2E<br />

⎛ ⎞<br />

tot<br />

N U<br />

x<br />

K<br />

_<br />

= =<br />

2 ∑<br />

⎜<br />

⎟<br />

E cap<br />

(18)<br />

C1U<br />

Mk<br />

DC<br />

f _ sw x=<br />

1 ⎝U<br />

DC ⎠<br />

In the case of p groups of flying capacitors with each group forming a MC, this can also be<br />

writt<strong>en</strong> as (k/p is the number of flying capacitors per group):<br />

∑∑<br />

− 2<br />

p 1 k / p<br />

N ⎛U<br />

y+<br />

x*<br />

k / p ⎞<br />

K<br />

E _ cap<br />

=<br />

⎜<br />

⎟<br />

(19)<br />

Mk<br />

f _ sw x= 0 y=<br />

1 U<br />

DC<br />

⎝<br />

⎠<br />

With p id<strong>en</strong>tical groups of flying capacitors this results in:<br />

2<br />

k / p<br />

pN ⎛ U<br />

y ⎞<br />

K<br />

_<br />

= ∑<br />

⎜<br />

⎟<br />

(20)<br />

E cap<br />

Mk<br />

f _ sw y=<br />

1 ⎝U<br />

DC ⎠

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