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L6615

keeping in mind that every Volt on the share bus will increase the master controller's supply current

by approximately 45

µA for each slave unit connected in parallel; this total current, provided by the

master share drive amplifier, must be lower than its minimum output capabilty (8mA) so

This condition is not tough to meet in normal applications, as one can easily see by using sensible

solving for N, we obtain Nmax=20;

– for safety reasons the following relation must be met:

At full load,

tems composed by N power supplies, each of them works at its nominal current, so:

This relationship is true also in N+M redundant system, even if under normal condition each power supply

For example in a system composed by two paralleled power supplies 100% redundant (N=M=1), each

module is sized to sustain the entire load current (in normal operation it carries only one half): for this rea-

son the sense resistor must be sized considering the whole load current.

The temperature variation of the sense resistor (hence of its resistance value) has to be taken into ac-

culated:

The effect of current sharing feedback loop is to force the voltages of the slave's CGA pins to be equal to

simplicity we consider 2 paralleled power supplies (as in fig. 11): under closed loop condition:

Ideally all the external component and

α are matched so:

Any mismatch will have repercussion on the sharing precision: in particular the maximum difference be-

tween the output currents (sharing error) will be given by the sum of the mismatches amongst the relevant

values.

V

SH MA X

()

R

iMIN

()

N

------------------- 8mA

⋅

<

R

G

1

2

---

V

out

10m A

----------------

40

–





⋅

>

I

OUT MAX

()

I

LOAD

N

----------------

=

R

CGA

R

G

---------------

V

SH MAX

()

V

SENSE MAX

()

-------------------------------------

=

I

OUT 1

()

R

SNS 1

()

R

G1

()

---------------------- R

CGA 1

()

⋅⋅

I

OUT 2

()

R

SNS 2

()

R

G2

()

---------------------- R

CGA 2

()

⋅⋅

=

I

OUT 1

()

I

OUT 2

()

I

LOAD

2

----------------

==