L6714 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
L6714
STMicroelectronics
'L6714' PDF : 70 Pages View PDF
L6714
21
System control loop compensation
System control loop compensation
The control loop is composed by the Current Sharing control loop (See Figure 8) and the
Average Current Mode control loop. Each loop gives, with a proper gain, the correction to
the PWM in order to minimize the error in its regulation: the Current Sharing control loop
equalize the currents in the inductors while the Average Current Mode control loop fixes the
output voltage equal to the reference programmed by VID. Figure 22 shows the block
diagram of the system control loop.
The system Control Loop is reported in Figure 23. The current information IDROOP sourced
by the DROOP pin flows into RFB implementing the dependence of the output voltage from
the read current.
Figure 22. Main control loop
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CURRENT SHARING
DUTY CYCLE
CORRECTION
IINFO1
IINFO2
IINFO3
IINFO4
L4
PWM4
L3
PWM3
L2
PWM2
L1
PWM1
ERROR AMPLIFIER
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COMP
ZF(s)
COUT
ROUT
VREF
IDROOP
FB
DROOP
ZFB(s)
The system can be modeled with an equivalent single phase converter which only difference
is the equivalent inductor L/N (where each phase has an L inductor).The Control Loop gain
results (obtained opening the loop after the COMP pin):
GLOOP(s) = –[---Z----P---(---s-P--)--W--+----M-Z---L---⋅(---s---Z)---]F---⋅-(--s----)--Z---⋅A-----F----(---((--s--Rs----)---)--D--+--R---O⎝⎛---1-O----+P-----+A---------(1-Z----s----P---)--⎠⎞(---s-⋅--)--)--R-----F---B----
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