ISL6551_06 Datasheet, PDF (17/26 Pages) Intersil Corporation – ZVS Full Bridge PWM Controller

ISL6551
Figure 13 shows the block diagram of a power supply
system employing the ISL6551 full bridge controller. The
ISL6551 not only is a full bridge PWM controller but also can
be used as a push-pull PWM controller. Users can design a
power supply by selecting appropriate blocks in the “System
Blocks Chart” based on the power system requirements.
Figures 13A, 14A, 15A, 16A, 17A, 18A, 19, 20A, 21, 22A,
and 24A have been used in the 200W telecom power supply
reference design, which can be found in the Application Note
AN1002. To meet the specifications of the power supply,
minor modifications of each block are required. To take full
advantage of the integrated features of the ISL6551,
“secondary side control” is recommended.
V_IN
INPUT
FILTER
PRIMARY
FETs
CURRENT
SENSE
PRIMARY FET
DRIVERS
BIASES
MAIN
TRANSFORMER
ISL6551
CONTROLLER
SUPERVISOR
CIRCUITS
PRIMARY BIAS
SECONDARY BIAS
RECTIFIERS
SECONDARY
DRIVERS
FEEDBACK
OUTPUT
FILTER
V_OUT
FIGURE 13. BLOCK DIAGRAM OF A POWER SUPPLY SYSTEM USING ISL6551 CONTROLLER
System Blocks Chart
Input Filters
V_IN
V_INF
C_IN
FIGURE 13A. GENERAL
L_IN
V_IN
V_INF
C_IN
General - Input capacitors are required to absorb the
power switch (FET) pulsating currents.
EMI - For good EMI performance, the ripple current that is
reflected back to the input line can be reduced by an input
L-C filter, which filters the differential-mode noises and
operates at two times the switching frequency, i.e., the
clock frequency (Fclock). In some cases, an additional
common-mode choke might be required to filter the
common-mode noises.
FIGURE 13B. EMI
17
FN9066.5
January 3, 2006