08-16-2017, 10:55 PM
In recent years the usefulness of interleaving
power stages has become apparent. The best
known application is in powering
microprocessors, commonly referred to as
voltage regulator modules (VRMs). In VRM
applications, the converters are non-isolated from
input to output. This paper presents the benefits
of interleaving power stages for isolated
applications. It shows that the two-inductor (2L)
interleaved forward converter topology or the
interleaved flyback converter topologies are
appropriate choices for many high-power
applications.
The forward converter shown in Fig. 1 is one
of the most studied topologies. Derived from the
simple buck converter, the forward converter
delivers energy from the input source to the
output filter inductor during the on time of the
main switch. In contrast, the flyback converter
shown in Fig. 3 delivers energy to the output
filter capacitor only during the off-time of the
main power switch. This different power transfer
characteristic has a dramatic impact on the
transfer function and the power levels at which a
flyback converter is applicable.
The concept of interleaving enables these
converter topologies to operate at increased
power levels. The benefits of interleaving
include:
Reduced RMS current in the input capacitors
enabling the use of less expensive and fewer
input capacitors
Ripple current cancellation in the output
capacitor, enabling the use of less expensive
and fewer output capacitors
Reduction of peak currents in primary and
secondary transformer windings (2L
interleaved forward converter)
Improved transient response as a result of
reduced output filter inductance and higher
output ripple frequency
Separation of heat generating components
allowing for reduced heatsink requirements.
Improved form factor for low profile
solutions
Reduced EMI as a result of reduced peak
currents (2L interleaved forward converter)
