A method and apparatus for use in a multi-phase power system. The power
system is of the type having a plurality of Pulse Width Modulation (PWM)
controllers including a first PWM controller and at least one second PWM
controller. The first PWM controller generates at least one first PWM
output signal based on a cyclic signal having a cyclically recurring
parameter, and provides the cyclic signal including the cyclically
recurring parameter to the second PWM controller. The second PWM
controller generates at least one second PWM output signal based on the
cyclic signal, and synchronizes the generation of the first and second
output signals using the cyclically recurring parameter within the cyclic
signal, thereby maintaining a predetermined phase relationship between
the first and second output signals. The second PWM controller generates
a cyclic, triangular RAMP waveform signal having a series of periods, the
RAMP waveform having in each period a signal rising portion and a signal
falling portion, and compares the RAMP waveform against an error signal
to generate the second PWM signal, the RAMP waveform rising portion and
falling portion being generated by charging and discharging,
respectively, a capacitor. A feedforward path is provided by setting a
charging current for the capacitor that is proportional to an input
voltage.