A multiple-phase DC-DC converter has a first series circuit comprising first
and
second output transistors coupled across an input voltage, a first phase voltage
being provided at a first common connection between the first and second transistors,
at least one second series circuit comprising third and fourth output transistors
coupled in series across the input voltage, a second phase voltage being provided
at a second common connection between the third and fourth transistors, a first
output inductor for the first phase, at least one second output inductor for the
at least one second phase, an output capacitor, a first pulse width modulator circuit
comprising a first pulse width modulator comparator and a first fixed slope ramp
generator, the first fixed slope ramp generator supplying a fixed slope ramp signal
to one input of the first comparator, at least one second pulse width modulator
circuit comprising a second pulse width modulator comparator and a variable slope
ramp generator, the variable slope ramp generator supplying a variable slope ramp
signal to one input of the second comparator, an error amplifier for comparing
the output voltage of the converter to a reference voltage and providing an error
amplifier output voltage to respective second terminals of each of the first and
at least one second pulse width modulator comparators, a first current sense amplifier
for determining the phase current in a first phase of the converter provided by
the first series circuit, at least one second current sense amplifier for determining
the phase current in at least one second phase of the converter provided by the
at least one second series circuit and at least one share adjust amplifier for
receiving outputs from each of the first and second current sense amplifiers and
adjusting the slope of the variable slope ramp signal to adjust the current provided
by the at least one second series circuit thereby to equalize the currents provided
by the first and at least one second phases.
