Methods and apparatus are disclosed for controlling switching regulators
to automatically switch from a traditional pulse-width modulation (PWM)
mode, when the load current is higher than a predetermined value, to a
pulse-frequency modulation (PFM) mode, when the load current drops to a
point lower than the predetermine value. Switching modes increases the
efficiency of the regulator when the load current is low without
provoking a large output voltage transient. In some embodiments, a single
switching cycle regulates the output in the PFM mode, which reduces the
switching losses and enhances the efficiency of the regulator.