Automatic transition between PFM and PWM modes in a switching regulator

摘要

A method for transitioning between Pulse Frequency Modulation (PFM) mode and Pulse Width Modulation (PWM) mode and vice versa, in a switching regulator is disclosed. In PFM mode, load current is estimated based on slope of waveform of the output voltage of the switching regulator. If the load current is greater than an upper threshold, then the switching regulator is set to PWM mode. In PWM mode, load current is estimated using duration of dead-time. If the duration of dead-time is higher than a pulse filter trip point, the switching regulator temporarily transitions to PFM mode. The load current is further estimated based on slope of the waveform of the output voltage and, if the load current is lower than a lower threshold, the switching regulator remains in PFM mode. If the load current is higher than the lower threshold, the switching regulator transitions back into PWM mode.