In some examples, a switch-mode power supply circuit comprises a pulse generation circuit comprising an oscillator, the oscillator configured to generate first pulses using a fixed frequency regulation for a first load condition that exceeds a predefined threshold and configured to generate second pulses using a variable frequency regulation for a second load condition that does not exceed the predefined threshold. The circuit also includes a power converter coupled to the pulse generation circuit and configured to convert a first voltage to a regulated voltage using either one of the first or second pulses generated by the pulse generation circuit. The circuit further comprises an output filter coupled to the power converter and configured to produce a second voltage from the regulated voltage.