This application relates to switching drivers which receive a supply voltage that can vary in use. An output stage switches a driver output node between switching voltages with a controlled duty-cycle and is operable in different driver modes in which the switching voltages are different in the different driver modes. A capacitive voltage generator is operable to generate a switching voltage used in one of the driver modes. The switching driver is operable a first regime, in which a capacitor of the voltage generator is biased to a capacitor voltage with a magnitude greater than the input supply voltage, or a second regime, where the biasing of the capacitor is different, such that the capacitor voltage magnitude has a ratio to the input supply voltage with a lower value than in the first regime. The regime is controlled based on the magnitude of the supply voltage and/or the capacitor voltage.