Driver circuitry and operation

A driver apparatus comprising:

• a first switching output stage for switching a first driver output node between a set of switching voltages with a controlled duty cycle,
• wherein the driver apparatus is operable in at least first and second modes of operation, wherein:
• in the first mode of operation the set of switching voltages comprise a first voltage and a second voltage;
• and
• in the second mode of operation the set of switching voltages comprise said second voltage and a third voltage;
• the driver apparatus further comprising a controller for controlling the mode of operation of the driver apparatus and the duty cycle of the first switching output stage based on an input signal;
• and wherein the controller is configured to transition between the first and second mode of operations from a present mode to a new mode by:
• controlling the driver apparatus in the present mode with a first duty cycle;
• controllably varying the set of switching voltages to the relevant voltages for the new mode of operation;
• and
• controllably varying the duty cycle of the first switching output stage, wherein the change in duty cycle is controlled such that there is substantially no discontinuity in switching ripple.

A driver apparatus for driving a transducer comprising:

• a first switching driver having a first driver output node for driving the transducer, wherein the first switching driver comprises a first output bridge stage for selectively switching the first driver output node between high and low switching voltages,
• a first modulator for controlling a duty cycle of switching of the first output bridge stage based on an input signal;
• and
• a first voltage controller for providing said switching voltages;
• wherein the first switching driver is operable in a plurality of driver modes of operation in which the first voltage controller is operable to provide different switching voltages in each driver mode;
• and the apparatus comprises:
• a controller for controlling the driver mode of operation and the duty cycle of the first switching driver based on the input signal, wherein the controller is configured to transition between said driver modes of operation from a present mode to a new mode by:
• controlling the first voltage controller to provide the switching voltages for the new mode;
• and
• controlling the first modulator to vary the duty cycle of the first output bridge stage, wherein the change in duty cycle is controlled such that there is no substantial discontinuity in switching ripple.