Driver circuits

A driver circuit comprising a first switching driver for driving a transducer, the first switching driver comprising:

• an output stage comprising a first driver output node for outputting a first driver signal to drive the transducer and first and second switches for selectively connecting the first driver output node to respective first and second controlled voltage nodes;
• and
• a voltage stage configured to control voltages at the first and second controlled voltage nodes;
• wherein the first switching driver is configured to be operable in at least first and second modes to modulate the first driver output node between different voltages with a controlled duty-cycle in a switching cycle, wherein:
• in the first mode, the first and second switches are switched with the controlled duty-cycle so that the first driver output node is connected to the first controlled voltage node for part of the switching cycle and is connected to the second controlled voltage node for a different part of the switching cycle;
• and
• in the second mode, the first switch is closed, with the second switch open, throughout the switching cycle, so that the first driver output node is connected to the first controlled voltage node throughout the switching cycle and the voltage stage modulates the first controlled voltage node between different voltages with said controlled duty-cycle.

A driver circuit comprising:

• a first output stage with a first driver output node for outputting a first drive signal for driving a load and at least first and second switches for selectively connecting the first driver output node to respective first and second controlled voltage nodes;
• and
• a voltage stage configured to control voltages at the first and second controlled voltage nodes;
• the driver circuit being operable in:
• a first mode in which the first and second switches are repeatedly switched with a controlled duty-cycle to alternately connect the first driver output node to different voltages at the first and second controlled voltage nodes;
• and
• a second mode in which the first switch is maintained closed and the second switch is maintained open and the voltage stage alternates the first controlled voltage node between different voltages with a controlled duty-cycle.

A driver circuit comprising:

• a first output stage with a first driver output node for outputting a first drive signal for driving a load and at least first and second switches for selectively connecting the first driver output node to respective first and second controlled voltage nodes;
• the driver circuit being operable in;
• a first mode in which the first switch is switched with a controlled duty-cycle in a switching cycle and a voltage at the first controlled voltage node is held at a constant nominal value when the first switch is closed;
• and
• a second mode in which the first switch is closed throughout the whole of the switching cycle and the voltage at the first controlled voltage node is modulated between different nominal values when the first switch is closed.