17.1 An integrated 80V 45W class-D power amplifier with optimal-efficiency-tracking switching frequency regulation

Piezoelectric actuators are widely used in smart materials for vibration and noise control, precision actuators, etc. [1]. These actuators are largely capacitive and the reactive power applied on them can go to several tens of Watts. Highvoltage, high-power class-D amplifiers [2]-[5] are ideal drivers for such loads, because of their high power efficiency. Preferably, efficiency should be high both at maximum power and at average output power. Obtaining high power efficiency over the full output power range of a class-D amplifier is the main focus of this work.