Closed loop charge mode drive for piezo actuators using a DC restore amplifier

摘要

A piezo actuator drive circuit (40) adapted to operate in both a charge mode and a voltage mode. A low frequency compensation loop (44) is formed from a piezo actuator output (OUT6XP) of a driver (42) to the input thereof. The resulting closed loop system produces charge mode operation within a bandpass that can be tuned for desired operation. Below the bandpass turn on frequency (Fh) the closed loop system restores the piezo output (OUT6XP) to a defined DC voltage and compensates for any wandering effects, such as DC current mismatches in the closed loop configuration, such that the piezo output is centered around the desired DC operating point. The circuit is further provided with a DC restore feature in combination with the feedback which allows for a low frequency DC coupled path and thus allows for the DC positioning of the piezo in the charge mode to be changed. The DC restoring amplifier is used to compensate for offsets in the amplifier chain. The DC restore amplifier ensures the overall circuit is balanced and that the charge mode operation is maintained. The circuit is particularly adapted to drive a varying number of multiple piezo actuators.