US Patent 7852127 Driving circuit for capacitive load and fluid injecting device

A driving circuit that drives a capacitive load includes a drive signal generator that generates a drive signal that drives the capacitive load via a transistor pair in response to an analog signal. A power-source voltage generator generates high-voltage and low-voltage power-source voltages and supplies the power-source voltages to collectors of the transistors via a high-voltage output terminal and a low-voltage output terminal. The power-source voltage generator includes multiple power sources connected in parallel and a switch unit that connects the adjacent power sources in series each time the drive signal rises above or falls below a predetermined threshold value. The driving circuit further includes a voltage controlling capacitor connected to the low-voltage output terminal of the power source, and a power recovery unit having a switch unit that recovers a charge accumulated in the voltage controlling capacitor back to the power source via the high-voltage output terminal.