| 摘要 |
An improved capacitive load driving device that provides increased signal voltage gain, over-voltage, over-current, and over-temperature protections, over-modulation prevention, output level control, minimized harmonic generation, and compensation for propagation medium distortion. The device includes driver/amplifier circuitry, protection circuitry, and an output stage. The driver/amplifier circuitry simultaneously modulates and discretizes an analog input signal by comparing it with a specified digitally-synthesized modulation waveform, which is a repeating series of approximately parabolic waveforms. The resulting PWM waveform is processed to generate a discrete low-harmonic sine wave approximation used to produce gate drive signals for the output stage. The protection circuitry monitors the device for fault conditions, and, in the event a fault condition is detected, controls startup and automatic shutdown. The output stage includes an H-bridge that drives an impedance-matching transformer feeding an inductor. When the device is used to drive a capacitive transducer, the impedance-matching transformer, the inductor, and the transducer form a series- resonant circuit for boosting the signal voltage gain, reducing power consumption, and filtering higher harmonics.
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