An energy regenerative active vibration control method using piezoelectric actuators and class D amplifiers is proposed by the authors. Class D amplifiers can amplify signals with little power loss and regenerate powers from loads including actuators. Class D amplifiers usually consist of PWM modulators, class D drivers and output filters. PWM modulators generate PWM signals modulated by input signals. Class D drivers amplify PWM signals and output filters extract amplified input signals from amplified PWM signals. The reason of the indirect amplification process is that binary signals like PWM signals can be amplified by switching with little power loss. Binary signals can be considered as relay type non-linear inputs often used in sliding mode control. In this paper, a sliding mode controller is designed for a system including a mechanical SDOF oscillator, a piezoelectric actuator and an output filter. The controller generates a relay type non-linear input as a binary input signal for the class D driver without PWM modulator. The operation of the method is confirmed by numerical simulations.