A Design Of Digital Amplifier Module Based On Generalized Predictive Control

With the rapid development of microelectronic technology and semiconductor technology, miniaturization, modularization and integration of electronic Products have become the mainstream trend. And the power amplifiers also have been updated constantly. The developed and perfected techniques of audio modulation and digital compensation has significantly improved and enhanced the Class D amplifier's tone quality. And gradually replacing analog amplifier, digital power amplifier will become the market leader by means of low power consumption and small size. However in the field of high-end professional applications, digital amplifier's performance cannot meet the requirements. Therefore, when we are in pursuit of lower power consumption, high-power and small size, designing a high fidelity digital amplifier become the main research. Research of this subject is to design a new class D amplifier to maintain high-quality audio signals while achieve both lower power consumption and high power performance.By consulting a large number Literatures, I introduce the current class about linear power amplifiers and nonlinear analog digital amplifier and compare their advantages and disadvantages, highlighting the D class amplifier's advantage especially. In the meanwhile, the working principle of conventional digital amplifier is illustrated, and then this paper leads to the new design of digital power amplifier. In consideration of the rapid development of domestic and international automotive industry and the entertainment requirements when people drive cars , the digital power amplifier application in the field of car audio is described emphatically.Based on the principle of new digital power amplifier, this paper proposes to use the generalized predictive control algorithm to improve system performance, and establishes the digital amplifier system's state equation model based on generalized predictive control algorithm.The system includes signal processing module, drive circuit, power switching stage circuit, the output filter and the feedback signal detection circuit. DSP takes the detected feedback voltage and current signals and the audio signal as input signals, then calculates the output of the PWM duty using the generalized predictive control algorithm. The PWM signal can be amplified by the drive module and switch-level. The PWM pass through the low-pass filter circuit which consist of L and C components, and then drive the high-power load. The feedback of voltage and current signals from the low-pass filter will be converted to digital form by an ADC. By Configuring and debugging the DSP's multi-channel buffered serial interface (MCBSP) and the PWM module, DSP can be ensured to receive data and output PWM signal correctly.The Cadence software's Pspice tool is used to design and simulate the former level analog signal amplifier circuit. The results of simulation show that the analog amplifier circuit can maintain a good frequency response to meet system design requirements. At the same time, the model is simulated by making use of Matlab software to verify the generalized predictive control algorithm which can suppress noise and reduce the power switch time, the detection errors of voltage and current and component parameter drifts to impact on output, to hit the target that this algorithm can reduce the distortion of the system and improve the digital amplifier sound quality.