Spread spectrum modulation method for filterless digital D class audio power amplifier

Abstract

The invention provides a spread spectrum modulation method for a filterless digital D class audio power amplifier. A power amplifier main clock signal clk and an UPWM generator are used input a synchronous word clock signal clk_s1, another clock signal clk_s2 is synthesized according to a certain rule, and then a pseudo random number generator is constructed to generate a series of pseudo random number sequences. By judging the parities of the pseudo random number sequences, the clock signal clk_s1 and the clock signal clk_s2 are used to form a frequency variable clock signal clk_c through synthesis, and finally a PRF variable left-growth double-edge UPWM signal is processed and outputted through a threshold calculator, a counter and a comparator by using the amplitudes of the main clock signal clk, the clock signal clk_c and the UPWM generator input signal. At the same time, a corresponding filter-free pulse width modulator is designed based on the above spread spectrum modulation method. According to the method, the amplitude of a high-frequency component of a power amplifier output UPWM signal can be obviously reduced, thereby an EMI is reduced, the implementation is easy, and few hardware resources are needed.

Description

technical field [0001] The invention relates to the technical field of filter-free digital class-D audio power amplifiers, in particular to a spread-spectrum modulation method for filter-free digital class-D audio power amplifiers. Background technique [0002] The digital class D audio power amplifier based on switch mode is widely used in today's audio power amplifier field because of its high power efficiency, convenient interface with digital audio sources, small size and many other advantages. The structural diagram of the traditional digital class D audio power amplifier is attached figure 1 As shown, including sequentially connected pulse width modulator, power stage and LC analog low-pass filter. In the traditional digital class D audio power amplifier, the input digital audio signal is first modulated into a switching signal through a pulse width modulator, then amplified by a high-power transistor in the power stage, and finally filtered through an inductor-capaci...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the technical problems that the existing spread spectrum modulation method has low applicability, high master clock frequency and low efficiency, the present invention proposes a spread spectrum modulation method for filter-free digital class D audio power amplifier, which can significantly reduce the power amplifier output The amplitude of the high-frequency components of the UPWM signal achieves the purpose of reducing EMI, and the implementation is simple, requiring less hardware resources for implementation

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