A Spread Spectrum Modulation Method for Filter-free Digital Class-D Audio Power Amplifier

Abstract

The present invention proposes a spread-spectrum modulation method for a filter-free digital class D audio power amplifier, which utilizes the main clock signal of the power amplifier clk and UPWM generator input synchronous word clock signal clk_s 1 Synthesize another clock signal according to certain rules clk_s 2. Then build a pseudo-random number generator to generate a series of pseudo-random numbers, by judging the parity of the pseudo-random numbers, using the clock signal clk_s 1 and the clock signal clk_s 2 Synthesize a clock signal with variable frequency clk_c , and finally using the master clock signal clk , clock signal clk_c And the amplitude of the input signal of the UPWM generator is processed by the threshold calculator, counter and comparator to output the PRF variable left-increasing double-edge UPWM signal; at the same time, the corresponding filter-free pulse width modulator is designed based on the above-mentioned spread spectrum modulation method. The invention can obviously reduce the amplitude of the high-frequency component of the UPWM signal output by the power amplifier, thereby reducing EMI, and is simple to implement and requires less hardware resources.

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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