The capacitor filter rectifier power supply used in general high fidelity audio power amplifiers must use a large capacity transformer to ensure high performance, so the power system has problems such as large volume, heavy weight, and high cost. A well-designed linear regulated power supply has high performance and can to some extent reduce the quality of the power system. However, due to the need for high-quality components in the voltage regulator circuit, this will further reduce the cost-effectiveness of the power supply. Meanwhile, the power transistor in the voltage regulator circuit consumes a large amount of power due to its operation in the amplification region, which can lead to a decrease in the efficiency of the power supply system.

High frequency switching power supplies (hereinafter referred to as switching power supplies) have the characteristics of small size, light weight, and high efficiency, and have therefore been widely used in electronic products. However, due to the unsatisfactory performance of general switching power supplies in audio power amplifiers, they have not been widely used in high fidelity audio power amplifiers.

Thoroughly analyzing the reasons for the poor performance of switching power supplies in audio power amplifiers is the key to developing audio specific switching power supplies. Practice has proven that switch mode power supplies designed with targeted measures based on the special requirements for audio power amplifier power supplies and the characteristics of switch mode power supplies have performed very well in audio power amplifiers. Both experiments and subjective listening evaluations indicate that it can completely replace other forms of power supplies as the mainstream power supply for high fidelity audio power amplifiers.

Electromagnetic interference from switch mode power supplies is not the main contradiction

It is generally believed that electromagnetic interference from switch mode power supplies is the main factor affecting their sound quality performance

However, through the analysis of these interfering frequency components, it can be found that this is actually a misunderstanding.

There are various reasons for the formation of electromagnetic interference in switch mode power supplies, mainly including the following aspects:

(1) Electromagnetic interference of input circuit

After rectification and filtering, AC power is supplied with energy in the form of short conduction time and high peak value pulse current. This pulse current contains a series of harmonic components. These harmonic components will generate conducted and radiated interference along the transmission circuit. However, this interference is not unique to switching power supplies, it also occurs in general capacitor filtering rectifier circuits that use power transformers. Therefore, this is not the main interference of switching power supplies.

(2) Electromagnetic interference generated by switch circuits

The electromagnetic interference generated by switch circuits is one of the main sources of interference in switch power supplies. The power conversion transistor of a switching power supply operates in a high current switching state, and its conversion waveform is a rectangular wave. Due to the rich odd harmonics of rectangular waves, unique harmonic interference is generated.