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Frequency switching circuit for restraining the D power amplifier POP sound and its method

A power amplifier, frequency switching technology, applied in amplifiers, improving amplifiers to reduce the impact of noise, amplifiers with semiconductor devices/discharge tubes, etc. Simple effects of sound and circuit changes

Inactive Publication Date: 2009-03-18
APEXONE MICROELECTRONICS SHANGHAI +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Before the start-up, the output levels of both sides of the power switch tube are 0, and at the start-up time, one side will first jump from 0 to 1, such as Figure 7 As shown, it is the waveform diagram when PWM waves A and B start to oscillate, and the jump from 0-1 will generate POP sound, which affects the sound playback effect to a certain extent
[0005] Therefore, it is necessary to invent a technology to overcome and suppress the defect that the existing class D amplifier will produce POP sound

Method used

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  • Frequency switching circuit for restraining the D power amplifier POP sound and its method
  • Frequency switching circuit for restraining the D power amplifier POP sound and its method
  • Frequency switching circuit for restraining the D power amplifier POP sound and its method

Examples

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no. 1 example

[0018] figure 1 is the first embodiment of the present invention, a schematic diagram of the frequency switching circuit when the power is turned on.

[0019] figure 2 It is a schematic diagram of another way to generate high-frequency oscillation in the second embodiment of the present invention.

[0020] image 3 It is a schematic diagram of the frequency switching circuit when the power is turned off in the present invention.

[0021] Figure 4 It is a principle schematic diagram of a class D power amplifier in the prior art.

[0022] Figure 5 It is a schematic diagram of an output stage of a class D power amplifier in the prior art.

[0023] Figure 6 It is a reverse PWM waveform diagram output by a switch tube of a class D power amplifier in the prior art.

[0024] Figure 7 It is a schematic diagram of a situation of the reverse PWM waveform output by the Class D power amplifier at the start-up moment in the prior art, and B is the waveform that jumps first. ...

Embodiment approach

[0026] Referring to the accompanying drawings, the technical solution of the present invention will be further described for the case of two reversed PWM waveforms.

[0027] The main idea of ​​the present invention is to suppress the POP sound by switching two PWM signals with different frequencies. Since the POP sound can only be generated when the PWM signal starts or ends, and because the size of the POP sound is related to the width of the first pulse when the PWM signal starts to oscillate, the wider the first pulse, the generated POP sound The bigger it is, on the contrary, the smaller the POP sound will be. Therefore, the present invention suppresses the generation of POP sound by switching two PWM signals with different frequencies when the power is turned on or off. Please see figure 1 , is the first embodiment of the present invention, including a comparator 10, an inverter 12, an H-bridge power switch tube, and a high-frequency PWM signal device (not labeled). T...

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Abstract

In the invention, the HF-oscillating PWM wave is generated by self-oscillation; before starting power, the HF-oscillating PWM wave is oscillated with high starting frequency; thereby, the first PW is small and ignored; after some periods, it switches to LF to start oscillation by a MOS switch, now the first wide pulse noise is very low; the process when turning off power is similar. This invention can inhibit POP sound when turning on or off the power.

Description

【Technical field】 [0001] The invention relates to a frequency switching circuit and a method thereof, in particular to a frequency switching circuit and a method applied to a class D power amplifier. 【Background technique】 [0002] With the digitalization of audio systems and the marketization of portable products, Class D power amplifiers have been widely accepted by the market as a substitute for analog power amplifiers. Its biggest feature is that it can get the highest efficiency while maintaining the lowest distortion. [0003] Class D amplifiers use pulse-width modulation (PWM) technology, a method of digitally encoding the level of an analog signal. Through the use of high-resolution counters, the duty cycle of the square wave is determined. Modulation is used to encode the level of a specific analog signal to adjust the width of a series of rectangular pulses. Any analog value can be encoded using PWM as long as the bandwidth is sufficient. The output PWM signal d...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03F1/26H03F3/217H03K17/687H03K17/284
Inventor 鲍圣坤任永青朱昊
Owner APEXONE MICROELECTRONICS SHANGHAI