Class D amplifiers refer to Class D audio power amplifiers (sometimes called digital amplifiers). By controlling the ON / OFF of the switch unit, the amplifier driving the speaker is called a class D amplifier. Class D amplifiers were first proposed in 1958 and have gradually become popular in recent years. It has been in existence for many years. Compared with the general linear class AB power amplifier circuit, the class D power amplifier has the characteristics of high efficiency and small size.
Working principle of class d amplifierClass D amplifier design considerations are completely different from class AB amplifiers. At this time, the linearity of the power amplifier tube has no meaning, and the more important switch response and saturation voltage drop. Because the pulse frequency processed by the power amplifier tube is dozens of times that of the audio signal, and it is required to maintain good front and back edges of the pulse, the switching response of the tube is better. In addition, the efficiency of the whole machine is entirely due to the pipe consumption caused by the saturation pressure drop of the pipe. Therefore, the small pressure drop of the saturation tube not only has high efficiency, but also the heat dissipation structure of the power amplifier tube can be simplified. A few years ago, the price of such high-frequency high-power tubes was expensive, which limited the development of Class D amplifiers to a certain extent. Now MOSFETs with small current control and large currents have been widely used in the industrial field. Especially in recent years, UHC MOSFETs have been applied to Hi-Fi amplifiers, and the obstacles of the devices have been eliminated.
The modulation circuit is also a special link of class D power amplifier. To modulate the audio below 20KHz into a PWM signal, the triangle wave frequency must reach at least 200KHz. If the frequency is too low to meet the same requirements of the THD standard, the components of the passive LC low-pass filter are high and the structure is complex. The frequency is high, the sawtooth of the output waveform is small, which is closer to the original waveform, the THD is small, and the filter can be made with a relatively low value, small size and relatively low inductance and capacitance requirements, and the cost is reduced accordingly. But at this time, the switching loss of the transistor will increase with the increase of frequency. The high-frequency loss in the passive device and the skin effect of RF will reduce the efficiency of the whole machine. Radio frequency interference will also occur at higher modulation frequencies, so the modulation frequency cannot be higher than 1MHz.
At the same time, the shape of the triangular waveform, the accuracy of the frequency, and the jitter of the clock signal will all affect the distortion of the recovered signal and the original signal. So to achieve high fidelity, many of the same considerations as digital audio fidelity have emerged.
Another factor that has a lot to do with sound quality is the passive filter between the drive output and the load. The low-pass filter works under high current, and the load is the speaker. Strictly speaking, the change in speaker impedance should be taken into account in the design, but it is not feasible to specify the speaker as a power amplifier product, so there is a world of enthusiasts in the matching of class D amplifiers and speakers. It is actually proved that when the distortion requirement is below 0.5%, the second-order Butterworth flattest response low-pass filter can meet the requirement. If higher requirements are required, a fourth-order filter is required, and cost and matching issues must be considered.
In recent years, the general application of Class D amplifiers has integrated circuit chips, users only need to design low-pass filters as required.
What are the advantages and disadvantages of class d amplifiersClass D power amplifier advantages
Class D amplifiers have many advantages. Let me talk about them in detail.
1. Class d power amplifier has a very high energy use conversion rate, and its volume is very small, with strong reliability. The battery usage rate of class d power amplifier can reach more than 90%, which meets the requirements of environmental protection.
2. The use range of class d amplifiers is very wide. The minimum value of the connected load impedance can be very low. In addition, no matter how the load impedance value changes, the conversion rate of its battery can basically be said to be unchanged.
3. There is no relative change of high frequency, middle frequency and low frequency in class d amplifier, its sound is very clear, and the sound image has a very accurate positioning.
4. Class d power amplifier is very suitable for mass production of products. As long as the installation of the correct components is ensured, the product can have a good consistency, and it does not require any debugging during the production process, which is safe and reliable.
5. Class d power amplifier can directly realize functions such as group control, remote control and monitoring, without adding any devices.
Disadvantages of Class D power amplifiers
Although Class D power amplifiers have many advantages, they also have many shortcomings, and these shortcomings seriously affect the development of Class D power amplifiers. Let me specifically talk about the disadvantages of Class D power amplifiers.
1. There is no special switch for Class D power amplifiers. If the installed power transistors are not well matched with other devices, the quality of the entire product will be insufficient.
2. The power transistor of the Class D power amplifier will fluctuate during the beginning of the connection and the final shutdown process, and the potential close to the ground will increase the noise.
3. The output circuit of the Class D power amplifier may have dead zones.
4. The speaker of Class D power amplifier may be distorted for some reason.
The above is all the information collected by the editor about the advantages and disadvantages of the class d amplifier. If you want to learn more about the advantages and disadvantages of the class d amplifier after reading it, please log in to the Tubatu official website. I think there should be There is more knowledge about the advantages and disadvantages of Class D amplifiers.
CT For Management Terminal Unit
Our company`s current transformers have high precision,wide range,small volume and good linearity that can be used to the field of electronic watt-hour meter, electric energy metering, electronic detection.
Performance
â—Power frequency insulation strength:The insulation between the primary winding and the secondary winding and the ground part of the CT can bear 4kV power frequency voltage for 1minute
â—Interturn insulation strength:The secondary open circuit, the primary winding through the rated current 1min, no inter-turn damage in the transformer
â—The deviation is better than the industry standards and national standards
Management Terminal Unit Ct,New Design Current Transformer,Zero Phase Ct,Useful Residual Ct
Anyang Kayo Amorphous Technology Co.,Ltd. , https://www.kayoamotech.com