The power amplifier is the power conversion and power driving device of the electrodynamic shaker. It has two functions:
(1) Provide high-power DC excitation power to the excitation coil, so that the excitation coil becomes a magnet with high magnetic energy product, and in conjunction with it A high intensity magnetic flux density is formed in the connected ferromagnetic materials and the air gap.
(2) Amplify the low-power vibration signal transmitted from the signal source and send it to the drive coil to achieve high-thrust vibration.
According to the above two functions, there are two requirements for the power amplifier:
(1) Must have high transmission efficiency. That is, the power amplifier’s own loss is very small;
(2) Very small nonlinear distortion. That is, the power of the output signal of the power amplifier is amplified, but the waveform and phase must be consistent with the input signal.
Traditional power amplifiers are analog power amplifiers that use electron tubes or high-power transistors. This type of power amplifier directly amplifies analog signals when working. The switching tube must work in the linear amplification area. The waveform distortion is small, but the power loss is large. Among them, Class A analog traditional power amplifier has the lowest efficiency, only about 25%. The efficiency of Class B traditional power amplifiers can be increased to about 55%, but the distortion will also increase a lot. Class AB efficiency can be improved
As high as 40%, the waveform distortion is improved compared to Class B. However, no matter what measures are taken, the transmission efficiency of this type of power amplifier is difficult to exceed 60%, causing useless power to be converted into a large amount of heat, which adds a lot of burden to the cooling of the power amplifier. In order to improve the transmission efficiency of electrodynamic shaker, most ED shaker in active use basically use switching power amplifiers. Compared with traditional power amplifiers, the switching tube works in the switching state, and the theoretical efficiency can reach 100%. In actual use The efficiency can also reach more than 80%. Due to the inherent nonlinearity of the switching converter itself, the distortion of the switching power amplifier is usually greater than the traditional analog efficiency operating in the linear amplification region. However, switching power amplifiers are widely used in ED shaker that require high power conversion and want low power consumption.