| With the development of high-speed magnetic bearing, the higher requirements of power amplifier are raised including high performance and high efficiency. Switching power amplifier is popularly used because of its virtues of low power losses, high efficiency and high frequency bandwidth.The standard current controlled bi-state PWM switching power amplifier has its intrinsic deficiencies, such as significant harmonic distortion and restriction of the dynamic characteristic, which have serious negative effects on the magnetic bearing system. To overcome these drawbacks, the application of current controlled tri-state PWM technology to the switching power amplifier is proposed, which can provide better dynamic response combined with lower harmonic distortion. This paper describes the general design rules of switching power amplifier and analyses different control strategies. Simulation comparisons verify the superior performance of the tri-state PWM technology. Experimental results indicate that the current-controlled tri-state PWM switching power amplifier based on sample-hold strategy has high frequency bandwidth and fast dynamic response in a wide load range, which can well meet the demands of high-speed magnetic bearing.
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