Low Noise ZVS Switch Sharing Multichannel Switching Amplifier for Magnetic Bearing Applications

In a magnetic bearing system, the levitation coils or electromagnets must be driven by an amplifier in order to control their currents for levitation stability. This amplifier typically drives every coil individually with hard-switching H-bridges. However, the inherent high dv/dt of hard-switching in conjunction with the large parasitic capacitance of magnetic bearing coils typically results in high current spikes and severe ringing in the switching process, which may interfere with position sensors and system communication. Furthermore, driving each coil individually requires a large number of switches. In this brief, a switch sharing zero-voltage-switching (ZVS) multichannel switching amplifier topology is proposed, which not only reduces the number of switches needed when driving multiple coils, but also eliminates current spikes and reduces the switching loss of the magnetic bearing amplifier. The proposed topology is experimentally tested to validate expected benefits.