A switching amplifier with an H-bridge drive was developed for self-sensing magnetic suspension. In this amplifier, switching times are controlled by a current comparator with a small hysteresis. The amplifier implemented with such hysteresis control has asynchronous characteristics so that the switching rate depends on the load impedance. When the hysteresis amplifier is used for magnetic suspension, the gap between the suspended object and the electromagnet can be estimated from the switching frequency. Since the Hbridge reverses the polarity of the voltage applied to the coil alternatively, the switching frequency is insensitive to the value of current command to the amplifier. The F/V conversion of the switching signal was used for feedback control with the result that self-sensing suspension was achieved.
A current-comparator-based high-voltage reference inductor