Abstract: In response to the stringent requirements of high current and low ripple for switching power amplifiers in active magnetic bearings of heavy industrial equipment, this paper proposes a design scheme based on multi power device parallel topology and three-level modulation strategy. By paralleling power devices, the current output capability of the circuit has been improved and the conduction loss has been reduced; relying on the high-speed computing capability of DSP processors, a three-level modulation strategy is adopted to reduce output current ripple. Based on the above scheme, this article developed a switching power amplifier with a bus voltage of 150 V, a switching frequency of 20 kHz, and a maximum sustainable output current of 25 A, and conducted performance tests on it. The test results show that the developed switching power amplifier can continuously output 25 A current for a long time and has excellent static and dynamic operating performance, improving the high load carrying capacity and long-term reliability of active magnetic bearings.