Design of surface acoustic wave filters for the multiplex transmission system of multilevel inverter circuits

We designed surface acoustic wave (SAW) filters for a multiplex transmission system of multilevel inverter circuits, and applied them to a singlephase three-level inverter. To reduce the transmission delay time of the SAW filters, a four-channel SAW filter array was fabricated and its characteristics were measured. The delay time of the SAW filters was < 350 ns, and the delay time difference was reduced to <= 184 ns, less than half that previously reported. The SAW filters withstood up to 990V, which is sufficient for the inverters used in most domestic appliances. A singlephase three-level inverter with the fabricated SAW filters worked with a total delay time shorter than our target delay time of 2.5 mu s. The delay time difference of the proposed system was 0.26 mu s, which is sufficient for preventing the inverter circuit from short-circuiting. The SAW filters controlled a multilevel inverter system with simple signal wiring and high dielectric withstanding voltages. (C) 2017 The Japan Society of Applied Physics