A study for active filter using operating amplifier without harmonics of switching frequency

Active filter (AF) is a good solution for eliminating harmonics from switching devices. But, many types of AF are composed of switching devices itself Still more, in order to compensate harmonics with AF sufficiently, we need to increase switching frequency of inverter. This increases the switching losses of de-vices. In addition, this may cause new harmonics or EMI to the A C line. In this paper, we proposed a new type AF. This AF consists of power operating amplifier with resonant circuit and partial-switching-type AF. Power operating amplifier has an advantage of generating no harmonics, but a disadvantage at the point of efficiency. Therefore, we use resonant circuit for reducing the capacity of operating amplifier. Furthermore, we combined this with partial-switching-type AF for much more decreasing the capacity. As this type AF has very low switching frequency (2 times switching in one source voltage period in this case), the conversion efficiency of this system is very high. But, as this type AF has been developed for specific load such as home electronic applications, the control method of applying for various load has not been established. Therefore, we proposed the method for adapting these loads in this paper By using simulation and experimental results, we represents that this system can be in practical use.