Интермодуляционные искажения в ключевых генераторах класса D с резистивной нагрузкой в режимах с переключением тока и мостовом

Abstract

The article is a continuation of the topic consideration of reverse intermodulation distortions analysis in class D switching generators with a resistive load. Similar to the approach used for the voltage-switched circuit in the previous authors work, a theoretical analysis of the reverse intermodulation distortion in class D current-switched circuit and in the bridge circuit is carried out. For both configurations, expressions for the output spectrum are written and the dependences of intermodulation distortion on non-ideal element parameters and operating modes are considered. A comparison of all three configurations of switching generators with a resistive load, while ensuring the intermodulation distortion level not exceeding minus 70 dB, showed that the circuit with voltage switching imposes the most stringent requirements for all influencing parameters. In it, the variation in the saturation resistance of the switches should not exceed 20%, and the total switches saturation time deviation in any combination should not exceed 0.01, which is 2% of 0.5T (from Pi). The current switching circuit allows a similar switches saturation time deviation, but the distortions in it do not depend on the switches saturation resistances difference. The switching bridge circuit allows for a 70% difference in switches saturation resistance. The permissible total saturation time deviation depends on the mode of operation and is 2.4% for overlapping and 18% for undercovering. The study allows developers of highly efficient switching generators to take into account one more parameter - resistance to induced electromagnetic radiation, in addition to the generally accepted achievable efficiency values, current and voltage crest factors, and resistance to load mismatch.