The interleaved operation of power amplifiers

Multi-level power stages and control techniques have been developed to increase power converter operating voltage levels above the voltage ratings of available power semiconductor switches, and also improve output waveform resolution. The multilevel power conversion idea, however, may also be adopted more generally in high-power amplifiers. In amplifiers based on the single-phase inverter topology, or H-bridge, this is most easily accomplished by the direct series, or parallel, connection of multiple H-bridge power-stages. Operating these with interleaved PWM control gives higher output power and produces an improved output voltage spectrum and significantly lower output current-ripple. Consideration is given here to the effect on output waveforms when H-bridge power stages are series and parallel connected, and controlled by optimally interleaved PWM. Parallel as well as series amplifier connection is shown to produce multilevel output waveforms