Switch-linear hybrid envelope-tracking power supply with multilevel structure

Based on the research of parallel-switch-linear hybrid envelope tracking (ET) power supply, this paper proposes a new topology where a multilevel structure converter in parallel with a linear amplifier. Adopting discrete level modulation, the converter operates each switcher only once during every tracking period. So it can achieve higher tracking bandwidth with the same switching frequency, compared to other schemes. Due to the poor anti-jamming capability of the comparators used in control circuits, the bandwidth must be lowered to suppress the high frequency noise. However, the low bandwidth leads to the limited loop gain at the tracking frequency, which is unable to reduce the load admittances of linear amplifier, forcing it to output an extra fundamental wave current component. This decreases the system efficiency greatly. The full feed-forward of the output voltage scheme is adopted to eliminate the influences from the output voltage to the linear amplifier output current. A prototype is built aiming for 300kHz sine wave tracking, with 10V~26V output voltage and 50W peak output power. The experimental results verify the effectiveness of theoretical analysis.