Feed-Forwarding the Output Voltage to Improve Efficiency for Envelope-Tracking Power Supply Based on a Switch-Linear Hybrid Scheme

Envelope-tracking (ET) technique is one of the most promising methods to improve the efficiency of the modern wireless communication transmitters, which is based on using a high-efficient power supply to provide varying voltage to the RF power amplifier. For this application, this letter adopts an AB-type linear amplifier and a synchronous rectification buck converter connected in parallel at the output to construct the ET power supply. The linear amplifier features of wide bandwidth and makes the output voltage follow the envelope of the transmitted signal; the buck converter features of high efficiency provides most of the load current. An average current control strategy with constant switching frequency is proposed, and it is further improved by feed-forwarding the output voltage to reduce the current of the linear amplifier, leading to higher efficiency. A prototype is built and shown to perform very well, achieving high efficiency and track bandwidth of about 100 kHz.