Energy Recovery of the Linear Amplifier in the Parallel-Form Switch-Linear Hybrid Envelope Tracking Power Supply

Parallel-form switch-linear hybrid (SLH) envelope tracking (ET) power supply is composed of a current-controlled switched-mode converter (CSC) and a voltage-controlled linear amplifier (VLA) connected in parallel. When the bandwidth of the envelope signal is much larger than the tracking bandwidth of the CSC, it works as a quasi-constant current source, which requires the linear amplifier to compensate a large current and the overall efficiency is lowered. Especially when the current of CSC is larger than the load current, the redundant current will be absorbed and wasted by the VLA. This paper proposes to introduce a hysteresis voltage controlled boost converter to store the redundant energy provided by CSC and feedback to the system input. Then, a simulation platform is implemented with the specifications as 5 MHz tracking bandwidth, 8 V ~ 28 V output voltage and 20 W average output power. The simulation results verify the effectiveness of the proposed topology, and about 5% efficiency improvement can be achieved by adding the boost converter when tracking a single-tone sine wave.