Switched Capacitor Based High Bandwidth Envelope Tracking Power Supply

Abstract

The envelope tracking (ET) power supply can output a variable voltage which tracks the envelope of the radio frequency input signal to the power amplifier (PA), and the system efficiency can be significantly improved. To achieve a high tracking bandwidth, the switching frequency of the ET power supply is usually too high. The pulse edge independent distribution (PEID) method has been proposed to reduce the switching frequency to 1/n (n ϵ N) of the tracking bandwidth, but a large number of isolated voltage sources are needed, leading to increased power stage and system complexity. In this letter, a switched capacitor based high bandwidth ET power supply is proposed, which employs optimized charging topologies and mechanisms to stabilize the voltages across the switched capacitors, and thus they can fully replace the isolated voltage sources. Since the proposed configuration is derived from the PEID method, all the features of PEID method are retained. A prototype with 6-26-V output voltage and 20-W peak output power is fabricated and tested with a 1-MHz sine wave and a 5-MHz bandwidth communication envelope. The experimental results validate the proposed configuration.