A comparative analysis of two approaches in EER based envelope tracking power supplies

Abstract

In modern telecommunication systems, the requirements for amount of transmitted data are increasing rapidly. For a better spectral efficiency complex type modulations (QAM, OFDM) are used, resulting in high PAPR signals. As a consequence, if conventional linear amplifiers (classes A, B) are used in transmitters, prominent linearity, but poor efficiency are assured. The efficiency of the transmitters can be significantly improved using some of the popular techniques: Kahn EER technique, ET technique, Doherty amplifier, Chireix's amplifier. In this paper, two different approaches in supplying power amplifier based on EER technique are presented. The same part of both envelope amplifiers (EA) is switched-capacitor based voltage divider combined with switching structure, analog multiplexer. The analog multiplexer is assisted with series linear regulator, in the first system, and with a fourth order LC filter, in the second system. Two prototypes for 10 W average output power with about 40 W peak output power are fabricated and the experimental results are compared in terms of efficiency and signal quality.

Tracking Multilevel Power Supplies for Class-D Audio Amplifiers

“…This can be rewritten to use a distribution by considering the sum of the costs (11) for operating between each pair of discrete supply voltages (12).…”

“…Where the m'th level will be the maximum level of the supply voltage. In (12) it is noticed that the size of the summation for each φ αi varies with the placement of the voltages rails, α, making the optimization difficult to solve efficiently. The cost functions in (11), (12) will minimize the losses introduced by the voltage overhead, which in the case of class-G amplifiers would be the desired minimization.…”

“…Another study [11] proposes a different approach where dedicated power supply constantly adjust the supply voltage of a conventional Buck type Class-D amplifier also beneficial for the low power efficiency. This paper will use a Tracking Multi-Level Power Supply (TMLPS) similar to that but with discrete voltage levels as seen in [12][13][14][15][16] Radio Frequency (RF) amplifiers. A TMLPS is capable of toggling between multiple fixed voltage levels as depicted in Fig.…”

Multilevel tracking power supply for switch-mode audio power amplifiers

“…Future work includes an implementation using a switch-cap circuit to generate the fixed voltage levels as proposed in [9]. In addition to this the control signals, S1 − S3, may be implemented on an audio DSP instead of the HPPD/comparator circuit, as audio DSPs is a typical component in audio systems [21].…”

“…A similar challenge exists for Radio Frequency (RF) power amplifiers where highly dynamic radio signals cause low efficiency [7]- [9]. To overcome this challenge within RF power amplifiers several methods have been proposed including Envelope Tracking (ET) and Envelope Elimination and Restoration (EER) [10]- [13].…”