G. Gong, H. Ertl, J.W. Kolar:
"Novel Tracking Power Supply for Linear Power Amplifiers";
IEEE Transactions on Industrial Electronics, 55 (2008), 2; 684 - 698.

Conventional linear power amplifiers (LPAs) show a
high output voltage quality but are characterized by high power
losses and/or low power density. Therefore, there is a growing
interest in increasing the efficiency of LPAs, e.g., for the realization
of high power testing voltage sources. In this paper, a highfrequency
isolated boost-type tracking power supply (TPS) system
is proposed for the conditioning of the input voltage of an LPA.
The output voltage of the TPS is varied according to the voltage
to be formed by the LPA so that the voltage drop across the
power amplifier output transistors is reduced to low values. This
results in a significant increase of the total system efficiency. The
operating principle of the proposed system is described. A design
method for the output filter using the power supply rejection ratio
of the LPA is proposed. This method ensures that the ampli-
fier output voltage has minimal switching frequency components.
Furthermore, a control system design method is presented that
ensures good performance in the control of the constant inductor
current of the switch-mode tracking stage. Finally, the theoretical
considerations are verified bymeasurements on a 1-kW laboratory
prototype.
Index Terms-Linear power amplifier (LPA), supply voltage
conditioning, testing power supply, tracking power supply (TPS).