Gain-Relationship-Based Automatic Resonant Frequency Tracking in Parallel <inline-formula> <tex-math notation="LaTeX">$LLC$</tex-math></inline-formula> Converter

Abstract

This paper proposes a generic control scheme for automatic resonant frequency tracking (ARFT) in resonant converters. The plant is modeled based on realistic ramp variation of resonant frequency due to slowly varying environmental conditions. The proposed ARFT scheme monitors the gain relationship between an exclusive electrical variable-pair to detect frequency drift. An analytical approach is presented to select the most suitable variable-pair for gain comparison. The effects of tank parameter variation and circuit non-idealities on the gain relationship of the chosen variable-pair have been analyzed. An online correction mechanism is proposed to nullify the influence of load variation on the proposed technique. Second order generalized integrator (SOGI) based low cost analog realization of the proposed strategy is detailed. Analytical predictions are experimentally validated by applying the control scheme to a parallel LLC tank based resonant dc-dc converter.Index Terms-Automatic resonant frequency tracking (ARFT), Gain comparator, Second order generalized integrator (SOGI), Parallel LLC tank, Dc-dc converter 0278-0046 (c)

An adaptive synchronous rectifier driving strategy for unregulated LLC resonant converter

“…The basic operational principle of the proposed technique is very simple and the details have been discussed in [22]. To summarize, only at resonant frequency, the LLC converter voltage gain is unity.…”

“…In [22], the converter voltage gain is directly calculated based on the input voltage and output voltage, and the operating switching frequency is adjusted accordingly. However, for SR LLC converter, due to the bi-directional current flow capability, the converter voltage gain is also adjusted.…”

“…Many different resonant frequency tracking techniques have been proposed based on the LLC converter operation [15][16][17][18][19][20][21][22]. When operating at resonant frequency, there should be no period for zero secondary rectifier current, which is called boundary conduction mode (BCM).…”

“…In [22,23], a resonant frequency tracking strategy is proposed for LLC converter based on the phase or gain relationship of circuit electrical pairs. However, the implementation of this strategy requires complicate analog circuitries.…”

A new double mode control strategy for power router with very wide DC voltage range

“…However, this approach is only suitable for an ideal DC transformer (DCT) with very limited voltage range of DC bus. To effectively regulate the voltage of DC bus, the frequency regulation control (FRC) has been widely applied in resonant DC/DC converter [22][23][24]. Nevertheless, if the switching frequency deviates from the resonant frequency, significant reactive power loss will be induced, degrading the efficiency.…”