LLC resonant converter with wide output voltage control ranges operating at a constant switching frequency

Design and Implementation of a Two-Stage Resonant Converter for Wide Output Range Operation

“…1) Approaches considering the primary or secondary side structures: An LLC structure reconfigurable for half-bridge or full-bridge operation combined with auxiliary switches at secondary side is proposed in [22]. Such a solution is able to cover a very wide range of output voltages, but additional switches and dedicated modulation capable of smoothly transit between the configurations are required.…”

“…1) primary-side [15], [17]- [19] or secondary-side structures [11], [20]- [22]; 2) resonant tank [23]; 3) conversion structure considering partial-power conversion [3], [24], [25], and 4) number of stages [10], [26]- [31].…”

Analysis and Performance Evaluation of a Two-Stage Resonant Converter for Wide Voltage Range Operation

“…The transformer design procedure adopted herein is based on [26]. Once the magnetic core is selected, with given magnetic volume V c , window winding area W a , core crosssectional area A c , Steinmetz parameters K c , α and β, and maximum window filling factor k u of the transformer (typ., assume k u ≤ 40%), it is possible to calculate the winding and core losses as: (11) where P cond is the total copper loss, ρ w is the copper resistivity, V w is the total windings volume, RF = R ac /R dc is the resistivity factors for the selected litz wire at fundamental frequency [26], J 0 is the current density, V A is the power rating of the transformer, K v is the waveform factor, f s is the fundamental frequency, B max is the peak flux density, k f is core stacking factor, A p = AcW a is the area product of the core and P core is the core loss given by the Steinmetz equation with parameters K c , α and β. The total loss of the transformer is then computed as P cond +P core and must be lower than the thermal dissipation capability of the component, which can be estimated during the design phase.…”

“…Fig. 7 reports the results using (11), showing a total loss of 17 W at nominal conditions, namely, V o = 400 V and P o = 5 kW. A corresponding prototype of the transformer was implemented using a core PQ50/50 N87 and two parallel litz wires 500 × 71 µm, resulting in a measured total power loss of 21 W at the same nominal conditions.…”

“…The literature reports approaches to overcome the limitations of the frequency-modulated LLC converter [2], [8]- [10]. An LLC structure reconfigurable for half-bridge or full-bridge operation is proposed in [11], but smooth transitions between the configurations may be complex to achieve. A reconfigurable This work has been created in the context of the PROGRESSUS project.…”