US 11,677,326 B2
LLC resonant converter and method of controlling the same
Shang-Kay Yang, Taoyuan (TW); Hsien-Kai Wang, Taoyuan (TW); and Yen-Wei Lin, Taoyuan (TW)
Assigned to DELTA ELECTRONICS, INC., Taoyuan (TW)
Filed by DELTA ELECTRONICS, INC., Taoyuan (TW)
Filed on May 27, 2021, as Appl. No. 17/331,947.
Claims priority of application No. 202011056300.3 (CN), filed on Sep. 30, 2020.
Prior Publication US 2022/0103080 A1, Mar. 31, 2022
Int. Cl. H02M 3/335 (2006.01); H02M 1/00 (2006.01); H02M 1/08 (2006.01)
CPC H02M 3/33573 (2021.05) [H02M 1/0009 (2021.05); H02M 1/0035 (2021.05); H02M 1/08 (2013.01); H02M 3/33592 (2013.01)] 16 Claims
OG exemplary drawing
 
1. An LLC resonant converter configured to convert an input voltage into an output voltage, the LLC resonant converter comprising:
a transformer,
a primary-side circuit coupled to a primary-side winding of the transformer, the primary-side circuit comprising:
a first bridge arm comprising a first switch and a second switch connected to the first switch in series, and configured to receive the input voltage, and
a second bridge arm connected to the first bridge arm in parallel, and comprising a third switch and a fourth switch connected to the third switch in series, and
a control unit configured to provide a first control signal to control the first switch, and provide a fourth control signal to control the fourth switch,
wherein the control unit is configured to adjust a switching frequency of the first control signal and the fourth control signal according to the output voltage; when the switching frequency increases to a frequency threshold value, the control unit controls the switching frequency to be fixed at the frequency threshold value, and controls the first control signal and the fourth control signal having a variable phase difference, and
wherein when the switching frequency is equal to the frequency threshold value, the control unit controls the phase difference not to excess a phase shift threshold value.