High-efficiency llc resonant converter

An LLC resonant converter, comprising:

• a DC power supplying unit, having at least one first switch element, and being configured for receiving a power signal, thereby outputting a first voltage signal after applying a power conversion process to the power signal;
• a bridge switch unit, being coupled to the DC power supplying unit for receiving the first voltage signal;
• a resonant unit, comprising a resonant inductor and a resonant capacitor, and being coupled to a second voltage signal that is transmitted from the bridge switch unit;
• a transformer unit, comprising a primary winding, a magnetizing inductor that is parallelly connected to the primary winding, and a secondary winding having a first electrical terminal, a second electrical terminal and a third electrical terminal, wherein the primary winding is coupled to the resonant unit, such that the magnetizing inductor, the resonant inductor and the resonant capacitor together form an LLC resonant tank;
• an output rectifying unit, being coupled to the first electrical terminal and the third electrical terminal of the secondary winding, thereby outputting an output voltage signal to at least one load device after applying a signal rectifying process to a third voltage signal received from the secondary winding;
• a detection unit, being coupled to the second electrical terminal of the secondary winding, and having two end terminals;
• a first control unit, being coupled to the output rectifying unit;
• an error amplifier unit, being coupled to the two end terminals of the detection unit, so as to correspondingly generate a modulated voltage signal after receiving a voltage difference from two terminal ends of the detection unit;
• a first isolation feedback unit, being coupled to the error amplifier unit;
• and
• a second control unit, being coupled to the first isolation feedback unit, and being also coupled to the modulated voltage signal Sm via the first isolation feedback unit;
• wherein the second control unit calculates an immediate load rate based on the modulated voltage signal, and correspondingly generating a first switch element controlling signal, based on the calculated immediate load rate, transmitted to a control signal receiving terminal of the switch element of the DC power supplying unit, such that an output voltage modulation of the DC power supplying unit is achieved by using the first switch element controlling signal to control a switching frequency of the first switch element, thereby keeping a conversion efficiency of the LLC resonant converter be greater than a specific value.