A planar magnetic component (PE) arranged on a circuit board (CB1) of a resonant converter , the resonant converter comprising a primary-side circuit and a secondary-side circuit , the planar magnetic component (PE) comprising: an inductor trace (Tl) arranged on the primary-side circuit and formed on one layer board of the circuit board (CB1) to serve as a resonant inductor (Lr) electrically connected to the primary-side circuit , an inductor iron core (C_L) comprising a core pillar (C_LC), the core pillar (C_LC) penetrating a through hole (H3) of the circuit board (CB1), and the inductor trace (Tl) surrounding the through hole (H3), an iron core (C1) comprising a first core pillar (C12) and a second core pillar (C14) respectively penetrating a first through hole (H1) and a second through hole of the circuit board (CB1), a transformer comprising a primary-side trace (Tp1) surrounding the first through hole (H1) to serve as a primary-side coil electrically connected to the primary-side circuit , and a secondary-side trace (Ts1) surrounding the second through hole (H2) to serve as a secondary-side coil electrically connected to the secondary-side circuit , characterized by a current transformer trace (Tca, Tcb) formed on the circuit board (CB1) to serve as a current transformer coil coupled to the resonant inductor (Lr), wherein the current transformer trace (Tca, Tcb) surrounds the through hole (H3) to form a common-core structure that shares the inductor iron core (C_L), and wherein the current transformer trace (Tca, Tcb) surrounding the through hole (H3) has a first area, and the inductor trace (Tl) surrounding the through hole (H3) has a second area, and the first area is less than the second area. an inductor trace (Tl) arranged on the primary-side circuit and formed on one layer board of the circuit board (CB1) to serve as a resonant inductor (Lr) electrically connected to the primary-side circuit , an inductor iron core (C_L) comprising a core pillar (C_LC), the core pillar (C_LC) penetrating a through hole (H3) of the circuit board (CB1), and the inductor trace (Tl) surrounding the through hole (H3), an iron core (C1) comprising a first core pillar (C12) and a second core pillar (C14) respectively penetrating a first through hole (H1) and a second through hole of the circuit board (CB1), a transformer comprising a primary-side trace (Tp1) surrounding the first through hole (H1) to serve as a primary-side coil electrically connected to the primary-side circuit , and a secondary-side trace (Ts1) surrounding the second through hole (H2) to serve as a secondary-side coil electrically connected to the secondary-side circuit , characterized by a current transformer trace (Tca, Tcb) formed on the circuit board (CB1) to serve as a current transformer coil coupled to the resonant inductor (Lr), wherein the current transformer trace (Tca, Tcb) surrounds the through hole (H3) to form a common-core structure that shares the inductor iron core (C_L), and wherein the current transformer trace (Tca, Tcb) surrounding the through hole (H3) has a first area, and the inductor trace (Tl) surrounding the through hole (H3) has a second area, and the first area is less than the second area. <EOS>