An LLC resonant converter comprising: a multi input transformer; first and second converter units (210,220) configured to be connected to a primary side of the multi input transformer; an input voltage part configured to apply a voltage to both ends between which the first and second converter units (210,220)are connected in series with each other; an output part configured to be connected to a secondary side of the multi input transformer, wherein the first converter unit includes a first part in which a first switch (M 1) and a first resonance capacitor (C r1) are connected in series with each other and a second part in which a second switch (M 2) and a second resonance capacitor are (C r2) connected in series with each other, the first part, the second part, and a primary side winding of the transformer are connected in parallel to each other, the first switch (M 1) and the second switch (M 2) are connected to each other, and the first resonance capacitor (C r1) and the second resonance capacitor (C r2) are connected to each other, the second converter unit includes a third part in which a third switch (M 3) and a third resonance capacitor (C r3) are connected in series with each other and a fourth part in which a fourth switch (M 4) and a fourth resonance capacitor (C r4) are connected in series with each other, the third part, the fourth part, and a further primary side winding of the transformer are connected in parallel to each other, the third switch (M 3) and the fourth switch (M 4) are connected to each other, and the third resonance capacitor (C r3) and the fourth resonance capacitor (C r4) are connected to each other, wherein a connection point of the first switch (M 1) and the first resonance capacitor (C r1) is a first input terminal of the input voltage part, a connection point of the fourth switch (M 4) and the fourth resonance capacitor (C r4) is a second input terminal of the input voltage part, and a connection point of the second switch (M 2) and the second resonance capacitor (C r2) is connected to a connection point of the third switch (M 3) and the third resonance capacitor (C r3), characterised in that: a first balance capacitor (C B1) is connected to a node between the first switch (M 1) and the second switch (M 2) and a node between the third switch (M 3) and the fourth switch (M 4), the LLC resonant converter being configured to maintain the sum of the voltages across the first and second resonance capacitors (C r1, C r2) equal to the sum of the voltages across the third and fourth resonance capacitors (C r3, C r4) using the first balance capacitor (C B1). a multi input transformer; first and second converter units (210,220) configured to be connected to a primary side of the multi input transformer; an input voltage part configured to apply a voltage to both ends between which the first and second converter units (210,220)are connected in series with each other; an output part configured to be connected to a secondary side of the multi input transformer, wherein the first converter unit includes a first part in which a first switch (M 1) and a first resonance capacitor (C r1) are connected in series with each other and a second part in which a second switch (M 2) and a second resonance capacitor are (C r2) connected in series with each other, the first part, the second part, and a primary side winding of the transformer are connected in parallel to each other, the first switch (M 1) and the second switch (M 2) are connected to each other, and the first resonance capacitor (C r1) and the second resonance capacitor (C r2) are connected to each other, the second converter unit includes a third part in which a third switch (M 3) and a third resonance capacitor (C r3) are connected in series with each other and a fourth part in which a fourth switch (M 4) and a fourth resonance capacitor (C r4) are connected in series with each other, the third part, the fourth part, and a further primary side winding of the transformer are connected in parallel to each other, the third switch (M 3) and the fourth switch (M 4) are connected to each other, and the third resonance capacitor (C r3) and the fourth resonance capacitor (C r4) are connected to each other, wherein a connection point of the first switch (M 1) and the first resonance capacitor (C r1) is a first input terminal of the input voltage part, a connection point of the fourth switch (M 4) and the fourth resonance capacitor (C r4) is a second input terminal of the input voltage part, and a connection point of the second switch (M 2) and the second resonance capacitor (C r2) is connected to a connection point of the third switch (M 3) and the third resonance capacitor (C r3),