A switching supply comprising: an input part (T10, T20); an output part (T30, T40); a first transformer having a first coil group (42, 45, 243, 246); a second transformer having a second coil group (43, 46, 242, 245); an inverter circuit connected between the input part (T10, T20) and an input terminal of the first and second transformers; a rectifier smoothing circuit connected between the output part (T30, T40) and an output terminal of the first and second transformers; a first coil pair having a primary side first coil and a secondary side first coil magnetically coupled; a second coil pair having a primary side second coil and a secondary side second coil magnetically coupled; a third coil pair having a primary side third coil and a secondary side third coil magnetically coupled; and a fourth coil pair having a primary side fourth coil and a secondary side fourth coil magnetically coupled; wherein the first coil group (G1, G3) has the first and third coil pairs, the second coil group (G2, G4) has the second and fourth coil pairs, characterized in that the primary side first coil and the primary side second coil included in the first and second coil pairs are mutually connected in series between an input terminal of the first transformer and an input terminal of the second transformer, the primary side third coil and the primary side fourth coil included in the third and fourth coil pairs are mutually connected in series between an input terminal of the first transformer and an input terminal of the second transformer, the secondary side first coil and the secondary side third coil included in the first and third coil pairs are mutually connected in parallel to the output part (T30, T40), and the secondary side second coil and the secondary side fourth coil included in the second and fourth coil pairs are mutually connected in parallel to the output part (T30, T40). an input part (T10, T20); an output part (T30, T40); a first transformer having a first coil group (42, 45, 243, 246); a second transformer having a second coil group (43, 46, 242, 245); an inverter circuit connected between the input part (T10, T20) and an input terminal of the first and second transformers; a rectifier smoothing circuit connected between the output part (T30, T40) and an output terminal of the first and second transformers; a first coil pair having a primary side first coil and a secondary side first coil magnetically coupled; a second coil pair having a primary side second coil and a secondary side second coil magnetically coupled; a third coil pair having a primary side third coil and a secondary side third coil magnetically coupled; and a fourth coil pair having a primary side fourth coil and a secondary side fourth coil magnetically coupled; wherein the first coil group (G1, G3) has the first and third coil pairs, the second coil group (G2, G4) has the second and fourth coil pairs, characterized in that the primary side first coil and the primary side second coil included in the first and second coil pairs are mutually connected in series between an input terminal of the first transformer and an input terminal of the second transformer, the primary side third coil and the primary side fourth coil included in the third and fourth coil pairs are mutually connected in series between an input terminal of the first transformer and an input terminal of the second transformer, the secondary side first coil and the secondary side third coil included in the first and third coil pairs are mutually connected in parallel to the output part (T30, T40), and the secondary side second coil and the secondary side fourth coil included in the second and fourth coil pairs are mutually connected in parallel to the output part (T30, T40).