Bi-Directional DC-DC Converter and Control Method

A bi-directional DC-DC converter comprising:

• a main high-voltage circuit having a first switching device;
• a main low-voltage circuit having a second switching device;
• a transformer whose ratio of the number of turns is N1/N2 (N1>N2), operatively connected between the main high-voltage circuit and the main low-voltage circuit;
• a step-down controller configured to control the first and second switching devices in the main respective high-voltage circuit and the main low-voltage circuit using a first switching frequency;
• and
• a step-up controller configured to control the first and second switching devices in the respective main high-voltage circuit and the main low-voltage circuit using a second switching frequency which is different from the first switching frequency;
• wherein
• the second switching frequency during step-up operation is set up low than the first switching frequency during step-down;
• and
• a step-up ratio during the step-up operation is larger than the ratio of the number of the transformer turns (N1/N2).