DC to DC power converter device capable of either bidirectional step-up conversion or bidirectional step-down conversion, and control method thereof

A direct current to direct current (DC to DC) power converter device comprising:

• a DC to DC resonant converter having a first side and a second side, each of said first and second sides including a positive terminal and a negative terminal, said DC to DC resonant converter including
• a first full bridge chopper circuit including a first switch, a second switch, a third switch and a fourth switch, said first switch being coupled between said positive terminal of said first side and a first node, said second switch being coupled between said first node and said negative terminal of said first side, said third switch being coupled between said positive terminal of said first side and a second node, said fourth switch being coupled between said second node and said negative terminal of said first side,
• a second full bridge chopper circuit including a fifth switch, a sixth switch, a seventh switch and an eighth switch, said fifth switch being coupled between said positive terminal of said second side and a third node, said sixth switch being coupled between said third node and said negative terminal of said second side, said seventh switch being coupled between said positive terminal of said second side and a fourth node, said eighth switch being coupled between said fourth node and said negative terminal of said second side, and
• an LLC resonant circuit including a resonant capacitor, a resonant inductor and a transformer, said transformer including a primary winding and a secondary winding, said resonant capacitor, said resonant inductor and said primary winding being coupled in series between said first and second nodes, said secondary winding being coupled between said third and fourth nodes;
• and
• a controller coupled to said first to eighth switches, and controlling transition of each of said first to eighth switches between an ON state and an OFF state so that said DC to DC resonant converter operates in one of a first conversion mode, a second conversion mode and a third conversion mode;
• in the first conversion mode, an input voltage received at said first side being converted to an output voltage provided at said second side;
• in each of the second and third conversion modes, an input voltage received at said second side being converted to an output voltage provided at said first side;
• wherein, to cause said DC to DC resonant converter to operate in the third conversion mode, said controller controls said first to eighth switches in such a way that
• said second and fourth to eighth switches transition between the ON state and the OFF state with the ON state reoccurring at a frequency lower than a resonant frequency of said DC to DC power converter device when said second side serves as an input side, wherein the resonant frequency is related to said resonant capacitor and said resonant inductor, and wherein said fifth and eighth switches transition between the ON state and the OFF state synchronously, said sixth and seventh switches transition between the ON state and the OFF state synchronously, an operating state of said sixth switch is substantially always different from an operating state of said fifth switch, said sixth switch transitions from the OFF state to the ON state after said fifth switch transitions from the ON state to the OFF state, and transitions from the ON state to the OFF state before said fifth switch transitions from the OFF state to the ON state, said second switch transitions from the OFF state to the ON state upon completion of one cycle of resonance of said resonant capacitor and said resonant inductor when said fifth switch stays in the ON state, and transitions from the ON state to the OFF state upon said fifth switch transitioning from the ON state to the OFF state, and said fourth switch transitions from the OFF state to the ON state upon completion of one cycle of resonance of said resonant capacitor and said resonant inductor when said sixth switch stays in the ON state, and transitions from the ON state to the OFF state upon said sixth switch transitioning from the ON state to the OFF state, and
• said first and third switches stay in the OFF state.