Resonant converters and methods
A multilevel LLC resonant converter comprises a resonant tank connected in series with a primary side of a transformer, a first switch and a second switch connected in series, wherein a common node of the first switch and the second switch is coupled to a mid-voltage point through a first isolation switch and the resonant bank and a third switch and a fourth switch connected in series, wherein a common node of the third switch and the fourth switch is coupled to the resonant tank.
1. An apparatus comprising:
a first capacitor and a second capacitor connected in series providing a mid-voltage point of an input dc power source;
a resonant tank connected in series with a primary side of a transformer;
a first leg comprising a first switch, a second switch, a third switch and a fourth switch connected in series, wherein:
a common node of the first switch and the second switch is connected to the mid-voltage point through a first semiconductor element;
a common node of the third switch and the fourth switch is connected to the mid-voltage point through a second semiconductor element; and
a common node of the second switch and the third switch is connected to the resonant tank; and
a second leg comprising a fifth switch and a sixth switch connected in series, wherein a common node of the fifth switch and the sixth switch is coupled to the resonant tank.
2. The apparatus of claim 1 , wherein:
the resonant tank comprises an inductor and a capacitor.
3. The apparatus of claim 1 , wherein:
the first semiconductor element is a first diode; and
the second semiconductor element is a second diode.
4. The apparatus of claim 3 , wherein:
a cathode of the first diode is connected to the common node of the first switch and the second switch; and
an anode of the first diode is connected to the mid-voltage point.
5. The apparatus of claim 3 , wherein:
a cathode of the second diode is connected to the mid-voltage point; and
an anode of the second diode is connected to the common node of the third switch and the fourth switch.
6. The apparatus of claim 1 , wherein:
the mid-voltage point is a common node of the first capacitor and the second capacitor.
7. The apparatus of claim 1 , wherein:
the first semiconductor element is a first transistor; and
the second semiconductor element is a second transistor.
8. The apparatus of claim 7 , wherein:
a drain of the first transistor is connected to the common node of the first switch and the second switch; and
a source of the first transistor is connected to the mid-voltage point.
9. The apparatus of claim 7 , wherein:
a drain of the second transistor is connected to the mid-voltage point; and
a source of the second transistor is connected to the common node of the third switch and the fourth switch.
10. The apparatus of claim 1 , further comprising:
a synchronous rectifier coupled to a secondary side of the transformer; and
an output filter coupled to the synchronous rectifier.
11. A system comprising:
an input power source;
a first capacitor and a second capacitor connected in series across the input power source;
a resonant tank connected in series with a primary side of a transformer to form a resonant network;
a first leg comprising a first switch, a second switch, a third switch and a fourth switch connected in series, wherein:
a common node of the first switch and the second switch is connected to a common node of the first capacitor and the second capacitor through a first semiconductor element;
a common node of the third switch and the fourth switch is connected to the common node of the first capacitor and the second capacitor through a second semiconductor element; and
a common node of the second switch and the third switch is connected to the resonant tank;
a second leg comprising a fifth switch and a sixth switch connected in series, wherein a common node of the fifth switch and the sixth switch is coupled to the resonant tank;
a synchronous rectifier coupled to a secondary side of the transformer; and
an output filter coupled to the synchronous rectifier.
12. The system of claim 11 , wherein the resonant tank comprises:
a resonant inductor connected in series with a primary winding of the transformer;
a resonant capacitor connected in series with the primary winding of the transformer; and
a magnetizing inductor connected in parallel with the primary winding of the transformer.
13. The system of claim 11 , wherein the synchronous rectifier comprises:
a first switch coupled between a first terminal of the secondary side of the transformer and ground; and
a second switch coupled between a second terminal of the secondary side of the transformer and ground.
14. The system of claim 13 , wherein the output filter is capacitor coupled between a mid-point of the second side of the transformer and ground.
15. The system of claim 11 , wherein:
the first semiconductor element is a first diode; and
the second semiconductor element is a second diode, and wherein:
a cathode of the first diode is connected to the common node of the first switch and the second switch;
an anode of the first diode is connected to the common node of the first capacitor and the second capacitor;
a cathode of the second diode is connected to the common node of the first capacitor and the second capacitor; and
an anode of the second diode is connected to the common node of the third switch and the fourth switch.
16. The system of claim 11 , wherein:
the first semiconductor element is a first transistor; and
the second semiconductor element is a second transistor, wherein:
a drain of the second transistor is connected to the common node of the first capacitor and the second capacitor;
a source of the second transistor is connected to the common node of the third switch and the fourth switch;
a drain of the second transistor is connected to the common node of the first capacitor and the second capacitor; and
a source of the second transistor is connected to the common node of the third switch and the fourth switch.
17. A device comprising:
a first capacitor and a second capacitor connected in series providing a mid-voltage point of an input dc power source;
a resonant tank connected in series with a primary side of a transformer;
a first leg comprising a first switch, a second switch, a third switch and a fourth switch connected in series, wherein:
a common node of the first switch and the second switch is connected to the mid-voltage point through a fifth switch;
a common node of the third switch and the fourth switch is connected to the mid-voltage point through a sixth switch; and
a common node of the second switch and the third switch is connected to the resonant tank; and
a second leg comprising a seventh switch and an eighth switch connected in series, wherein a common node of the seventh switch and the eighth switch is coupled to the resonant tank.
18. The device of claim 17 , wherein:
a switching frequency of the fifth switch is approximately equal to a resonant frequency of the resonant tank.
19. The device of claim 17 , wherein:
the resonant tank comprising a resonant inductor, a resonant capacitor and a magnetizing inductor of a transformer.
20. The device of claim 19 , wherein:
the resonant inductor connected in series with a primary winding of the transformer;
the resonant capacitor connected in series with the primary winding of the transformer; and
the magnetizing inductor connected in parallel with the primary winding of the transformer.