Multi-Stage Multilevel DC-DC Step-Down Converter
AssigneeQueen's University at Kingston
InventorsTianshu Liu, Yan-Fei Liu
Life of this patent
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Abstract
Disclosed are multi-stage multilevel DC-DC step-down converters. Stages may include three or four switches, and switches of each stage are operated at selected duty cycles such that each stage reduces an input voltage by one-half and voltage stress on switches is reduced. In some embodiments only a single output inductor is used in an LC filter, and the inductor may be very small as compared with a conventional Buck converter. Thus, embodiments provide DC-DC step-down converters with high power density and efficiency.
Claims20
A method for controlling a DC-DC converter, wherein the DC-DC converter comprises at least one stage, wherein the at least one stage is a first stage comprising:
- first and second input terminals and first and second output terminals, wherein the second input terminal and the second output terminal are connected together as a common terminal;
- first, second, third, and fourth switches connected together in series across the first and second input terminals;
- a first capacitor connected in parallel with the second and third switches;
- a first inductor having a first terminal connected between the second and third switches and a second terminal connected to a first output terminal;
- and
- a second capacitor connected across the first and second output terminals;
- wherein the method comprises:
- turning on the first and third switches for a first selected portion of a first switching cycle;
- turning on the second and fourth switches for a second selected portion of the first switching cycle;
- wherein the first and second selected portions of the first switching cycle are each 50%;
- wherein an output DC voltage of the DC-DC converter is 0.5 times an input DC voltage of the DC-DC converter;
- and
- wherein a voltage across the first inductor is substantially zero volts.
A DC-DC converter, comprising:
- a first input terminal adapted to receive an input DC voltage;
- a common terminal;
- a first four switch (4S) stage comprising:
- first, second, third, and fourth switches connected together in series across the first input terminal and the common terminal;
- a first capacitor connected in parallel with the series-connected second and third switches;
- a 4S input point connected to an input terminal of the first switch;
- a 4S output point at a first node between the second and third switches;
- a common terminal connected to an output terminal of the fourth switch;
- an output circuit comprising a series inductor, a parallel capacitor, and a first output terminal adapted to output a DC voltage;
- and
- a controller that controls the 4S switches such that the first and third switches are switched on and off together, the second and fourth switches are switched on and off together, the first and third switches are not on when the second and fourth switches are on, and the duty cycle of the switches is 50% or less;
- wherein an output DC voltage is one-half of the input DC voltage.
Dependencies are inferred from the claim text.