Non-isolated bus converters with voltage divider topology

• US 7,746,041 B2
• Filed: 03/27/2007
• Issued: 06/29/2010
• Est. Priority Date: 06/27/2006
• Status: Active Grant

• Current Assignee: Virginia Tech Intellectual Properties, Inc.
• Original Assignee: Virginia Tech Intellectual Properties, Inc.
• Inventors: Xu, Ming, Lee, Fred C., Sun, Julu
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US11/691,800
• Publication Number:
  US 20070296383A1
• Time in Patent Office: 1,190 Days
• Field of Search: 323/223, 323/224, 323/225, 323/282, 323/283, 323/284, 323/285
• US Class Current: 323/223
• CPC Class Codes: H02M 1/0043 Converters switched with a phase shift, i.e. interleaved non-isolated DC/DC converters H02M3/1586
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 7/4837 Flying capacitor converters

Abstract

A voltage converter having four switches Q1, Q2, Q3, Q4, connected in series and operated in pairs in a complementary fashion. An input voltage is provided across the four switches. A middle capacitor is connected in parallel with two middle switches Q2, Q3. Voltage output is provided across switches Q3 and Q4 (i.e. at a midpoint of the four switches). Series-connected output capacitors can be connected in parallel with the set of four switches. The middle capacitor alone or in combination with parallel connected capacitors, when connected to the input voltage or output terminals functions as a capacitive voltage divider for voltage conversion and/or regulation with extremely high efficiency and which can provide either step-down or step-up function. Also, an output inductor can be provided as a perfecting feature to further increase efficiency. Alternatively, two of the four switches can be replaced with rectifying diodes. Alternatively, the voltage converter has two or more sets of four switches connected in parallel. The two sets can be connected by resistor-capacitor ladder, or an inductor-capacitor ladder for charge/voltage sharing to reduce voltage ripple.

Claims

1. A voltage converter comprising

a plurality of selective conduction devices connected to each other in series at respective nodes to form a series connection, at least two of said plurality of selective conduction devices being controllable switches,

at least one capacitor connected between two of said respective nodes connecting said plurality of selective conduction devices to each other,

a voltage source connected to two of said respective nodes at respective ends of said series connection, and

means for controlling said controllable switches to conduct in mutually exclusive groups to define two different conduction paths, each of said two different conduction paths including a conduction path through said at least one capacitor, whereby said combination of said at least one capacitor and said plurality of said selective conduction devices functions substantially as a capacitive voltage divider to reduce a voltage provided by said voltage source or as a voltage multiplier to increase a voltage supplied by said voltage source.

2. The voltage converter as recited in claim 1, further comprising

at least one additional capacitor connected to an output connection of said voltage converter, said at least one capacitor being connected in series with said at least one additional capacitor in one of said two different conduction paths and in parallel with said at least one additional capacitor in another of said two different conduction paths.

3. The voltage converter as recited in claim 1 wherein said means for controlling said controllable switches operates said controllable switches with a 50% duty cycle.

4. The voltage converter as recited in claim 1, further comprising

an inductor connected in series with an output connection of said voltage converter.

5. The voltage converter as recited in claim 4, further comprising

a filter capacitor connected in parallel with an output of said voltage converter.

6. The voltage converter as recited in claim 1, further comprising

a filter capacitor connected in parallel with an output of said voltage converter.

7. The voltage converter as recited in claim 1, wherein said plurality of selective conduction devices comprise four selective conduction devices.

8. The voltage converter as recited in claim 1, wherein said plurality of selective conduction devices include diodes.

9. The voltage converter as recited in claim 1, further comprising

a further plurality of selective conduction devices connected to each other in series at respective nodes and in parallel with said plurality of selective conduction devices, at least two of said further plurality of selective conduction devices being controllable switches,

at least one further capacitor connected between two of said respective nodes of said further plurality of selective conduction devices,

a voltage source connected to two of said respective nodes, and

means for controlling said controllable switches of said further plurality of selective conduction devices to conduct in a mutually exclusive manner and complementary to said controllable switches of said plurality of selective conduction devices to define two further different conduction paths, each of said two different conduction paths including a conduction path through said at least one further capacitor.

10. The voltage converter as recited in claim 9, further comprising voltage sharing means connected between said at least one capacitor and said at least one further capacitor.

11. The voltage converter as recited in claim 10, wherein said voltage sharing means includes resistors.

12. The voltage converter as recited in claim 10, wherein said voltage sharing means includes coupled inductors.

13. The voltage converter as recited in claim 9, wherein said plurality of selective conduction devices include diodes.

14. A voltage converter, comprising:

a) a set of four switches Q1, Q2, Q3, Q4, connected in series, and connected, in order, across a voltage input;

b) a capacitor connected in parallel with a middle pair Q2, Q3, of the four switches;

c) a pair of storage capacitors connected in series with each other, and connected in parallel with the set of four switches, and wherein a midpoint of the storage capacitor pair is connected to a switch midpoint node connecting switches Q2 and Q3; and

d) a gate driver for operating switches Q1, Q3, in a manner complementary to switches Q2 Q4;

whereby an output voltage is provided across switches Q3 and Q4.

15. The voltage converter of claim 14, further comprising an output inductor connected to a switch midpoint, and connected to a voltage output.

16. A voltage converter, comprising:

a) a first set of four switches Q1, Q2, Q3, Q4, connected in series;

b) a middle capacitor connected in parallel with a middle pair Q2, Q3, of the first set of four switches;

c) a second set of four switches Q5, Q6, Q7, Q8, connected in series, wherein the first set and second set are connected in parallel, and connected across a voltage input or output;

d) a second capacitor connected in parallel with a middle pair Q6, Q7, of the second set of four switches;

e) a gate driver for operating switches Q1, Q3, in a complementary manner compared to switches Q2, Q4, and for operating switches Q5, Q7, in a complementary manner compared to switches Q6, Q8;

wherein an output voltage, or input voltage, is provided across switches Q3 and Q4, and across switches Q7 and Q8.

17. The voltage converter of claim 16 further comprising an output inductor connected to the voltage output.

18. The voltage converter as recited in claim 16 wherein said voltage converter is a step down voltage converter.

19. The voltage converter as recited in claim 16 wherein said voltage converter is a step up voltage converter.