Multilevel power converter including switching circuits

• US 6,005,787 A
• Filed: 11/25/1998
• Issued: 12/21/1999
• Est. Priority Date: 11/25/1997
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Mizukoshi, Masahito
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/199,316
• Time in Patent Office: 391 Days
• Field of Search: 363/71, 363/142, 327/403, 327/404, 327/408, 307/44
• US Class Current: 363/71
• CPC Class Codes: H02M 7/483 Converters with outputs that each can have more than two voltages levels

Abstract

A multi-level power converter such as an inverter for changing one of a plurality of dc voltage inputs into an ac voltage output is provided which includes inverter arms disposed between dc power supplies and an ac voltage output terminal. The inverter arms include switching circuits which are selectively subjected to PWM control to establish and block communication between one of the corresponding dc power supplies and the ac voltage output terminal. The switching circuits that are not connected to either the maximum or minimum dc voltage terminal include a first switching device, a second switching device connected in series with the first switching device, a first diode connected backward in parallel to the first switching device, and a second diode connected backward in parallel to the second switching device. This structure decreases the number of floating power supplies for driving the switching elements.

Claims

1. A multilevel power converter comprising:

a plurality of electric paths extending between dc voltage terminals and a common ac voltage output terminal, the dc voltage terminals being connected to dc power supplies creating dc voltages at levels different from each other; and

a plurality of switching circuits each disposed in one of said electric paths, said switching circuits being activated selectively to establish electric communication between corresponding one of the dc power supplies and the ac voltage output terminal to develop an ac voltage output terminal, wherein at least one of said switching circuits is connected to the dc voltage terminal having other than a minimum or a maximum voltage includes a first switching device, a second switching device connected in series with the first switching device, and a second diode connected backward in parallel to the second switching device.

2. A multi-level power converter as set forth in claim 1, wherein two of said switching circuits connected between one of the dc power supplies creating the maximum voltage and the ac voltage output terminal and between another of the dc power supplies creating the minimum voltage and the ac voltage output terminal each include a switching device and a diode connected backward in parallel to the switching device.

3. A multi-level power converter as set forth in claim 1, wherein the first and second switching devices are MOS transistors which are connected at sources to each other.

4. A multi-level power converter as set forth in claim 1, wherein the first and second switching devices are MOS transistors which are connected at drains to each other.

5. A multi-level power converter as set forth in claim 1, wherein said switching circuits are activated selectively under PWM control to establish the electric communication between corresponding one of the dc power supplies and the ac voltage output terminal to allow a current to flow through one of said switching circuits undergoing the PWM control, and wherein one of said switching circuits connected to one of the dc power supplies creating the dc voltage lower than that of another of the dc power supplies undergoing the PWM control is so controlled as to allow a current to flow in the same direction as that of the current flowing through the one of said switching circuits undergoing the PWM control.

6. A multilevel power converter comprising:

a plurality of electric paths extending between dc voltage terminals and a common ac voltage output terminal, the dc voltage terminals being connected to dc power supplies creating dc voltages at level different from each other; and

a plurality of switching circuits each disposed in one of said electric paths, said switching circuits being activated and inactivated selectively to establish and block electric communication between corresponding one of the dc power supplies and the ac voltage output terminal to develop an ac voltage at the ac voltage output terminal,

wherein two of said switching circuits connected to the dc power supplies creating a maximum and minimum voltage each include a switching device, and

wherein at least one of said switching circuits is connected to the dc voltage terminal having other than a minimum or a maximum voltage includes a first and a second switching devices and a first and a second diode connected backward in parallel to the first and the second switching devices, respectively.