Apparatus for converting a direct current into an alternating current

• US 6,151,234 A
• Filed: 03/06/2000
• Issued: 11/21/2000
• Est. Priority Date: 03/08/1999
• Status: Expired due to Fees

• Current Assignee: Hendrik Oldenkamp
• Original Assignee: Hendrik Oldenkamp
• Inventors: Oldenkamp, Hendrik
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/519,806
• Time in Patent Office: 260 Days
• Field of Search: 323/268, 363/132, 363/65, 307/71
• US Class Current: 363/132
• CPC Class Codes: H02M 7/483 Converters with outputs that each can have more than two voltages levels

Abstract

An apparatus for converting a direct current into an alternating current comprises a direct-current converter having an input and an output, which direct-current converter is continuously controllable, a capacitor, and a control unit for controlling the direct-current converter. The apparatus furthermore comprises a second direct-current converter having an input and an output, wherein the input of the second direct-current converter is connected in parallel to the input of the first direct-current converter and the outputs of the first and the second direct-current converter are connected in series. An unfolding bridge is connected to the series-connected outputs of the direct-current converters, whilst the capacitor is connected to the output of the second direct-current converter. Furthermore, a first switching element is provided for interrupting the series connection and a second switching element is provided for connecting the unfolding bridge to the output of the first direct-current converter in the interrupted state of the series connection. The control unit controls at least the first switching element in dependence on the voltage V_c across the capacitor and the voltage V_abs across the unfolding bridge, in such a manner that the first switching element is opened when V_abs <V_c.

Claims

1. Apparatus for converting a direct current into an alternating current, comprising a direct-current converter having an input and an output, which direct-current converter is continuously controllable, a capacitor, a control unit for controlling the direct-current converter, and an unfolding bridge, wherein a second direct-current converter having an input and an output is provided, the input of the second direct-current converter being connected in parallel to the input of the first direct-current converter and the outputs of the first and the second direct-current converter being connected in series, wherein the unfolding bridge is connected to the series-connected outputs of the direct-current converters and the capacitor is connected to the output of the second direct-current converter, wherein a first switching element is provided for interrupting the series connection and a second switching element is provided for connecting the unfolding bridge to the output of the first direct-current converter in the interrupted state of the series connection, wherein the control unit controls at least the first switching element in dependence on the voltage V_c across the capacitor and the voltage v_abs across the unfolding bridge, in such a manner that the first switching element is opened when V_abs <

V_c.

2. Apparatus according to claim 1, wherein the two direct-current converters have one common transformer comprising different secondary windings.

3. Apparatus according to claim 1, wherein the second direct-current converter has at least two outputs, wherein each output of the second direct-current converter can be connected in series to the output of the first direct-current converter by means of an associated first switching element, and a second switching element is provided for each output of the second direct-current converter for connecting the unfolding bridge to the output of the first direct-current converter in the interrupted state of the series connection.

4. Apparatus according to claim 2, wherein the second direct-current converter has at least two outputs, wherein each output of the second direct-current converter can be connected in series to the output of the first direct-current converter by means of an associated first switching element, and a second switching element is provided for each output of the second direct-current converter for connecting the unfolding bridge to the output of the first direct-current converter in the interrupted state of the series connection.

5. Apparatus according to claim 1, wherein the second direct-current converter is controllable over a limited range.

6. Apparatus according to claim 1, wherein the second direct-current converter is a bidirectional converter.