DC-DC converter having partial DC input conversion

• US 8,817,492 B2
• Filed: 06/25/2012
• Issued: 08/26/2014
• Est. Priority Date: 12/23/2009
• Status: Active Grant

• Current Assignee: SMA Solar Technology AG
• Original Assignee: SMA Solar Technology AG
• Inventors: Rigbers, Klaus, Althof, Carsten, Papenfuss, Frank
• Primary Examiner(s): Vu, Bao Q
• Application Number:
  US13/532,046
• Publication Number:
  US 20120262952A1
• Time in Patent Office: 792 Days
• Field of Search: 363 15- 17, 363/131, 363/132, 363/97, 363/98, 323/906
• US Class Current: 363/17
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/22 with intermediate conversion into ac
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer

Abstract

A DC/DC converter includes two input terminals for a DC input voltage, two output terminals for a DC output voltage, an inverter converting a DC voltage into an AC voltage, and a rectifier converting an AC voltage from the inverter into a DC voltage between a first one of the input terminals and a first one of the output terminals. At least one galvanically isolating element is arranged between the output of the inverter and the input of the rectifier, and a capacitance is coupled between the output terminals. The inverter converts a partial DC voltage, being smaller than the full DC input voltage, across a capacitance between the second one of the input terminals and the second one of the output terminals.

Claims

1. A DC/DC converter, comprising:

two input terminals configured to receive a DC input voltage;

two output terminals configured to output a DC output voltage;

an inverter configured to convert a DC voltage at its input into an AC voltage at its output;

a rectifier connected to the output of the inverter at its input end and connected between a first one of the two input terminals and a first one of the two output terminals at its output end, wherein the rectifier is configured to convert an AC voltage applied to its input into a DC voltage between the first one of the two input terminals and the first one of the two output terminals;

at least one galvanically isolating element arranged between the output of the inverter and the input of the rectifier, and

a capacitance between the two output terminals,

wherein the inverter is configured to convert a partial DC voltage drop with respect to a full DC voltage drop across the two input terminals across a capacitance between a second one of the two input terminals and a second one of the two output terminals, wherein the partial DC voltage drop is smaller than the full DC voltage drop across the two input terminals.

2. The DC/DC converter of claim 1, wherein the at least one galvanically isolating element comprises a capacitor or a transformer.

3. The DC/DC converter of claim 2, further comprising at least one resonant circuit coupled between the output of the inverter and the input of the rectifier.

4. The DC/DC converter of claim 3, wherein the inverter comprises one or more half-bridge circuits, and wherein one resonant circuit is formed between the output of the inverter and the input of the rectifier for each half-bridge circuit of the inverter.

5. The DC/DC converter of claim 4, wherein all resonant circuits between the output of the inverter and the input of the rectifier have a same resonant frequency.

6. The DC/DC converter of claim 1, wherein individual output terminals of the inverter are connected to each other via at least one inductance and at least one capacitance.

7. The DC/DC converter of claim 1, wherein each individual output terminal of the inverter and/or each individual input terminal of the rectifier is connected to one of the input terminals or output terminals via an inductance and a capacitance.

8. The DC/DC converter of claim 1, wherein the inverter comprises switches, and wherein an actuation of the switches of the inverter is performed at a duty cycle between 30% and 50% regardless of a switched state of any converters connected downstream thereof.

9. The DC/DC converter of claim 1, wherein the capacitance between the second one of the two input terminals and the second one of the two output terminals is in parallel with at least one circuit configured to vary a voltage drop across the capacitance.

10. The DC/DC converter of claim 9, wherein the circuit is configured to reduce the voltage drop across the capacitance between the second one of the two input terminals and the second one of the two output terminals towards zero.

11. The DC/DC converter of claim 9, wherein the circuit comprises at least one switch.

12. The DC/DC converter of claim 11, wherein the circuit comprises one inductance and at least one diode.

13. The DC/DC converter of claim 1, wherein electric potentials at the two input terminals relative to ground have a same sign or one of these electric potentials is zero.

14. The DC/DC converter of claim 12, wherein, in one mode of operation of the circuit, a signal from a sensor that senses a current to ground has an impact on a control logic of the circuit.

15. The DC/DC converter of claim 14, wherein the sensed current to ground is a leakage current from one of the output terminals of the DC/DC converter or at an output of an inverter connected downstream of the DC/DC converter.

16. A DC/DC converter, comprising:

an inverter configured to receive at first and second inputs a partial DC voltage of a full DC input voltage of the DC/DC converter, and provide an AC output voltage associated therewith;

a rectifier configured to receive the AC output voltage at an input via a coupling element, and provide at first and second outputs a DC output voltage associated therewith,

wherein the full DC input voltage of the DC/DC converter is applied to the second input of the inverter and the second output of the rectifier, and

wherein an output voltage of the DC/DC converter is tapped at the first input of the inverter and the first output of the rectifier.

17. The DC/DC converter of claim 16, wherein the coupling element comprises a galvanically isolating element.

18. The DC/DC converter of claim 17, wherein the galvanically isolating element comprises a capacitance or a transformer.

19. The DC/DC converter of claim 16, further comprising a resonant circuit coupled between the inverter and the recitifier.

20. The DC/DC converter of claim 17, further comprising:

a capacitance between the first and second inputs of the inverter; and

a start-up circuit configured to vary a magnitude of the partial DC voltage across the capacitance.