Method and circuit for galvanically isolated transmission of a signal

• US 20060152082A1
• Filed: 01/10/2006
• Published: 07/13/2006
• Est. Priority Date: 01/11/2005
• Status: Active Grant

• Current Assignee: Dspace GmbH
• Original Assignee: Dspace Digital Signal Processing And Control Engineering Gmbh
• Inventors: Gruber, Paul
• Granted Patent: US 7,684,221 B2
• Time in Patent Office: Days
• US Class Current: 307/4
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop

Abstract

A method for galvanically isolated transmission of a signal, especially a switching signal for controlling at least one switching means includes using a transformer. The primary side of a transformer is fed with a pulse-width modulated voltage in which different duty factors are indicative of different signal states. The voltage obtained on the secondary side is converted by an electronic circuit into at least one signal voltage which is dependent on the duty factor and whose magnitude represents a signal state.

Claims

1. A method for galvanically isolated transmission of a signal, the method comprising:

feeding a primary side of a transformer with a pulse-width modulated first voltage, a duty factor of the first voltage indicating a signal state; and

converting, by an electronic circuit, a second voltage obtained on a secondary side of the transformer into at least one signal voltage dependent on the duty factor, a magnitude of the at least one signal voltage representing the signal state.

2. The method as recited in claim 1 wherein the signal is a switching signal for controlling at least one switching device.

3. The method as recited in claim 1 further comprising:

converting the second voltage into a supply voltage independent of or only slightly dependent on the duty factor; and

providing the supply voltage to at least one electronic component.

4. The method as recited in claim 1 further comprising:

generating a supply voltage on the secondary side of the transformer;

obtaining at least one reference voltage from the supply voltage; and

comparing the at least one signal voltage to the at least one reference voltage, a result of the comparing representing a second signal state.

5. The method as recited in claim 4 wherein the at least one reference voltage is independent of or only slightly dependent on the duty factor.

6. The method as recited in claim 4 further comprising operating at least one switching device as a function of the result of the comparing.

7. The method as recited in claim 5 further comprising operating at least one switching device as a function of the result of the comparing.

8. The method as recited in claim 1 further comprising comparing the at least one signal voltage to a reference voltage using at least one comparator by applying the at least one signal voltage and the reference voltage to respective inputs of the comparator so as to provide an output voltage at an output of the at least one comparator representing a second signal state.

9. The method as recited in claim 8 wherein the second signal state is a switching state.

10. The method as recited in claim 8 further comprising controlling at least one switching device using the output voltage so as to switch the at least one switching device as a function of a level of the output voltage.

11. A circuit comprising a transformer configured to galvanically isolate signals and to have a pulse-width modulated voltage applied to a primary side thereof, a secondary side of the transformer being connected to a second circuit comprising:

a first series connection including a first and a second rectified diode, a first central potential of the first series connection being connected to a first end of a secondary coil of the transformer;

a second series connection including a first and a second capacitor, a second central potential of the second series connection being connected to a second end of the secondary coil of the transformer, the second series connection being connected in parallel with the first series connection; and

a load connected in parallel with the first and second series connections.

12. The circuit as recited in claim 11 further comprising an element connected in series with a primary coil of the transformer, the element being configured to suppress DC components through the primary coil.

13. The circuit as recited in claim 12 wherein the element includes a third capacitor.

14. The circuit as recited in claim 11 wherein the load includes at least one resistive load.

15. The circuit as recited in claim 14 wherein the resistive load includes a series connection of at least two ohmic resistors.

16. The circuit as recited in claim 11 wherein the load includes an electronic component.

17. The circuit as recited in claim 16 wherein the electronic component includes a comparator.

18. The circuit as recited in claim 11 further comprising a comparator configured to have a first input signal thereof derived from the second central potential.

19. The circuit as recited in claim 15 further comprising a comparator configured to have a second input signal thereof derived from a voltage tap at the series connection of the at least two ohmic resistors.

20. The circuit as recited in claim 11 further comprising at least one fourth capacitor connected in parallel with the first series connection, a capacitance of the fourth capacitor being larger than a respective capacitance of the first capacitor and of the second capacitor.

21. The circuit as recited in claim 20 wherein the capacitance of the fourth capacitor is at least 5 times larger than the respective capacitance of the first capacitor and of the second capacitor.

22. The circuit as recited in claim 21 wherein the capacitance of the fourth capacitor is 40 to 60 times larger than the respective capacitance of the first capacitor and of the second capacitor.

23. The circuit as recited in claim 20 wherein the load includes a comparator, at least one of a supply voltage of the comparator and a reference voltage for a second input signal of the comparator is derived from a voltage across the at least one fourth capacitor.

24. The circuit as recited in claim 11 further comprising at least one switching device, and wherein the load includes a comparator, an output signal of the comparator being applied to a control input of the at least one switching device.

25. The circuit as recited in claim 24 wherein the control input includes a gate of a field-effect transistor.

26. The circuit as recited in claim 25 wherein the field-effect transistor is a MOSFET.

27. The circuit as recited in claim 11 wherein the load includes a first comparator and a component, a second output signal of the component being inverted relative to a first output signal of the first comparator.

28. The circuit as recited in claim 27 wherein the component includes a second comparator having second inputs driven inversely relative to first inputs of the first comparator.