Processing

Please wait...

Settings

Settings

Goto Application

1. WO2020222889 - HIGH EFFICIENCY PASSIVE CLAMP

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

CLAIMS

1. A circuit having primary and secondary sides, the circuit comprising:

a flyback power converter including an input voltage source and a transformer having primary and secondary windings on the primary and secondary sides, respectively;

a main switch in series with the primary winding on the primary side; and

a passive clamp circuit across the main switch, the passive clamp circuit comprising a clamp diode, a clamp capacitor, and an auxiliary circuit comprising first and second rectifiers in series with each other and in series with an electronic component configured to store electromagnetic energy, the electronic component having first and second terminals;

wherein a cathode of the first rectifier is connected with the passive clamp circuit, and an anode of the first rectifier is connected to the second terminal of electronic component;

wherein an anode of the second rectifier is connected with the cathode of the first rectifier, and a cathode of the second rectifier is connected with the first terminal of the electronic component.

2. The circuit of claim 1, wherein the auxiliary circuit is configured to reduce an RMS current through the clamp capacitor from a first current value to a second current value which is at least thirty percent lower than the first current value, and to reduce a charge through the clamp capacitor from a first charge value to a second charge value which is at least thirty percent lower than the first charge value.

3. The circuit of claim 2, wherein the clamp diode is formed by several diodes in parallel.

4. The circuit of claim 3, wherein the first rectifier is in series with a resistor.

5. The circuit of claim 2, wherein the first rectifier is in series with a resistor.

6. The circuit of claim 5, wherein the electronic component includes a voltage source, the first terminal is a positive terminal of the voltage source, and the second terminal is a negative terminal of the voltage source.

7. The circuit of claim 5, wherein the electronic component includes a voltage source, and the voltage source provides a bias voltage to the flyback power converter.

8. The circuit of claim 5, wherein the electronic component includes a bias voltage source for the flyback power converter including:

a bias winding in the transformer, the bias winding coupled with the primary winding of the transformer and having first and second terminals;

a bias synchronous rectifier having a gate and a drain, wherein the drawn of the bias synchronous rectifier is connected to the first terminal of the bias winding; and

a bias capacitor connected to the second terminal of the bias winding and to the source of the bias synchronous rectifier.

9. The circuit of claim 1, further comprising a resistor connected between the positive terminal of the input voltage source and a junction between the clamp capacitor and clamp diode.

10. A method of operating a circuit having primary and secondary sides, the method comprising:

providing a flyback power converter including an input voltage source and a transformer having primary and secondary windings on the primary and second sides, respectively;

providing a main switch in series with the primary winding on the primary side;

providing a synchronous rectifier in series with the secondary winding on the secondary side;

providing a passive clamp circuit across the main switch, the passive clamp circuit comprising a clamp diode and a clamp capacitor in series with the clamp diode;

wherein the circuit is characterized by an electrical charge, injected into the clamp capacitor after the main switch is turned off, the electrical charge having a first charge value;

electrically connecting the circuit with an auxiliary circuit in series with the clamp capacitor, wherein:

the auxiliary circuit comprises an auxiliary energy storage, first and second rectifiers in series with each other, and an electronic component configured to store electromagnetic energy in series with the first and second rectifiers;

a cathode of the first rectifier is connected with the passive clamp circuit, and an anode of the first rectifier is connected to the second terminal of electronic component; and

an anode of the second rectifier is connected with the cathode of the first rectifier, and a cathode of the second rectifier is connected with the first terminal of the electronic component;

directing a current, flowing through a leakage inductance reflected in the primary side of the transformer, to flow through the clamp capacitor and through the second rectifier toward the auxiliary energy storage, so as to change the first charge value, thereby imparting a second charge value to flow through the first rectifier during a reverse recovery time of the clamp diode, so as to balance the electrical charge in the clamp capacitor.

11. The method of claim 10, wherein the step of electrically connecting further includes connecting the auxiliary energy storage between a ground and the cathode of the second rectifier.

12. The method of claim 11, wherein the step of electrically connecting further includes connecting the anode of the first rectifier to the ground via a resistor.

13. The circuit of claim 10, further comprising a resistor connected between a positive terminal of the input voltage source and a junction between the clamp capacitor and clamp diode.

14. A circuit having primary and secondary sides, the circuit comprising:

a flyback power converter including an input voltage source having positive and negative terminals, a transformer having primary and secondary windings on the primary and secondary sides, respectively;

a main switch in series with the primary winding on the primary side;

a parasitic capacitor across the main switch;

a synchronous rectifier in series with the secondary winding on the secondary side;

a passive clamp circuit across the main switch, the passive clamp circuit comprising a clamp diode, a clamp capacitor in series with the clamp diode, a resistor connected between the positive terminal of the input voltage source and a junction between the clamp capacitor and clamp diode; and

first and second rectifiers in series with each other and in series with an electronic component configured to store electromagnetic energy;

wherein a cathode of the first rectifier is connected with the passive clamp circuit, and an anode of the first rectifier is connected to a second terminal of electronic component; and

wherein an anode of the second rectifier is connected with the cathode of the first rectifier, and a cathode of the second rectifier is connected with a first terminal of the electronic component.

15. The circuit of claim 14, further comprising a resistor in series with the first rectifier.

16. The circuit of claim 14, further comprising:

a current injection circuit including a current injection winding in the transformer having first and second terminals;

a current injection switch connected to the first terminal of the current injection winding;

a current injection diode, with a cathode connected to the second terminal of the current injection winding, and an anode connected to the electronic component configured to store electromagnetic energy;

an energy source to collect energy of a leakage inductance of the transformer via the passive clamp circuit and second rectifier; and

the current injection winding configured to inject the energy as a pulse of current into the transformer via the current injection winding, so as to discharge the parasitic capacitor to create a zero voltage switching condition for the main switch.

17. The circuit of claim 16, further comprising a resonant capacitor between the second terminal of the current injection winding and the current injection switch at a terminal of current injection switch which is not connected to the current injection winding.

18. The circuit of claim 16, further comprising a bias diode having an anode, connected to the second terminal of the electronic component, and a cathode, connected to a bias voltage.

19. The circuit of claim 16, wherein the clamp diode comprises at least two diodes in parallel.

20. The circuit of claim 19, wherein the current injection switch turns on when a voltage across the main switch reaches its lowest amplitude, and the main switch turns on when the voltage across the main switch reaches a predetermined value.

21. The circuit of claim 20, wherein the predetermined value is zero.

22. A circuit having primary and secondary sides, the circuit comprising:

an input voltage source connected to a primary winding of a transformer, the transformer having additional windings;

a leakage inductance between the primary winding and the additional windings;

a main switch in series with the primary winding, wherein a magnetizing current of the transformer has a low impedance path to further circulate after the main switch turns off; and

a passive clamp circuit comprised of a diode and a capacitor in series, wherein the passive clamp circuit is connected to an energy extraction circuit comprising first and second rectifiers connected in series with each other and in series with an electronic component configured to store electromagnetic energy;

wherein a cathode of the first rectifier is connected with the passive clamp circuit, and an anode of the first rectifier is connected to a second terminal of electronic component;

wherein an anode of the second rectifier is connected with the cathode of the first rectifier, and a cathode of the second rectifier is connected with a first terminal of the electronic component.

23. The circuit of claim 22, further comprising:

a current injection circuit including a current injection winding in the transformer having first and second terminals;

a current injection switch connected to the first terminal of the current injection winding;

a current injection diode, with a cathode connected to the second terminal of the current injection winding, and an anode connected to the electronic component configured to store electromagnetic energy;

an energy source to collect energy of a leakage inductance of the transformer via the passive clamp circuit and second rectifier; and

the current injection winding configured to inject the energy as a pulse of current into the transformer via the current injection winding, so as to discharge the parasitic capacitor to create a zero voltage switching condition for the main switch.

24. The circuit of claim 22, further comprising a resistor in series with the first rectifier.

25. The circuit of claim 22, further comprising a resistor connected between a positive terminal of the input voltage source and a junction between the capacitor and diode.

26. A DC-DC converter comprising:

an input voltage source in series with a parasitic capacitance, wherein a voltage of the input voltage source changes sufficiently abruptly to cause resonant ringing, wherein the input voltage source is connected to a rectifier means which is connected to an output circuit;

a passive clamp circuit across the rectifier means, wherein the passive clamp circuit comprises a clamp diode, a clamp capacitor, and an auxiliary circuit, said auxiliary circuit comprising first and second rectifiers in series with each other and in series with an electronic component configured to store electromagnetic energy, the electronic component having first and second terminals;

wherein a cathode of the first rectifier is connected with the passive clamp circuit, and an anode of the first rectifier is connected to the second terminal of the electronic component;

wherein an anode of the second rectifier is connected with the cathode of the first rectifier, and a cathode of the second rectifier is connected with the first terminal of the electronic component; and

wherein directing a current, flowing through a leakage inductance, to flow through the clamp capacitor and through the second rectifier toward the auxiliary energy storage, causes some of the leakage inductance to transfer to an auxiliary energy storage and damps the resonant ringing.

27. The DC-DC converter of claim 26, wherein the anode of the first rectifier is connected to a ground via a resistor.

28. The DC-DC converter of claim 26, wherein the electronic component includes a voltage source which provides a bias voltage to the DC-DC converter.