Zero voltage switching detection apparatus and method
A converter comprises a switch network coupled to a power source, wherein the switch network comprises a plurality of power switches, a magnetic device coupled to the switch network, a detector coupled to the magnetic device through a magnetic coupling and a control circuit configured to receive a zero voltage switching signal from the detector and adjust gate drive signals of the power switches based upon the zero voltage switching signal.
1. A converter comprising:
a switch network coupled to a power source, wherein the switch network comprises a plurality of power switches;
a magnetic device coupled to the switch network;
a detector coupled to the magnetic device through a magnetic coupling, wherein a continuous current flowing through a primary side of the magnetic coupling is proportional to a current flowing through a power inductor of the converter, and wherein the detector comprises a dc blocking capacitor having a first terminal connected to a secondary side of the magnetic coupling, a diode and a resistor connected in series and further coupled to a second terminal of the dc blocking capacitor, and a voltage divider coupled to the second terminal of the dc blocking capacitor; and
a control circuit configured to receive a zero voltage switching signal from the detector and adjust gate drive signals of the power switches based upon the zero voltage switching signal.
2. The converter of claim 1 , wherein the magnetic coupling is implemented as a signal transformer, and wherein:
a primary side of the signal transformer is the magnetic device; and
a secondary side of the signal transformer is coupled to the detector.
3. The converter of claim 2 , wherein:
the dc blocking capacitor is connected to the secondary side of the signal transformer.
4. The converter of claim 3 , wherein:
the control circuit is configured to turn on a power switch of the switch network after the zero voltage switching signal drops below a predetermined threshold.
5. The converter of claim 4 , wherein:
the predetermined threshold is in a range from about 0.5 V to about 1.0 V.
6. The converter of claim 4 , wherein:
a voltage across the power switch is approximately equal to zero when the power switch is turned on.
7. The converter of claim 1 , wherein the switch network comprises:
a first power switch and a second power switch connected in series between two terminals of the power source, wherein a common node of the first power switch and the second power switch is connected to the magnetic device.
8. The converter of claim 1 , wherein the switch network comprises:
a first power switch and a second power switch connected in series between two terminals of an output capacitor, wherein a common node of the first power switch and the second power switch is connected to the magnetic device.
9. The converter of claim 1 , wherein the switch network comprises:
a first power switch and a second power switch connected in series between two terminals of the power source, and wherein a common node of the first power switch and the second power switch is connected to a first terminal of the magnetic device; and
a third power switch and a fourth power switch connected in series between two terminals of an output capacitor, and wherein a common node of the third power switch and the fourth power switch is connected to a second terminal of the magnetic device.
10. The converter of claim 1 , wherein:
the magnetic device is an inductor.
11. A method comprising:
providing a power converter, wherein the power converter comprises:
an inductor coupled to a switch network;
a detector coupled to the inductor through a magnetic coupling, wherein a continuous current flowing through a primary side of the magnetic coupling is proportional to a current flowing through the inductor, and wherein the detector comprises a dc blocking capacitor having a first terminal connected to a secondary side of the magnetic coupling, a diode and a resistor connected in series and further coupled to a second terminal of the dc blocking capacitor, and a voltage divider coupled to the second terminal of the dc blocking capacitor; and
a control circuit coupled between the detector and the switch network;
detecting a signal indicating a soft switching process of a power switch of the switch network; and
turning on the power switch after a magnitude of the signal is less than a predetermined threshold.
12. The method of claim 11 , further comprising:
detecting the signal indicating a soft switching process of the power switch, wherein the signal is measured from the inductor through the magnetic coupling, and wherein the magnetic coupling is implemented as a signal transformer, and wherein:
a primary side of the signal transformer is the inductor; and
a secondary side of the signal transformer is coupled to the detector.
13. The method of claim 12 , wherein:
the dc blocking capacitor is connected to the secondary side of the signal transformer.
14. The method of claim 13 , further comprising:
receiving the signal indicating the soft switching process of the power switch through the signal transformer; and
scaling the signal down to a level suitable for the control circuit through the voltage divider.
15. The method of claim 11 , wherein:
the power converter is a non-isolated dc/dc converter.
16. A method comprising:
providing a dc/dc converter, wherein the dc/dc converter comprises:
a switch network coupled to a power source, wherein the switch network comprises a plurality of power switches;
a magnetic device coupled to the switch network;
a detector coupled to the magnetic device through a magnetic coupling, wherein a continuous current flowing through a primary side of the magnetic coupling is proportional to a current flowing through a power inductor of the dc/dc converter, and wherein the detector comprises a dc blocking capacitor having a first terminal connected to a secondary side of the magnetic coupling, a diode and a resistor connected in series and further coupled to a second terminal of the dc blocking capacitor, and a voltage divider coupled to the second terminal of the dc blocking capacitor; and
a control circuit coupled between the detector and the switch network;
detecting a signal indicating a zero voltage switching process of a power switch of the dc/dc converter; and
turning on the power switch by the control circuit after the signal indicating the zero voltage switching process drops below a predetermined threshold.
17. The method of claim 16 , further comprising:
coupling the detector to the magnetic device through a signal transformer, wherein a primary side of the signal transformer is an inductor of a buck dc/dc converter.
18. The method of claim 16 , further comprising:
coupling the detector to the magnetic device through a signal transformer, wherein a primary side of the signal transformer is an inductor of a boost dc/dc converter.
19. The method of claim 16 , wherein:
coupling the detector to the magnetic device through a signal transformer, wherein a primary side of the signal transformer is an inductor of a buck-boost dc/dc converter.
20. The method of claim 19 , wherein:
the buck-boost dc/dc converter is a four-switch buck-boost dc/dc converter.