Drive circuit for a synchronous rectifier, method of providing drive signals thereto and power converter incorporating the same
View Patent ↗The present invention provides a transition-isolating drive circuit for a synchronous rectifier. In one embodiment, the transition-isolating drive circuit includes drive switches coupled to a transformer winding and configured to provide drive signals for the synchronous rectifier. Additionally, the transition-isolating drive circuit also includes a conduction-inhibiting circuit, coupled to the drive switches, that increases a turn-off voltage of the drive signals to a predetermined level.
1. A transition-isolating drive circuit for a synchronous rectifier, comprising:
drive switches coupled to a transformer winding and configured to provide drive signals for said synchronous rectifier; and
a conduction-inhibiting circuit, coupled to said drive switches, that increases a turn-off voltage of said drive signals to a predetermined level that substantially prevents the drive switches from simultaneously conducting.
2. The circuit as recited in claim 1 wherein said conduction-inhibiting circuit comprises a component that produces a reference voltage on which said predetermined level is based.
3. The circuit as recited in claim 2 wherein said component is a zener diode.
4. The circuit as recited in claim 3 wherein said conduction-inhibiting circuit further comprises a blocking diode series-coupled to said component.
5. The circuit as recited in claim 1 wherein said conduction-inhibiting circuit comprises a zener diode associated with each of said drive switches.
6. The circuit as recited in claim 1 further comprising a conduction-enhancing circuit, coupled to said drive switches, that limits a turn-on voltage of said drive signals to a predetermined level.
7. The circuit as recited in claim 1 wherein said transformer winding is a secondary winding and said circuit further comprises isolation capacitors interposing said secondary winding and said drive switches.
8. A method of providing drive signals to a synchronous rectifier, comprising:
employing an input voltage from a transformer winding to provide said drive signals to said synchronous rectifier; and
increasing a turn-off voltage of said drive signals to a predetermined level that substantially prevents the drive switches from simultaneously conducting.
9. The method as recited in claim 8 wherein said increasing is carried out by a component that produces a reference voltage on which said predetermined level is based.
10. The method as recited in claim 9 wherein said component is a zener diode.
11. The method as recited in claim 9 wherein a blocking diode is series-coupled to said component.
12. The method as recited in claim 8 wherein said increasing is carried out by a zener diode associated with each of said drive switches.
13. The method as recited in claim 8 further comprising limiting a turn-on voltage of said drive signals to a predetermined level.
14. The method as recited in claim 8 wherein said transformer winding is a secondary winding and said method further comprises isolating said secondary winding and said drive switches.
15. A power converter, comprising:
a main power switch coupled to a DC voltage source;
a transformer coupled to said main power switch;
a synchronous rectifier coupled to said transformer that provides a converter output; and
a transition-isolating drive circuit for said synchronous rectifier, including:
drive switches coupled to a winding of said transformer and configured to provide drive signals for said synchronous rectifier, and
a conduction-inhibiting circuit, coupled to said drive switches, that increases a turn-off voltage of said drive signals to a predetermined level that substantially prevents the drive switches from simultaneously conducting.
16. The power converter as recited in claim 15 wherein said conduction-inhibiting circuit comprises a component that produces a reference voltage on which said predetermined level is based.
17. The power converter as recited in claim 16 wherein said component is a zener diode.
18. The power converter as recited in claim 16 wherein said conduction-inhibiting circuit further comprises a blocking diode series-coupled to said component.
19. The power converter as recited in claim 15 wherein said conduction-inhibiting circuit comprises a zener diode associated with each of said drive switches.
20. The power converter as recited in claim 15 further comprising a conduction-enhancing circuit, coupled to said drive switches, that limits a turn-on voltage of said drive signals to a predetermined level.
21. The power converter as recited in claim 15 wherein said winding is a secondary winding and said circuit further comprises isolation capacitors interposing said secondary winding and said drive switches.