Method and apparatus for over-current protection and CrCM control in power converters
A power converter includes an input coupled to an inductor, a first switch coupled to a first comparator, and a second switch coupled to a second comparator. The power converter also includes a pulse comparison counter coupled to the first comparator and the second comparator and a synchronous rectifier (SR) calculator coupled to the pulse comparison counter. The synchronous rectifier calculator is operable to modify a conduction time of the first switch during a first AC half-cycle and modify a conduction time of the second switch during a second AC half-cycle.
1. A power converter comprising:
an input coupled to an inductor;
a first switch coupled to a first comparator;
a second switch coupled to a second comparator;
a pulse comparison counter coupled to the first comparator and the second comparator; and
a synchronous rectifier (SR) calculator coupled to the pulse comparison counter;
wherein the SR calculator is operable to:
modify a conduction time of the first switch during a first AC half-cycle; and
modify a conduction time of the second switch during a second AC half-cycle.
2. The power converter of claim 1 further comprising:
a first current sense resistor electrically coupled to the first switch; and
a second current sense resistor electrically coupled to the second switch.
3. The power converter of claim 1 wherein the power converter comprises a bridgeless, totem-pole boost power factor correction power converter.
4. The power converter of claim 1 wherein the power converter supports bidirectional inductor current.
5. The power converter of claim 1 further comprising a current sense amplifier electrically coupled to the first switch and the first comparator.
6. The power converter of claim 1 further comprising a current sense amplifier electrically coupled to the second switch and the second comparator.
7. The power converter of claim 6 further comprising level shifter electrically coupled to the second comparator.
8. The power converter of claim 1 , wherein the pulse comparison counter is configured to output a triangular current mode (TCM) pulse count.
9. The power converter of claim 8 , wherein the SR calculator is configured to receive a switching pulse (SP) pulse count, and wherein the SR calculator comprises:
a pulse count subtractor operable to determine a difference between the TCM pulse count and the SP pulse count; and
a third comparator coupled with the pulse count subtractor and operable to compare an output of the pulse count subtractor with a threshold, wherein the SR calculator is operable to:
modify the conduction time of the first switch based on the comparison of the third comparator; and
modify the conduction time of the second switch based on the comparison of the third comparator.
10. The power converter of claim 9 , wherein the SR calculator is operable to:
determine a modifier based on the comparison of the third comparator;
modify the conduction time of the first switch based on the determined modifier; and
modify the conduction time of the second switch based on the determined modifier.
11. A power converter, comprising:
an input coupled to an inductor;
a first switch coupled to the inductor;
a current sense resistor electrically coupled to the first switch;
a current sense amplifier electrically coupled to the current sense resistor and a comparator;
a pulse comparison counter coupled to the comparator; and
a synchronous rectifier (SR) calculator coupled to the pulse comparison counter,
wherein the SR calculator is operable to:
determine a modifier based on an output of the pulse comparison counter; and
modify, based on the determined modifier, a conduction time of the first switch during an AC half-cycle.
12. The power converter of claim 11 , wherein the power converter comprises a bridgeless, totem-pole boost power factor correction power converter.
13. The power converter of claim 11 , wherein the power converter supports bidirectional inductor current.
14. The power converter of claim 11 , further comprising:
a second switch coupled to the inductor;
a second current sense resistor electrically coupled to the second switch;
a second comparator coupled to the pulse comparison counter;
a second current sense amplifier electrically coupled to the second current sense resistor and the second comparator; and wherein the SR calculator is operable to:
modify, based on the determined modifier, a conduction time of the second switch during a first AC half-cycle, wherein the conduction time of the first switch is modified during a second AC half-cycle.
15. The power converter of claim 11 , further comprising level shifter electrically coupled to the comparator.
16. The power converter of claim 11 , wherein the pulse comparison counter is configured to output a triangular current mode (TCM) pulse count.
17. The power converter of claim 16 , wherein the SR calculator is configured to receive a switching pulse (SP) pulse count, and wherein the SR calculator comprises:
a pulse count subtractor operable to determine a difference between the TCM pulse count and the SP pulse count; and
a third comparator coupled with the pulse count subtractor and operable to compare an output of the pulse count subtractor with a threshold, wherein the SR calculator is operable to determine the modifier based on a comparison of the third comparator.
18. A power converter, comprising:
an input coupled to an inductor;
a first switch coupled to the inductor and a comparator;
a pulse comparison counter coupled to the comparator, wherein the pulse comparison counter is configured to output a triangular current mode (TCM) pulse count; and
a synchronous rectifier (SR) calculator coupled to the pulse comparison counter,
wherein the SR calculator comprises:
a pulse count subtractor operable to determine a difference between the TCM pulse count and a switching pulse (SP) pulse count; and
a second comparator coupled with the pulse count subtractor and operable to compare an output of the pulse count subtractor with a threshold, wherein the SR calculator is operable to modify a conduction time of the first switch based on the comparison of the second comparator.
19. The power converter of claim 18 , wherein the SR calculator is operable to:
determine a modifier based on the comparison of the second comparator; and
modify, based on the determined modifier, the conduction time of the first switch during an AC half-cycle.
20. The power converter of claim 18 , comprising:
a second switch coupled to the inductor;
a third comparator coupled to the second switch and the pulse comparison counter, wherein the SR calculator is operable to:
modify the conduction time of the switch during a first AC half-cycle; and
modify, based on the comparison of the second comparator, a conduction time of the second switch during a first AC half-cycle, wherein the conduction time of the first switch is modified during a second AC half-cycle.