Mobile device adapter and charger

1. A power adapter comprising:

an AC input;

a rectifier coupled to the AC input;

a power factor correction circuit coupled to the rectifier; and

a burst switch circuit coupled to the power factor correction circuit, wherein the burst switch circuit provides power to a DC output via a set of FET drivers, a set of FETs, and a transformer, and wherein the burst switch circuit provides power exclusively in a burst mode using a feedback input from the DC output;

wherein the transformer comprises a first winding coupled to the set of FETs, and second, third, fourth, and fifth windings each coupled to the first winding;

wherein the second winding and the third winding are embedded in a printed circuit board; and

wherein the fourth and fifth winding each comprise a conductive ribbon that loops around a transformer core.

2. The power adapter of claim 1 further comprising a power adapter housing enclosing the power adapter such that the power density of the power adapter enclosed by the power adapter housing is greater than 12 W/cubic inch.

3. The power adapter of claim 2 further comprising a high voltage line coupled to a bus output of the power factor correction circuit.

4. The power adapter of claim 3 further comprising a diode coupled to a transistor, wherein the transistor is further coupled to the high voltage line.

5. The power adapter of claim 4 further comprising a comparator coupled the set of FET drivers and a comparison voltage input.

6. The power adapter of claim 5 wherein the diode and the transistor operate at a start-up of the power adapter to create a low voltage backup that provides operating power to the set of FET drivers at the start-up of the power adapter.

7. The power adapter of claim 6 wherein the second winding creates a FET driver operating voltage that replaces the low voltage backup in providing power to the set of FET drivers when the second winding is driven by the first winding.

8. The power adapter of claim 7 wherein the comparator compares a first comparison voltage from the comparison voltage input with the FET driver operating voltage.

9. The power adapter of claim 8 wherein an output of the comparator is coupled to the transistor to maintain the low voltage backup when the FET driver operating voltage drops below a predetermined threshold set by the first comparison voltage.

10. The power adapter of claim 9 further comprising a USB switcher coupled to the DC output that drives a USB voltage and a USB current to a first USB output and a second USB output.

11. The power adapter of claim 10 further comprising a first monitoring circuit that monitors the USB current and activates a fault input of the power factor correction circuit when the USB current exceeds a current threshold.

12. The power adapter of claim 11 further comprising a second monitoring circuit that monitors the USB voltage and activates the fault input of the power factor correction circuit when the USB voltage exceeds a voltage threshold.

13. The power adapter of claim 12 further comprising a third monitoring circuit that activates the fault input of the power factor correction circuit when a DC output voltage of the DC output exceeds a DC voltage threshold.

14. A high power density multi-output power adapter system comprising:

an AC input;

a rectifier coupled to the AC input;

a power factor correction circuit coupled to the rectifier;

a burst switch circuit coupled to the power factor correction circuit, wherein the burst switch circuit provides power to a DC output via a set of FET drivers, a set of FETs, and a transformer, and wherein the burst switch circuit provides power exclusively in a burst mode using a feedback input from the DC output; and

a USB switcher coupled to the DC output that drives a USB voltage and a USB current to a first USB output and a second USB output; and

a power adapter housing enclosing the power adapter system such that the power density of the power adapter enclosed by the power adapter housing is greater than 12 W/cubic inch.

15. The high power density multi-output power adapter system of claim 14 wherein the transformer comprises a first winding coupled to the set of FETs, and second, third, fourth, and fifth windings each coupled to the first winding;

wherein the second winding and the third winding are embedded in a printed circuit board; and

wherein the fourth and fifth winding each comprise a conductive ribbon that loops around a transformer core.

16. The high power density multi-output power adapter system of claim 15 further comprising:

a first monitoring circuit that monitors the USB current and activates a fault input of the power factor correction circuit when the USB current exceeds a current threshold;

a second monitoring circuit that monitors the USB voltage and activates the fault input of the power factor correction circuit when the USB voltage exceeds a voltage threshold; and

a third monitoring circuit that activates the fault input of the power factor correction circuit when a DC output voltage of the DC output exceeds a DC voltage threshold.

17. The high power density multi-output power adapter system of claim 14 further comprising a high voltage line coupled to a bus output of the power factor correction circuit;

a diode coupled to a transistor, wherein the transistor is further coupled to the high voltage line; and

a comparator;

wherein the diode and the transistor operate at a start-up of the power adapter to create a low voltage backup that provides operating power to the set of FET drivers at the start-up of the power adapter;

wherein the second winding creates a FET driver operating voltage that replaces the low voltage backup in providing power to the set of FET drivers when the second winding is driven by the first winding; and

wherein the comparator compares a first comparison voltage with the FET driver operating voltage and the output of the comparator is coupled to the transistor to maintain the low voltage backup when the FET driver operating voltage drops below a predetermined threshold set by the first comparison voltage.

18. The high power density multi-output power adapter system of claim 17 further comprising an opto-coupler coupled to the comparator output, wherein the opto-coupler provides digital feedback information to a primary side of the adapter across an isolation barrier created by the transformer.

19. The high power density multi-output power adapter system of claim 15 wherein a core of the transformer is a Feroxcube EQ core.

20. The high power density multi-output power adapter system of claim 19 wherein the core of the transformer is attached to a circular PCB section of a PCB on which the burst switcher circuit is mounted, and wherein the windings of the transformer are set in an interleaving arrangement around the circular PCB section.