Phase-cut pre-regulator and power supply comprising the same

1. A phase-cut pre-regulator comprising:

a switching device connected between a rectifier and a bulk capacitor; and

a comparator that is connected to an output of the rectifier to receive a full-wave rectified AC line voltage from the rectifier, the comparator being configured, to compare the full-wave rectified AC line voltage with a plurality of hysteresis reference voltages that are based on a reference voltage, to turn-off the switching device at least once in each cycle of the full-wave rectified AC line voltage according to a result of comparing the full-wave rectified AC line voltage with a first hysteresis reference voltage in the plurality of hysteresis reference voltages to disconnect the full-wave rectified AC line voltage from the bulk capacitor, and to turn-on the switching device at least once in each cycle of the full-wave rectified AC line voltage according to a result of comparing the full-wave rectified AC line voltage with a second hysteresis reference voltage in the plurality of hysteresis reference voltages to connect the full-wave rectified AC line voltage to the bulk capacitor.

2. The phase-cut pre-regulator of claim 1 , wherein the comparator is configured to output a switching signal to turn-off the switching device to stop charging the bulk capacitor with the full-wave rectified AC line voltage when the full-wave rectified AC line voltage is higher than the first hysteresis reference voltage.

3. The phase-cut pre-regulator of claim 2 , wherein the comparator is configured to output the switching signal to turn-on the switching device and charge the bulk capacitor with the full-wave rectified AC line voltage when the full-wave rectified AC line voltage is lower than the second hysteresis reference voltage.

4. The phase-cut pre-regulator of claim 3 , wherein the first hysteresis reference voltage is higher than the second hysteresis reference voltage.

5. The phase-cut pre-regulator of claim 1 , wherein the bulk capacitor is charged by the rectified AC line voltage in a turn-on time of the switching device when the switching device is turned on and energy stored in the bulk capacitor is discharged in a turn-off time of the switching device when the switching device is turned off.

6. The phase-cut pre-regulator of claim 1 , wherein the rectifier comprise a bridge rectifier.

7. A power supply comprising:

a rectifier circuit that defines a first output terminal and a second output terminal, the rectifier circuit configured to rectify an AC input into a rectified AC line voltage at the first and second output terminals;

a bulk capacitor having a first terminal and a second terminal, the first terminal of the bulk capacitor coupled to the first output terminal of the rectifier circuit;

a switching device connected between the second output terminal of the rectifier circuit and the second terminal of the bulk capacitor; and

a comparator that is configured, for each cycle of the rectified AC line voltage, to compare the rectified AC line voltage with a plurality of hysteresis reference voltages, and to turn the switching device on and off at least once in each cycle of rectified AC line voltage according to a result of comparing the rectified AC line voltage to the plurality of hysteresis reference voltages.

8. The power supply of claim 7 , wherein the comparator is configured to output a switching signal to turn-off the switching device when the line voltage is higher than a first hysteresis reference voltage in the plurality of hysteresis reference voltages.

9. The power supply of claim 8 , wherein the comparator is configured to output the switching signal to turn-on the switching device when the line voltage is lower than a second hysteresis reference voltage in the plurality of hysteresis reference voltages.

10. The power supply of claim 9 , wherein the first hysteresis reference voltage is higher than the second hysteresis reference voltage.

11. The power supply of claim 7 , wherein the bulk capacitor is charged by the rectified AC line voltage when the switching device is turned on and energy stored in the bulk capacitor is discharged when the switching device is turned off.

12. A power supply comprising:

a first rectifier circuit that defines a first output terminal and a second output terminal, the rectifier circuit configured to rectify a first phase AC input of a multi-phase AC input to generate a first rectified AC line voltage across the first and second output terminals;

a bulk capacitor having a first terminal and a second terminal, the first terminal of the bulk capacitor coupled to the first output terminal of the first rectifier circuit;

a first switching device connected between the second output terminal of the rectifier circuit and the second terminal of the bulk capacitor; and

a first comparator that is configured, for each cycle of the first rectified AC line voltage, to receive the first rectified AC line voltage and a reference voltage, to compare the first rectified AC line voltage with a plurality of hysteresis reference voltages that are based on the reference voltage, and to switch the first switching device on and off at least once in each cycle of the first rectified AC line voltage according to a result of comparing the first rectified AC line voltage with the plurality of hysteresis reference voltages.

13. The power supply of claim 12 , wherein the first rectifier comprises:

a first diode connected to the first phase AC input and the first switching device; and

a second diode connected to the first phase AC input and a ground.

14. The power supply of claim 12 , wherein the first comparator is configured to output a first switching signal to turn-off the first switching device when the first rectified AC line voltage is higher than a first hysteresis reference voltage in the plurality of hysteresis reference voltages.

15. The power supply of claim 14 , wherein the first comparator is configured to output the first switching signal to turn-on the first switching device when the first rectified AC line voltage is lower than a second hysteresis reference voltage in the plurality of hysteresis reference voltages.

16. The power supply of claim 15 , wherein the first hysteresis reference voltage is higher than the second hysteresis reference voltage.

17. A power supply comprising:

a first rectifier circuit that is configured to rectify a first phase AC input of a multi-phase AC input to generate a first rectified AC line voltage;

a bulk capacitor;

a first switching device connected between the first rectified AC line voltage and the bulk capacitor; and

a first comparator that is configured, for each cycle of the first rectified AC line voltage, to receive the first rectified AC line voltage and a reference voltage, to compare the first rectified AC line voltage with a plurality of hysteresis reference voltages that are based on the reference voltage, and to switch the first switching device according to a result of comparing the first rectified AC line voltage with the plurality of hysteresis reference voltages;

a second rectifier circuit that is configured to rectify a second phase AC input of the multi-phase AC input to generate a second rectified AC line voltage;

a second switching device connected between the second rectified AC line voltage and the bulk capacitor; and

a second comparator that is configured, for each cycle of the second rectified AC line voltage, to receive the second rectified AC line voltage and the reference voltage, to compare the second rectified AC line voltage with the plurality of hysteresis reference voltages, and to switch the second switching device according to a result of comparing the second rectified AC line voltage with the plurality of hysteresis reference voltages.

18. The power supply of claim 17 , wherein the second rectifier comprises:

a third diode connected to the second phase AC input and the second switching device; and

at least a fourth diode connected to the second phase AC input and a ground.

19. The power supply of claim 17 , wherein the second comparator is configured to output a second switching signal to turn-off the second switching device when the second rectified AC line voltage is higher than a first hysteresis reference voltage in the plurality of hysteresis reference voltages.

20. The power supply of claim 19 , wherein the second comparator is configured to output the second switching signal to turn-on the second switching device when the second rectified AC line voltage is lower than a second hysteresis reference voltage in the plurality of hysteresis reference voltages.