Switching Regulator with Increased Light Load Efficiency

• US 20130027009A1
• Filed: 07/29/2011
• Published: 01/31/2013
• Est. Priority Date: 07/29/2011
• Status: Active Grant

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Primarion Incorporated (Infineon Technologies AG)
• Inventors: Tang, Benjamim, Babazadeh, Amir, Ostrom, Kenneth A., Bernacchia, Giuseppe
• Granted Patent: US 8,896,280 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A switching regulator includes a multiphase converter which includes a plurality of main phases configured to covert a power supply voltage to a lower voltage for application to an electronic device at different load conditions. The switching regulator also includes an auxiliary phase configured to operate in a pulse frequency modulation mode during a light load condition so that power is supplied to the electronic device by at least the auxiliary phase during the light load condition.

Claims

1. A switching regulator, comprising:

a multiphase buck converter comprising a plurality of main phases configured to covert a power supply voltage to a lower voltage for application to an electronic device at different load conditions; and

an auxiliary phase configured to operate in a pulse frequency modulation mode during a light load condition so that power is supplied to the electronic device by at least the auxiliary phase during the light load condition.

2. The switching regulator according to claim 1, wherein the auxiliary phase and the plurality of main phases of the multiphase buck converter comprise field effect transistors each having a gate drive voltage and a gate capacitance, and wherein the auxiliary phase has a lower gate drive voltage and lower gate capacitance than the plurality of main phases of the multiphase buck converter.

3. The switching regulator according to claim 1, wherein the auxiliary phase and each of the plurality of main phases of the multiphase buck converter has an output coupled to an inductor, and wherein the inductor coupled to the output of the auxiliary phase has a larger inductance and a lower saturation current than the inductors coupled the output of the main phases.

4. The switching regulator according to claim 1, further comprising a controller operable to control the multiphase buck converter and the auxiliary phase, wherein the controller is coupled to a power supply voltage lower than the power supply voltage coupled to the plurality of main phases of the multiphase buck converter and the auxiliary phase is coupled to the same power supply voltage as the controller.

5. The switching regulator according to claim 4, wherein the controller and the auxiliary phase are integrated on the same die.

6. The switching regulator according to claim 1, wherein a single main phase of the multiphase buck converter is activated in a continuous current mode or a discontinuous current mode and the other main phases are deactivated during the light load condition.

7. The switching regulator according to claim 6, wherein the single main phase of the multiphase buck converter is configured to transition from the continuous current mode to the discontinuous current mode responsive to a decrease in the load condition and the auxiliary phase remains operational in the pulse frequency modulation mode.

8. The switching regulator according to claim 1, wherein the auxiliary phase is configured to be deactivated responsive to a command from the electronic device indicating the auxiliary phase is to be deactivated.

9. The switching regulator according to claim 1, wherein the auxiliary phase is configured to be deactivated responsive to an increase in the load condition.

10. The switching regulator according to claim 1, wherein the auxiliary phase is configured to remain operational in the pulse frequency modulation mode regardless of how many main phases of the multiphase buck converter are activated.

11. The switching regulator according to claim 1, wherein pulse frequency modulation pulses are applied to the auxiliary phase responsive to the load current or load voltage falling below a threshold.

12. The switching regulator according to claim 11, wherein the pulse frequency modulation pulses are on for a first period of time and off for a second period of time such that a current in an inductor coupled to the output of the auxiliary phase reaches zero by the end of the second time period.

13. The switching regulator according to claim 11, wherein pulse frequency modulation pulses are applied to only a single main phase of the multiphase buck converter responsive to the load current or load voltage falling below the threshold, and wherein the threshold at which the pulse frequency modulation pulses are applied to the auxiliary phase is higher than the threshold at which the pulse frequency modulation pulses are applied to the single main phase of the multiphase buck converter.

14. The switching regulator according to claim 11, wherein the auxiliary phase comprises a high-side switch and a low-side switch, and wherein both switches are configured to remain in a high-impedance off-state after the load current or load voltage falls below the corresponding threshold until at least a current in an inductor coupled to the output of the auxiliary phase reaches zero before the high-side switch is turned on.

15. The switching regulator according to claim 14, wherein the thresholds are voltage thresholds.

16. The switching regulator according to claim 1, further comprising a monitor operable to determine whether the output of the auxiliary phase in the pulse frequency modulation mode violates a load criterion over a predefined interval, and if so, to generate a signal indicating one or more previously deactivated ones of the main phases of the multiphase buck converter are to be activated.

17. A power supply circuit, comprising:

a multiphase converter comprising a plurality of main phases coupled to a first power supply voltage and configured to covert the first power supply voltage to a lower voltage for application to an electronic device at different load conditions;

an auxiliary phase coupled to a second power supply voltage lower than the first power supply voltage and configured to operate during a light load condition so that power is supplied to the electronic device by at least the auxiliary phase during the light load condition; and

a controller operable to control operation of the multiphase converter and the auxiliary phase, the controller and the auxiliary phase being integrated on the same die.

18. The power supply circuit according to claim 17, wherein the auxiliary phase is configured to operate in a pulse frequency modulation mode during the light load condition.

19. The power supply circuit according to claim 17, wherein the auxiliary phase and the controller are coupled to the same power supply voltage.

20. A method of operating a switching regulator, comprising:

controlling a plurality of main phases of a multiphase converter so that a power supply voltage applied to the plurality of main phases is converted to a lower voltage for application to an electronic device at different load conditions; and

operating an auxiliary phase in a pulse frequency modulation mode during a light load condition so that power is supplied to the electronic device by at least the auxiliary phase during the light load condition.

21. The method according to claim 20, comprising enabling a single main phase of the multiphase converter in a continuous current mode or a discontinuous current mode and disabling the other main phases during the light load condition.

22. The method according to claim 21, comprising switching the single main phase of the multiphase converter from the continuous current mode to the discontinuous current mode responsive to a decrease in the load condition while maintaining the auxiliary phase in the pulse frequency modulation mode.

23. The method according to claim 20, comprising disabling the auxiliary phase responsive to a command from the electronic device indicating the auxiliary phase is to be deactivated.

24. The method according to claim 20, comprising disabling the auxiliary phase responsive to an increase in the load condition.

25. The method according to claim 20, comprising maintaining the auxiliary phase in the pulse frequency modulation mode regardless of how many main phases of the multiphase converter are activated.

26. The method according to claim 20, comprising applying pulse frequency modulation pulses to the auxiliary phase responsive to the load current or load voltage falling below a threshold.

27. The method according to claim 26, comprising applying pulse frequency modulation pulses to only a single main phase of the multiphase buck converter responsive to the load current or load voltage falling below the threshold, and wherein the threshold at which the pulse frequency modulation pulses are applied to the auxiliary phase is higher than the threshold at which the pulse frequency modulation pulses are applied to the single main phase of the multiphase buck converter.

28. The method according to claim 26, comprising maintaining a high-side switch and a low-side switch of the auxiliary phase in a high-impedance off-state after the load current or load voltage falls below the threshold until at least a current in an inductor coupled to the output of the auxiliary phase reaches zero before the high-side switch is turned on.

29. The method according to claim 20, further comprising determining whether the output of the auxiliary phase in the pulse frequency modulation mode violates a load criterion over a predefined interval, and if so, enabling one or more previously deactivated ones of the main phases of the multiphase converter.