Digital controller for a voltage regulator module

• US 7,456,618 B2
• Filed: 10/31/2005
• Issued: 11/25/2008
• Est. Priority Date: 10/31/2005
• Status: Active Grant

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: CHiL Semiconductor, Inc. (Infineon Technologies AG)
• Inventors: Jain, Praveen, Guo, Wennan
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US11/261,661
• Publication Number:
  US 20070096704A1
• Time in Patent Office: 1,121 Days
• Field of Search: 323/272, 323/282, 323/283, 323/284, 323/285, 323/351
• US Class Current: 323/272
• CPC Class Codes: H02M 3/1566 with means for compensating against rapid load changes, e.g. with auxiliary current source, with dual mode control or with inductance variation
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/1586 switched with a phase shift, i.e. interleaved
• CPC Class Codes: H02M 3/33515 with digital control

Abstract

A digital controller for a voltage regulator module (VRM) having single phase or multiphase power converters, and an optional dynamic conversion circuit, is disclosed. The digital controller improves the transient response of the VRM during harsh load current transients, and permits a substantial reduction in output capacitance of the VRM. When used with multiphase interleaved power converters, for a given load current requirement, the digital converter permits the number of interleaved phases of the VRM to be minimized. A VRM with the digital controller demonstrates low cost, high power density, high efficiency, and fast transient response.

Claims

1. A digital controller comprising:

a voltage sensor configured to sense an output voltage of a power supply and generate a corresponding digital signal representing the output voltage;

a detector configured to estimate a transient load current associated with a load based on rate of change of the output voltage, the transient load current representing a change in current required by the load during a transient condition;

a signal generator configured to generate an auxiliary switch control signal to activate an auxiliary switch to at least partially account for the transient load current when the estimate transient load current is greater than a threshold value;

wherein the digital controller is configured to control a main high side switch as well as the auxiliary switch to maintain the output voltage; and

wherein the digital controller produces a first control signal to control the main high side switch that, when activated, increases current supplied to the load.

2. The digital controller of claim 1, wherein the power supply is a DC-DC converter.

3. The digital controller of claim 1, wherein the power supply system is a buck converter.

4. The digital controller of claim 1, wherein the auxiliary switch control signal is a pulse train of higher frequency than a switching frequency of the main high side switch.

5. A method for controlling a voltage regulator module including a switching DC-DC converter, the method comprising:

sensing an output voltage of the DC-DC converter and generating a corresponding digital signal representing the output voltage;

maintaining an auxiliary high side switch in an OFF state during a steady state condition in which at least one main high side switch of the DC-DC converter produces an output current to drive a load;

based on the output voltage, determining a rate of change associated with the output current of the DC-DC converter; and

generating a control signal to activate the auxiliary high side switch during a transient load condition in which the rate of change associated with the output current is greater than a threshold value based on increased current consumption by the load.

6. The method of claim 5, wherein the DC-DC converter is of a non-isolated topology.

7. The method of claim 5, wherein the DC-DC converter is a buck converter.

8. The method of claim 5, further comprising pulse width modulating the control signal while the at least one main high side switch is maintained in a continuous ON state.

9. The method of claim 5, wherein each DC-DC converter is of an isolated circuit topology.

10. A method comprising:

maintaining an auxiliary high side switch of a power supply in an OFF state during a steady state condition in which at least one main high side switch in the power supply is switched to supply power to a load;

monitoring an output voltage of the power supply;

calculating a rate of change associated with the output voltage to detect a transient condition during which the load consumes additional current than when in the steady state condition; and

initiating activation of the auxiliary high side switch to an ON state to convey power from an input voltage source to the load to at least partially account for the transient condition.

11. The method as in claim 10, wherein calculating the rate of change associated with the output voltage includes producing a value representing a change in current consumed by the load during the transient condition.

12. The method as in claim 10 further comprising:

initiating activation of the at least one main high side switch by controlling multiple high side switches in respective phases of the power supply to maintain the output voltage at a substantially fixed value during the steady state condition.

13. The method as in claim 10 further comprising:

utilizing the rate of change associated with the output voltage to estimate a load current step representing an additional amount of current consumed by the load during the transient condition.

14. The method as in claim 13 further comprising:

comparing the estimated load current step to a threshold value; and

in response to detecting that the load current step is greater than the threshold value, initiating activation of the auxiliary high side switch to the ON state.

15. The method as in claim 10, wherein the at least one main high side switch includes multiple high side switches, the method further comprising:

during the steady state condition, operating the multiple high side switches of the power supply out of phase with respect to each other to maintain the output voltage; and

during the transient condition, initiating simultaneous activation of the multiple high side switches to an ON state when the auxiliary switch is activated to supply current to the load.

16. The method as in claim 10, wherein initiating activation of the auxiliary high side switch to the ON state includes:

activating the auxiliary high side switch for a respective time duration of time whose length is proportional to the rate of change associated with the output voltage.

17. The method as in claim 16, wherein initiating activation of the auxiliary high side switch to an ON state includes:

after the respective time duration;

deactivating the auxiliary high side switch; and

while the auxiliary high side switch is deactivated, repeatedly activating the at least one main high side switch in the power supply to maintain the output voltage within an acceptable voltage range.

18. The method as in claim 10, wherein the at least one main high side switch includes multiple high side switches, the method further comprising:

during the steady state condition, operating the multiple high side switches of the power supply out of phase with respect to each other to maintain the output voltage; and

during the transient condition, initiating simultaneous activation of the multiple high side switches to an ON state when the auxiliary switch is activated to supply current to the load.

19. The method as in claim 18, wherein initiating activation of the auxiliary high side switch during the transient condition includes:

pulsing the auxiliary switch ON and OFF while maintaining the multiple high side switches in a continuous ON state.

20. The method as in claim 18, wherein initiating activation of the auxiliary high side switch during the transient condition includes:

pulsing the auxiliary switch ON and OFF at a higher frequency than a rate of switching each of the multiple high side switches.

21. The method as in claim 10, wherein the auxiliary high side switch, when activated to an ON state, supplies a higher rate of current to power the load than do each of the at least one main high side switch when activated to an ON state.

22. A controller configured to:

maintain an auxiliary high side switch of a power supply in an OFF state during a steady state condition in which at least one main high side switch in the power supply is switched to supply power to a load;

monitor an output voltage of the power supply;

calculate a rate of change associated with the output voltage to detect a transient condition during which the load consumes additional current than when in the steady state condition; and

initiate activation of the auxiliary high side switch to an ON state to convey power from an input voltage source to the load to at least partially account for the transient condition.