Digital double-loop output voltage regulation

• US 7,554,310 B2
• Filed: 02/06/2007
• Issued: 06/30/2009
• Est. Priority Date: 03/18/2005
• Status: Active Grant

• Current Assignee: Power-One Incorporated (ABB Limited)
• Original Assignee: Power-One Incorporated (ABB Limited)
• Inventors: Chapuis, Alain, Roark, Dennis R.
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): Behm; Harry
• Application Number:
  US11/671,889
• Publication Number:
  US 20070182391A1
• Time in Patent Office: 875 Days
• Field of Search: 323/283, 323/282, 323/288, 341/110, 341/114, 341/155, 341/156, 341/142, 341/164, 702/64, 702/189
• US Class Current: 323/282
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A switched mode voltage regulator has a digital control system that includes dual digital control loops. The voltage regulator comprises at least one power switch adapted to convey power between respective input and output terminals of the voltage regulator and a digital controller adapted to control operation of the power switches responsive to an output of the voltage regulator. The digital controller further comprises dual digital control loops in which a first control loop provides high speed with lower regulation accuracy and a second control loop has high accuracy with lower speed. Thus, the digital control system provides the advantages of both high speed and high regulation accuracy.

Claims

1. A voltage regulator comprising:

at least one power switch adapted to convey power between respective input and output terminals of said voltage regulator; and

a digital controller adapted to control operation of said at least one power switch responsive to an output of said voltage regulator, said digital controller comprising;

a first digital control loop including a first analog-to-digital converter providing a first digital measurement of said voltage regulator output, a digital filter providing a digital control output based on a first digital error signal and a second digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch based on said digital control output, the first digital error signal comprising a difference between the first digital measurement and a digital reference value, the second digital error signal comprising a sum of the first digital error signal and a time varying portion of the digital reference value; and

a second digital control loop including a second analog-to-digital converter providing a second digital measurement of said voltage regulator output, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital control loop providing the digital reference value based on a desired output voltage setpoint, said second digital control loop providing said time varying portion of the digital reference value based on a difference between said second digital measurement and said output voltage setpoint.

2. The voltage regulator of claim 1, further comprising a serial interface operatively coupled to said second digital control loop and adapted to receive said output voltage setpoint.

3. The voltage regulator of claim 2, wherein said serial interface is further adapted to transmit said second digital measurement to a host.

4. The voltage regulator of claim 1, wherein said digital filter comprises proportional, integral and derivative arithmetic units.

5. The voltage regulator of claim 4, wherein said first digital error signal is provided to said proportional and derivative arithmetic units.

6. The voltage regulator of claim 4, wherein said second digital error signal is provided to said integral arithmetic unit.

7. The voltage regulator of claim 1, wherein said second digital control loop further comprises a digital comparator receiving said second digital measurement and said output voltage setpoint, and a counter operatively coupled to said digital comparator, said counter counting in a first direction if said second digital measurement is less than said output voltage setpoint and counting in an opposite direction if said second digital measurement is more than said output voltage setpoint.

8. The voltage regulator of claim 7, wherein said second digital control loop further comprises a phase accumulator operatively coupled to the counter that provides said time varying portion of the digital reference value.

9. The voltage regulator of claim 1, wherein said second digital control loop adjusts said digital reference value relatively slowly in correspondence with said second digital measurement.

10. The voltage regulator of claim 1, wherein said first analog-to-digital converter has a sampling rate substantially higher rate than a corresponding sampling rate of said second analog-to-digital converter.

11. A method of controlling a voltage regulator comprising at least one power switch adapted to convey power between input and output terminals of said voltage regulator, said method comprising:

receiving first and second output measurements of said voltage regulator;

sampling said first output measurement to provide a first digital error signal representing a difference between said output measurement and a reference value;

sampling said second output measurement to provide a time varying portion of a difference between said second output measurement and a reference value;

combining the time varying portion with the first digital error signal to provide a second digital error signal;

filtering said first and second digital error signals to provide a digital control output; and

providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output;

wherein, said first sampling step is performed at substantially higher speed and lower resolution than said second sampling step.

12. The method of claim 11, further comprising receiving reference data defining said reference value.

13. The method of claim 11, further comprising sending monitor data corresponding to said second output measurement.

14. The method of claim 11, wherein said filtering step further comprises derivative and proportional filtering the first digital error signal and integral filtering the second digital error signal.

15. The method of claim 11, further comprising adjusting said reference value using said second output measurement.

16. The method of claim 11, wherein the time varying portion further comprises at least one least significant bit of the difference between said second output measurement and a reference value.

17. A digital controller for a voltage regulator having at least one power switch adapted to convey power between respective input and output terminals of said voltage regulator, said digital controller being adapted to control operation of said at least one power switch responsive to an output of said voltage regulator, said digital controller comprising:

a first digital control loop including a first analog-to-digital converter providing a first digital measurement of said voltage regulator output, a digital filter providing a digital control output based on a first digital error signal and a second digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch based on said digital control output, the first digital error signal comprising a difference between the first digital measurement and a digital reference value, the second digital error signal comprising a sum of the first digital error signal and a time varying portion of the digital reference value; and

a second digital control loop including a second analog-to-digital converter providing a second digital measurement of said voltage regulator output, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital control loop providing the digital reference value based on a desired output voltage setpoint, said second digital control loop providing said time varying portion of the digital reference value based on a difference between said second digital measurement and said output voltage setpoint.

18. The digital controller of claim 17, further comprising a serial interface operatively coupled to said second digital control loop and adapted to receive said output voltage setpoint.

19. The digital controller of claim 18, wherein said serial interface is further adapted to transmit said second digital measurement to a host.

20. The digital controller of claim 17, wherein said digital filter comprises proportional, integral and derivative arithmetic units.

21. The digital controller of claim 20, wherein said first digital error signal is provided to said proportional and derivative arithmetic units.

22. The digital controller of claim 20, wherein said second digital error signal is provided to said integral arithmetic unit.

23. The digital controller of claim 17, wherein said second digital control loop further comprises a digital comparator receiving said second digital measurement and said output voltage setpoint, and a counter operatively coupled to said digital comparator, said counter counting in a first direction if said second digital measurement is less than said output voltage setpoint and counting in an opposite direction if said second digital measurement is more than said output voltage setpoint.

24. The digital controller of claim 23, wherein said second digital control loop further comprises a phase accumulator operatively coupled to the counter that provides said time varying portion of the digital reference value.

25. The digital controller of claim 17, wherein said second digital control loop adjusts said digital reference value relatively slowly in correspondence with said second digital measurement.

26. The digital controller of claim 17, wherein said first analog-to-digital converter has a sampling rate substantially higher rate than a corresponding sampling rate of said second analog-to-digital converter.