Digital output voltage regulation circuit having first control loop for high speed and second control loop for high accuracy

• US 7,141,956 B2
• Filed: 03/18/2005
• Issued: 11/28/2006
• Est. Priority Date: 03/18/2005
• Status: Active Grant

• Current Assignee: Bel Power Solutions Inc.
• Original Assignee: Power-One Incorporated (ABB Limited)
• Inventors: Chapuis, Alain
• Primary Examiner(s): Easthom, Karl
• Assistant Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US11/084,766
• Publication Number:
  US 20060208716A1
• Time in Patent Office: 620 Days
• Field of Search: 323/283, 323/282, 323/288, 341/110, 341/114, 341/155
• US Class Current: 323/283
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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 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 error signal representing a difference between a first output measurement of said voltage regulator and a reference value, a first digital filter providing a digital control output based on said first digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output; and

a second digital control loop including a second analog-to-digital converter providing a second output measurement of said voltage regulator, said second digital control loop providing a second digital error signal representing a difference between said second output measurement and said reference value, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital error signal being applied to said first digital control loop to improve accuracy of said first output measurement and thereby improve regulation of said voltage regulator.

2. The voltage regulator of claim 1, further comprising a serial interface operatively coupled to said first and second digital control loops and adapted to receive reference data defining said reference value.

3. The voltage regulator of claim 2, wherein said serial interface is further adapted to send monitor data corresponding to said second output measurement.

4. The voltage regulator of claim 2, wherein said serial interface is further adapted to receive coefficient data and provide said coefficient data to said first digital filter, said coefficient data defining filter characteristics of said first digital filter.

5. The voltage regulator of claim 2, further comprising a digital-to-analog converter operatively coupled to said serial interface, said digital-to-analog converter converting said reference data to said reference value.

6. The voltage regulator of claim 1, wherein said first digital control loop further comprises a subtractor providing an analog error signal representing said difference between said first output measurement and said reference value, said analog error signal being provided to said first analog-to-digital converter.

7. The voltage regulator of claim 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 error signal representing a difference between a first output measurement of said voltage regulator and a reference value, a first digital filter providing a digital control output based on said first digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output; and

a second digital control loop including a second analog-to-digital converter providing a second output measurement of said voltage regulator, said second digital control loop providing a second digital error signal representing a difference between said second output measurement and said reference value, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital error signal being applied to said first digital control loop to improve accuracy of said first output measurement and thereby improve regulation of said voltage regulator;

wherein said second digital control loop further comprises a digital comparator receiving said second output measurement and said reference value and providing said second digital error signal.

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

9. The voltage regulator of claim 8, wherein said second digital control loop further comprises a variable resistor operatively coupled to said output terminals and responsive to said counter to adjust said first output measurement.

10. 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 error signal representing a difference between a first output measurement of said voltage regulator and a reference value, a first digital filter providing a digital control output based on said first digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output; and

a second digital control loop including a second analog-to-digital converter providing a second output measurement of said voltage regulator, said second digital control loop providing a second digital error signal representing a difference between said second output measurement and said reference value, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital error signal being applied to said first digital control loop to improve accuracy of said first output measurement and thereby improve regulation of said voltage regulator;

wherein said second digital control loop further comprises a variable resistor operatively coupled to said output terminals and responsive to said second digital error signal to adjust said first output measurement.

11. 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 error signal representing a difference between a first output measurement of said voltage regulator and a reference value, a first digital filter providing a digital control output based on said first digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output; and

a second digital control loop including a second analog-to-digital converter providing a second output measurement of said voltage regulator, said second digital control loop providing a second digital error signal representing a difference between said second output measurement and said reference value, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital error signal being applied to said first digital control loop to improve accuracy of said first output measurement and thereby improve regulation of said voltage regulator;

wherein said second digital control loop adjusts said reference value using said second digital error signal.

12. The voltage regulator of claim 11, wherein said second digital control loop further comprises a phase accumulator that provides dithering of said reference value.

13. 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 error signal representing a difference between a first output measurement of said voltage regulator and a reference value, a first digital filter providing a digital control output based on said first digital error signal, and a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output; and

a second digital control loop including a second analog-to-digital converter providing a second output measurement of said voltage regulator, said second digital control loop providing a second digital error signal representing a difference between said second output measurement and said reference value, said second analog-to-digital converter having greater resolution than said first analog-to-digital converter, said second digital error signal being applied to said first digital control loop to improve accuracy of said first output measurement and thereby improve regulation of said voltage regulator;

wherein said first analog-to-digital converter is clocked at a substantially higher rate than said second analog-to-digital converter.

14. 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;

filtering said first digital error signal to provide a digital control output;

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

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

adjusting said first output measurement using said second digital error signal;

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

15. The method of claim 14, further comprising receiving reference data defining said reference value.

16. The method of claim 14, further comprising sending monitor data corresponding to said second output measurement.

17. The method of claim 14, further comprising receiving coefficient data and using said coefficient data in performing said filtering step.

18. The method of claim 15, further comprising converting said reference data to said reference value.

19. The method of claim 14, further comprising providing an analog error signal representing said difference between said first output measurement and said reference value.

20. The method of claim 14, further comprising adjusting said reference value using said second digital error signal.

21. The method of claim 14, further comprising dithering said reference value.