Digital peak current mode control for switch-mode power converters

• US 8,773,097 B2
• Filed: 01/06/2011
• Issued: 07/08/2014
• Est. Priority Date: 01/06/2011
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Franklin, Chris Michael, McDonald, Brent Alan, Vogt, John Christian
• Primary Examiner(s): Laxton, Gary L
• Application Number:
  US12/985,693
• Publication Number:
  US 20120176824A1
• Time in Patent Office: 1,279 Days
• Field of Search: 323/282, 323/283, 323/284, 323/285
• US Class Current: 323/283
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A digital control circuit is provided for use with a switch-mode power converter that receives an input signal at a first input node and a control signal at a second input node, and that provides an output signal at a first output node and a current signal at a second output node. The digital control circuit generates a programmable current reference signal based on a difference between the output signal and a voltage reference signal, calculates a time instant when the current signal substantially equals the programmable reference current signal, and generates the control signal based on the calculated time instant.

Claims

1. A digital control circuit for use with a switch-mode power converter that receives an input signal at a first input node and a control signal at a second input node, and that provides an output signal at a first output node and a current signal at a second output node, the digital control circuit comprising:

the first input node coupled to receive the output signal at the first output node of the switch-mode power converter;

the second input node coupled to receive the current signal at the second output node of the switch-mode power converter; and

an output node coupled to provide the control signal at the second input node of the switch-mode power converter,

wherein the digital control circuit;

(a) generates a programmable current reference signal based on a difference between the output signal and a voltage reference signal;

(b) mathematically predicts, utilizing a prediction algorithm, a time instant in the future when the peak current signal substantially equals the programmable reference current signal; and

(c) generates the control signal based on the mathematically computed time instant.

2. The digital control circuit of claim 1, wherein the digital control circuit:

generates a current reference signal based on a difference between the output signal and the voltage reference signal; and

generates the programmable current reference signal based on the current reference signal and a programmable slope compensation signal.

3. The digital control circuit of claim 2, wherein the programmable slope compensation signal comprises a ramp signal having a programmable slope.

4. The digital control circuit of claim 1, wherein the digital control circuit generates a current error signal based on a difference between the current signal and the programmable current reference signal, and calculates the time instant based on the current error signal.

5. The digital control circuit of claim 1, wherein the digital control circuit adjusts a duty cycle of the control signal based on the calculated time instant.

6. The digital control circuit of claim 1, wherein the digital control circuit adjusts a phase of the control signal based on the calculated time instant.

7. The digital control circuit of claim 1, wherein the digital control circuit generates the control signal so that the current signal has a peak value based on the programmable current reference signal.

8. A digital control circuit for use with a switch-mode power converter for receiving an input voltage signal at a first input node and a control signal at a second input node, and that provides an output voltage signal at a first output node and an inductor current signal at a second output node, the digital control circuit comprising:

a voltage control loop comprising an input node couplable to receive the output voltage signal at the first output node of switch-mode power converter, wherein the voltage control loop provides a current reference signal at an output node based on a difference between the output voltage signal and a reference voltage signal; and

a current control loop comprising the first input node couplable to receive the current reference signal at the output node of the voltage control loop, the second input node couplable to receive the inductor current signal at the first output node of switch-mode power converter, and a second output node couplable to provide a control signal at a second input node of the switch-mode power converter,

wherein the current control loop;

(a) generates a programmable current reference signal based on the current reference signal;

(b) determines a current error signal based on a difference between the programmable current reference signal and the inductor sense current;

(c) mathematically computes a time instant when the peak inductor current signal substantially equals the programmable current reference signal based on the current error signal; and

(d) generates the control signal based on the mathematically computed time instant.

9. The digital control circuit of claim 8, wherein the current control loop generates the programmable current reference signal based on the current reference signal and a programmable slope compensation signal.

10. The digital control circuit of claim 9, wherein the programmable slope compensation signal comprises a ramp signal having a programmable slope.

11. The digital control circuit of claim 8, wherein the current error signal comprises a sampled data signal based on samples of the difference between the programmable current reference signal and the inductor sense current.

12. The digital control circuit of claim 8, wherein the control signal comprises a clock cycle, and the current control loop calculates the time instant once per clock cycle.

13. The digital control circuit of claim 8, wherein the current control loop generates the control signal so that the inductor current signal has a peak value based on the programmable current reference signal.

14. The digital control circuit of claim 8, wherein the current control loop adjusts a duty cycle of the control signal based on the calculated time instant.

22. The digital control circuit of claim 8 wherein the time instant when the current signal substantially equals the programmable reference current signal is mathematically computed by:

15. A method for providing peak current mode control for a switch-mode power converter that receives an input signal and a control signal, and that provides an output signal and a current signal, the method comprising:

using a digital controller to;

(a) generate a programmable current reference signal based on a difference between the output signal and a voltage reference signal;

(b) mathematically predicting, utilizing a prediction algorithm, a time instant in the future when a peak value of the current signal substantially equals the programmable reference current signal; and

(c) generate the control signal based on the mathematically computed time instant.

16. The method of claim 15, further comprising using the digital controller to:

generate a current reference signal based on a difference between the output signal and the voltage reference signal; and

generates the programmable current reference signal based on the current reference signal and a programmable slope compensation signal.

17. The method of claim 16, wherein the programmable slope compensation signal comprises a ramp signal having a programmable slope.

18. The method of claim 15, further comprising using the digital controller to:

generate a current error signal based on a difference between the current signal and the programmable current reference signal; and

calculate the time instant based on the current error signal.

19. The method of claim 15, further comprising using the digital controller to adjust a duty cycle of the control signal based on the calculated time instant.

20. The method of claim 15, further comprising using the digital controller to generate the control signal so that the current signal has a peak value based on the programmable current reference signal.

21. A digital control circuit for use with a switch-mode power converter that receives an input signal at a first input node and a control signal at a second input node, and that provides an output signal at a first output node and a current signal at a second output node, the digital control circuit comprising:

the first input node coupled to receive the output signal at the first output node of the switch-mode power converter;

the second input node coupled to receive the current signal at the second output node of the switch-mode power converter; and

an output node coupled to provide the control signal at the second input node of the switch-mode power converter,

wherein the digital control circuit;

(a) generates a programmable current reference signal based on a difference between the output signal and a voltage reference signal;

(b) mathematically computes utilizing a prediction algorithm a time instant when the peak current signal substantially equals the programmable reference current signal; and

(c) generates the control signal based on the mathematically computed time instant,

wherein the time instant when the current signal substantially equals the programmable reference current signal is mathematically computed by;

23. A method for providing peak current mode control for a switch-mode power converter that receives an input signal and a control signal, and that provides an output signal and a current signal, the method comprising:

using a digital controller to;

(a) generate a programmable current reference signal based on a difference between the output signal and a voltage reference signal;

(b) mathematically compute utilizing a prediction algorithm a time instant when a peak value of the current signal substantially equals the programmable reference current signal; and

(c) generate the control signal based on the mathematically computed time instant,

wherein the time instant when the current signal substantially equals the programmable reference current signal is mathematically computed by;