Nonlinear digital control circuit and method for a DC/DC converter

• US 20070024252A1
• Filed: 07/18/2006
• Published: 02/01/2007
• Est. Priority Date: 07/19/2005
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Marino, Filippo, Minieri, Marco, Boscaino, Valeria, Di Blasi, Giuseppe
• Granted Patent: US 7,656,140 B2
• Time in Patent Office: Days
• US Class Current: 323/222
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A control circuit for a DC/DC converter has a linear-control loop, which receives a quantity to be controlled and a first reference quantity, and generates a modulation value. A nonlinear modulation unit is activated in presence of a variation of the quantity to be controlled higher than a preset intervention threshold and modifies in a nonlinear way the reference quantity supplied to the linear-control loop. In the case of large variation and of preset sign of the quantity to be controlled, the linear-control loop is deactivated, a signal for switching-off of the DC/DC converter is initially generated, and then a false steady-state-modulation value is supplied to the DC/DC converter.

Claims

1. A control circuit for a DC/DC converter, comprising

a linear-control loop, which has an input receiving a quantity to be controlled and a first reference quantity, and has an output supplying a modulation value, and

a nonlinear modulation unit for said first reference quantity, said nonlinear modulation unit being activated in presence of a first variation of said quantity to be controlled higher than an intervention threshold.

2. The control circuit according to claim 1, wherein said linear-control loop and said nonlinear modulation unit are of digital type.

3. The control circuit according to claim 1, wherein said linear-control loop comprises a voltage-adaptive positioning module, which receives said quantity to be controlled;

an error-amplification module, cascade-coupled to said adaptive positioning module and receiving said first reference quantity; and

a linear controller cascade-coupled to said error-amplification module.

4. The control circuit according to claim 1, wherein said nonlinear modulation unit receives said quantity to be controlled and said first reference quantity, and generates a modulated reference quantity according to said quantity to be controlled and according to said first reference quantity.

5. The control circuit according to claim 4, wherein said nonlinear modulation unit comprises a control module receiving said quantity to be controlled and generating a first enabling signal in presence of said first variation of said quantity to be controlled;

a subtractor element receiving said quantity to be controlled and a regulation value and generating a loop quantity;

a differential element receiving said loop quantity and said first reference quantity and generating said modulated reference quantity; and

a first selector, controlled by said first enabling signal, receiving said first reference quantity and said modulated reference quantity, and having an output connected to said linear-control loop.

6. The control circuit according to claim 5, wherein said regulation value is equal to the instantaneous value of said quantity to be controlled when said nonlinear modulation unit is activated.

7. The control circuit according to claim 4, wherein said control module deactivates said linear-control loop in presence of a second variation of said quantity to be controlled of a preset sign and greater than a second preset threshold, said second preset threshold being greater than said intervention threshold.

8. The control circuit according to claim 7, wherein said nonlinear modulation unit generates a modulation-modification quantity, supplied to an output of said control circuit and having initially a switching-off value for said DC/DC converter and subsequently a false steady-state-modulation value.

9. The control circuit according to claim 8, wherein said nonlinear modulation unit further comprises a second selector arranged between said linear-control loop and said output of said control circuit, said second selector being controlled by said control module for replacing said modulation value with said modulation-modification quantity in presence of said second variation of said quantity to be controlled.

10. A method for controlling a DC/DC converter receiving a modulation value and supplying a quantity to be controlled, comprising:

acquiring said quantity to be controlled and a first reference quantity;

regulating with a closed linear loop said quantity to be controlled on the basis of said first reference quantity; and

detecting a first variation of said quantity to be controlled higher than an intervention threshold, and

modulating, in a nonlinear way, said first reference quantity in presence of said first variation of said quantity to be controlled.

11. The method according to claim 10, wherein said modulating step comprises generating a modulated reference quantity according to said quantity to be controlled and according to said first reference quantity.

12. The method according to claim 10, wherein said step of generating a modulated reference quantity comprises:

generating a loop quantity proportional to a difference between said quantity to be controlled and a preset regulation value; and

generating said modulated reference quantity on the basis of a difference between said loop quantity and said first reference quantity.

13. The method according to claim 10, comprising:

deactivating said step of regulating with closed linear loop upon detection of a positive variation of said quantity to be controlled greater than a second preset threshold, said second preset threshold being greater than said preset intervention threshold; and

generating a modulation-modification quantity having initially a switching-off value for said DC/DC converter and subsequently a preset false steady-state-modulation value.