Delay compensation for hysteretic control

• US 20070103126A1
• Filed: 11/08/2005
• Published: 05/10/2007
• Est. Priority Date: 11/08/2005
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Johnson, Brian, McDonald, Brent
• Granted Patent: US 7,508,178 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: H02M 1/385 with means for correcting output voltage deviations introduced by the dead time
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence

Abstract

For controlling a direct current to direct current (DC-DC) converter, a controller individually switches a charge switch and a discharge switch to control a duty cycle, thereby providing a regulated DC output. A delay in switching each one of the charge and discharge switches results in a formation of a DC error in the regulated DC output. The controller adjusts the duty cycle by adding a delay compensation to substantially eliminate the DC error. The delay compensation substantially eliminates the DC error by decreasing an average value of the regulated DC output to offset an increase in the average value of the regulated DC output without the delay compensation.

Claims

1. A direct current to direct current (DC-DC) converter comprising:

a charge switch coupled in between a direct current (DC) voltage input and a switched DC output, wherein the charge switch is switchable to control a duty cycle of the DC voltage input;

a discharge switch coupled in between the switched DC output and a predefined voltage, wherein the discharge switch is switchable to control the duty cycle;

a filter to filter out at least one predefined frequency of the switched DC output and provide a regulated DC output; and

a controller to control the duty cycle, wherein a corresponding delay in switching each one of the charge and discharge switches results in a DC error in the regulated DC output, wherein the controller adjusts the duty cycle by adding a delay compensation to substantially eliminate the DC error.

2. The converter of claim 1, wherein the controller includes:

a first comparator providing a first output in response to the regulated DC output and a first input, the first input being indicative of a first hysteretic trip point;

a second comparator providing a second output in response to the regulated DC output and a second input, the second input being indicative of a second hysteretic trip point;

an adder providing a delayed second output in response to adding the delay compensation to the second output; and

a latch providing a control output to control the duty cycle in response to the first output and the delayed second output.

3. The converter of claim 2, wherein the first input is derived by adding a voltage reference source to the first hysteretic trip point.

4. The converter of claim 2, wherein the second input is derived by subtracting the second hysteretic trip point from a voltage reference source.

5. The converter of claim 2, wherein the charge switch is off and the discharge switch is on when the first output is high, wherein the first output is high when the regulated DC output is greater than the first input.

6. The converter of claim 2, wherein the charge switch is on and the discharge switch is off when the delayed second output is high, wherein the delayed second output is high when the regulated DC output is less than the second input.

7. The converter of claim 2, wherein the adder is bypassed and the second hysteretic trip point is adjusted to result in a duty cycle that is substantially equal to the duty cycle with the delay compensation.

8. The converter of claim 2, wherein the latch is a set-reset flip-flop.

9. The converter of claim 2, wherein the control output includes a charge control signal provided to the charge switch and a discharge control signal provided to the discharge switch, wherein the charge control signal and the discharge control signal respectively control an operating state of the charge switch and the discharge switch.

10. The converter of claim 1, wherein the delay compensation substantially eliminates the DC error by decreasing an average value of the regulated DC output to offset an increase in the average value of the regulated DC output without the delay compensation.

11. The converter of claim 1, wherein the delay compensation is computed as a function of a load current.

12. The converter of claim 1, wherein the regulated DC output is provided to a processor included in an information handling system (IHS).

13. A method for controlling a direct current to direct current (DC-DC) converter, the method comprising:

receiving a delay compensation as a predefined function of a time delay in switching a plurality of switches included in the DC-DC converter, wherein the time delay results in a DC error in a regulated output of the DC-DC converter; and

adjusting a duty cycle of the DC-DC converter by an addition of the delay compensation to substantially eliminate the DC error.

14. The method of claim 13, comprising:

adjusting a hysteretic trip point of the DC-DC converter to control the duty cycle, wherein the hysteretic trip point is adjusted as another predefined function of the delay compensation to substantially eliminate the DC error.

15. The method of claim 14, comprising:

bypassing the addition of the delay compensation.

16. The method of claim 13, wherein the delay compensation is stored in a memory.

17. The method of claim 13, wherein the predefined function is computed as a difference of slopes divided by a discharge current slope, wherein the difference of slopes is the discharge current slope subtracted from a charge current slope.

18. An information handling system (IHS) comprising:

a processor; and

a direct current to direct current (DC-DC) converter to provide a current to the processor, wherein the converter includes;

a charge switch coupled in between a direct current (DC) voltage input and a switched DC output, wherein the charge switch is switchable to control a duty cycle of the DC voltage input;

a discharge switch coupled in between the switched DC output and a predefined voltage, wherein the discharge switch is switchable to control the duty cycle;

a filter to filter out at least one predefined frequency of the switched DC output and provide a regulated DC output to the processor; and

a controller to control the duty cycle, wherein a corresponding delay in switching each one of the charge and discharge switches results in a DC error in the regulated DC output, wherein the controller adjusts the duty cycle by adding a delay compensation to substantially eliminate the DC error.

19. The system of claim 18, wherein the controller includes:

a first comparator providing a first output in response to the regulated DC output and a first input, the first input being indicative of a first hysteretic trip point;

a second comparator providing a second output in response to the regulated DC output and a second input, the second input being indicative of a second hysteretic trip point;

an adder providing a delayed second output in response to adding the delay compensation to the second output; and

a latch providing a control output to control the duty cycle in response to the first output and the delayed second output.

20. The system of claim 19, wherein the adder is bypassed and the second hysteretic trip point is adjusted to result in a duty cycle that is substantially equal to the duty cycle with the delay compensation.