Digital calibration with lossless current sensing in a multiphase switched power converter

• US 7,262,628 B2
• Filed: 07/02/2004
• Issued: 08/28/2007
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Primarion Incorporated (Infineon Technologies AG)
• Inventors: Carroll, Robert T., Tang, Benjamim, Schulte, Steven Joseph, Southwell, Scott Wilson
• Primary Examiner(s): Easthom; Karl
• Assistant Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US10/884,840
• Publication Number:
  US 20060001408A1
• Time in Patent Office: 1,152 Days
• Field of Search: 323/283, 323/272, 324/769, 324/759, 324/601, 324/713, 324/130, 702/107, 702/65
• US Class Current: 323/266
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

Disclosed is a multi-phase power regulator that accurately senses current at a load in a lossless manner and adjusts the power supplied to the load based on the sensed current. Also disclosed is a method of calibrating a multiphase voltage regulator by applying a known calibration current at the load and determining actual current values by the difference in measured values between when the known calibration current is applied and when it is not applied. The accurate current is determined at a known temperature and accurate temperature compensation is provided by a non-linear digital technique. Each phase of the multi-phase power regulator is individually calibrated so that balanced channels provide accurate power to the load. Also disclosed is a calibration method with minimal noise generation.

Claims

1. In a closed loop system, a method of calibrating a digital multiphase voltage regulator having a discrete output at each output phase for providing regulated power to a load, comprising the steps of:

providing a low side field effect transistor and a high side field effect transistor connected in series and having a common node at each output phase;

coupling an inductor between each output phase and the load;

placing the load in a quiescent state such that it draws only leakage current;

coupling a calibration current source to the load;

obtaining a first voltage measurement by measuring the voltage across the low side field effect transistor with the calibration current source in a first state;

storing the first voltage measurement;

obtaining a second voltage measurement by measuring the voltage across the low side field effect transistor with the calibration current source in a second state;

storing the second voltage measurement; and

determining an on resistance of the low side field effect transistor by comparing the first and second voltages.

2. A method as in claim 1 further comprising:

measuring a temperature of the low side field effect transistor.

3. A method as in claim 2, wherein the measured temperature is converted to a digital value.

4. A method as in claim 3, wherein the digital value is used to provide non-linear compensation comprising the steps of:

utilizing most significant bits to define a plurality of approximately linear portions of the change in element resistance as a function of temperature;

utilizing less significant bits to define the change in element resistance as a function of temperature within each of the plurality of approximately linear portions.

5. A method as in claim 3, wherein the digital value is used to provide non-linear compensation comprising the step of:

accessing a look up table to identify the actual element resistance at the measured temperature.

6. A method of calibrating a digital multiphase voltage regulator having a discrete output at each output phase for providing regulated power to a load, comprising the steps of:

providing a low side field effect transistor and a high side field effect transistor connected in series and having a common node, at each output phase;

coupling an inductor between each output phase and the load;

placing the load in a quiescent state such that it draws only leakage current;

coupling a calibration current source to the load;

obtaining a first voltage measurement at each phase with the current source in a first state;

storing the voltage obtained by said first voltage measurement;

obtaining a second voltage measurement at each phase by measuring the voltage with the current source in a second state; and

storing the voltage obtained by said second voltage measurement.

7. A method as in claim 6, wherein the steps of obtaining said first and second voltage measurement are taken at said inductor.

8. A method as in claim 7, wherein the comparison of the first and second voltage measurements provides a DC resistance of the inductor.

9. A method as in claim 6, wherein the steps of obtaining said first and second voltage measurement are taken at said high side field effect transistor with a current mirror comprising a precision resistor.

10. A method as in claim 9, wherein the comparison of the first and second voltage measurements provides the current mirror effective resistance.

11. A method as in claim 6, wherein the steps of obtaining said first and second voltage measurement are taken at said low side field effect transistor.

12. A method as in claim 11, wherein the comparison of the first and second voltage measurements provides the on resistance of the low side field effect transistor.

13. A method of calibrating a multi-phase voltage regulator with a calibration current source comprising the steps of:

setting the calibration current source in a first state;

turning on all the phases of the multi-phase voltage regulator;

turning off one phase at a time until only one phase is on and measuring the current at that one phase;

turning on a second phase in addition to said only one phase;

turning off said only one phase and measuring the current at said second phase;

repeating the last two mentioned steps for successive phases until the current has been measured in all the phases with the calibration current set in said first state;

setting the calibration current source into a second state;

measuring the current in the last measured phase again;

turning on another phase;

turning off the last measured phase;

measuring the current in said another phase; and

repeating the last two steps until the current has been measured in all the phases with the calibration current turned in said second state.