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

• US 20060001408A1
• Filed: 07/02/2004
• Published: 01/05/2006
• 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
• Granted Patent: US 7,262,628 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• 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. A multiphase power regulator comprising:

a multiphase pulse width modulator;

a pulse output stage comprising a high side FET, a low side FET and an inductor coupled to the multiphase pulse width modulator;

a sense amplifier coupled to the pulse output stage for sensing the current; and

an analog to digital converter coupled to the sense amplifierr for converting the sensed current into digital form.

2. A multiphase power regulator as in claim 1, further comprising a calibration current source coupled to the inductor.

3. A multiphase power regulator as in claim 1, further comprising:

a current mirror coupled to the high side FET, the sense amplifier being coupled to the current mirror.

4. A multiphase power regulator as in claim 3, wherein the current mirror further comprises:

a sensing resistor, the sense amplifier being coupled to the sensing resistor.

5. A multiphase power regulator as in claim 1, further comprising:

a series connected resistor and capacitor connected in parallel with said inductor, said sense amplifier being coupled to the junction between said resistor and capacitor.

6. A multiphase power regulator as in claim 1, further comprising:

a calibration current source coupled to one side of said inductor;

the other side of the inductor being coupled to a common node formed by said high side FET and said low side FET; and

a sense amplifier coupled to said common node.

7. A multiphase power regulator as in claim 6, wherein said calibration current source comprises:

a reference voltage source;

an operational amplifier having an input coupled to the reference voltage source;

an input electrode of an FET coupled to the output of the operational amplifier; and

an output electrode of said FET being coupled to a second input of said operational amplifier.

8. A multiphase power regulator as in claim 1, further comprising:

a temperature sensor positioned adjacent said pulse output stage.

9. A multiphase power regulator as in claim 1, further comprising:

a temperature sensor positioned adjacent said low side FET.

10. A digital multiphase power regulator comprising:

a digital controller;

a first high side field effect transistor and a first low side field effect transistor connected at a common point therebetween, forming a series connection between a first and second potential source;

a first node at said common point between said first high side field effect transistor and said first low side field effect transistor connected to one end of a first inductor, the other end of said first inductor coupled to a common connection of a capacitor and a load;

a second high side field effect transistor and a second low side field effect transistor connected at a common point therebetween, forming a series connection between said first and second potential source;

a second node at said common point between said second high side field effect transistor and said second low side field effect transistor connected to one end of a second inductor, the other end of said second inductor connected to said common connection of said capacitor and load; and

a switchable current source coupled between said common connection and said second potential source.

11. A digital multiphase power regulator as in claim 10, wherein said switchable current source comprises:

a reference voltage source;

an operational amplifier having an input coupled to the reference voltage source;

an input electrode of an FET coupled to the output of the operational amplifier; and

an output electrode of said FET being coupled to a second input of said operational amplifier.

12. 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 current source in a first state;

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

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

13. A method as in claim 12 further comprising:

sensing the temperature of the low side field effect transistor.

14. A method as in claim 13, wherein the sensed temperature is converted to a digital value.

15. A method as in claim 14, wherein the digital value is used to provide non-linear compensation comprising the steps of:

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

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

16. A method as in claim 14, 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.

17. 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;

18. A method as in claim 17, wherein the steps of obtaining said first and second voltage measurement are taken at said inductor.

19. A method as in claim 18, wherein the comparison of the first and second voltage measurements provides the DC resistance of the inductor.

20. A method as in claim 17, wherein the steps of obtaining said first and second voltage measurement are taken at said high side field effect transistor.

21. A method as in claim 20, wherein the comparison of the first and second voltage measurements provides the current mirror effective resistance.

22. A method as in claim 17, wherein the steps of obtaining said first and second voltage measurement are taken at said low side field effect transistor.

23. A method as in claim 22, wherein the comparison of the first and second voltage measurements provides the on resistance of the low side field effect transistor.

24. 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.