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

• US 7,960,951 B2
• Filed: 07/18/2007
• Issued: 06/14/2011
• 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: Schulte, Steven Joseph, Southwell, Scott Wilson, Carroll, Robert T., Tang, Benjamim
• Primary Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US11/779,487
• Publication Number:
  US 20070257650A1
• Time in Patent Office: 1,427 Days
• Field of Search: 323/283, 323/272, 323/220, 324/769, 324/759, 324/601, 324/713, 324/130, 702/107, 702/65
• US Class Current: 323/272
• 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 current;

an analog to digital converter coupled to the sense amplifier for converting the sensed current into digital form;

a calibration current source coupled to the inductor and adapted to generate a precise calibration current;

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

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

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

a temperature sensor positioned adjacent said pulse output stage.

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

a temperature sensor positioned adjacent said low side FET.

4. In a closed loop system, a digital multiphase power regulator adapted to operate in a normal operating state or calibration state, comprising:

a digital controller;

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

a first node at said first 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 second common point therebetween, forming a series connection between said first and second potential source;

a second node, at said second 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;

a first sense amplifier coupled to the first common point;

a second sense amplifier coupled to the second common point; and

a switchable current source coupled between said common connection and said second potential source, wherein said switchable current source is adapted to;

apply a precise calibration current through said common connection of said capacitor and load during at least a portion of the calibration state; and

be disabled during the normal operating state.

5. A digital multiphase power regulator as in claim 4, 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.

6. In a closed loop system as in claim 4, a digital multiphase power regulator 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.

7. In a closed loop system as in claim 4, a digital multiphase power regulator 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.

8. In a closed loop system as in claim 4, a digital multiphase power regulator further comprising:

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.

9. In a closed loop system as in claim 4, a digital multiphase power regulator further comprising:

a temperature sensor positioned adjacent said pulse output stage and having an output coupled to a multiplexer; and

said first and second sense amplifiers each having an output coupled to said multiplexer.

10. In a closed loop system as in claim 4, a digital multiphase power regulator further comprising:

a storage for receiving and storing an output from said first sense amplifier and said second sense amplifier during a first measurement;

said storage also receiving and storing an output from said first and second sense amplifiers during a second measurement; and

a compare circuit coupled to an output of said storage for subtracting the stored output from one of said first and second measurements from the other of said first and second measurements.

11. In a closed loop system as in claim 4, a digital multiphase power regulator further comprising:

first and second current mirrors each coupled to a corresponding one of the first and second high side field effect transistors,

first and second sensing resistors each coupled to a corresponding one of the current mirrors; and

each of said first and second sense amplifiers being coupled to a corresponding one of said first and second sensing resistors.