Current sensing and current sharing

• US 6,414,469 B1
• Filed: 12/13/2000
• Issued: 07/02/2002
• Est. Priority Date: 12/03/1998
• Status: Expired due to Fees

• Current Assignee: Virginia Tech Intellectual Properties, Inc.
• Original Assignee: Virginia Tech Intellectual Properties, Inc.
• Inventors: Lee, Fred C., Zhou, Xunwei
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/734,697
• Publication Number:
  US 20020036486A1
• Time in Patent Office: 566 Days
• Field of Search: 323/272, 323/271, 323/280, 323/282, 323/284, 323/285, 323/268
• US Class Current: 323/272
• CPC Class Codes: G05F 1/62 using bucking or boosting dc sources

Abstract

An interleaved small-inductance buck voltage regulator (VRM) converter with the novel current sensing and sharing technology significantly improves transient response with size minimization. Specifically, two or more buck VRM modules are interleaved or connected in parallel. The resultant current waveform has a fast transient response but with reduced ripples since the ripples in the individual modules mathematically cancel one another. The result is a smooth output current waveform having spikes within an acceptable tolerance limits when for example the load increases due to a connected processor changing from “sleep” to “active” mode. A novel current sensing and sharing scheme between the individual VRMs is implemented using an RC network in each module to detect inductor current for that module. Good current sharing result can be easily achieved. Unlike peak current mode control and average current mode control, with this technology, the converter still has low output impedance and fast transient response. As a result, the VRM can be very cost-effective, high power density, high efficiency and have good transient performance.

Claims

1. In a dc-dc voltage converter comprising n interleaved dc-dc converters, where n is an integer greater than or equal to 2, connected in parallel between a dc voltage source terminal and a load terminal, said dc-dc converters each comprising an inductor for delivering a current to said load terminal;

a controller for controlling a switching network for connecting and disconnecting said inductor to one of said voltage source terminal and ground; and

an output capacitor connected in parallel with said load terminal for supplying an output voltage signal, said controller comprising;

a first integrator circuit connected to said output capacitor for generating an integrated output voltage signal;

n second integrator circuits, each having an inverting input connected to said inductor of each of said n dc-dc converters, and a non-inverting input connected to receive said integrated output voltage signal; and

n-comparators for outputting a duty cycle signal for said switching networks in each of said n dc-dc converters, each of said n-comparators for comparing an output signal from one of said n-second integrator circuits to a triangle wave; and

a resistive capacitive (RC) network connected between said inductor and ground, and wherein said inverting input of each of said n second integrator circuits is connected to said inductor through said RC network.

2. A switchmode power converter, comprising

a plurality of switching stages, each switching stage including a series coupled pair of MOS-gated switching elements including a high side switch and a low side switch coupled together at a common node, each switching stage being connectable from a voltage source to a ground potential;

a plurality of inductors coupled, at respective first ends, to the respective common nodes of the switching stages;

a shunt capacitor coupled from second ends of the plurality of inductors to the ground potential; and

a controller connected between said shunt capacitor and said switching stages, said controller comprising;

a first comparator for comparing an output voltage across said shunt capacitor to a first reference voltage; and

a second comparator for comparing said output voltage to a second reference voltage,

wherein if said output voltage falls below said first reference voltage, said controller turns on said high side switches and turns off said low side switches; and

if said output voltage rises above said second reference voltage, said controller turns off said high side switches and turns on said low side switches.

3. The switchmode power converter of claim 2, wherein each series coupled pair of MOS-gated switching elements includes:

at least one series MOS-gated switching element coupled in series with the respective inductor; and

at least one MOS-gated switching element coupling the respective inductor to the ground potential.

4. The switchmode power converter of claim 3, wherein the control circuit provides the gate signals to the MOS-gated switching elements such that the at least one series MOS-gated switching element of each switching stage turns on and off at substantially different instants from one another.

5. The switchmode power converter of claim 3, wherein the control circuit provides the gate signals to the MOS-gated switching elements such that the at least one shunt MOS-gated switching element of each switching stage turns on and off at substantially different instants from one another.

6. The switchmode power converter of claim 3, wherein the control circuit provides the gate signals to the MOS-gated switching elements such that the at least one series MOS-gated switching element of each switching stage turns on and off at substantially the same instant.

7. The switchmode power converter of claim 2, wherein the MOS-gated switching elements are MOSFETs.

8. The switchmode power converter of claim 2, wherein the voltage source is a DC voltage source.

9. An interleaved dc-dc voltage converter for a voltage regulator module (VRM), comprising:

at least two dc-dc converters connected in parallel between a dc voltage source terminal and a load terminal, said dc-dc converters each comprising;

an inductor for delivering a current to said load terminal; and

a switching network having a high side switch for connecting sa id inductor to said voltage source terminal and a low said switch for connecting said inductor to ground;

an output capacitor connected in parallel with said load terminal;

a controller connected between said output capacitor and said switching networks, said controller comprising;

a first comparator for comparing an output voltage across said output capacitor to a first reference voltage; and

a second comparator for comparing said output voltage to a second reference voltage,

wherein if said output voltage falls below said first reference voltage, said controller turns on said high side switches and turns off said low side switches; and

if said output voltage rises above said second reference voltage, said controller turns off said high side switches and turns on said low side switches.

10. An interleaved dc-dc voltage converter for a voltage regulator module (VRM), as recited in claim 9 wherein said at least two dc-dc converters comprise buck converters.

11. An interleaved dc-dc voltage converter for a voltage regulator module (VRM), as recited in claim 9 further comprising a low pass filter connected between said output capacitor and said first comparator and said second comparator.

12. An interleaved dc-dc voltage converter for a voltage regulator module (VRM), comprising:

n dc-dc converters, where n is an integer greater than or equal to 2, connected in parallel between a dc voltage source terminal and a load terminal, said dc-dc converters each comprising;

an inductor for delivering a current to said load terminal; and

a switching network for connecting and disconnecting said inductor to one of said voltage source terminal and ground;

an output capacitor connected in parallel with said load terminal for supplying an output voltage signal; and

a controller for controlling said switching networks, said controller comprising;

a first integrator circuit connected to said output capacitor for generating an integrated output voltage signal;

n second integrator circuits, each having an inverting input connected to said inductor of each of said n dc-dc converters, and a non-inverting input connected to receive said integrated output voltage signal; and

n-comparators for outputting a duty cycle signal for said switching networks in each of said n dc-dc converters, each of said n-comparators for comparing an output signal from one of said n-second integrator circuits to a triangle wave; and

a resistive capacitive (RC) network connected between said inductor and ground, and wherein said inverting input of each of said n second integrator circuits is connected to said inductor through said RC network.

13. An interleaved dc-dc voltage converter for a voltage regulator module (VRM) as recited in claim 12 wherein said n dc-dc converters comprise buck converters.

14. An interleaved dc-dc voltage converter for a voltage regulator module (VRM) as recited in claim 12 wherein said triangle wave input to each of said n-comparators is out of phase by 360°

/n degrees.