Sensing current of a DC-DC converter

Patent metadata

Field	Value
Publication number	US-9618539-B2
Application number	US-201514723769-A
Country	US
Kind code	B2
Filing date	May 28, 2015
Priority date	May 28, 2015
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A DC-DC converter includes a directly coupled inductor with coil elements and power-switching phases. Each phase includes a high-side and low-side switch, where the high-side switch couples a voltage source to a coil element and the low-side switch couples the coil element to a ground voltage. Each switch is configured to be alternately activated and no two switches are activated at the same time. A current sensor for the DC-DC converter includes a single current amplifier having inputs and an output. The output provides a current sensing signal. The current sensor also includes a single RC network coupled to one of the power-switching phases and a first input of the current amplifier. The current sensor also includes a resistive ladder. The ladder includes, for each of the other power-switching phases, a resistor coupled in parallel to the RC network resistor and to a second input of the current amplifier.

First claim

What is claimed is:

1. A current sensor for a DC (‘Direct Current’)-DC converter, the DC-DC converter comprising:
a directly coupled inductor comprising a plurality of coil elements; and
a plurality of power-switching phases, each power-switching phase coupled to a different one of the plurality of coil elements, each phase comprising: a high-side switch and a low-side switch, wherein the high-side switch is configured, when activated, to couple a voltage source to one of the coil elements and the low-side switch is configured, when activated, to couple the coil element to a ground voltage, wherein each switch of the DC-DC converter is configured to be alternately activated and no two switches are activated at the same time;
the current sensor comprising:
a single current amplifier comprising a plurality of inputs and an output, wherein the output provides a current sensing signal;
a single RC network (Resistor-Capacitor network') coupled to one of the power-switching phases and a first input of the current amplifier, the RC network comprising a resistor in series with a capacitor; and
a resistive ladder comprising: for each of the other power-switching phases, a resistor coupled in parallel to the resistor of the RC network and coupled to a second input of the current amplifier.

2. The current sensor of claim 1 wherein the DC-DC converter further comprises a filter and a load coupled to the directly coupled inductor and each switch of the DC-DC converter is configured to be alternately activated by:
activating the high-side switch of a first power-switching phase, including coupling the voltage source to a first coil element, energizing a magnetic core of the directly coupled inductor, and providing, via the first coil element, output current to the filter and load;
activating the low-side switch of the first power-switching phase, including coupling the first coil element to the ground voltage and providing, via a second coil element and the energized magnetic core, output current to the filter and load;
activating the high-side switch of a second power-switching phase, including coupling the voltage source to the second coil element, re-energizing the magnetic core of the directly coupled inductor, and providing, via the second coil element, output current to the filter and load; and
activating the low-side switch of the second power-switching phase, including coupling the second coil element to the ground voltage and providing, via the first coil element and the energized magnetic core, output current to the filter and load.

3. The current sensor of claim 1 wherein each switch of the DC-DC converter is configured to be alternately activated and no two switches are activated at the same time by:
activating each high-side switch for a period of time according to:

D
N

where D represents a duty cycle and N represents the number of power-switching phases; and
activating each low-side switch for a period of time according to:

(

1
-
D

)

N

.

4. The current sensor of claim 1 wherein the number of power-switching phases is inversely proportional to the duty cycle of activating the switches and thereby inversely proportional to the inductance of the directly coupled inductor.

5. The current sensor of claim 1 wherein the DC-DC converter further comprises a filter and a load coupled to the directly coupled inductor and current ripple experienced by the filter and the load comprises:

1

f
*

⁢

L
OL

*

(

1
-

V
OUT

V
IN

)

*

V
OUT

N

,

where f represents the frequency of alternatively activating each switch, L OL represents the open loop inductance of the directly coupled inductor, N represents the number of power-switching phases, V IN represents the voltage of the voltage source and V OUT represents the voltage experienced at the filter and load.

6. The current sensor of claim 1 wherein each high-side switch and each low-side switch comprises a Field Effect Transistor.

7. A method of sensing current of a DC (‘Direct Current’)-DC converter, the DC-DC converter comprising:
a directly coupled inductor comprising a plurality of coil elements; and
a plurality of power-switching phases, each power-switching phase coupled to a different one of the plurality of coil elements, each phase comprising: a high-side switch and a low-side switch, wherein the high-side switch is configured, when activated, to couple a voltage source to one of the coil elements and the low-side switch is configured, when activated, to couple the coil element to a ground voltage, wherein each switch of the DC-DC converter is configured to be alternately activated and no two switches are activated at the same time; and
the method comprises:
measuring a current sensing signal provided by a current sensor, wherein the current sensor comprises:
a single current amplifier comprising a plurality of inputs and an output, wherein the output provides the current sensing signal;
a single RC network (‘Resistor-Capacitor network’) coupled to one of the power-switching phases and a first input of the current amplifier, the RC network comprising a resistor in series with a capacitor; and
a resistive ladder comprising: for each of the other power-switching phases, a resistor coupled in parallel to the resistor of the RC network and coupled to a second input of the current amplifier.

8. The method of claim 7 wherein the DC-DC converter further comprises a filter and a load coupled to the directly coupled inductor and each switch of the DC-DC converter is configured to be alternately activated by:
activating the high-side switch of a first power-switching phase, including coupling the voltage source to a first coil element, energizing a magnetic core of the directly coupled inductor, and providing, via the first coil element, output current to the filter and load;
activating the low-side switch of the first power-switching phase, including coupling the first coil element to the ground voltage and providing, via a second coil element and the energized magnetic core, output current to the filter and load;
activating the high-side switch of a second power-switching phase, including coupling the voltage source to the second coil element, re-energizing the magnetic core of the directly coupled inductor, and providing, via the second coil elem

Assignees

• Lenovo Entpr Solutions Singapore Pte Ltd

Inventors

• Barnette Jamaica L
• Evans Douglas I
• Totten Brian C

Classifications

• G01R19/0092

  Measuring current only · CPC title

• G01R15/146 Primary

  Measuring arrangements for current not covered by other subgroups of G01R15/14, e.g. using current dividers, shunts, or measuring a voltage drop (if no voltage isolation is involved G01R1/203 or G01R19/0092) · CPC title

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title

• H02M1/0048

  Circuits or arrangements for reducing losses (using snubbers H02M1/34) · CPC title

• H02M1/14

  Arrangements for reducing ripples from DC input or output · CPC title