DC/DC power converter

• US 7,400,064 B2
• Filed: 04/22/2005
• Issued: 07/15/2008
• Est. Priority Date: 04/22/2005
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chen, Jun, Hoon, Siew Kuok, Culp, Norman L., Maloberti, Franco
• Primary Examiner(s): Sherry; Michael J
• Assistant Examiner(s): KAPLAN, HAL IRA
• Application Number:
  US11/112,266
• Publication Number:
  US 20060238029A1
• Time in Patent Office: 1,180 Days
• Field of Search: 307/31, 307/39, 315/296, 315/299, 315/300, 315/301, 315/302
• US Class Current: 307/39
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A switching regulation system and control scheme efficiently enables driving multiple loads from a common energy storage element, such as an inductor. The control scheme operates to store energy in the energy storage element over a first portion of a cycle, such as by ramping up current through an inductor, according to energy requirements of the multiple loads. After storing the energy in the storage element during the first portion of the cycle, the stored energy is delivered consecutively to each of the multiple loads over a subsequent portion of the cycle.

Claims

1. A power converter comprising:

at least two switch devices coupled to receive electrical energy from a common energy storage device, each of the at least two switch devices being coupled to regulate an associated output; and

a control system that after causing electrical energy to be stored in the common energy storage device during a first portion of a given cycle, controls the at least two switch devices consecutively to deliver the stored electrical energy to the associated output during a second portion of the given cycle and to provide a discontinuous mode prior to beginning the first portion of a next cycle, wherein the control system adjusts a duration of the first portion of the given cycle for providing current through the common energy storage device as a function of input signals that define regulated electrical energy requirements for each associated output so that sufficient energy is stored in the common energy storage device, the duration of the discontinuous mode changing to accommodate variations in the duration of the first portion and the second portion of the given cycle.

2. The power converter of claim 1, wherein the control system controls the at least two switch devices in a continuous mode during the second portion of the given cycle and then in the discontinuous mode prior to beginning the first portion of the next cycle.

3. The power converter of claim 1, wherein the control system further comprises a control loop associated with each of the at least two switch devices, the control system further comprising logic that controls current through the energy storage device during the first portion of the given cycle based on relative energy requirements for each of the associated outputs.

4. The power converter of claim 3, wherein each of the control loops associated with the at least two switch devices further comprises:

an error amplifier that provides an error signal having a duty cycle indicative of the energy requirements for the associated output, the error signal being determined based on a respective input signal relative to a feedback signal indicative of load current for the associated output; and

a comparator that provides a comparator output signal indicative of a crossing condition based on a comparison of the error signal relative to an indication of current through the energy storage device,

wherein the logic sets a duty cycle for the current through the energy storage device during the first portion of the given cycle based on which comparator output signal for a respective one of the control loops indicates that a crossing condition occurs latest in time.

5. The power converter of claim 3, wherein the control system further comprises another control loop that controls switching between the at least two switch devices during the second portion of the given cycle.

6. The power converter of claim 5, wherein the another control loop further comprises a comparator that compares a feedback signal from one of the associated outputs with a predetermined input signal that sets a regulated value for the one of the associated outputs to control switching between the at least two switch devices during the second portion of the given cycle.

7. The power converter of claim 3, further comprising a load connected at each of the associated outputs, each of the loads being driven based on the electrical energy delivered during consecutive phases of the second portion of the given cycle, an indication of current through each of the loads being provided as feedback to each of the control loops.

8. The power converter of claim 7, wherein the each of the loads comprises at least one light emitting diode.

9. The power converter of claim 1, wherein the common energy storage device comprises at least one inductor.

10. An integrated circuit comprising the power converter of claim 1.

11. A control system for regulating multiple outputs, comprising:

first means for, when activated, electrically coupling an energy storage element with a first output of the multiple outputs;

second means for, when activated, electrically coupling the energy storage element with a second output of the multiple outputs;

means for causing current through the energy storage element during a first portion of a given cycle to store electrical energy in the energy storage element, wherein the means for causing controls the current through the energy storage element based on the indication of electrical current through the first load relative to a first input signal and based on the indication of electrical current through the second load relative to a second input signal;

means for consecutively activating the first means and the second means such that stored electrical energy is delivered from the energy storage element to the first output during a first phase of a second portion of the given cycle and such that stored electrical energy is delivered from the energy storage element to the second output during a second phase of the second portion of the given cycle and a discontinuous phase prior to beginning the first phase of a next cycle, wherein the means for consecutively activating controls the first and second means based on at least one of the indication of electrical current through the first load and the indication of electrical current through the second load relative to at least one of the respective first input signal and the second input signal;

means for feeding back an indication of electrical current through a first load connected at the first output;

means for feeding back an indication of electrical current through a second load connected at the second output; and

logic means for controlling a duty cycle of the current through the energy storage element during the first portion of the given cycle according to which of the first and second loads have greater energy requirements.

12. The system of claim 11, further comprising means for determining the energy requirements of each of the first and second loads by comparing the indication of electrical current through the first load relative to the first input signal and by comparing the indication of electrical current through the second load relative to the second input signal.

13. The system of claim 11, wherein each of the first and second loads comprises at least one light emitting diode.

14. An integrated circuit comprising the system of claim 11.

15. A power converter comprising:

current input operative to receive electrical current from an associated energy storage element;

a first switch device coupled between the current input and a first output;

a second switch device coupled between the current input and a second output;

a first control loop that feeds back an indication of current through a first load connected at the first output and determines energy requirements of the first load based on the indication of current through the first load relative to a predetermined first input signal that sets regulated energy requirements for the first load;

a second control loop that feeds back an indication of current through a second load connected at the second output and determines energy requirements of the second load based on the indication of current through the second load relative to a predetermined second input signal that sets regulated energy requirement for the second load;

logic that controls a duty cycle of current through the energy storage element based on the relative energy requirements of the first load and the second load such that sufficient energy is stored in the energy storage element during a first portion of a given cycle; and

a third control loop that controls the first switch device to deliver stored electrical energy from the energy storage element to the first output during a first phase of a second portion of the given cycle and that controls the second switch device to deliver stored electrical energy from the energy storage element to the second output during a second phase of a second portion of the given cycle, the first and second phases of the second portion of the given cycle occurring consecutively in a continuous mode.

16. The power converter of claim 15, wherein the first load comprises at least one light emitting diode and the second load comprises at least one light emitting diode.

17. An integrated circuit comprising the power converter of claim 15, wherein the energy storage element comprises an inductor.