Low power DC-DC converter with improved load regulation

• US 7,990,126 B1
• Filed: 07/22/2009
• Issued: 08/02/2011
• Est. Priority Date: 07/20/2006
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Dai, Shaoan, Zhang, Jiancheng
• Primary Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US12/507,322
• Time in Patent Office: 741 Days
• Field of Search: 323/284, 323/282, 323/283, 323/285, 323/288, 323/222, 323/223, 323/286, 307/103
• US Class Current: 323/284
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence

Abstract

A voltage converter includes, among other things, an amplifier, a voltage combiner, and a hysteretic comparator. The amplifier has a first input terminal which receives a first voltage representative of an output voltage of the voltage converter, a second input terminal which receives a first reference voltage, and an output terminal which generates a second voltage proportional to a difference between the first voltage and the first reference voltage. The voltage combiner combines the second voltage with a second reference voltage to generate a combined voltage. The comparator causes a third voltage to decrease if a feedback voltage defined by the third voltage is detected by the comparator as being greater than a first threshold voltage defined by the combined voltage, and further to cause the third voltage to increase if the feedback voltage is detected by the comparator as being less than the first threshold. The third voltage is applied to a first terminal of a load external to the voltage converter.

Claims

1. A voltage converter comprising:

an amplifier responsive to a first reference voltage and to a first divided voltage indicative of a voltage at a first end of an inductive load;

a voltage combiner that generates a combined voltage based at least in part on an output voltage of the amplifier; and

a comparator that receives the combined voltage, the comparator being responsive to at least the output voltage of the amplifier and a second divided voltage indicative of a voltage at a second end of the inductive load, the comparator generating a comparator output voltage used to control the voltage converter,

wherein the voltage combiner generates the combined voltage based on the output voltage of the amplifier and a second reference voltage, the second reference voltage comprising a non-zero value, wherein the output voltage and the second reference voltage are inputs to the voltage combiner, and

wherein the second reference voltage is substantially equal to the first reference voltage.

2. The voltage converter of claim 1 wherein the first divided voltage comprises a first fraction of the voltage at the first end of the inductive load and the second divided voltage comprises a second fraction of the voltage at the second end of the inductive load.

3. A voltage converter comprising:

an amplifier responsive to a first reference voltage and to a first divided voltage indicative of a voltage at a first end of an inductive load;

a voltage combiner that generates a combined voltage based at least in part on an output voltage of the amplifier;

a comparator that receives the combined voltage, the comparator being responsive to at least the output voltage of the amplifier and a second divided voltage indicative of a voltage at a second end of the inductive load, the comparator generating a comparator output voltage used to control the voltage converter; and

a driver to generate the second divided voltage in response to the comparator output voltage,

wherein the voltage combiner generates the combined voltage based on the output voltage of the amplifier and the second divided voltage, wherein the output voltage and the second divided voltage are inputs to the voltage combiner.

4. The voltage converter of claim 3 further comprising a driver to generate the second divided voltage in response to the comparator output voltage.

5. The voltage converter of claim 3 wherein the first divided voltage comprises a first fraction of the voltage at the first end of the inductive load and the second divided voltage comprises a second fraction of the voltage at the second end of the inductive load.

6. A method of converting a voltage, the method comprising:

amplifying a difference between a first reference voltage and a first divided voltage indicative of a voltage at a first end of an inductive load to thereby generate an amplified difference voltage;

generating a combined voltage based at least in part on the amplified difference voltage that is supplied to a comparator, the comparator being responsive to at least the amplified difference voltage and a second divided voltage indicative of a voltage at a second end of the inductive load;

generating a control voltage based on an output voltage generated by the comparator;

driving an external load in response to the control voltage;

generating the combined voltage based on the amplified difference voltage and the second divided voltage, wherein the amplified difference voltage and the second divided voltage are inputs to a voltage combiner; and

comparing the combined voltage with a second reference voltage to generate the control voltage; and

decreasing the control voltage if the combined voltage is detected as being greater than the second reference voltage and increasing the control voltage if the combined voltage is detected as being smaller than the second reference voltage.

7. The method of claim 6 further comprising:

buffering the control voltage; and

applying the buffered control voltage to the external load.

8. The method of claim 7 further comprising:

dividing the buffered control voltage to generate the second divided voltage.

9. The method of claim 6 wherein the first divided voltage comprises a first fraction of the voltage at the first end of the inductive load and the second divided voltage comprises a second fraction of the voltage at the second end of the inductive load.

10. A method of converting a voltage, the method comprising:

amplifying a difference between a first reference voltage and a first divided voltage indicative of a voltage at a first end of an inductive load to thereby generate an amplified difference voltage;

generating a combined voltage based at least in part on the amplified difference voltage that is supplied to a comparator, the comparator being responsive to at least the amplified difference voltage and a second divided voltage indicative of a voltage at a second end of the inductive load;

generating a control voltage based on an output voltage generated by the comparator;

driving an external load in response to the control voltage;

generating the combined voltage based on the amplified difference voltage and a second reference voltage wherein the amplified difference voltage and the second reference voltage are inputs to a voltage combiner, the second reference voltage comprising a non-zero value; and

comparing the combined voltage with the second divided voltage to generate the control voltage;

buffering the control voltage;

applying the buffered control voltage to the external load; and

dividing the buffered control voltage to generated the second divided voltage.

11. The method of claim 10 further comprising decreasing the control voltage if the combined voltage is detected as being greater than the second divided voltage and increasing the control voltage if the combined voltage is detected as being smaller than the second divided voltage.

12. A voltage converter comprising:

an amplifier that generates an amplified voltage based on a first reference voltage and a first divided voltage indicative of a voltage at a first end of an inductive load;

a voltage combiner that generates a combined voltage based at least in part on the amplified voltage of the amplifier and supplies the combined voltage to a comparator; and

a driver that drives an external load based on an output of the comparator,

wherein the comparator is responsive to at least the amplified voltage and a second divided voltage indicative of a voltage at a second end of the inductive load and wherein the voltage combiner generates the combined voltage based on the amplified voltage of the amplifier and a second reference voltage wherein the amplified voltage and the second reference voltage are inputs to the voltage combiner, the second reference voltage comprising a non-zero value, and

wherein the second reference voltage is substantially equal to said first reference voltage.

13. The voltage converter of claim 12 wherein the first divided voltage comprises a first fraction of the voltage at the first end of the inductive load and the second divided voltage comprises a second fraction of the voltage at the second end of the inductive load.

14. The voltage converter of claim 12 wherein the driver generates the second divided voltage in response to the output of the comparator.

15. A voltage converter comprising:

an amplifier that generates an amplified voltage based on a first reference voltage and a first divided voltage indicative of a voltage at a first end of an inductive load;

a voltage combiner that generates a combined voltage based at least in part on the amplified voltage of the amplifier and supplies the combined voltage to a comparator; and

a driver that drives an external load based on an output of the comparator,

wherein the comparator is responsive to at least the amplified voltage and a second divided voltage indicative of a voltage at a second end of the inductive load and wherein the voltage combiner generates the combined voltage based on the amplified voltage of the amplifier and the second divided voltage, wherein the amplified voltage and the second divided voltage are inputs to the voltage combiner, and

wherein the driver generates the second divided voltage in response to the output of the comparator.

16. The voltage converter of claim 15 wherein the first divided voltage comprises a first fraction of the voltage at the first end of the inductive load and the second divided voltage comprises a second fraction of the voltage at the second end of the inductive load.