Low dropout regulator, method for improving stability of low dropout regulator, and phase-locked loop

Patent metadata

Field	Value
Publication number	US-10296028-B2
Application number	US-201715857037-A
Country	US
Kind code	B2
Filing date	Dec 28, 2017
Priority date	Jun 30, 2015
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

Embodiments of the present invention disclose a low dropout regulator, a method for improving stability of the low dropout regulator, and a phase-locked loop. The low dropout regulator includes: a reference voltage source, an error amplifier, a regulating circuit, a load, a first compensation circuit, and a second compensation circuit. The first compensation circuit is coupled to the regulating circuit, and is configured to regulate a dominant pole and a secondary dominant pole of the low dropout regulator, to regulate a phase margin. The second compensation circuit is configured to: decrease the dominant pole of the low dropout regulator and further increase the secondary dominant pole on the basis that the first compensation circuit has regulated the dominant pole and the secondary dominant pole of the low dropout regulator, so as to regulate the phase margin; and regulate a gain-bandwidth product of the low dropout regulator.

First claim

What is claimed is:

1. A low dropout regulator, comprising:
a reference voltage source, configured to provide a reference voltage;
an error amplifier, coupled to the reference voltage source, and configured to receive a feedback voltage and the reference voltage, compare the feedback voltage with the reference voltage, and output a control voltage according to a result of comparing the feedback voltage with the reference voltage;
a regulating circuit, coupled to the error amplifier, and configured to receive the control voltage, and output a regulating current under control of the control voltage;
a load, coupled to the regulating circuit and the error amplifier, wherein an on-load voltage is formed when the regulating current passes through the load, and the feedback voltage is related to the on-load voltage;
a first compensation circuit, coupled to the regulating circuit, and configured to regulate a dominant pole and a secondary dominant pole of the low dropout regulator, so as to regulate a phase margin; and
a second compensation circuit, coupled to the first compensation circuit, and configured to: decrease the dominant pole of the low dropout regulator and further increase the secondary dominant pole on the basis that the first compensation circuit has regulated the dominant pole and the secondary dominant pole of the low dropout regulator, so as to regulate the phase margin; and regulate a gain-bandwidth product of the low dropout regulator, wherein:
the second compensation circuit comprises a compensation resistor, wherein a terminal of the compensation resistor is connected to an output terminal of the error amplifier, and another terminal of the compensation resistor is connected to a terminal of a nulling resistor and a gate of the transistor.

2. The low dropout regulator according to claim 1 , wherein the regulating circuit comprises a transistor.

3. The low dropout regulator according to claim 2 , wherein:
the first compensation circuit comprises the nulling resistor and a Miller compensation capacitor, wherein a terminal of the Miller compensation capacitor is connected to a drain of the transistor, another terminal of the Miller compensation capacitor is connected to a terminal of the nulling resistor, and another terminal of the nulling resistor is connected to the second compensation circuit.

4. The low dropout regulator according to claim 1 , wherein a resistance value of the compensation resistor is not less than a resistance value of an equivalent load resistor of the error amplifier and is less than or equal to R B-MAX , wherein R B-MAX is a resistance value of the compensation resistor when noise reduced by the compensation resistor is equal to noise introduced by the compensation resistor, and the noise reduced by the compensation resistor is noise that is introduced by another component in the low dropout regulator and that is eliminated by the compensation resistor.

5. The low dropout regulator according to claim 1 , further comprising a feedback circuit, wherein
the feedback circuit is connected to the error amplifier and the load, and is configured to receive the on-load voltage and generate the feedback voltage according to the on-load voltage.

6. The low dropout regulator according to claim 1 , further comprising:
a noise filter circuit, coupled to the reference voltage source and the error amplifier, and configured to perform noise filtering on the reference voltage provided by the reference voltage source, and send, to the error amplifier, the reference voltage on which noise filtering is performed.

7. A phase-locked loop, comprising:
a low dropout regulator, wherein the low dropout regulator comprises:
a reference voltage source, configured to provide a reference voltage;
an error amplifier, coupled to the reference voltage source, and configured to receive a feedback voltage and the reference voltage, compare the feedback voltage with the reference voltage, and output a control voltage according to a result of comparing the feedback voltage with the reference voltage;
a regulating circuit, coupled to the error amplifier, and configured to receive the control voltage, and output a regulating current under control of the control voltage;
a load, coupled to the regulating circuit and the error amplifier, wherein an on-load voltage is formed when the regulating current passes through the load, and the feedback voltage is related to the on-load voltage;
a first compensation circuit, coupled to the regulating circuit, and configured to regulate a dominant pole and a secondary dominant pole of the low dropout regulator, so as to regulate a phase margin; and

a second compensation circuit, coupled to the first compensation circuit, and configured to: decrease the dominant pole of the low dropout regulator and further increase the secondary dominant pole on the basis that the first compensation circuit has regulated the dominant pole and the secondary dominant pole of the low dropout regulator, so as to regulate the phase margin; and regulate a gain-bandwidth product of the low dropout regulator, wherein:
the second compensation circuit comprises a compensation resistor, wherein a terminal of the compensation resistor is connected to an output terminal of the error amplifier, and another terminal of the compensation resistor is connected to a terminal of a nulling resistor and a gate of the transistor.

8. The phase-locked loop according to claim 7 , wherein the regulating circuit comprises a transistor.

9. The phase-locked loop according to claim 8 , wherein:
the first compensation circuit comprises the nulling resistor and a Miller compensation capacitor, wherein a terminal of the Miller compensation capacitor is connected to a drain of the transistor, another terminal of the Miller compensation capacitor is connected to a terminal of the nulling resistor, and another terminal of the nulling resistor is connected to the second compensation circuit.

10. The phase-locked loop according to claim 7 , wherein a resistance value of the compensation resistor is not less than a resistance value of an equivalent load resistor of the error amplifier and is less than or equal to R B-MAX , wherein R B-MAX is a resistance value of the compensation resistor when noise reduced by the compensation resistor is equal to noise introduced by the compensation resistor, and the noise reduced by the compensation resistor is noise that is introduced by another component in the low dropout regulator and that is eliminated by the compensation resistor.

11. The phase-locked loop according to claim 7 , wherein the low dropout regulator further comprising a feedback circuit, wherein
the feedback circuit is connected to the error amplifier and the load, and is configured to receive the on-load voltage and generate the feedback voltage according to the on-load voltage.

12. The phase-locked loop according to claim 7 , wherein the low dropout regulator further comprising:
a noise filter circuit, coupled to the reference voltage source and the error amplifier, and configured to perform noise filtering on the reference voltage provided by the reference voltage source, and send, to the error amplifier, the reference voltage on which noise filtering is performed.

13. A method for improving stability of a low dropout regulator, comprising:
receiving a reference voltage and a feedback voltage;
comparing the feedback voltage with the reference voltage, and generating a control voltage according to a result of comparing the feedback voltage with the reference voltage;
generating a regulating current under control of the control voltage;
regulating

Assignees

• Huawei Tech Co Ltd

Inventors

• Zhang Jinhai
• Cai Fei
• Zhou Shenghua

Classifications

• G05F1/56

  using semiconductor devices in series with the load as final control devices (G05F1/461 takes precedence) · CPC title

• H03L7/08

  Details of the phase-locked loop · CPC title

• G05F1/575 Primary

  characterised by the feedback circuit · CPC title