# US 12,007,801 B2 · Capacitor-less low dropout regulator using dual feedback loop structure

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- Number: US 12,007,801 B2
- Document ID: US12007801B2
- Status: Granted
- Kind: B2
- Application number: 17/885,848
- Filed: 2022-08-11
- Published: 2023-03-16
- Granted: 2024-06-11
- Earliest claimed: 2021-09-16
- Assignees: Korea University Research and Business Foundation
- Applicants: Korea University Research and Business Foundation
- Inventors: Hyung-Min Lee; Hyun Jun Park
- Web page: https://patentgrep.com/patent/US12007801B2

## CPC

- G05F 1/575: characterised by the feedback circuit
- G05F 1/565: sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor (G05F1/563 takes precedence)
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

## Abstract

A capacitor-less low dropout regulator includes: a capacitor-less dual feedback loop unit including a plurality of feedback resistors, an error amplifier, and a transconductance cell to form a main loop passing through the error amplifier and a sub-loop passing through the gm cell without passing through the error amplifier; a dynamic compensation unit connected to a first main pole located at an output of the error amplifier and a second main pole located at an output of the gm cell to provide dynamic frequency compensation using a Miller effect to the first main pole and the second main pole according to a load current of the capacitor-less dual feedback loop unit; and a load current measurement unit configured to measure a load current of a third main pole formed at a load of the dual feedback loop unit to provide the load current to the dynamic compensation unit.

## Claims

### Claim 1

A capacitor-less low dropout regulator using a dual feedback loop structure, comprising:
a capacitor-less dual feedback loop unit including a plurality of feedback resistors, an error amplifier, and a transconductance cell (hereinafter, referred to as a gm cell) to form a main loop passing through the error amplifier and a sub-loop passing through the gm cell without passing through the error amplifier;
a dynamic compensation unit connected to a first main pole located at an output of the error amplifier and a second main pole located at an output of the gm cell to provide dynamic frequency compensation using a Miller effect to the first main pole and the second main pole according to a load current of the capacitor-less dual feedback loop unit; and
a load current measurement unit configured to measure a load current of a third main pole formed at a load of the dual feedback loop unit to provide the load current to the dynamic compensation unit.

### Claim 2 (depends on 1)

The capacitor-less low dropout regulator of claim 1, wherein the dynamic compensation unit includes:
a first compensation capacitor and a second compensation capacitor respectively connected to the first main pole and the second main pole; and
a differential amplifier connected to the second main pole, and configured to apply the Miller effect differently according to the load current transmitted from the load current measurement unit.

### Claim 3 (depends on 2)

The capacitor-less low dropout regulator of claim 2, wherein the dynamic compensation unit further includes a low-pass filter including a first resistor and a second capacitor connected to the second main pole to provide an input bias of the differential amplifier.

### Claim 4 (depends on 3)

The capacitor-less low dropout regulator of claim 3, wherein the dynamic compensation unit further includes a null resistor connected to the first compensation capacitor and the second compensation capacitor in series to remove a right-half plane (RHP) zero generated by the Miller effect.

### Claim 5 (depends on 2)

The capacitor-less low dropout regulator of claim 2, wherein the load current measurement unit adjusts a current of the differential amplifier according to the measured load current.

### Claim 6 (depends on 5)

The capacitor-less low dropout regulator of claim 5, wherein the load current measurement unit adjusts the current of the differential amplifier to be low to increase a gain when the load current is lower than a preset first threshold value, and provides high stability to the load current according to the increased gain.

### Claim 7 (depends on 5)

The capacitor-less low dropout regulator of claim 5, wherein the load current measurement unit adjusts the current of the differential amplifier to be high to reduce a gain when the load current is higher than a preset second threshold value, and improves a transient response characteristic of the load current due to a widened bandwidth according to the reduced gain.

### Claim 8 (depends on 2)

The capacitor-less low dropout regulator of claim 2, wherein the dynamic compensation unit applies a Miller effect as much as the sum of voltage gains of the gm cell and the differential amplifier to the first main pole.

### Claim 9 (depends on 2)

The capacitor-less low dropout regulator of claim 2, wherein the dynamic compensation unit applies a Miller effect as much as a voltage gain of the differential amplifier to the second main pole.