# US 10,310,526 B2 · Quiescent current limitation for a low-dropout regulator in dropout condition > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,310,526 B2 - Document ID: US10310526B2 - Status: Granted - Kind: B2 - Application number: 14/864,987 - Filed: 2015-09-25 - Published: 2016-09-29 - Granted: 2019-06-04 - Earliest claimed: 2015-03-24 - Assignees: Dialog Semiconductor (UK) Limited - Applicants: Dialog Semiconductor (UK) Limited - Inventors: Slawomir Malinowski; Robert Goslawski - Web page: https://patentgrep.com/patent/US10310526B2 ## 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 1/573: with overcurrent detector - G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES ## Abstract An low dropout regulator and method that has reduced quiescent current consumption is presented. The voltage regulator circuit comprises an output terminal, a first circuit branch connected between an input voltage level and the output terminal, a second circuit branch connected between the input voltage level and a predetermined voltage level, a first current mirror for mirroring a current flowing in the second circuit branch to the first circuit branch, a first feedback circuit to regulate the output voltage, and a second feedback circuit for controlling the second switching element. The second feedback circuit comprises a current sensing means for sensing a current that depends on a current flowing in the first circuit branch and to control the second switching element such that the current flowing through the second circuit branch is limited to a current that depends on the current sensed by the current sensing means. ## Claims ### Claim 1 A voltage regulator circuit for outputting a regulated output voltage, comprising an output terminal for outputting the output voltage; a first circuit branch connected between an input voltage level and the output terminal; a second circuit branch connected between the input voltage level and a predetermined voltage level, the second circuit branch comprising a first switching element and a second switching element connected in series; a first current mirror for mirroring a current flowing in the second circuit branch to the first circuit branch; a first feedback circuit for controlling the first switching element in dependence on the output voltage to thereby regulate the output voltage; and a second feedback circuit for controlling the second switching element, wherein the second feedback circuit comprises a current sensing means for sensing a current that depends on a current flowing in the first circuit branch; and the second feedback circuit is configured to control the second switching element such that the current flowing through the second circuit branch is limited to a current that is in a predetermined first ratio to the current sensed by the current sensing means, thereby limiting a quiescent current at low load currents, wherein the second switching element is a transistor that forms a current mirror with another transistor that is coupled in series with the current sensing means and that conducts the sensed current. ### Claim 2 (depends on 1) The voltage regulator circuit according to claim 1, wherein the first circuit branch comprises a first transistor connected between the input voltage level and the output terminal; the second circuit branch comprises a second transistor, a third transistor, and a fourth transistor connected in series; the first transistor and the second transistor form the first current mirror; the third transistor acts as the first switching element; the fourth transistor acts as the second switching element; and the current sensing means is configured to sense a current that depends on a current flowing through the first transistor. ### Claim 3 (depends on 2) The voltage regulator circuit according to claim 2, wherein the current sensing means is configured such that the current sensed by the current sensing means is in a predetermined second ratio to the current flowing through the first transistor. ### Claim 4 (depends on 1) The voltage regulator circuit according to claim 1, wherein the predetermined first ratio is larger than 1. ### Claim 5 (depends on 2) The voltage regulator circuit according to claim 2, wherein the second feedback circuit is configured to control the fourth transistor in dependence on the output voltage and a voltage at an output terminal of the current sensing means. ### Claim 6 (depends on 2) The voltage regulator circuit according to claim 2, wherein the second feedback circuit comprises a third circuit branch connected between the input voltage level and the predetermined voltage level, the third circuit branch comprises a fifth transistor and a sixth transistor connected in series; the fifth transistor acts as the current sensing means; the fifth transistor and the first transistor are configured to form a second current mirror; the fourth transistor and the sixth transistor are configured to form a third current mirror; and the second feedback circuit is configured to control the sixth transistor in dependence on the output voltage and a voltage at an intermediate node between the fifth transistor and the sixth transistor. ### Claim 7 (depends on 6) The voltage regulator circuit according to claim 6, wherein the second feedback circuit is configured to output a drive voltage for driving the sixth transistor in dependence on the output voltage and the voltage at said intermediate node; and the second feedback circuit is configured to drive the sixth transistor such that the current flowing through the fourth transistor increases if the output voltage decreases, and to drive the sixth transistor such that the current flowing through the fourth transistor decreases if the output voltage increases. ### Claim 8 (depends on 6) The voltage regulator circuit according to claim 6, further comprising: a current conveyor circuit receiving a voltage depending on the output voltage and a voltage depending on the voltage at said intermediate node at its input terminals, wherein an output terminal of the current conveyor circuit is connected to a control terminal of the sixth transistor. ### Claim 9 (depends on 8) The voltage regulator circuit according to claim 8, wherein the current conveyor circuit comprises: a fourth circuit branch connected between the output terminal and the predetermined voltage level; and a fifth circuit branch connected between said intermediate node and the predetermined voltage level; the fourth current branch comprises a seventh transistor and a first current sink connected in series; the fifth current branch comprises an eighth transistor and a second current sink connected in series; control terminals of the seventh and eighth transistors are connected to each other; and the output terminal of the current conveyor circuit is arranged between the eighth transistor and the second current sink. ### Claim 10 (depends on 6) The voltage regulator circuit according to claim 6, further comprising a current conveyor circuit receiving a voltage depending on the output voltage and a voltage depending on the voltage at said intermediate node at its input terminals, wherein the current conveyor circuit comprises: a fourth circuit branch connected between the output terminal and the predetermined voltage level, the fourth circuit branch comprising a seventh transistor and a first current sink connected in series; and a fifth circuit branch connected between said intermediate node and the predetermined voltage level, the fifth circuit branch comprising an eighth transistor and a second current sink connected in series; control terminals of the seventh and eighth transistors are connected to each other; the voltage regulator circuit further comprises a ninth transistor arranged in the third circuit branch; and an output terminal of the current conveyor circuit is connected to a control terminal of the ninth transistor. ### Claim 11 (depends on 1) The voltage regulator circuit according to claim 1, further comprising a second error amplifier for controlling the third transistor, wherein the second error amplifier receives a reference voltage and a voltage depending on the output voltage at its positive and negative input terminals; and an output terminal of the second error amplifier is connected to a control terminal of the third transistor. ### Claim 12 A method of operating a voltage regulator circuit for outputting a regulated output voltage, the voltage regulator circuit comprising: an output terminal for outputting the output voltage; a first circuit branch connected between an input voltage level and the output terminal; and a second circuit branch connected between the input voltage level and a predetermined voltage level, the second circuit branch comprising a first switching element and a second switching element connected in series, the method comprising: mirroring a current flowing in the second circuit branch to the first circuit branch; controlling the first switching element in dependence on the output voltage to thereby regulate the output voltage; sensing a current that depends on a current flowing through the first circuit branch; and controlling the second switching element such that the current flowing through the second circuit branch is limited to a current that is in a predetermined first ratio to the sensed current, thereby limiting a quiescent current at low load currents, wherein the second switching element is a transistor that forms a current mirror with another transistor that is coupled in series with the current sensing means and that conducts the sensed current. ### Claim 13 (depends on 12) The method according to claim 12, wherein the first circuit branch comprises a first transistor connected between the input voltage level and the output terminal; and sensing said current is performed such that the sensed current depends on a current flowing through the first transistor. ### Claim 14 (depends on 13) The method according to claim 13, wherein the voltage regulator circuit comprises a second transistor that forms a current mirror with the first transistor and that acts as a current sensing means for sensing said current; and controlling the second switching element is performed in dependence on the output voltage and a voltage at an output terminal of the second transistor. ### Claim 15 (depends on 14) The method according to claim 14, wherein the voltage regulator circuit further comprises a third circuit branch connected between the input voltage level and the predetermined voltage level; the third circuit branch comprises the second transistor and a third transistor connected in series; and the method further comprises: mirroring a current flowing in the third circuit branch to the second circuit branch; and controlling the third transistor in dependence on the output voltage and a voltage at an intermediate node between the second transistor and the third transistor. ### Claim 16 (depends on 15) The method according to claim 15, further comprising: generating a drive voltage for driving the third transistor in dependence on the output voltage and the voltage at said intermediate node, wherein generating the drive voltage is performed such that the current flowing through the second switching element increases if the output voltage decreases, and such that the current flowing through the second switching element decreases if the output voltage increases. ### Claim 17 A method of providing a voltage regulator circuit for outputting a regulated output voltage, comprising the steps of: outputting the output voltage at an output terminal; connecting with a first circuit branch an input voltage level and the output terminal; connecting with a second circuit branch the input voltage level and a predetermined voltage level, the second circuit branch comprising a first switching element and a second switching element connected in series; mirroring with a first current mirror a current flowing in the second circuit branch to the first circuit branch; controlling with a first feedback circuit the first switching element in dependence on the output voltage to thereby regulate the output voltage; and controlling with a second feedback circuit the second switching element, wherein the second feedback circuit comprises a current sensing means for sensing a current that depends on a current flowing in the first circuit branch; and the second feedback circuit controls the second switching element such that the current flowing through the second circuit branch is limited to a current that is in a predetermined first ratio to the current sensed by the current sensing means, thereby limiting a quiescent current at low load currents, wherein the second switching element is a transistor that forms a current mirror with another transistor that is coupled in series with the current sensing means and that conducts the sensed current. ### Claim 18 (depends on 17) The method according to claim 17, wherein the first circuit branch comprises a first transistor connected between the input voltage level and the output terminal; the second circuit branch comprises a second transistor, a third transistor, and a fourth transistor connected in series; the first transistor and the second transistor form the first current mirror; the third transistor acts as the first switching element; the fourth transistor acts as the second switching element; and the current sensing means senses a current that depends on a current flowing through the first transistor. ### Claim 19 (depends on 18) The method according to claim 18, wherein the current sensed by the current sensing means is in a predetermined second ratio to the current flowing through the first transistor. ### Claim 20 (depends on 17) The method according to claim 17, wherein the predetermined first ratio is larger than 1. ### Claim 21 (depends on 18) The method according to claim 18, wherein the second feedback circuit controls the fourth transistor in dependence on the output voltage and a voltage at an output terminal of the current sensing means. ### Claim 22 (depends on 18) The method according to claim 18, wherein the second feedback circuit comprises a third circuit branch connected between the input voltage level and the predetermined voltage level, the third circuit branch comprises a fifth transistor and a sixth transistor connected in series; the fifth transistor acts as the current sensing means; the fifth transistor and the first transistor form a second current mirror; the fourth transistor and the sixth transistor form a third current mirror; and the second feedback circuit controls the sixth transistor in dependence on the output voltage and a voltage at an intermediate node between the fifth transistor and the sixth transistor. ### Claim 23 (depends on 22) The method according to claim 22, wherein the second feedback circuit outputs a drive voltage for driving the sixth transistor in dependence on the output voltage and the voltage at said intermediate node; and the second feedback circuit drives the sixth transistor such that the current flowing through the fourth transistor increases if the output voltage decreases, and to drive the sixth transistor such that the current flowing through the fourth transistor decreases if the output voltage increases. ### Claim 24 (depends on 22) The method according to claim 22, further comprising: a current conveyor circuit receiving a voltage depending on the output voltage and a voltage depending on the voltage at said intermediate node at its input terminals, wherein an output terminal of the current conveyor circuit is connected to a control terminal of the sixth transistor. ### Claim 25 (depends on 24) The method according to claim 24, wherein the current conveyor circuit comprises: a fourth circuit branch connected between the output terminal and the predetermined voltage level; and a fifth circuit branch connected between said intermediate node and the predetermined voltage level; the fourth current branch comprises a seventh transistor and a first current sink connected in series; the fifth current branch comprises an eighth transistor and a second current sink connected in series; control terminals of the seventh and eighth transistors are connected to each other; and the output terminal of the current conveyor circuit is arranged between the eighth transistor and the second current sink. ### Claim 26 (depends on 22) The method according to claim 22, further comprising a current conveyor circuit receiving a voltage depending on the output voltage and a voltage depending on the voltage at said intermediate node at its input terminals, wherein the current conveyor circuit comprises: a fourth circuit branch connected between the output terminal and the predetermined voltage level, the fourth circuit branch comprising a seventh transistor and a first current sink connected in series; and a fifth circuit branch connected between said intermediate node and the predetermined voltage level, the fifth circuit branch comprising an eighth transistor and a second current sink connected in series; control terminals of the seventh and eighth transistors are connected to each other; the voltage regulator circuit further comprises a ninth transistor arranged in the third circuit branch; and an output terminal of the current conveyor circuit is connected to a control terminal of the ninth transistor. ### Claim 27 (depends on 17) The method according to claim 17, further comprising a second error amplifier for controlling the third transistor, wherein the second error amplifier receives a reference voltage and a voltage depending on the output voltage at its positive and negative input terminals; and an output terminal of the second error amplifier is connected to a control terminal of the third transistor.