Quiescent current limitation for a low-dropout regulator in dropout condition

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.

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.