US 8,283,906 B2Granted

Voltage regulator

AssigneeSeiko Instruments Inc.

InventorRie Shito

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Abstract

Provided is a voltage regulator that is capable of improving a transient response characteristic while suppressing current consumption. A fluctuating output voltage is detected without increasing the current consumption of a differential amplifier, and a phase compensation resistor (60) is temporarily short-circuited, to thereby decrease a time constant determined by a parasitic capacitance of an output transistor (40) and the phase compensation resistor (60) to improve the transient response characteristic. Alternatively, a voltage divider circuit (50) is short-circuited to temporarily increase the current consumption and correct the output voltage, with the result that the current consumption during a normal operation is relatively low, and the transient response characteristic is improved by increasing a current only during a transient response.

Claims4

Dependent claims

A voltage regulator that operates so as to keep an output voltage constant, comprising:

an output transistor for outputting the output voltage;
a voltage divider circuit for dividing the output voltage to be supplied to an external load to output a divided voltage;
a first differential amplifier for comparing a reference voltage with the divided voltage to output a signal;
a second differential amplifier for amplifying only an AC component of the output voltage, wherein the second differential amplifier has one input terminal input with the output voltage, and another input terminal input with the output voltage from which a high frequency component is removed through a low-pass filter, and amplifies only the AC component of the output voltage;
and
a switch for receiving an output of the second differential amplifier and short-circuiting at least one of a phase compensation resistor and the voltage divider circuit when the output voltage fluctuates by a given voltage or higher, the phase compensation resistor compensating a phase of a control terminal of the output transistor.

3 more elements

Dependencies are inferred from the claim text.