High PSRR linear voltage regulator and control method thereof

Abstract

A linear voltage regulator comprises a transistor for converting a supply voltage to an output voltage. By directly monitoring the supply voltage and thereby rapidly responding when the supply voltage suffers a ripple, the linear voltage regulator enhances the stability of the output voltage.

Description

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a conventional linear voltage regulator;

FIG. 2 shows an embodiment according to the present invention; and

FIG. 3 shows a waveform of a supply voltage Vin having a ripple thereon.

Claims

1. A linear voltage regulator for converting a supply voltage to an output voltage, the linear voltage regulator comprising: a transistor having an input terminal for receiving the supply voltage, an output terminal for providing the output voltage, and a control terminal for adjusting a channel width of the transistor;a first monitoring circuit for monitoring the output voltage in order to determine an output-dependent signal coupled to the control terminal, so as to regulate the output voltage; anda second monitoring circuit for monitoring the supply voltage in order to determine an input-dependent signal coupled to the control terminal, so as to prevent the output voltage from a perturbation due to a supply voltage ripple.

2. The linear voltage regulator of claim 1, wherein the first monitoring circuit comprises an error amplifier for comparing an output-dependent voltage with a reference voltage to determine the output-dependent signal.

3. The linear voltage regulator of claim 1, wherein the second monitoring circuit comprises: a filter for filtering the supply voltage to produce a delta voltage; anda transimpedance amplifier for determining the input-dependent signal according to the supply voltage and the delta voltage.

4. The linear voltage regulator of claim 3, wherein the filter comprises a low-pass filter.

5. The linear voltage regulator of claim 1, wherein the second monitoring circuit comprises a high-pass filter.

6. A control method for a linear voltage regulator to convert a supply voltage to an output voltage, the control method comprising the steps of: determining an output-dependent signal by monitoring the output voltage for regulating the output voltage; anddetermining an input-dependent signal by monitoring the supply voltage for preventing the output voltage from a perturbation due to a supply voltage ripple.

7. The control method of claim 6, wherein the step of determining an output-dependent signal by monitoring the output voltage comprises the step of comparing an output-dependent voltage with a reference voltage for determining the output-dependent signal.

8. The control method of claim 6, wherein the step of determining an input-dependent signal by monitoring the supply voltage comprises the steps of: determining a delta voltage by filtering the input voltage; anddetermining the input-dependent signal according to the supply voltage and the delta voltage.