Low dropout linear regulator with high power supply rejection ratio

Abstract

The invention discloses a low dropout linear regulator with a high power supply rejection ratio. An auxiliary module and a buffer stage are connected to the output end of the error amplifier and the control end of the power switch tube; in the auxiliary module, a power switch tube is scaled down and copied to obtain a first switch tube, the current flowing through a first direct current source ofthe first switch tube and a second switch tube form a current mirror structure, and the current mirrored by the second switch tube generates voltage drop on a first resistor to obtain an auxiliary voltage signal to be connected with the inverting input end of a first operational amplifier; the first operational amplifier, the second resistor and the third resistor form a proportional amplificationcircuit to process the auxiliary voltage signal and output the auxiliary voltage signal to the buffer stage; when the grid voltage of the power switch tube rises or falls, the buffer stage reduces orincreases the load current flowing through the power switch tube, so that the output voltage of the low dropout regulator drops or rises, and the change of the output voltage is offset; and the gridvoltage of the power switch tube does not change along with the change of power ripples, so that a high power supply rejection ratio is realized.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits and relates to a low-dropout linear regulator circuit with high power supply rejection ratio. Background technique [0002] Such as figure 1 Shown is a traditional low-dropout linear regulator circuit, which is usually placed in front of the power receiving unit. A typical low-dropout linear regulator structure generally consists of a voltage reference source VREF, an error amplifier EA, a power transistor MP, and a feedback network Rf1 and Rf2 composition. Its working principle is as follows: use the negative feedback system to sample the output voltage, then compare it with the reference voltage, and stabilize the output voltage Vout through loop adjustment. The error amplifier EA is used to compare the sampling voltage with the reference voltage; the power transistor is the channel through which the load current flows, and its conduction is controlled through a negative feedback l...

AI Technical Summary

Problems solved by technology

[0003] However, when the output voltage Vout of the traditional low-dropout linear regulator circuit increases, the feedback voltage after passing through the resistor divider feedback network will also increase, resulting in an increase in the output voltage of the error amplifier, making the low-dropout linear regulator circuit The output voltage is unstable

In addition, in the traditional low-dropout linear regulator circuit, the ripple and noise on the power supply flow into the load and couple to the gate terminal of the power transistor through the power transistor, and then convert the large transconductance of the power transistor into the current of the output terminal and flow into the load. , which has a large impact on the power supply rejection ratio of the low dropout linear regulator circuit

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