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Low dropout linear regulator and frequency compensating circuit thereof

A low-dropout linear and frequency compensation technology, which is applied in the direction of instruments, electrical variable adjustment, control/regulation systems, etc., can solve problems such as system instability, achieve the effects of eliminating complex poles, improving system stability, and increasing damping coefficients

Active Publication Date: 2015-06-03
SHENZHEN STATE MICROELECTRONICS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The purpose of the embodiment of the present invention is to provide a frequency compensation circuit for a low-dropout linear regulator, which aims to solve the problem of complex poles generated by the circuit due to too small damping coefficient in the existing cascode Miller compensation mode with a buffer stage , leading to system instability

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  • Low dropout linear regulator and frequency compensating circuit thereof
  • Low dropout linear regulator and frequency compensating circuit thereof
  • Low dropout linear regulator and frequency compensating circuit thereof

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Embodiment 1

[0021] Embodiment 1 of the present invention proposes a frequency compensation circuit for a low-dropout linear regulator, such as figure 2 As shown, for ease of description, only the part related to Embodiment 1 of the present invention is shown.

[0022] In detail, the frequency compensation circuit of the low dropout linear voltage regulator provided by the first embodiment of the present invention adopts a cascode Miller compensation method with a buffer stage to realize frequency compensation. At this time, the low dropout linear regulator includes: an error amplifier 1 with a folded cascode structure, the negative input terminal of the error amplifier 1 is connected to the reference voltage Vref; The output end of the tube 2 is connected to the load; the resistance feedback network 3, the input end of the resistance feedback network 3 is connected to the output end of the adjustment tube 2, and the output end of the resistance feedback network 3 is connected to the posi...

Embodiment 2

[0038] Embodiment 2 of the present invention proposes a frequency compensation circuit for a low-dropout linear regulator, such as Figure 4 As shown, for ease of description, only the part related to Embodiment 2 of the present invention is shown.

[0039] Since in the cascode Miller compensation method with a buffer stage, the unity gain frequency of the low dropout linear regulator increases with the increase of the load current, in order to ensure that the sub-dominant pole frequency is always higher than the unity gain frequency, it is required The buffer stage circuit 4 must consume a larger quiescent current to ensure that the output of the buffer stage circuit 4 has a lower equivalent resistance in the case of a large load current, which will result in high static power consumption of the low dropout linear regulator. In order to solve this problem, different from the first embodiment, the frequency compensation circuit of the low dropout linear voltage regulator provi...

Embodiment 3

[0044] Embodiment 3 of the present invention proposes a frequency compensation circuit for a low-dropout linear regulator, such as Figure 6 As shown, for ease of description, only the part related to Embodiment 3 of the present invention is shown.

[0045] Different from the second embodiment, in the third embodiment, in order to further reduce the output equivalent impedance of the buffer stage circuit 4 without increasing the static current consumption of the buffer stage, the frequency compensation circuit of the low dropout linear regulator can also be It includes: a buffer stage output impedance attenuation circuit 8 connected between the driving end of the adjustment tube 2 and the buffer stage circuit 4 , used to reduce the output equivalent impedance of the buffer stage circuit 4 by using parallel negative feedback.

[0046] Further, as Figure 7 As shown, the output impedance attenuation circuit 8 of the buffer stage may include an N-type twentieth MOS transistor M2...

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Abstract

The invention belongs to the field of low dropout linear regulators, and provides a low dropout linear regulator and a frequency compensating circuit thereof. The low dropout linear regulator comprises an error amplifier with a folded cascode structure or a sleeve structure, wherein the frequency compensating circuit, based on a current buffer stage circuit and a cascode Miller's compensating circuit, further comprises a transconductance boosting circuit. The frequency compensating circuit takes advantage of the positive correlation property of a damping coefficient and common gate transistor transconductance, boosts the equivalent transconductance of a common gate transistor in the error amplifier via the feedback of the transconductance boosting circuit, increases the damping coefficient further, eliminates the complex poles that are possible to appear in the system, and then enhances the stability of the system.

Description

technical field [0001] The invention belongs to the field of low-dropout linear voltage stabilizers, in particular to a low-dropout linear voltage stabilizer and a frequency compensation circuit thereof. Background technique [0002] Low dropout regulator (Low Dropout Regulator, LDO) with low static power consumption is a power management circuit widely used in electronic products. Such as figure 1 As shown, the main circuit of the LDO includes an error amplifier EA, a regulator tube, and a resistor feedback network. The output voltage of the LDO is fed back to the input terminal of the error amplifier EA through the resistance feedback network, and compared with the reference voltage Vref by the error amplifier EA, thereby changing the control signal output by the error amplifier EA, and then adjusting the voltage drop (or equivalent impedance) of the output adjustment tube ), so that the LDO maintains a stable output voltage. [0003] In order to make the LDO maintain t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G05F1/565
Inventor 石彦冷金喜张弛雷军
Owner SHENZHEN STATE MICROELECTRONICS CO LTD
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