Linear regulator with improved stability

Patent metadata

Field	Value
Publication number	US-10001795-B2
Application number	US-201615248039-A
Country	US
Kind code	B2
Filing date	Aug 26, 2016
Priority date	Aug 28, 2015
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A linear regulator is presented. It comprises a first amplifier stage, one of the inputs being coupled with the output of the linear regulator. It has an intermediate amplifier stage. The input of the intermediate amplifier stage is coupled to the output of the first amplifier stage. It has a driver stage having a pass device driven by the output of the driver stage. The output of the pass device provides the output of the linear regulator. The regulator has a voltage-to-current feedback circuit coupled with the driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator. The voltage-to-current feedback circuit has a transistor and a current limitation circuit to limit the regulation of the output resistance of the first amplifier stage to low load conditions of the linear regulator.

First claim

What is claimed is:

1. A linear regulator comprising
a first amplifier stage having an input and an output, one of the inputs being coupled with the output of the linear regulator;
an intermediate amplifier stage having an input and an output, the input of the intermediate amplifier stage being coupled to the output of the first amplifier stage;
a driver stage having an input and an output;
a pass device driven by the output of the driver stage, the output of the pass device proving the output of the linear regulator; and
a voltage-to-current feedback circuit coupled with the driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator, the voltage-to-current feedback circuit comprising a transistor and a current limitation circuit to limit the regulation of the output resistance of the first amplifier stage to low load conditions of the linear regulator,
wherein the input of the driver stage is coupled to said output of said intermediate amplifier stage and the gate of the transistor of said voltage-to-current feedback circuit is coupled with the gate of the pass device.

2. The linear regulator of claim 1 , wherein said voltage-to-current feedback circuit provides active pole splitting by gain limitation of the first amplifier stage.

3. The linear regulator of claim 1 , wherein said current limitation circuit comprises a transistor or a current mirror.

4. A linear regulator comprising
a first amplifier stage having an input and an output, one of the inputs being coupled with the output of the linear regulator;
an intermediate amplifier stage having an input and an output, the input of the intermediate amplifier stage being coupled to the output of the first amplifier stage;
a driver stage having an input and an output;
a pass device driven by the output of the driver stage, the output of the pass device proving the output of the linear regulator;
a voltage-to-current feedback circuit coupled with the driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator, the voltage-to-current feedback circuit comprising a transistor and a current limitation circuit to limit the regulation of the output resistance of the first amplifier stage to low load conditions of the linear regulator; and
a driver stage replica coupled between the output of said intermediate amplifier stage and the input of the driver stage, wherein the gate of the transistor of said voltage-to-current feedback circuit is coupled with the driver stage replica.

5. A linear regulator comprising
a first amplifier stage having an input and an output, one of the inputs being coupled with the output of the linear regulator;
an intermediate amplifier stage having an input and an output, the input of the intermediate amplifier stage being coupled to the output of the first amplifier stage;
a driver stage having an input and an output;
a pass device driven by the output of the driver stage, the output of the pass device proving the output of the linear regulator; and
a voltage-to-current feedback circuit coupled with the driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator, the voltage-to-current feedback circuit comprising a transistor and a current limitation circuit to limit the regulation of the output resistance of the first amplifier stage to low load conditions of the linear regulator,
wherein the transistor of said voltage-to-current feedback circuit is in a current mirror configuration with a driver transistor in the driver stage.

6. A linear regulator comprising
a first amplifier stage having an input and an output, one of the inputs being coupled with the output of the linear regulator;
an intermediate amplifier stage having an input and an output, the input of the intermediate amplifier stage being coupled to the output of the first amplifier stage;
a driver stage having an input and an output;
a pass device driven by the output of the driver stage, the output of the pass device proving the output of the linear regulator;
a voltage-to-current feedback circuit coupled with the driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator, the voltage-to-current feedback circuit comprising a transistor and a current limitation circuit to limit the regulation of the output resistance of the first amplifier stage to low load conditions of the linear regulator;
a sink device to sink current from the output of the linear regulator, and a sink driver stage to drive the sink device; and
a sink feedback circuit coupled with the sink driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator, the sink feedback circuit comprising a transistor and a current limitation circuit to limit the regulation of the output resistance of the first amplifier stage to low load conditions.

7. The linear regulator of claim 6 , wherein the current limitation circuit in the sink feedback circuit limits the amount of current that is sinked from the node between the first amplifier stage and the intermediate voltage amplifier stage.

8. The linear regulator of claim 6 , wherein the sink driver stage is coupled with the output of the intermediate amplifier stage or a driver stage replica.

9. The linear regulator of claim 1 , the linear regulator being a low dropout regulator.

10. A method of operating a linear regulator comprising a first amplifier stage;
an intermediate amplifier stage; a driver stage; a pass device; and a voltage-to-current feedback circuit,
wherein the input of the driver stage is coupled to an output of said intermediate amplifier stage and the gate of a transistor of said voltage-to-current feedback circuit is coupled with the gate of the pass device, the method comprising the step of:
limiting the gain of the first amplifier stage at low load conditions of the linear regulator by regulating the output resistance of the first amplifier stage depending on load conditions of the linear regulator,
wherein limiting the gain of the first amplifier stage comprises injecting current into a node between the first amplifier stage and the intermediate voltage amplifier stage, the injected current being dependent on the load current provided by the linear regulator.

11. The method of claim 10 , wherein limiting the gain of the first amplifier stage is restricted to low load conditions by limiting the amount of injected current.

12. A method of operating a linear regulator comprising the steps of:
providing a first amplifier stage having an input and an output, one of the inputs being coupled with the output of the linear regulator;
providing an intermediate amplifier stage having an input and an output, the input of the intermediate amplifier stage being coupled to the output of the first amplifier stage;
providing a driver stage having an input and an output;
providing a pass device driven by the output of the driver stage, the output of the pass device proving the output of the linear regulator; and
providing a voltage-to-current feedback circuit coupled with the driver stage and the output of the first amplifier stage for regulating the output resistance of the first amplifier stage depending on load conditions of the line

Assignees

• Dialog Semiconductor Uk Ltd

Inventors

• Jefremow Mihail
• Ciomaga Dan
• Yang Qiao
• Drebinger Stephan
• Rigoni Fabio

Classifications

• H02M3/155

  using semiconductor devices only · CPC title

• G05F1/575 Primary

  characterised by the feedback circuit · CPC title