# US 2019/0317537 A1 · N-channel input pair voltage regulator with soft start and current limitation circuitry

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- Number: US 2019/0317537 A1
- Document ID: US20190317537A1
- Status: Published application
- Kind: A1
- Application number: 16/451,601
- Filed: 2019-06-25
- Published: 2019-10-17
- Earliest claimed: 2014-12-29
- Assignees: STMicroelectronics (China) Investment Co., Ltd.
- Applicants: STMicroelectronics (China) Investment Co. Ltd
- Inventors: Zhenghao CUI; Fei Wang; Ming Jiang
- Web page: https://patentgrep.com/patent/US20190317537A1

## CPC

- G05F 1/575: characterised by the feedback circuit
- G05F 1/45: being controlled rectifiers in series with the load
- G05F 3/26: Current mirrors
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

## Abstract

A voltage regulator includes two input pairs of opposite type transistors, p-type and n-type, to provide a soft-start functionality for gradually increasing the voltage regulator's output voltage from zero, or a voltage below the thresholds of the n-type transistors, to an operational voltage. The voltage regulator operates in a soft-start mode during which a variable input voltage signal is ramped up to allow the output voltage to reach the operational voltage, and a normal-operation mode during which the operational voltage is maintained.

## Claims

### Claim 1

A method for operating a voltage regulator, comprising:
generating a soft-start current in response to a difference between a soft-start feedback signal and a variable ramp signal;
generating a control voltage in response to a difference between a normal operation feedback signal and a reference signal;
using the control voltage to control a conductivity of a transistor to pass the soft-start current for output as a drive current for controlling generation of an output voltage; and
controlling said variable ramp signal to:
increase in voltage during a soft-start operating mode; and
remain at a fixed voltage during a normal operating mode following said soft-start operating mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein the fixed voltage is a supply voltage for the voltage regulator.

### Claim 3 (depends on 1)

The method of claim 1, further comprising generating the soft-start feedback signal by dividing the output voltage.

### Claim 4 (depends on 1)

The method of claim 1, further comprising generating the normal operation feedback signal by dividing the output voltage.

### Claim 5

A method for operating a voltage regulator, comprising:
generating an output current applied to an output node of the voltage regulator to produce an output voltage;
generating a soft-start current in response to a difference between a soft-start feedback signal and a variable ramp signal, wherein the soft-start feedback signal is derived from the output voltage;
passing the soft-start current through a source-drain path of a transistor;
adjusting a magnitude of the soft-start current passing through a source-drain path of the transistor by generating a control voltage applied to the gate of the transistor, wherein the control voltage is responsive to a difference between a normal operation feedback signal and a reference signal, and where the normal operation feedback signal is derived from the output voltage;
mirroring the soft-start current received from the source-drain path of the transistor to generate said output; and
controlling said variable ramp signal to:
increase in voltage during a soft-start operating mode; and
remain at a fixed voltage during a normal operating mode following said soft-start operating mode.

### Claim 6 (depends on 1)

The method of claim 1, wherein the fixed voltage is a supply voltage for the voltage regulator.

### Claim 7 (depends on 1)

The method of claim 1, further comprising generating the soft-start feedback signal by dividing the output voltage.

### Claim 8 (depends on 1)

The method of claim 1, further comprising generating the normal operation feedback signal by dividing the output voltage.

### Claim 9

A method for operating a voltage regulator to generate an output voltage signal, comprising:
sourcing an output current to generate the output voltage signal;
operating in a soft-start mode comprising:
varying a variable ramp voltage signal to gradually increase from a starting voltage to an operational voltage during the soft-start mode;
determining a first difference between a first feedback signal that is based on the output voltage signal and the variable ramp voltage signal;
generating a soft start current in response to said first difference; and
mirroring the soft start current to produce said output current; and
operating in a normal-operation mode comprising:
maintaining the operational voltage during the normal-operation mode;
determining a second difference between a second feedback signal that is based on the output voltage signal and a reference signal; and
controlling mirroring of the soft-start current in response to the second difference to produce said output current.