Voltage detector and communication circuit including voltage detector

Patent metadata

Field	Value
Publication number	US-11233590-B2
Application number	US-201816224873-A
Country	US
Kind code	B2
Filing date	Dec 19, 2018
Priority date	Dec 21, 2017
Publication date	Jan 25, 2022
Grant date	Jan 25, 2022

Abstract

Disclosed is a voltage detector and a communication circuit capable of detecting a low input voltage. The voltage detector includes: an alternating-current coupling circuit generating a first and a second input voltages according to a source input voltage; a feedback amplifier outputting a branch current according to a sink current including the branch current, and determining an output voltage according to the first input voltage and the amount of the branch current; and an auxiliary circuit outputting the amount of the sink current according to the second input voltage. When the sink current increases as the second input voltage rises, the branch current also increases, so that the output voltage not only rises as the first input voltage rises but also rises as the branch current increases. This feature allows a lower input voltage to be detectable by the detection of the risen output voltage.

First claim

What is claimed is:

1. A voltage detector comprising:
an alternating-current coupling circuit configured to generate a first input voltage and a second input voltage according to a source input voltage;
a feedback amplifier configured to output a branch current according to a sink current and determine an output voltage according to the first input voltage and an amount of the branch current; and
an auxiliary circuit configured to output an amount of the sink current according to the second input voltage, wherein the sink current includes a sum of a predetermined current from a current source of the auxiliary circuit and the branch current, and the branch current is not outputted from the current source.

2. The voltage detector of claim 1 , wherein the feedback amplifier includes:
a first voltage input circuit configured to determine a first output voltage of an output terminal according to the first input voltage and determine a conduction current according to the first input voltage, in which the conduction current passes through the first voltage input circuit;
a current mirror circuit coupled to the output terminal and configured to generate a first current according to the first output voltage, in which the first current includes the branch current and the conduction current; and
an output feedback circuit coupled to the current mirror circuit and configured to generate the output voltage.

3. The voltage detector of claim 2 , wherein the current mirror circuit is configured to generate a second current while a ratio of the second current to the first current is constant or configurable and the output voltage is proportional to the second current.

4. The voltage detector of claim 2 , wherein the feedback amplifier further includes a bias circuit coupled to the first voltage input circuit and the output feedback circuit.

5. The voltage detector of claim 1 , wherein the auxiliary circuit includes:
the current source configured to output the predetermined current; and
a current sink configured to draw the sink current according to the second input voltage.

6. The voltage detector of claim 5 , wherein the current sink includes: a second voltage input circuit configured to output the amount of the sink current according to the second input voltage.

7. The voltage detector of claim 1 , further comprising: a comparing circuit configured to compare the output voltage with a threshold voltage and thereby generate a voltage detection result.

8. A voltage detector comprising:
an alternating-current coupling circuit configured to generate a first input voltage and a second input voltage according to a source input voltage;
a feedback amplifier configured to output a branch current according to a sink current and determine an output voltage according to the first input voltage and an amount of the branch current; and
an auxiliary circuit configured to output an amount of the sink current according to the second input voltage, wherein the sink current includes the branch current,
wherein the source input voltage is composed of two voltages of a differential signal, the first input voltage is composed of two voltages of another differential signal, and the second input voltage is composed of two voltages of yet another differential signal, and the alternating-current coupling circuit includes:
a first terminal configured to receive a positive-terminal input of the source input voltage;
a second terminal configured to receive a negative-terminal input of the source input voltage;
a first alternating-current coupling circuit configured to generate the first input voltage according to the positive-terminal input, the negative-terminal input and a first bias; and
a second alternating-current coupling circuit configured to generate the second input voltage according to the positive-terminal input, the negative-terminal input and a second bias.

9. The voltage detector of claim 8 , wherein the auxiliary circuit includes:
a current source configured to output a predetermined current; and
a current sink configured to draw the sink current including the predetermined current and the branch current.

10. The voltage detector of claim 9 , wherein the current sink includes: a second voltage input circuit configured to output the amount of the sink current according to the second input voltage.

11. The voltage detector of claim 9 , wherein the current source is configured to output the predetermined current according to a third bias while a ratio of the third bias to the second bias is constant or configurable.

12. The voltage detector of claim 11 , further comprising a bias generating circuit including:
a bias current source configured to determine a reference current;
a bias current mirror configured to generate a mirror current according to the reference current, in which a gate voltage of the bias current mirror acts as the second bias; and
a diode-connected transistor, in which a gate voltage of the diode-connected transistor acts as the third bias and the mirror current passes through the diode-connected transistor.

13. A communication circuit including a voltage detector, the communication circuit comprising:
a radio-frequency circuit configured to process a reception signal according to an amplifier gain and thereby generate a source input voltage;
the voltage detector including:
an alternating-current coupling circuit configured to generate a first input voltage and a second input voltage according to the source input voltage;
a feedback amplifier configured to output a branch current according to a sink current and determine an output voltage according to the first input voltage and an amount of the branch current; and
an auxiliary circuit configured to output an amount of the sink current according to the second input voltage, wherein the sink current includes a sum of a predetermined current from a current source of the auxiliary circuit and the branch current, and the branch current is not outputted from the current source;

a comparing circuit configured to compare the output voltage with a threshold voltage and thereby generate a voltage detection result; and
a gain adjusting circuit configured to adjust the amplifier gain according to the voltage detection result.

14. The communication circuit of claim 13 , wherein the feedback amplifier includes:
a first voltage input circuit configured to determine a first output voltage of an output terminal according to the first input voltage and determine a conduction current according to the first input voltage, in which the conduction current passes through the first voltage input circuit;
a current mirror circuit coupled to the output terminal and configured to generate a first current according to the first output voltage, in which the first current includes the branch current and the conduction current; and
an output feedback circuit coupled to the current mirror circuit and configured to generate the output voltage.

15. The communication circuit of claim 13 , wherein the auxiliary circuit includes:
the current source configured to output the predetermined current; and
a current sink configured to draw the sink current according to the second input voltage.

16. The communication circuit of claim 15 , wherein the current sink includes: a second voltage input circuit configured to determine the output of the sink current according to the second input voltage.

Assignees

• Realtek Semiconductor Corp

Inventors

• Lin Chung-Yu

Classifications

• G01R19/165 Primary

  Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values · CPC title

• H03F2200/471

  the voltage being sensed · CPC title

• H03F2200/294

  the amplifier being a low noise amplifier [LNA] · CPC title

• H04B17/409

  by means of resistance, voltage or current measurement · CPC title

• H03F3/193

  with field-effect devices (H03F3/195 takes precedence) · CPC title