Advanced load current monitoring circuit and method for a class-AB amplifier

Patent metadata

Field	Value
Publication number	US-10944366-B2
Application number	US-201916291971-A
Country	US
Kind code	B2
Filing date	Mar 4, 2019
Priority date	Mar 4, 2019
Publication date	Mar 9, 2021
Grant date	Mar 9, 2021

Abstract

In an embodiment, a class-AB amplifier includes: an output stage that includes a pair of half-bridges configured to be coupled to a load; and a current sensing circuit coupled to a first half-bridge of the pair of half-bridges. The current sensing circuit includes a resistive element and is configured to sense a load current flowing through the load by: mirroring a current flowing through a first transistor of the first half-bridge to generate a mirrored current, flowing the mirrored current through the resistive element, and sensing the load current based on a voltage of the resistive element.

First claim

What is claimed is:

1. A class-AB amplifier comprising:
an output stage that comprises a pair of half-bridges configured to be coupled to a load; and
a current sensing circuit having a high impedance input coupled to a first half-bridge of the pair of half-bridges, the current sensing circuit comprising a resistive element and configured to sense a load current flowing through the load by:
mirroring a current flowing through a first transistor of the first half-bridge to generate a mirrored current based on the high impedance input of the current sensing circuit,
flowing the mirrored current through the resistive element, and
sensing the load current based on a voltage of the resistive element, wherein the mirrored current is configured to flow through a path different from the load.

2. A class-AB amplifier comprising:
an output stage that comprises a pair of half-bridges configured to be coupled to a load; and
a current sensing circuit coupled to a first half-bridge of the pair of half-bridges, the current sensing circuit comprising a resistive element and configured to sense a load current flowing through the load by:
mirroring a current flowing through a first transistor of the first half-bridge to generate a mirrored current,
flowing the mirrored current through the resistive element, and
sensing the load current based on a voltage of the resistive element, wherein the current sensing circuit further comprises:

a second transistor having a control terminal coupled to an output of the first half-bridge;
a third transistor having a control terminal coupled to a current path of the second transistor;
a sense transistor having a control terminal coupled to a control terminal of the first transistor and having a current path coupled to a current path of the third transistor; and
a current mirror coupled between the sense transistor and the resistive element, the current mirror configured to generate the mirrored current.

3. The class-AB amplifier of claim 2 , wherein the first transistor and the sense transistor are matching transistors.

4. The class-AB amplifier of claim 3 , wherein the first transistor has a first portion and a second portion disposed in a semiconductor substrate, and wherein the sense transistor is disposed between the first portion and the second portion.

5. The class-AB amplifier of claim 4 , wherein the first portion corresponds to a first half of the first transistor, and the second portion corresponds to a second half of the first transistor.

6. The class-AB amplifier of claim 2 , wherein the current mirror comprises a current mirror transistor configured to adjust a mirroring ratio of the current mirror based on a control signal.

7. The class-AB amplifier of claim 6 , wherein the current sensing circuit further comprises:
a second current mirror coupled between the sense transistor and the current mirror, the second current mirror comprising a second current mirror transistor configured to adjust a mirroring ratio of the second current mirror based on a second control signal.

8. The class-AB amplifier of claim 1 , further comprising an analog-to-digital converter (ADC) configured to generate a digital signal based on the voltage of the resistive element.

9. A class-AB amplifier comprising:
an output stage that comprises a pair of half-bridges configured to be coupled to a load;
a current sensing circuit coupled to a first half-bridge of the pair of half-bridges, the current sensing circuit comprising a resistive element and configured to sense a load current flowing through the load by:
mirroring a current flowing through a first transistor of the first half-bridge to generate a mirrored current,
flowing the mirrored current through the resistive element, and
sensing the load current based on a voltage of the resistive element;

an analog-to-digital converter (ADC) configured to generate a digital signal based on the voltage of the resistive element;
a reference resistor; and
a reference current source configured to inject a reference current into the reference resistor to generate a reference voltage, wherein the ADC is configured to receive the reference voltage, wherein the resistive element comprises a first resistor, and wherein the first resistor and the reference resistor are matching resistors.

10. The class-AB amplifier of claim 8 , further comprising a fully-differential buffer coupled between the resistive element and the ADC, wherein the ADC is configured to receive a reference voltage, and wherein the fully-differential buffer is configured to level-shift the voltage of the resistive element to have a DC bias substantially equal to a DC bias of comparators in the ADC, and wherein the DC bias of comparators in the ADC is based on the reference voltage.

11. The class-AB amplifier of claim 8 , further comprising a digital core circuit configured to receive the digital signal from the ADC and configured to calculate a load impedance based on the digital signal.

12. The class-AB amplifier of claim 8 , further comprising a digital core circuit configured to receive the digital signal from the ADC and configured to limit the load current based on the digital signal.

13. The class-AB amplifier of claim 1 , further comprising the load, wherein the load is an audio speaker coupled the pair of half-bridges.

14. The class-AB amplifier of claim 1 , wherein the first transistor is a low-side transistor of the pair of half-bridges.

15. The class-AB amplifier of claim 1 , wherein the resistive element comprises a resistor having a resistance of 10Ω or higher.

16. A digital input class-AB amplifier comprising:
an output stage that comprises a pair of half-bridges configured to be coupled to a load;
a digital communication interface configured to receive an data stream;
a digital core circuit;
a digital-to-analog converter (DAC);
a driver circuit configure to receive a signal from the DAC, and configured to control the output stage based on the received signal;
a current sensing circuit coupled to a first half-bridge of the pair of half-bridges, the current sensing circuit comprising a resistive element and configured to sense a load current flowing through the load by:
mirroring a current flowing through a first transistor of the first half-bridge to generate a mirrored current,
flowing the mirrored current through the resistive element, and
sensing the load current based on a voltage of the resistive element; and

an analog-to-digital converter (ADC) coupled to the digital core circuit and configured to generate a digital signal based on the sensed load current.

17. The digital input class-AB amplifier of claim 16 , wherein the digital core circuit is configured to receive real-time load current data from the ADC.

18. The digital input class-AB amplifier of claim 17 , wherein the digital core circuit is further configured to send the real-time load current data to an external user via the digital communication interface.

19. The digital input class-AB amplifier of claim 17 , wherein the digital core circuit is further configured to calculate a load impedance of the load based on the real-time load current data.

20. The digital input class-AB amplifier of claim 19 , wherein the digital core circuit is further configured to send the load impedance via the digital communication interface.

21. The digital input class-AB amplifier of claim 17 , wherein the digital core circuit is further configured to limit the load current based on the

Assignees

• Stmicroelectronics Shenzhen R&D Co Ltd

Inventors

• Du Ru Feng
• Li Xiangsheng

Classifications

• H03F3/2173

  of the bridge type · CPC title

• H03F3/20 Primary

  Power amplifiers, e.g. Class B amplifiers, Class C amplifiers (H03F3/26 - H03F3/30 take precedence) · CPC title

• H03F3/3064

  with symmetrical driving of the end stage · CPC title

• H03F1/523 Primary

  for amplifiers using field-effect devices (H03F1/526 takes precedence) · CPC title

• H03F2203/30078

  A resistor being added in the pull stage of the SEPP amplifier · CPC title