Class-H Switching Amplifier Circuit Having Supply Voltage Proportional To An Audio Signal

• US 20180337637A1
• Filed: 05/18/2017
• Published: 11/22/2018
• Est. Priority Date: 05/18/2017
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: GALAL, Sherif, CHAKKIRALA, Subbarao Surendra, ABDELFATTAH, Khaled, SCHREYER, Earl
• Granted Patent: US 10,326,405 B2
• Time in Patent Office: Days
• CPC Class Codes: H03F 1/0216 Continuous control
• CPC Class Codes: H03F 1/0233 by using a signal derived from the output signal, e.g. bootstrapping the voltage supply
• CPC Class Codes: H03F 2200/03 the amplifier being designed for audio applications
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit
• CPC Class Codes: H03F 2200/504 the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier
• CPC Class Codes: H03F 2200/555 A voltage generating circuit being realised for biasing different circuit elements
• CPC Class Codes: H03F 3/181 Low-frequency amplifiers, e.g. audio preamplifiers
• CPC Class Codes: H03F 3/185 with field-effect devices H03F3/187 takes precedence
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers
• CPC Class Codes: H03F 3/2175 using analogue-digital or digital-analogue conversion H03F3/2173 takes precedence
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

An amplifier circuit includes an amplifier and a voltage boost circuit configured to provide a variable supply voltage to the amplifier, the variable supply voltage continuously proportional to an audio input signal, the variable supply voltage configured to follow an output of the amplifier.

Claims

1. An amplifier circuit, comprising:

an amplifier;

a voltage boost circuit configured to provide a variable supply voltage to the amplifier, the variable supply voltage continuously proportional to an audio input signal, the variable supply voltage configured to follow an output of the amplifier with a variable decay; and

a boost controller configured to generate a control signal configured to control the variable supply voltage using the variable decay.

2. The amplifier circuit of claim 1, wherein the amplifier comprises a class D amplifier;

and

wherein a voltage headroom value between an output of the voltage boost circuit and an output of the class-D amplifier is proportional to a magnitude of the audio input signal.

3. The amplifier circuit of claim 1, wherein the audio input signal is an audio input signal to the amplifier and the voltage boost circuit is configured to receive a voltage boost circuit input signal, the voltage boost circuit input signal comprising a multiple-bit representation of the audio input signal and a voltage headroom value.

4. The amplifier circuit of claim 3, wherein the multiple-bit representation of the audio input signal and the voltage headroom value comprises 8-bits.

5. The amplifier circuit of claim 3, wherein when the output of the amplifier exceeds a threshold, the voltage boost circuit provides a boost voltage to the class-D amplifier in addition to a fixed voltage.

6. The amplifier circuit of claim 1, wherein the voltage boost circuit and the amplifier have similar signal processing delay.

8. The amplifier circuit of claim 5, wherein the threshold comprises a voltage at which the voltage boost circuit transitions between a bypass mode and a boost mode.

9. The amplifier circuit of claim 8, wherein the multiple-bit representation of the audio input signal and the voltage headroom value is compared against the fixed voltage to determine whether the voltage boost circuit provides the boost voltage in addition to the fixed voltage.

10. The amplifier circuit of claim 8, wherein when the voltage boost circuit enters boost mode, the voltage boost circuit and the amplifier operate as a class-H amplifier circuit.

12. The amplifier circuit of claim 1, wherein the variable decay is chosen to allow the variable supply voltage to adjustably follow the output of the amplifier.

13. The amplifier circuit of claim 12, further comprising a counter configured to further adjustably control a rate at which the variable supply voltage adjustably follows the output of the amplifier.

7. (canceled)

11. (canceled)

14. A device, comprising:

means for amplifying an audio input signal; and

means for providing a variable supply voltage to the amplifying means, the variable supply voltage continuously proportional to an audio input signal, the variable supply voltage configured to follow an output of the amplifying means with a variable decay; and

means for generating a control signal configured to control the variable supply voltage using the variable decay.

15. The device of claim 14, further comprising means for providing a variable voltage headroom value between the variable supply voltage and an output of the amplifying means, the variable voltage headroom value being proportional to a magnitude of the audio input signal.

16. The device of claim 14, wherein the means for providing a variable supply voltage is configured to receive a voltage boost circuit input signal, the voltage boost circuit input signal comprising a multiple-bit representation of the audio input signal and a voltage headroom value.

17. The device of claim 16, wherein the multiple-bit representation of the audio input signal and the voltage headroom value comprises 8-bits.

18. The device of claim 16, further comprising means for providing a boost voltage for amplifying the audio input signal in addition to a fixed voltage when the output of the amplifying means exceeds a threshold.

19. The device of claim 18, further comprising means for varying a rate of decay with which the variable supply voltage follows the output of the amplifying means.

20. The device of claim 19, wherein the means for varying the rate of decay allows the variable supply voltage to adjustably follow the output of the amplifying means.

21. The device of claim 20, further comprising means for counting configured to further adjustably control the rate of decay with which the variable supply voltage adjustably follows the output of the amplifying means.

22. A method for operating an amplifier, comprising:

amplifying an audio input signal;

providing a variable supply voltage for amplifying the audio input signal, the variable supply voltage continuously proportional to an audio input signal, the variable supply voltage configured to follow an amplified audio output signal with a variable decay; and

generating a control signal configured to control the variable supply voltage using the variable decay.

23. The method of claim 22, further comprising providing a variable voltage headroom value between the variable supply voltage and the amplified audio output signal, the variable voltage headroom value being proportional to a magnitude of the audio input signal.

24. The method of claim 22, wherein the audio input signal is provided to the class-D amplifier and a voltage boost circuit input signal comprises a multiple-bit representation of the audio input signal and a voltage headroom value.

25. The method of claim 24, wherein the multiple-bit representation of the audio input signal and the voltage headroom value comprises 8-bits.

26. The method of claim 24, further comprising providing a boost voltage for amplifying the audio input signal in addition to a fixed voltage when the amplified audio output signal exceeds a threshold.

27. The method of claim 22, further comprising the variable supply voltage following the amplified audio output signal with a variable decay.

28. The method of claim 27, wherein the variable decay allows the variable supply voltage to adjustably follow the amplified audio output signal.

29. The method of claim 28, further comprising adjustably controlling the variable decay using a counter.

30. The method of claim 29, wherein adjustably controlling the variable decay comprises lengthening a time during which the variable supply voltage follows the amplified audio output signal.