Amplifier circuit and methods of operation thereof

Patent metadata

Field	Value
Publication number	US-10587187-B2
Application number	US-201715597900-A
Country	US
Kind code	B2
Filing date	May 17, 2017
Priority date	Jun 30, 2006
Publication date	Mar 10, 2020
Grant date	Mar 10, 2020

Abstract

A signal amplifying circuit and associated methods and apparatuses, the circuit comprising: a signal path extending from an input terminal to an output terminal, a gain controller arranged to control the gain applied along the signal path in response to a control signal; an output stage within the signal path for generating the output signal, the output stage having a gain that is substantially independent of its supply voltage, and a variable voltage power supply comprising a charge pump for providing positive and negative output voltages, the charge pump comprising a network of switches that is operable in a number of different states and a controller for operating the switches in a sequence of the states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage.

First claim

What is claimed is:

1. A charge pump circuit comprising:
a voltage selector for selecting one of a plurality of different voltage inputs as a selected input voltage;
a network of switches; and
a controller for operating said switches in a first mode so as to generate, in use, first and second output voltages of opposite polarity to one another and each substantially equal in magnitude to a fraction of said selected voltage.

2. A charge pump circuit as claimed in claim 1 wherein the network of switches interconnects the voltage selector with a plurality of flying capacitor nodes for connecting to at least one flying capacitor and with first and second output nodes for outputting said first and second output voltages.

3. A charge pump circuit as claimed in claim 2 where said plurality of flying capacitor nodes comprises a plurality of pairs of flying capacitor terminals, each pair of flying capacitor terminals for connection to a respective flying capacitor.

4. A charge pump circuit as claimed in claim 2 wherein said fraction of the magnitude of the input voltage is 1/(n+1) where n is an integer representing the number of flying capacitors connected to said plurality of flying capacitor nodes.

5. A charge pump circuit as claimed in claim 1 wherein the controller is further operable in a second mode, wherein in the second mode the first and second output voltages are of opposite polarity to one another and each equal in magnitude to the magnitude of the input voltage.

6. A charge pump circuit as claimed in claim 5 wherein the voltage selector comprises a first control input for controlling the selection of the input voltage from the plurality of different voltage inputs and the controller comprises a second control input for controlling the operating mode of the charge pump.

7. A charge pump circuit as claimed in claim 6 wherein at least one of:
the mode of operation of the charge pump circuit; and
the voltage input selected by the voltage selector as the selected input voltage;
is controlled, in use, so as to vary the first and second output voltages.

8. An apparatus comprising a charge pump circuit as claimed in claim 1 and a first amplifier circuit in a first audio signal path, wherein the first amplifier circuit is configured to be powered by the first and second output voltages.

9. An apparatus as claimed in claim 8 wherein the controller is configured to determine, in use, whether the audio signal path is operably connected to a headphone load or a line-out load.

10. An apparatus as claimed in claim 8 further comprising a first level-shifter in the first audio signal path upstream of the first amplifier circuit, wherein the first level-shifter is configured to level shift a signal in the first audio signal path from being referenced midway between a first supply voltage and ground to being referenced about ground.

11. An apparatus as claimed in claim 10 wherein the first supply voltage is one of said plurality of different voltage inputs for the voltage selector.

12. An apparatus as claimed in claim 10 further comprising a first signal processing circuit in the first audio signal path upstream of the first level-shifter signal.

13. An apparatus as claimed in claim 12 wherein a signal input to the first signal processing circuit is referenced midway between the first supply voltage and ground.

14. An apparatus as claimed in claim 12 wherein the first signal processing circuit is configured to be powered by the first supply voltage.

15. An apparatus as claimed in claim 8 further comprising a second amplifier circuit in a second audio signal path, wherein the first and second audio signal paths corresponding to different audio channel and wherein the second amplifier circuit is also configured to be powered by the first and second output voltages.

16. An apparatus as claimed in claim 8 wherein the apparatus is at least one of: an audio apparatus; a mobile telephone; an MP3 player; a multimedia player and a laptop computer.

17. A charge pump circuit comprising:
an input node for receiving an input voltage;
first and second output nodes for connection to first and second reservoir capacitors and for outputting first and second output voltages respectively;
a plurality of flying capacitor nodes;
a network of switches for interconnecting said nodes; and
a controller for operating said switches, said controller being operable in a first mode to operate said switches in a sequence of states so as to generate said first and second output voltages wherein, in said first mode, said first and second output voltages are of opposite polarity to one another and each substantially equal in magnitude to a fraction of said input voltage;
wherein the circuit further comprises an input selector for receiving, in use, a plurality of different voltage inputs and operable to select one of said plurality of different voltage inputs as said input voltage received at the input node.

18. A charge pump circuit as claimed in claim 17 wherein, in said first mode, said sequence of states comprises a first state of the first mode in which a flying capacitor connected to the flying capacitor nodes is connected in series with the first reservoir capacitor and a second state in which a flying a flying capacitor connected to the flying capacitor nodes is connected in parallel with the second reservoir capacitor.

19. A variable power supply circuit comprising:
a charge pump configured to output first and second supply voltages of opposite polarity; and
a voltage selector for selecting one of a plurality of different voltage inputs as a selected input voltage for the charge pump;
wherein the charge pump is configured so that a ratio of the magnitude of the first and second supply voltages to the magnitude of the selected input voltage may be controllably selected.

20. A variable power supply circuit as claimed in claim 19 wherein at least one of:
the ratio of the magnitude of the first and second supply voltages to the magnitude of the selected input voltage; and
the voltage input selected by the voltage selector;
is controlled, in use, so as to vary the first and second supply voltages.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Lesso John P
• Pennock John L
• Frith Peter J

Classifications

• H02M3/07 Primary

  using capacitors charged and discharged alternately by semiconductor devices with control electrode {, e.g. charge pumps} · CPC title

• H03F3/187

  in integrated circuits · CPC title

• H03G1/0017

  the device being at least one of the amplifying solid-state elements · CPC title

• H03F1/025

  by using a signal derived from the input signal · CPC title

• H03G1/0088

  using discontinuously variable devices, e.g. switch-operated · CPC title