Amplifier circuit and methods of operation thereof

Patent metadata

Field	Value
Publication number	US-9306448-B2
Application number	US-201414174553-A
Country	US
Kind code	B2
Filing date	Feb 6, 2014
Priority date	Jun 30, 2006
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

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:
an input terminal and a common terminal for receiving an input voltage;
a first capacitor terminal, the first capacitor terminal being connected, in use, to said common terminal via a first capacitor;
a second capacitor terminal, the second capacitor terminal being connected, in use, to said common terminal via a second capacitor;
first and second flying capacitor terminals for connection, in use, to a flying capacitor;
a switch network that is operable, in use, in a plurality of different switch states to interconnect at least some of said input terminal, said common terminal, said first capacitor terminal, said second capacitor terminal and said first and second flying capacitor terminals;
wherein said switch network is operable, in use, in at least a first mode with only said first and second capacitors and said flying capacitors being connected to said switch network, to operate said plurality of switches in a sequence of said switch states so as to generate a first positive voltage at said first capacitor terminal and a first negative voltage at said second capacitor terminal that are each substantially equal in magnitude to the half the magnitude of said input voltage.

2. A charge pump circuit as claimed in claim 1 wherein switch network is further operable in at least a second mode to operate said plurality of switches in a sequence so as to generate a second positive voltage at said first capacitor terminal and a second negative voltage at said second capacitor terminal that are each substantially equal in magnitude to the magnitude of said input voltage.

3. A charge pump circuit as claimed in claim 1 wherein at least one of said first and second capacitor terminals is connected to an output terminal.

4. A charge pump circuit as claimed in claim 1 wherein, in said first mode, said sequence of switch states comprises at least first and second switch states, wherein:
in the first switch state the first capacitor and flying capacitor are connected in series between the input terminal and the common terminal; and
in the second switch state the flying capacitor is connected in parallel with the second capacitor.

5. A charge pump circuit as claimed in claim 4 wherein, in said first mode, said sequence of switch states further comprises a third switch state in which the flying capacitor is connected in parallel with the first capacitor.

6. A charge pump circuit as claimed in claim 2 wherein, in said second mode, said sequence of switch states comprising at least fourth and fifth switch states, wherein;
in the fourth switch state the first capacitor and flying capacitor are connected in parallel between the input terminal and the common terminal; and
in the fifth switch state the flying capacitor is connected in parallel with the second capacitor.

7. A charge pump circuit as claimed in claim 1 wherein, in said first mode, said sequence of switch states comprises at least sixth and seventh switch states, wherein in:
the sixth switch state the flying capacitor are connected between the input terminal and the common terminal; and
in the seventh switch state the flying capacitor is connected between the first and second capacitor terminals.

8. A charge pump circuit as claimed in claim 2 wherein said controller comprises a control input and operates in said first mode or said second mode based on a control signal received at said control input.

9. A charge pump circuit as claimed in claim 1 comprising:
a first capacitor connected between said first capacitor terminal and said common terminal;
a second capacitor connected between said second capacitor terminal and said common terminal; and
a third capacitor connected between said first and second flying capacitor terminals.

10. A charge pump circuit as claimed in claim 1 comprising an input selector for, in use, selectively varying the voltage input at said input terminal.

11. An audio amplifier circuit comprising:
a charge pump circuit as claimed in claim 1 ;
one or more amplification stages configured to receive a supply voltage from said charge pump circuit.

12. An audio amplifier circuit comprising:
a charge pump circuit as claimed in claim 8 ; and
one or more amplification stages configured to receive a supply voltage from said charge pump circuit;
wherein said control signal is a volume control signal.

13. An audio apparatus comprising an audio amplifier circuit as claimed in claim 11 .

14. An audio apparatus as claimed in claim 13 wherein the audio apparatus comprises at least one: a portable music system, an MP3 player, a mobile telephone handset, a Hi-Fi, an in-car entertainment system and a DVD player.

15. A charge pump circuit comprising:
an input terminal for receiving an input voltage;
first and second reservoir capacitor terminals, for in use, connection to a reference voltage at a common node via respective first and second reservoir capacitors;
first and second flying capacitor terminals;
a switch network for interconnecting said input terminal, said common terminal, said first and second flying capacitor terminals and said first and second reservoir capacitor terminals, the switch network being operable, in use with just said first and second reservoir capacitors and only one flying capacitor connected, to generate, at said first and second reservoir capacitor terminals, either:
a respective first positive voltage and a first negative voltage that are each substantially equal in magnitude to the magnitude of said input voltage; or
a respective second positive voltage and a first negative voltage that are each substantially equal in magnitude to the half the magnitude of said input voltage.

16. A charge pump circuit as claimed in claim 15 wherein at least one of said first and second reservoir capacitor terminals is connected to an output terminal for outputting an output voltage.

17. A charge pump circuit comprising:
a supply input terminal;
a first capacitor terminal for connecting to a first capacitor;
a second capacitor terminal for connecting to a second capacitor;
a common terminal for connecting to a common voltage and connecting to said first and second capacitors;
first and second flying capacitor terminals for connecting to a flying capacitor; and
a switch network, the switch network comprising:
a first switch for connecting the supply input terminal to the first flying capacitor terminal;
a second switch for connecting the first flying capacitor terminal to the first capacitor terminal;
a third switch for connecting the first flying capacitor terminal to the common terminal;
a fourth switch for connecting the second flying capacitor terminal to the first capacitor terminal;
a fifth switch for connecting the second flying capacitor terminal to the common terminal; and
a sixth switch for connecting the second flying capacitor terminal to the second capacitor terminal.

18. A charge pump circuit as claimed in claim 17 wherein said switch network is operable in a first mode in a sequence of states comprising at least a first switch state and a second switch state wherein:
in the first switch state the first switch and the fourth switch are closed and the second, third, fifth and sixth switches are open; and
in the second switch state the third and sixth switches are closed and the first, second, fifth and sixth switches are open.

19. A charge pump circuit as claimed in claim 18 wherein, in said first mode, said sequence of switch states furt

Assignees

• Wolfson Microelectronics Plc
• Cirrus Logic Int Semiconductor Ltd

Inventors

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

Classifications

• H03F3/187

  in integrated circuits · CPC title

• H03G1/0088

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

• H03G1/0094

  using switched capacitors · CPC title

• H03G1/0017

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

• H02M3/07 Primary

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