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CN-115884834-B - Driver circuit for capacitive transducer

CN115884834BCN 115884834 BCN115884834 BCN 115884834BCN-115884834-B

Abstract

The present disclosure relates to driver circuits for driving capacitive transducers. The circuit includes an output stage circuit (330) configured to receive an input signal and drive the capacitive transducer (340) to generate an output signal, a variable voltage power supply circuit (320) configured to output a supply voltage of a charge driven output stage circuit, wherein the supply voltage output by the variable voltage power supply circuit varies based on the input signal, a supply capacitor (326, 328) for receiving the supply voltage output by the variable voltage power supply circuit, a storage capacitor (360), and a circuit for transferring charge between the storage capacitor and the supply capacitor (400).

Inventors

  • J.P. Lesotho

Assignees

  • 思睿逻辑国际半导体有限公司

Dates

Publication Date
20260512
Application Date
20210603
Priority Date
20200618

Claims (20)

  1. 1. A circuit for driving a capacitive transducer, the circuit comprising: a charge-driven output stage circuit configured to receive an input signal and drive the capacitive transducer to generate an output signal; a variable voltage power supply circuit configured to output a power supply voltage for a charge-driven output stage circuit, wherein a power supply voltage output by the variable voltage power supply circuit varies based on the input signal; A supply capacitor for receiving the supply voltage output by the variable voltage power supply circuit; a storage capacitor, and A circuit for transferring charge between the storage capacitor and the supply capacitor; wherein the charge driven output stage circuit comprises a charge pump circuit.
  2. 2. The circuit of claim 1, further comprising circuitry configured to transmit a control signal to the variable voltage power supply circuit to cause the variable voltage power supply circuit to adjust a magnitude of the supply voltage of the charge drive output stage circuit based on the input signal.
  3. 3. The circuit of claim 2, wherein the circuit configured to transmit a control signal to the variable voltage power supply circuit to cause the variable voltage power supply circuit to adjust the magnitude of the supply voltage of the charge drive output stage circuit based on the input signal comprises a lead circuit.
  4. 4. The circuit of claim 3, wherein the look-ahead circuit is configured to monitor a level of the input signal, and wherein the control signal is based on the level of the input signal.
  5. 5. The circuit of claim 3 or claim 4, wherein the look-ahead circuit is configured to monitor an envelope of the input signal, and wherein the control signal is based on the envelope of the input signal.
  6. 6. The circuit of any of claims 1-4, wherein the circuit for transferring charge between the storage capacitor and the supply capacitor comprises a switching network and one or more inductors.
  7. 7. The circuit of claim 6, further comprising a control circuit for controlling operation of the switching network to transfer charge between the storage capacitor and the supply capacitor via at least one of the one or more inductors.
  8. 8. The circuit of any of claims 1-4, wherein the variable voltage power supply circuit is configured to output a positive supply voltage and a negative supply voltage of the charge-driven output stage circuit.
  9. 9. The circuit of claim 8, comprising a first supply capacitor for the positive supply voltage and a second supply capacitor for the negative supply voltage.
  10. 10. The circuit of any of claims 1-4, further comprising a signal processing circuit configured to process the input signal and output a processed version of the input signal to the charge-driven output stage circuit.
  11. 11. The circuit of claim 10, wherein the signal processing circuit comprises one or more of: A filter circuit; a digital-to-analog converter circuit; envelope detector circuit, and A delay circuit.
  12. 12. The circuit of any of claims 1-4, wherein the input signal is an audio signal, a haptic signal, or an ultrasonic signal.
  13. 13. The circuit of any of claims 1 to 4, wherein the charge driven output stage circuit comprises a linear amplifier circuit.
  14. 14. The circuit of claim 13, wherein the variable voltage power supply circuit is configured to output a positive supply voltage and a negative supply voltage of the charge-driven output stage circuit, and wherein the linear amplifier circuit comprises: an input stage receiving a fixed supply voltage from a positive voltage supply and a reference voltage supply, an An output stage that receives the positive supply voltage and the negative supply voltage from the variable voltage power supply circuit.
  15. 15. The circuit of any of claims 1 to 4, wherein the charge-driven output stage circuit comprises: A current source; Current groove and The control circuitry is configured to control the operation of the control circuitry, Wherein the control circuit is configured to control operation of the current source and the current sink to selectively charge and discharge the capacitive transducer based on the input signal.
  16. 16. The circuit of any of claims 1-4, further comprising a commutator circuit coupled to the charge-driven output stage circuit, the commutator circuit configured to selectively couple a first or second terminal of the capacitive transducer to an output of the charge-driven output stage circuit.
  17. 17. The circuit of any of claims 1-4, wherein the capacitive transducer comprises a piezoelectric transducer, a MEMS transducer, or an electrostatic transducer.
  18. 18. An integrated circuit comprising the circuit of any one of the preceding claims.
  19. 19. A device comprising the circuit of any one of the preceding claims, wherein the device comprises a mobile phone, a tablet or laptop computer, a smart speaker, or an accessory device.
  20. 20. The device of claim 19, wherein the accessory device comprises a headset.

Description

Driver circuit for capacitive transducer Technical Field The present disclosure relates to driver circuits for capacitive transducers. Background Piezoelectric transducers are increasingly being considered as viable alternatives to transducers such as speakers and resonant actuators for providing audio and/or tactile output in devices such as mobile phones, laptop computers, and tablet computers. Piezoelectric transducers are also increasingly used as transducers for ultrasonic sensing and ranging systems. The piezoelectric transducer may be voltage driven. However, piezoelectric transducers exhibit hysteresis and creep when driven by a voltage, which means that the displacement of the piezoelectric transducer when excited by a voltage depends on both the currently applied voltage and the previously applied voltage. Thus, for any given drive voltage, there are multiple possible displacements of the piezoelectric transducer. For audio applications, this appears as distortion. One way to reduce hysteresis and creep in piezoelectric transducers and associated problems is to drive the transducer with charge rather than voltage. When driven with an electrical charge, the displacement of the piezoelectric transducer varies with the applied electrical charge. Fig. 1 is a schematic diagram of a circuit for driving a piezoelectric transducer with charge. As shown generally at 100 in fig. 1, a charge drive circuit 102, which may be a charge pump circuit, for example, may receive an electrical input signal (e.g., an input audio or ultrasonic signal or a haptic waveform) from an upstream circuit (not shown), such as an amplifier circuit, and drive a piezoelectric transducer 104 to cause the piezoelectric transducer 104 to produce an audible or tactile output based on the electrical input signal. The circuit 100 is also suitable for driving other capacitive transducers, such as capacitive microelectromechanical system (MEMS) transducers or electrostatic transducers. Disclosure of Invention According to a first aspect, the present invention provides a circuit for driving a capacitive transducer, the circuit comprising: An output stage circuit configured to receive an input signal and drive a capacitive transducer to produce an output signal; a variable voltage power supply circuit configured to output a supply voltage for a charge-driven output stage circuit, wherein the supply voltage output by the variable voltage power supply circuit varies based on an input signal; A power supply capacitor for receiving a power supply voltage output by the variable voltage power supply circuit; a storage capacitor, and A circuit for transferring charge between the storage capacitor and the supply capacitor. The output stage circuit may include a charge drive circuit. The circuit may further include circuitry configured to transmit a control signal to the variable voltage power supply circuit to cause the variable voltage power supply circuit to adjust a magnitude of a supply voltage of the output stage circuit based on the input signal. For example, a circuit configured to transmit a control signal to the variable voltage power supply circuit to cause the variable voltage power supply circuit to adjust a magnitude of a supply voltage of the output stage circuit based on the input signal may include a lead circuit. The lead circuit may be configured to monitor a level of the input signal, and the control signal may be based on the level of the input signal. The look-ahead circuit may be configured to monitor an envelope of the input signal and the control signal may be based on the envelope of the input signal. The circuit for transferring charge between the storage capacitor and the supply capacitor may include a switching network and one or more inductors. The circuit may also include a control circuit for controlling operation of the switching network to transfer charge between the storage capacitor and the supply capacitor via at least one of the one or more inductors. The variable voltage power supply circuit may be configured to output a positive supply voltage and a negative supply voltage of the charge-driven output stage circuit. The circuit may comprise a first supply capacitor for a positive supply voltage and a second supply capacitor for a negative supply voltage. The circuit may further include a signal processing circuit configured to process the input signal and output a processed version of the input signal to the charge drive output stage circuit. The signal processing circuitry may include one or more of the following: A filter circuit; a digital-to-analog converter circuit; envelope detector circuit, and A delay circuit. For example, the input signal may be an audio signal. The input signal may be a haptic signal. The input signal may be an ultrasonic signal. The output stage circuit may comprise a charge pump circuit. The output stage circuit may comprise a linear amplifier circuit. The variable voltage power supp