Ultrasonic sensor with reverberant vibration suppression circuit

Patent metadata

Field	Value
Publication number	US-12377440-B2
Application number	US-202017130341-A
Country	US
Kind code	B2
Filing date	Dec 22, 2020
Priority date	Jul 6, 2018
Publication date	Aug 5, 2025
Grant date	Aug 5, 2025

Abstract

An ultrasonic sensor is provided in which, after output of an excitation signal from a transmission circuit to a drive electrode is stopped, when a suppression control signal subjected to signal amplification by a band variable calculation amplifier is supplied from a reverberant vibration suppression circuit to the drive electrode, reverberant vibration of a piezoelectric body is reduced or prevented in a reverberation suppression time period. In a reception time period after output of the suppression control signal to the drive electrode is stopped, a signal amplification frequency band of the band variable calculation amplifier is varied by a control circuit, and a signal amplification factor of the band variable calculation amplifier in a frequency band of high-frequency noise that occurs within the band variable calculation amplifier is reduced.

First claim

What is claimed is:

1. An ultrasonic sensor comprising:
an oscillator including a drive electrode to which an excitation signal that causes a vibrating body to vibrate is applied and a detection electrode that extracts a detection signal corresponding to vibration of the vibrating body, and the oscillator being configured to emit an ultrasonic wave;
a transmission circuit configured to output the excitation signal that causes the vibrating body to vibrate to the drive electrode;
a reception circuit configured to receive the detection signal detected by the detection electrode;
a reverberant vibration suppression circuit configured to, after the output of the excitation signal from the transmission circuit to the drive electrode is stopped, amplify a reverberant vibration suppression circuit control signal corresponding to reverberant vibration of the vibrating body output from the reception circuit to generate and supply a suppression control signal that reduces or prevents the reverberant vibration to the drive electrode, and including a band variable calculation amplifier having a variable frequency band of signal amplification without changing a gain of signal amplification in a low frequency range below a cutoff frequency compared to in a high frequency range above the cutoff frequency; and
a control circuit configured to, after output of the suppression control signal from the reverberant vibration suppression circuit to the drive electrode is stopped, vary the variable frequency band of signal amplification of the band variable calculation amplifier.

2. The ultrasonic sensor according to claim 1 , wherein the control circuit varies the variable frequency band of signal amplification by changing a frequency of a dominant pole of the band variable calculation amplifier.

3. The ultrasonic sensor according to claim 1 , further comprising:
a semiconductor switch provided between the reverberant vibration suppression circuit and the drive electrode; wherein
the control circuit controls a conductive state of the semiconductor switch.

4. The ultrasonic sensor according to claim 1 , wherein the band variable calculation amplifier includes a voltage-current conversion circuit configured to convert an input differential voltage to a current, a current-voltage conversion circuit configured to convert the current subjected to conversion by the voltage-current conversion circuit to a voltage, and a variable resistance circuit provided between the voltage-current conversion circuit and the current-voltage conversion circuit and having a resistance value that is varied by the control circuit.

5. The ultrasonic sensor according to claim 4 , wherein the variable resistance circuit includes a MOSFET.

6. The ultrasonic sensor according to claim 3 , further comprising:
a series circuit including a first variable current source, a first resistor, a second resistor, and a second variable current source connected in series in this order between a positive power supply and a negative power supply and in which a connection point between the first resistor and the second resistor is connected to an output of the reverberant vibration suppression circuit; wherein
the semiconductor switch is defined by a transmission gate including a gap between a source and a drain of an n-channel MOSFET and a gap between a source and a drain of a p-channel MOSFET that are connected in parallel, respective sources of the n-channel MOSFET and the p-channel MOSFET that are connected to the connection point between the first resistor and the second resistor, a gate of the n-channel MOSFET that is connected to a connection point between the first variable current source and the first resistor, and a gate of the p-channel MOSFET that is connected to a connection point between the second resistor and the second variable current source.

7. The ultrasonic sensor according to claim 4 , wherein the voltage-current conversion circuit includes a first pair of MOSFETs including gates to which input voltages of a non-inverting input terminal and an inverting input terminal of the band variable calculation amplifier are applied, and a second pair of MOSFETs defining a current mirror circuit.

8. The ultrasonic sensor according to claim 4 , wherein the current-voltage conversion circuit includes a first MOSFET including a gate to which a constant voltage is supplied to define and function as the constant current source, and a second MOSFET connected in series with the first MOSFET and including a gate and a drain between which a capacitor is connected.

Assignees

• Murata Manufacturing Co

Inventors

• Takase Yasuhide

Classifications

• H10N30/20

  with electrical input and mechanical output, e.g. functioning as actuators or vibrators · CPC title

• G01S15/931

  of land vehicles · CPC title

• G01S7/524

  Transmitters · CPC title

• G01S7/521

  Constructional features · CPC title

• B06B2201/55

  Piezoelectric transducer · CPC title