Matching circuit for bridge-driven ultrasonic transducer

Abstract

The utility model discloses a matching circuit used for a bridge type driving ultrasonic transducer, comprising an isolation transformer and at least one inductance switching unit, an input loop of the at least one inductance switching unit is connected with an enable signal of a controller, and an output loop is connected with an output signal of a secondary side of the isolation transformer. The primary side of the isolation transformer is connected with the output end of the bridge circuit, and the output end of at least one inductance switching unit is connected with the input end of the ultrasonic transducer. According to the matching circuit, tuning matching is achieved through series connection of the inductors, variable resistance matching is achieved by adding the isolation transformer, the isolation effect is achieved at the same time, and after matching, the piezoelectric ceramic driving circuit works more stably, and the working efficiency is higher.

Description

Technical Field

[0001] The utility model relates to a piezoelectric ceramic driving circuit, in particular to a matching circuit for a bridge-type driving ultrasonic transducer. Background Art

[0002] Piezoelectric ceramic drive technology is widely used in many fields such as medicine, sonar, measurement and control. Piezoelectric ceramic drive circuit can drive piezoelectric ceramics to generate high-precision adjustable ultrasonic signals.

[0003] The matching of the existing bridge drive circuit is mainly to increase the frequency difference between its parallel resonant frequency and series resonant frequency, that is, to increase the effective electromechanical coupling coefficient. Common matching methods mainly include series capacitor matching, parallel capacitor matching, series inductor matching, and parallel inductor matching. The existing general impedance matching method has a single output frequency and an unsatisfactory output waveform. If the piezoelectric ceramic device is replaced, it needs to be re-matched. In addition, channel crosstalk may also occur when used on multi-channel devices. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the utility model provides a matching circuit for a bridge-driven ultrasonic transducer, which matches driving signals of different frequencies through the mutual cooperation of an inductor switching unit and an isolation transformer, thereby achieving frequency adjustment and reducing channel crosstalk.

[0005] The utility model is realized according to the following technical solutions:

[0006] A matching circuit for a bridge-driven ultrasonic transducer comprises an isolation transformer and at least one inductance switching unit, wherein an input circuit of at least one of the inductance switching units is connected to an enable signal of a controller, an output circuit is connected to an output signal of a secondary side of the isolation transformer, a primary side of the isolation transformer is connected to an output end of a bridge circuit, and an output end of at least one of the inductance switching units is connected to an input end of an ultrasonic transducer.

[0007] The matching circuit of the above technical solution realizes tuning matching through series inductance, realizes variable resistance matching by adding an isolation transformer, and has an isolation effect at the same time. After matching, the piezoelectric ceramic drive circuit works more stably and with higher working efficiency.

[0008] Optionally, when there are multiple inductance switching units, the multiple inductance switching units are connected in series in sequence.

[0009] The specific number of inductors is determined by the frequency of the driving signal. The inductor switching units with the same value are connected in series according to the inductance that needs to be matched.

[0010] Optionally, the inductance switching unit includes a relay and an inductance connected to the relay. When the inductance needs to be connected in series, the relay is controlled to be closed, and when the inductance switching unit is not needed, the relay is controlled to be opened.

[0011] Optionally, the relay includes two input terminals and three output terminals, wherein the two input terminals form an input loop, and the three output terminals form an output loop, the input loop is connected to an enable signal output by a controller, and the output loop is connected to a secondary side of an isolation transformer.

[0012] Optionally, one of the input terminals is connected to the collector of a transistor, the emitter of the transistor is grounded, and the base is connected to the output terminal of the controller.

[0013] Optionally, the controller includes a single-chip microcomputer and an FPGA unit, the single-chip microcomputer outputs an enable signal to the inductance switching unit, and the single-chip microcomputer simultaneously controls the FPGA to generate a drive signal to the bridge drive circuit.

[0014] Optionally, the bridge driving circuit includes a bridge driving chip and a bridge circuit driven by the bridge driving chip.

[0015] Compared with the prior art, the beneficial effects of the utility model are:

[0016] The matching circuit of the utility model includes two parts: variable resistance matching and tuning matching. The variable resistance matching is completed by using a transformer, and the resistance value of the load is adjusted to a value that can meet the requirements of the driving circuit through the transformer. The tuning matching uses an inductor element to match the capacitive reactance transducer and the inductive reactance transducer, and the effective power added to the load is maximized by converting the reactive load into a resistive load.

[0017] The utility model realizes tuning matching by connecting inductors in series, realizes variable resistance matching by adding transformers, and simultaneously has an isolation effect. After matching, the piezoelectric ceramics can work more stably and with higher working efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a matching circuit for a bridge-driven ultrasonic transducer according to an embodiment of the present utility model.

[0019] Figure 2 4 is a circuit diagram of an inductor switching unit according to an embodiment of the present utility model.

[0020] Figure 3 The figure is a circuit diagram of an isolation transformer according to an embodiment of the utility model.

[0021] Figure 4 4 is a circuit schematic diagram of a bridge drive circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0022] The existing common impedance matching method has a single output frequency and an unsatisfactory output waveform. If the piezoelectric ceramic device is replaced, it needs to be re-matched. Channel crosstalk may also occur when used on multi-channel devices. To this end, the utility model provides a matching circuit for a bridge-driven ultrasonic transducer, which can achieve adjustable frequency while reducing channel crosstalk of multi-channel drive signals.

[0023] The following will clearly and completely describe the technical solutions of various embodiments of the utility model in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] Matching circuit for bridge driven ultrasonic transducer, such as Figure 1 As shown, it includes an isolation transformer and at least one inductance switching unit. The isolation transformer is arranged between the bridge drive circuit and the inductance switching unit, and the output end of the inductance switching unit is connected to the ultrasonic transducer. The drive signal output by the bridge drive circuit is matched with variable resistance by the isolation transformer, and then the output signal is sent to the inductance switching unit for tuning and matching, and the tuned and matched drive signal is input to the ultrasonic transducer.

[0025] When the piezoelectric ultrasonic transducer is near the series resonant frequency, it behaves as a variable capacitive load (nonlinear). The transducer is regarded as a capacitive load. In order to offset the influence of the capacitive reactance component, an inductor element is required to tune it when the ultrasonic transducer is working near the resonant frequency. However, the existing impedance matching method has a single output frequency and cannot achieve impedance matching under adjustable matching conditions. Therefore, the utility model sets the tuning matching as multiple inductor switching units with the same matching impedance, and different numbers of inductor switching units can be selected for tuning matching according to different matching requirements.

[0026] Optionally, when there are multiple inductance switching units, the multiple inductance switching units are connected in series in sequence.

[0027] The specific number of inductors is determined by the frequency of the driving signal. The inductor switching units with the same value are connected in series according to the inductance that needs to be matched.

[0028] Furthermore, the inductance value of a single inductor switching unit is 1 uH. If a 5 uH inductor is required for tuning and matching, five inductor switching units are selected to be connected in series.

[0029] Optionally, the inductance switching unit includes a relay and an inductance connected to the relay. When the inductance needs to be connected in series, the relay is controlled to be closed, and when the inductance switching unit is not needed, the relay is controlled to be opened.

[0030] like Figure 2 As shown, the relay model is SRD-05VDC-SL-C. Its pin 2 is the normally open end, pin 3 is the normally closed end, pin 5 is the common end, and pins 1 and 4 are input ends. Pins 2 and 1 are connected to inductor L1 respectively, and the other end of inductor L1 is connected to the ultrasonic transducer. Pin 3 is connected to the power supply VCC.

[0031] Pin 5 is connected to the secondary output signal of the isolation transformer. When the inductor switching unit is started, the driving signal after resistance matching through the isolation transformer is connected to the output loop of the inductor switching unit through pin 5, and is sent to the inductor L1 through pin 2, and is output to the ultrasonic transducer after tuning and matching through the inductor L1.

[0032] Pin 4 is connected to VCC via a rectifier diode U5 and is also connected to the controller via a transistor U6.

[0033] Specifically, pin 4 is connected to the collector of transistor U6, the emitter of transistor U6 is grounded, the base is connected to the controller via resistor R40, and the enable signal output by the controller is accessed to turn on the input loop of the inductor switching unit.

[0034] Optionally, the controller includes a single-chip microcomputer and an FPGA unit, the single-chip microcomputer outputs an enable signal to the inductance switching unit, and the single-chip microcomputer simultaneously controls the FPGA to generate a drive signal to the bridge drive circuit.

[0035] Optionally, the bridge drive circuit includes a bridge drive chip and a bridge circuit driven by the bridge drive chip. Figure 4 As shown, the bridge driver chip is implemented by using the UCC21540DW chip. The bridge circuit is an H bridge.

[0036] The drive signals S1-S4 generated by the FPGA unit are output to control the H bridge through the bridge driver chip, and the drive signals OUT1-OUT2 are generated by controlling the on and off of the MOS tube.

[0037] The H-bridge circuit is composed of NMOS tubes. The amplitude of the output signal of the MOS tube is determined by the drain (S pole) supply voltage, and whether the MOS tube is turned on or not depends on the output signal of the driver chip.

[0038] In order to maximize the rated power output of the power circuit and maximize the efficiency of the power circuit, the load of the circuit must match the output impedance of the power amplifier circuit. Based on this, an isolation transformer for impedance matching is added to the circuit design, such as Figure 3As shown, the primary side of the isolation transformer is connected to the output end of the driving circuit, and the secondary side is connected to the input end of the inductor switching unit. It may affect the circuit operation in the form of leakage inductance, excitation current, etc. For example, to prevent the transformer from instantaneous magnetic saturation during operation, the saturation of the selected magnetic core material should be large enough.

[0039] The variable resistance matching of the utility model is completed by using a transformer, through which the resistance value of the load can be adjusted to a value that can meet the requirements of the driving circuit, and the output voltage utilization factor and current utilization factor can be maximized by variable resistance matching. The tuning matching is completed by using a resonance method, and an inductor element is used to match the capacitive reactance transducer and the inductive reactance transducer.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solution recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solution from the technical solution of the embodiments of the utility model.

Claims

1. A matching circuit for a bridge-driven ultrasonic transducer, characterized in that: It includes an isolation transformer and at least one inductance switching unit, wherein the input circuit of at least one of the inductance switching units is connected to the enable signal of the controller, the output circuit is connected to the output signal of the secondary side of the isolation transformer, the primary side of the isolation transformer is connected to the output end of the bridge circuit, and the output end of at least one of the inductance switching units is connected to the input end of the ultrasonic transducer.

2. The matching circuit for a bridge-driven ultrasonic transducer according to claim 1, characterized in that: When there are multiple inductance switching units, the multiple inductance switching units are connected in series in sequence.

3. The matching circuit for a bridge-driven ultrasonic transducer according to claim 1, characterized in that: The inductance switching unit includes a relay and an inductor connected to the relay.

4. The matching circuit for a bridge-driven ultrasonic transducer according to claim 3, characterized in that: The relay comprises two input terminals and three output terminals, wherein the two input terminals form an input loop, and the three output terminals form an output loop, wherein the input loop is connected to an enable signal output by a controller, and the output loop is connected to a secondary side of an isolation transformer.

5. The matching circuit for a bridge-driven ultrasonic transducer according to claim 4, characterized in that: One of the input ends is connected to the collector of a transistor, the emitter of the transistor is grounded, and the base is connected to the output end of the controller.

6. The matching circuit for a bridge-driven ultrasonic transducer according to claim 5, characterized in that: The controller includes a single chip microcomputer and an FPGA unit. The single chip microcomputer outputs an enable signal to the inductance switching unit, and the single chip microcomputer simultaneously controls the FPGA to generate a drive signal to the bridge drive circuit.

7. The matching circuit for a bridge-driven ultrasonic transducer according to claim 6, characterized in that: The bridge driving circuit includes a bridge driving chip and a bridge circuit driven by the bridge driving chip.

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