JP4512721B2 - Oscillation control circuit of multi-frequency ultrasonic cleaner - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an oscillation control circuit of a multi-frequency ultrasonic cleaner that performs alternating high-speed switching by tracking power and frequency.
[0002]
[Prior art]
Conventionally, the drive oscillation circuit of an alternating-switching type / multi-frequency ultrasonic cleaner has different impedances of vibrators at the respective drive frequencies, so the power input to the vibrator varies for each drive frequency, and Since the impedance of each mechanical resonance frequency also changes due to the influence of the liquid depth, temperature, type of liquid, object to be cleaned, etc., the input power to the vibrator changes greatly.
[0003]
[Problems to be solved by the invention]
For this reason, there is a problem that cleaning failure due to power drop, destruction of the vibrator due to overpower input, or element destruction beyond the safe area due to excessive output of the power element of the oscillator occurs, while the power input to the vibrator is Since it becomes maximum at each resonance frequency, in order to realize constant power control in real time in multi-frequency high-speed switching drive, there is a problem that stable tracking of each resonance frequency and improvement of tracking speed at frequency switching are required. there were.
[0004]
[Means to solve the problem]
The present invention relates to at least two phase shifters that change the phase of an output current input to a vibrator mounted in a cleaning tank, at least two phase lock loop circuits that lock the phase of the phase shifter, and the two phase locks A frequency control circuit comprising a data selector for alternately selecting output data of the loop circuit with a clock, a pulse width control circuit for controlling the pulse width of the output of the data selector, and switching for amplifying the output of the pulse width control circuit A power amplifier, a matching circuit for matching alternate outputs of the switching power amplifier, a current detection element for detecting an output current of the matching circuit, and a first circuit for converting the output current detected by the current detection element into an impedance. 1 impedance converter, a voltage divider that divides the voltage input to the vibrator, and the divided voltage A second impedance converter for converting to impedance, a multiplier for multiplying the outputs of the first impedance converter and the second impedance converter, a low-pass filter that passes a low frequency of the output of the multiplier, and the low-pass A power measuring circuit comprising a DC amplifier for amplifying the output of the filter, and a negative feedback circuit for inputting the output of the DC amplifier of the power measuring circuit to the negative terminal and inputting a reference voltage for power control to the positive terminal, The output of the negative feedback circuit is input to the pulse width control circuit, the power input to the vibrator is controlled to automatically track the frequency, and the phase-locked loop circuit includes the phase shifter A phase comparator that compares the phases of the signals from the output, a loop filter that passes through a loop of the output of the phase comparator, and an output voltage of the loop filter, An analog switch that alternately switches a constant voltage with a clock, and a voltage-controlled oscillation circuit that oscillates with an input voltage. Further, the pulse width control circuit includes an integration circuit and a window comparator. The output of the frequency control circuit is input to the circuit, and the output of the negative feedback circuit is input to the window comparator.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a plurality of mechanical resonances existing in one vibrator are used to drive each resonance frequency alternately at high speed, thereby moving a standing wave and reducing cleaning unevenness. The damage to the object to be cleaned can be reduced, and the life of the vibrator can be extended.
[0006]
【Example】
FIG. 1 is a block diagram of an oscillation control circuit of a multi-frequency ultrasonic cleaner according to an embodiment of the present invention. The frequency control circuit 1 includes a first phase shifter 2, a second phase shifter 3, and a first phase locked loop. The circuit 4, the second phase locked loop circuit 5, and the data selector 6, the output of the first phase shifter 2 is input to the first phase locked loop circuit 4, and the output of the second phase shifter 3 is the first 2 and the outputs of the first and second phase-locked loop circuits 4 and 5 are alternately taken into the data selector 6 by the clock 7.
[0007]
The output of the data selector 6 is input to the pulse width control circuit 8, the output of the pulse width control circuit 8 is input to the switching power amplifier 9, the output of the switching power amplifier 9 is input to the matching circuit 10, and the matching circuit 10 Is input to the vibrator 11, and the vibrator 11 is attached to the cleaning tank 13 in which the liquid 12 is placed.
[0008]
The power measuring circuit 14 includes a first impedance converter 15, a second impedance converter 17 to which the output of the voltage divider 16 is connected, and outputs of the first and second impedance converters 15 and 17. The multiplier 18 includes a multiplier 18, a low-pass filter 19, and a DC amplifier 20. The output of the DC amplifier 20 is connected to the negative terminal of the negative feedback circuit 21, and the reference power supply 22 is connected to the positive terminal of the negative feedback circuit 21. Is supplied with a reference voltage for power control, the output of the negative feedback circuit 21 is input to the pulse width control circuit 8, and the current is detected by the current detector 23 from the output of the matching circuit 10, and the detected current is In addition to being input to the first and second phase shifters 2 and 3, the first impedance converter 15 of the power measurement circuit 14 is also input, and the output of the matching circuit 10 is the power measurement circuit. Is input to the voltage divider 16 of 14.
[0009]
In the oscillation control circuit of the multi-frequency ultrasonic cleaner of this embodiment configured as described above, the output current of the matching circuit 10 detected by the current detector 23 is sent to the first and second phase shifters 2 and 3. Respectively input as feedback currents, the outputs of the first and second phase shifters 2 and 3 are phase-locked by the first and second phase-locked loop circuits 4 and 5, respectively. The outputs of the loop circuits 4 and 5 are selected by the clock 6 and input to the data selector 6, and the pulse width selected by the data selector 6 is controlled by the pulse width control circuit 8, and the switching power amplifier 9 When amplified, the matching circuit 10 matches the two pulses, and inputs them to the vibrator 11, so that the vibrator 11 resonates at two frequencies and generates ultrasonic waves with no variation. The object to be cleaned, which is placed in a cleaning tank 13 by the ultrasonic wave number can be efficiently cleaned.
[0010]
The current detected by the current detector 23 from the output of the matching circuit 10 is input to the first impedance converter 15 of the power measurement circuit 14, and the detection voltage detected from the output of the matching circuit 10 is the power measurement circuit 14. The voltage is input to the voltage divider 16, and the voltage is appropriately divided, converted into a predetermined voltage, and input to the second impedance converter 17. The outputs of the first and second impedance converters 15 and 17 are multiplied. Only the low frequency component is passed through the low-pass filter 19, amplified by the DC amplifier 20, input to the negative terminal of the negative feedback circuit 21, and the reference voltage from the reference power supply 22 is the negative feedback circuit 21. The pulse width of the pulse input to the pulse width control circuit 8 is controlled by the output of the negative feedback circuit 21.
[0011]
In this embodiment, since the first and second phase-locked loop circuits 4 and 5 are inserted in the positive feedback circuit in this way, the oscillation condition is a frequency at which the total loop phase of the oscillation circuit becomes 0 °. The merit of using the first and second phase-locked loop circuits 4 and 5 is that it has a function as an ideal pand-pass filter that suppresses oscillation at an unnecessary sub-resonance. As described above, since the dedicated voltage controlled oscillation circuit is provided, there is an effect that oscillation does not stop depending on the load condition.
[0012]
In the power measuring circuit 14, the multiplier 18 is used to multiply the instantaneous values of the voltage v and current i input to the vibrator 11 by the outputs of the first and second impedance converters 15 and 17, and use them. After passing through a low-pass filter 19 whose cutoff frequency is set sufficiently low with respect to the frequency, a voltage component proportional to the active power is taken out by the DC amplifier 20, which is applied to multi-frequency power measurement that is switched at high speed. In this case, since the measurement responsiveness becomes a problem, the cut-off frequency of the normal low-pass filter is set to several tens of Hz, but this low-pass filter 19 is switched at high speed (several tens to several hundreds Hz). A high cutoff frequency of several hundred Hz to several kHz is set so that the power measurement value can follow.
[0013]
FIG. 2 is a block diagram of the first and second phase-locked loop circuits 4 and 5 used in the oscillation control circuit 1 of the present invention shown in FIG. 1. The outputs of the first and second phase shifters 2 and 3 are A phase comparison circuit 24 is connected to an input terminal 23 to be inputted, an output of the phase comparison circuit 24 is inputted to a loop pass filter 25, an output of the loop pass filter 25 is inputted to one terminal of an analog switch 26, and the other terminal. Is connected to a frequency setting power source 27 for generating a frequency setting voltage V (f0 + Δf), the analog switch 26 is alternately switched in output by a clock 28, and the output of the analog switch 26 is input to a voltage controlled oscillation circuit 29. 1 is applied from the output oscillation output terminal 30 of the control oscillation circuit 29 to the data selector 6 in FIG.
[0014]
In the phase lock loop circuit configured as described above, the frequency setting voltage V from the frequency setting power source 27 in which the free-running frequency of the voltage control circuit is forcibly switched by the analog switch 26 before the phase lock loop enters the frequency tracking operation. Oscillation is generated near the resonance frequency f0 + Δf set by (f0 + Δf), and thus the frequency tracking operation starts from a location that is relatively close to resonance. Therefore, the tracking speed of the resonance frequency f0 by the loop filter feedback voltage V (f0) is increased, In addition, even if there is a sub-resonance near the resonance, it can be avoided and stable tracking can be performed.
[0015]
FIG. 3 is a block diagram of an oscillation control circuit according to another embodiment of the present invention, in which 9 is a switching power amplifier, 10 is a matching circuit, 11 is a vibrator, 14 is a power measurement circuit, 21 is a negative feedback circuit, and 22 is The reference power source 23 is a current detector, and since the configuration thereof is the same as that in the above embodiment, the description thereof will be omitted. In this embodiment, the output of the original oscillator 31 is sent to the integrating circuit 33 of the pulse width control circuit 32. The output of the integration circuit 33 is input to the window comparator 34, the output of the window comparator 34 is input to the switching power amplifier 9, the output of the switching power amplifier 9 is input to the matching circuit 10, and the output of the matching circuit 10 is Further, the current i output from the matching circuit 10 is detected by the current detector 23 and input to the power measurement circuit 14. The output voltage v of the matching circuit 10 is input to the power measurement circuit 14, the output of the power measurement circuit 14 is input to the negative terminal of the negative feedback circuit 21, the reference power supply 22 is connected to the positive terminal of the negative feedback circuit, and the negative feedback The output of the circuit 21 is input to the window comparator 34 of the pulse width control circuit 32.
[0016]
In the oscillation control circuit of this embodiment configured as described above, as shown in FIG. 4, the original oscillation signal A from the original oscillator 31 is converted into a triangular wave B by the integration circuit 33 of the pulse width control circuit 32, and the window comparator 34, the triangular wave B and the output voltage V0 of the negative feedback circuit 21 are compared to obtain pulses C and D. When the output power of the matching circuit 10 is low, the pulse is generated by increasing the output voltage V0 of the negative feedback circuit 21. When the pulse widths of C and D are widened and the output power of the matching circuit 10 is low, the reverse operation is performed to control the output power of the matching circuit 10 constant.
[0017]
In this embodiment, since the output power can be variably controlled instantaneously by using the circuit for controlling the pulse width of the original oscillation signal A of the original oscillation circuit 31 in this way, real-time constant power control is possible. Since the window comparator 34 is used, there is an advantage that the power can be varied from 0 to max.
[0018]
Since the present invention is configured as described above, a constant cleaning effect can be expected for any load fluctuation, the destruction of the vibrator and the diaphragm can be prevented, and further, the power element of the oscillator can be prevented. Destruction can be prevented.
[0019]
In the above-described embodiment, the two-frequency oscillation control circuit has been described. However, it is possible to configure a multi-frequency oscillation control circuit having two or more frequencies by increasing the first and second circuits by a desired number. it can.
[0020]
【The invention's effect】
As described above, in the oscillation control circuit of the multi-frequency ultrasonic cleaning machine of the present invention, by using a plurality of mechanical resonances existing in one vibrator, each resonance frequency is alternately switched at a high speed, Since the standing wave is moved, it is possible to expect a certain cleaning effect by reducing the unevenness of cleaning for any load fluctuation, reducing the damage to the object to be cleaned, and the power element of the oscillator There is an advantage that the destruction of the vibrator and the diaphragm can be prevented, and the life of the vibrator can be extended.
[Brief description of the drawings]
FIG. 1 is a block diagram of an oscillation control circuit of a multi-frequency ultrasonic cleaner according to an embodiment of the present invention.
2 is a block diagram of a phase-locked loop circuit of the oscillation control circuit of FIG.
FIG. 3 is a block diagram of an oscillation control circuit of a multi-frequency ultrasonic cleaner according to another embodiment of the present invention.
4 is a waveform diagram of each part in FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Frequency control circuit 2 1st phase shifter 3 2nd phase shifter 4 1st phase lock loop circuit 5 2nd phase lock loop circuit 6 Clock 7 Data selector 8 Pulse width control circuit 9 Switching power amplifier 10 Matching circuit 11 Vibrator 12 Liquid 13 Washing tank 14 Power measurement circuit 15 First impedance converter 16 Voltage divider 17 Second impedance converter 18 Multiplier 19 Low-pass filter 20 DC amplifier 21 Negative feedback circuit 22 Reference power supply 23 Current detector

Claims (3)

At least two phase shifters that change the phase of the output current input to the vibrator mounted in the cleaning tank, at least two phase-locked loop circuits that lock the phase of the output of the phase shifter, and the two phase locks A frequency control circuit comprising a data selector for alternately selecting output data of the loop circuit with a clock, a pulse width control circuit for controlling the pulse width of the output of the data selector, and switching for amplifying the output of the pulse width control circuit A power amplifier, a matching circuit for matching alternate outputs of the switching power amplifier, a current detection element for detecting an output current of the matching circuit, and a first circuit for converting the output current detected by the current detection element into an impedance. 1 impedance converter, a voltage divider that divides the voltage input to the vibrator, and the divided voltage A second impedance converter for converting to impedance, a multiplier for multiplying the outputs of the first impedance converter and the second impedance converter, a low-pass filter for passing a low frequency of the output of the multiplier, and the low-pass A power measuring circuit comprising a DC amplifier for amplifying the output of the filter, and a negative feedback circuit for inputting the output of the DC amplifier of the power measuring circuit to the negative terminal and inputting a reference voltage for power control to the positive terminal, An oscillation control circuit for a multi-frequency ultrasonic cleaner, wherein the output of the negative feedback circuit is input to the pulse width control circuit, the power input to the vibrator is controlled, and the frequency is automatically tracked. The phase-locked loop circuit includes a phase comparator that compares the phase of the signal from the phase shifter, a loop filter that passes through a loop of the output of the phase comparator, and an output voltage and a set voltage of the loop filter by a clock. 2. The oscillation control circuit for a multi-frequency ultrasonic cleaner according to claim 1, comprising an analog switch that switches alternately and a voltage-controlled oscillation circuit that oscillates with an input voltage. The pulse width control circuit includes an integration circuit and a window comparator, and an output of the frequency control circuit is input to the integration circuit, and an output of the negative feedback circuit is input to the window comparator. An oscillation control circuit for a multi-frequency ultrasonic cleaner according to Item 1.

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