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DESCRIPTION JPH07264692

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DESCRIPTION JPH07264692
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
drive device for an ultrasonic transducer used in an ultrasonic cutter, an ultrasonic welder, an
ultrasonic cleaner and the like.
[0002]
2. Description of the Related Art FIG. 2 is a circuit diagram showing a conventional driving
apparatus for an ultrasonic transducer. A description will be given below based on this figure.
[0003]
The drive control device 80 rectifies and smoothes the AC power supply voltage VAC to obtain a
DC voltage VIN, and an oscillation circuit 86 which drives the ultrasonic vibrator 84 by the DC
voltage VOUT obtained by the rectification smoothing circuit 82. And a switch circuit 88 for
applying the DC voltage V.sub.OUT obtained by the rectifying and smoothing circuit 82 to the
oscillation circuit 86 (for example, as described in FIG. 8 of Japanese Patent Application LaidOpen No. 4-317651). A power transformer 90 and a choke coil 92 are interposed between the
oscillation circuit 86 and the ultrasonic transducer 84. The choke coil 92 is for canceling the
capacitive component of the ultrasonic transducer 84.
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[0004]
The rectifying and smoothing circuit 82 includes a rectifying diode bridge 94 and a smoothing
capacitor 96. The rectifying and smoothing circuit 82 receives an AC power supply voltage VAC
and outputs a DC voltage VIN. Since the AC power supply voltage VAC is a commercial power
supply voltage of 100 [V], the DC voltage VIN is about 140 [V]. The oscillation circuit 86 is a
general one that oscillates following a change in the resonant frequency of the ultrasonic
transducer 84 (for example, Japanese Patent Publication No. 52-17412).
[0005]
The switch circuit 88 includes resistors R11, R12, R13, R14, and R15, a capacitor C11,
transistors Tr11 and Tr12, and a push-button manual switch PB. A manual switch PB is
connected between the connection point of the resistors R11 and R12 that divide the DC voltage
VIN and the base of the transistor Tr11. When the manual switch PB is turned on, the transistor
Tr11 is turned on, whereby the transistor Tr12 is turned on to apply the DC voltage VOUT to the
oscillation circuit 86. Here, assuming that the voltage drop between the collector and the emitter
of the transistor Tr12 is VCE, then VOUT = VIN-VCE.
[0006]
However, in the conventional ultrasonic transducer drive apparatus, the fluctuation of the DC
voltage VOUT applied to the oscillation circuit 86 is not particularly considered. Therefore, it is
difficult to keep the output of the ultrasonic transducer 84 constant, because the direct current
voltage V.sub.OUT fluctuates due to the fluctuation of the AC power supply voltage VAC, the
fluctuation of the load of the ultrasonic vibrator 84, and the like.
[0007]
SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide
a driving device capable of stabilizing the operation of an ultrasonic transducer.
[0008]
SUMMARY OF THE INVENTION A driving device for an ultrasonic transducer according to the
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present invention is made to achieve the above object, and it comprises rectifying and smoothing
an AC power supply voltage to obtain a DC voltage. A circuit, a DC voltage stabilization circuit for
stabilizing a DC voltage obtained by the rectification smoothing circuit, and an oscillation circuit
for driving an ultrasonic vibrator by the DC voltage stabilized by the DC voltage stabilization
circuit It is
[0009]
In addition, a manual switch for controlling the driving of the ultrasonic transducer may be
attached to the low voltage portion of the DC voltage stabilization circuit.
In this case, a light emitting diode that emits light by the operation of a manual switch is
provided in the low voltage portion of the direct current voltage stabilization circuit, and the
photoMOS transistor operates the direct current voltage stabilization circuit by turning on light
emission of the light emitting diode. It is good also as what is provided in the high voltage part of
the said DC voltage stabilization circuit.
[0010]
The operation of the drive device according to the present invention is as follows.
The rectifying and smoothing circuit rectifies and smoothes the AC power supply voltage to
obtain a DC voltage. The DC voltage stabilization circuit further stabilizes the DC voltage obtained
by the rectification and smoothing circuit, and then supplies the DC voltage to the oscillation
circuit. Here, even if the AC power supply voltage fluctuates, a constant voltage is always
supplied to the oscillation circuit by the DC voltage stabilization circuit. Therefore, in the
oscillation circuit, stable driving of the ultrasonic transducer is possible.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a circuit diagram showing
an embodiment of a driving apparatus for an ultrasonic transducer according to the present
invention. A description will be given below based on this figure. However, the same parts as
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those in FIG.
[0012]
The ultrasonic transducer drive device 10 according to the present invention stabilizes the DC
voltage VIN obtained by the rectification smoothing circuit 82 which rectifies and smoothes the
AC power supply voltage VAC to obtain the DC voltage VIN, and the rectification smoothing
circuit 82 A DC voltage stabilization circuit 12 and an oscillation circuit 86 for driving the
ultrasonic vibrator 84 by the DC voltage VDC stabilized by the DC voltage stabilization circuit 12
are provided.
[0013]
The low voltage portion of the DC voltage stabilization circuit 12 is provided with a manual
switch PB for controlling the driving of the ultrasonic transducer 84 and a light emitting diode
14 for emitting light by operation of the manual switch PB.
The manual switch PB is a normally open contact that is always urged in an open direction by a
spring (not shown). A photo MOS transistor 16 is provided in the high voltage portion of the DC
voltage stabilization circuit 12. The photo MOS transistor 16 operates by the light emission of
the light emitting diode 14 to operate the DC voltage stabilization circuit 12.
[0014]
The DC voltage stabilization circuit 12 includes the above-described manual switch PB and the
like, resistors R1, R2, R3, R4, R5 and R6, zener diodes D1 and D2, and transistors Tr1 and Tr2. A
DC voltage VDC is applied to the zener diode D2 for reference voltage generation via the resistor
R6. The reference voltage of the Zener diode D2 is applied to the emitter of the transistor Tr2 for
comparison amplification, and the DC voltage VDC divided by the resistors R3, R4 and R5 is
applied to the base. The base of the control transistor Tr1 is connected to the collector of the
transistor Tr2, and a series circuit of the resistor R2 and the source / drain of the photo MOS
transistor 16 is connected between the collector and the base of the transistor Tr1. The
resistance value between the source and the drain of the photo MOS transistor 16 is almost zero
at the on time, and is almost infinite at the off time. The collector of the transistor Tr1 is
connected to the rectifying and smoothing circuit 82, and the emitter of the transistor Tr1 is
connected to the oscillating circuit 86. A series circuit of a resistor R1 and a zener diode D1 is
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connected in parallel to a smoothing capacitor 96, and a series circuit of a manual switch PB and
a light emitting diode 14 is connected in parallel to the zener diode D1.
[0015]
Next, the operation of the drive device 10 will be described.
[0016]
100
The AC power supply voltage VAC of [V] is rectified and smoothed by the rectifying and
smoothing circuit 82 to be a DC voltage VIN of about 140 [V].
Since a DC voltage VIN is applied to a series circuit of the resistor R1 and the zener diode D1, a
zener voltage VD1 of about 12 [V] is generated in the zener diode D1.
[0017]
When the manual switch PB is pressed with a finger, the contact is closed, and the Zener voltage
VD1 is applied to the light emitting diode 14. Then, the light emitting diode 14 emits light, and
the photo MOS transistor 16 conducts. As a result, the transistor Tr1 is turned on, and the DC
voltage VDC is supplied from the DC voltage stabilization circuit 12 to the oscillation circuit 86.
[0018]
The DC voltage stabilization circuit 12 stabilizes the DC voltage VDC as follows. The Zener diode
D2 generates a constant reference voltage VD2 even if the DC voltage VDC slightly fluctuates. On
the other hand, the base-emitter voltage VBE2 of the transistor Tr2 fluctuates with the
fluctuation of the DC voltage VDC. Therefore, the collector-emitter voltage VCE2 of the transistor
Tr2 also fluctuates according to the fluctuation of the DC voltage VDC. That is, when the DC
voltage VDC decreases, the VBE2 also decreases, thereby increasing the collector voltage VC2 of
the transistor Tr2. Then, as a result of the base voltage VB1 of the transistor Tr1 increasing, the
collector-emitter voltage VCE1 of the transistor Tr1 decreases and the DC voltage VDC increases.
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[0019]
Thus, the DC voltage stabilization circuit 12 operates to increase the DC voltage VDC when the
DC voltage VDC decreases. When the DC voltage VDC increases, the reverse operation is
performed. Therefore, DC voltage stabilization circuit 12 can supply constant DC voltage VDC to
oscillation circuit 86 at all times.
[0020]
Further, only the Zener voltage VD1 of at most about 12 [V] or less is applied to both ends of the
manual switch PB. Therefore, there is no possibility that a high voltage is applied to the human
body via the manual switch PB. In addition, the manual switch PB may be of a small and
generally rated voltage DC 30 [V].
[0021]
Furthermore, a voltage of about 140 [V] or more at maximum is applied across the photo MOS
transistor 16. The photo MOS transistor 16 can easily obtain high breakdown voltage
characteristics. Therefore, the photo MOS transistor is smaller and cheaper than the high
withstand voltage relay, the high withstand voltage switching element, and the like having the
same high withstand voltage characteristics. For example, in the case of using a photobipolar
transistor instead of the photoMOS transistor 16, it is difficult to obtain one having high
withstand voltage characteristics of a rated voltage DC 140 [V] or more. Therefore, in practice, a
protective circuit or the like is required, resulting in a very complicated configuration.
[0022]
The photo MOS transistor 16 may be replaced with the manual switch PB. In this case, in
addition to the photo MOS transistor 16, the Zener diode D1, the light emitting diode 14, the
resistor R1 and the like can be omitted. However, the manual switch PB needs to use a large and
expensive switch with a rated voltage of DC 140 [V] or more. In addition, a high voltage may be
applied to the human body via the manual switch PB.
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[0023]
According to the first aspect of the present invention, the following effects can be obtained. By
interposing the DC voltage stabilization circuit between the rectifying and smoothing circuit and
the oscillation circuit, it is possible to always supply a stable DC voltage to the oscillation circuit
even against fluctuations in the AC power supply voltage. Therefore, a constant ultrasound
output can be obtained at all times.
[0024]
The drive device for an ultrasonic transducer according to claim 2 has the following effects in
addition to the above effects. By providing the manual switch in the low voltage part of the DC
voltage stabilization circuit, the possibility of applying a high voltage to the human body through
the manual switch can be eliminated. Moreover, since the manual switch can be made to have a
low rated voltage, downsizing and cost reduction can be achieved.
[0025]
The drive device for an ultrasonic transducer according to claim 3 has the following effects in
addition to the above effects. The photo MOS transistor can easily obtain high breakdown voltage
characteristics. Therefore, by providing the photo MOS transistor in the high voltage part,
complicated parts such as high breakdown voltage relays and high breakdown voltage switching
elements are not required, so that the configuration can be made small and simple.
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