JP6019379B1 - Pulse isolator using piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit an input side pulse signal received from the outside from a primary side to a secondary side using a piezoelectric transformer, and to generate and output an output side pulse signal having the same waveform insulated from the input side pulse signal. A drive control circuit unit 11 that outputs a pulse signal output from an input buffer unit 11a and a pulse output of a multivibrator 11b as a logic circuit, and an AC voltage having a predetermined frequency at a subsequent stage via a resonance inductor L. Switching circuit unit 12 that outputs the AC voltage, piezoelectric transformer unit 13 that receives the AC voltage output from the switching circuit unit 12 and outputs the AC voltage, and rectifies, smoothes, and rectangularizes the output voltage and outputs the output side to the subsequent stage. And a waveform shaping circuit unit 14 that outputs a pulse signal Sout. [Selection] Figure 1

Description

  The present invention relates to a pulse isolator using a piezoelectric transformer that receives a pulse signal from outside and generates and outputs a pulse signal having the same waveform insulated from the pulse signal.

  Conventionally, a pulse isolator (also referred to as a signal isolator in the instrumentation field) that receives a pulse signal from the outside and transmits a pulse signal having the same waveform by isolating the input and output (for example, patents) Reference 1).

  The configuration of the pulse isolator will be described with reference to FIG.

  A flip-flop circuit 207 is provided, and a voltage signal VA generated at one end of the secondary winding CL2 of the pulse transformer PT is generated at the other end of the secondary winding CL2 of the pulse transformer PT to the set terminal S of the flip-flop circuit 207. The voltage signal VB is applied to the reset terminal R of the flip-flop circuit 207.

  Further, a resistor R3 for limiting current is provided on the primary side of the pulse transformer PT, and a resistor R4 for suppressing ringing is provided on the secondary side of the pulse transformer PT.

  Further, the middle point of the secondary winding CL2 of the pulse transformer PT is connected to the terminal P11, and the output pulse signal Pout is obtained between the terminals P10 and P11.

  Here, the flip-flop circuit 207 is a well-known RS flip-flop circuit, and is composed of NOR circuits NOR1 and NOR2. Its Q output terminal is connected to the terminal P10.

  In this pulse isolator, when the pulse signal Pin is input to the terminal P9, the pulse signal Pin is push-pulled to the primary winding CL1 of the pulse transformer PT via the buffer 204 and the inverter 205, and this primary winding. A voltage is induced at one end and the other end of the secondary winding CL2 of the pulse transformer PT by the pulse signal Pin input to the line CL1.

  With such a configuration, the flip-flop circuit is set by the first voltage signal generated at one end of the secondary winding rising at the rising edge of the input pulse signal, and the other end of the secondary winding rising at the falling edge of the input pulse signal. The flip-flop circuit is reset by the second voltage signal generated at the time.

  That is, an output pulse signal that rises at the rising edge of the input pulse signal and falls at the falling edge of the input pulse signal can be obtained from the flip-flop circuit.

  As a result, the pulse transformer PT can be used to transmit a wide range of pulse signals from low frequency (for example, about 0.00001 Hz) to high frequency (for example, about 100 MHz) with the input and output insulated.

  In addition, a pulse transformer having a narrower band than the frequency band of the pulse signal to be transmitted, a drive circuit for supplying a current corresponding to the pulse signal to the primary side of the pulse transformer, and a secondary side of the pulse transformer Also known is a rectifier circuit, a flip-flop connected to the output terminal of the rectifier circuit, a delay circuit connected to the output terminal of the flip-flop, and a configuration in which the input of the flip-flop is masked by the output of the delay circuit (For example, refer to Patent Document 2).

  On the other hand, a commercial AC input (for example, AC 100 V / 50 Hz) is rectified and smoothed to be converted into a DC voltage, further converted into a high-frequency AC voltage by a switching circuit, insulated and transformed by a piezoelectric transformer, and then a rectifying and smoothing circuit. There is also known a piezoelectric transformer converter that outputs a voltage to a load after being converted to a constant voltage direct current (see, for example, Patent Document 3 and Patent Document 4).

  In this piezoelectric transformer converter, the output voltage output to the load is controlled by controlling the voltage frequency converter (VCO) based on the comparison result between the output voltage and the reference voltage by the error amplifier, and the drive frequency of the switching circuit is controlled. It was kept at a constant voltage by controlling.

  A DC / DC converter using a piezoelectric transformer that can output a desired DC output voltage from a DC input voltage using a piezoelectric transformer and switch means is also known (see, for example, Patent Document 5 and Patent Document 6). .

  There has also been known a constant voltage / constant frequency generator provided with a high frequency oscillator that converts a DC input voltage into a high frequency by the output of a pair of piezoelectric transformers and an error amplifier (see, for example, Patent Document 7).

  Furthermore, a power transmission system capable of transmitting power by using an inverter circuit and a piezoelectric transformer as a DC power source has been known (see, for example, Patent Document 8).

  In this power transmission system, an inverter circuit is connected to a DC power source, and the inverter circuit is switching-controlled by a control circuit.

  JP 2001-111390 A   Japanese Utility Model Publication No. 61-176823   JP 2000-341939 A   JP-A-10-262369   JP 11-55941 A   JP-A-4-210773   JP-A-6-86552   Japanese Patent Laying-Open No. 2015-156741

  However, in the conventional pulse isolator described above, the pulse transformer PT has a function of inputting a rising pulse and a falling pulse to the flip-flop circuit 207 (only a signal that changes transiently due to magnetic coupling from the primary side to the secondary side). In order to obtain an output pulse signal Pout corresponding to the input pulse signal Pin, the power supply for driving the flip-flop circuit 207 is used. In addition, it was necessary to separately supply new power from another power supply terminal.

  In addition, by using the pulse transformer PT, radio noise (external noise) is superimposed on the transmitted pulse signal depending on the noise environment where the conventional signal insulation circuit is installed, causing set / reset malfunctions. However, a signal unrelated to the input signal may be output.

  Furthermore, the core, bobbin, winding, insulating tape, margin tape, and other elements are essential for the pulse transformer PT, and further, the insulation distance (spatial distance and creepage distance) between windings and winding terminals. It was necessary to secure enough.

  Solving these problems has also caused an increase in the size of the entire signal insulation circuit, a complicated circuit configuration, and an increase in cost.

  On the other hand, when the converter or transmission system using the piezoelectric transformer described above is intended to output a desired voltage using a piezoelectric transformer with respect to a predetermined voltage input such as a DC voltage generator or a commercial AC voltage, It is known to convert the primary side input voltage of a piezoelectric transformer to a high frequency using a switching circuit, for example, an LC resonance circuit.

  However, the object to be controlled by the switching circuit is the DC output voltage value after the secondary side AC voltage of the piezoelectric transformer is smoothed, and the purpose / function of controlling the value to a predetermined range in advance ( This function reduces the error between the target value and the actual value), so it does not have a function to receive a pulse signal from the outside and generate and output a pulse signal with the same waveform that is insulated from the pulse signal. It was.

  In other words, for the purpose of receiving a pulse signal from the outside, generating and outputting a pulse signal having the same waveform insulated from the pulse signal, the technical purpose / function itself is significantly different from that of the conventional one. I could not do it.

  The present invention solves the above-described problems, and provides a pulse isolator using a piezoelectric transformer that receives a pulse signal from the outside and generates and outputs a pulse signal having the same waveform insulated from the pulse signal. For the purpose.

  According to the pulse isolator using the piezoelectric transformer according to the present invention, when the input side pulse signal is received from the outside, the output side pulse signal having the same waveform as the input side pulse signal is generated and output. An input buffer unit to which an input side pulse signal is input; a pulse control signal output from the input buffer unit; and a drive control circuit unit that outputs a pulse output of the multivibrator; A switching circuit unit that is driven by an output signal of the drive control circuit unit and outputs an AC voltage of a predetermined frequency to the subsequent stage via the resonance inductor, and an AC voltage output from the switching circuit unit is a primary side input voltage. , Piezoelectric transformer part that outputs AC voltage to the secondary side, and secondary side output voltage output from the piezoelectric transformer part Smooth, and is characterized in that it comprises a waveform shaping circuit for outputting the output pulse signal to the subsequent stage by the squaring, the.

  That is, in the piezoelectric transformer section which is a main component of the pulse isolator using the piezoelectric transformer according to the present invention, the applied electric energy forcibly deforms, for example, a ceramic rectangular plate by the reverse piezoelectric effect on the primary side. The elastic energy is converted into such elastic energy, and the elastic energy has an inherent property that it becomes electric energy again by the piezoelectric effect on the secondary side.

  As a result, since electrical energy conversion is performed through elastic vibration, immunity of pulse isolators using conventional pulse transformers (in the field of EMC, electrical devices are exposed to electrical stress (electric field, magnetic field, voltage, current)). Overcoming the weakness of the ability to withstand)

  This performance is also referred to as Electromagnetic Susceptibility.

  In addition, electrical devices are exposed to various electrical stresses depending on the use environment, and electrical stress includes radio waves for radio communication and public broadcasting in addition to those generated from electrical devices.

  For example, electrical stress due to natural phenomena such as lightning and static electricity is also covered, and as with emissions, all electrical equipment must have the immunity required to prevent electromagnetic interference from occurring. The ability can be greatly improved by using a transformer.

  As a result, wireless noise (external noise) is superimposed on the transmission signal without being dependent on the noise environment of the place where the pulse isolator using the piezoelectric transformer according to the present invention is installed. The occurrence of a reset malfunction or the output of a signal unrelated to the input signal is greatly reduced.

  In addition, a pulse isolator using a conventional pulse transformer receives, for example, a pulse signal of 10 kHz (on duty ratio 50%) at a peak value of 5 V, and transmits from 0.1 W to 0.15 W from the primary side to the secondary side. What can only be achieved is a pulse isolator using a piezoelectric transformer according to the present invention, which enables transmission of 0.5 to 1.0 W from the primary side to the secondary side (secondary power input to the primary side). The ratio of the secondary output power (power transmission efficiency) is 80% to 99%).

  As a result, the pulse isolator using the piezoelectric transformer according to the present invention only needs to input the pulse signal from the outside and the DC power supply. It is not necessary to separately supply power as a driving power source for a logic IC, a buffer circuit, or the like constituting the unit.

  In addition, elements such as cores, bobbins, windings, insulating tapes, margin tapes, etc., which are essential for pulse transformers, are no longer required, and have been conventionally required between windings and between winding terminals. It is not necessary to secure an insulation distance (clearance distance and creepage distance).

  That is, by using a piezoelectric transformer, the problems associated with the conventional pulse transformer can be solved, so that the overall size and size of the pulse isolator can be reduced, the circuit configuration can be simplified, and the cost can be reduced.

  Further, according to the pulse isolator using the piezoelectric transformer according to the present invention, the DC voltage after rectifying and smoothing the secondary output voltage output from the piezoelectric transformer unit is used as a driving power source for the waveform shaping circuit unit. You may supply.

  As a result, it is not necessary to provide another power supply terminal as a driving power supply, and accordingly, the wiring path from the power supply side is reduced, and radio noise (external noise) from another power supply side is reduced. Since intrusion and signal superimposition can be significantly suppressed, the occurrence of malfunctions of the input buffer unit, logic IC, buffer, or the like is suppressed, and the possibility that a signal unrelated to the input signal is output is also greatly reduced.

  According to the pulse isolator using the piezoelectric transformer according to the present invention, the drive control circuit unit outputs the pulse signal output from the input buffer unit and the pulse output of the multivibrator as a logic circuit, and the switching circuit. ON / OFF switching control may be performed so that the two switching elements included in the unit have opposite logics (inverted with respect to each other).

  As a result, the two switching elements of the switching circuit section are reversed in logic (inverted with respect to each other), so that the supply and release of the DC voltage to the primary terminal of the piezoelectric transformer section via the resonance inductor (the primary terminals are connected to each other). Therefore, an alternating current corresponding to the oscillation frequency of the multivibrator can be generated on the primary side of the piezoelectric transformer unit.

  Further, according to the pulse isolator using the piezoelectric transformer according to the present invention, the drive control circuit unit outputs a logical product output of the pulse signal output from the input buffer unit and the pulse output Q of the multivibrator. When the signal is output as a driving signal for the first part, the switching circuit part includes two switching elements, one P-channel type FET is connected to a positive power source, and the other N-channel type FET is connected to a negative power source. The product output may be the gate input of each FET.

  Thereby, a pulse isolator in which a known and simple technique is applied to a part of the entire configuration can be provided.

  Further, according to the pulse isolator using the piezoelectric transformer according to the present invention, the drive control circuit unit includes a first logical product output of the pulse signal output from the input buffer unit and the pulse output Q of the multivibrator. When the second logical product output of the pulse signal and the pulse output NotQ of the multivibrator is output as a drive signal for the switching circuit unit, the switching circuit unit includes two switching elements, which are either a positive power source or a negative power source. Also, an N-channel FET may be connected, and the first AND output may be the gate input of one N-channel FET and the second AND output may be the gate input of the other N-channel FET.

  Thereby, a pulse isolator in which a known and simple technique is applied to a part of the entire configuration can be provided.

  A pulse isolator using a piezoelectric transformer according to the present invention can receive a pulse signal from the outside, and generate and output a pulse signal having the same waveform insulated from the pulse signal.

1 is a schematic overall configuration diagram of a pulse isolator using a piezoelectric transformer and a site side (measurement pulse signal transmission system) connected to the pulse isolator in an embodiment of the present invention. FIG. 1 is a configuration diagram of a previous stage of a pulse isolator using a piezoelectric transformer in an embodiment of the present invention. FIG. 3 is a configuration diagram of the latter part of a pulse isolator using a piezoelectric transformer in the embodiment of the present invention. (A)-(d) Timing chart in case of different pulse frequency in pulse isolator using piezoelectric transformer in embodiment of this invention. (A)-(d) Timing chart in case of different on-duty ratio in pulse isolator using piezoelectric transformer in embodiment of this invention. (A) Relationship diagram between frequency of input side pulse signal and output side pulse signal, (b) Relationship diagram between on duty ratio of input side pulse signal and on duty cycle of output side pulse signal FIG. 6 is a configuration diagram of the rear stage of a pulse isolator using a piezoelectric transformer in a modification of the embodiment of the present invention. Circuit diagram of conventional pulse isolator

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic overall configuration diagram of a pulse isolator using a piezoelectric transformer and a site side (measurement signal transmission system) connected thereto in an embodiment of the present invention, and FIG. 2 is an embodiment of the present invention. FIG. 3 is a block diagram of the former stage of a pulse isolator using a piezoelectric transformer, and FIG. 3 is a block diagram of the latter stage of a pulse isolator using a piezoelectric transformer in the embodiment of the present invention. These are timing charts in the case of different pulse frequencies in the pulse isolator using the piezoelectric transformer in the embodiment of the present invention, and FIGS. 5A to 5D show the piezoelectric transformer in the embodiment of the present invention. FIG. 6A is a timing chart in the case of different on-duty ratios in the used pulse isolator. FIG. 6A shows the frequency of the input side pulse signal and the output side pulse. FIG. 6B is a relationship diagram between the on-duty ratio of the input-side pulse signal and the on-duty ratio of the output-side pulse signal, and FIG. 7 is a diagram of the embodiment of the present invention. It is a back | latter stage part block diagram using the piezoelectric isolator in one modification.

  In FIG. 1, for example, 0 V (L level) / L, based on the measurement result of instantaneous flow rate and integrated flow rate combined with an external positive displacement type or impeller type flow meter, or measurement of speed and movement distance combined with an encoder. Piezoelectric wave that can be received via a pulse transmitter PD on the site side that transmits a 5V (H level) input side pulse signal Sin and a pair of transmission lines L1 and L2 (for example, twisted pair wires, shielded wires, coaxial cables, etc.) 1 is a schematic overall configuration diagram on the monitoring / control device side, such as a pulse isolator 10 using a transformer, and a pulse analog converter and a pulse integrating analog converter (not shown) connected to the subsequent stage.

  Here, the pulse transmission unit PD uses the voltage pulse signal output or the open collector output to input the input side pulse signal Sin (for example, the peak value is 5V, 10V, or 15V based on the measurement result described above). , A pulse transformer having a pulse frequency of 0.01 Hz to 50 kHz and an on-duty ratio of 1% to 99% in a typical range) is connected via a pair of transmission lines L1 and L2 to a piezoelectric transformer. This is a device having a conventional function of transmitting to the used pulse isolator 10.

  Further, the pulse isolator 10 using a piezoelectric transformer once outputs the input side pulse signal Sin, and outputs the output side pulse signal Sout having the same waveform as that between the site side and the other monitoring / control device side. It has a function of transmitting a pulse signal having the same waveform as the received pulse signal to a subsequent monitoring / controlling device (not shown) while ensuring insulation.

  The pulse isolator 10 using a piezoelectric transformer according to the embodiment of the present invention has an input terminal T1 and an input terminal T2 as connection terminals for the pair of transmission lines L1 and L2.

  Here, the input side pulse signal Sin is input to the input buffer unit 11a via the input terminal T1 connected to the transmission line L1, and the input terminal T2 connected to the transmission line L2 is internally driven via the terminal t1. It is connected to a negative power source (-) supply circuit of the control circuit unit 11 (see FIGS. 4A and 5A).

  The drive control circuit unit 11 outputs the pulse signal output from the input buffer unit 11a and the pulse output of the multivibrator 11b as a logic circuit.

  Here, the input buffer unit 11a is connected to an input terminal T3 for connection to an external power supply and is supplied with a positive power supply (+).

  The input buffer unit 11a is connected to an input terminal T4 for connection to an external power supply via a terminal t1 and is supplied with a negative power supply (−).

  An input terminal T4 for connection between the input terminal T2 and an external power source is internally connected via a terminal t1 and a terminal t2, both of which are COM terminals (common potential terminals) of the pulse isolator 10 using a piezoelectric transformer. It is connected to the.

  With the circuit connection as described above, the input buffer unit 11a can supply, for example, 5V to the output stage of the input buffer unit 11a depending on whether the input side pulse signal Sin input from the input terminal T1 is higher or lower than a predetermined threshold voltage. A voltage corresponding to a logical value of either (H level) or 0 V (L level) is output.

  As a result, a pull-up resistor is temporarily set from the receiving side due to the influence of wiring resistance and capacitance (for example, about 50 pF / m in the case of a twisted pair wire) that increases when the length of the pair of transmission lines L1 and L2 is long. Even if a voltage drop (attenuation of the signal waveform) occurs in the input side pulse signal Sin transmitted from the open collector output of the pulse transmission unit PD, an error is input through the input buffer unit 11a. Can be prevented.

  The pulse signal output from the input buffer unit 11a is input to the AND gate 11c and the AND gate 11d via the terminal t5. Similarly, the pulse output Q of the multivibrator 11b is input to the AND gate 11c via the terminal t6. And the AND gate 11d.

  Here, for example, a model “CD4047B Types” manufactured by TEXAS INSTRUMENTS may be used as the multivibrator 11b.

  The logical product output, which is an output signal of one AND gate 11c, is input to the gate terminal (gate input) as a drive signal for the P-channel FET 12a connected to the positive power source (+) via the terminals t3 and t4. Is done.

  The logical product output, which is the output signal of the other AND gate 11d, is input to the gate terminal (gate input) as a drive signal for the N-channel FET 12b connected to the negative power source (−) via the terminals t7 and t9. Is done.

  In this way, ON / OFF switching control is performed so that the two switching elements (P-channel FET 12a and N-channel FET 12b) constituting the switching circuit unit 12 are reversed in logic (inverted with respect to each other).

  Here, as a driving power source for the multivibrator 11b, a positive power source (+) is supplied to the power source terminal Vdd via the terminal t3 and the terminal t4, and a negative power source (−) is supplied to the GND terminal via the terminal t7.

  Further, although not shown for the AND gate 11c and the AND gate 11d, a positive power source (+) and a negative power source (−) are supplied to the respective logic ICs as driving power sources.

  In this way, even when input side pulse signals having different peak values, pulse frequencies, or on-duty ratios are input, the two switching elements 12a and 12b are reversed in the time domain in which the input side pulse signal is at the H level. ON / OFF switching control is performed so as to be (reciprocal to each other).

  As a result, the supply and release of the DC voltage (short circuit between the terminal t8 and the terminal t9) are alternately performed with respect to the primary side terminal of the piezoelectric transformer section 13 via the resonance inductor L, and therefore the oscillation frequency of the multivibrator 11b. The alternating current according to can be generated on the primary side of the piezoelectric transformer section 13.

  That is, according to the pulse output of the multivibrator 11b, it is determined by the inductance of the resonance inductor L and the internal equivalent circuit between the primary side terminals of the piezoelectric transformer section 13 (between the primary side terminal 13a and the primary side terminal 13b). An AC voltage having a predetermined high frequency (for example, a resonance frequency of 140 kHz) is generated and output as the primary side input voltage of the piezoelectric transformer section 13 (see FIGS. 4B and 5B).

  On the other hand, in the time region where the pulse signal output from the drive control circuit unit 11 is at the L level, ON / OFF switching control is performed such that the two switching elements 12a and 12b are reversed in logic (inverted with respect to each other). Therefore, the AC voltage having the predetermined high frequency (for example, the resonance frequency is 140 kHz) is not generated (see FIGS. 4B and 5B).

  In this way, when the pulse signal output from the input buffer unit 11a is at the H level, an AC voltage signal is input to the primary side terminals (13a, 13b) of the piezoelectric transformer unit 13, and thus the piezoelectric transformer unit 13 The secondary side terminals (13c, 13d) are subjected to electrical energy conversion (electromagnetically insulated) from the primary side terminals (13a, 13b) via elastic vibrations, and output secondary side output voltages.

  And the signal of the secondary side output voltage output from the secondary side terminals (13c, 13d) of the piezoelectric transformer unit 13 is connected to the diode bridge 14a and the diode bridge via the terminal t10 and the terminal t11 of the waveform shaping circuit unit 14. 14c is input in parallel to each input side.

  Here, the signal subjected to full-wave rectification by the diode bridge 14a is smoothed through an RC smoothing circuit including a resistor R1 and a capacitor C1 connected between the terminal t14 and the terminal t15, and the terminal t14. (See FIGS. 4C and 5C).

  Then, the smoothed signal is rectangularized (pulse shaped) to become a pulse signal through the buffer 14b, and then an output side pulse signal Sout is output from the output terminal T5 (FIG. 4D). ), FIG. 5 (d)).

  On the other hand, the output voltage between the secondary terminals (13c, 13d) output from the piezoelectric transformer unit 13 is full-wave rectified by the diode bridge 14c, and is connected by the capacitor C2 connected between the terminal t12 and the terminal t13. Smoothed and supplied as a driving power source for the buffer 14b, that is, a positive power source (+).

  As a result, only the pulse signal from the outside (between the input terminal T1 and the input terminal T2) and the DC power supply (between the input terminal T3 and the input terminal T4) are input to the pulse isolator 10 using a piezoelectric transformer. The secondary circuit itself may be provided with a separate power source, and there is an effect that it is not necessary to separately supply power as a driving power source for a logic IC or the like that forms part of the circuit.

  Next, the case where the pulse frequency of the input side pulse signal Sin is 10 kHz and the case of 20 kHz will be described with reference to FIGS.

  FIG. 4A shows the respective signal waveforms when the pulse frequency of the input side pulse signal Sin is 10 kHz and 20 kHz.

  Here, if the pulse frequency is 10 kHz, the pulse period Ta is 0.1 msec, and if the pulse frequency is 20 kHz, the pulse period Tb is 0.05 msec.

  Next, FIG. 4B shows a case where the input side pulse signal Sin has a predetermined high frequency (for example, in the time region where the input side pulse signal Sin is at the H level in each case where the pulse frequency of the input side pulse signal Sin is 10 kHz and 20 kHz. A signal waveform in which an AC voltage having a resonance frequency of 140 kHz is generated and an AC voltage having a predetermined high frequency (for example, the resonance frequency is 140 kHz) is not generated in a time region where the input side pulse signal Sin is at the L level. That is, the signal waveform inputted as the primary side input voltage of the piezoelectric transformer section 13 is shown.

  FIG. 4C shows the secondary output from the secondary terminal (13c, 13d) of the piezoelectric transformer section 13 when the pulse frequency of the input side pulse signal Sin is 10 kHz and 20 kHz, respectively. The signal of the side output voltage is full-wave rectified by the diode bridge 14a of the waveform shaping circuit unit 14, and smoothed through an RC smoothing circuit including a resistor R1 and a capacitor C1 between the terminal t14 and the terminal t15. The signal waveform is shown.

  Further, FIG. 4D shows that the above-mentioned smoothed signal becomes a pulse signal through the buffer 14b in each of the cases where the pulse frequency of the input side pulse signal Sin is 10 kHz and 20 kHz. The signal waveform of the output side pulse signal Sout output from the output terminal T5 after being rectangularized (pulse shaping) is shown.

  As described above, even when a plurality of input side pulse signals having different pulse frequencies are input from the outside, an output side pulse signal having the same waveform (same frequency) insulated from the pulse signal can be generated and output. it can.

  Next, a case where the on-duty ratio of the input side pulse signal Sin is 40% and a case where it is 80% will be described with reference to FIGS.

  FIG. 5A shows the case where the input side pulse signal Sin has a pulse period T (pulse frequency is 1 / T) and its on-duty ratio is 40% (pulse width ta / pulse period T is 40%). Each signal waveform in the case of 80% (pulse width tb / pulse period T is 80%) is shown.

  Next, FIG. 5B shows a predetermined high level in the time region where the input side pulse signal Sin is at the H level in each of the cases where the on-duty ratio of the input side pulse signal Sin is 40% and 80%. An AC voltage having a frequency (for example, a resonance frequency of 140 kHz) is generated, and an AC voltage having a predetermined high frequency (for example, a resonance frequency of 140 kHz) is not generated in a time region where the input side pulse signal Sin is at the L level. That is, a signal waveform input as the primary side input voltage of the piezoelectric transformer section 13 is shown.

  FIG. 5C shows the output from the secondary side terminals (13c, 13d) of the piezoelectric transformer section 13 when the on-duty ratio of the input side pulse signal Sin is 40% and 80%, respectively. The signal of the secondary output voltage is full-wave rectified by the diode bridge 14a of the waveform shaping circuit unit 14, and passes through an RC smoothing circuit including a resistor R1 and a capacitor C1 between the terminal t14 and the terminal t15. 2 shows a smoothed signal waveform.

  Further, FIG. 5D shows that the above smoothed signal passes through the buffer 14b in each of the cases where the on-duty ratio of the input side pulse signal Sin is 40% and 80%. The signal waveform of the output-side pulse signal Sout output from the output terminal T5 after being rectangularized (pulse shaping) to be

  As described above, even if an input side pulse signal with the same pulse frequency and different on-duty ratio is input from the outside, the output side pulse with the same waveform (same on-duty ratio) insulated from that pulse signal A signal can be generated and output.

  Next, the relationship between the frequency of the input side pulse signal and the frequency of the output side pulse signal will be described with reference to FIG.

  As is clear from this figure, in the frequency band of at least 0 Hz to 50 kHz, the frequency of the input side pulse signal Sin and the frequency of the output side pulse signal Sout are substantially the same, and a plurality of pulse signals having different pulse frequencies are externally provided. Even if input, a pulse signal having the same waveform (same frequency) insulated from the pulse signal can be generated and output.

  Further, the relationship between the on-duty ratio of the input-side pulse signal and the on-duty ratio of the output-side pulse signal will be described with reference to FIG.

  As is clear from this figure, the on-duty ratio of the input-side pulse signal Sin and the on-duty ratio of the output-side pulse signal Sout are substantially the same in an on-duty ratio range of at least 1% to 99%. Even if a plurality of pulse signals having different on-duty ratios are input, a pulse signal having the same waveform (same on-duty ratio) insulated from the pulse signals can be generated and output.

  As described above, even if various pulse signals with different pulse frequencies and on-duty ratios are input from outside, a pulse signal having the same waveform (same frequency and same duty ratio) insulated from the pulse signal is generated and output. be able to.

  (One variation)

  Next, with reference to FIG. 7, one modified example of the drive control circuit unit and the switching circuit unit included in the configuration of the previous stage of the pulse isolator 10 using the piezoelectric transformer will be described.

  In this figure, the same reference numerals are used as they are for the same components as those described above, and the same descriptions are also omitted below.

  On the other hand, in the pulse isolator 10 using the piezoelectric transformer according to one modification of the embodiment of the present invention, the input side pulse signal Sin is input to the input buffer unit via the input terminal T1 connected to the transmission line L1. The input terminal T2 input to the transmission line 11a and connected to the transmission line L2 is internally connected to the negative power supply (−) supply circuit of the drive control circuit unit 11 via the terminal t1.

  Further, the drive control circuit unit 111 outputs the pulse signal output from the input buffer unit 11a and the pulse output of the multivibrator 11b as a logic circuit.

  That is, the pulse signal output from the input buffer unit 11a is input to each of the AND gate 11c and the AND gate 11d via the terminal t18, the pulse output Q of the multivibrator 11b is input to the AND gate 11c, and the multivibrator 11b. The pulse output NotQ is input to the AND gate 11d.

  Further, the first AND output, which is the output signal of one AND gate 11c, is input to the gate terminal as a driving signal for the N-channel FET 112a connected to the positive power source (+) via the terminal t3 and the terminal t4 ( Gate input).

  The second logical product output, which is the output signal of the other AND gate 11d, is input to the gate terminal as a drive signal for the N-channel FET 112b connected to the negative power source (−) via the terminal t7 and the terminal t9 ( Gate input).

  In this way, ON / OFF switching control is performed so that the two switching elements (N-channel type FETs 112a and 112b) constituting the switching circuit unit 112 are reversed in logic (inverted with respect to each other).

  Although not shown or described in detail, the AND output of one AND gate 11c is replaced with an N-channel FET 112a connected to a positive power source (+) via terminals t3 and t4. The AND output of the other AND gate 11d is input to the gate terminal of the FET and the N channel FET 112b connected to the negative power source (−) via the terminal t7 and the terminal t9 is replaced with the gate terminal of the P channel type FET. You may enter.

  That is, even if both of the two switching elements are constituted by P-channel FETs, ON / OFF switching control is performed so that the two switching elements are in reverse logic (inverted with respect to each other).

  In any case, the drive control circuit unit may output the logic circuit so that ON / OFF switching control is performed so that the two switching elements constituting the switching circuit unit are reversed in logic (inverted with respect to each other). .

  In addition, the switching element is not limited to a P-channel FET or an N-channel FET, and a transistor, a junction FET, or the like may be selected as appropriate.

  The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. The technical scope disclosed in different embodiments, respectively. Modifications of the embodiment obtained by appropriately combining the means are also included in the technical scope of the present invention.

  For example, in the above-described embodiment, the case where the pulse transmission unit PD is a voltage pulse signal output (0 V or 5 V) has been described. However, if the pulse transmission unit PD is an open collector output, the input buffer unit 11a. A positive power source (+) supplied to the input terminal T1 may be connected to the input terminal T1 via a pull-up resistor having an appropriate resistance value to supply a pull-up voltage.

  In particular, the circuit configuration and circuit constants in the reference circuit diagram are not clearly described in the description of the above-described embodiment and its modifications, as long as the intended purpose of the present invention is achieved and a desired effect is obtained. May be selected as appropriate within the scope of the technical scope of the present invention.

  As described above, the pulse isolator using a piezoelectric transformer according to the present invention can receive a pulse signal from the outside, and generate and output a pulse signal having the same waveform insulated from the pulse signal. Useful as.

DESCRIPTION OF SYMBOLS 10 Pulse isolator using a piezoelectric transformer 11 Drive control circuit part 11a Input buffer part 11b Multivibrator 11c, 11d AND gate 12, 112 Switching circuit part 12a P channel type FET
12b N-channel FET
112a N-channel FET
112b N-channel FET
13 Piezoelectric transformers 13a and 13b Primary terminals 13c and 13d Secondary terminals 14 Waveform shaping circuits 14a and 14c Diode bridge 14b Buffer PD Pulse transmitters L1 and L2 A pair of transmission lines Sin Input pulse signal Sout Output pulse signal T1, T2, T3, T4 Input terminal T5, T6 Output terminal Vdd Power supply terminal GND Ground terminal Q, NotQ Multivibrator pulse output T, Ta, Tb Pulse period ta, tb Pulse width L Resonant inductor C1, C2 Capacitor R1 Resistance t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18 terminals

Claims (5)

A pulse isolator using a piezoelectric transformer that generates and outputs an output side pulse signal having the same waveform as the input side pulse signal when receiving an input side pulse signal from the outside,
An input buffer unit to which the input side pulse signal is input;
A drive control circuit unit that outputs a pulse signal output from the input buffer unit and a pulse output of the multivibrator to a logic circuit;
A switching circuit unit that is driven by an output signal of the drive control circuit unit and outputs an alternating voltage of a predetermined frequency to a subsequent stage via a resonance inductor;
The AC voltage output from the switching circuit unit is used as the primary side input voltage, and the piezoelectric transformer unit that outputs the AC voltage to the secondary side;
A waveform shaping circuit unit that rectifies, smoothes, and rectangularizes the secondary output voltage output from the piezoelectric transformer unit and outputs the output side pulse signal to the subsequent stage; and
A pulse isolator using a piezoelectric transformer. 2. The piezoelectric transformer according to claim 1, wherein a DC voltage after rectifying and smoothing a secondary output voltage output from the piezoelectric transformer unit is supplied as a driving power source for the waveform shaping circuit unit. The pulse isolator used. The drive control circuit section outputs a logic circuit output of the pulse signal output from the input buffer section and the pulse output of the multivibrator, and two switching elements included in the switching circuit section are reversed in logic (mutually 3. The pulse isolator using a piezoelectric transformer according to claim 1, wherein ON / OFF switching control is performed so as to be reversed. When the drive control circuit unit outputs a logical product output of the pulse signal output from the input buffer unit and the pulse output Q of the multivibrator as a drive signal for the switching circuit unit,
The switching circuit unit includes two switching elements, one P-channel type FET is connected to a positive power source, the other N-channel type FET is connected to a negative power source, and the logical product output is a gate of each FET. The pulse isolator using a piezoelectric transformer according to claim 3, wherein the pulse isolator is an input. The drive control circuit unit includes a first AND output of the pulse signal output from the input buffer unit and the pulse output Q of the multivibrator, and the pulse signal and a pulse output NotQ of the multivibrator. When outputting the second logical product output as a driving signal for the switching circuit unit,
The switching circuit unit includes two switching elements, an N-channel FET is connected to both a positive power source and a negative power source, the first AND output is used as a gate input of one N-channel FET, and the first 4. A pulse isolator using a piezoelectric transformer according to claim 3, wherein a 2-logical product output is used as a gate input of the other N-channel FET.

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