JP2001045071A - Transmission cable drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission cable drive circuit where multiple reflection of a signal is prevented and an optimum waveform of a drive pulse signal is obtained at an end of a transmission cable. SOLUTION: In the transmission cable drive circuit consisting of a drive section 1, an element 2 to be driven, and a transmission cable 3 that is connected between the drive section 1 and the element 2 to be driven and used to transmit a drive signal from the drive section 1, the drive section 1 consists of a timing pulse signal generating circuit 4, a driver circuit 5 having 1st and 2nd output lines 6, 7 that amplify an output signal of the timing pulse signal generating circuit 4, a control circuit 8 controlling either of the output lines of the driver circuit 5 to have a high impedance for a prescribed period, and a waveform correction circuit 9 to which the output lines 6, 7 of the driver circuit 5 are connected. A delay element 12 to delay a drive pulse signal is provided between a waveform correction circuit 9 and the element 2 to be driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable termination in which a signal is transmitted from a drive section to a driven element at a long interval and a transmission cable having a characteristic impedance such as a coaxial cable is used as signal transmission means. The present invention relates to a transmission cable drive circuit that can obtain an optimal waveform in the above.

[0002]

2. Description of the Related Art Conventionally, as a device using a transmission cable such as a coaxial cable as a signal transmission means, for example,
There is an electronic endoscope camera. Such an electronic endoscope camera,
Conventionally, it basically has a configuration as shown in FIG.
That is, a solid-state imaging device 102 such as a CCD, which is a driven device, is disposed in a camera head unit 101 as an imaging unit, and a position separated from the solid-state imaging device 102 by a distance of several meters via a transmission cable 103 having a characteristic impedance. And a camera control unit 104 as an image processing means. A driver circuit 105 for driving the solid-state imaging device 102 and a timing pulse signal generating circuit 106 are provided in the camera control unit 104.

In the electronic endoscope camera configured as described above, the drive pulse signal from the timing pulse signal generation circuit 106 applied from the driver circuit 105 to the solid-state imaging device 102 is applied to both ends of the transmission cable 103, Input impedance of image sensor 102 and driver circuit 10
5 is not matched with the output impedance of No. 5, and the length of the transmission cable 103 is close to the wavelength of the driving pulse signal [1 / (the number of signal wavelengths).
In the above case, there is a drawback that the waveform is disturbed at the input end (the end of the transmission cable 103) of the solid-state imaging device 102 due to the influence of the reflected signal generated at the input end of the solid-state imaging device 102.

For this reason, a method shown in FIG. 16 has been proposed as a solution in Japanese Patent Application Laid-Open No. Sho 64-2622. In other words, the solution is to provide a terminating resistor 107 equal to the characteristic impedance of the transmission cable 103 on the side of the solid-state imaging device 102,
Signal reflection on the side 102 is prevented from occurring, and the drive pulse signal waveform is optimized at the end of the transmission cable 103.

Another solution is disclosed in Japanese Patent Laid-Open No. 62-8 / 1987.
In Japanese Patent No. 4735, as shown in FIG. 17, a cable matching circuit 108 comprising a resistor and a capacitor corresponding to a plurality of types of transmission cable lengths is provided, and the matching circuit 108 is switched by a switch 109 according to the transmission cable length to be used. Thus, a configuration in which the drive pulse signal waveform is optimized at the end of the transmission cable 103 has been proposed.

However, in the conventional example shown in FIG. 16, at the end of the transmission cable 103 (the input end of the solid-state imaging device 102), the termination resistor 107 matches the characteristic impedance of the transmission cable 103. Therefore, the drive pulse signal waveform at the end of the transmission cable 103 is optimal. However, the power consumed by the terminating resistor 107 provided near the solid-state imaging device 102 is large (for example, when the terminating resistor 107 is 50Ω and the driving pulse voltage level is 10Ω).
In the case of V, the power consumption is 1 W or more), so that heat is generated, and this heat causes the temperature of the solid-state imaging device 102 to rise. This increase in temperature may cause a problem in safety, particularly in an electronic endoscope camera used as a medical device, and also in the performance of the system, the characteristics of the solid-state imaging device 102 deteriorate (the noise level increases). Etc.) may occur. When the length of the transmission cable 103 becomes longer, attenuation occurs in a high frequency region of the transmission signal due to a resistance component and a capacitance component as a distribution constant of the transmission cable, and the drive pulse signal waveform at the end of the transmission cable 103 rises and rises. The fall time becomes slow, which may cause a problem that the signal transfer speed of the solid-state image sensor 102 does not satisfy the system specifications.

In the conventional example shown in FIG. 17, for a transmission cable of a fixed length, a cable matching circuit comprising a resistor and a capacitor corresponding to the length of the transmission cable.
With 108, the drive pulse signal waveform can be adjusted, so that the rise and fall speed (steepness) at the end of the transmission cable 103 can be optimized. But,
Since the impedance of the matching circuit viewed from the transmission cable side fluctuates due to the signal frequency component (in the conventional example shown in FIG. 17, the impedance decreases as the frequency increases), transmission of a pulse signal or the like having a harmonic component of the frequency is performed. In, at both ends of the transmission cable 103, no matching is performed.
As a result, a signal may cause multiple reflections at both ends of the transmission cable 103, and the drive pulse signal waveform may not be optimal at the end of the transmission cable 103.

In order to solve such a problem, the present inventor has proposed a transmission cable driving circuit having the following configuration in Japanese Patent Application No. 11-1683. That is,
As shown in the conceptual diagram of FIG. 1, a driving unit 1, a driven element 2 driven by the driving unit 1, and a driving unit 1 connected between the driving unit 1 and the driven element 2, In the transmission cable driving circuit including the transmission cable 3 having the characteristic impedance for electrically transmitting the driving signal output from the transmission cable 3, the driving unit 1 for driving the transmission cable 3 having the characteristic impedance and the driven element 2 includes: ,
A timing pulse signal generation circuit, a driver circuit having first and second output lines for amplifying an output signal of the timing pulse signal generation circuit, and one output line of the driver circuit being fixed; During the period, a control circuit 8 for controlling the impedance to a high impedance and a waveform correction circuit 9 to which the output lines 6 and 7 of the driver circuit 5 are connected are provided.

In the transmission cable driving circuit configured as described above, at the time of rising and falling of the pulse signal output from the timing pulse signal generating circuit 4, the control circuit 8 controls the first operation of the driver circuit 5. The output line 6 and the second output line 7 are controlled so as to be in a conductive state.
During a period other than the falling (signal voltage flat period), the first output line 6 of the driver circuit 5 is made conductive, and the control circuit 8 makes the second output line 7 of the driver circuit 5 non-conductive. The waveform correction circuit 9 connected to the output lines 6 and 7 of the driver circuit 5 causes the transmission cable 3 having the characteristic impedance to rise and fall when the pulse signal rises and falls. By correcting the attenuation of the transmission signal in the high frequency region due to the resistance component and the capacitance component, and correcting the transmission signal to match the characteristic impedance of the transmission cable 3 at the transmission source during the signal voltage flat period of the pulse signal. 3 prevents signal reflection at the transmission source and optimizes the driving pulse signal at the end of the transmission cable 3. Can be made to form is obtained.

Further, in the above-mentioned patent application, as shown in the conceptual diagram of FIG. 2, in the transmission cable driving circuit shown in the conceptual diagram of FIG. A device having a signal delay circuit 10 for delaying an output signal of the timing pulse signal generation circuit 4 between the control terminal of the driver circuit 5 and the control terminal of the driver circuit 5 has been proposed.

In the transmission cable driving circuit having the above-described configuration, the signal delay circuit 10 is configured to control the signal rising and falling signal transmission delay times at the first and second output lines 6 and 7 of the driver circuit 5. Has an effect of suppressing a decrease in the driving capability of the driver circuit 5 when a difference occurs between the output lines 6 and 7 of the driver circuit 5 at the end of the transmission cable 3. The rising and falling waveforms of the drive pulse signal can be optimized.

[0012]

In the transmission cable driving circuit proposed above, signal reflection at the transmission cable transmission source is prevented, and an optimum driving pulse signal waveform can be obtained at the transmission cable termination source. However, if the phase of the driving pulse signal and the signal phase of the reflected wave at the transmission source overlap in opposite phases due to a change in the characteristics of the transmission cable, the driving capability of the driver circuit is reduced, and the transmission cable The rising and falling waveforms of the drive pulse signal at the end may not be optimal.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is intended to prevent signal reflection on a transmission cable and to obtain an optimum drive pulse signal waveform at a terminal end of the transmission cable. At the same time, even when a change in the phase of the reflected wave at the transmission source occurs due to a change in the characteristics of the transmission cable, the phase of the drive pulse signal and the phase of the reflection signal at the transmission source are adjusted to the same phase, and the driving capability of the driver circuit is reduced. It is an object of the present invention to provide a transmission cable drive circuit capable of suppressing the reduction and optimizing the drive pulse signal waveform.

[0014]

According to a first aspect of the present invention, there is provided a driving unit, a driven element driven by the driving unit, a driving unit and the driven element. And a transmission cable having a characteristic impedance for electrically transmitting a driving signal output from the driving unit, the transmission cable having the characteristic impedance and the driven element being driven. A driving circuit having a timing pulse signal generation circuit, a driver circuit having two output lines for amplifying an output signal of the timing pulse signal generation circuit, and one output line of the driver circuit being kept in a high impedance state for a certain period. A control circuit for controlling, a waveform correction circuit to which each output line of the driver circuit is connected,
A delay element provided between the waveform correction circuit and the driven element for delaying a drive pulse signal.

That is, as shown in the conceptual diagram of FIG. 3, in the previously proposed transmission cable driving circuit shown in the conceptual diagram of FIG. 1, a driving circuit is provided between the waveform correction circuit 9 and the driven element 2. It is characterized by including a delay element 12 for delaying a pulse signal output.

In the transmission cable driving circuit configured as described above, signal reflection on the transmission cable is prevented, an optimum drive pulse signal waveform can be obtained at the end of the transmission cable, and characteristics of the transmission cable can be obtained. Even if a change in the phase of the reflected wave at the transmission source occurs due to the change, the delay element 12 causes the phase of the drive pulse signal at the transmission source (waveform correction circuit 9 side) and the reflected signal (due to cable mismatch at the end). By adjusting the phase of the primary reflected wave to the same phase, the driving performance of the driver circuit 5 is prevented from deteriorating, whereby the driving pulse signal waveform is optimized at the end of the transmission cable 3. it can.

According to a second aspect of the present invention, in the transmission cable driving circuit according to the first aspect, the timing pulse signal is provided between the timing pulse signal generating circuit in the driving section and a control terminal of the driver circuit. A signal delay circuit for delaying an output signal of the generation circuit is provided.

The transmission cable driving circuit thus configured has the same operation as the transmission cable driving circuit according to the first aspect, and also has the same function as the previously proposed transmission cable driving circuit shown in FIG. Even when a signal transmission delay time difference occurs between the two output lines of the driver circuit, the rising and falling waveforms of the drive pulse signal can be optimized.

According to a third aspect of the present invention, as shown in the conceptual diagram of FIG. 4, in the transmission cable driving circuit according to the first aspect shown in the conceptual diagram of FIG. A delay element 12 for delaying a drive pulse signal provided between itself and the drive element 2 is constituted by a variable delay circuit 13 having a variable delay time, and a delay time control circuit 14 for switching the delay time is provided. It is a feature.

In the transmission cable drive circuit thus configured, the phase of the drive pulse signal and the reflected signal (due to cable mismatch at the end) at the transmission source (waveform correction circuit 9 side) due to a change in the transmission cable, etc. When a difference occurs in the phase of the primary reflected wave), the variable delay circuit 13 and the delay time control circuit 14 switch the phase difference between the drive pulse signal and the reflected signal to a desired (same phase) value. Even when the transmission cable 3 is changed and the signal transmission delay time in the transmission cable 3 is changed, the drive pulse signal waveform can be optimized at the end of the transmission cable 3. This claim 3
The invention according to the second aspect can be applied to the invention according to the second aspect in combination, and the effects obtained in the second aspect can also be obtained.

[0021]

Next, an embodiment will be described. Prior to the description of the embodiment of the present invention, a first specific example of a transmission cable driving circuit proposed in the earlier patent application will be described with reference to FIG. The same or corresponding components as those shown in the conceptual diagram of FIG. 1 are denoted by the same reference numerals. In the first configuration example, as shown in FIG. 5, the drive pulse signal generated by the timing pulse signal generation circuit 4 in the drive unit 1 is supplied to the first driver circuit 5-1 and the second driver circuit 5 The control circuit 8 is connected to the input terminal of the second driver circuit 5-2 and turns on / off the output of the second driver circuit 5-2 (when OFF, the output impedance of the driver circuit 5-2 is high impedance). Of the driver circuit 5-2. An output line 6 of the first driver circuit 5-1 is connected to a resistor 9-1 constituting the waveform correction circuit 9, and an output line 7 of the second driver circuit 5-2 constitutes the waveform correction circuit 9. It is connected to the capacitor 9-2. The other end of the resistor 9-1 and the other end of the capacitor 9-2 constituting the waveform correction circuit 9 are connected in common and connected to one end of the transmission cable 3 having a characteristic impedance via the resistor 9-3. A driven element 2 such as a CCD is connected to the other end of 3.

According to such a configuration, the first driver circuit 5-1 and the second driver circuit 5-2 during a certain period of time when the drive pulse signal rises and falls.
Since the control circuit 8 controls the second driver circuit 5-2 so that both of them are in the operating state, the output of each of the driver circuits 5-1 and 5-2 constitutes the waveform correction circuit 9. Since the transmission cable 3 and the driven element 2 are driven via the resistor 9-1, the capacitor 9-2, and the resistor 9-3, the resistor 9
The waveform correction circuit 9 having a high-pass filter composed of -1, a capacitor 9-2 and a resistor 9-3 functions to correct the signal attenuation in a high frequency region due to the distribution constant of the transmission cable 3, and as a result, the transmission cable The rising and falling waveform shapes of the pulse signal at the end of 3 are optimized.

In the time other than the rise and fall of the pulse signal (the signal voltage flat period), the control circuit 8 controls the driver circuit 5 so that the output impedance of the second driver circuit 5-2 becomes high.
−2 is controlled (in the signal voltage flat period, since there is no change in the signal, one output of the driver circuit suffices for the driving capability), the impedance when the driving unit 1 side is viewed from the transmission cable 3 side is approximately the waveform The resistor 9− in the correction circuit 9
1 and the resistor 9-3 (the output impedance of the driver circuit is assumed to be small).
If the combined resistance of the transmission cable 3 and the resistor 9-3 is set to the same value as the characteristic impedance of the transmission cable 3, the transmission cable 3 can be matched at the transmission source. The influence due to the signal reflection due to the non-matching at the end is absorbed by the transmission source (on the waveform correction circuit 9 side).
Since the secondary reflection does not occur, as a result, the end of the transmission cable 3 is not affected by the reflected wave even during the signal flat period, and can have an optimal waveform. Reflectance = (Zout−Zo) / (Zout + Zo) (1) where Zo is the characteristic impedance of the transmission cable 3,
Zout is the output impedance of the drive unit 1 as viewed from the transmission cable 3 side.

The configuration of the waveform correction circuit 9 can be modified as long as desired rising and falling waveforms can be obtained. For example, the resistor 9- in the above configuration example can be modified.
3 is not required.

Next, a second configuration example of the transmission cable drive circuit similarly proposed above will be described with reference to FIG. In this configuration example, instead of the second driver circuit 5-2 in the first configuration example shown in FIG. 5, the output of the first driver circuit 5-1 is connected to the first output line 6 and the second output circuit. A second output line 7 and a waveform correction circuit 9
The switch 11 is turned off by the control circuit 8 during a period (signal voltage flat period) other than the rising and falling of the pulse signal, thereby providing the second output line 7. Is set to high impedance, and the same operation function as that of the first configuration example is obtained.

Next, a third configuration example of the transmission cable drive circuit similarly proposed above will be described with reference to FIG. In this configuration example, a signal delay circuit 10 is provided between the timing pulse signal generation circuit 4 and the control terminal of the second driver circuit 5-2 in the first configuration example shown in FIG.

Next, the operation of the third configuration example thus configured will be described with reference to the timing chart of FIG. As shown in the timing chart of FIG. 8, the output a of the first driver circuit 5-1 and the output a of the second driver circuit 5-
If a difference occurs in the output signal delay time of the output b of the second
Of the driver circuit 5-1 and the second driver circuit 5-
The output voltage level difference between the two outputs occurs during the output signal delay period. Therefore, during that period, the second driver circuit 5-2
Is in the operating state, a current proportional to the voltage level difference causes an output line current d between the output line 6 of the first driver circuit 5-1 and the output line 7 of the second driver circuit 5-2. Therefore, the output current driving capability of each of the driver circuits 5-1 and 5-2 to the transmission cable 3 side is reduced.

Therefore, in this configuration example, the control timing of the second driver circuit 5-2 is determined by adjusting the output voltage level during the operation of the second driver circuit 5-2 and the output voltage of the first driver circuit 5-1. The output line 6 of the first driver circuit 5-1 and the second driver circuit 5-2 are controlled by delaying the second driver circuit 5-2 with the delay control signal e so that the voltage levels match. 5-2
8 is prevented from flowing to the output line 7 (f in FIG. 8), and a decrease in the current driving capability of each of the driver circuits 5-1 and 5-2 is suppressed. As a result, even if a signal delay time difference occurs in each output line of the driver circuit at the end of the transmission cable 3, it is possible to optimize the rising and falling waveforms of the pulse signal.

The connection position of the signal delay circuit 10 depends on the output of the timing pulse generation circuit 4 and the second driver circuit 5.
It may be connected to any position as long as it is between the control terminals of -2. For example, in the above configuration example, it may be provided between the control circuit 8 and the control terminal of the second driver circuit 5-2.

Next, a first embodiment of the transmission cable drive circuit according to the present invention will be described with reference to FIG. In this embodiment, a signal delay element 12 is provided between the waveform correction circuit 9 and the transmission cable 3 in the first configuration example of the previously proposed transmission cable drive circuit shown in FIG. The other configuration is the same as the transmission cable drive circuit shown in FIG.

Next, the operation of the present embodiment thus configured will be described with reference to the timing chart of FIG. As shown in the timing chart of FIG. 10, the driving pulse signal (driver circuit output signal: FIG.
When the signal phases of 10A) and the reflected wave (B in FIG. 10) overlap in opposite phases, the output of the driver circuit 5-1 and the output of the driver circuit 5-2 cancel the influence of the voltage level of the reflected wave. In this manner, a large amount of output current is required when the drive pulse signal rises and falls, which leads to a decrease in drive capability, and the rise and fall waveforms of the drive pulse signal at the end of the transmission cable are not optimal (see FIG. 10). C). Note that the following equation (2) holds between the cable delay round trip time t _dd and the unit length cable delay time t _d in B and C in FIG. Cable delay round trip time (t _dd ) = cable length × cable delay time per unit length (t _d ) × 2 (2)

Therefore, in the present embodiment, the delay element 12 (usually using a delay line having an input / output impedance equivalent to the characteristic impedance of the transmission cable) is connected between the waveform correction circuit 9 and the transmission cable 3. With this arrangement, the signal phase of the drive pulse signal and the signal phase of the reflected wave are adjusted to the same phase at the transmission source. As a result, the reflected wave has the same phase as the drive pulse as shown in FIG. 10D, so that the output current of the driver circuit can be reduced by the voltage level of the reflected wave,
It is possible to minimize a decrease in the driving capability of the driver circuit due to the reflected wave. As a result, at the end of the transmission cable 3, the deterioration of the waveform shape due to the reflected wave is suppressed.
As shown in E, the driving pulse signal waveform can be made optimal. The following equation (3) shows the additional delay time for adjusting the phase. Additional delay time = {(cycle x cycle)-(cable length x cable delay time per unit length x 2)} 2 ... (3) Additional delay time: delay time by delay element Cycle: drive Frequency cycle T Cable length: Transmission cable length Cable delay time per unit length: Signal delay time at 1m length

Next, a description will be given of a second embodiment in which the first embodiment of the transmission cable drive circuit according to the present invention is applied to an electronic endoscope camera with reference to FIG. In this embodiment, a delay element provided between the waveform correction circuit 9 and the transmission cable 3 in the first embodiment shown in FIG.
12 is arranged on the scope cable side of the scope section of the electronic endoscope camera. In FIG. 11, reference numeral 21 denotes a camera control unit provided with the drive unit 1 in the electronic endoscope camera, 22 denotes a scope unit, and 23 denotes a scope unit 22.
2 shows a camera head section in the inside. By arranging the delay element 12 on the scope unit 22 side, even if a phase change occurs at the transmission source of the reflected wave due to repairs on the scope unit side (changes in the length and characteristics of the transmission cable, etc.), the scope unit The phase can be adjusted (adjusted) on the main body side, and the commonality of the scope cable is not impaired.

Next, a third embodiment of the transmission cable drive circuit according to the present invention will be described with reference to FIG. In this embodiment, the delay element 12 in the first embodiment shown in FIG. 9 is replaced by a plurality of delay elements 13-1a to 13-1n.
And a variable delay circuit 13 comprising a plurality of switches 13-2a to 13-2n, and a phase difference detection unit 14-1 for detecting a phase difference between the drive pulse signal and the reflected signal, and a variable delay circuit 13 A delay time control circuit 14 comprising a control signal generator 14-2 for switching the switches 13-2a to 13-2n is provided.

Next, the operation of the present embodiment configured as described above will be described. As described in the first embodiment, when there is a difference between the signal phases of the drive pulse signal (A in FIG. 10) and the reflected wave (B in FIG. 10) at the transmission source (on the waveform correction circuit 9 side), Driver circuit 5-1 and driver circuit 5
The -2 output operates so as to cancel the influence of the voltage level of the reflected wave, so that a large amount of output current is required at the point where the voltage of the reflected wave changes (at the time of rising and falling). The drive waveform at the end may not be optimal.

Therefore, in this embodiment, the delay
The phase difference detector 14-1 in the time control circuit 14
(Waveform correction circuit 9 side) drive pulse signal and reflected wave signal
The phase difference of the signal phase is detected, and the control corresponding to the phase difference is detected.
The control signal is generated by the control signal generator 14-2, and the variable delay
The switches 13-2a to 13-2n of the circuit 13 are switched to
The signal phase of the drive pulse signal and the reflected wave
By operating as described above, the dry
Minimizing the drive capability degradation of the bus circuits 5-1 and 5-2,
Waveform shape due to reflected wave at the end of transmission cable 3
Of the drive pulse signal waveform
it can. For example, as shown in FIG.
The delay time of the delay elements 13-1a to 13-1n of the circuit 13 is 2
^n-1(nS), 2 ^n-2(nS), ... 2ⁿⁿ(nS) (n is
(The number of delay elements), 2ⁿ-1 (n
S) Controllable up to time. It should be noted that FIG.
Is switch control when there are three delay elements
9 shows a setting example of a control delay time corresponding to an aspect.

FIG. 14 is a diagram showing a fourth embodiment in which the third embodiment of the transmission cable drive circuit according to the present invention is used in an electronic endoscope camera. In this embodiment, the variable delay circuit 13 and the delay time control circuit 14 in the third embodiment shown in FIG. 12 are arranged on the camera control unit 21 side of an electronic endoscope camera. By arranging the variable delay circuit 13 and the delay time control circuit 14 on the camera control unit 21 side in this way, the source of the reflected wave due to the repair on the scope side (change of the length and characteristics of the transmission cable, etc.) Even if a phase change occurs, since the phase is controlled on the camera control unit main body side, without changing and adjusting the scope cable each time the repair is performed, and without adding a circuit to the existing scope cable, the third control can be performed.
The effect of the embodiment can be obtained.

[0038]

As described above, according to the present invention, according to the present invention, the attenuation of the drive pulse signal in the transmission cable in the high frequency region is corrected, and the transmission source of the transmission cable is set to the characteristic of the transmission cable. Correction is made to match the impedance, preventing signal reflection at the transmission cable source, obtaining the optimal drive pulse signal waveform at the termination source, and changing the phase of the reflected wave at the transmission source due to the change in transmission cable characteristics. If there ’s a change,
A transmission cable drive circuit capable of adjusting the phase of the drive pulse signal and the phase of the reflection signal at the transmission source to the same phase, thereby suppressing a reduction in the drive capability of the driver circuit and optimizing the drive pulse signal waveform. Can be realized.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for describing a configuration of a transmission cable driving circuit proposed earlier.

FIG. 2 is a conceptual diagram for explaining another configuration of the transmission cable driving circuit proposed earlier.

FIG. 3 is a conceptual diagram for explaining the invention according to claim 1 of the present application.

FIG. 4 is a conceptual diagram for explaining the invention according to claim 3 of the present application.

FIG. 5 is a block diagram showing a specific configuration example of the transmission cable driving circuit shown in FIG. 1;

FIG. 6 is a block diagram showing another specific configuration example of the transmission cable driving circuit shown in FIG. 1;

FIG. 7 is a block diagram showing a specific configuration example of the transmission cable drive circuit shown in FIG. 2;

8 is a timing chart for explaining the operation of the transmission cable drive circuit shown in FIG.

FIG. 9 shows a first example of the transmission cable according to the present invention shown in FIG.
FIG. 2 is a block diagram showing an embodiment.

10 is a timing chart for explaining an operation of the first embodiment shown in FIG.

11 is a block diagram showing a second embodiment in which the first embodiment shown in FIG. 9 is applied to an electronic endoscope camera.

FIG. 12 is a block diagram showing a third embodiment of the present invention.

13 is a diagram illustrating a setting example of a delay time of a delay element and a setting example of a control delay time of a variable delay circuit according to the third embodiment illustrated in FIG. 12;

FIG. 14 is a block diagram showing a fourth embodiment in which the third embodiment shown in FIG. 12 is applied to an electronic endoscope camera.

FIG. 15 is a block diagram illustrating a configuration example of a conventional electronic endoscope camera.

FIG. 16 is a block diagram showing another configuration example of the conventional electronic endoscope camera.

FIG. 17 is a block diagram showing still another example of the configuration of a conventional electronic endoscope camera.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drive unit 2 driven element 3 transmission cable 4 timing pulse signal generation circuit 5 driver circuit 5-1 first driver circuit 5-2 second driver circuit 6 first output line 7 second output line 8 control circuit 9 Waveform correction circuit 9-1 Resistance 9-2 Capacitance 9-3 Resistance 10 Signal delay circuit 11 Switch 12 Delay element 13 Variable delay circuit 14 Delay time control circuit 14-1 Phase difference detector 14-2 Control signal generator 21 Camera Control unit 22 Scope unit 23 Camera head unit

Claims (3)

[Claims] 1. A drive section, a driven element driven by the drive section, and a drive signal output from the drive section, electrically connected between the drive section and the driven element. A transmission cable having a characteristic impedance of the transmission cable, the driving unit that drives the transmission cable having the characteristic impedance and the driven element, a timing pulse signal generation circuit,
A driver circuit having two output lines for amplifying an output signal of the timing pulse signal generation circuit, a control circuit for controlling one output line of the driver circuit to high impedance for a certain period, and each of the driver circuits A transmission cable drive circuit, comprising: a waveform correction circuit to which an output line is connected; and a delay element provided between the waveform correction circuit and the driven element for delaying a drive pulse signal. 2. A signal delay circuit for delaying an output signal of the timing pulse signal generation circuit between the timing pulse signal generation circuit in the drive unit and a control terminal of the driver circuit. Claim 1
Transmission cable driving circuit according to the above. 3. A delay element provided between the waveform correction circuit and the driven element for delaying a drive pulse signal is constituted by a variable delay circuit having a variable delay time, and the delay time of the variable delay circuit is changed. The transmission cable driving circuit according to claim 1 or 2, further comprising a delay time control circuit for switching the transmission cable.