JPS58169603A - Control voltage generation circuit depending on ac voltage - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for generating a control voltage dependent on an alternating current voltage. The circuit then has a charging capacitor, the state of charge of which is dependent on the alternating voltage and is varied via controllable charging and discharging current paths as follows. That is, when the amplitude of the alternating current increases, the charging capacitor is charged through the valve circuit, and when the amplitude decreases, the conductance of the discharge current path increases. At this time, a delay element is inserted into the control circuit of the discharge current path. Also, the conductance of the discharge current path is controlled depending on the time difference between the increase and decrease of the alternating voltage amplitude. moreover,
An alternating current voltage is evaluated to change the state of charge of the capacitor.

Such a circuit is described in German Patent No. 28307
This circuit is described in Specification No. 84 and No. 2830786. This circuit is used as a control voltage generator.
It is possible to use it in the ξ-da system, which is described in German Patent No. 2 406 258.

In the converter circuit, the alternating voltage output signal of the amplifier during compression and the alternating voltage input signal during expansion are fed to the input side of the control voltage generator. in this case,
The DC voltage output signal of the control voltage generator is in the active signal path and is fed to the control input of the amplifier, the amplification of which can be electrically controlled. This control voltage generator works as follows. That is, when the AC voltage supplied to its input side increases rapidly, the control voltage generator rapidly generates a DC voltage corresponding to the voltage increase value. This DC voltage quickly changes the amplification of the amplifier in the active signal path.

Changing the amplifier transmission amount rapidly is especially important when the level of the useful signal changes dramatically over a wide range. When the transmission amount does not change, if the level suddenly changes from a small value to a large value, the compressor force signal may over-oscillate,
Therefore, overcontrol of the transmission channel may occur. Also, if the level suddenly changes in the opposite direction, during the transition period to control, the noise signal that is masked when a valid signal is present appears as an audible signal at the output of the expander. In order to obtain complementary characteristics of the compressor and decompressor, it is advantageous to consider the characteristics specific to the operation of the compressor and decompressor in the same way.

Therefore, a control voltage generator for controlling the transmission amount of an amplifier in the effective signal path must supply a control voltage that quickly adapts to the respective level. In that case,
When the level fluctuates widely, the discharge time constant of the charging capacitor in the control voltage generator should be shortened. In steady state or slowly varying levels, the discharge time constant is increased to prevent the control voltage from varying in response to the valid signal. This is because the distortion rate increases when the control voltage fluctuates.

To achieve the above, the discharge of a charging capacitor is utilized. In that case, the time constant of the charging capacitor, in which the above-mentioned relationship must be maintained, in a circuit in which the charging capacitor discharges when the amplitude of the alternating voltage decreases, and in a circuit in which the capacitor is charged in the same case, imposes contradictory requirements. need to be controlled to meet the requirements. For this purpose, a circuit is used which can control the discharge time constant in such a way that over-oscillations are reliably prevented, the distortion factor is reduced, and the noise signal can be physiologically masked by a stronger useful signal.

This type of circuit is described in German Patent No. 285073
It is described in Specification No. 6. This known circuit has the advantage that the delay time of the delay element can be controlled in such a way that the distortion factor is kept to an acceptable value, taking into account the short duration of the unmasked noise.

Applicant's Federal Republic of Germany patent application P2812431
．． Specification No. 4 includes the Federal Republic of Germany Patent No. 28507.
No. 36, a companding type rectifier circuit is described. This rectifier circuit obtains partially linear characteristics by limiting the rectified voltage.

Purpose of the Invention The basic problem of the present invention is to solve the above-mentioned patent No. P2850736.
By means of a circuit different from the basic principle described in the specification, it is possible to control the discharge time constant, taking into account overvibration prevention, small distortion factor, physiological masking of noise signals by a strong effective signal, etc., as in the known ones. It is to do so.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block circuit diagram of a known control voltage generation circuit. Here, 1 is a controllable amplifier, whose input terminal 2 is supplied with an alternating current voltage. An amplified or controlled modified output voltage, for example a compressed or expanded output voltage, is taken off at the output 3. amplifier 1
The control input side of the control circuit 5 is connected to the control circuit 5, and the input terminal thereof is connected to the input terminal 2. In the control circuit 5, an AC voltage is applied to the base of the transistor 70 via the collector 6. The pace is grounded via a resistor 8.

A charging capacitor 9 is provided in the emitter circuit of the transistor 7, and this capacitor 9 is charged via the transistor 7 by the operating voltage source +U. The charging state of the charging capacitor 9 serves as a reference for the voltage value of the AC voltage supplied to the transistor 7. The voltage of the charging capacitor is fed directly or via a separate amplifier to a controllable amplifier. A resistor 10 is connected in parallel with the charging capacitor 9. Resistor 10 is used to determine the time constant of the circuit and to discharge capacitor 9 at the same time.

This type of circuit is described in German Patent Application No. 19
A known control circuit is also shown in FIG. 2 described in Japanese Patent No. 34306.

The control circuit 5 of FIG. 2 has an operational amplifier 11, which is connected to a rectifier 12 for charging the charging capacitor 9. The control circuit 5 of FIG. The operation of this circuit roughly corresponds to that of the circuit shown in FIG. 1. The coupling capacitor 13 and leakage resistor 14 in FIG. 2 correspond to the capacitor 6 and resistor 6 in FIG. However, in this case, the charging capacitor 9 is configured to match the input resistance of the operational amplifier 11.
The current that flows during charging serves as a reference for the state of charge of the capacitor 9. The current flows through transistor 7 or diode 12.

DESCRIPTION OF EMBODIMENTS FIGS. 3 and 4 are block circuit diagrams of a control circuit according to the present invention. Among these two circuits, the circuit shown in FIGS. 1 and 2 has been modified as follows. That is, the value of the voltage or current supplied to the collector of the transistor 7 of FIG. 1 (FIG. 3) or of the transistor 20 (FIG. 4) configured as a diode 12 of FIG. 2 can be evaluated. In this modified circuit, transistor 7.20
A current mirror 15 is connected to the 0-bow rectifier circuit. The current mirror 15 has a mirror-symmetrical current 1 to the charging current
is supplied to the current control input 16 (current sensitive input) of the trigger circuit 17. As a trigger circuit, for example, an AEG-type EFUNK11CN Wissenscha
ftlicheBerichte l 979 172
It is possible to use a so-called mo/flotso (monostable multivibrator) as described on page 103 of the issue. The trigger circuit 17 includes a resistor 10 in series with a resistor 18.
is used to switch the switches 19 connected in parallel. The switch 19 may be a component of the trigger circuit 17.

The circuit described in FIGS. 3 and 4 improves the characteristics of the control voltage generator when the amplitude of the alternating voltage is reduced.

When the amplitude of the alternating voltage decreases slowly, the charging capacitor 9 also slowly discharges via the resistor 10. This slow discharge time constant is the maximum allowable distortion deviation when the signal frequency is the lowest.
is determined so that it can be obtained. This time constant is determined by capacitor 9 and resistor 10. When transmitting a wideband signal (for example, an electroacoustic signal) having a low lower limit frequency, a large time constant of several seconds is required to keep the distortion factor low.

However, if the alternating voltage drops rapidly, a large time constant becomes a hindrance, since the transmission amount does not decrease as rapidly, for example in an expander. As a result, the disturbance noise in the transmission path that was previously masked by the strong effective signal is now
become audible to human ears. Therefore, when the amplitude of the alternating voltage decreases rapidly, the discharge time in the control voltage generator must be short. In other words, a small discharge time constant is required. To meet this demand, transistor 7
The electrical values that depend on the charging current to the charging capacitor 9, such as the voltage supplied to the collector and the current corresponding to the current, are evaluated in the form shown in Figures 3 and 4. be done. If the effective signal is small, the charging current will not flow. This means that the resistor 18 is then connected via the switch 19.
is evaluated for connecting in parallel with resistor 10. Thereby, the discharge rate of the capacitor 9 increases, for example, by a factor of 10.

However, in order to reproduce the last vibration train of a strong useful signal without distortion, starting from the end of this last vibration train /I:
A switch to a small time constant takes place. For this purpose, a monostable multi-node isolator 17 is inserted between the current mirror 15 and the switch 19. Thereby, when the current 1' becomes 0, after a certain delay time, the switch 1
9 is closed. The oscillation period is the longest when the signal frequency is the lowest. Therefore, the delay time when switching from a large time constant to a small time constant must be determined according to the lowest signal frequency. If, before this delay time has elapsed, the amplitude of the useful signal becomes small, unmasked noise appears at the output of the expander. However, human hearing
Even though the bell changes in response to large sound pressure or small sound pressure,
It takes some time. Therefore, even if the delay time when switching the time constant is shorter than the time that physiologically matches human hearing, no unmasked noise will be perceived.

German Patent Application No. P 281 243° 4 describes a rectifier circuit of the compression/expansion type according to German Patent No. 2 850 736. This rectifier circuit obtains partially linear characteristics by limiting the rectified voltage.

In the device of the color diagram, additional circuit elements shown in FIG. 5 are used to obtain a partially linear characteristic. Here, a power supply resistor 23 is connected. Resistor 23 is transistor 21. which acts as a diode. It is connected to a series circuit consisting of a resistor 22, a switch 25, and a resistor 24. The emitter of the transistor 21 is connected to the output terminal 4. Switches 19 and 25 are interlocked to operate in conjunction with each other. The output terminal is grounded via a Zener diode 26.

The control voltage appearing at the output terminal is limited in the positive direction by the Zener diode 26.

In order to determine the minimum value of the control voltage, output 4 is connected via the base-emitter path of transistor 21 to a reference voltage. This reference voltage is the transistor 21
higher than the minimum voltage desired at the output 4 by the base-emitter forward voltage of . In this circuit, resistor 24
A reference voltage is taken off from the working voltage via a parallel connection consisting of the series connection of the switch 25 and the resistor 22 and a voltage divider formed by this and the resistor 23.

If no input signal appears at input terminal 2, switch 1
9 is closed. Therefore, resistors 18 and 10 are connected in parallel. Accordingly, the desired minimum voltage applied to the output 4 produces a current 1□ flowing through the resistor 18.10. The current I□ also flows through the base-emitter path of the transistor 21, where a voltage drop Ul occurs. U□ is obtained from the following formula.

In this case, K is Boltzmann's constant, T is absolute temperature, and q is the value of charge. Engineering. is a constant determined by the substance,
In the case of a normal silicon transistor 14, the current is ~10A.

If an input signal is applied to the input side 2 which is slightly larger than the signal corresponding to the desired lower bending point of the characteristic curve, the transistor 20 conducts for a short time during the peak of the signal. At that time, a current equal to the current flowing through the transformer and nostar 20 flows from the current mirror 15. This current 1 is the current input side 1
6 triggers the monostable multivibrator 17. The switch 19 is then opened. At this time, the resistor 18 is no longer connected in parallel with the resistor 10, so the minimum value of the Sarel current supplied from the transistor 21 to limit the control voltage at the terminal falls from 1 to 1.

Therefore, the base-emitter forward voltage of the transistor 21 also decreases from U to Ul.

If the resistance value of only the resistor 1o is, for example, 10 times the resistance value of the parallel circuit consisting of the resistor 10.18, then the following equation is obtained. At this time, the forward voltage between the base and emitter of the transistor 21 changes by a large amount. In this example, it is Ul-Ul z26 mV · in loz60 mV.

Follow 1. The minimum control voltage defined by transistor 21 and resistor 22.23 is increased by 60 mV. This is undesirable and also causes distortion in the lower bend region of the desired partially linear characteristic of the conductor. According to the invention, this increase in the minimum control voltage at the output side is compensated as follows.

That is, when the switch 19 is opened, the reference voltage is lowered by the difference due to the forward voltage of the transistor 21. This operation is performed as follows, for example. That is, at the same time as switch 19 is opened, switch 2 is opened.
5 is closed, and the resistor 24 is connected in parallel with the resistor 22. This changes the voltage division ratio of the voltage divider that generates the reference voltage so that the reference voltage changes as desired.

FIG. 6 shows another embodiment of the reference voltage control circuit. This circuit is used to match the reference voltage to different usage conditions. This circuit shows a part of the circuit of FIG. 5, and includes a Zener diode 26, a transistor 2
1. Contains resistors 22 and 23 connected in series. A series circuit of a switch 28 and a resistor 27 is connected in parallel with the resistor 23 . Switches 19 and 28 are operated synchronously, as in the embodiment of FIG. When switch 19 is opened, switch 28 is also opened. Therefore, the voltage division ratio of the voltage divider 23,22 is changed so that the desired change in the reference voltage occurs.

In this case, any circuit can be used as long as it can change the reference voltage applied to the base of the transistor 21 by a desired value in synchronization with the opening and closing of the switch 19.

FIG. 7 shows a circuit in which a large number of diodes 29 are connected in series. This diode series circuit is used to limit the maximum value of the control voltage instead of the Zener diode-P2O

[Brief explanation of the drawing]

1 and 2 are block circuit diagrams of a known control voltage generation circuit, FIGS. 3 and 4 are block circuit diagrams of a control voltage generation circuit according to an embodiment of the present invention, and FIG. 5 is a block circuit diagram of a control voltage generation circuit according to an embodiment of the present invention. 6 is a block circuit diagram of an embodiment of the present invention of a control voltage generation circuit having a control voltage generating circuit according to the present invention, FIG. 6 is a block circuit diagram of an embodiment of the present invention that is a modification of the voltage limiting circuit shown in FIG. 5, and FIG. 7 is a series connection circuit of diodes. FIG. 1... Controllable amplifier, 2... Input terminal, 3...
Output side, Cow... Control input side, 5... Control voltage generation circuit, 6... Capacitor, 9... Charging funden-IJ
-111..., operational amplifier, 12... rectifier, 13
...Coupling capacitor, 14...Leakage resistance, 15...
・Current mirror, 16...Current input side, 17...
Trigger circuit, 19.25.28... switch, 26.
...Zener diode, no change in content in drawing "if possible" 7) Fig, 1 Fig, 2 Fig, 4 Procedural amendment (method) May 12, 1980 To the Commissioner of the Japan Patent Office 1, Indication of case 1981 Patent Application No. 3596 2, Name of the invention: Control voltage generation circuit dependent on AC voltage 3, Person making the amendment Relationship to the case: Patent applicant 4 Sub-agent 5, Date of amendment order: April 26, 1980 (Delivery date) However, engraving of the drawings (no changes to the contents)

Claims (1)

[Claims] 1. It has a charging capacitor (9), and when the amplitude of the AC voltage increases, the charging state of the charging capacitor (9) is controlled by the capacitor (7, 12, 20). 9) is charged and the conductance of the discharge current path (lO, 18) increases when the amplitude of the alternating voltage decreases, depending on the alternating current voltage, through controllable charging and discharging current paths. In this case, a delay element (17) is arranged in the control path of the discharge current path, and the conductance of the discharge current path is controlled depending on the time difference between the increase and decrease of the alternating voltage amplitude, and In a circuit for generating a control voltage dependent on an alternating voltage, in which the alternating voltage is evaluated in order to change the state of charge, a charging capacitor ( 9) is supplied with charging current,
Generation of a control voltage dependent on an alternating current voltage, characterized in that the collector voltage of the transistor (7, 20) serves as a reference for the state of charge, and the collector voltage, collector current, or a value corresponding thereto is supplied to the evaluation circuit. circuit. 2. A current mirror (15) is inserted into the collector path of the transistor (7, 20) as an evaluation circuit, and the current generated by the current mirror (15) is applied to the current control input side of the trigger circuit (17) as a delay circuit. (16) The □ circuit according to claim 1 provided in claim 1. 3. It has a charging capacitor (9), and when the amplitude of the AC voltage increases, the charging state of the charging capacitor (9) is controlled by the capacitor (9) via the valve circuit (7, 12, 20). and can be varied depending on the alternating voltage via controllable charging and discharging current paths, such that when the amplitude of the alternating voltage decreases, the conductance of the discharge current path (10, 18) increases; At that time, a delay element (17) is arranged in the control path of the discharge current path, and the conductance of the discharge current path is controlled depending on the time difference between the increase and decrease of the AC voltage amplitude, and the state of charge is further controlled. In a circuit for the generation of a control voltage dependent on an alternating voltage, in which the alternating voltage is evaluated in order to be varied, a charging capacitor (9) is connected to the charging capacitor (9) via the emitter-collector path of the transistor (7, 20) for evaluating the alternating voltage. A charging current is supplied, the collector voltage of the transistor (7, 20) serves as a reference for the state of charge, and the collector voltage, collector current or their corresponding values are supplied to the evaluation circuit, and a control voltage dependent on the alternating current voltage is supplied. However, the limit circuit (21 to 28)
A circuit for the generation of a control voltage dependent on an alternating current voltage, characterized in that the circuit elements (24, 25° 27.28) keep the minimum control voltage constant in the event of changing operating conditions.