JP3227166B2 - Absolute value circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, in particular also the related to the absolute value circuit of broadband.

[0002]

2. Description of the Related Art An absolute value circuit is a type of full-wave rectifier circuit.
It converts the polarity of one half-wave of the AC input voltage to the same polarity as the other half-wave, and there is an example shown in FIG. 5 as one of the generally used absolute value circuits.

In the circuit shown in FIG.
1, a half-wave rectifier for obtaining a positive half-wave output by combining the amplifier A1, the diode D1, and the feedback resistor R2; and sharing the input resistor R1 and the amplifier A1 with the diode D
2. A half-wave rectifier for generating a negative half-wave output by combining a feedback resistor R3, an amplifier A2 and resistors R4, R5, R6
, And each resistance value is usually set to R2 = R3 R4 = 2 · R6.

Accordingly, the gain of the amplifier A1 with respect to a signal applied to the amplifier A1 via the resistor R1 is R2 / R1 = R
3 / R1. The gain of the amplifier A2 via the resistor R4 is R5 / R4, and the gain of the signal via the resistor R6 is R5 / R4.
Since / R6 = R5 / (R4 / 2), that is, 2R5 / R4, the amplification degree is twice as large.

Here, for example, a resistor R1 is connected from an input terminal T1.
When a sine-wave AC voltage e (i) having a maximum value E as shown in FIG. 6A is applied to the amplifier A1 via the line A, the output of the amplifier A1 becomes negative with respect to the positive half-wave. Becomes In this case, since the negative input terminal of the amplifier A1 is imaginary earth, the output side of the amplifier A1 has a lower potential than the negative input terminal, so that the diode D1 is off and the cathode side voltage e (a) is as shown in FIG. ), The ground potential, ie, zero.

When the input voltage e (i) is a negative half wave, the output of the amplifier A1 is positive and the diode D1 is turned on. For example, when R1 = R2, the amplifier A1 has a gain of 1
6B, the cathode-side voltage e (a) of the diode D1 has the same magnitude as the input voltage e (i) and a half-wave rectified voltage e of which polarity is inverted as shown in FIG. 6B. (A) = − e (i).

The half-wave rectified voltage e (a) is, for example, a resistor R
6, and the input voltage e (i) is applied to the amplifier via a resistor R4. In this case, the amplification of the amplifier A2 with respect to the voltage e (a) is 2R5 / R4 as described above, and the amplification with respect to the voltage e (i) is R5.
/ R4. The voltages amplified at this amplification degree are shown in FIGS. 6C and 6D, respectively. When these amplified voltages are added to each other by the amplifier A2, a full-wave rectified voltage e having, for example, a negative polarity and the same magnitude of each half-wave voltage is output from the output terminal T2 as shown in FIG. (O) is obtained.

When a forward voltage applied between the anode and the cathode of a diode exceeds, for example, about 0.6 V in a silicon diode, the diode turns on and a current flows, and a voltage lower than that, that is, 0 to 0.6 V There is a dead voltage zone in which it does not turn on between the two. In the rectifier of FIG. 5, when the diode D1 is turned on, a feedback loop including the diode D1 and the resistor R2 is closed, and the amplifier A1 operates as an amplifier having a gain of 1 as described above.

On the other hand, in the dead voltage band, the feedback loop is open because the diode D1 is turned off. In this case, the amplifier A1 operates at the originally high gain, that is, the so-called gain. Therefore, for example, even a very small voltage near the rise or fall of the input voltage e (i) is greatly amplified, and an output exceeding the dead voltage is generated to turn on the diode. Thereby, the dead voltage of the diodes can be substantially ignored, and the output voltage of the full-wave rectification type as shown in FIG.

[0010]

Absolute value circuit [0005] has been widely utilized in the field of converting alternating current and in direct current, bandwidth of the absolute value circuit is desired in accordance with the frequency of the AC signal to be handled is high It has become. However , in a conventional circuit, when obtaining a full-wave rectification type output voltage e (o),
Amplified voltage and half-wave rectified voltage e of AC power voltage e (i)
2-fold amplification voltage of (a) was formed by the amplifier A2, so that added together. For this reason, in the high frequency region, for example, as shown in FIG.
During one cycle of (o), there is a problem that a level or a time width mismatch occurs between one half-wave voltage and the other half-wave voltage, and it is difficult to increase the upper limit of the applicable frequency.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a wide-band absolute value circuit capable of expanding the upper limit of the applied frequency to approximately twice that of the conventional device with a relatively simple configuration. To provide.

[0012]

Means for Solving the Problems Referring to the embodiment of FIG .
In order to achieve the above object, the present invention provides the following (1)
Or (4) means. (1) Input resistor R1, the amplification degree 1 of amplifier A1, a semiconductor integer
With a diode D1 and a feedback resistor R2 as stream element, for rectifying one of the half-wave voltage of the AC input voltage e (i)
First half-wave rectifier circuit 1.

[0013] (2) above fill out force resistance R1 and the amplifier A1
And the diode D2 and the feedback resistor R
Comprising a feedback resistor R3 of 2 and equal, the second half-wave rectifier circuit for rectifying the other half-wave voltage of the AC input voltage (e (i)) 2.

[0014] (3) has a input resistor R7 and amplifier A3 and the feedback resistor with a value equal with the input resistor R7 R8, for example
For example, an inverting circuit 3 having an amplification degree of 1 which receives the output voltage of the second half-wave rectifier circuit 2 and inverts its polarity.

[0015] (4) the two input resistors, such as arbitrary values R4, R
6 and includes a feedback resistor R5 equal to the amplifier A2 and the input resistor R4, R6, for example, with receiving the half-wave rectified voltage from the half-wave rectifier circuit 1 of the first through the input resistor R4, the the inverting circuit 3 via an input resistor R6
And an amplification circuit 1 having an amplification degree of 1 for receiving the other half-wave rectified voltage of which the polarity is inverted and adding the two half-wave rectified voltages.

[0016]

According to the means (1) and (2), two positive and negative half-wave rectified voltages having the same magnitude as the input voltage and different polarities can be obtained. Therefore, when the polarity of one half-wave rectified voltage is inverted by means of (3), the two half-wave rectified voltages applied to the adder circuit 4 have the same polarity. When the two half-wave rectified voltages are added by the means (4) with the same amplification degree, the added output becomes the input voltage e (i) and the absolute value up to almost twice the upper limit of the operating frequency in the conventional circuit. Are equal to each other.

[Operation Principle] The operation principle of the absolute value circuit according to the present invention will be described below with reference to FIG. In FIG. 2A, for example, when a voltage e is applied to the amplifier at time t = 0, it takes some time from when the output rises to when it reaches the same magnitude as the input voltage e. This rising speed is generally called a slew rate. In catalog specifications and the like, for example, the input voltage e when the amplification degree of the amplifier is set to 1 and the output of the amplifier are the input voltage e.
E / t1 [V /
μs] is the slew rate.

The case where the output voltage falls is similarly defined. For example, when the input voltage e of the amplifier becomes zero at t = tn, the time required for the output voltage to fall and reach zero is defined as t2. Then, the slew rate is e /
It is represented by t2 [V / μs]. Note that the rise time and the fall time of the output voltage are not necessarily equal, but there is no problem in practical use even if t2 = t1. Therefore, one slew rate value is usually described in catalog specifications and the like. .

Therefore, assuming that the inclination angle of the rise or fall of the output voltage with respect to the time axis is equal and that is θ, the slew rate = e / T (1) = tan θ (2) Can write. Thus, θ = arctan (e / T) (3)

That is, the value of the slew rate corresponds to the rising or falling inclination angle θ of the output voltage, and the rising or falling voltage along this inclination angle can respond to the input voltage of the amplifier. This is the fastest output voltage. In other words, for an input voltage that rises between 90 ° and 90 ° or more, the output of the amplifier cannot exceed the tilt angle θ and cannot follow the input voltage.

Here, as shown in FIG. 2B, the input voltage e (i) of the amplifier is, for example, a sine wave voltage e (i) = Esinωt (4). Where E is the maximum value, ω = 2π
In f, f is a frequency.

Now, at the point of t = 0, the input voltage e
Assuming that a tangent OA is drawn in (i) and an angle between the tangent and the horizontal axis (time axis) is θ (i), θ (i) is an input voltage e.
(I) represents the rising angle. Therefore, the value of θ (i) is

[0023]

(Equation 1) You can keep. Substituting equation (4) into the above equation gives θ (i) = arctan (ωE). Since θ (i) must not exceed θ in FIG. 2A, θ (i) ≦ θ. If an equal sign is used and θ (i) = θ, θ = arctan (ωE) If the slew rate of the amplifier is expressed as SR, ωE = e / T = SR from the above equation and equations (3) and (1). is there. Therefore, f = SR / 2πE (5a) is obtained from 2πfE = SR (5). According to the formula (5) or (5a), the slew rate SR is a value specific to the amplifier and is known, so that the maximum frequency f of the AC signal e (i) in which the amplifier can linearly operate.
Is determined by the magnitude of the voltage E. If the frequency actually handled is f> SR / 2πE or E> SR / 2πf with respect to the voltage, the amplifier cannot follow and the output voltage waveform is distorted.

Here, assuming that a frequency at which the voltage E can be linearly operated when the voltage E is multiplied by n is f (n), the equation (5a) is obtained.
Thus, f (n) = SR / 2πnE. By substituting equation (5) into the above equation, f (n) = f / n is obtained. That is, for example, assuming that each amplifier in the device has substantially the same slew rate and the voltage level of the input / output signal in those amplifiers is E, the upper limit of the frequency at which the device can linearly operate within the above slew rate The value is f
Becomes However, one of the amplifiers has n times the voltage n
When E is an input or an output, it is difficult to increase the slew rate of the amplifier by n times.
It is necessary to limit the upper limit of the operating frequency band of the device to 1 / n of f.

FIG. 2C shows an example where n = 2. In the figure, (a) is the signal Esinωt of the above equation (4) where the maximum voltage is E, OA is the tangent at the rising time t = 0, and θ is the inclination angle corresponding to the slew rate of the amplifier. . (B) is a signal 2Esinωt having a maximum voltage of 2E, for example, as shown by a broken line, the amplifier cannot follow a voltage rising or falling at an inclination angle larger than the above θ, and its response output is a tangent. Distortion occurs as a waveform along. In such a case, as shown in (c) and (d), 1
The cycle repetition time is set to twice (a) or (b), that is, the frequency is set to f / 2. Incidentally, FIG. 3 shows an example in which the final output voltage becomes a value different from the absolute value of the input voltage when the frequency is not reduced to 1/2 in the conventional device.
3A to 3D and FIG. 3E correspond to FIGS. 6A to 6D and 6F, respectively.

[0026]

Referring again to FIG. 1, the absolute value circuit according to the present invention, as described in the above-mentioned means for solving the problems, for example, rectifies one and the other half-wave voltages of the input voltage, respectively.
Two half-wave rectifier circuits 1 and 2, an inverting circuit 3 for inverting the polarity of the rectified voltage of the half-wave rectifier circuit 2, and a half-wave voltage whose polarity has been inverted by the half-wave rectifier circuit 2 And the input resistors and the feedback resistors R1 to R8 are all set to the same resistance value so that the amplifiers A1, A2, and A3 of each circuit operate at an amplification factor of 1. ing.

Next, the operation of each section will be described with reference to FIG. When a sine wave voltage e (i) = Esinωt is applied to the input terminal T1 (FIG. 1), for example, as shown in FIG. 2A, the half-wave rectifier circuits 1 and 2 operate as an amplifier A1 operating at an amplification factor of 1 and a diode D1. , D2 to form and transmit half-wave rectified voltages e (a) and e (b) as shown in FIGS. 4 (B) and 4 (C), respectively.

One half-wave rectified voltage e (a) is applied to an amplifier A2 set to an amplification degree of 1, for example, via a resistor R4 of an adder circuit 4. Further, the other half-wave rectified voltage e (b) is applied to the amplifier A3 which is also set to the amplification degree 1 via the resistor R7 of the inverting circuit 3, for example, and its polarity is changed as shown in FIG. After inversion, the resistance R6
, And is applied to the amplifier A2. The amplifier A2 amplifies these two half-wave rectified voltages at the same magnification and adds them. In this embodiment, since the maximum voltage handled in the device is E, if the frequency f that satisfies the expression (5a) shown in the above description of the operation principle is set as the upper limit value of the operating frequency band, the addition of the amplifier A2 is performed. The output e (o) is a full-wave rectified voltage having an absolute value equal to the magnitude of the input voltage e (i) as shown in FIG.

The above is an example in which the inverting circuit 3 is provided between the output side of the half-wave rectifier circuit 2 and the input resistor R6 of the adder circuit 4. R
An inversion circuit may be provided between the four. In this case, the polarity of the added output voltage shown in FIG. 4E is positive, but the principle of operation is the same as that described above, and a description thereof will be omitted.

[0030]

As described above in detail, according to the present invention, two rectifier circuits 1 for half-wave rectifying the input voltage e (i).
And 2, a polarity inverting circuit 3, and an adding circuit 4. The voltage amplification of the amplifiers A1, A2, and A3 constituting each of the above circuits is set to 1, and the slew rate of the amplifier and the input voltage e are set. The frequency f determined by the maximum value E of (i) is set as the upper limit of the operating frequency band.

Therefore, according to the present invention, it is possible to increase the upper limit of the frequency band to almost twice as much as that of a conventional device requiring a voltage 2E whose maximum value is twice the input voltage in the course of signal processing, for example. Thus, a wide-band absolute value circuit can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment to which the present invention is applied.

FIGS. 2A to 2C are waveform diagrams for explaining the operation principle.

FIG. 3 is a waveform chart for explaining the operation principle.

FIG. 4 is a waveform chart for explaining the operation of each unit.

FIG. 5 is a block diagram showing a configuration of a conventional device.

FIG. 6 is a waveform chart for explaining the operation of the conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 half-wave rectifier circuit 2 half-wave rectifier circuit 3 inverting circuit 4 adder circuit A1, A2, A3 amplifier D1, D2 diode e (i) AC input voltage e (a), e (b) half-wave rectified voltage e (o) Full-wave rectification output voltage R1, R4, R6 Input resistance R2, R3 Feedback resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/21 G01R 1/30 H03D 1/10

Claims (1)

(57) [Claims] [Claim 1] input resistor (R1), the amplification degree first amplifier (A1), a feedback resistor (R2) and the semiconductor rectifying element (D
Include 1), shared with the AC input voltage (e (i) the first half-wave rectifier circuit for rectifying one of the half-wave voltage) (1), the input resistor (R1) and the amplifier (A1) is With
A feedback resistor (R3) and a value equal to the feedback resistor (R2)
Includes a good beauty semiconductor rectifier (D2), and a said AC input voltage (e (i)) the second half-wave integer <br/> flow circuit for rectifying the other half-wave voltage (2) In the absolute value circuit, a half-wave rectified voltage (e (b)) having an amplifier (A3) configured to have an amplification factor of 1 and transmitted from the second rectifier circuit (2).
An inverting circuit (3) for inverting the polarity of the half-wave rectified voltage (e (b)) sent from the inverting circuit (3) and the half-wave rectified sent from the first rectifying circuit (1) It has an amplifier (A2) having an amplification degree of 1 which receives the voltage (e (a)) via input resistors (R6, R4) having the same value, and the two inputs are added by the amplifier (A2) . Thus , the voltage of the full-wave rectification type (e (o))
An absolute value circuit comprising: an adder circuit (4) for forming.