JPH0897688A - Clamp circuit for triangle wave signal - Google Patents

Abstract

PURPOSE: To realize clamping with an excellent temperature characteristic and high accuracy by setting a negative peak level of a triangle wave signal of an output signal of an integration circuit to a setting potential when a transistor (TR) is conductive by a differentiation signal of a differentiation circuit and obtaining a clamped triangle wave signal to the setting potential at an output of a DC block capacitor. CONSTITUTION: An integration circuit 2 and a differentiation circuit 4 generating a triangle wave signal are connected to an output side of a square-wave signal oscillator 1. The differentiation circuit 4 is made up of resistors R3, R4 and a capacitor C4. When a TRQ1 is turned on by a differentiation signal of the differentiation circuit 4, a negative peak of a triangle wave signal of an output signal of the integration circuit 2 is forcibly set to a prescribed potential and a charge equivalent to a difference between the set potential and a voltage being a half of a peak-to-peak voltage Va is charged in a DC blocking capacitor C2. Thus, a triangle wave signal clamped to the setting potential is obtained at the output side of the capacitor C2. When a load impedance of the clamp circuit is light, no buffer amplifier A1 is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triangular wave signal clamp circuit for fixing the peak of a triangular wave signal used as a pulse width modulated carrier signal to an arbitrary DC potential.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram showing an example of a conventional clamp circuit for a triangular wave signal. In FIG. 6, 1 is a square wave signal oscillator, 2 is an integrating circuit composed of a resistor R1 and a capacitor C1, C2 is a DC blocking capacitor, 3 is a voltage source for clamping, D1 is a diode, and A1 is a buffer amplifier. In the circuit of FIG. 6, the square wave signal from the square wave signal oscillator 1 is integrated by the integrating circuit 2 and converted into a triangular wave signal, which is supplied to the DC blocking capacitor C2. A clamp voltage is applied to the output side of the DC blocking capacitor C2 from the clamping voltage source 3 via the diode D1, and an output with the peak of the triangular wave signal clamped can be obtained at the output side of the DC blocking capacitor C2.

[0003]

By the way, when the peak of the triangular wave signal is clamped, the impedance for charging the DC blocking capacitor C2 is the impedance ZD of the diode D1 and has a certain value, so that a good clamping characteristic is obtained. To obtain the above, the value of the DC blocking capacitor C2 cannot be increased so much. Therefore, the clamped triangular wave signal output on the output side of the DC blocking capacitor C2 needs to be received with a very large impedance, and in most cases, the buffer amplifier A1 must be connected to the output side of the DC blocking capacitor C2. Further, since the clamp voltage V1 becomes (the output voltage V0 of the clamp voltage source 3 + the forward drop voltage V2 of the diode D1), in order to keep the temperature characteristics of the clamp voltage V1 good, the forward drop of the diode D1 is performed. In order to compensate the temperature characteristic of the voltage V2, it is necessary to give the output voltage V0 of the clamping voltage source 3 a temperature characteristic opposite to that of V2. For this reason,
The die D2 is connected. (Usually, the amplitude of the triangular wave signal is often used with a small value, and it is necessary to take the temperature characteristic of the forward drop voltage V2 of the diode D1 into consideration.)

An object of the present invention is to provide a clamp circuit for a triangular wave signal that does not require a buffer amplifier when the load connected to the output side is relatively light and does not require temperature compensation.

[0005]

A clamp circuit for a triangular wave signal according to the present invention comprises a square wave signal generating means, a converting means for converting a square wave signal from the square wave signal generating means into a triangular wave signal, and the converting means. A DC blocking capacitor connected to the output side of the means, a differentiating circuit for differentiating the square wave signal from the square wave signal generating means, a first electrode connected to the output side of the differentiating circuit, and a second electrode Is composed of a switching transistor connected to the output side of the DC blocking capacitor and a clamp voltage source connected to the third electrode of the switching transistor, and the voltage of the clamp voltage source is changed from the output side of the DC blocking capacitor to It is configured to obtain a clamped triangular wave signal.

The first, second and third electrodes of the switching transistor are a base, a collector and an emitter, respectively. Further, the converting means is an integrating circuit including a resistor and a capacitor, and its integration time constant is set to be larger than the differentiation time constant of the differentiating circuit. The clamp voltage source may be ground potential or DC positive potential, and an inverting circuit may be connected between the square wave signal generating means and the converting means.

[0007]

The square wave signal from the square wave signal generating means is converted into the triangular wave signal by the converting means, and the clamp voltage is applied to the triangular wave signal through the switching transistor which is turned on / off by the differential output obtained by differentiating the square wave signal. As a result, an output obtained by clamping the negative or positive peak of the triangular wave signal with an arbitrary clamp voltage is obtained.

[0008]

1 is a circuit diagram showing an embodiment of a clamp circuit for a triangular wave signal according to the present invention. As shown in FIG. 1, an integrating circuit 2 and a differentiating circuit 4 for producing a triangular wave signal are connected to the output side of the square wave signal oscillator 1. The differentiating circuit 4 is composed of resistors R3 and R4 and a capacitor C4, and its differential time constant is set to a value smaller than the integral time constant of the integrating circuit 2. The output of the differentiating circuit 4 is the base of the NPN transistor Q1 which is turned on at the rising portion of the square wave signal oscillator 1 in order to fix the negative peak value of the triangular wave signal to a certain DC potential (ground potential in FIG. 1). Is connected to the output side of the DC blocking capacitor C2 connected in series to the output side of the integrating circuit 2, and the emitter is connected to an arbitrary DC potential (ground potential in FIG. 1). A buffer amplifier A1 is connected to the output side of the DC blocking capacitor C2, if necessary. Although not shown in FIG. 1, if the output impedance of the integrating circuit 2 is not too low, the integrating circuit 2 and the DC blocking capacitor C
A buffer amplifier may be connected between the two. This is Figure 6
The same applies to the conventional example.

2A and 2B show signal waveforms of respective portions of the circuit of FIG. 1, where FIG. 2A is an output signal of the square wave signal oscillator 1, FIG. 2B is an output signal of the integrating circuit 2, and FIG. The differential signal, (d), is the output signal of the DC blocking capacitor C2. The differential signal (c) of the differential circuit 4 causes the transistor Q
When 1 is turned on, the negative peak of the triangular wave signal of the output signal (b) of the integrating circuit 2 is forcibly pulled to the ground potential, and the DC blocking capacitor C2 has a DC potential of point (b) and Va / 2. A charge corresponding to the difference in DC potential is charged. Here, Va is the peak-to-peak of the triangular wave signal (b).
It is the peak voltage. Therefore, the DC blocking capacitor C
At the output side of 2, a triangular wave signal (d) clamped to the installation potential is obtained. Thereafter, the same operation is repeated each time the square wave signal from the square wave signal oscillator 1 rises, and an output fixed or clamped to a constant DC potential having a negative peak of the triangular wave signal is obtained.

Next, FIG. 3 is a circuit diagram of another embodiment of the clamp circuit for the triangular wave signal according to the present invention. In FIG. 3, the positive output voltage V0 of the clamping voltage source 3 is applied to the emitter of the transistor Q1. Therefore, in this case, the triangular wave signal clamped to the positive output voltage V0 of the clamping voltage source 3 can be obtained at the output side of the DC blocking capacitor C2. The positive output voltage V0 of the clamping voltage source 3 can be made variable.

FIG. 4 is a circuit diagram of still another embodiment of the clamp circuit for the triangular wave signal according to the present invention. In FIG. 4, an inverting circuit A is provided between the square wave signal oscillator 1 and the integrating circuit 2.
2 are connected. In this case, the signal waveform of each part is as shown in FIG. 5, and an output in which the positive peak of the triangular wave signal is clamped to the ground potential can be obtained. In addition, although the NPN transistor is used as the switching transistor in the circuits of FIGS. 1, 3, and 4, it is also possible to adopt a circuit configuration using the PNP transistor.

[0012]

According to the triangular wave signal clamp circuit of the present invention, the following effects can be obtained. (1) When the load impedance of the clamp circuit for the triangular wave signal is relatively light, the buffer amplifier can be eliminated. (2) A clamp with high temperature characteristics and high accuracy can be realized. (3) The circuit configuration is simple.

[Brief description of drawings] [Explanation of symbols]

 1 square wave signal oscillator 2 integrating circuit 3 voltage source for clamping 4 differentiating circuit C2 DC blocking capacitor Q1 switching transistor

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[Procedure amendment]

[Submission date] November 9, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a clamp circuit for a triangular wave signal according to the present invention.

FIG. 2 is a signal waveform diagram of each part of the circuit of FIG.

FIG. 3 is a circuit diagram showing another embodiment of the clamp circuit for the triangular wave signal according to the present invention.

FIG. 4 is a circuit diagram showing still another embodiment of the clamp circuit for the triangular wave signal according to the present invention.

5 is a signal waveform diagram of each part of the circuit of FIG.

FIG. 6 is a circuit diagram showing an example of a conventional clamp circuit for a triangular wave signal.

[Explanation of symbols] 1 square wave signal oscillator 2 integrating circuit 3 voltage source for clamping 4 differentiating circuit C2 DC blocking capacitor Q1 switching transistor

Claims (7)

[Claims] 1. A square wave signal generating means, a converting means for converting a square wave signal from the square wave signal generating means into a triangular wave signal, a DC blocking capacitor connected to an output side of the converting means, and the square shape. A differentiating circuit for differentiating the square wave signal from the wave signal generating means, a first electrode connected to the output side of the differentiating circuit, and a second electrode connected to the output side of the DC blocking capacitor. A clamp voltage source connected to the third electrode of the switching transistor, and is configured to obtain a triangular wave signal clamped to the voltage of the clamp voltage source from the output side of the DC blocking capacitor. A characteristic triangular wave signal clamp circuit. 2. The clamp circuit according to claim 1, wherein
The first, second and third electrodes of the switching transistor are a base, collector and emitter clamp circuit for a triangular wave signal. 3. The clamp circuit according to claim 1, wherein
The conversion means is a clamp circuit for a triangular wave signal, which is an integration circuit composed of a resistor and a capacitor. 4. The clamp circuit according to claim 3, wherein
Clamp circuit for triangular wave signal, where the integration time constant of the integration circuit is set to be larger than the differentiation time constant of the differentiation circuit. 5. The clamp circuit according to claim 1, wherein
The clamp voltage source is a clamp circuit for a triangular wave signal that is at ground potential. 6. The clamp circuit according to claim 1, wherein
The clamp voltage source is a clamp circuit for a triangular wave signal with a DC positive potential. 7. The clamp circuit according to claim 1, wherein:
A clamp circuit for a triangular wave signal in which an inverting circuit is connected between the square wave signal generating means and the converting means.