JPH01110265A - Waveform processing circuit - Google Patents

Abstract

PURPOSE:To remove the effect of an input offset component in the processing of a waveform using an amplifier, by detecting input offset voltage and canceling offset using said offset voltage. CONSTITUTION:An input signal is converted to forward and reverse waveform signals by a full-wave rectifying circuit and the peak values of the respective signals are calculated by a peak detection circuit 200 and the difference therebetween is further obtained by a subtractor circuit 300. This difference is twice offset voltage. When the output obtained by reducing said difference to 1/2 is inputted to a cancel circuit 500 as offset detection output from a 1/2 output generating circuit 400, offset is canceled from the input signal containing offset to obtain a processed signal.

Description

[Detailed Description of the Invention] [Summary] Regarding a waveform processing circuit suitable for use in a circuit that handles an input that may have an offset, such as a full-wave rectifier circuit, the present invention provides a waveform processing circuit that cancels the offset of a periodic function waveform input. For the purpose of
A peak detection circuit that detects the peak value of the inverted waveform, a subtraction circuit that obtains the difference between each peak value, a 1/2 output generation circuit that reduces the output of this subtraction circuit to 1/2, and this 1/2 output. and a cancellation circuit that uses the output of the generation circuit to remove the offset of the reference level in the input signal and outputs a psychic signal.

[Industrial application field]

The present invention relates to a waveform processing circuit suitable for use in a circuit that handles an input that may have an offset, such as a full-wave rectifier circuit.

[Conventional technology]

When dealing with a periodic function waveform such as a sine wave, there are cases where the waveform has an offset. When the input waveform has an offset, when the input is amplified by an amplifier,
The signal is amplified to the offset amount and extracted.

[Problem that the invention seeks to solve]

However, amplification to the extent of the offset is not a desirable state in terms of waveform processing.

Figures 5(a) and 5(b) show the input and output waveforms of the full-wave rectifier circuit when there is an input offset;
If the input sine wave has an offset as shown in (a), the peak values of the normal wave and the inverted wave are different as shown in (b) of the same figure (the difference in peak value is 2 times the input offset voltage VOIPF).
vO〃), and the absolute value amplification circuit (
In the case of a circuit that outputs the absolute value of an input voltage as a voltage of the same polarity regardless of its polarity, its function as an absolute value amplifying circuit is impaired.

An object of the present invention is to provide a waveform processing circuit that cancels the offset of a periodic function waveform input.

One household at a time [Means for solving problems] This will be explained with reference to FIG. 1, which is a diagram of the principle of the present invention.

The waveform processing circuit according to the present invention processes an input signal that is repeatedly photographed on the positive side and negative side with respect to a reference level, respectively.
It has a full-wave rectifier circuit 100 that inverts and rectifies the signal, and a peak detection circuit 200 that detects the peak value of a normal and two-inverted waveform signal that is the output of the full-wave rectifier circuit 100 is connected to the full-wave rectifier circuit 100. Enter. Then, a subtraction circuit 300 obtains the difference between each peak value, and the output of this subtraction circuit 300 is divided into 1/
A 1/2 output generating circuit 400 which converts the output voltage into 2 is connected sequentially.

Furthermore, a cancellation circuit 500 is connected which uses the output of the 1/2 output generation circuit 400 to remove the offset from the input signal and outputs a processed signal. 100 is converted into a normal rotation 9 inversion waveform signal, and each peak value is detected by a peak detection circuit 200.
The subtraction circuit 300 further obtains the difference. This difference is twice the offset voltage. This difference is 1/2
If the resulting output is input from the 172 output generation circuit 400 to the cancellation circuit 500 as an offset detection output, the offset is canceled from the input signal including the offset and processed to obtain a ratio signal.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In this embodiment, a sine wave signal is supplied to the input terminal IN in FIG. Each circuit in FIG. 2 is indicated by the same reference numeral as in the diagram of the invention principle in FIG. 1, and this waveform processing circuit is a full-wave rectifier circuit 1.
00, a peak detection circuit 200, a subtraction circuit 300,
It includes a main output generation circuit 400 and a cancellation circuit 500 which is a full-wave rectification circuit.

In FIG. 2, the full-wave rectifier circuit 100 includes an operational amplifier (
OP amplifiers) 11 to 13, and MOS transistors 14.
15 and resistors 16 to 19. OP amplifier 11.1
2 constitute an inverting amplifier circuit and a non-inverting amplifier circuit, respectively. The inverting input terminal of the OP amplifier 11 is connected to the input terminal IN via the resistor 16, and the non-inverting input terminal is grounded.

A feedback resistor 17 is connected between the output terminal and the inverting input terminal, and the output terminal is connected to the non-inverting input terminal of the OP y 13. Also, OP amplifier 13
0 inversion input terminal is grounded, and its output terminal is connected to each MO8)
It is connected to the gates of transistors 14 and 15.

An inverting input terminal of the OP amplifier 12 is grounded via a resistor 18, a feedback resistor 19 is connected between the OP amplifier 12 and the output terminal, and a non-inverting input terminal is connected to the input terminal 10.

The peak detection circuit 200 includes a MOS transistor 21゜2.
2 and capacitors 23 and 24. Full wave rectifier circuit 1
00 NMO8) Sources of transistor 14 and PMOS transistor 15 2. Between the drains is N of the peak detection circuit.
MO8) The sources and drains of transistors 21 and 22 are connected in cascade, respectively, and the output terminals of OP Angs 11 and 12 are connected to these MOS transistors 14, 21 and 15.
22 to one end of each capacitor 23, 24, and the other end of each capacitor 23, 24 is grounded.

The subtraction circuit 300 includes an operational amplifier 31 and resistors 32 to 35.
It consists of An inverting input terminal of the OP amplifier 31 is connected to one end of a capacitor 23 via a resistor 32, and a feed pump resistor 33 is connected between the output terminal and the inverting input terminal. The non-inverting input terminal is connected to one end of the capacitor 24 via a resistor 34'lr, and is also grounded via a resistor 35.

The output terminal of the OP amplifier 31 is grounded via these resistors 30 and 31. In this embodiment, the full-wave rectifier circuit 1 and the full-wave rectifier circuit 1 shown in FIG. Similar OP amplifiers 51 to 53,
A full-wave rectifier circuit consisting of MOS transistors 54 and 55 and resistors 56 to 59 is used.

The output terminal 0UT1 of the 1/2 output circuit 400 is connected to a non-inverting input terminal of an OP amplifier 51 and an inverting input terminal of an OP amplifier 52 via a resistor 58, respectively. M.O.
The S transistors 54 and 55 are connected to an output terminal 0UT2 from which the full-wave rectified output of the full-wave rectifier is taken out.

When a sine wave signal is input to the input terminal IN, the input signal is inverted and normalized by the full-wave rectifier circuit 1 (300 inverting amplifier circuit and non-inverting amplifier circuit, respectively, and these are inverted and normalized by the OP amplifier 13
The MOS transistor 14 is turned on and off by the output of
．． 15, each positive half wave is taken out and supplied to the peak detection circuit 200. In the peak detection circuit 200, the positive half waves of the respective inverted and forward waveforms are connected to capacitors 23 and 24 via MOS transistors 21 and 22e.
Therefore, the input sine wave signal has an offset voltage of 1 voltage VOPF as shown in FIG.
nωt+ VOFF
), the waveform is shown in (c), and the capacitor 24.2
The peak output v+2, v2 obtained in 3 is shown in the same figure (d
), the waveform will be as shown in (e). input is A s
When inωt+Voη, the normal rotation side h A +
On the inversion side, A-VoFF is detected as the peak value.

The subtraction circuit 300 calculates the difference between the peak values of the waveforms of both the normal rotation and the inversion.
Detect. The peak values are A + Vovt, respectively.
If A - VOFF, is the difference A + VOFF? -(A
−VOFF ) = 2 Voff (Fig. 3 (
f)), by halving the offset voltage VO
becomes FF (see figure (g)) 0 In the cancellation circuit 500, such a detection output VO1
77 as the reference voltage, the offset voltage Voyyk can be canceled from the input sine wave, and the output terminal 0U
At T2, a full-wave rectified output as shown in FIG. 3(h) is obtained.

Since the full-wave rectified output from which the offset has been removed can be detected after the off period (see Figure 3 (g)), offset cancellation is also performed from this point (Figure 3 (h)).
Reference) 0 FIG. 4 shows another embodiment. In this embodiment, diodes D and D6 are used in the full-wave rectifier circuit and the peak detection circuit. Components similar to those in FIG. 2 are given the same reference numerals. In addition, in FIG. 4, 61 to 64 are operational amplifiers,
65 to 74 are resistors.O The excitation in this example is basically the same as the case in FIG. direction, the waveform of the circuit in Figure 4 is as shown in Figure 3 (a
) All waveforms other than the input Vin have reversed polarity.

〔Effect of the invention〕

According to the present invention, even if there is an offset in the input waveform, it is possible to detect the input offset voltage and cancel the offset voltage using this offset voltage, and in the case of waveform processing using an amplifier. This is effective when performing waveform processing because the input offset is not amplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the invention. Fig. 2 is a circuit diagram showing a specific example, Fig. 3 is a waveform diagram of each part of Fig. 2, Fig. 4 is a circuit diagram showing another embodiment, and Fig. 5 is a diagram explaining conventional problems. 0 100...Full wave rectifier circuit, 200...
Peak detection times 500...Cancellation circuit.

Claims (1)

[Claims] A full-wave rectifier circuit (100) that rectifies input signals that repeatedly oscillate on the positive side and negative side with respect to a reference level by respectively forwarding and inverting them, and detecting the peak values of these forward and inverted waveforms. A peak detection circuit (200), a subtraction circuit (300) that obtains the difference between each peak value, a 1/2 output generation circuit (400) that reduces the output of this subtraction circuit to 1/2, and this 1/2 output generation circuit (400). A waveform processing circuit comprising: a cancellation circuit (500) that uses the output of the circuit (400) to output a signal obtained by removing a reference level offset in the input signal.