JPS62101126A - Ripple eliminating circuit - Google Patents

Abstract

PURPOSE:To obtain a DC output while the ripple is eliminated by extracting an AC signal from an original signal and subtracting the extracted AC component from the original signal. CONSTITUTION:The AC component is extracted from the original signal outputted from an AC effective value/DC converting circuit 1 in an extracting circuit 2. The extracting circuit 2 consists of a capacitor 4 eliminating the DC component from the original signal and the 1st and 2nd resistors 5, 6. The original signal from the AC effective value/DC conversion circuit 1 is inputted to an inverting input of the operational amplifier 3, the AC component from the extracting circuit 2 is outputted to the non-inverting input of the operational amplifier 3 and an output subtracting the overlapped AC component from the original signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention is directed to converting an alternating current to a direct current, such as an AC effective value to direct current conversion circuit, and converting the direct current output into an original signal.
The present invention relates to a ripple removal circuit that is applied when digitally controlling various devices based on an original signal input to a /D converter.

(Prior art and its problems) In the original signal as described above, if an alternating current component is superimposed on the direct current component, so-called ripple is superimposed, and if the ripple is large, it may cause problems during A/D conversion. To,
Although it is at the "L" level, it is converted as the "■(" level, which has the disadvantage of causing a conversion error.

Therefore, in order to remove such ripples, conventionally, for example, the rectified output from a rectifier circuit that converts alternating current to direct current is smoothed by a smoothing capacitor and then extracted.

However, in the case of the conventional example having such a configuration, in order to better remove ripples, it is preferable to increase the capacity of the smoothing capacitor.
For example, as shown in Figure 3, when the amplitude of the alternating current input to the rectifier circuit is changed in order to finally obtain a predetermined "L" level or "H" level output as a digital output for control. In addition, if the capacitance of the smoothing capacitor is large, the response to amplitude changes will be poor, as shown by the broken line, and when performing highly accurate control in terms of time, "L"
, H" has the disadvantage of causing a shift in the switching timing, causing control errors. In order to reduce the shift in switching timing, it is possible to reduce the capacitance of the smoothing capacitor, but in this case, the ripple cannot be effectively removed.

That is, in the case where a smoothing capacitor is provided to remove ripples, ripple removal and control responsiveness are contradictory to each other, and both cannot be satisfied.

(Object of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to improve responsiveness by quickly removing ripples while being able to remove ripples well. do.

(Structure and Effects of the Invention) In order to achieve such an object, the present invention includes an extraction circuit that extracts an AC component from an original signal on which ripples are superimposed, and an extraction circuit that extracts an AC component and the original signal that are extracted by the extraction circuit. and a calculation means for subtracting the alternating current component from the original signal to produce a direct current output.

According to this configuration, by extracting the AC component from the original signal and subtracting the extracted AC component from the original signal, a DC output with ripples removed is obtained.

Therefore, since the ripple itself is extracted and the ripple is subtracted as is from the original signal, the ripple can now be removed reliably and satisfactorily.

Moreover, since ripples are only extracted and subtracted in order to remove ripples, ripples can be removed in an extremely short period of time without requiring a charging action unlike conventional smoothing capacitors. This has improved responsiveness and made it possible to perform highly accurate control when obtaining DC output for use.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings. FIG. 1 is an electrical circuit diagram of a ripple removal circuit according to an embodiment of the present invention. In this figure, ■ is the AC effective value - which outputs a DC signal proportional to the effective value of the AC signal.
A DC conversion circuit 2 is an extraction circuit that extracts an AC component from the original signal output from the AC effective value-DC conversion circuit 1, and 3 is an operational amplifier as a calculation means.

The extraction circuit 2 includes a capacitor 4 that removes a DC component from the original signal, and first and second resistors 5 and 6 that adjust the input gain of the extracted AC component to the operational amplifier 3 by voltage division. It is being

The original signal from the AC effective value to DC conversion circuit l is input to the inverting input terminal of the operational amplifier 3, and the AC component from the extraction circuit 2 is input to the non-inverting input terminal of the operational amplifier 3, and the original signal The output is obtained by subtracting the superimposed alternating current from the above.

and a fourth resistor.

This will be explained using ←→reference≠〒-4-.

First, the output V from the AC effective value-DC conversion circuit 1 is
If the DC component is Vd and the ripple component is Va, then v,=va+va, resulting in an output as shown in FIG. 2(a).

The voltage V applied to the non-inverting input terminal of the operational amplifier 3 has a resistance value R of each of the first and second resistors 5.6.
1, R2, then V 1 = V a X Rt / (R+ + R!
), resulting in an output as shown in FIG. 2(b).

Also, the resistance value of each of the third and fourth resistors 7.8 is R
j, R, the output voltage Vo from the operational amplifier 3 is Vow V +X R4/ R3+ V t(1+
Ra/R3)=(Vd+Va)XR
a / R3+ V aXCRs/(R++Rt))X
(1+R4/R3)=-VdxQ,/Q--cV r
o−y/p −↓ Q 'l/(R3×(RI+
R2)) a4/Rr] where R,/R,=R4
/R3, then RzX(Ra+R4)/(R*X(R
++Rt))-R,/rt3=0, and Vo=VdXR4/R3 is obtained.

That is, by adjusting the ratio of the resistance values of the first and second resistors 5.6, it is possible to obtain a DC output with completely eliminated ripples, as shown in FIG. 2(C).

The means for obtaining an output obtained by subtracting the alternating current component superimposed on the original signal from the original signal is not limited to the operational amplifier 3 as in the above-mentioned embodiment, but may also include, for example, a configuration combining transistors, etc.
Various modifications such as a field effect transistor are possible, and these are collectively referred to as the calculation means 3.

[Brief explanation of drawings]

≠--≠Mori--≠-1 FIG. 3 is a waveform diagram for explaining the operation of the conventional example. 2... Extraction circuit, 3... Operational amplifier as calculation means, 4... Capacitor, 5... First resistor as voltage dividing resistor, 6... Second resistor as voltage dividing resistor.

Claims (2)

[Claims] (1) An extraction circuit that extracts an alternating current component from an original signal on which ripples are superimposed, and inputs the alternating current component and the original signal extracted by the extraction circuit, and subtracts the alternating current component from the original signal to generate a direct current. and a calculation means for outputting an output. (2) The extraction circuit includes: a capacitor that removes a DC component from the original signal; and a voltage dividing resistor that adjusts the input gain of the AC component to the calculation means. The ripple removal circuit described in section.