JPS61260169A - Ac signal detecting circuit - Google Patents

Abstract

PURPOSE:To obtain an errorless detection signal by using a single low-voltage power source as the power source and performing the operation after raising an input signal to the + side in DC. CONSTITUTION:The AC input signal issued to an input terminal 1 is inputted to a primary-side winding 4 of a transformer T through a noise eliminating filter 2 and a level setter 3, and the step-down AC signal obtained in a secondary-side winding 5 is raised to the + side by a DC voltage Vref from a reference voltage generating circuit 6 to generate a signal Vdet to be detected. The signal Vdet is sampled by the fist A/D converter 8 and is converted to a digital signal V'det, and the level of the voltage Vref is converted to a digital signal V'ref by the second A/D converter 9. Signals V'det and the signal V'ref are inputted to an operating circuit 10, and the circuit 10 operates V'det-V'ref to output the output signal to a terminal 11. Thus,the errorless accurate detection signal is obtained for the AC input signal waveform.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is mainly applicable to AC output devices (for example, constant voltage electric
! (equipment) feedback w4m and various AC waveforms total 1
! II! The present invention relates to an AC signal detection circuit used in i, etc.

(Prior art) Conventionally, for example, Combicoke. Broadcasting equipment 0 Communication equipment, etc. N
Since N requires AT precision and reliability, a constant frequency constant voltage WI source device using an inverter is generally used, but in order to maintain this output stably, the output voltage must be controlled by an AC signal detection circuit. Feedback control is performed to detect and bring the voltage close to the set voltage value. The signal for performing this feedback control is generated by comparing the extracted AC output voltage converted into a DC voltage by a rectifying circuit and a smoothing circuit with a set voltage value.

The rectifier circuit used in such a place is usually a bridge type full-wave rectifier circuit including diodes Qa-[)d as shown in FIG.

By the way, when the output of the rectifier circuit is passed through the smoothing circuit, a time delay occurs, and there is a problem that the response of the feedback IIJ all is delayed. Therefore, in feedback systems that require high-speed response, instead of using a smoothing circuit, the output waveform of the rectifier circuit is sampled with an A/D converter and each sample value is converted to a digital signal to read the feedback information. something is being used. For processing the output of a rectifier circuit in this way, the rectified output waveform itself has an important meaning, so a rectifier circuit that outputs an accurate waveform is required.

[Problem to be solved]

In the rectifier circuit shown in Figure 3, the rectifier output voltage VQ
is the forward voltage drop of the diode f.

If the input IFBE is vl, then Vo -Vi -2Vf
As a result, the diode forward drop voltage Vf becomes an error, making it impossible to obtain an accurate rectified output waveform for the waveform of the input voltage v1 shown in Figure 4(a).
).

By the way, microcomputers and digital arithmetic circuits that make up the control system usually operate at low voltages (for example, +5V).
If a low-voltage single-I power source (0 and +) is used for the AC signal detection circuit, the diode forward drop voltage Vr (
For example, 0.7 V) causes a large detection error, and there is a problem that the influence of this error cannot be ignored.

The present invention has been made to solve the above problems. 1! It is an object of the present invention to provide an alternating current signal detection circuit that can obtain error-free detection signals when a source is used.

[Means for solving problems]

In order to achieve the above object, the AC signal detection circuit of the present invention stops the use of a rectifier circuit and transfers the AC signal to be detected (AC signal to be detected) shown in FIG. The AC signal obtained by stepping down to the secondary side is input to the DC current rfVr+J from the reference voltage generation circuit.
Lift it to the side to create a detection signal V det as shown in Figure 2 (tl), sample it, and obtain A , /
First A/D change t9 for D conversion! a second A/D converter that converts the level of the applied DC voltage Vref into an A/D converter; a second A/D converter that converts the level of the applied DC voltage Vref; A detection signal (alternating current signal level) is obtained using an arithmetic circuit which inputs the output signal Vref- of the A/D converter No. 2 and calculates Vdet--Vref-.

(Function) As described above, the AC signal detection circuit of the present invention has 'R'
Since the fIA uses a low-voltage single-m source and does not use a rectifier circuit, it is not possible to use the input AC signal as is for detection, and the DC signal is
By lifting (biasing) to the side and then performing arithmetic processing, a detection signal with no w4 difference is obtained.

〔Example〕

Next, there are 4 drawings regarding *embodiments of the present invention! I will refer to and explain.

FIG. 1 is a circuit diagram showing an embodiment of the AC signal detection circuit of the present invention. In the figure, 1 is an input terminal to which an AC input signal (AC signal to be detected) is applied, 2 is a noise removal filter, 3 is an input signal level setting circuit, and 4 is a transformer (T
)'s - next 轡榛, 5 is also the second M! line, 6 is the transformer (T
), and 7 is a level setting circuit for extracting a predetermined signal level. 8 is a first A/D converter which samples the detected signal yaet on which the DC voltage vref on the secondary side of the transformer is superimposed and converts it into a digital signal 11'. 9 is a second A/D converter which converts the level of the DC voltage V ref applied to the secondary side of the transformer into a digital signal @yrer'. 10 is an arithmetic circuit which receives the output signal of the first A/D converter ■det-
and the output signal V ref' of the second A,/D converter are input, the calculation of Vdet = -Vref - is performed, and a detection signal is output. Reference numeral 11 denotes an output terminal that outputs a detection signal (digital signal of the calculation result).

Diode D1. D2 is inserted to protect the A/D converter and arithmetic circuit when an abnormality occurs in the input signal voltage. Note that the level setting circuits 3 and 7 are not essential.

〔effect〕

As explained above, since the AC signal detection circuit of the present invention does not use a rectifier circuit, it is possible to obtain an accurate detection signal with no error in the waveform of the AC input signal (AC signal to be detected).

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an AC signal detection circuit according to the present invention. FIGS. 2(a) and 2(b) are explanatory diagrams of the operation of the circuit of the present invention.
a) shows the AC signal to be detected, (M shows the relationship between the signal to be detected and the detection signal. Fig. 3 is a circuit diagram of a conventional rectifier circuit,
Figure 4 is a waveform diagram of a conventional rectifier circuit; (a) is the input waveform;
(b) is the rectified output. T...Transformer, 4...Primary g of transformer! line. 5... Secondary IJ line of transformer, 6... Reference voltage generation circuit, 8... First A/D converter, 9... Second A/D converter, 10...
...Arithmetic circuit.

Claims (1)

[Claims] 1. A transformer to which the AC signal to be detected is input, a reference voltage generation circuit that applies a predetermined DC voltage Vref to the secondary side of the transformer, and a reference voltage generation circuit that applies the DC voltage Vref to the secondary side of the transformer. The obtained detected signal Vdet is sampled and A
a first A/D converter that performs /D conversion, a second A/D converter that performs A/D conversion of the level of the applied DC voltage Vref, and an output signal of the first A/D converter. An AC signal detection circuit comprising an arithmetic circuit that inputs Vdet' and the output signal Vref' of the second A/D converter, calculates Vdet'-Vref', and outputs a detection signal.