JPH0136141Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Technical field of the invention This invention is a simple method for rectifying ripple components included in the rectified output when an AC power source with a certain frequency range is rectified by a rectifier circuit with frequency characteristics. It is about the technology of detecting by configuration.

(b) Conventional techniques and problems When measuring the level of an AC signal using a level meter, etc., the AC signal is amplified, then rectified by a rectifier circuit, and the input level is indicated to an indicator. In this case, when the input signal changes from low frequency to high frequency, it will be affected by the frequency characteristics of the rectifier circuit.

Next, the configuration of a rectifier circuit according to the prior art will be explained with reference to FIG.

In FIG. 1, 1 is an AC power source, 2 is a rectifier circuit, and 3 is an output terminal.

The rectifier circuit 2 includes a diode 21, a resistor 22, and a smoothing capacitor 23.

When the frequency of AC power supply 1 is high, it is sufficiently smoothed by resistor 22 and capacitor 23, so terminal 3
There are few ripple components that appear in .

When the frequency of the AC power supply 1 becomes low, for example below 100Hz, it is no longer possible to achieve sufficient smoothness with only the resistor 22 and capacitor 23, and the terminal 3
The ripple component included in the rectified output becomes larger.

In order to reduce this ripple component, the capacitance of the capacitor 23 can be increased, but if the capacitance of the capacitor 23 is increased, the time constant of the resistor 22 and the capacitor 23 becomes larger, and it takes a considerable amount of time for the rectified output to stabilize. It starts to take a while.

Recently, an increasing number of level meters are using AD converters to display the input level digitally.

In this case, the rectified output of terminal 3 in Figure 1 should be
AD convert.

FIG. 2 is an explanatory diagram of such AD conversion for a level meter.

P ₁ , P ₂ , and P ₃ in FIG. 2 are sample points on the rectified output, and the sampling levels of the points P ₁ , P ₂ , and P ₃ are L ₁ , L ₂ , and L _{3 ,} respectively.

As is clear from FIG. 2, as the ripple component increases, the sampling level differs depending on the sampling position, resulting in an error in level display.

In order to reduce the sampling error as shown in FIG. 2, the number of sampling points should be increased only when the ripple component increases, and the average of these sampling levels should be taken.

To this end, it is sufficient to detect that the ripple component has exceeded the indication error of the level meter and to switch the AD conversion.

(c) Purpose of the invention This invention connects the rectified output of the rectifier circuit 2 to the first input terminal of the comparator, and
Extract only the ripple component of , amplify it with an amplifier, rectify the output of this amplifier with another rectifier circuit, connect this rectified output to the second input terminal of the comparator,
The ripple component of rectifier circuit 2 increases, and the second
When the level of the input terminal exceeds the level of the first input terminal of the comparator, the comparator outputs an output, detects the ripple component of the rectifier circuit, switches AD conversion with the detected output, and detects the ripple component due to the ripple. The purpose is to reduce the level meter reading error.

(d) Example of the invention Next, a configuration diagram of an example of this invention is shown in FIG. 3.

In FIG. 3, 4 is a comparator, 5 is a capacitor, 6 is an amplifier, 7 is a rectifier circuit, and 8 is an output terminal, and the other parts are the same as in FIG. 1.

The comparator 4 compares the voltages of two input signals, and generates a binary voltage as an output depending on whether another input voltage is larger or smaller than one reference voltage.

In FIG. 3, input terminal 4A of comparator 4 is connected to terminal 3.
The rectified output of the rectifier circuit 2 is connected to the rectifier circuit 2.

The rectified output of terminal 3 corresponds to the reference voltage of comparator 4.

The capacitor 5 is used for blocking direct current to take out only the ripple component from the terminal 3.

The ripple component taken out by capacitor 5 is
The signal is amplified by an amplifier 6, and the output of the amplifier 6 is connected to a rectifier circuit 7.

The rectifier circuit 7 includes a diode 7A and a capacitor 7.
The capacitor 7B is for smoothing.

The output of the rectifier circuit 7 is connected to the other input terminal 4B of the comparator 4.

The output of the rectifier circuit 7 corresponds to the input voltage of the comparator 4.

Therefore, the frequency of AC power supply 1 becomes lower,
If the ripple component increases and the output of the input terminal 4B becomes larger than the input terminal 4A of the comparator 4, the output of the comparator 4 can be set to "1". ” appears, which indicates that the ripple component has increased.

For example, the voltage at input terminal 4A of comparator 4 is 0.5
If you set it in the range of ~10V, if the voltage at input terminal 4B of comparator 4 exceeds this set voltage, comparator 1 will output "1", indicating that the ripple component has exceeded a certain value. .

(e) Effect of the invention According to this invention, the output of the first rectifier circuit is connected to the first input terminal of the comparator, and
Since only the AC component is extracted from the output of the rectifier circuit and amplified, and the amplified output is rectified by the second rectifier circuit and connected to the second input terminal of the comparator, the ripple component of the first rectifier circuit is When the voltage at the second input terminal of the comparator exceeds the voltage at the first input terminal, the comparator outputs an output, indicating that the ripple component of the first rectifier circuit has increased.

Therefore, the output of the comparator can be used in a level meter or the like based on AD conversion, thereby reducing indication errors.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a rectifier circuit according to the prior art, FIG. 2 is an explanatory diagram of AD conversion for a level meter, and FIG. 3 is a block diagram of an embodiment of this invention. 1... AC power supply, 2... Rectifier circuit, 3... Output terminal, 4... Comparator, 5... Capacitor, 6...
Amplifier, 7... Rectifier circuit, 7A... Diode,
7B... Capacitor, 8... Output terminal, 21...
Diode, 22...resistor, 23...capacitor.

Claims (1)

[Claims for Utility Model Registration] When rectifying a variable frequency AC power source 1 with a first rectifier circuit 2 having frequency characteristics, a capacitor 5 connected to the output of the first rectifier circuit 2 and extracting only ripple components. , an amplifier 6 whose input is the output of the capacitor 5, and a second rectifier circuit 7 connected to the output of the amplifier 6.
and the output of the first rectifier circuit 2 is connected to the first input terminal 4A.
and a comparator 4 in which the output of the second rectifier circuit 7 is connected to the second input terminal 4B, and the voltage at the second input terminal 4B is connected to the first input terminal 4.
A ripple level detection circuit characterized in that when the voltage becomes higher than the voltage of A, an output is output from the comparator 4.