JPH0245371B2 - 9PISOKAIRO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a 90° phase shift circuit that outputs an analog voltage that is phase shifted by 90° from an analog input voltage.

[Conventional technology]

In direct display type capacitor testing equipment, transformer testing equipment, etc., the error component is divided into an in-phase component and a quadrature component.
Or a ratio error is used, and the quadrature component is a capacitance error or a phase angle. In order to extract the signal corresponding to this quadrature phase component, a test voltage and a quadrature reference voltage are required, and a circuit to obtain this voltage is required.
It is a 90° phase shift circuit.

Such 90° phase shift circuits include those using CR as shown in Figures 1 and 2, and those using CR as shown in Figures 1 and 2.
A differentiating circuit as shown in the figure or an integrating circuit as shown in FIG. 4 is used.

The one shown in Figure 1 is called a Toulon circuit, and the one shown in Figure 2 is an operational amplifier.
This is an all-pass circuit using OP.

[Problem to be solved by the invention]

The one using CR shown in Figures 1 and 2 is
When the input frequency changes, although the amplitude remains constant, the phase changes, so there is a drawback that the only condition for a 90° phase shift is when 2πfCR=1, where f is the frequency.

In addition, in the differentiating circuits and integrating circuits shown in Figures 3 and 4, when the input frequency changes, the phase angle changes.
Although the angle is maintained at 90°, the disadvantage is that the amplitude changes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a 90° phase shift circuit that maintains a 90° phase shift even when the frequency of an input signal changes, and the amplitude of the voltage remains constant.

[Means to solve the problem]

To achieve the above object, the present invention includes a clock generator in a 90° phase shift circuit that generates an analog output signal that is 90° phase shifted from an analog input signal using a differentiating circuit or an integrating circuit. a digital counter that counts the clock from the clock generator according to the analog input signal and measures the period or frequency of the analog input signal; and a coefficient unit that obtains a coefficient according to the value measured by the digital counter. , a gain adjustment circuit comprising an operational amplifier whose gain is adjusted according to the coefficient in cooperation with the coefficient multiplier; A 90° phase shift circuit is provided, characterized in that the gain adjuster is controlled according to a measured value of a counter.

[Effect]

A clock generator included in the digital counter generates a clock signal. When an analog input signal is applied to the digital counter, the digital counter counts the clock signal during a period in which a signal determined according to the frequency of the analog input signal is applied, and uses this as a measurement value. This measured value is applied to a coefficient multiplier in the gain adjuster, and the output of this coefficient multiplier is applied as a coefficient to an operational amplifier. As a result, the operational amplifier performs multiplication according to this coefficient. Therefore, when the frequency of the signal to be phase-shifted changes,
The gain adjuster changes the magnitude of the output signal accordingly.

This change corresponds to the situation where the differentiating circuit or the integrating circuit changes the amplitude in accordance with the change in frequency. Therefore, when the frequency of the analog input signal increases or decreases and the amplitude of the output voltage of the differentiating circuit or the integrating circuit changes, the gain adjuster performs amplitude correction to compensate for this. A 90° phase-shifted output with constant amplitude is produced regardless of frequency changes.

〔Effect of the invention〕

In the present invention, the frequency or period of the analog input signal is measured using a digital counter, and this measured value is applied to the gain adjuster to correct the amplitude of the signal phase-shifted by 90 degrees. The amplitude of the 90° phase-shifted signal can be maintained constant even if the signal changes. Therefore, it is possible to provide a circuit that is particularly effective for automatic measurement circuits and the like in alternating current.

Since the circuit of the present invention is serially controlled,
It is extremely stable and has the advantage of not causing hunting even when combined with other circuits.

〔Example〕

FIG. 5 shows an embodiment of the present invention.
The 90° phase shift circuit is an operational amplifier with a capacitor C as an input element and a resistor R as a feedback element.
It has a differentiator circuit 1 consisting of OP1. On the input side of the differentiating circuit 1, a coefficient multiplier 2 and a digital counter 3 for measuring the frequency or period of the analog input voltage are provided. The digital counter 3 has a built-in clock circuit (not shown) and counts the clock according to the frequency or period of the analog input signal. Digital counter 3
The count value is a measured value of the frequency or period of the analog input signal, and this measured value is given to the coefficient multiplier 2.

As a result, the coefficient unit 2 converts the digital counter 3
Obtain the coefficient corresponding to the measured value from. Therefore, from the input terminal to the operational amplifier OP2 via the coefficient unit 2
The analog input voltage applied to the converter varies depending on the frequency. The output of the operational amplifier OP2 is then given to the differentiating circuit.

In this circuit, now the analog input voltage V2
Suppose that the frequency of increases. In this case, the output voltage of the differentiating circuit 1 becomes high. Therefore, the operational amplifier
OP2 output needs to be low. As the frequency of the analog input voltage increases, the period measured by the digital counter 3 decreases in inverse proportion to the frequency. Therefore, the measured value of the digital counter 3 becomes small, and the coefficient multiplier 2, which indicates a coefficient corresponding to this measured value, produces a small output corresponding to the height of the frequency.

The input voltage of the differentiating circuit 1 becomes smaller as the frequency increases, but the differentiating circuit 1 produces a larger output voltage as the frequency becomes higher. Therefore, the input voltage V
2 and the output voltage V2', it is found that the change in voltage amplitude caused by the increase or decrease in frequency in the differentiating circuit 1 is canceled by the coefficient change in the coefficient unit 2, and in the end, the relationship between the input voltage and the output voltage is always constant. be done.

FIG. 6 shows another embodiment of the present invention,
This uses an integrating circuit 4 constituted by an operational amplifier OP4 having R as an input element and C as a feedback element.

The output voltage of the integrating circuit 4 is inversely proportional to the frequency of the input voltage. Therefore, the frequency is measured by measuring the analog input voltage for a certain period of time with the digital counter 3 and measuring the clock during that period, and the coefficient unit 2 has a coefficient corresponding to this measured value. This allows a configuration similar to that shown in FIG. 5 to be achieved. However, in order to reduce the time required for control even when the frequency of the input voltage V2 is low, an operational amplifier OP20 is connected between the input and output of the coefficient multiplier 2, and a resistor R is used as an input element.
20 to constitute a division circuit.

[Other Examples]

The arrangement order of the differentiating circuit 1 and the coefficient multiplier 2 in the circuit configuration of FIG. 5 may be reversed so that the differentiating circuit 1 performs differentiation and then the coefficient multiplier 2 performs control. Furthermore, the order of the integrating circuit 4 and the coefficient multiplier 2 in FIG. 6 may be reversed.

When measuring input signals, it is faster to measure the period for low frequencies, and it is faster to measure the frequency for high frequencies, so they can be used appropriately.

This distinction can be easily made with a normal switching type digital counter.

[Brief explanation of drawings]

Figures 1 and 2 show a conventional system using a CR circuit.
A circuit diagram showing an example of a 90° phase shift circuit, FIG. 3 is a diagram showing the configuration of a differentiating circuit, FIG. 4 is a diagram showing the configuration of an integrating circuit, and FIG. 5 is a circuit diagram showing an example of the present invention. ,
FIG. 6 is a circuit diagram showing another embodiment of the present invention. 1...Differentiating circuit, 2...Coefficient unit, 3...Digital counter, 4...Integrator circuit, OP...Operation amplifier, R...
Resistance, C...capacitor, V...voltage.

Claims (1)

[Claims] 1. Producing an analog output signal that is 90° phase shifted from the analog input signal using a differentiating circuit or an integrating circuit.
In a 90° phase shift circuit, a digital circuit having a clock generator is provided with an analog input signal, and measures the period or frequency of the analog input signal by counting the clocks from the clock generator according to the analog input signal. A gain adjustment circuit comprising a counter, a coefficient multiplier that obtains a coefficient according to a value measured by the digital counter, and an operational amplifier whose gain is adjusted according to the coefficient in cooperation with the coefficient multiplier; A 90° phase shift circuit, characterized in that the gain adjuster is controlled in accordance with the measured value of the digital counter so that the amplitude of the analog output signal phase-shifted by 90° is constant.