JPS6220485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a modulation/demodulation circuit that uses an inductosyn to obtain a signal that changes sinusoidally depending on the rotation angle.

FIG. 1 is a circuit diagram showing a conventional modulation/demodulation circuit. In the figure, 1 is a voltage source that outputs a reference voltage, 2 is an oscillator that outputs a carrier signal, 3 is a modulation circuit that modulates the input voltage with the carrier signal,
4 is a drive circuit, 5 is a resonant capacitor, 6a and 6b are rotating transformer coils, 7a, 7b and 7c are inductosin printed conductors, 8a
and 8b are load resistances, 9a, 9b, 9c and 9d are amplifiers, 10a and 10b are demodulation circuits that demodulate input signals with the resonant output of the resonant circuit formed by the resonant capacitor 5 and coil 6a, and 11a and 11b are synchronized It is a capacitor.

The operation in the above configuration will be explained. First, the modulation circuit 3 modulates the reference voltage output from the voltage source 1 with the carrier signal output from the oscillator 2.
A drive circuit 4 amplifies the modulated output and outputs it to a capacitor 5 and a coil 6a. This causes the capacitor 5 and the coil 6a to resonate. This change in the current flowing through the coil 6a causes an induced current to occur in the coil 6b, and this induced current flows through the printed conductor 7a, so that induced currents are generated in the printed conductors 7b and 7c. At this time, as the inductosin rotates, the mutual inductance between the printed conductor 7a and the printed conductors 7b and 7c changes, so the induced current generated in the printed conductors 7b and 7c also changes sinusoidally, and therefore the load resistance 8a The peak value of the voltage generated across 8b also changes sinusoidally as the inductosin rotates. Amplifiers 9a and 9b amplify the voltage generated across the load resistors 8a and 8b,
The synchronous capacitors 11a and 11b pass the modulated output output from the drive circuit 4.
Therefore, the modulation circuits 10a and 10b demodulate the outputs of the amplifiers 9a and 9b using the outputs of the synchronous capacitors 11a and 11b. This demodulated output is sent to the outside via amplifiers 9a and 9d. Therefore, it is possible to obtain a signal that changes sinusoidally depending on the rotation angle of the inductosin.

However, in the conventional modulation/demodulation circuit, when the gap between the stator and rotor of the inductosyn fluctuates, for example, the range of change in mutual inductance fluctuates, or the amplification degree of the amplifiers 9a to 9d fluctuates due to temperature change, the amplifier There was a drawback that the amplitude of the signals output from 9c and 9d fluctuated.

In order to eliminate the above drawbacks, the present invention includes an amplitude detection circuit that detects the amplitude of the demodulated signal, and makes the amplitude of the demodulated signal constant by negatively feeding back the detection output of the amplitude detection circuit. in,
A detailed explanation will be given below according to the drawings.

FIG. 2 is a circuit diagram showing one embodiment of the present invention, and the same elements as in FIG. 1 are given the same reference numerals. In FIG. 2, reference numeral 12 denotes an adder circuit that adds the reference voltage output from the voltage source 1 and the output voltage of an amplitude detection circuit 14, which will be described later, and outputs the result, 13a and 13b.
14 is an inverting amplifier; 14 is an amplitude detection circuit for detecting the amplitude of the voltage output from the buffer amplifiers 9c and 9d and the inverting amplifiers 13a and 13b;
5a to 15g are resistors, and 16a to 16h are diodes. Note that the resistance value of the resistors 15c to 15f is √2 times the resistance value of the resistor 15g.

The operation in the above configuration will be explained. First, the adder circuit 12 adds the reference voltage output from the voltage source 1 and the output voltage of the amplitude detection circuit 14 and outputs the result. A modulation circuit 3 modulates the output voltage of the adder circuit 12 using a carrier signal output from the oscillator 2.
A drive circuit 4 amplifies the modulated output and applies it to the resonant capacitor 5 and coil 6a. This causes the resonance capacitor 5 and the coil 6a to resonate. Therefore, the current flowing through the coil 6a changes, and therefore an induced current is generated in the coil 6b.
Since this induced current flows through printed conductor 7a, induced currents are generated in printed conductors 7b and 7c.
If the inductosin is rotating at this time, the mutual inductance between the printed conductor 7a and the printed conductors 7b and 7c will change periodically as the inductor rotates, so the induced current generated in the printed conductors 7b and 7c will also change periodically. Changes to Therefore, the amplitude of the voltage generated across the load resistors 8a and 8b also changes periodically as the inductosin rotates. Buffer amplifiers 9a and 9b amplify the voltage generated across the load resistors 8a and 8b. Synchronous capacitors 11a and 11b
passes the resonant output output from the resonant circuit formed by the capacitor 5 and the coil 6a. Therefore, the demodulation circuits 10a and 10b demodulate the outputs of the amplifiers 9a and 9b using the modulation signal output from the drive circuit 4. This demodulated output is sent to inverting amplifiers 13a and 13b via amplifiers 9c and 9d, inverted by these inverting amplifiers 13a and 13b, and output. FIG. 3 illustrates four signals output from amplifiers 9c and 9d and inverting amplifiers 13a and 133b. The amplitude detection circuit 14 detects the sum of the largest negative voltage among the voltages output from the buffer amplifiers 9c and 9d and the inverting amplifiers 13a and 13b and a voltage obtained by multiplying the sum of the negative voltages by 1/√2, and performs this detection. The voltage (F(t) in FIG. 3) is transferred to the amplifiers 9c and 9d and the inverting amplifier 13a.
and output as the amplitude of the voltage output from 13b. When the detection voltage becomes smaller, the output of the addition circuit 12 becomes larger, and conversely, when the detection voltage becomes larger, the output of the addition circuit 12 becomes smaller. Therefore, for example, the gap between the stator and rotor of the inductosyn may change, and the printed conductors 7a, 7b and 7c may change.
Even if the mutual inductance between them changes, the amplitude of the voltage output from the inverting amplifiers 13a and 13b does not change.

In the above embodiment, the modulation method of the modulation circuit 3 uses amplitude modulation/demodulation, but the present invention is not limited to this. For example, the present invention can be similarly applied by using a pulse width modulation method in which the carrier signal is a pulse and the pulse width is changed. Can be implemented. Today, pulse width modulation circuits that change the pulse width of the output pulse according to the input voltage are used.
It is integrated into an IC, so it will not be large. It goes without saying that the fundamental frequency of the output pulse is matched to the resonant frequency of the resonant circuit formed by the resonant capacitor 5 and the coil 6a, and at this time, the amplitude V of the resonant output of the resonant circuit
_P is roughly shown in equation (1) below. Please see below (1)
In the equation, V _O is the peak voltage of the pulse, and Q _W is the pulse width.

V _P =4V _O /πsinQ _W /2 (1) Therefore, by changing the pulse width Q _W , the amplitude of the resonant output of the resonant circuit can be controlled.

As described in detail above, according to the present invention, there is an effect that the amplitude of the output voltage does not fluctuate even if the inductosin gap changes or the characteristics of the amplifier change due to temperature changes or the like.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional modulation/demodulation circuit;
The figure is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is a waveform diagram showing the output of the main part of the embodiment shown in FIG. 1... Voltage source, 2... Oscillator, 3... Modulation circuit, 4...
Drive circuit, 5... Resonance capacitor, 6a and 6b... Coil, 7a, 7b and 7c... Printed conductor, 8a and 8b... Load resistor, 9a, 9b,
9c and 9d...buffer amplifier, 10a and 10b...demodulation circuit, 11a and 11b...synchronous capacitor, 12...addition circuit, 13a and 13b
...Inverting amplifier, 14...Amplitude detection circuit, 15a-1
5g...resistance, 16a-16h...diode.

Claims (1)

[Claims] 1. A signal that changes sinusoidally according to the rotation angle of the rotor is generated by passing an alternating current through the printed conductor on the rotor side of the inductosyn and demodulating the signal generated in the printed conductor on the stator side due to mutual induction. In the inductosin modulation/demodulation circuit, the demodulated first signal, a second signal whose phase is shifted by 90 degrees from the first signal, and a third signal obtained by inverting each of these first and second signals are provided. and a fourth signal and detects the sum of the largest negative voltage among these input signals and a voltage obtained by multiplying the sum of the negative voltages by 1/√2, An inductosin modulation/demodulation circuit characterized in that the amplitude of the demodulated signal is made constant by negative feedback of the detection output.