JPS61204572A - Frequency/voltage converter - Google Patents

Abstract

PURPOSE:To execute the monolithic integration and to select the polarity of the output voltage by constituting the reference voltage by a switched capacitor integrator, a pulse generating device and a switch control circuit. CONSTITUTION:A pulse is generated by a pulse generating device 2 each time an input signal voltage reaches a certain voltage value. A switch control circuit 3 forms a switch control signal by the pulse and the clock signal applied to a clock input terminal 32, charges the capacitor to constitute an integrator 1, to a reference voltage each time the pulse is outputted from the generating device 2 and the charging charge is integrated. The output voltage of the integrator 1 is in proportion to the integrated charge, and therefore, the voltage in proportion to the frequency of the input signal is obtained from an output terminal 12. Whether or not the integrator 1 is operated as a positive-phase integrator and operated as a reverse-phase integrator is executed by changing the switch sequence of the integrator 1 by the circuit 3. By the constitution, since the digital signal processing is main, integrating can be easily executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a frequency-to-voltage converter that operates in real time and obtains a voltage proportional to the frequency of a human input signal without using a digital-to-analog converter or a counter.

Conventional technology A conventional frequency/voltage converter that operates in real time consists of a monostable circuit and an integrator.The monostable circuit converts a human signal into a constant pulse signal, which is integrated by an integrator to calculate the frequency A voltage proportional to is obtained. As the integrator, a passive integrating circuit using a resistor and a capacitor, an active integrating circuit using an operational amplifier, a resistor, and a capacitor, or an integrating circuit using a resistor, a capacitor, and a constant current source is used.

Problems to be Solved by the Invention In this conventional method, the sensitivity of converting frequency to voltage depends on the pulse width of the pulse signal from the monostable circuit.
Requires a highly stable monostable circuit. Furthermore, in order to reduce output voltage fluctuations, it is necessary to increase the integration time constant, which requires a high resistance and large capacitance capacitor, which makes monolithic integration difficult. There were problems such as only being able to obtain a voltage of either negative polarity.

The present invention was made to solve these problems.
The object of the present invention is to provide a frequency/voltage converter that can be monolithically integrated and that can convert an input signal frequency to either positive or negative voltage.

Means for Solving the Problems FIG. 1 is a block diagram of the frequency/voltage converter of the present invention, in which 1 is a pinched capacitor integrator, 2 is a pulse generator, 3 is a switch control circuit, and 4 is a reference. It is a voltage source. An input signal is applied to the pulse generator 20 input terminal 21 and a converted voltage is obtained from the output terminal 12 of said integrator 1. The switch control circuit 3 has an output voltage polarity selection terminal 31 to which a signal for selecting the polarity of the output voltage is applied.

Operation The pulse generator 2 generates a pulse every time the input signal voltage reaches a certain voltage value. The switch control circuit 2 generates a switch control signal from this pulse and the clock signal applied to the clock input terminal 32, controls the switch included in the switched capacitor integrator, and outputs the pulse generator 2. Every time a pulse is output from the integrator 1, the capacitor constituting the integrator 1 is photoelectrically charged to the reference voltage 4, and this charged charge is integrated. Since the output voltage of the switched capacitor integrator 1 is proportional to the integrated charge, a voltage proportional to the frequency of the input signal is obtained at the output terminal 12. Whether the switched capacitor integrator 1 is operated as a positive phase integrator or a negative phase integrator is determined by the switch control circuit 3 based on a signal applied to the output voltage polarity selection terminal 31. - By changing the switch sequence of the capacitor integrator l. When the integrator 1 acts as a positive phase integrator, the input signal frequency is converted into a voltage of positive polarity, and when it acts as a negative phase integrator, the input signal frequency is converted into a voltage of negative polarity.

Embodiment FIG. 2 shows an embodiment of the present invention, in which the duty ratio is 50%.
This is a wiring diagram of a frequency/voltage converter that converts the frequency of a symmetrical square wave into a voltage, and the symmetrical square wave is applied to the input terminal 21 of the pulse generation circuit 2.

In this example, the pulse generator 2 has two F-di-trigger type D
It consists of flip-flops 22 and 23 and an exclusive OR gate 24, and when the voltage applied to the output voltage polarity selection terminal 31 is positive, the rising and falling edges of the input signal are J clock signals input to the clock signal input terminal 32. When the voltage at the output voltage polarity selection terminal 31 is negative, it is detected in synchronization with the φ clock signal input to the clock signal input terminal 33. Here, the φ clock signal and the φ clock signal are two-phase clock pulses with a frequency much higher than the input signal frequency.

Switched capacitor integrator 3 has an input capacitor 10
11 Integral capacitor 102, damping capacitor 1
03, hold capacitor 104, switch 105.106.10 to control charging and discharging of these capacitors
7.108.109.110.111 and operational amplifier 10
Consists of 0. The clock signal symbol written next to a switch indicates the clock signal that turns on the switch. The opening and closing of the switches 105 and 106 are controlled by a switch control circuit 3 made up of logic gates. When a positive output voltage polarity is specified, the switch 105 is closed by the i clock signal at the rise and fall of the input signal, and the capacitor 101 is set to the reference voltage 4.
Since the switch 106 closes with the next φ clock signal, the charged charge is transferred to the S-minute cabassic 102, charging the capacitor 102 to the polarity shown. Charging and transfer of the capacitor 101 are instantaneous and therefore independent of the pulse widths of the input signal and clock signal. Since the number of times the capacitor 102 is charged per second is proportional to the frequency of the input signal (in this example twice the frequency of the input signal), a positive voltage proportional to the human frequency is obtained from the output terminal of the integrator 3.

When a negative output voltage polarity is specified, the switch 105 is closed by the φ clock signal at the rise and fall of the input signal, and the capacitor 101 is charged to the illustrated polarity. In this case, a charging current simultaneously flows through the capacitor 102 and charges the capacitor 102 to a polarity opposite to that shown, so that a negative voltage appears at the output terminal 12.

FIG. 3 shows the relationship between the input signal frequency and the output voltage obtained in the embodiment of FIG. 2 using two-phase locking signals φ and φ of 65 kHz, and shows that the frequency converter of the present invention has a wide range. This shows that the signal frequency is converted into voltage with good linearity over the frequency range.

Effects of the Invention Since the pulse generator 2 and the switch control circuit 3 mainly perform digital signal processing, they can be integrated using the current integration technology, and the switched capacitor integrator 1 can also be integrated using the CMO5 technology. Therefore, the frequency-to-voltage converter of the present invention can be monolithically integrated. Furthermore, as described above, since the conversion sensitivity does not depend on the pulse width, highly accurate frequency/voltage conversion is possible, and the polarity of the output voltage can also be selected, making the present invention extremely useful in applications.

4. Brief explanation of aspects FIG. 1 is a block diagram of the frequency/voltage converter of the present invention, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a diagram obtained by the embodiment of FIG. 2. Relationship between input signal frequency and output voltage.

In FIGS. 1 and 2, 1 is a switched capacitor integrator, 2 is a pulse generator, and 3 is a switch control circuit.

Claims (1)

[Claims] A switch control circuit (3) having a switched capacitor integrator (1), a pulse generator (2) that generates a pulse when the input signal voltage reaches a certain voltage value, and an output voltage polarity selection terminal (31). A reference voltage (4) is connected to the input terminal (11) of the integrator (1), and a frequency
voltage converter.