JPS605623A - Frequency ratio arithmetic circuit - Google Patents

Abstract

PURPOSE:To obtain a frequency ratio arithmetic circuit of simple circuit configuration that calculates frequency ratio of the first frequency and second frequency by providing an operational amplifier, switching elements, capacitors and an inverter. CONSTITUTION:Transmission gates 1, 2 as switching elements conduct when a control signal is H level, and beome high impedance when L level. An inverter 3 makes transmission gates 1, 2 on and off alternately corresponding to the first or second frequency. Capacitors 4, 5 makes charging and discharging according to on/off of transmission gates 1, 2. An operational amplifier 6 makes minus side terminal input and plus side terminal reference and constitutes an inversion type amplifier. By providing these units, a frequency ratio arithmetic circuit of simple circuit configuration that calculates ratio of the first frequency to second frequency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frequency ratio calculation circuit that calculates the ratio of two types of frequencies.

Conventionally, to calculate the ratio of two types of frequencies, as shown in Figure 3, two types of frequencies r, , r2 are input to separate frequency-voltage conversion circuits 20, and the output 211F cheek voltage value is divided. There is a method of inputting it into the circuit 21 and calculating the ratio, or a method of measuring two types of frequencies f1 and f2 with a microcomputer,
There is a method of dividing this measured value using software to find the frequency ratio. However, the former has a very large number of circuit elements and requires many adjustments. Although the latter can be expected to measure frequency ratios through accurate calculations, it is costly.

In view of the above drawbacks, the present invention provides a switching element that turns on and off in response to a second frequency between the input terminal and output glass of an operational amplifier, in which a signal that changes in response to a first frequency is connected to the input glass. The circuit configuration includes a capacitor that is connected and charged and discharged by turning on and off this switch element.
c., It is an object of the present invention to provide a frequency ratio calculation circuit with a simple circuit configuration for calculating the frequency ratio between a first frequency and a second frequency.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram of a frequency ratio calculation circuit according to the present invention. 1
．． 2 is a transmission gate as a switching element which is conductive when the control signal is 1 level and becomes high impedance when the control signal is at L level. 3 corresponds to the first or second frequency and alternately turns on and off the ``C transmisoring game 1'' and 4; 4.
5 turns on two transmission gates 1 and 2;
A capacitor that charges and discharges when turned off. 6 is an operational amplifier that uses the negative terminal as an input and the positive terminal as a base to form an inverting amplifier. 7 is a constant voltage source. 8 is an IZ
Namekawa capacitor 9 is a low-pass filter for shaping the output waveform.

Next, the operation of the above configuration will be explained. First, when the first frequency f1 is at H level, the transmission gate 1 is conductive and the transmission gate 2 is in a high impedance state. The capacitor 4 is then charged through the external impedance Rs and the conduction resistance RO of the transmission gate 1. Here, the charging time constant τ-C+ (R, s, +R'o) of the capacitor 4 is set sufficiently smaller than the first frequency r, l (level 1"8 hours), so the initial charging time constant of the capacitor 4 is If the charge is set to zero, the charged charge Q will be constant. Also, the first frequency f
+ is 1. When the level is reached, transmission gate 1 becomes high impedance and transmission gate 2 becomes conductive. The charge Q of the capacitor 4 is discharged through the external impedance R3' and the conduction resistor RO of the transmission gate 2. Note that the discharge time constant τ'-C1 (Rs'+Ro) of the capacitor 4 is determined when the first frequency f is L.
Since the level TL dark time is set to be sufficiently small, the charge Q charged in the capacitor 4 is completely discharged and becomes zero.

In this way, the transmission gate at the first frequency f,
Considering the state in which 1, 1, and 2 are alternately turned on and off,
The charge Q that moves during one cycle is Q=C1Vref.

Therefore, the average value of the current is that the charge moving in 1 second is C1Vr
Since ef f I, 10 = CIV r e f f 1 / 1.

Therefore, the equivalent resistance RA of this 30 parts is RA = V r”
' / T o = 1 / C + f +.

Similarly, the equivalent resistance 1 of 40 parts inputting the second frequency f2
? s becomes RB-1/C2f2.

30 parts and 40 parts in FIG. 1 are equivalent resistances RA, respectively,
, RB, Fig. 1 becomes an inverting amplifier, and the output voltage Vo is Vo=-Re/RA-Vref -(C1fl)/(C2f2)Vref=-(C1Vr
ef)/C2·(f I/f2) If Vref is constant, the output voltage VO is proportional to the frequency ratio (II/f2). As described above, the waveform of the voltage VO outputted from the first frequency f and the second frequency ``2'' is adjusted by the low-pass filter 9.

Another embodiment of the present invention will be explained in FIG. 10 is f-V
It is a converter, and the output voltage Vi is Vi=Rf I (R constant number).

Here, the output voltage Vo is do.

Note that the circuit of the above embodiment can be used for the applications as shown in (11 to ()) below.

(1) The gear ratio of the transmission is detected by inputting an iG pulse signal proportional to the engine speed and a vehicle speed pulse signal proportional to the vehicle speed to this circuit.

(2) Fuel consumption is detected by inputting the output of a rotary flow rate needle that generates a pulse proportional to the fuel flow rate and the vehicle speed pulse to this circuit.

(A sensor that outputs a frequency proportional to the rotation speed is installed before and after the 31A/T torque converter, respectively.
The slip rate of the torque converter is detected by inputting it to this circuit.

Further, in addition to the examples (1) to (3), this circuit can be applied if the input is a pulse input proportional to a certain amount.

As described above, according to the present invention, a signal that changes in response to the first frequency is turned on and off in response to the second frequency between the input terminal and the output terminal of the operational amplifier connected to the input terminal. Switch element and turning on of this switch element,
Since the amplifier circuit uses an operational amplifier with a simple circuit configuration in which a capacitor that is charged and discharged when it is turned off is installed, it has the excellent effect of being able to detect the ratio of two types of frequencies as a voltage value proportional to this frequency ratio. There is.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a frequency ratio calculation circuit according to the present invention, FIG. 2 is a circuit block diagram of another embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional method. 1.2... Transmission gate, 3... Inverter, 4.5... Capacitor, 6... Operational amplifier. Representative Patent Attorney Takashi Okabe

Claims (1)

[Claims] An operational amplifier whose input terminal is connected to a signal that changes in accordance with a first frequency; and an operational amplifier which is located between the input ring and the glass at the output end of the operational amplifier, and which corresponds to a second frequency when turned on or off. A switching element that performs
A frequency ratio calculation circuit characterized by comprising a capacitor.