JPH0550821U - Oscillator circuit - Google Patents

Abstract

(57) [Summary] [Purpose] An oscillation circuit that can obtain a constant amplitude value without variations in oscillation amplitude. [Configuration] In an oscillation circuit including a low-pass filter 10 and an integrating circuit 10, capacitors used in the low-pass filter and the integrating circuit are manufactured in the same lot, and capacitors having the same capacitance value are used alone or It is composed of a plurality of combinations.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an oscillator circuit, and more particularly to reducing variations in its oscillation amplitude.

[0002]

[Problems to be solved by conventional techniques and devices]

 FIG. 2 is a circuit diagram of a conventional oscillator circuit applied to a torque sensor. In the figure, 10 is a low-pass filter, which is composed of an operational amplifier 11, resistors R1 and R2, and capacitors C1 and C2. Reference numeral 20 denotes an integrator, which includes an operational amplifier 21, a resistor R3, and an offset voltage 22. R4 and R5 are resistors, and ZD is a Zener diode. Here, the capacitance of each capacitor is set as follows, and the resistance values of the resistors R1 to R3 have the following relationship. C1 = C3 = 3300 pF C2 = 6800 pF R1 = R2 = R3

In the oscillation circuit of FIG. 2, variations in the relative capacitances of the capacitors C1 to C3 appear as variations in the oscillation amplitude. Therefore, when applied to a torque sensor, the AC characteristics (the motor to the torque input from the handlebar) Although the power steering is configured by adding the assist current, this is a characteristic that is a factor that determines the assist current.) There is a problem that the assist current also changes. Further, since the temperature coefficients of the capacitors C1 to C3 are different, the oscillation amplitude depends on the temperature and finally appears as a temperature fluctuation of the AC characteristic. The present invention has been made in order to solve such a problem, and an object thereof is to apply an oscillating circuit capable of obtaining a constant oscillation amplitude.

[0004]

[Means for Solving the Problems]

 The oscillator circuit according to the present invention is an oscillator circuit including a low-pass filter and an integrating circuit. The capacitors used in the low-pass filter and the integrating circuit are manufactured by the same lot and have the same capacitance value. It is composed of a single capacitor or a combination of multiple capacitors.

[0005]

[Action]

 In the present invention, the capacitors are manufactured in the same lot, and the capacitors having the same capacitance value are configured singly or in combination, so that the relative capacitance values are the same and the relative capacitance values are the same. The temperature coefficients are also equal. Therefore, variations due to the capacitor and variations in the oscillation amplitude due to temperature are eliminated.

[0006]

【Example】

 FIG. 1 is a circuit diagram of an oscillator circuit according to an embodiment of the present invention. In this embodiment, the capacitor corresponding to the capacitor C2 in the circuit of FIG. 2 is composed of two capacitors Ca and Cb, and the capacitance of each capacitor is set as follows, and the resistances of the resistors R1 to R3 are The resistance value has the following relationship. C1 = Ca = Cb = C3 = 3300pF R1 = R2 = R3 That is, the capacitors C1, Ca, Cb, and C3 have the same capacitance and use the same lot product. Here, the cutoff frequency fo of the low-pass filter 10 is obtained by the following equation.

[0007]

[Equation 1] Further, the gain e ₀ / e _i = Q of the low pass filter 10 is obtained by the following equation.

[0008]

[Equation 2] Since the output of the operational amplifier 11 is all fed back, the gain k = 1 of the operational amplifier (equation 2) is expressed by the following equation.

[0009]

[Equation 3] Next, the gain A of the integrator 20 is expressed by the following equation.

[0010]

[Equation 4]

As is clear from the above equation, when the capacitors C1, C2a, C2b, and C3 have the same value, the gain does not depend on the value of these capacitors, and the gain is the same. In some cases, the temperature characteristics will be the same, so it will not be affected by temperature.

[0012]

[Effect of the device]

 As described above, according to the present invention, the capacitors are manufactured in the same lot and the capacitors having the same capacitance value are configured individually or in combination, so that the relative capacitance values are Moreover, the relative temperature coefficients become equal. Therefore, variations due to capacitor lots and variations in oscillation amplitude due to temperature are eliminated. In addition, since capacitors of the same lot are used, it is not necessary to use sorted products, so costs can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an oscillator circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional oscillator circuit.

[Explanation of symbols]

 10 Low-pass filter 20 Integration circuit

Claims (1)

[Scope of utility model registration request] 1. In an oscillation circuit including a low-pass filter and an integrating circuit, the capacitors used for the low-pass filter and the integrating circuit are capacitors manufactured in the same lot and having the same capacitance value. And an oscillator circuit characterized by being configured in combination.