KR19990010369A - Voltage controlled double oscillator - Google Patents

Abstract

A voltage controlled double oscillator for controlling a voltage to adjust an output frequency of an double oscillator. The oscillator for generating a signal using charge and discharge of a capacitor. And first and second switches for switching by a periodic signal to control charging and discharging of the capacitor, and first and second voltage controlled current sources for supplying current for controlling the charging and discharging speed of the capacitor. Therefore, the output frequency can be adjusted by adjusting the charge / discharge rate of the capacitor in accordance with the change of the current value supplied by the adjustment of the constant control voltage.

Description

Voltage controlled double oscillator

The present invention relates to a relaxation oscillator, and more particularly, to a voltage controlled relaxation oscillator capable of variably controlling an output frequency.

As shown in FIG. 1, the double oscillator is connected to the first and second resistors R ₁ and R ₂ connected in parallel to the connection nodes of the first and second resistors R ₁ and R ₂ in parallel. The first capacitor C ₁ , the Schmitt trigger 10 outputting a voltage control signal by the charge / discharge operation of the first capacitor C ₁ , and the second resistor R ₂ are connected to the first resistor C ₂ . The first switch S ₁ is configured to control the charging and discharging operation of the capacitor C ₁ .

The operation of the oscillator configured as described above is as follows.

When the first switch (S ₁₎ is assumed to be off (off) state initially, the current is charged in the first capacitor (C ₁₎ via a first resistance (R ₁₎ The voltage across the first capacitor (C ₁₎ (V _C ) is increased.

The Schmitt trigger 10 outputs a high voltage control signal when the voltage V _C applied to the first capacitor C ₁ increases and is greater than the upper limit voltage V _B. At this time, the first switch S ₁ is turned on by the high voltage control signal output from the Schmitt trigger 10 so that the first capacitor C ₁ is discharged.

Then, the when lower than a first capacitor a first capacitor in accordance with the discharge operation of the (C ₁₎ (C _1), the voltage (V _C), the lower limit voltage (V _A) of the Schmitt trigger 10 is filled in, the Schmitt trigger ( 10) outputs a low voltage control signal.

At this time, the first switch S ₁ is turned off again by the low voltage control signal.

Therefore, the periodic waveform is output in accordance with the repetition of the charge / discharge operation of the first capacitor C ₁ .

The conventional oscillator has a problem in that the first and second resistors and the first capacitor are fixed to a predetermined value so that the frequency output from the Schmitt trigger cannot be varied.

Accordingly, an object of the present invention is to provide a voltage controlled dual oscillator capable of varying an output frequency by using a voltage.

1 is a circuit diagram of a double wave oscillator according to the prior art,

2 is a circuit diagram of a voltage controlled dual oscillator according to the present invention;

3 is a detailed circuit diagram of the present invention.

Explanation of symbols for main parts of the drawings

10, 40: Schmitt trigger I ₁ , I ₂ : voltage control current source

The voltage controlled double wave oscillator according to the present invention is an oscillator for generating a signal by using charge and discharge of a capacitor. It is characterized by including a first and a second switch for controlling the charge and discharge, and a first and second voltage control current source for supplying a current for controlling the charge and discharge speed of the capacitor.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a voltage controlled double oscillator according to the present invention will be described in detail.

2 is a circuit diagram of a voltage controlled double oscillator according to the present invention.

Referring to FIG. 2, the configuration thereof includes a first and second current sources I ₁ (Vctrl) and I ₂ (Vctrl) for supplying a current controlled by a predetermined control voltage, and a first current source I _1. (Vctrl)) to the Schmitt trigger for charging is generated in a periodic signal according to the charge and discharge of the capacitor (C ₁₎ and a capacitor (C ₁₎ is discharged by a second current source (I ₂ (Vctrl)) by 40 and, the switching operation by a signal generated at the Schmitt trigger 40 of the first current source (I ₁ (Vctrl)) and the first switch (S _1), and a Schmitt trigger (40) for connecting the capacitor (C ₁₎ It is composed of a second switch S ₂ which is operated by a periodic signal and connects the second current source I ₂ (Vctrl) and the capacitor C ₁ .

Here, the first voltage control current source I ₁ (Vctrl) includes a first transistor Q ₁ operated by a constant control voltage Vctrl applied to a base as shown in FIG. 3, and a first transistor ( A second transistor Q ₂ having a base connected to the emitter of Q ₁ ), a third transistor Q ₃ having a base connected to the collector of the second transistor Q ₂ , and an emission of the second transistor Q ₂ . Resistor and a resistor R _O simultaneously connected to the collector of the third transistor Q ₃ . The constant current source I _x is connected to the emitter of the first transistor Q ₁ .

In this case, the first and third transistors Q _{1 and} Q ₃ are NPN transistors, and the second transistor Q ₂ is a PNP transistor.

Here, the configuration of the second current source I ₂ (Vctrl) is the same as that of the first current source I ₁ (Vctrl), and thus the description of the configuration will be omitted.

The operation of the voltage controlled oscillator configured as described above is as follows.

Assuming that the first switch S ₁ is initially off, the capacitor C ₁ is charged by the current supplied from the first current source I ₁ (Vctrl), and the Schmitt trigger 40 uses the capacitor C _When the charging voltage V _C of ₁ ) is greater than the upper limit voltage V _B , a high control signal is output.

When the high control signal output from the Schmitt trigger 40 is output, the first switch S ₁ is turned off and the second switch S ₂ is turned on, so that the capacitor C _{1 is} connected to the second current source I ₂ (Vctrl). Start discharging by)).

The Schmitt trigger 40 outputs a low control signal when the charging voltage V _C of the capacitor C ₁ is lower than the lower limit voltage V _A by the discharge operation.

As a result, since the first switch S ₁ is turned on and the second switch S ₂ is turned off and returned to the initial state, the Schmitt trigger 40 repeatedly performs such an operation to output a periodic signal.

Here, the first and second current sources I ₁ (Vctrl) and I ₂ (Vctrl) may be formed by the constant current source I _x , where the VBE of the first transistor Q ₁ and the VBE of the second transistor Q ₂ are equal to each other. Almost the same, the voltage at point A is equal to the constant control voltage.

Therefore, output currents I (Vctrl) of the first and second current sources I ₁ (Vctrl) and I ₂ (Vctrl) are

According to Equation 1, the current is supplied proportionally variable by a constant control voltage Vctrl, and when the current is increased, the speed of charging and discharging the capacitor C ₁ is increased, so that the Schmitt trigger 40 When the frequency of the output control signal increases and the current decreases, the charge / discharge rate of the capacitor C ₁ decreases, so that the frequency of the output control signal decreases.

The voltage controlled double oscillator according to the present invention can adjust the output frequency by adjusting the charge and discharge speed of the capacitor in accordance with the change of the current value supplied by the adjustment of the constant control voltage.

Claims (4)

An oscillator for generating a signal using charge and discharge of a capacitor, the oscillator comprising: a Schmitt trigger for generating a periodic signal according to charge and discharge of the capacitor; First and second switches configured to switch by the periodic signal to control charge and discharge rates of the capacitor; And a first and second voltage controlled current sources for supplying current for controlling the charge and discharge speed of the capacitor. 2. The voltage controlled oscillator of claim 1, wherein the capacitor is configured to be charged by the operation of the first switch and to be discharged by the operation of the second switch. 2. The voltage of claim 1, wherein said first voltage controlled current source charges said capacitor by said first switch, and said second voltage controlled current source is configured to discharge said capacitor by said second switch. Controlled double oscillator. 2. The apparatus of claim 1, wherein the first and second voltage controlled current sources comprise: a first NPN transistor operated by a constant control voltage applied to a base; A third NPN transistor having a base connected to the collector of the second transistor, a resistor connected simultaneously to the emitter of the second transistor and the collector of the third transistor, and a constant current source connected to the emitter of the first transistor. Voltage controlled double oscillator.