KR100205246B1 - oscillator - Google Patents

Abstract

The present invention relates to an oscillator, comprising: a frequency variable control unit for controlling and outputting a voltage level; A comparison unit for comparing and switching a voltage level from the frequency variable control unit with a predetermined reference voltage level; A current control unit controlling the current from the comparison unit to have hysteresis characteristics; An output voltage controller for controlling an output voltage level in response to the control from the current controller; An oscillation control unit for preventing high frequency oscillation of the feedback signal from the output voltage control unit is provided, and when a conventional oscillator is used to vary the output frequency and the duty ratio of the output waveform, it is necessary to connect a separate circuit. For example, by using a comparator capable of controlling hysteresis by the input voltage, the output frequency and the duty cycle can be changed without an additional circuit.

Description

Oscillator

The present invention relates to an oscillator, and more particularly to an oscillator capable of varying the duty ratio and output frequency.

For example, the oscillation frequency of the RC oscillator can be expressed by the following equation.

[Equation 1]

Therefore, to change the oscillation frequency in the RC oscillator, the time constant (R * C) is changed by changing the capacitance of the resistor or capacitor in the oscillator. For example, when the resistance value R and the capacitor C are increased in Equation 1, the oscillation frequency is lowered.

On the other hand, in order to vary the duty ratio of the output signal, a dividing circuit using a flip-flop (FLIP-FLOP) is further connected to the oscillator and used in a pulse generator.

Referring to FIG. 1, a conventional feedback signal is output to a first feedback resistor Ra and a second feedback resistor Rb by a signal feedback output to an oscillator, and the variable resistor Rv. And the negative feedback (NEGATIVE FEEDBACK) to the third feedback resistor (Rc) and the capacitor (C1) to oscillate.

At this time, the oscillation frequency can be increased by reducing the value of the second feedback resistor Rb compared to the value of the first feedback resistor Ra and decreasing the swing SWING of the output voltage Vo. However, at this time, the duty ratio of the signal output from the amplifier is not constant. For example, if a square wave having a duty ratio of 50% is required, the signal output from the oscillator is divided in half using the J-K flip-flop 20.

As described above, the conventional oscillator has a problem that the size of the circuit becomes large because it is necessary to change the resistance value or the capacitance of the capacitor or additionally connect an external circuit when the output frequency and duty ratio need to be varied.

Accordingly, the present invention has been proposed to solve the above-described problems, and an object thereof is to provide an oscillator capable of controlling an output frequency and a duty ratio according to an input voltage and having a simple structure.

1 is a circuit diagram schematically showing an oscillator according to a conventional embodiment;

2 schematically illustrates an oscillator according to an embodiment of the present invention;

Figure 3 shows a block according to the function of the oscillator according to an embodiment of the present invention;

4 is a view showing in detail the OP amplifier in the oscillator according to an embodiment of the present invention shown in FIG.

5 is a timing diagram showing an output frequency and a duty ratio for an oscillation frequency variable control signal of an oscillator according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

100: frequency variable control unit 200: comparison unit

300: current controller 400: output voltage controller

500: oscillation control unit 210: switch unit

220: constant current portion

According to a feature of the present invention proposed to achieve the above object, an oscillator composed of a comparator having a hysteresis characteristic and a frequency variable control unit for outputting a variable oscillation frequency control signal so that the oscillation frequency is variable; A comparator for comparing the oscillation frequency variable control signal from the frequency variable controller and a reference voltage level; A current control unit which hysteresis operates according to the comparison current from the comparison unit; An output voltage control unit controlling a level of a signal output from the current control unit; And an oscillation control unit for preventing high frequency oscillation due to a feedback signal from the output voltage control unit.

In a preferred embodiment of this aspect, the frequency variable control section includes a function of outputting a corresponding voltage level according to a predetermined selection signal.

In a preferred embodiment of this aspect, the comparison unit comprises: a switch unit for comparing the oscillation frequency variable control signal from the frequency variable control unit with a predetermined reference voltage level and outputting a switch signal; It includes a constant current unit for supplying a constant current to the switch unit.

In a preferred embodiment of this aspect, the constant current unit includes a controllable constant current as the internal resistance or the emitter resistance of the fifth NPN transistor is varied.

In a preferred embodiment of this aspect, the current control unit includes: an eighth PNP transistor / ninth PNP transistor for flowing alternating current until a load is applied to the first NPN transistor; A tenth PNP transistor / eleventh PNP transistor for flowing AC until a load is applied to the second NPN transistor; A twelfth PNP transistor / 13th PNP transistor coupled to a collector and a base respectively to the collector and the base of the eighth PNP transistor / ninth PNP transistor to control a current ratio; A fourteenth PNP transistor / a fifteenth PNP transistor, in which a collector and a base are coupled to the collector and the base of the ninth PNP transistor / the tenth PNP transistor to control a current ratio; And a current sensing resistor connected between the emitter and the supply voltage terminal of the eighth PNP transistor / ninth PNP transistor to the fourteenth PNP transistor / 15th PNP transistor to prevent overcurrent.

In a preferred embodiment of this aspect, the current control section includes controlling the frequency and duty ratio by a collector current that increases in proportion to the number of collectors of the multitransistor connected to the output of the comparator.

In a preferred embodiment of this aspect, the output voltage control section includes a pull-up resistor for controlling the output voltage; And a sixteenth NPN transistor for controlling the swing of the output voltage to reduce the output potential.

In a preferred embodiment of this aspect, the oscillation control unit includes a timing capacitor capable of varying a frequency by a change in charge time and discharge time by an output voltage; It includes a timing resistor for adjusting the duty ratio of the oscillation output in proportion to the input voltage.

In a preferred embodiment of this aspect, the oscillation control unit includes the timing resistor and the timing capacitor in an integrator form for preventing high frequency oscillation.

In a preferred embodiment of this feature, it is possible to control the current ratio of the current control unit according to the voltage level of the frequency variable control unit.

The present invention relates to an oscillator, comprising: a frequency variable control unit for controlling and outputting a voltage level; A comparison unit for comparing and switching a voltage level from the frequency variable control unit with a predetermined reference voltage level; A current control unit controlling the current from the comparison unit to have hysteresis characteristics; An output voltage controller for controlling an output voltage level in response to the control from the current controller; An oscillation control unit for preventing high frequency oscillation of the feedback signal from the output voltage control unit is provided, and when a conventional oscillator is used to vary the output frequency and the duty ratio of the output waveform, it is necessary to connect a separate circuit. For example, by using a comparator capable of controlling hysteresis by the input voltage, the output frequency and the duty cycle can be changed without an additional circuit.

Hereinafter, referring to FIG. 2, the frequency and duty ratio of the output signal are directly related to the capacitance and charge / discharge time of the capacitor. For example, if the output voltage Vo is saturated at a positive value, the capacitor C has an exponential magnitude in the positive Vsat direction. At the point of UTP (UPPER TRIP POINT), the output voltage Vo changes to (-) Vsat, and then the capacitor voltage Vc decreases. When the output voltage (Vo) is changed to (-) Vsat continuously, the capacitor remains in the previous state. When the capacitor voltage (Vc) is equal to the LTP (LOWER TRIP POINT) point, the output voltage (Vo) is again positive (+). Turns into Vsat.

That is, when the input voltage Vin is 0V, the current charged in the capacitor C is the current flowing through the resistor R2 even when the output voltage level Vo is positive or negative. Since Ir2) is the same, the duty ratio of the oscillation output is 50%.

When the input voltage level Vin is positive, the current charged in the capacitor C flows into Ir2 + Ir1 (resistance R1 when the output voltage level Vo is positive). Current) and the cycle becomes shorter. When the output voltage level Vo is negative, the period becomes Ir2-Ir1. Therefore, the duty ratio D decreases in proportion to the input voltage Vin.

On the other hand, when the input voltage level Vin is a negative value (-), the current charged in the capacitor C becomes Ir2-Ir1 when the output voltage level Vo is a positive value (+). Longer When the output voltage level Vo is negative, the period becomes Ir2 + Ir1 and the period is shortened. Therefore, the repetition period increases in proportion to the input voltage Vin.

Here, the duty ratio DUTY RATIO refers to a percentage of the period PERIOD with respect to the output pulse width OUTPUT PULSE WIDTH.

3 to 4, the novel oscillator of the present invention comprises a frequency variable controller 100, a comparator 200, a current controller 300, an output voltage controller 400, an oscillation controller 500. have.

First, the frequency variable control unit 100 outputs an oscillation frequency variable control signal. The comparator 200 compares the signal level Vin from the frequency variable controller 100 with the reference voltage level Vref and outputs a switching signal. The current controller 300 outputs the hysteresis HYSTERESIS as the active load having the current ratio variable function according to the comparison signal level from the comparator 200.

At this time, the equation for obtaining hysteresis can be expressed as follows.

[Equation 2]

In Equation 2, VthH refers to HTP (HIGH TRIP POINT) in a section having hysteresis characteristics. In addition, VthL refers to LTP (LOW TRIP POINT) in a section having hysteresis characteristics.

As shown in FIG. 4, in the eighth PNP transistor Q8 / ninth PNP transistor Q9 of the current control unit 300, an emitter and a collector are connected between the first conductive path L1 and an external power supply voltage. The base is connected to the base of the twelfth PNP transistor Q12 / thirteenth PNP transistor Q13. An emitter and a collector are connected between the second conductive path L2 and the external power supply voltage in the tenth PNP transistor Q10 and the eleventh PNP transistor Q11, and the base is a fourteenth PNP transistor Q14 / 15th. It is connected to the base of the PNP transistor Q15. In addition, an emitter and a collector are connected to the twelfth PNP transistor Q12 and the thirteenth PNP transistor Q13 between the second conductive path L2 and the external power supply voltage, and the base of the eighth PNP transistor Q8 / It is connected to the base of the ninth PNP transistor Q9. Similarly, in the fourteenth PNP transistor Q14 and the fifteenth PNP transistor Q15, the emitter and the collector are connected between the first conductive path L1 and the external power supply voltage, and the base is the tenth PNP transistor Q10 /. It is connected to the base of the eleventh PNP transistor Q11. The sixth and seventh NPN transistors Q6 to Q7 are connected to send collector currents of the eighth PNP transistor Q8 and the eleventh PNP transistor Q11 to the ground side.

At this time, the current ratio is varied according to the number of multi-collectors (MULTIPLE COLLECTOR) of the twelfth PNP transistor Q12 / thirteenth PNP transistor Q13 to fourteenth PNP transistor Q14 / fifteenth PNP transistor Q15.

The output voltage controller 400 includes a sixteenth NPN transistor Q16 and a pull-up resistor R2 for controlling the output voltage swing based on the signal level from the current controller 300.

For example, when the sixteenth NPN transistor Q16 is saturated, the output voltage level decreases, and when the sixteenth NPN transistor Q16 cuts off, the pull-up resistor R2 outputs the output voltage level Vo. ) To the supply voltage level (VCC).

The present invention varies the hysteresis characteristics to change the charge and discharge times of the capacitor (C). By varying the Vth (THRESHOLD VOLTAGE) of the comparator 200, when the input voltage Vin is increased, the duty ratio is reduced and the oscillation frequency is variable.

That is, by using a comparator capable of controlling the output current according to the input voltage level, it is not necessary to design a separate circuit when the output frequency and duty ratio need to be changed.

The present invention solves the problem of connecting a separate circuit when the output frequency and duty ratio (DUTY RATIO) of the output waveform to be changed using a conventional oscillator, comparator that can control the hysteresis by the input voltage By using, it is possible to change the output frequency and duty cycle (DUTY CYCLE) without additional circuitry.

Claims (10)

In an oscillator that generates a predetermined frequency, Frequency variable control means (100) for outputting a predetermined oscillation frequency variable control signal (Vin) to vary the oscillation frequency; Comparison means (200) for comparing the oscillation frequency variable control signal (Vin) from the frequency variable control means (100) with a predetermined reference voltage level (Vref); Current control means (300) for hysteresis operation according to the comparison current from the comparison means (200); Output voltage control means (400) for controlling a signal output from the current control means (300) to a predetermined level; An oscillator characterized in that it comprises an oscillation control means (500) for preventing high frequency oscillation by the signal fed back from the output voltage control means (400). The method of claim 1, The frequency variable control means 100 is characterized in that it comprises a function for outputting a corresponding voltage level in accordance with a predetermined selection signal The method of claim 1, The comparison means 200 includes switch means 210 for outputting a switch signal by comparing the oscillation frequency variable control signal Vin from the frequency variable control means 100 with a predetermined reference voltage level Vref; Oscillator, characterized in that it comprises a constant current means for supplying a constant current to the switch means (210). The method of claim 3, wherein The constant current means 220 is an oscillator, characterized in that the constant current can be controlled by varying the emitter resistance (R4) of the internal resistance (R3) or the fifth NPN transistor. The method of claim 1, The current control means 300 includes: an eighth PNP transistor (Q8) / ninth PNP transistor (Q9) for flowing alternating current until a load is applied to the first NPN transistor (Q1); A tenth PNP transistor Q10 / eleventh PNP transistor Q11 for flowing alternating current until a load is applied to the second NPN transistor Q2; A twelfth PNP transistor (O12) and a thirteenth PNP transistor (Q13) for coupling a collector and a base to the collector and the base of the eighth PNP transistor (Q8) and the ninth PNP transistor (Q9), respectively, to control a current ratio; A fourteenth PNP transistor Q14 and a fifteenth PNP transistor Q15 coupled to the collector and the base of the ninth PNP transistor Q9 and the tenth PNP transistor Q10 to control a current ratio; A current sensing resistor connected between the emitter and the supply voltage terminal of the eighth PNP transistor Q8 / ninth PNP transistor Q9 to the fourteenth PNP transistor Q14 / fifteenth PNP transistor Q15 to prevent overcurrent An oscillator comprising (R8 to R11). The method of claim 5, The current control means 300 controls the frequency and duty ratio by a collector current that increases in proportion to the number of collectors of the multi transistors Q12 / Q13 to Q14 / 15 connected to the output terminal of the comparison means 200. An oscillator characterized by. The method of claim 1, The output voltage control means 400 includes a pull-up resistor (R2) for controlling the output voltage; And a sixteenth NPN transistor (Q16) for controlling the swing of the output voltage to reduce the output potential. The method of claim 1, The oscillation control means 500 includes a timing capacitor (C) capable of varying the frequency of the charge time and the discharge time by the output voltage; And a timing resistor (R1) for adjusting the duty ratio of the oscillation output in proportion to the input voltage Vin. The method of claim 1, The oscillation control means (500) is characterized in that the timing resistor (R1) and the timing capacitor (C) comprises an integrator for preventing high frequency oscillation. The method of claim 1, An oscillator, characterized in that for controlling the current ratio of the current control means 300 according to the voltage level of the variable frequency control means (100).

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