JPH05308256A - Triangular wave oscillating circuit - Google Patents

Abstract

PURPOSE:To provide the triangular wave oscillating circuit whose oscillating frequency and oscillating amplitude are stable even when a drive power supply voltage is subjected to change. CONSTITUTION:A constant voltage source 3 is used for a constant current source by using an amplifier 4, a buffer 6 and a resistor 5, its constant current is used for a charging current and a discharge current for a capacitor 20, and a voltage across the capacitor 20 is compared with a voltage at other terminal of a resistor 26 whose one terminal connects to the constant voltage source 30 at a comparator comprising transistors (TRs) 16,17. A constant current flows in/out of the resistor 26 in interlocking with the changeover of charging/ discharging of the capacitor 20 and then the voltage at the other terminal of the resistor 26 is switched. The voltage across the capacitor 20 is changed in a triangle shape by comparing the voltage at the other terminal of the resistor 26 with the voltage across the capacitor 20 to switch the charging/ discharging of the capacitor 20 and the flowing in/out of the current to/from the resistor 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triangular wave oscillator circuit for generating a periodic triangular wave voltage.

[0002]

2. Description of the Related Art An example of a conventional triangular wave oscillator circuit is shown in FIG. An example of this is shown in Nikkei Tuna Hill Co., Ltd., Semiconductor Circuit Design Technology (published April 4, 1987). In FIG. 5, 1 is a power supply terminal and 2 is a ground terminal (GND). 41, 43, 44 are PNP transistors, 45-47 are NPN transistors, 48,
49 is a PNP transistor, 50 is an NPN transistor, 42, 51-53 are resistors, and 54 is a capacitor. The PNP transistors 41, 43 and 44 form a current mirror circuit. Similarly, the NPN transistors 45 and 47 and the PNP transistors 48 and 49 also constitute current mirror circuits, respectively. Transistor 4
Reference numerals 6 and 47 form a differential circuit and form a comparator.
The NPN transistor 47 corresponds to two NPN transistors 45. That is, the current mirror ratio is doubled.

In the above structure, when the driving power supply voltage V _CC is applied between the power supply terminal 1 and the ground terminal 2, a current flows through the series circuit of the PNP transistor 41 and the resistor 42, and the current mirror with the PNP transistor 41. The same current as that of the PNP transistor 41 also flows through the PNP transistors 43 and 44 that form the circuit.

An electric charge is accumulated in the capacitor 54 by the current flowing through the PNP transistor 43, which causes the voltage of the capacitor 54 to rise and the comparator (differential circuit).
When the base voltage of the NPN transistor 46 that forms the NPN transistor 46 becomes higher than the base voltage of the NPN transistor 50 that also forms the comparator (differential circuit), the NPN transistor 46 turns on and the NPN transistor 50
Turns off.

Further, the PNP transistor 44 and the NPN transistor 45 are connected in series, the current flowing through the PNP transistor 44 flows through the NPN transistor 45 as it is, and the NPN transistor 45 and the NPN transistor 47 form a current mirror circuit. Cage, N
Since the PN transistor 47 is designed to correspond to two NPN transistors 45, the NPN transistor 47
A current twice as large as the current of the NPN transistor 45 will flow through.

The current of the NPN transistor 47 is NPN.
Before the transistor 46 is turned on, that is, the NPN
When the transistor 50 is in the ON state, the current flows through the NPN transistor 50 and turns the PNP transistors 48 and 49 into the ON state. However, when the charging of the capacitor 54 progresses and the NPN transistor 46 is turned on and the NPN transistor 50 is turned off as described above, the PNP transistors 48 and 49 are turned off, and the current flows through the NPN transistor 46. Become. This current flows as a current flowing through the PNP transistor 43 and a discharging current of the capacitor 54. Therefore, the discharging current having the same value as the previous charging current flows through the capacitor 54.

Then, the discharge of the capacitor 54 progresses, the voltage of the capacitor 54 decreases, and the base voltage of the NPN transistor 46 forming the comparator (differential circuit) is also the NPN forming the comparator (differential circuit).
When it becomes lower than the base voltage of the transistor 50, the NPN
The transistor 46 is turned off, the NPN transistor 50 is turned on, the current of the NPN transistor 47 flows through the NPN transistor 50 again, the charging of the capacitor 54 is started, and this operation is repeated thereafter. The voltage will change in a triangular waveform.

At this time, the base voltage of the NPN transistor 50 of the comparator has different values because the ON / OFF states of the NPN transistor 50 and the PNP transistors 48 and 49 are inverted when the capacitor 54 is charged and discharged. First, the NPN transistor 5 of the comparator
The base voltage V ₅₀ (OFF) when 0 is off is expressed by the following equation because the PNP transistors 48 and 49 are in the off state.

[0009]

[Equation 1]

Here, R ₅₁ , R ₅₂ , and R ₅₃ are resistance values of the resistors ₅₁ , ₅₂ , and ₅₃ , respectively. V _CC is a drive power supply voltage applied between the power supply terminal 1 and the ground terminal 2. Next, the base voltage V ₅₀ (ON) when the NPN transistor 50 of the comparator is on is expressed by the following equation since the PNP transistors 48 and 49 are on.

[0011]

[Equation 2]

Here, V _CE50 (SAT) is the collector-emitter saturation voltage of the NPN transistor 50. Then, the capacitor 54 is charged and discharged with the voltages represented by the equations 1 and 2 as the lower limit and the upper limit, respectively, and the voltage of the capacitor 54 is taken out as the output voltage of the triangular wave oscillation circuit.

[0013]

In the conventional example shown in FIG. 5, as is clear from the circuit diagram, when the drive power supply voltage V _CC changes, the charging / discharging current to the capacitor 54 changes, so that the charging / discharging changes. There is an inconvenience that the time changes and the oscillation frequency changes. Further, as is clear from the equations 1 and 2, there is a disadvantage that the amplitude of the triangular wave oscillation waveform changes due to the change of the driving power supply voltage V _CC .

Therefore, an object of the present invention is to provide a triangular wave oscillating circuit capable of stabilizing the oscillation frequency and the amplitude regardless of the change of the driving power supply voltage.

[0015]

In the triangular wave oscillator circuit according to the first aspect of the invention, the constant voltage source and the first resistor constitute a constant current source. A capacitor that allows the constant current regulated by the constant current source to flow in and out as a charging / discharging current is provided, and a voltage source is provided.One end is connected to this voltage source and the constant current regulated by the constant current source flows from the other end. -A second resistance is provided for the outflow. Further, a comparator for comparing the voltage of the capacitor with the voltage of the other end of the second resistor is provided, and in response to the output of the comparator, a constant current flows in and out of the capacitor and a constant current flows in to the second resistor. A switch element is provided to switch the outflow.

According to another aspect of the present invention, there is provided a triangular wave oscillating circuit comprising a third and a fourth resistors for dividing the voltage of the driving power source and a buffer for receiving the divided voltage by the third and the fourth resistors. It constitutes a voltage source. According to another aspect of the triangular wave oscillator circuit of the present invention, first and second transistors forming a differential circuit with emitters connected in common and third and fourth transistors connected in Darlington to the first and second transistors, respectively. The comparator of claim 1 is constituted by a transistor, the voltage of the capacitor is applied to the base of the third transistor, and the voltage of the other end of the second resistor is applied to the base of the fourth transistor. The switch element is composed of a fifth transistor, and the base of the fifth transistor is connected to the collector of the first transistor.

According to a fourth aspect of the present invention, in the triangular wave oscillating circuit, the comparator of the first aspect is constituted by the first and second transistors which form a differential circuit with the emitters commonly connected, and the base of the first transistor constitutes the differential circuit. The voltage of the first capacitor is applied, the voltage of the other end of the second resistor of claim 1 is applied to the base of the second transistor, and the switch element of claim 1 is configured by a third transistor. The base of the third transistor is connected to the collector of the first transistor, the emitter of the fourth transistor is connected to the connection point between the capacitor and the base of the first transistor, and the base of the fourth transistor is used as a constant voltage source. And the collector of the fourth transistor is connected to the drive power supply.

[0018]

According to the structure of claim 1, the constant current regulated by the constant current source flows into the capacitor as a charging current, so that the voltage of the capacitor linearly rises and, conversely, the constant current is greater than that of the capacitor. By flowing out as a discharge current, the voltage of the capacitor drops linearly. The rising and falling slopes of the capacitor voltage at this time are not affected by fluctuations in the drive power supply voltage because the charging and discharging of the capacitor are performed by the inflow and outflow of the constant current.

The current defined by the constant current source flows into or out of the capacitor, and at the same time, it flows in or out from the other end of the second resistor connected to the voltage source. When a constant current flows into the second resistor, the voltage at the other end of the second resistor becomes higher than the voltage of the voltage source by a voltage obtained by multiplying the resistance value of the second resistor by the inflow current value, and vice versa. Second
When a constant current flows out from the resistance of the second resistance, the voltage at the other end of the second resistance becomes lower than the voltage of the voltage source by a voltage obtained by multiplying the resistance value of the second resistance by the outflow current value.

As a result, the change in the voltage at the other end of the second resistor when the current flows in and out of the second resistor is obtained by multiplying the resistance value of the second resistor by the inflow current value. The sum of the voltage and the voltage obtained by multiplying the resistance value of the second resistor by the outflow current value is not related to the drive power supply voltage and is not affected by the fluctuation of the drive power supply voltage. The comparator compares the voltage of the capacitor with the voltage at the other end of the second resistor, and the switch element responds to the output of the comparator by inflowing and outflowing a constant current into the capacitor and inflowing a constant current into the second resistor. The outflow will be linked and switched. At this time, when a constant current flows into the capacitor for charging, the current also flows into the second resistor, and the voltage at the other end of the second resistor has a higher value. On the contrary, when a constant current flows out from the capacitor and discharge is performed, current also flows out from the second resistor, and the voltage at the other end of the second resistor has a lower value.

As described above, the comparator compares the voltage of the capacitor to which the charging current and the discharging current are supplied with the voltage drop of the second resistor into and out of which the current flows, and based on the comparison result of the comparator, the switch element. By switching the charging / discharging of the capacitor and the inflow / outflow of the current to / from the second resistor, the voltage of the capacitor is in the range from the higher value to the lower value of the voltage at the other end of the second resistor. As a result, a triangular wave voltage is obtained, and the triangular wave voltage is obtained. The gradient and amplitude of this triangular wave voltage are determined by the constant current specified by the constant current source, so it is stable regardless of fluctuations in the drive power supply voltage. Can be made

According to the second aspect of the present invention, the voltage obtained by dividing the drive power supply voltage becomes the voltage of the constant voltage source. Therefore, even when the drive power supply voltage changes, the center voltage of oscillation corresponds to the drive power supply voltage. Therefore, the distortion of the oscillation waveform can be suppressed. According to the configuration of claim 3, even if the capacitor is discharged to a low potential, a voltage that is almost twice the base-emitter voltage can be obtained on the collector side of the first transistor, and the first transistor is a switch element. The transistor of No. 5 can be normally started and the oscillation operation can be continued.

According to the structure of claim 4, when the capacitor is discharged to a low potential, the charging transistor is turned on, and the charging current is supplied from the power supply to the capacitor to raise the voltage of the capacitor. A sufficient voltage can be obtained on the collector side of the transistor for starting the fourth transistor, which is a switch element, so that the fourth transistor can be started normally and the oscillation operation can be continued.

[0024]

Embodiments of the present invention will now be described with reference to the drawings. [First Embodiment] FIG. 1 is a circuit diagram of a triangular wave oscillator circuit according to a first embodiment of the present invention. As shown in FIG. 1, this triangular wave oscillator circuit has a power supply terminal 1 and a ground terminal (G
The drive power supply voltage V _CC is applied between ND) 2. In addition, the first constant voltage source 3 is connected to the amplifier 4 and the NPN transistor 6
A constant current source is formed by adding the first resistor 5 via the buffer consisting of.

The constant current source is connected in series with the PNP transistor 7 and connected to the power supply terminal 1 and the ground terminal 2. The PNP transistor 7 and the PNP transistors 8 to 11, whose bases are commonly connected, form an upper current mirror circuit. PNP transistors 8-10
Are respectively connected in series with the NPN transistors 12, 13 and 14, respectively, and are connected to the power supply terminal 1 and the ground terminal 2.

The NPN transistors 12, 13, 14 are
The bases are commonly connected to form a lower current mirror circuit. However, the NPN transistors 12 and 13 are
Designed to correspond to two PN transistors 14, that is, designed so that the current mirror ratio is doubled, and that twice the current flowing through the NPN transistor 14 flows through the NPN transistors 12 and 13, respectively. become.

Another PN of the upper current mirror circuit
The P-transistor 11 is connected in series to PNP transistors 16 and 17 whose emitters are commonly connected to each other to form a differential circuit and to form a comparator. NPN transistors 18 and 19 serving as loads are connected in series to the PNP transistors 16 and 17, respectively, and these series connection circuits are connected to the power supply terminal 1 and the ground terminal 2.

Further, a series circuit of a current source 31 and a constant voltage source 30 is connected between the power supply terminal 1 and the ground terminal 2, and one end of the second resistor 26 is connected to the connection point of the current source 31 and the constant voltage source 30. Is connected, and the other end of the second resistor 26 constitutes a PNP transistor 16 which constitutes a comparator.
Connected to the base of. P that constitutes a comparator
A capacitor 20 is connected between the base of the NP transistor 17 and the ground terminal 2.

The connection point between the second resistor 26 and the base of the PNP transistor 16 is connected to the connection point between the PNP transistor 8 and the NPN transistor 12, and the connection point between the capacitor 20 and the base of the PNP transistor 17 is the PNP transistor. 9 and NPN transistor 1
It is connected to three connection points. In addition, the NPN transistor 15 which is a switch element has N between the collector and the emitter.
It is connected in parallel to the PN transistor 14, and the base of the NPN transistor 15 is connected to the collector of the PNP transistor 17.

The connection point between the first resistor 5 and the NPN transistor 6 will be referred to as point A in the following description, the base of the PNP transistor 17 will be referred to as point B, and the PNP transistor 1 will be described.
The base of 6 is marked as C point. Next, the operation of this triangular wave oscillator circuit will be described. Power terminal 1 and ground terminal 2
If the drive power supply voltage V _CC is applied between the first constant voltage source 3 and
A constant current flows through a constant current source composed of the amplifier 4, the first resistor 5 and the NPN transistor 6, and this current flows through the PNP transistor 7 which constitutes the upper side current mirror circuit. As a result, the same current flows in the PNP transistors 8 to 11, respectively.

When the power is turned on, the capacitor 20 is not charged, the potential at the point B is lower than the potential at the point C, and the comparator composed of the PNP transistors 16 and 17 turns off the PNP transistor 16. The PNP transistor 17 is on, the current of the PNP transistor 11 flows through the PNP transistor 17, the NPN transistor 15 is on, the current of the PNP transistor 10 flows through the NPN transistor 15, and the lower current mirror circuit NPN transistor 12 to be configured,
13, 14 are off.

In such a state, the current of the PNP transistor 9 flows into the capacitor 20 as a charging current, the voltage of the capacitor 20 rises linearly, and this voltage becomes the base voltage of the PNP transistor 17.
At this time, the current of the PNP transistor 8 is the second resistor 2
6 and the voltage at the other end of the second resistor 26 is applied to the constant voltage source 3
The voltage rises above the voltage of 0 by the voltage drop of the second resistor 26, and this voltage becomes the base voltage of the PNP transistor 16.

Thereafter, the charging of the capacitor 20 progresses, the voltage of the capacitor 20 rises, and the PNP transistor 17
When the base voltage of is higher than the base voltage of the PNP transistor 16, the PNP transistor 16 is turned on,
The PNP transistor 17 is turned off. As a result, NP
The N-transistor 15 is turned off, and the NPN transistors 12 to 14 forming the lower current mirror circuit are operated.

That is, the current of the PNP transistor 11 flows through the PNP transistor 16 and the PNP transistor 1
A current of 0 flows to the NPN transistor 14, and the NPN transistors 12 and 13 respectively receive the NPN transistor 1
Double the current of 4 flows. At this time, half of the current flowing in the NPN transistor 13 flows as the current of the PNP transistor 9, and the other half flows as the discharging current of the capacitor 20, and the capacitor 20 discharges the same value as the charging current. The voltage of 20 drops linearly with the same gradient as when charging. Also, NP
Half of the current flowing through the N-transistor 12 flows as the current of the PNP transistor 8, and the other half flows through the constant voltage source 30.
Flows as a current flowing from the second resistor 26 through
The voltage at the other end of the second resistor 26 is lower than the voltage of the constant voltage source 30 by the voltage drop of the second resistor 26, and this voltage becomes the base voltage of the PNP transistor 16.

After that, the discharge of the capacitor 20 progresses, the voltage of the capacitor 20 drops, and the PNP transistor 17
Is lower than the base voltage of the PNP transistor 16, the on / off states of the PNP transistors 16 and 17 are inverted, the charging of the capacitor 20 is restarted, and the above operation is repeated. It will change wavy.

In the above repeating operation, the voltage V _C (up1) at the point C during the period when the PNP transistor 16 is off and the PNP transistor 17 is on to charge the capacitor 20 and the voltage of the capacitor 20 is rising is It becomes like the following formula.

[0037]

[Equation 3]

Here, R ₅ and R ₂₆ are resistors 5 and 2, respectively.
6, and V ₃ and V ₃₀ are the voltage values of the constant voltage source 3 and the constant voltage source 30, respectively. On the other hand, the voltage V _C (down1) at the point C during the period in which the PNP transistor 16 is on and the PNP transistor 17 is off and the capacitor 20 is discharged and the voltage of the capacitor 20 is decreasing is given by the following equation.

[0039]

[Equation 4]

The oscillation amplitude V _W1 in the above operation is the difference between the above _equations 3 and 4,

[0041]

[Equation 5]

Is represented by As mentioned above,
In the triangular wave oscillator circuit of the embodiment, the voltage of the capacitor 20 is
The slope of the pressure rise and fall depends on the charging of the capacitor 20 and
Since the discharge is performed by inflow and outflow of constant current,
Source voltage V_CCOf the second resistor 2
Second when current flows in and out of 6
Of the voltage at the other end of the resistor 26 of
The resistance of the second resistor 26 and the voltage obtained by multiplying the resistance value by the inflow current value.
It becomes the sum of the resistance value and the voltage obtained by multiplying the outflow current value.
Voltage V _CCDrive power supply voltage V_CCShadow of fluctuations
Not affected. Therefore, the voltage of the capacitor 20 and the
Comparing with the voltage of the other end of the resistor 26 of 2 by the comparator
Drive voltage when the triangular wave is oscillated.
V_CCCan stabilize the oscillation frequency regardless of the fluctuation of
In addition, the oscillation amplitude can be stabilized.

In each of the above-mentioned embodiments, the mirror ratio of the upper current mirror and the lower current mirror is set to be double and the charging current and discharging current of the capacitor 20 are set to the same value, but the mirror ratio is changed. As a result, the setting of the charging current and the discharging current can be changed, and the duty ratio of the triangular wave oscillation waveform can be set arbitrarily. [Second Embodiment] FIG. 2 is a circuit diagram of a triangular wave oscillator circuit according to a second embodiment of the present invention.

As shown in FIG. 2, this triangular wave oscillating circuit is obtained by modifying the configurations of the current source 31 and the constant voltage source 30 in FIG. 1 as follows. That is, the series circuit of the resistors 21 and 22 is connected between the power supply terminal 1 and the ground terminal 2, and the divided voltage by the resistors 21 and 22 is input to the buffer by the amplifier 23, the NPN transistor 24, and the resistor 25. Of the NPN transistor 24, and one end of the second resistor 26 is connected to the output terminal of the NPN transistor 24.

Other configurations are the same as those in FIG. In this embodiment, PNP transistor 16 is off and PN
The voltage V _C (up2) at the point C during the period when the P-transistor 17 is turned on and the capacitor 20 is charged and the voltage of the capacitor 20 is rising is given by the following equation.

[0046]

[Equation 6]

Here, R ₂₁ and R ₂₂ are resistance values of the resistors 21 and ₂₂ , respectively. On the other hand, when the PNP transistor 16 is on, P
The voltage V _C (down2) at the point C during the period in which the NP transistor 17 is turned off, the capacitor 20 is discharged, and the voltage of the capacitor 20 is decreasing is given by the following equation.

[0048]

[Equation 7]

Further, the oscillation amplitude V _W2 is the difference between the above _equations 6 and 7,

[0050]

[Equation 8]

Is represented as The points other than the above are the same as those in the first embodiment. According to the triangular wave oscillator circuit of this embodiment, the voltage obtained by dividing the drive power supply voltage V _CC is the voltage source 3 of FIG.
Since the voltage of the voltage source corresponds to 0, the drive power supply voltage V
_{When CC} changes, the center voltage of oscillation is the drive power supply voltage V
It follows that it corresponds to _CC , especially the drive power supply voltage V
_{When CC} decreases, the power supply can be used in a wide range, and the range in which the oscillation waveform is distorted can be narrowed. That is, it is possible to prevent the oscillation waveform from being easily distorted even if the drive power supply voltage V _CC fluctuates.

[Third Embodiment] FIG. 3 is a circuit diagram of a peripheral portion of a comparator of a triangular wave oscillator circuit according to a third embodiment of the present invention. This triangular wave oscillator circuit, as shown in FIG.
The PNP transistor 27 is connected to the PNP transistor 16 in a Darlington connection, and the PNP transistor 17 is connected.
Darlington connection of PNP transistor 28 to
The other end of the second resistor is connected to the base of a PNP transistor 27 instead of the P transistor 16, and the comparator 20 is connected to the base of a PNP transistor 28 instead of the PNP transistor 17. Other configurations are the same as those in FIG. 1 or FIG.

For example, in the case where the comparator is composed of the PNP transistors 16 and 17 having a one-stage differential structure as shown in FIG. 1, when the electric charge of the comparator 20 is completely discharged, the potential at the point B becomes Approximately 0V, PN
When the P-transistor 17 is turned on, the collector potential of the PNP transistor 17 does not rise to about 0.6 V (transistor base-emitter on-voltage), and the PN
The NPN transistor 15, which is a switching element having the base connected to the collector of the P transistor 17, does not reach the ON state, and oscillation does not start.

In order to avoid such a state, the transistors forming the comparator may have the Darlington connection configuration as shown in FIG. 3 as described above. In this Darlington connection configuration, even if the potential at the point B ′, that is, the base of the PNP transistor 28 becomes 0V, the potential of the collector of the PNP transistor 17 is approximately 1.2V (the base-emitter voltage of the transistor). Of 2
), And therefore the NPN transistor 15
Can be driven and oscillation can be started.

The points other than the above are the same as those in the above-described embodiment. According to the triangular wave oscillator circuit of this embodiment, even if the capacitor 20 is discharged to a low potential, the PNP transistor 1
A voltage approximately twice the base-emitter voltage can be obtained on the collector side of 7, and the NPN transistor 15, which is a switching element, can be normally started and the oscillation operation can be continued.

[Fourth Embodiment] FIG. 4 shows a circuit diagram of a main portion of a fourth embodiment of the present invention. This triangular wave oscillator circuit
As shown in FIG. 4, the collector of the NPN transistor 29 is connected to the power supply terminal 1 in FIG.
The emitter of the N-transistor 29 is connected to the point B, that is, the capacitor 20, and the base thereof is connected to the constant current source, that is, the point A, and other configurations are the same as those of the embodiment of FIG. 1 or 2.

As described above, when the NPN transistor 29 is provided, when the electric charge of the capacitor 20 is discharged and the potential at the point B drops too much, the NPN transistor 29 is turned on and the NPN transistor from the power supply terminal 1 to the point B is reached. A current flows through the emitter of 29, charges the capacitor 20, and raises the voltage of the capacitor 20. As a result, B
The potential at the point rises, the comparator including the PNP transistors 16 and 17 operates normally, and the collector voltage of the PNP transistor 17 can be set to a value sufficient to turn on the NPN transistor 15.

In other words, in this embodiment, by preventing the potential drop at the point B, the voltage at the collector of the PNP transistor 17 is maintained at a value sufficient to turn on the NPN transistor 15, so that the third voltage is maintained. Oscillation can be activated as in the embodiment. According to the triangular wave oscillator circuit of this embodiment, when the capacitor 20 is discharged to a low potential, the NPN transistor 15 for charging is turned on and the charging current is supplied from the driving power source to the capacitor 20 to raise the voltage of the capacitor 20. Therefore, it is possible to obtain a sufficient voltage on the collector side of the PNP transistor 17 for activating the NPN transistor 15 which is a switching element.
The transistor 15 can be normally started and the oscillation operation can be continued.

[0059]

According to the triangular wave oscillating circuit of the first aspect of the present invention, the gradient of the rise and fall of the voltage of the capacitor is that the charging and discharging of the capacitor are performed by the inflow and outflow of the constant current, and therefore the fluctuation of the drive power supply voltage. In addition, the change in voltage at the other end of the second resistor when the current flows into and out of the second resistor is determined by the inflow current value being added to the resistance value of the second resistor. It is the sum of the multiplied voltage and the voltage obtained by multiplying the resistance value of the second resistor by the outflow current value, which is irrelevant to the drive power supply voltage and is not affected by fluctuations in the drive power supply voltage.
Therefore, when the triangular wave oscillation is performed by comparing the voltage of the capacitor and the voltage of the other end of the second resistor with the comparator, the oscillation frequency can be stabilized regardless of the fluctuation of the drive power supply voltage. The oscillation amplitude can be stabilized.

According to the triangular wave oscillator circuit of the second aspect,
The voltage at the other end of the second resistor follows the fluctuation of the driving power supply voltage. Therefore, when the driving power supply voltage changes, the center voltage of oscillation follows the driving power supply voltage. Distortion can be reduced. Claim 3
According to the triangular wave oscillator circuit described, even if the capacitor is discharged to a low potential, it is possible to obtain a voltage approximately twice as high as the base-emitter voltage on the collector side of the first transistor, and the fifth element which is a switch element. The transistor can be started normally and the oscillation operation can be continued.

According to the triangular wave oscillator circuit of the fourth aspect,
When the capacitor is discharged to a low potential, the charging transistor is turned on, and the charging current is supplied from the power supply to the capacitor to increase the voltage of the capacitor. Therefore, the collector side of the first transistor is provided with the fourth switching element. A voltage sufficient for starting the transistor can be obtained, the fourth transistor can be normally started, and the oscillation operation can be continued.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a triangular wave oscillator circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a triangular wave oscillator circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a modified circuit example of a comparator.

FIG. 4 is a circuit diagram showing an example of a transistor added in the embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional example of a triangular wave oscillator circuit.

[Explanation of symbols]

 1 Power Supply Terminal 2 Ground Terminal 3 Constant Voltage Source 4 Buffer 5 First Resistor 6 NPN Transistor 7 to 11 PNP Transistor 12 to 15 NPN Transistor 16, 17 PNP Transistor 18, 19 PNP Transistor 20 Capacitor 21, 22 Resistor 23 Buffer 24 NPN Transistor 25 Resistance 26 Second resistance 27, 28 PNP transistor 29 NPN transistor 30 Constant voltage source 31 Current source

Claims (4)

[Claims] 1. A constant voltage source, a first resistor that forms a constant current source together with the constant voltage source, and a capacitor into and out of which a constant current defined by the constant current source flows as a charging / discharging current. A voltage source, a second resistor having one end connected to the voltage source and a constant current defined by the constant current source flowing in and out from the other end, the voltage of the capacitor and the other end of the second resistor. A triangular wave provided with a comparator for comparing a voltage and a switching element that switches inflow and outflow of a constant current with respect to the capacitor and inflow and outflow of a constant current with respect to the second resistor in response to an output of the comparator. Oscillator circuit. 2. The triangular wave according to claim 1, wherein the voltage source is composed of third and fourth resistors for dividing the voltage of the driving power source, and a buffer which receives the divided voltage by the third and fourth resistors. Oscillator circuit. 3. First and second transistors forming a differential circuit with emitters connected in common, and the first and second transistors.
Comparing a third transistor and a fourth transistor, which are Darlington-connected to the transistor, respectively, to apply a capacitor voltage to the base of the third transistor, and to add a second resistor to the base of the fourth transistor. The voltage of the other end of the transistor is applied, the switch element is composed of a fifth transistor, and the base of the fifth transistor is connected to the collector of the first transistor.
The triangular wave oscillator circuit described. 4. A comparator is composed of first and second transistors forming a differential circuit with emitters connected in common, and a voltage of a capacitor is applied to the base of the first transistor to make a comparator of the second transistor. A voltage at the other end of the second resistor is applied to the base, the switch element is formed of a third transistor, the base of the third transistor is connected to the collector of the first transistor, and the capacitor and the first transistor are connected. The emitter of a fourth transistor is connected to a connection point with the base of the first transistor, the base of the fourth transistor is connected to a constant voltage source, and the collector of the fourth transistor is connected to a driving power supply. 1. The triangular wave oscillator circuit according to 1.