JP7206062B2 - Oscillator circuit and method of controlling the oscillator circuit - Google Patents

Description

The present invention relates to an oscillator circuit and a control method for the oscillator circuit.

Conventionally, in an oscillator circuit, a comparator compares the charging and discharging voltage of an external capacitor with a constant current with a threshold voltage, and by switching charging and discharging according to the comparison result, a triangular wave signal corresponding to the voltage of the external capacitor is generated. had generated.

JP-A-2003-188693

Conventionally, however, when generating a triangular wave signal of high frequency, overshoot of the triangular wave signal occurs due to response delay of the comparator, resulting in a problem that high frequencies cannot be properly handled. Such problems could not be solved by increasing the charging current or reducing the size of the capacitor.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an oscillation circuit and an oscillation circuit control method capable of generating a triangular wave signal having an appropriate waveform in which overshoot is suppressed even when the frequency of the triangular wave signal is high. .

An oscillation circuit according to an aspect of the present invention includes:
a charging/discharging circuit that controls charging/discharging of a capacitor with power supplied from a power source and generates a triangular wave signal corresponding to the charged voltage of the capacitor;
The charging/discharging circuit receives the triangular wave signal and the reference signal, compares the voltage value of the triangular wave signal with the reference voltage value of the reference signal, and switches between charging and discharging of the capacitor according to the comparison result. a charge/discharge control circuit for controlling the
a reference voltage value switching circuit that generates the reference signal, outputs it to the charge/discharge control circuit, and switches the reference voltage value of the reference signal;
a reference signal adjustment circuit that adjusts the reference signal,
The reference voltage value switching circuit is
In order to switch the capacitor from discharging to charging by the charge/discharge control circuit, the reference voltage value of the reference signal is switched from a lower limit voltage value to an upper limit voltage value of the triangular wave signal, while the capacitor is controlled by the charge/discharge control circuit. switching the reference voltage value of the reference signal from the upper limit voltage value to the lower limit voltage value to switch from charging to discharging of the
The reference signal adjustment circuit is
When the reference voltage value switching circuit switches the reference voltage value to the upper limit voltage value, the reference voltage value output to the charge/discharge control circuit becomes a first reference voltage value lower than the upper limit voltage value. On the other hand, when the reference voltage value switching circuit switches the reference voltage value to the lower limit voltage value, the reference voltage value output to the charge/discharge control circuit is the lower limit voltage value. adjusting the reference signal to a second reference voltage value that is higher than the first reference voltage value and lower than the first reference voltage value.

In the oscillation circuit,
The charge/discharge control circuit is
controlling the charge/discharge circuit to switch from charging to discharging the capacitor when the voltage value of the triangular wave signal reaches the first reference voltage value during charging of the capacitor;
The charging/discharging circuit may be controlled to switch from discharging to charging the capacitor when the voltage value of the triangular wave signal reaches the second reference voltage value during discharging of the capacitor.

In the oscillation circuit,
The reference signal may be a triangular wave signal having an amplitude smaller than that of the triangular wave signal.

In the oscillation circuit,
The reference signal adjustment circuit may adjust the reference signal such that the higher the frequency of the triangular wave signal, the smaller the first reference voltage value and the larger the second reference voltage value.

In the oscillation circuit,
The reference signal adjustment circuit changes the reference voltage value output to the charge/discharge control circuit to the second reference voltage value during a period in which the reference voltage value is maintained at the upper limit voltage value by the reference voltage value switching circuit. to the first reference voltage value, and output to the charge/discharge control circuit during a period in which the reference voltage value is maintained at the lower limit voltage value by the reference voltage value switching circuit The reference signal may be adjusted such that the reference voltage value applied decreases from the first reference voltage value to the second reference voltage value.

In the oscillation circuit,
The charge/discharge control circuit has a first input terminal for inputting the triangular wave signal, a second input terminal for inputting the reference signal, and outputs a control signal for controlling charging/discharging of the capacitor by the charge/discharge circuit. and a comparator having an output terminal for

In the oscillation circuit,
The reference voltage value switching circuit is
a plurality of resistors connected in series between the power supply and a fixed potential;
The contacts of the second input terminal for the plurality of resistors are a first contact that divides the voltage of the power supply to the upper limit voltage of the triangular wave signal, and a second contact that divides the voltage of the power supply to the lower limit voltage of the triangular wave signal. and a switch for switching between
The reference signal adjustment circuit is
adjusting the reference signal so that the reference voltage value output to the charge/discharge control circuit becomes the first reference voltage value when the second input terminal is connected to the first contact;
The reference signal may be adjusted such that the reference voltage value output to the charge/discharge control circuit becomes the second reference voltage value when the second input terminal is connected to the second contact. .

In the oscillation circuit,
The switch connects the second input terminal to the first contact when the control signal output from the output terminal instructs charging of the capacitor, and the control signal instructs discharging of the capacitor. case, the second input terminal may be connected to the second contact.

In the oscillation circuit,
The reference signal adjustment circuit may have a second capacitor having one end connected to the switch and the second input terminal and the other end connected to a fixed potential.

In the oscillation circuit,
The second capacitor acts as a first resistor between the first contact and the second contact among the plurality of resistors when the second input terminal is connected to the first contact by the switch. and a second resistor between the second contact and the fixed potential, and may be connected to the second resistor when the switch connects the second input terminal to the second contact. .

In the oscillation circuit,
The reference signal adjustment circuit has a second capacitor having one end connected to the switch and the second input terminal and the other end connected to a fixed potential,
The switch is
a first switching element having one end connected to one end of the second capacitor, the other end connected to the first contact, and a control terminal connected to the output terminal side of the comparator;
a second switching element having one end connected to one end of the second capacitor, the other end connected to the second contact, and a control terminal connected to the output terminal side of the comparator.

In the oscillation circuit,
the first input terminal is a non-inverting input terminal;
the second input terminal is an inverting input terminal;
The comparator outputs a high-level control signal from the output terminal when switching from charging to discharging the capacitor, and outputs a low-level control signal from the output terminal when switching from discharging to charging the capacitor. and
The reference voltage switching circuit further includes an inverter having one end connected to the output terminal of the comparator and the other end connected to a control terminal of the first switching element and a control terminal of the second switching element,
The first switching element is turned on by a first inverted signal obtained by logically inverting the low level control signal by the inverter, and turned off by a second inverted signal obtained by logically inverting the high level control signal by the inverter,
The second switching element may be turned off by the first inversion signal and turned on by the second inversion signal.

In the oscillation circuit,
the first input terminal is a non-inverting input terminal;
the second input terminal is an inverting input terminal;
The comparator outputs a high-level control signal from the output terminal when switching from charging to discharging the capacitor, and outputs a low-level control signal from the output terminal when switching from discharging to charging the capacitor. and
the first switching element is turned on by the low level control signal and turned off by the high level control signal;
The second switching element may be turned off by the low level control signal and turned on by the high level control signal.

In the oscillation circuit,
The charge/discharge circuit is
a first constant current circuit connected between the power supply and one end of the capacitor;
a transistor having one end connected to one end of the capacitor and having a control terminal connected to the output terminal of the comparator;
and a second constant current circuit connected between the other end of the transistor and a fixed potential.

A control method for an oscillator circuit according to an aspect of the present invention includes:
a charging/discharging circuit that controls charging/discharging of a capacitor with power supplied from a power source and generates a triangular wave signal corresponding to the charged voltage of the capacitor;
The charging/discharging circuit receives the triangular wave signal and the reference signal, compares the voltage value of the triangular wave signal with the reference voltage value of the reference signal, and switches between charging and discharging of the capacitor according to the comparison result. a charge/discharge control circuit for controlling the
a reference voltage value switching circuit that generates the reference signal, outputs it to the charge/discharge control circuit, and switches the reference voltage value of the reference signal;
controlling an oscillation circuit comprising a reference signal adjustment circuit that adjusts the reference signal;
The control of the oscillation circuit includes:
The reference voltage value switching circuit
In order to switch the capacitor from discharging to charging by the charge/discharge control circuit, the reference voltage value of the reference signal is switched from a lower limit voltage value to an upper limit voltage value of the triangular wave signal, while the capacitor is controlled by the charge/discharge control circuit. switching the reference voltage value of the reference signal from the upper limit voltage value to the lower limit voltage value to switch from charging to discharging of the
The reference signal adjustment circuit is
When the reference voltage value switching circuit switches the reference voltage value to the upper limit voltage value, the reference voltage value output to the charge/discharge control circuit becomes a first reference voltage value lower than the upper limit voltage value. On the other hand, when the reference voltage value switching circuit switches the reference voltage value to the lower limit voltage value, the reference voltage value output to the charge/discharge control circuit is the lower limit voltage value. adjusting the reference signal to a second reference voltage value that is higher than the first reference voltage value and lower than the first reference voltage value.

An oscillation circuit according to one embodiment of the present invention includes a charging/discharging circuit that controls charging/discharging of a capacitor with power supplied from a power source and generates a triangular wave signal according to the charged voltage of the capacitor, and a triangular wave signal and a reference signal. A charge/discharge control circuit that compares the voltage value of the input triangular wave signal with the reference voltage value of the reference signal, and controls the charge/discharge circuit to switch between charging and discharging of the capacitor according to the comparison result; a reference voltage value switching circuit that generates and outputs to a charge/discharge control circuit and switches the reference voltage value of the reference signal; and a reference signal adjustment circuit that adjusts the reference signal. In order to switch the capacitor from discharging to charging by the circuit, the reference voltage value of the reference signal is switched from the lower limit voltage value to the upper limit voltage value of the triangular wave signal. The reference voltage value of the signal is switched from the upper limit voltage value to the lower limit voltage value, and the reference signal adjustment circuit changes the reference voltage value output to the charge/discharge control circuit when the reference voltage value switching circuit switches the reference voltage value to the upper limit voltage value. The reference signal is adjusted so that the voltage value becomes a first reference voltage value lower than the upper limit voltage value, and when the reference voltage value switching circuit switches the reference voltage value to the lower limit voltage value, the charge/discharge control circuit The reference signal is adjusted so that the output reference voltage value becomes a second reference voltage value higher than the lower limit voltage value and lower than the first reference voltage value.
According to the present invention, by adjusting the reference voltage value of the reference signal by the reference signal adjustment circuit, charging is performed before the triangular wave signal reaches the upper limit voltage value and the lower limit voltage value in consideration of the delay time of the charge/discharge control circuit. By switching the discharge control, it is possible to suppress the occurrence of overshoot.
Thus, according to the present invention, even when the frequency of the triangular wave signal is high, it is possible to generate a triangular wave signal with an appropriate waveform in which overshoot is suppressed.

1 is a circuit diagram showing an example of an oscillator circuit according to a first embodiment; FIG. 4 is an operation waveform diagram of the oscillation circuit according to the first embodiment; FIG. FIG. 4 is an operation waveform diagram of an oscillation circuit according to a comparative example; FIG. 5 is a circuit diagram showing an example of an oscillator circuit according to a second embodiment; FIG. 11 is a circuit diagram showing an example of an oscillator circuit according to a third embodiment; FIG. 11 is a circuit diagram showing an example of an oscillator circuit according to a fourth embodiment; FIG. 11 is a circuit diagram showing an example of an oscillator circuit according to a fifth embodiment;

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. This embodiment does not limit the present invention.

(First embodiment)
First, the oscillator circuit and its control method according to the first embodiment will be described. FIG. 1 is a circuit diagram showing an example of an oscillation circuit 1 according to the first embodiment. FIG. 2 is an operation waveform diagram of the oscillation circuit 1 according to the first embodiment.

The oscillation circuit 1 according to the first embodiment includes a charge/discharge circuit 2, a charge/discharge control circuit 3, a reference voltage value switching circuit 4, and a reference signal adjustment circuit 5, as shown in FIG. The components of these oscillation circuits 1 will be described in detail below.

(Charge/discharge circuit 2)
The charging/discharging circuit 2 is a circuit that controls charging/discharging of the first capacitor C1 with power supplied from the power supply.

The charging/discharging circuit 2 generates a triangular wave signal A according to the charging voltage of the first capacitor C1.

As a specific configuration for generating the triangular wave signal A, the charge/discharge circuit 2 has a first constant current circuit 21 , a transistor Tr, and a second constant current circuit 22 .

The first constant current circuit 21 is connected between the power supply _VDD and one end of the first capacitor C1.

The transistor Tr has one end connected to one end of the first capacitor C1, and a control terminal connected to the output terminal of the comparator 31 of the charge/discharge control circuit 3, which will be described later. The transistor Tr may be an nMOSFET that is turned on by a high-level control signal and turned off by a low-level control signal, as shown in FIG.

The second constant current circuit 22 is connected between the other end of the transistor Tr and a ground potential, which is an example of a fixed potential.

The charging/discharging circuit 2 having such a configuration charges the first capacitor C1 by turning off the transistor Tr in response to a control signal from the output terminal of the comparator 31, which will be described later. On the other hand, the charging/discharging circuit 2 discharges the first capacitor C1 by turning on the transistor Tr according to the control signal from the output terminal of the comparator 31 .

More specifically, when the transistor Tr is turned off, the first constant current circuit 21 outputs a constant current determined by adjusting the resistance value according to the desired frequency to the first capacitor C1. 1. Charge the capacitor C1 with a constant current. On the other hand, when the transistor Tr is turned on, the second constant current circuit 22 supplies a constant current to absorb the accumulated charge of the first capacitor C1 and the constant current of the first constant current circuit 21, and the first capacitor C1 is turned on. Discharge with constant current.

Then, the charging/discharging circuit 2 supplies a triangular wave signal corresponding to the charging voltage of the first capacitor C1 to the non-inverting input terminal of the comparator 31, which will be described later, from the node N between the first constant current circuit 21 and the transistor Tr. Output A.

(Charge/discharge control circuit 3)
The charge/discharge control circuit 3 is a circuit that controls the charge/discharge circuit 2 . The charging/discharging control circuit 3 receives the triangular wave signal A output from the charging/discharging circuit 2 and the reference signal B output from the reference voltage value switching circuit 4, which will be described later. The reference signal B is, for example, a triangular wave signal whose amplitude is smaller than that of the triangular wave signal A, as shown in FIG.

The charge/discharge control circuit 3 compares the voltage value of the triangular wave signal A and the reference voltage value of the reference signal B, and controls the charge/discharge circuit 2 to switch between charging and discharging of the first capacitor C1 according to the comparison result. do.

As a specific configuration for controlling the charge/discharge circuit 2, the charge/discharge control circuit 3 includes a comparator 31 as shown in FIG. The comparator 31 has a non-inverting input terminal (+) which is an example of a first input terminal, an inverting input terminal (-) which is an example of a second input terminal, and an output terminal.

A triangular wave signal A is input from the charging/discharging circuit 2 to the non-inverting input terminal. A reference signal B is input to the inverting input terminal from a reference voltage value switching circuit 4, which will be described later. A control signal for controlling charging/discharging of the first capacitor C<b>1 by the charging/discharging circuit 2 is output from the output terminal to the control terminal of the transistor Tr of the charging/discharging circuit 2 .

In the charge/discharge control circuit 3 having such a configuration, the voltage value of the triangular wave signal A rises to the first reference voltage value Vr1 during the charging of the first capacitor C1, which is the period in which the triangular wave signal A rises (increases) in FIG. When the voltage value of the triangular wave signal A reaches from the first reference voltage value Vr1 to the upper limit voltage value VC1H, the response time (that is, the delay time) of the comparator 31 is applied to charge the first capacitor C1 to The charge/discharge circuit 2 is controlled to switch to discharge.

On the other hand, when the voltage value of the triangular wave signal A reaches the second reference voltage value Vr2 during the discharge of the first capacitor C1, which is the period in which the triangular wave signal A descends (decreases) in FIG. Then, the charging/discharging circuit 2 is controlled to switch from discharging to charging the first capacitor C1.

More specifically, while the first capacitor C1 is being charged, the comparator 31 changes the voltage value of the triangular wave signal A input to the non-inverting input terminal to the first reference voltage of the reference signal B input to the inverting input terminal. When the voltage reaches the value Vr1, a high-level control signal is output from the output terminal to the control terminal of the transistor Tr of the charging/discharging circuit 2 to instruct discharging of the first capacitor C1. That is, the comparator 31 outputs a high-level control signal from the output terminal when switching from charging to discharging the first capacitor C1. The transistor Tr is turned on by a high-level control signal to discharge the first capacitor C1.

At this time, the voltage value of the triangular wave signal A input to the non-inverting input terminal of the comparator 31 reaches the first reference voltage value Vr1 until the high level control signal is output from the output terminal of the comparator 31. requires the response time (that is, delay time) of the comparator 31 .

The response time of the comparator 31 corresponds to the time required for the voltage value of the triangular wave signal A to reach the upper limit voltage value VC1H from the first reference voltage value Vr1. In other words, the first reference voltage value Vr1 is adjusted so that the triangular wave signal A reaches the upper limit voltage value VC1H when the response time of the comparator 31 elapses after the triangular wave signal A reaches this voltage value Vr1. voltage.

By comparing the first reference voltage value Vr1 adjusted in this way with the triangular wave signal A in the comparator 31, the triangular wave signal A becomes larger than the upper limit voltage value VC1H when the first capacitor C1 is switched from charging to discharging. can be suppressed.

On the other hand, while the first capacitor C1 is being charged, the voltage value of the triangular wave signal A input to the non-inverting input terminal of the comparator 31 reaches the first reference voltage value Vr1 of the reference signal B input to the inverting input terminal. If not, a low-level control signal instructing charging of the first capacitor C1 is continuously output from the output terminal to the control terminal of the transistor Tr. The transistor Tr keeps charging the first capacitor C1 by keeping it turned off by the low-level control signal.

The voltage value of the triangular wave signal A input to the non-inverting input terminal of the comparator 31 reaches the second reference voltage value Vr2 of the reference signal B input to the inverting input terminal while the first capacitor C1 is being discharged. In this case, a low-level control signal instructing charging of the first capacitor C1 is output from the output terminal to the control terminal of the transistor Tr of the charging/discharging circuit 2 . That is, the comparator 31 outputs a low-level control signal from the output terminal when switching from discharging to charging the first capacitor C1. The transistor Tr is turned off by a low-level control signal to charge the first capacitor C1.

At this time, the voltage value of the triangular wave signal A input to the non-inverting input terminal of the comparator 31 reaches the second reference voltage value Vr2 until the low level control signal is output from the output terminal of the comparator 31. requires the response time of the comparator 31 .

The response time of the comparator 31 corresponds to the time required for the voltage value of the triangular wave signal A to reach the lower limit voltage value VC1L from the second reference voltage value Vr2. In other words, the second reference voltage value Vr2 is adjusted so that the triangular wave signal A reaches the lower limit voltage value VC1L when the response time of the comparator 31 elapses after the triangular wave signal A reaches this voltage value Vr2. voltage.

By comparing the second reference voltage value Vr2 adjusted in this way with the triangular wave signal A in the comparator 31, when the first capacitor C1 is switched from discharging to charging, the triangular wave signal A becomes smaller than the lower limit voltage value VC1L. can be suppressed.

On the other hand, the voltage value of the triangular wave signal A input to the non-inverting input terminal of the comparator 31 reaches the second reference voltage value Vr2 of the reference signal B input to the inverting input terminal while the first capacitor C1 is being discharged. If not, a high-level control signal instructing discharge of the first capacitor C1 is continuously output from the output terminal to the control terminal of the transistor Tr. The transistor Tr continues to discharge the first capacitor C1 by being kept on by the high-level control signal.

By outputting the control signal from the output terminal of the comparator 31 to the control terminal of the transistor Tr of the charging/discharging circuit 2 in this manner, the charging/discharging of the first capacitor C1 by the charging/discharging circuit 2 is controlled.

(Reference voltage value switching circuit 4)
The reference voltage value switching circuit 4 is a circuit that generates a reference signal B, outputs it to the charge/discharge control circuit 3, and switches the reference voltage value of the reference signal B. FIG.

The reference voltage value switching circuit 4 switches the reference voltage value of the reference signal B from the lower limit voltage value VC1L of the triangular wave signal A to the upper limit voltage value VC1H in order to switch the first capacitor C1 from discharging to charging by the charge/discharge control circuit 3. .

On the other hand, the reference voltage value switching circuit 4 switches the reference voltage value of the reference signal B from the upper limit voltage value VC1H to the lower limit voltage value VC1L in order to switch the charge/discharge control circuit 3 from charging the first capacitor C1 to discharging it.

As a specific configuration for generating and switching the reference signal B, the reference voltage value switching circuit 4, as shown in FIG. and an inverter 41 . The resistor R2 is an example of a first resistor. The resistor R3 is an example of a second resistor. The switch SW has a first transfer gate TG1, which is an example of a first switching element, and a second transfer gate TG2, which is an example of a second switching element.

The resistors R1 to R3 are connected in series between the power supply _VDD and the ground potential, which is an example of a fixed potential. More specifically, the resistor R1 has one end connected to the power supply _VDD and the other end connected to one end of the resistor R2. The other end of the resistor R2 is connected to one end of the resistor R3. The other end of resistor R3 is connected to the ground potential.

The switch SW connects the contacts of the inverting input terminal of the comparator 31 with respect to the first to third resistors R1 to R3 to the first node N1 (first contact) between the resistors R1 and R2 and the resistors R2 and R3. and the second node N2 (second contact) between.

The first node N1 is a contact of a switch SW for dividing the power supply voltage (hereinafter denoted by the same symbol _VDD as the power supply) to the upper limit voltage VC1H of the triangular wave signal A. FIG. The second node N2 is a contact of a switch SW for dividing the power supply voltage _VDD to the lower limit voltage VC1L of the triangular wave signal A. FIG.

The first transfer gate TG1 of the switch SW has one end connected to one end of the second capacitor C2 of the reference signal adjustment circuit 5 described later, the other end connected to the first node N1, and a control terminal connected to the output terminal side of the comparator 31. It is connected to the.

The second transfer gate TG2 of the switch SW has one end connected to one end of the second capacitor C2, the other end connected to the second node N2, and a control terminal connected to the output terminal side of the comparator 31. FIG.

The inverter 41 has one end connected to the output terminal of the comparator 31 and the other end connected to the control terminal of the first transfer gate TG1 and the control terminal of the second transfer gate TG2.

When the control signal output from the output terminal of the comparator 31 instructs charging of the first capacitor C1 (that is, when the control signal is at a low level), the switch SW switches the inverting input terminal of the comparator 31 to the first Connect to node N1. By connecting the inverting input terminal of the comparator 31 to the first node N1, the switch SW switches the reference voltage value of the reference signal B from the lower limit voltage value VC1L of the triangular wave signal A to the upper limit voltage value VC1H.

On the other hand, when the control signal output from the output terminal of the comparator 31 instructs to discharge the first capacitor C1 (that is, when the control signal is at a high level), the switch SW switches the inverting input terminal of the comparator 31 to It connects to the second node N2. By connecting the inverting input terminal of the comparator 31 to the second node N2, the switch SW switches the reference voltage value of the reference signal B from the upper limit voltage value VC1H to the lower limit voltage value VC1L.

More specifically, the first transfer gate TG1 outputs a low-level control signal when the control signal output from the output terminal of the comparator 31 is a low-level control signal instructing charging of the first capacitor C1. It is turned on by the first inverted signal logically inverted by the inverter 41 . By being turned on by the first inversion signal, the first transfer gate TG1 connects the inversion input terminal of the comparator 31 to the first node N1, and increases the reference voltage value of the reference signal B from the lower limit voltage value VC1L of the triangular wave signal A to the upper limit. Switch to voltage value VC1H.

On the other hand, when the control signal output from the output terminal of the comparator 31 is a high level control signal instructing discharge of the first capacitor C1, the first transfer gate TG1 outputs a high level control signal to the inverter 41. It is turned off by the inverted second inverted signal. By being turned off by the second inverted signal, the first transfer gate TG1 disconnects the inverted input terminal of the comparator 31 from the first node N1.

When the control signal output from the output terminal of the comparator 31 is a low-level control signal instructing charging of the first capacitor C1, the second transfer gate TG2 outputs a low-level control signal through the inverter 41. It is turned off by the inverted first inversion signal. By being turned off by the first inverted signal, the second transfer gate TG2 disconnects the inverted input terminal of the comparator 31 from the second node N2.

On the other hand, when the control signal output from the output terminal of the comparator 31 is a high-level control signal instructing the discharge of the first capacitor C1, the second transfer gate TG2 outputs a high-level control signal through the inverter 41. It is turned on by the inverted second inverted signal. By being turned on by the second inverted signal, the second transfer gate TG2 connects the inverted input terminal of the comparator 31 to the second node N2, and changes the reference voltage value of the reference signal B from the upper limit voltage value VC1H of the triangular wave signal A to the lower limit. Switch to the voltage value VC1L.

(Reference signal adjustment circuit 5)
The reference signal adjustment circuit 5 is a circuit that adjusts the reference signal B. FIG.

The reference signal adjustment circuit 5 adjusts the reference voltage output to the charge/discharge control circuit 3 when the reference voltage value switching circuit 4 switches the reference voltage value to the upper limit voltage value VC1H in order to switch from discharging to charging the first capacitor C1. The reference signal B is adjusted so that the voltage value becomes a first reference voltage value Vr1 lower than the upper limit voltage value VC1H.

That is, the reference signal adjustment circuit 5 adjusts the reference voltage value output to the charge/discharge control circuit 3 to the first reference voltage value Vr1 when the inverting input terminal of the comparator 31 is connected to the first node N1. Adjust the reference signal B.

On the other hand, the reference signal adjustment circuit 5 outputs to the charge/discharge control circuit 3 when the reference voltage value switching circuit 4 switches the reference voltage value to the lower limit voltage value VC1L in order to switch from charging to discharging the first capacitor C1. The reference signal B is adjusted so that the reference voltage value is a second reference voltage value Vr2 higher than the lower limit voltage value VC1L and lower than the first reference voltage value Vr1.

That is, the reference signal adjustment circuit 5 adjusts the reference voltage value output to the charge/discharge control circuit 3 to the second reference voltage value Vr2 when the inverting input terminal of the comparator 31 is connected to the second node N2. Adjust the reference signal B.

The reference signal adjustment circuit 5 may adjust the reference signal B so that the higher the frequency of the triangular wave signal A, the smaller the first reference voltage value Vr1 and the larger the second reference voltage value Vr2.

More specifically, the reference signal adjustment circuit 5 operates during the period in which the reference voltage value of the reference signal B is maintained at the upper limit voltage value VC1H by the reference voltage value switching circuit 4, as indicated by the dashed rectangular waveform in FIG. At T1, the reference signal B (solid line waveform) is adjusted so that the reference voltage value output to the charge/discharge control circuit 3 increases from the second reference voltage value Vr2 to the first reference voltage value Vr1. The reference signal adjustment circuit 5 may adjust the reference signal B so that the reference voltage value increases from the second reference voltage value to the first reference voltage value according to a linear function.

On the other hand, in the period T2 in which the reference voltage value is maintained at the lower limit voltage value VC1L by the reference voltage value switching circuit 4, the reference signal adjustment circuit 5 changes the reference voltage value output to the charge/discharge control circuit 3 to the first reference voltage value. The reference signal B is adjusted to decrease from the value Vr1 to the second reference voltage value Vr2. The reference signal adjustment circuit 5 may adjust the reference signal B so that the reference voltage value decreases from the first reference voltage value Vr1 to the second reference voltage value Vr2 according to a linear function.

As a specific configuration example for adjusting the reference signal B, the reference signal adjustment circuit 5 has a second capacitor C2. The second capacitor C2 has one end connected to the switch SW and the inverting input terminal of the comparator 31, and the other end connected to a ground potential, which is an example of a fixed potential.

The second capacitor C2 connects the first node N1 and the second node N2 among the first to third resistors R1 to R3 when the inverting input terminal of the comparator 31 is connected to the first node N1 by the switch SW. and a resistor R3 between the second node N2 and the ground potential.

By being connected to the resistor R2 and the resistor R3, the second capacitor C2 provides the reference voltage output to the charge/discharge control circuit 3 when the reference voltage value switching circuit 4 switches the reference voltage value to the upper limit voltage value VC1H. The reference signal B is adjusted so that the value becomes a first reference voltage value Vr1 lower than the upper limit voltage value VC1H. More specifically, the comparator 31 is inverted when the reference voltage value switching circuit 4 switches the reference voltage value to the upper limit voltage value VC1H due to the time constant of the circuit composed of the second capacitor C2, the resistor R2, and the resistor R3. The reference voltage value output to the input terminal is adjusted to the first reference voltage value Vr1.

On the other hand, the second capacitor C2 is connected to the resistor R3 when the switch SW connects the inverting input terminal of the comparator 31 to the second node N2.

By being connected to the resistor R3, the second capacitor C2 allows the reference voltage value output to the charge/discharge control circuit 3 to be the lower limit when the reference voltage value switching circuit 4 switches the reference voltage value to the lower limit voltage value VC1L. The reference signal B is adjusted to a second reference voltage value Vr2 higher than the voltage value VC1L and lower than the first reference voltage value Vr1. More specifically, when the reference voltage value switching circuit 4 switches the reference voltage value to the lower limit voltage value VC1L due to the time constant of the circuit composed of the second capacitor C2 and the resistor R3, the inverting input terminal of the comparator 31 The output reference voltage value is adjusted to the second reference voltage value Vr2.

Here, if the upper limit voltage value VC1H of the triangular wave signal A set by the reference voltage value switching circuit 4 is directly output to the inverting input terminal of the comparator 31 when switching from discharging to charging the first capacitor C1, When the triangular wave signal A input to the non-inverting input terminal reaches the upper limit voltage value VC1H after the start of charging, the comparator 31 outputs a low-level control signal instructing charging to instruct discharging. Switch to high-level control signal output. However, switching the output of this control signal requires a response time (that is, a delay time) of the comparator 31 . Since the response time is required, as shown in FIG. 3, even after the triangular wave signal A reaches the upper limit voltage value VC1H, the first capacitor C1 continues to be charged by continuing to output the low-level control signal. As a result, an overshoot occurs in which the triangular wave signal A becomes larger than the upper limit voltage value VC1H.

On the other hand, according to the reference signal adjustment circuit 5, when the first capacitor C1 is switched from discharging to charging, the first voltage lower than the upper limit voltage value VC1H of the triangular wave signal A set by the reference voltage value switching circuit 4 is set. A reference voltage value Vr1 can be output to the inverting input terminal of the comparator 31 . When the triangular wave signal A input to the non-inverting input terminal reaches the first reference voltage value Vr1 after the start of charging, the comparator 31 outputs a low-level control signal instructing charging to Switch to the output of a high-level control signal that instructs discharge. The switching of the control signal requires a response time (that is, a delay time) of the comparator 31 . By requiring a response time, as shown in FIG. 2, the first capacitor C1 continues to be charged even after the triangular wave signal A reaches the first reference voltage value Vr1.

However, when the triangular wave signal A reaches the upper limit voltage value VC1H, the response time of the comparator 31 elapses, so that the comparator 31 can output a high-level control signal and switch to discharge the first capacitor C1. can be done. As a result, it is possible to suppress an overshoot in which the triangular wave signal A becomes larger than the upper limit voltage value VC1H.

Further, if the lower limit voltage value VC1L of the triangular wave signal A set by the reference voltage value switching circuit 4 is directly output to the inverting input terminal of the comparator 31 when switching from charging to discharging the first capacitor C1, the comparator 31 is triggered by the fact that the triangular wave signal A input to the non-inverting input terminal reaches the lower limit voltage value VC1L after the start of discharging, and the output of a high level control signal instructing discharging is changed to a low level instructing charging. Switch to level control signal output. However, switching the output of this control signal requires a response time (that is, a delay time) of the comparator 31 . Since the response time is required, as shown in FIG. 3, even after the triangular wave signal A reaches the lower limit voltage value VC1L, the first capacitor C1 continues to be discharged by continuing to output the high-level control signal. As a result, an overshoot occurs in which the triangular wave signal A becomes smaller than the lower limit voltage value VC1L.

On the other hand, according to the reference signal adjustment circuit 5, when switching from charging to discharging of the first capacitor C1, the second voltage higher than the lower limit voltage value VC1L of the triangular wave signal A set by the reference voltage value switching circuit 4 is set. A reference voltage value Vr2 can be output to the inverting input terminal of the comparator 31 . After the discharge is started, the comparator 31 is triggered by the fact that the triangular wave signal A input to the non-inverting input terminal reaches the second reference voltage value Vr2, and from the output of the high-level control signal instructing the discharge, Switch to the output of a low-level control signal instructing charging. The switching of the control signal requires a response time (that is, a delay time) of the comparator 31 . By requiring a response time, as shown in FIG. 2, the first capacitor C1 continues to be discharged even after the triangular wave signal A reaches the second reference voltage value Vr2.

However, when the triangular wave signal A reaches the lower limit voltage value VC1L, the response time of the comparator 31 elapses, so that the comparator 31 can output a low-level control signal and switch to charging the first capacitor C1. can be done. As a result, it is possible to suppress an overshoot in which the triangular wave signal A becomes smaller than the lower limit voltage value VC1L.

As described above, according to the reference signal adjustment circuit 5, when switching from discharging to charging the first capacitor C1, the first reference voltage value Vr1 lower than the upper limit voltage value VC1H of the triangular wave signal A can be set in the comparator 31. , the overshoot on the upper limit side of the triangular wave signal A can be suppressed. Further, according to the reference signal adjustment circuit 5, when switching from charging to discharging of the first capacitor C1, by setting the second reference voltage value Vr2 higher than the lower limit voltage value VC1L of the triangular wave signal A to the comparator 31, the triangular wave Overshoot on the lower limit side of signal A can be suppressed.

Next, the operation brought about by the oscillation circuit 1 according to the first embodiment configured as described above will be described.

As described above, the oscillation circuit 1 according to the first embodiment includes the charging/discharging circuit 2, the charging/discharging control circuit 3, the reference voltage switching circuit 4, and the reference signal adjusting circuit 5. The charging/discharging circuit 2 controls charging/discharging of the first capacitor C1 with power supplied from the power source, and generates a triangular wave signal A according to the charging voltage of the first capacitor C1. The charge/discharge control circuit 3 receives the triangular wave signal A and the reference signal B, compares the voltage value of the triangular wave signal A and the reference voltage value of the reference signal B, and charges the first capacitor C1 according to the comparison result. The charging/discharging circuit 2 is controlled to switch between discharging and discharging. The reference voltage value switching circuit 4 generates a reference signal B, outputs it to the charge/discharge control circuit 3, and switches the reference voltage value of the reference signal B. FIG. The reference signal adjustment circuit 5 adjusts the reference signal B. FIG. The reference voltage value switching circuit 4 switches the reference voltage value of the reference signal B from the lower limit voltage value VC1L of the triangular wave signal A to the upper limit voltage value VC1H in order to switch from discharging to charging the first capacitor C1 by the charge/discharge control circuit 3. On the other hand, in order to switch from charging of the first capacitor C1 to discharging by the charge/discharge control circuit 3, the reference voltage value of the reference signal B is switched from the upper limit voltage value VC1H to the lower limit voltage value VC1L.

When the reference voltage value switching circuit 4 switches the reference voltage value to the upper limit voltage value VC1H, the reference signal adjustment circuit 5 outputs a reference voltage value lower than the upper limit voltage value VC1H to the charge/discharge control circuit 3. The reference signal B is adjusted so as to become the first reference voltage value Vr1. On the other hand, in the reference signal adjustment circuit 5, when the reference voltage value switching circuit 4 switches the reference voltage value to the lower limit voltage value VC1L, the reference voltage value output to the charge/discharge control circuit 3 is higher than the lower limit voltage value VC1L. The reference signal B is adjusted to have a second reference voltage value Vr2 lower than the first reference voltage value Vr1.

According to such a configuration, by adjusting the reference voltage value of the reference signal B by the reference signal adjustment circuit 5, the triangular wave signal A is adjusted to the upper limit voltage value VC1H and the lower limit voltage value VC1H in consideration of the delay time of the charge/discharge control circuit 3. By switching the charge/discharge control before reaching the voltage value VC1L, it is possible to suppress the occurrence of overshoot.

Thus, according to the first embodiment, even when the frequency of the triangular wave signal A is high, it is possible to generate a triangular wave signal with an appropriate waveform in which overshoot is suppressed.

Further, as described above, the charge/discharge control circuit 3 causes the voltage value of the triangular wave signal A to increase to the first reference voltage value Vr1 when the voltage value of the triangular wave signal A reaches the first reference voltage value Vr1 while the first capacitor C1 is being charged. The charging/discharging circuit 2 is controlled to switch from charging to discharging the first capacitor C1 over the response time of the charging/discharging control circuit 3 from the reference voltage value Vr1 to the upper limit voltage value VC1H. Further, the charge/discharge control circuit 3 switches the first capacitor C1 from discharging to charging when the voltage value of the triangular wave signal A reaches the second reference voltage value Vr2 during discharging of the first capacitor C1. Controls circuit 2.

According to such a configuration, in consideration of the delay time of the charge/discharge control circuit 3, charging/discharging of the first capacitor C1 is actually switched when the triangular wave signal A reaches the upper limit voltage value VC1H and the lower limit voltage value VC1L. Therefore, it is possible to suppress the occurrence of undershoot due to too early actual switching between charging and discharging.

Further, as described above, the reference signal B is a triangular wave signal with an amplitude smaller than that of the triangular wave signal A. FIG.

According to such a configuration, the simple signal waveform of the reference signal B prevents charging and discharging from switching until the reference signal B reaches the first reference voltage value Vr1 or the second reference voltage value Vr2. can.

Further, as described above, the reference signal adjustment circuit 5 adjusts the reference signal B so that the higher the frequency of the triangular wave signal A, the smaller the first reference voltage value Vr1 and the larger the second reference voltage value Vr2. may be adjusted.

According to such a configuration, regardless of the frequency of the triangular wave signal A, it is possible to generate a triangular wave signal with an appropriate waveform in which overshoot is suppressed by a simple technique.

Further, as described above, the reference signal adjustment circuit 5 outputs the reference voltage value to the charge/discharge control circuit 3 during the period in which the reference voltage value switching circuit 4 maintains the reference voltage value at the upper limit voltage value VC1H. increases from the second reference voltage value Vr2 to the first reference voltage value Vr1. Further, the reference signal adjustment circuit 5 changes the reference voltage value output to the charge/discharge control circuit 3 to the first reference voltage value while the reference voltage value is maintained at the lower limit voltage value VC1L by the reference voltage value switching circuit 4. The reference signal B is adjusted to decrease from Vr1 to a second reference voltage value Vr2.

According to such a configuration, after the triangular wave signal A reaches the second reference voltage value Vr2 during discharging of the first reference voltage value Vr1, the reference voltage of the reference voltage value switching circuit 4 is set to the upper limit voltage value VC1H. The reference voltage value of the reference signal B can be increased from the second reference voltage value Vr2 to the first reference voltage value Vr1 by switching and maintaining the upper limit voltage value VC1H. Further, after the triangular wave signal A reaches the first reference voltage value Vr1 during charging of the first reference voltage value Vr1, the reference voltage of the reference voltage value switching circuit 4 is switched to the lower limit voltage value VC1L, over the sustain period, the reference voltage value of the reference signal B can be decreased from the first reference voltage value Vr1 to the second reference voltage value Vr2. As a result, the reference signal adjustment circuit 5 appropriately adjusts the reference signal B between the first reference voltage value Vr1 and the second reference voltage value Vr2 based on the setting state of the reference voltage value by the reference voltage value switching circuit 4. can do.

Further, as described above, the charge/discharge control circuit 3 includes a non-inverting input terminal (first input terminal) for inputting the triangular wave signal A, an inverting input terminal (second input terminal) for inputting the reference signal B, and an output terminal for outputting a control signal for controlling charging/discharging of the first capacitor C1 by the charging/discharging circuit 2.

According to such a configuration, it is possible to control switching between charging and discharging based on comparison between the triangular wave signal A and the reference signal B with a simple configuration.

Further, as described above, the reference voltage value switching circuit 4 includes a plurality of resistors R1 to R3 connected in series between the power source and the ground potential (fixed potential), and an inverting input terminal for the plurality of resistors R1 to R3. (second input terminal) is connected to the first node N1 (first contact) that divides the power supply voltage _VDD into the upper limit voltage value VC1H of the triangular wave signal A, and the power supply voltage _VDD is connected to the lower limit voltage of the triangular wave signal A. a switch SW for switching between a second node N2 (second contact) that divides the voltage to the value VC1L. Then, the reference signal B is adjusted so that the reference voltage value output to the charge/discharge control circuit 3 becomes the first reference voltage value Vr1 when the inverting input terminal of the reference signal adjustment circuit 5 is connected to the first node N1. adjust. Further, the reference signal adjustment circuit 5 adjusts the reference signal B so that the reference voltage value output to the charge/discharge control circuit 3 becomes the second reference voltage value Vr2 when the inverting input terminal is connected to the second node N2. to adjust. The switch SW connects the inverting input terminal to the first node N1 when the control signal output from the output terminal instructs charging of the first capacitor C1, and connects when the control signal instructs discharging of the first capacitor C1. , the inverting input terminal is connected to the second node N2.

According to such a configuration, the reference voltage value can be changed between the first reference voltage value Vr1 and the second reference voltage value Vr2 by simple control for switching the connection of the inverting input terminal to the first node N1 or the second node N2. You can switch between them appropriately.

Further, as described above, the reference signal adjustment circuit 5 has a second capacitor C2 whose one end is connected to the switch SW and the inverting input terminal and whose other end is connected to the ground potential.

With such a configuration, the number of parts of the reference signal adjustment circuit 5 can be minimized.

Further, as described above, the second capacitor C2 is connected to the first node N1 and the second node N2 among the plurality of resistors R1 to R3 when the inverting input terminal is connected to the first node N1 by the switch SW. and a resistor R3 between the second node N2 and the ground potential. Also, the second capacitor C2 is connected to the resistor R3 when the switch SW connects the inverting input terminal to the second node N2.

According to such a configuration, when the inverting input terminal is connected to the first node N1 and the upper limit voltage value VC1H is set in the reference voltage value switching circuit 4, the second capacitor C2, the resistor R2 and the resistor R3 Due to the time constant of the configured circuit, the first reference voltage value Vr1 can be output to the inverting input terminal of the comparator 31 at a timing suitable for switching from charge control that does not cause overshoot to discharge control. . Further, when the inverting input terminal is connected to the second node N2 and the lower limit voltage value VC1L is set in the reference voltage value switching circuit 4, the time constant of the circuit composed of the second capacitor C2 and the resistor R3 causes The second reference voltage value Vr2 can be output to the inverting input terminal of the comparator 31 at a suitable timing for switching from the discharge control that does not cause overshoot to the charge control.

As described above, the switch SW has one end connected to one end of the second capacitor C2, the other end connected to the first node N1, and the control terminal connected to the output terminal side of the comparator 31. a transfer gate TG1 (first switching element) and a second transfer having one end connected to one end of a second capacitor C2, the other end connected to a second node N2, and a control terminal connected to the output terminal side of the comparator 31; and a gate TG2 (second switching element).

With such a configuration, the switch SW can be configured with a simple circuit configuration using the first transfer gate TG1 and the second transfer gate TG2.

As described above, the comparator 31 outputs a high-level control signal from the output terminal when switching from charging to discharging the first capacitor C1, and when switching from discharging to charging the first capacitor C1. , a low-level control signal is output from the output terminal. The reference voltage value switching circuit 4 further includes an inverter 41 having one end connected to the output terminal of the comparator 31 and the other end connected to the control terminal of the first transfer gate TG1 and the control terminal of the second transfer gate TG2. . The first transfer gate TG1 is turned on by a first inverted signal obtained by logically inverting the low level control signal by the inverter 41, and turned off by a second inverted signal obtained by logically inverting the high level control signal by the inverter 41. FIG. The second transfer gate TG2 is turned off by the first inverted signal and turned on by the second inverted signal.

According to such a configuration, the reference voltage value switching circuit 4 can can appropriately switch the reference voltage value.

Further, as described above, the charging/discharging circuit 2 includes a first constant current circuit 21 connected between the power source and one end of the first capacitor C1, and one end connected to one end of the first capacitor C1. It has a transistor Tr whose terminal is connected to the output terminal of the comparator 31, and a second constant current circuit 22 connected between the other end of the transistor Tr and the ground potential.

According to such a configuration, by charging the first capacitor C1 with a constant current, the triangular wave signal A can be increased with an appropriate waveform, and by discharging the first capacitor C1 with a constant current, the triangular wave signal A can be increased to an appropriate level. It can be lowered in waves.

(Second embodiment)
Next, a second embodiment in which the inverter 41 is omitted will be described, focusing on differences from the first embodiment. FIG. 4 is a circuit diagram showing an example of the oscillation circuit 1 according to the second embodiment.

As in the first embodiment, the comparator 31 outputs a high-level control signal from the output terminal when switching from charging to discharging the first capacitor C1, while switching from discharging to charging the first capacitor C1. A low-level control signal is output from the output terminal.

Unlike the first embodiment, the control terminal of the first transfer gate TG1 is directly connected to the output terminal of the comparator 31 without the inverter 41 intervening. The first transfer gate TG1 is turned on by a low level control signal and turned off by a high level control signal.

Also, unlike the first embodiment, the control terminal of the second transfer gate TG2 is directly connected to the output terminal of the comparator 31 without the inverter 41 intervening. The second transfer gate TG2 is turned off by a low level control signal and turned on by a high level control signal.

With such a configuration, the inverter 41 can be omitted, so the number of parts can be reduced.

(Third embodiment)
Next, a third embodiment in which the reference signal adjustment circuit 5 further includes a resistor will be described, focusing on differences from the first embodiment. FIG. 5 is a circuit diagram showing an example of the oscillation circuit 1 according to the third embodiment.

As shown in FIG. 5, the reference signal adjustment circuit 5 in the third embodiment, in addition to the already-described second capacitor C2, directly connects the second capacitor C2 between the second capacitor C2 and the ground potential. with a resistor R connected.

According to the third embodiment, by including the resistor R in addition to the second capacitor C2, the time constant of the reference signal adjustment circuit 5 can be controlled with high accuracy. As a result, even when the frequency of the triangular wave signal A is high, the overshoot can be suppressed more effectively, and a triangular wave signal with a more appropriate waveform can be generated.

(Fourth embodiment)
Next, the fourth embodiment will be described, focusing on differences from the first embodiment. FIG. 6 is a circuit diagram showing an example of the oscillation circuit 1 according to the fourth embodiment.

The charging/discharging circuit 2 in the fourth embodiment further includes a transistor Tr2 and an inverter 23 in addition to the configuration of the charging/discharging circuit 2 in the first embodiment, as shown in FIG.

The transistor Tr2 has one end connected to the first constant current circuit 21 and the other end connected to one end of the transistor Tr, that is, the node N. As shown in FIG. The transistor Tr2 may be a pMOSFET that is turned on by a low level control signal and turned off by a high level control signal.

The inverter 23 has one end connected to the output end of the comparator 31 and the other end connected to the control terminal of the transistor Tr2.

Further, the reference voltage value switching circuit 4 in the fourth embodiment includes constant voltage sources 42 and 43 instead of the resistors R1 to R3 in the first embodiment.

Constant voltage source 42 is connected between first transfer gate TG1 and the ground potential, and has an upper limit voltage value VC1H as a constant voltage.

Constant voltage source 43 is connected between second transfer gate TG2 and the ground potential, and has lower limit voltage value VC1L as a constant voltage.

Further, the reference signal adjustment circuit 5 in the fourth embodiment further includes a resistor r in addition to the configuration of the first embodiment.

The resistor r has one end connected to one end of the second capacitor C2 and the other end connected to the first transfer gate TG1 and the second transfer gate TG2.

According to the configuration of the fourth embodiment, since the charge/discharge circuit 2 includes the transistor Tr2, the charge/discharge of the first capacitor C1 can be controlled more appropriately. Further, since the reference voltage value switching circuit 4 has the constant voltage sources 42 and 43, the reference voltage can be easily and appropriately switched between the upper limit voltage value VC1H and the lower limit voltage value VC1L. Further, since the reference signal adjustment circuit 5 includes the resistor r, the time constant of the reference signal adjustment circuit 5 can be controlled with high accuracy.

(Fifth embodiment)
Next, the fifth embodiment will be described, focusing on differences from the first embodiment. FIG. 7 is a circuit diagram showing an example of the oscillator circuit 1 according to the fifth embodiment.

As shown in FIG. 7, the reference signal adjustment circuit 5 in the fifth embodiment further includes resistors r1 and r2 in addition to the configuration of the reference signal adjustment circuit 5 in the first embodiment.

The resistor r1 has one end connected to one end of the second capacitor C2 and the other end connected to the first transfer gate TG1.

The resistor r2 has one end connected to one end of the second capacitor C2 and the other end connected to the second transfer gate TG2.

The configuration of the reference voltage value switching circuit 4 is the same as that of the fourth embodiment.

According to the configuration of the fifth embodiment, since the reference signal adjustment circuit 5 includes the resistors r1 and r2, the time constant of the reference signal adjustment circuit 5 can be controlled with high accuracy.

The embodiment described above is merely an example and does not limit the scope of the invention. Various modifications can be made to the above-described embodiments without departing from the scope of the invention. Modified embodiments are included in the scope of the invention described in the claims and equivalents thereof.

1 oscillation circuit 2 charge/discharge circuit 3 charge/discharge control circuit 4 reference voltage value switching circuit 5 reference signal adjustment circuit

Claims (15)

a charging/discharging circuit that controls charging/discharging of a capacitor with power supplied from a power source and generates a triangular wave signal corresponding to the charged voltage of the capacitor;
The charging/discharging circuit receives the triangular wave signal and the reference signal, compares the voltage value of the triangular wave signal with the reference voltage value of the reference signal, and switches between charging and discharging of the capacitor according to the comparison result. a charge/discharge control circuit for controlling the
a reference voltage value switching circuit that generates the reference signal, outputs it to the charge/discharge control circuit, and switches the reference voltage value of the reference signal;
a reference signal adjustment circuit that adjusts the reference signal,
The reference voltage value switching circuit is
In order to switch the capacitor from discharging to charging by the charge/discharge control circuit, the reference voltage value of the reference signal is switched from a lower limit voltage value to an upper limit voltage value of the triangular wave signal, while the capacitor is controlled by the charge/discharge control circuit. switching the reference voltage value of the reference signal from the upper limit voltage value to the lower limit voltage value to switch from charging to discharging of the
The reference signal adjustment circuit is
When the reference voltage value switching circuit switches the reference voltage value to the upper limit voltage value, the reference voltage value output to the charge/discharge control circuit becomes a first reference voltage value lower than the upper limit voltage value. On the other hand, when the reference voltage value switching circuit switches the reference voltage value to the lower limit voltage value, the reference voltage value output to the charge/discharge control circuit is the lower limit voltage value. and adjusting the reference signal to a second reference voltage value higher than the first reference voltage value and lower than the first reference voltage value. The charge/discharge control circuit is
controlling the charge/discharge circuit to switch from charging to discharging the capacitor when the voltage value of the triangular wave signal reaches the first reference voltage value during charging of the capacitor;
2. The charging/discharging circuit is controlled to switch from discharging to charging the capacitor when the voltage value of the triangular wave signal reaches the second reference voltage value during discharging of the capacitor. The oscillation circuit described in . 2. The oscillator circuit according to claim 1, wherein the reference signal is a triangular wave signal having an amplitude smaller than that of the triangular wave signal. The reference signal adjustment circuit adjusts the reference signal such that the higher the frequency of the triangular wave signal, the smaller the first reference voltage value and the larger the second reference voltage value. Item 2. The oscillation circuit according to item 1. The reference signal adjustment circuit changes the reference voltage value output to the charge/discharge control circuit to the second reference voltage value during a period in which the reference voltage value is maintained at the upper limit voltage value by the reference voltage value switching circuit. to the first reference voltage value, and output to the charge/discharge control circuit during a period in which the reference voltage value is maintained at the lower limit voltage value by the reference voltage value switching circuit 2. The oscillator circuit of claim 1, wherein the reference signal is adjusted such that the reference voltage value applied decreases from the first reference voltage value to the second reference voltage value. The charge/discharge control circuit has a first input terminal for inputting the triangular wave signal, a second input terminal for inputting the reference signal, and outputs a control signal for controlling charging/discharging of the capacitor by the charge/discharge circuit. 2. The oscillator circuit according to claim 1, comprising a comparator having an output terminal for The reference voltage value switching circuit is
a plurality of resistors connected in series between the power supply and a fixed potential;
The contacts of the second input terminal for the plurality of resistors are a first contact that divides the voltage of the power supply to the upper limit voltage of the triangular wave signal, and a second contact that divides the voltage of the power supply to the lower limit voltage of the triangular wave signal. and a switch for switching between
The reference signal adjustment circuit is
adjusting the reference signal so that the reference voltage value output to the charge/discharge control circuit becomes the first reference voltage value when the second input terminal is connected to the first contact;
The reference signal is adjusted so that the reference voltage value output to the charge/discharge control circuit becomes the second reference voltage value when the second input terminal is connected to the second contact. 7. The oscillator circuit according to claim 6, wherein: The switch connects the second input terminal to the first contact when the control signal output from the output terminal instructs charging of the capacitor, and the control signal instructs discharging of the capacitor. 8. The oscillator circuit according to claim 7, wherein said second input terminal is connected to said second contact in a case where said second input terminal is connected to said second contact. 8. The oscillator circuit according to claim 7, wherein said reference signal adjusting circuit has a second capacitor having one end connected to said switch and said second input terminal and the other end connected to a fixed potential. The second capacitor acts as a first resistor between the first contact and the second contact among the plurality of resistors when the second input terminal is connected to the first contact by the switch. and a second resistor between the second contact and the fixed potential, and connected to the second resistor when the switch connects the second input terminal to the second contact. 10. The oscillator circuit according to claim 9. The reference signal adjustment circuit has a second capacitor having one end connected to the switch and the second input terminal and the other end connected to a fixed potential,
The switch is
a first switching element having one end connected to one end of the second capacitor, the other end connected to the first contact, and a control terminal connected to the output terminal side of the comparator;
a second switching element having one end connected to one end of the second capacitor, the other end connected to the second contact, and a control terminal connected to the output terminal side of the comparator. 8. The oscillator circuit according to claim 7. the first input terminal is a non-inverting input terminal;
the second input terminal is an inverting input terminal;
The comparator outputs a high-level control signal from the output terminal when switching from charging to discharging the capacitor, and outputs a low-level control signal from the output terminal when switching from discharging to charging the capacitor. and
The reference voltage value switching circuit further includes an inverter having one end connected to the output terminal of the comparator and the other end connected to a control terminal of the first switching element and a control terminal of the second switching element,
The first switching element is turned on by a first inverted signal obtained by logically inverting the low level control signal by the inverter, and turned off by a second inverted signal obtained by logically inverting the high level control signal by the inverter,
12. The oscillator circuit according to claim 11, wherein said second switching element is turned off by said first inverted signal and turned on by said second inverted signal. the first input terminal is a non-inverting input terminal;
the second input terminal is an inverting input terminal;
The comparator outputs a high-level control signal from the output terminal when switching from charging to discharging the capacitor, and outputs a low-level control signal from the output terminal when switching from discharging to charging the capacitor. and
the first switching element is turned on by the low level control signal and turned off by the high level control signal;
12. The oscillator circuit according to claim 11, wherein said second switching element is turned off by said low level control signal and turned on by said high level control signal. The charge/discharge circuit is
a first constant current circuit connected between the power supply and one end of the capacitor;
a transistor having one end connected to one end of the capacitor and having a control terminal connected to the output terminal of the comparator;
7. The oscillator circuit according to claim 6, further comprising a second constant current circuit connected between the other end of said transistor and a fixed potential. a charging/discharging circuit that controls charging/discharging of a capacitor with power supplied from a power source and generates a triangular wave signal corresponding to the charged voltage of the capacitor;
The charging/discharging circuit receives the triangular wave signal and the reference signal, compares the voltage value of the triangular wave signal with the reference voltage value of the reference signal, and switches between charging and discharging of the capacitor according to the comparison result. a charge/discharge control circuit for controlling the
a reference voltage value switching circuit that generates the reference signal, outputs it to the charge/discharge control circuit, and switches the reference voltage value of the reference signal;
controlling an oscillation circuit comprising a reference signal adjustment circuit that adjusts the reference signal;
The control of the oscillation circuit includes:
The reference voltage value switching circuit
In order to switch the capacitor from discharging to charging by the charge/discharge control circuit, the reference voltage value of the reference signal is switched from a lower limit voltage value to an upper limit voltage value of the triangular wave signal, while the capacitor is controlled by the charge/discharge control circuit. switching the reference voltage value of the reference signal from the upper limit voltage value to the lower limit voltage value to switch from charging to discharging of the
The reference signal adjustment circuit is
When the reference voltage value switching circuit switches the reference voltage value to the upper limit voltage value, the reference voltage value output to the charge/discharge control circuit becomes a first reference voltage value lower than the upper limit voltage value. On the other hand, when the reference voltage value switching circuit switches the reference voltage value to the lower limit voltage value, the reference voltage value output to the charge/discharge control circuit is the lower limit voltage value. adjusting the reference signal to a second reference voltage value higher than the first reference voltage value and lower than the first reference voltage value.

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