JPH06188632A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To provide an oscillation circuit in which the start of oscillation is facilitated and defective start of the oscillation is prevented. CONSTITUTION:The oscillation circuit including an inverting amplifier 10 and a feedback circuit 11 feeding back the output signal of the inverting amplifier 10 to the input is provided with a trigger input means consisting of a P-channel transistor(TR) 12 provided between a power supply VDD and an input side of the inverting amplifier circuit 10 and of a delay circuit 13 conducting the P-channel TR 12 for a prescribed time at application of power. The initial state that the input of the inverting amplifier 10 is set to a high level and an output is set to a low level is formed forcibly for a prescribed time(t) after application of power to the oscillation circuit by the trigger input means and the oscillation is started from the initial state by the oscillation circuit, then the oscillation is easily started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating circuit, and more particularly to improving start-up failure of the oscillating circuit.

[0002]

2. Description of the Related Art Conventionally, various oscillator circuits have been used in various electronic circuits. In these oscillation circuits, an amplifier is used to amplify the oscillation signal, and a crystal oscillator or a ceramic oscillator is often used in the feedback circuit to obtain a stable oscillation frequency.

FIG. 2 shows a conventional oscillator circuit in which an inverter is used as an inverting amplifier and a resistor and a crystal oscillator or a ceramic oscillator are used in a feedback circuit.
In the circuit of FIG. 2, the output of the inverting amplifier 10 is fed back to the input side by the feedback circuit 11 and oscillates while the power supply voltage is applied. In this circuit, a capacitor 14 connecting both ends of the feedback circuit 11 to the ground is used to stabilize the oscillation frequency. An oscillation signal is supplied to the circuit of the next stage via the amplifier 15.

[0004]

The oscillation circuit as described above starts its oscillation operation triggered by fluctuations in current when the power is turned on, resistance noise, or noise voltage of a transistor. However, in recent electronic circuits, noise reduction of substrates, LSIs, etc. has progressed, there is no opportunity to start the oscillation operation, and the oscillation circuit does not start up smoothly, so-called startup failure occurs. There is.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an oscillation circuit capable of facilitating the start of oscillation and preventing a start failure of the oscillation operation.

[0006]

To achieve the above object, the present invention provides an inverting amplifier for inverting and amplifying an input signal,
In an oscillation circuit including a feedback circuit for feeding back the output signal of the inverting amplifier to the input side, it is provided with trigger input means for inputting a square wave pulse that triggers the oscillation operation start of the oscillation circuit to the input side of the inverting amplifier. Characterize.

In the oscillator circuit of the present invention, the above-mentioned trigger input means includes a P-channel transistor whose source side is connected to the power source and whose drain side is connected to the input side of the inverting amplifier, and whose input side is connected to the power source and which outputs A delay circuit connected to the gate of a P-channel transistor, the delay circuit including a delay circuit for a predetermined period of time after power-on.
It is preferable that the rise of the gate voltage of the channel transistor is delayed to make the P-channel transistor conductive.

[0008]

According to the above structure, when the oscillation circuit is started, the trigger input means inputs a square wave pulse, which is a trigger for starting the oscillation operation, that is, a trigger, to the input side of the inverting amplifier. Can be facilitated.

Further, as the trigger input means, a P-channel transistor provided between the power supply and the input side of the inverting amplifier, and a delay circuit for conducting the P-channel transistor for a predetermined time after the power is turned on may be used. Therefore, it is necessary to supply the power supply voltage to the input side of the inverting amplifier via the P-channel transistor and fix it to a high voltage for a predetermined time after the power is turned on, thereby fixing the output side of the inverting amplifier to a low voltage. You can On the other hand, when the P-channel transistor is no longer conductive after a lapse of a predetermined time, the oscillating operation is started from the state where the input side of the inverting amplifier is at a high voltage and the output side is at a low voltage, and this state triggers the start of the oscillating operation. Therefore, the start of oscillation of the oscillation circuit can be facilitated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A shows a circuit diagram of an embodiment of an oscillator circuit according to the present invention. In FIG. 1A, the output signal of the inverting amplifier 10 is fed back to the input side by the feedback circuit 11 including a resistor and a crystal oscillator or a ceramic oscillator, and oscillates.

The drain of the P-channel transistor 12 is connected to the input side of the inverting amplifier 10, and the source of the P-channel transistor 12 is connected to the power supply.
The output side of the delay circuit 13 is connected to the gate of the P-channel transistor 12, and the input side of the delay circuit 13 is connected to the power supply. The delay circuit 13 keeps its output at a low voltage until a predetermined time elapses after power is turned on to the oscillation circuit of the present invention. When the output of the delay circuit 13 is a low voltage, the gate of the P-channel transistor 12 is also a low voltage, so that the P-channel transistor 12 becomes conductive and the input side of the inverting amplifier 10 becomes a high voltage by the power supply voltage VDD. Become. When the output of the delay circuit 13 becomes a high voltage after a predetermined time has passed, P
The channel transistor 12 becomes non-conductive, and the power supply voltage VDD is not supplied to the input side of the inverting amplifier 10. That is, the delay circuit 13 determines the time during which the P-channel transistor 12 is conducting.

As described above, the capacitors 14 connecting both ends of the feedback circuit 11 to the ground are used to stabilize the oscillation frequency, and the oscillation signal generated by this oscillation circuit passes through the amplifier 15. And supplied to the next stage circuit.

Next, the operation of the circuit shown in FIG. 1A will be described.

FIG. 1B is an operation diagram at the time of starting the oscillation operation, and shows a time change of the gate voltage of the P-channel transistor 12 and the voltage of the input side of the inverting amplifier 10.

When the oscillator circuit is powered on and started, P
The power supply voltage VDD is applied to the source of the channel transistor 12 and the input side of the delay circuit 13. However,
As shown in (B), the voltage on the output side of the delay circuit 13, that is, the gate voltage of the P-channel transistor 12 does not rise until a predetermined time t elapses after the power is turned on. Therefore, during this period, the P-channel transistor 12 is in a conductive state, and the voltage of the drain side of the P-channel transistor 12, that is, the input side of the inverting amplifier 10 is maintained at a high voltage by the power supply voltage VDD.
As a result, the output side of the inverting amplifier 10 is forcibly maintained at a low voltage, and the initial state in which the input side of the inverting amplifier 10 is high voltage and the output side is low voltage is determined. Incidentally, this predetermined time t
May be, for example, about several μs.

When a predetermined time t elapses after the power is turned on, the voltage on the output side of the delay circuit 13 becomes a high voltage, as shown in FIG.
As shown in (B), P-channel transistor 1
The gate voltage of 2 becomes a high voltage and the P-channel transistor 12 becomes non-conductive. Therefore, the inverting amplifier 1
The power supply voltage VDD is not supplied to the input side of 0. Then, as shown in FIG. 1B, the voltage on the input side of the inverting amplifier 10 decreases, and when it decreases to a certain point,
The output side of the inverting amplifier 10 is inverted to a high voltage, so that the voltage is fed back to the input side, the input side becomes a high voltage again, and the output side is inverted to a low voltage. Thereafter, this operation is repeated and the oscillation circuit performs the oscillation operation. That is, the oscillating operation of the oscillating circuit is started more easily by using the initial state forcibly determined by the P-channel transistor 12 and the delay circuit 13 as a trigger.

[0018]

As described above, according to the present invention,
At the time of starting the oscillation circuit, the trigger input means inputs a square wave pulse that triggers, that is, triggers the oscillation operation start to the input side of the inverting amplifier, so that the oscillation start of the oscillation circuit can be facilitated.

Further, as the trigger input means of the oscillation circuit of the present invention, a P-channel transistor provided between the power supply and the input side of the inverting amplifier and a delay for making the P-channel transistor conductive for a predetermined time after the power is turned on. It can be configured with a circuit. Therefore, the input side of the inverting amplifier can be fixed at a high voltage for a predetermined time after the power is turned on, so that the output side of the inverting amplifier can be fixed at a low voltage. ,
The output side starts the oscillation operation from the low voltage state, and this state triggers the start of the oscillation operation.
It is possible to facilitate the start of oscillation of the oscillator circuit. As a result, it is possible to provide an oscillation circuit that facilitates the start of oscillation and can prevent a startup failure of the oscillation operation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of an oscillator circuit of the present invention,
(A) is a circuit diagram thereof, and (B) is an operation diagram of this circuit at the start of oscillation.

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

[Explanation of symbols]

 10 Inverting amplifier 11 Feedback circuit 12 P-channel transistor 13 Delay circuit

Claims (2)

[Claims] 1. An oscillating circuit including an inverting amplifier for inverting and amplifying an input signal and a feedback circuit for feeding back an output signal of the inverting amplifier to an input side, wherein a square wave pulse as a trigger for starting an oscillation operation of the oscillating circuit is An oscillating circuit comprising trigger input means for inputting to the input side of the inverting amplifier. 2. The oscillator circuit according to claim 1, wherein the trigger input means has a P-channel transistor having a source side connected to a power supply and a drain side connected to an input side of the inverting amplifier, and an input side being a power supply. A delay circuit having an output side connected to the gate of the P-channel transistor, the delay circuit delaying an increase in the gate voltage of the P-channel transistor for a predetermined time after power is turned on. An oscillation circuit characterized by making a transistor conductive.