JPH08298456A - Frequency control circuit - Google Patents

Abstract

PURPOSE: To obtain the frequency control circuit configured simply at a low cost in which a stable frequency signal is obtained even in the case of momentary interruption of the circuit power supply. CONSTITUTION: When a momentary interruption detection section 5 detects momentary interruption of the circuit power supply, a frequency control backup voltage generating section 6 generates a prescribed frequency control voltage based on a backup power supply 7 provided independently of the circuit power supply. The prescribed frequency control voltage is applied to a voltage controlled oscillator 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency control circuit for controlling a frequency signal generated from a voltage controlled oscillator based on a predetermined frequency control value output from a frequency control section, and more particularly to a frequency control circuit even when the circuit power supply is interrupted The present invention relates to a frequency control circuit capable of obtaining a stable frequency signal.

[0002]

2. Description of the Related Art Conventionally, a circuit shown in FIG. 5 is known as a frequency control circuit of this type. The frequency control circuit shown in FIG. 5 includes a frequency control unit 1, a digital / analog converter unit (D / A converter unit) 2, a reference voltage generation unit 3, and a voltage controlled oscillator 4.

That is, a desired frequency control value is output from the frequency control unit 1, and this frequency control value is converted by the D / A converter unit 2 into a frequency control voltage corresponding to the frequency control value. Here, in the D / A converter unit 2,
The reference voltage generated from the reference voltage generation unit 3 is applied, and the D / A converter unit 2 determines the frequency control value output from the frequency control unit 1 by the reference voltage generated from the reference voltage generation unit 3. To a frequency control voltage within a predetermined range. The frequency control voltage converted by the D / A converter unit 2 is applied to the voltage controlled oscillator 4,
As a result, the voltage controlled oscillator 4 generates a signal having a frequency within the range determined by the reference voltage generated by the reference voltage generator 3 and corresponding to the frequency control value output from the frequency controller 1.

By the way, in the conventional frequency control circuit shown in FIG. 5, the frequency control voltage output from the D / A converter section 2 is also cut off when the circuit power supply is interrupted.
Even if the circuit power supply is restored, the frequency control voltage is not applied to the voltage controlled oscillator 4 until a new frequency control value is set by the frequency control unit 1. As a result, The desired frequency signal cannot be obtained.

There is also a configuration in which the voltage controlled oscillator 4 is driven by a power supply of another system, but in this case, the frequency control voltage output from the D / A converter unit 2 is cut off and generated by the voltage controlled oscillator 4. The frequency of the frequency signal is largely deviated from the desired frequency, and as a result, even if the circuit power supply is restored, it takes time to converge to a state in which the desired frequency signal is generated.

In order to solve this problem, a configuration in which the entire circuit is backed up to cope with a momentary interruption of the circuit power supply has been considered, but with this configuration, a relatively large backup power supply is used. However, there is a problem that a power source of a plurality of voltages must be prepared.

[0007]

As described above, in the conventional frequency control circuit, the frequency control voltage is also cut off when the circuit power supply is momentarily cut off, and even if the circuit power supply is restored, a new frequency control section is used. Until the control value is set, the desired frequency signal cannot be obtained from the voltage-controlled oscillator, and in the configuration in which the voltage-controlled oscillator is driven by the power supply of another system, if the circuit power supply is interrupted, the circuit After the power is restored, there is a problem that it takes time to converge to a state where a desired frequency signal is generated. Also, in a configuration that backs up the entire circuit, a large backup power source is required, There was a problem that a voltage power supply had to be prepared.

Therefore, an object of the present invention is to provide a frequency control circuit which can obtain a stable frequency signal even when the circuit power supply is instantaneously cut off, and which can be constructed easily and at low cost.

[0009]

To achieve the above object, the present invention provides a digital / analog converter for converting a frequency control value output from a frequency controller to a predetermined reference voltage and outputting the frequency control value to the frequency control value. By applying the frequency control voltage converted to the corresponding frequency control voltage to the voltage controlled oscillator, a frequency signal corresponding to the frequency control value within the range determined by the reference voltage is generated from the voltage controlled oscillator. In the frequency control circuit to
A momentary interruption detection means for detecting a momentary interruption of the circuit power supply, a backup power supply provided independently of the circuit power supply circuit, and a backup power supply when the momentary interruption of the circuit power supply is detected by the momentary interruption detection means. Frequency control backup voltage generating means for generating a predetermined frequency control voltage based on the above, and applying the predetermined frequency control voltage to the voltage controlled oscillator.

[0010]

According to the present invention, when the instantaneous interruption of the circuit power supply is detected by the instantaneous interruption detection means, the frequency control backup voltage generation means generates a predetermined frequency control voltage based on the backup power supply provided independently of the circuit power supply. , Applying the predetermined frequency control voltage to a voltage controlled oscillator.

With such a configuration, it is possible to obtain a stable frequency signal even when the circuit power supply is instantaneously cut off, with a simple and low-cost configuration.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a frequency control circuit according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a frequency control circuit according to the present invention. In FIG. 1, the same components as those of the conventional circuit shown in FIG.

In FIG. 1, 1 is a frequency control unit and 2 is a D
A / A converter section, 3 is a reference voltage generation section, 4 is a voltage controlled oscillator, 5 is a momentary interruption detection section, 6 is a frequency control backup voltage generation section, and 7 is a backup power supply.

Here, the frequency controller 1 outputs a frequency control value corresponding to a desired frequency signal. This frequency control value is added to the D / A converter unit 2.

The D / A converter section 2 includes a frequency control section 1
The frequency control value corresponding to the desired frequency signal output from is converted into a frequency control voltage corresponding to the frequency control value. Here, the reference voltage generated from the reference voltage generator 3 is applied to the D / A converter unit 2,
The converter unit 2 converts the frequency control value output from the frequency control unit 1 into a frequency control voltage within a predetermined range determined by the reference voltage generated by the reference voltage generation unit 3. The frequency control voltage converted by the D / A converter unit 2 is applied to the voltage control type oscillator 4 so that the voltage control type oscillator 4 has a range determined by the reference voltage generated from the reference voltage generating unit 3. A signal having a frequency within the frequency control value output from the frequency control unit 1 is generated. The configuration up to this point is the same as the conventional circuit shown in FIG.

By the way, in this embodiment, in addition to the above configuration, an instantaneous interruption detection unit 5 for detecting an instantaneous interruption of a circuit power supply (not shown), a backup power supply 7 provided independently of the circuit power supply, an instantaneous interruption detection unit. A frequency control backup voltage generator that generates a predetermined frequency control voltage using the backup power supply 7 and applies the predetermined frequency control voltage to the voltage controlled oscillator 4 when an instantaneous interruption of the circuit power supply is detected by 6 is provided.

According to such a configuration, even if the circuit power supply is instantaneously interrupted, this is detected by the instantaneous interruption detector 5 and the predetermined frequency control voltage generated by the frequency control backup voltage generator 6 is a voltage controlled oscillator. 4, the voltage controlled oscillator 4 is controlled by a predetermined frequency control voltage output from the frequency control backup voltage generator 6 when the circuit power is restored, so that a desired frequency signal is output promptly. As a result, it becomes possible to obtain a stable frequency signal from the voltage controlled oscillator 4 even when the circuit power supply is interrupted.

FIG. 2 shows a specific structure of the frequency control backup voltage generator 6 shown in FIG. In FIG. 2, this frequency control backup voltage generator 6
Is a transistor 61, resistors 62 to 65, diode 6
It consists of 6.

In this configuration, when the instantaneous interruption detection unit 5 detects the instantaneous interruption of the circuit power supply, the frequency control voltage output from the D / A converter unit 2 is also cut off. The detection output is applied to the base of the transistor 61 via the resistor 62, which causes the transistor 61 to
Is turned on, and the output voltage of the backup power supply 7 is applied to the voltage controlled oscillator 4 via the voltage dividing circuit formed of the transistor 61, the resistors 64 and 65, and the diode 66.

In this state, when the circuit power is restored, the voltage controlled oscillator 4 receives a predetermined control voltage determined by the voltage dividing circuit composed of the resistors 64 and 65 from the diode 6.
Since it is applied via 6, the desired frequency signal can be output quickly, and as a result, it is possible to obtain a stable frequency signal from the voltage controlled oscillator 4 even when the circuit power supply is interrupted. .

FIG. 3 shows another specific structure of the frequency control backup voltage generator 6 shown in FIG. Frequency control backup voltage generator 6 shown in FIG.
Is the frequency control backup voltage generator 6 shown in FIG.
The voltage dividing circuit composed of the resistors 64 and 65 of FIG. 2 is replaced with the Zener diode 67.
It is the same as the frequency control backup voltage generator 6 shown in FIG.

That is, in the configuration shown in FIG. 3, when the instantaneous interruption detection unit 5 detects the instantaneous interruption of the circuit power supply, D /
Although the frequency control voltage output from the A converter unit 2 is also cut off, the detection output of the instantaneous interruption detection unit 5 is applied to the base of the transistor 61 via the resistor 62, and the transistor 61 is turned on to back up. Power supply 7
Is applied to the voltage controlled oscillator 4 via the transistor 61, the Zener diode 67 and the diode 66.

In this state, when the circuit power is restored, a predetermined control voltage determined by the Zener diode 67 is applied to the voltage controlled oscillator 4 through the diode 66, so that the desired voltage is promptly obtained. A frequency signal is output, and as a result, a stable frequency signal can be obtained from the voltage controlled oscillator 4 even when the circuit power supply is instantaneously cut off.

FIG. 4 is a block diagram showing a schematic configuration of another embodiment of the frequency control circuit according to the present invention. In addition,
In FIG. 4, the same components as those of the circuit shown in FIG.

In FIG. 4, 1 is a frequency control unit and 2 is D
/ A converter unit, 3 is a reference voltage generation unit, 4 is a voltage control type oscillator, 5 is an instantaneous interruption detection unit, 6 is a frequency control backup voltage generation unit, 7 is a backup power supply, 11 is a voltage monitoring unit, and 12 is a switch. is there. The embodiment shown in FIG.
In addition to the configuration shown in FIG. 1, a voltage monitoring unit 11 for monitoring the frequency control voltage output from the D / A converter unit 2 and a frequency control voltage output from the D / A converter unit 2 and a frequency control backup voltage generating unit A switch 12 for switching the frequency control backup voltage output from 6 and applying it to the voltage controlled oscillator 4 is provided.
Other configurations are the same as those shown in FIG.

In this configuration, when the circuit power supply is instantaneously interrupted and detected by the instantaneous interruption detector 5, the switch 12 is switched to select the frequency control backup voltage generator 6 side. As a result, the predetermined frequency control voltage generated by the frequency control backup voltage generator 6 is applied to the voltage controlled oscillator 4.

Further, the voltage monitoring unit 11 monitors the frequency control voltage output from the D / A converter unit 2, and the frequency control voltage output from the D / A converter unit 2 is for some reason determined in a predetermined range. If it is out of the range, the switch 12 is switched so as to select the frequency control backup voltage generator 6 side, whereby the predetermined frequency control voltage generated by the frequency control backup voltage generator 6 is changed to the voltage controlled oscillator 4. Apply to.

According to such a configuration, the D /
Even when the frequency control voltage output from the A converter unit 2 deviates from the predetermined range, it becomes possible to obtain a stable frequency signal from the voltage controlled oscillator 4.

[0030]

As described above, according to the present invention, when the instantaneous interruption of the circuit power supply is detected by the instantaneous interruption detection means, the frequency control backup voltage generating means detects the instantaneous interruption of the circuit power supply based on the backup power supply provided independently of the circuit power supply. Since a predetermined frequency control voltage is generated and the predetermined frequency control voltage is applied to the voltage controlled oscillator, it is possible to obtain a stable frequency signal even when the circuit power is interrupted by a simple and low-cost configuration. Has the effect that it becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a frequency control circuit according to the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a frequency control backup voltage generator shown in FIG.

FIG. 3 is a circuit diagram showing another specific configuration of the frequency control backup voltage generator shown in FIG.

FIG. 4 is a block diagram showing a schematic configuration of another embodiment of the frequency control circuit according to the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a conventional frequency control circuit.

[Explanation of symbols]

1 Frequency Control Section 2 Digital / Analog Converter Section (D / A Converter Section) 3 Reference Voltage Generation Section 4 Voltage Controlled Oscillator 5 Instantaneous Interruption Detection Section 6 Frequency Control Backup Voltage Generation Section 7 Backup Power Supply 11 Voltage Monitoring Section 12 Switches

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuhiro Kume 21-3-1, Asahigaoka, Hino City, Tokyo 21 Toshiba Communication Technology Co., Ltd.

Claims (1)

[Claims] 1. A frequency control voltage converted from a frequency control value output from the frequency control section into a frequency control voltage corresponding to the frequency control value by a digital / analog conversion section for converting and outputting the frequency control value into a predetermined reference voltage. In a frequency control circuit that generates a frequency signal corresponding to the frequency control value within a range determined by the reference voltage from the voltage controlled oscillator by applying the voltage control oscillator, A disconnection detection unit, a backup power supply that is provided independently of the circuit power supply circuit, and when a momentary interruption of the circuit power supply is detected by the instantaneous interruption detection unit, a predetermined frequency control voltage is generated based on the backup power supply. Frequency control backup voltage generating means for generating and applying the predetermined frequency control voltage to the voltage controlled oscillator. And a frequency control circuit.