JPH077348A - Dc control signal generating circuit - Google Patents

Abstract

PURPOSE:To obtain a DC control voltage signal stable to the fluctuation of a power supply voltage by DC-converting and outputting a differential portion of a DC-converted pulse signal and the power supply voltage subjected to prescribed voltage division by an operational amplifier circuit having a feedback circuit formed by a capacitor. CONSTITUTION:When a power supply supply voltage is fluctuated, a divided voltage is fluctuated, and also, an output voltage of an operational amplifier 13 is also fluctuated, and moreover, a peak value of a pulse signal of a PWM control input signal from an input terminal 1 is also modulated. An operational amplifier 6 calculates a differential portion of the PWM control input signal converted into DC by a filter circuit 5 and a voltage divided by a voltage dividing circuit, and outputs it as a DC control voltage signal. Therefore, the pulse signal converted to DC at the time when the power supply voltage is fluctuated, and a fluctuation of the differential portion divided by a prescribed voltage dividing ratio are offset. This fluctuation portion does not appear in the output of the operational amplifier 6, and the fluctuation of the DC control voltage signal caused by the fluctuation of the power supply voltage is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC control signal generation circuit capable of suppressing the influence of fluctuations in power supply voltage.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a configuration of a conventional DC control signal generating circuit. First, the structure will be described.
Is an input terminal to which a pulse signal whose pulse width is modulated (hereinafter referred to as a PWM control input signal) is supplied, 2 and 3 are resistors connected in series, 4 is a connection point between the resistors 2 and 3 and the ground. It is a connected capacitor. The resistor 2, the resistor 3, and the capacitor 4 constitute a filter circuit 5 that converts a pulse-width-modulated pulse signal into a direct current.
An operational amplifier 6 has a resistor 7 and a capacitor 8 connected in parallel between the output terminal and the inverting terminal. Reference numeral 9 is an offset compensation resistor connected between the non-inverting terminal of the operational amplifier 6 and the ground, and 10 is a DC control voltage output terminal for outputting a DC control voltage signal.

Next, the operation will be described. The PWM control input signal supplied to the input terminal 1 is smoothed by the filter circuit 5 and converted into a DC voltage signal. This DC voltage signal is supplied to the inverting terminal of the operational amplifier 6. The operational amplifier 6 constitutes a low-pass filter circuit that is fed back by a capacitor 8 and a resistor 7, and outputs a DC control voltage signal according to the pulse width of the PWM control input signal.

[0004]

Since the conventional DC control signal generating circuit is constructed as described above, when the power supply voltage changes, the pulse crest value of the PWM control input signal also changes, resulting in a filter. As a result of the output voltage of the circuit 5 also changing, and the power supply voltage of the operational amplifier 6 also changing,
The level of the DC control voltage signal output from the output terminal will also change. For this reason, when the DC control voltage signal is supplied to the laser auto power control circuit or the like, and the output of the laser oscillator is made constant to write on the magneto-optical disk, the operation of the auto power control circuit becomes unstable, There were problems such as the error rate getting worse.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a DC control signal generation circuit capable of generating a DC control voltage signal which is stable with respect to fluctuations in power supply voltage. To aim.

[0006]

A DC control signal generating circuit according to the present invention supplies a first input terminal to which a pulse signal is DC-converted and supplied, and a power supply voltage divided by a predetermined voltage dividing ratio. It is characterized in that it is composed of an operational amplifier circuit having a second input terminal and a feedback circuit by a capacitor.

[0007]

In the DC control signal generating circuit according to the present invention, the differential component of the pulse signal DC-converted by the operational amplifier circuit having the feedback circuit by the capacitor and the power supply voltage divided by the predetermined voltage dividing ratio is DC-converted. Is output after being output,
Even if the power supply voltage fluctuates, fluctuations in the differential component, which is the relative amount of the DC-converted pulse signal and the power supply voltage divided by a predetermined voltage dividing ratio, are canceled out, and the output signal level of the operational amplifier circuit is Fluctuation is suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of the DC control signal generation circuit of this embodiment. In FIG. 1, parts that are the same as or correspond to those in FIG. 2 are assigned the same reference numerals and explanations thereof are omitted.

In FIG. 1, 11 and 12 are power supply lines V.
It is a resistor connected in series between L and the ground, and constitutes a voltage dividing circuit for dividing the power supply voltage. Reference numeral 13 denotes an operational amplifier, which constitutes a known voltage follower circuit in which an output terminal and an inverting terminal are connected. 14 is an operational amplifier 13
Is a resistor connected between the output terminal of the operational amplifier 6 and the non-inverting terminal of the operational amplifier 6. Reference numeral 15 is an operational amplifier circuit having a differential amplification function for calculating a differential component of the voltage signal supplied to the inverting terminal and the non-inverting terminal of the operational amplifier 6.

Next, the operation will be described. When the PWM control input signal is supplied to the input terminal 1, the PWM control input signal is converted by the filter circuit 5 into a signal converted into a direct current having a level according to the pulse width, and supplied to the inverting terminal of the operational amplifier 6. On the other hand, the power supply voltage of the power supply voltage line VL is divided by a voltage dividing circuit composed of a resistor 11 and a resistor 12 connected in series, and supplied to the non-inverting terminal of the operational amplifier 13. Since the operational amplifier 13 constitutes a voltage follower circuit, the power supply voltage supplied to the non-inverting terminal of the operational amplifier 13 is divided by the resistors 11 and 12 and supplied from the output terminal of the operational amplifier 13 to the non-inverting terminal of the operational amplifier 6. It

In the operational amplifier 6, the DC signal supplied from the filter circuit 5 to the inverting terminal and the operational amplifier 1
The output of FIG. 3, that is, the differential component of the power supply voltage divided by the voltage dividing circuit including the resistors 11 and 12 is calculated by the operational amplifier 6 fed back by the capacitor 8 forming the low-pass filter circuit, and the DC control voltage is obtained. The signal is supplied to the DC control voltage output terminal 10 as a signal.

When the power supply voltage fluctuates, the divided voltage also fluctuates, the output voltage of the operational amplifier 13 fluctuates, and the peak value of the pulse signal of the PWM control input signal also fluctuates. Since the operational amplifier 6 calculates a differential component between the PWM control input signal converted into the direct current by the filter circuit 5 and the voltage divided by the voltage dividing circuit and outputs it as a DC control voltage signal, when the power supply voltage fluctuates. The fluctuations of the two are canceled out, and this fluctuation does not appear in the output of the operational amplifier 6, and the DC due to the fluctuation of the power supply voltage.
Fluctuations in the control voltage signal will be suppressed.

[0013]

As described above, according to the present invention, it is possible to suppress the fluctuation of the DC control voltage signal which is the output of the operational amplifier circuit due to the fluctuation of the power supply voltage.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a DC control signal generation circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional DC control signal generation circuit.

[Explanation of symbols]

 8 capacitors 15 operational amplifier circuit

Claims (1)

[Claims] 1. A first input terminal to which a pulse signal is converted into a direct current and supplied, a second input terminal to which a power supply voltage divided by a predetermined voltage dividing ratio is supplied, and a feedback circuit using a capacitor. A DC control signal generation circuit comprising an operational amplifier circuit having the same.