JPH04252388A - Pwm wave integration circuit - Google Patents

Abstract

PURPOSE:To set a PWM wave pulse width integration voltage output characteristic to a-more-than-tertiary curve characteristic. CONSTITUTION:The integration voltage is generated by charging/discharging a capacitor 1 in charging resistor R1 and discharging registor R2 by the PWM wave in an input terminal 3. In the integration circuit switching charge time constant and discharge time constant in a diode D1, R4 and the serial circuit of a Zener diode are inserted to the discharge resistance R2 in parallel and the discharge time constant voltage is changed based on the output integration voltage. Fore example, a tertiary curve can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrating circuit for pulse width modulated waves output from a microcomputer of a television receiver or the like.

0002

2. Description of the Related Art In recent years, data transmission means have been used in many ways, and pulse width modulated waves (hereinafter referred to as PWM waves) are widely used as one of the means.

A conventional PWM wave integrating circuit will be explained below with reference to the drawings. FIG. 3 shows a PWM wave in a waveform diagram. In the figure, t1 is the pulse width of the PWM wave, and t2 is P
During the period when the WM wave is at the low level 'L', t3 represents the time length corresponding to the period of the PWM wave.

FIG. 4 shows a circuit diagram of a conventional PWM wave integration circuit. In the figure, an output terminal 2 of a microcomputer (hereinafter referred to as microcomputer) 1 that generates PWM waves
The input terminal 3 of the integrating circuit is connected to the input terminal 3, and the input terminal 3 is connected to the base of the transistor Q1 through a parallel circuit of a diode D1 and a resistor R2.
Connected to CC. The base of transistor Q1 is grounded through capacitor C1, and the emitter is grounded through resistor R3.
A collector is connected to the power supply VCC. A voltage obtained by integrating the PWM wave is output from the emitter of transistor Q1. The voltage of power supply VCC is approximately 12 volts.

At the output terminal 2 of the microcomputer 1, the pulse width t1
It becomes an open end during the period t2, and operates as a current sink during the low level period of period length t2, and generates a predetermined PWM wave at the input terminal 3 with the resistor R1 as a load.

The operation of the above configuration will be explained. During the period of pulse width t1, the microcomputer 1 becomes an open terminal, and the capacitor C1 is charged with the power supply voltage VCC via the resistor R1, and the charging time constant is approximately R1×C1. Next, during the low level period of period length t2, the capacitor C1
The charge is transferred to the resistor R2 by the current sink of the microcontroller.
The time constant is approximately R2×C1. That is, during the charging operation, the diode D1 is conductive, so charging is performed almost exclusively through the resistor R1, and during the discharging operation, the diode D1 is in the opposite direction, so discharging is performed almost exclusively through the resistor R2. Therefore, the charging and discharging time constants are switched by the diode D1. This charging/discharging operation generates an integrated voltage in the capacitor C1 that increases with the pulse width, and this integrated voltage is output from the emitter of the transistor Q1. (However, it decreases by the voltage VBE between the base and emitter of the transistor.) This integrated voltage increases almost in proportion to the pulse width t1, but depending on the relationship between the charging time constant and the discharging time constant, it curves into a linear curve or a quadratic curve. This is a relationship.

FIG. 5 shows when the charging time constant and discharging time constant are almost equal, FIG. 6 shows when the charging time constant is much larger than the discharging time constant, and FIG. 7 shows when the charging time constant is much smaller than the discharging time constant. The relationship between the pulse width and the integrated voltage is shown in a graph.

[0008]

[Problem to be solved by the invention] Such a conventional PW
In the M-wave integrator circuit, as shown in Figures 5, 6, and 7, the characteristics of the integrated voltage with respect to the pulse width are approximately nonlinear or 2
The relationship is the following curve. When using the voltage obtained by integrating the PWM wave as a control voltage to be supplied to other electronic circuits, it may be necessary to obtain an integrated voltage such as a cubic curve change, but such an integrated voltage cannot be obtained with conventional integrating circuits. There were no problems.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a PWM wave integration circuit in which the relationship between pulse width and integrated voltage can be set to any desired relationship, including changes in cubic curves.

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a capacitor for accumulating electric charge, a charging resistor for charging the capacitor, a discharging resistor for discharging the charged electric charge, and a discharging resistor for discharging the charged electric charge. A circuit comprising a charging/discharging circuit configured with a charging resistor or a diode that bypasses the discharging resistor, and generating an integrated voltage across the capacitor by integrating a width-modulated pulse train with different charging time constants and discharging time constants. A Zener diode is inserted into the resistor of the charging/discharging circuit to provide a PWM wave integrating circuit in which the relationship between the pulse width and the integrated voltage is non-linear.

[0011]

According to the present invention, in the above structure, the Fenner diode changes the charging time constant and the discharging time constant depending on the integrated voltage, so that the relationship between the pulse width and the integrated voltage output becomes a high-order curved relationship.

0012

[Example] (Example 1) Hereinafter, PW of an example of the present invention
The M-wave integrator circuit will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of a PWM wave integrating circuit according to an embodiment of the present invention. In the figure, the output terminal 2 of the microcomputer 1 is controlled to be open during the pulse width period t1 and become a current silk during the low level period t2, as in the conventional example, and a predetermined PW is applied to the input terminal 3 using the resistor R1 as a load resistance.
Outputs M waves.

Input terminal 3 is connected to power supply voltage V via resistor R1.
It is connected to CC, via a diode D1 to the base of a transistor Q1, and to a capacitor C1 via a two-terminal circuit in which a resistor R1 is connected in parallel to a series connection of a resistor R4 and a Zener diode D2. The other end of capacitor C1 is connected to ground. The collector of the transistor Q1 is connected to the power supply voltage VCC, and the emitter is connected to ground via a resistor R3.

The operation of the above configuration will be explained. In the figure, when the pulse width is relatively small, the integrated voltage does not exceed the Zener voltage of the Zener diode D2, and therefore, due to the same operation as the conventional example without the Zener diode, the capacitor C1 becomes a resistor during the period of the pulse width t1. Charged to power supply voltage VCC via R1,
Its charging time constant is approximately R1×C1. During the low level period with period length t2, the charge in the capacitor C1 is discharged via the resistor R2, and the discharge time constant is R2×C
It is 1. In this case as well, the diode D1 performs the operation of switching the time constant during charging and discharging.

When the pulse width is sufficiently large and the integrated voltage of the capacitor C1 exceeds the Zener voltage of the Zener diode D2, discharge occurs through the resistor R1 and also through the series circuit of the resistor R4 and the Zener diode. However, the discharge time constant is smaller than the discharge time constant when the pulse width is small.

Resistors R1, R2, and R4 and the Zener voltage are set so that when the pulse width is small, the discharging time constant is much larger than the charging time constant, and when the pulse width is large, the discharging time constant is much smaller than the charging time constant. Then,
A characteristic that transitions from the downward quadratic curve characteristic shown in FIG. 5 of the conventional example to the upward quadratic curve characteristic shown in FIG. 7 is obtained,
A characteristic that can be regarded as a substantially cubic curve with an inflection point near the Zener voltage is obtained.

FIG. 2 graphically shows an example of the characteristics thus obtained. In the figure, the characteristic curve curves around the pulse width where the integrated voltage becomes the Zener voltage V1.

Note that the transistor Q1 constitutes a buffer circuit, and may be an operational amplifier, or may be omitted when a large output current is not required.

As described above, according to the PWM wave integration circuit of the embodiment of the present invention, a charging resistor for charging a capacitor, a discharging resistor for discharging the charged charge, and a diode for bypassing the discharging resistor during charging. In a circuit that generates an integrated voltage obtained by integrating a width-modulated pulse train across the capacitor, a series circuit of a resistor, a Zener diode, and a resistor is connected in parallel to the discharge resistor, and the pulse width vs. By using a PWM wave integrator circuit that is set so that the voltage relationship is non-linear, almost
A PWM wave integration circuit having a cubic curve can be realized.

[0021] In the embodiment, one Zener diode is used.
Although the relationship of the cubic curve was realized by using only one Zener diode, it is also possible to construct an integrating circuit having the characteristic of a complex curve of the third order or more by using a plurality of Zener diodes having different Zener voltages.

[0022]

As is clear from the above embodiments, the present invention includes a capacitor that stores charge, a charging resistor that charges the capacitor, a discharging resistor that discharges the charged charge, and a charge resistor or The circuit includes a charging/discharging circuit configured with a diode that bypasses the discharging resistor, and generates an integrated voltage across the capacitor by integrating a width-modulated pulse train with different charging time constants and discharging time constants. is inserted into the resistor of the charge/discharge circuit to form a PWM wave integrator circuit in which the relationship between pulse width and integrated voltage is non-linear, thereby creating an integrator circuit in which the characteristic of pulse width versus integrated voltage forms an arbitrary curve. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a PWM wave integration circuit according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of pulse width versus integrated voltage output characteristics in the PWM wave integration circuit according to the embodiment of the present invention.

[Figure 3] P
Waveform diagram showing the waveform of WM wave

[Figure 4] Circuit diagram showing the configuration of a conventional PWM wave integration circuit

[
Figure 5: Graph showing an example of pulse width versus integrated voltage output characteristics in a conventional PWM wave integration circuit

[Fig. 6] A graph showing an example of pulse width versus integrated voltage output characteristics in a conventional PWM wave integration circuit.

[Fig. 7] A graph showing an example of pulse width versus integrated voltage output characteristics in a conventional PWM wave integration circuit.

[Explanation of symbols]

R1 Charging resistance R2 Discharge resistance D1 Diode D2 Zener diode C1 Capacitor

Claims (1)

[Claims] 1. A charging/discharging device comprising a capacitor that stores charge, a charging resistor that charges the capacitor, a discharging resistor that discharges the charged charge, and a diode that bypasses the charging resistor or the discharging resistor. The circuit includes a circuit and generates an integrated voltage across the capacitor by integrating a width-modulated pulse train with different charging and discharging time constants, wherein a Zener diode is inserted into a resistor of the charging and discharging circuit, A PWM wave integration circuit in which the relationship between pulse width and integrated voltage is non-linear.