JPS5920691Y2 - Frequency-DC voltage conversion circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a frequency-DC voltage conversion circuit using a one-shot circuit (monostable multivibrator).

When the power supply of a frequency DC voltage conversion circuit using a one-shot circuit is an unstable power supply, a circuit that clamps the pulse output of the one-shot I circuit with a Zener diode has traditionally been used as a compensation circuit for power supply voltage fluctuations. ing.

However, although this circuit can keep the amplitude value of the pulse voltage constant, it is not possible to keep the pulse width of the one-shot circuit output pulse constant.

On the other hand, the pulse width, which is a characteristic unique to one-shot circuits, is also affected by power supply voltage fluctuations.

This has the disadvantage that conversion errors occur.

The present invention aims to eliminate this drawback and provide a wave frequency-to-DC voltage conversion circuit that has as high conversion accuracy as possible.

Hereinafter, the structure and operation of the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In the figure, 1 is a one-shot circuit which outputs a constant square wave to point C for each trigger when a trigger frequency signal is input to input terminal a.

2 is an amplifier circuit, which manually amplifies the pulse output to point C and outputs it to point d. 3 is a power supply voltage fluctuation compensation circuit. In the conventional circuit, the resistor R11 shown in China is Zener diode DZ1. It consisted only of DZ2, and in order to keep the amplitude of the pulse output at point d constant regardless of fluctuations in the power supply voltage, the voltage was clamped with a Zener diode, but the output of one-shot circuit 1 Since the pulse width also changes somewhat due to the influence of power supply voltage fluctuations, Zener diodes DZ1. According to the present invention, a resistor R1□ is added in series with DZ2.

For reference, the pulse width t is expressed by the formula: becomes.

However, C1... Capacity of capacitor C1, R4
...Resistance value of resistor R4, El...Power supply voltage, VD...Forward voltage of diode D2,
■BE・・・・・・Voltage between base and emitter of Tr2,
It is.

4 is a smoothing circuit for smoothing the square wave pulse into a DC voltage and outputs a DC voltage signal from point e.

5 is a power supply circuit.

Constituent element symbols in the figure indicate the following elements, respectively.

R1~R]3 are resistors, C1~C5 are capacitors, D
1 to D2 are diodes, DZ1 to DZ2 are Zener diodes, Tr1 to Tr4 are transistors, Rfl is a rectifier, and T1 is a lance.

FIG. 2 is a waveform diagram for explaining the operation, showing signal waveforms at points a to e in FIG.

In the circuit configuration shown in Fig. 1, when a 1 to 1 pulse frequency signal as shown in Fig. 2 A is inputted to three points, the one-shot circuit 1 outputs a square wave shown in Fig. 2 C to the 0 point. Ru.

To explain this operation, first, when the pulse signal A is input to the point a, the transistor Tr2, which had been dead until then, is turned on and the transistor Tr2 is turned on.
The Trl, which was 1 off, is turned on at the rising edge of the rigger pulse (t') signal.

Therefore, until then, the left terminal of the capacitor C1 was +E1pol), and the right terminal was almost O
The left terminal, which was charged at 10V l) volts, drops to O volts when the Tr is turned on, so the right terminal becomes -(ElVBE V) volts.

Therefore, Tr2 is turned off. In this state, C1 is the resistance R
4, the right terminal is gradually charged with positive charge.

When the right terminal reaches (VBE+Vo) volts, Tr2 is turned on.

When Tr2 turns on, the base voltage of Trl drops to O volts, so Trl turns off.

Thereafter, when the next 1-Riga pulse is manually applied to point a, the same operation is repeated.

Therefore, the potential at point b changes as shown in Figure 2, and becomes 0.
At the point, there is a capacitor C as shown in Figure 2 (c), (7) right side terminal car (El-vBE=VD) from (VB□+V
D) A square wave with a pulse width determined by the charging time until the voltage is charged will be output.

Then, the output of the 0 point is amplified by the amplifying circuit 2 and becomes the Tr.
The collector-emitter saturation voltage of Tr2 and the voltage drop of D2 (VCE+VD) (however, ■ oE is the collector-emitter saturation voltage of Tr2
By removing the emitter-emitter saturation voltage), the waveform shown in FIG. 2 is obtained.

Thereafter, when the power supply voltage E1 increases, the width of the square wave output from the one-shot circuit 1 becomes smaller due to the compensation circuit 3, but on the other hand, the amplitude increases, so the current flowing through the resistor R1+ increases. , resistance R], the voltage drop due to l becomes large.

Therefore, the output waveform from the compensation circuit 2 has an amplitude increased by the voltage drop.

That is, the amplitude is increased by the amount that the width is reduced, and the area of the square wave is compensated so that the polarity is constant, thereby eliminating the influence of power supply voltage fluctuations as much as possible.

Next, the output from the compensation circuit 3 is smoothed by a smoothing circuit 4, and a DC voltage as shown in FIG. 2E is outputted to the zero point.

As described above, the present invention brings about the excellent effect of increasing conversion accuracy.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of FIG. 1.

Claims (1)

[Scope of utility model registration request] A frequency signal is input to a one-shot circuit 1, and its output is input to a compensation circuit 3 directly or via a middle circuit 2, and after voltage clamping with a Zener diode, a smoothing circuit 4
In the frequency-DC voltage conversion circuit that converts the signal into a DC voltage signal through the frequency-DC voltage converter circuit, a series resistor is inserted in the Zener diode of the compensation circuit 3 to reduce conversion errors caused by fluctuations in the power supply voltage. DC voltage conversion circuit.