JPS5840414Y2 - Initial set pulse generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit that reliably generates an initial set pulse for a digital circuit.

Generally, in a control system, a digital circuit composed of a flip-flop circuit or the like is often used, for example, as a drive control circuit for an electric motor.

In this case, it is necessary to apply a phase control pulse to the operation stop terminal of the drive control circuit to ensure that the drive control circuit of the motor is in the initial set state when the power to the digital circuit is turned on or turned on again.

For example, in the conventional circuit shown in FIG.
The base voltage of the transistor Tr is increased through charging.

Therefore, the transistor Tr starts to conduct, and the output voltage at the output terminal O starts to rise.

In this case, the power supply voltage at point a and the output voltage at point b increase according to curves A and B shown in FIG.

V in FIG. When is the operating voltage of the motor drive control circuit, the power supply voltage (curve A) is at time t.

The operating voltage is V. but the output voltage (curve B) is RC
Due to the time constant, the operating voltage V is delayed at time t□.

reach. Therefore, the initial set pulse can be reliably generated during the time t□-t1.

However, after the power is turned on and the power supply voltage becomes sufficiently higher than the operating voltage vo of the motor drive control circuit, the power is once shut off and the power supply voltage becomes the operating voltage V.

If the power is turned on again before the voltage drops below, the output voltage when turned on again is already the operating voltage V.

Since it is higher than that, it becomes impossible to generate an initial set pulse.

The purpose of the present invention is to provide an initial set pulse generating circuit of the type described above, which is appropriately connected and arranged so as to reliably generate an initial set pulse when power is turned on or when the power is turned on again after being temporarily cut off in a digital circuit. There is something to do.

The present invention provides a parallel connection circuit consisting of a series-connected discharging diode and a charging/discharging capacitor, a series-connected resistor, a Zener diode, and a light emitting element between a power supply positive terminal and a ground point. The connection point and the connection point of the resistor and Zener diode are interconnected, and the series connection circuit of the transistor and the output resistor that together with the light emitting element constitutes a photocoupler is connected to another voltage source. The photocoupler is provided between the photocoupler and the photocoupler at a higher operating voltage level using a Zener diode to ensure generation of an initial set pulse.

The invention will be explained with reference to the drawings.

As shown in Fig. 3, in the initial set pulse generation circuit of the present invention, a discharge diode D□ is connected between the power supply positive terminal 1 and GND.
and a capacitor C1 are connected in series, a charging/discharging resistor R1 is connected in parallel to the diode D1, and a Zener diode ZD and a light emitting diode LE are connected in parallel to the capacitor C1.
Connect the series circuit of D.

It is assumed that the Zener diode ZD has the voltage-current characteristics shown in FIG.

Further, a phototransistor PTr and an output resistor R2 are connected in series between a positive voltage source (for example, +5V) and GND,
The output is taken out from the connection point between the emitter of the phototransistor PTr and the resistor R2.

According to the present invention, a photocoupler PC is constituted by a light emitting diode LED and a phototransistor PTr.

In the initial set pulse generation circuit of the present invention configured in this manner, the photocoupler PC starts operating when the voltages at three points reach the operating voltage of the motor drive control circuit of 70 or higher.

Now, when the power is turned on, the voltage at point d is the curve CK in Figure 5.
- the operating voltage of the drive control circuit increases along with time to 70
As a result, the Zener voltage exceeds v1 at time tl', and thereafter reaches almost the saturation value.

In this case, the voltage at point C, and therefore the voltage at point e, increases along curve DK in accordance with the time constant of resistor R1 and capacitor C□, and at time t1 reaches the operating voltage V of the drive control circuit.

At the time t2, the Zener voltage becomes equal to or higher than the Zener voltage V+, and thereafter almost reaches the saturation value.

Therefore, the output terminal OK of the circuit shown in FIG.
The initial set pulse can now be generated.

That is, at time t□', the Zener diode ZD starts conducting, the light emitting diode LED starts emitting light, this excites the phototransistor PTr, and current begins to flow through its collector electrode circuit, and at time t2. It begins to generate output pulses.

Next, when the power supply is cut off at time t3, the power supply voltage begins to drop, and this voltage becomes the operating voltage v of the drive circuit.

If the power is turned on again at time t3' before the voltage drops to LED
does not emit light, the phototransistor PTr also remains non-conductive, and no output pulse is generated.

When the power supply voltage increases further and becomes equal to or higher than the Zener voltage V□ again at time t3'', the Zener diode ZD becomes conductive and the light emitting diode LED also emits light, thus exciting the base of the phototransistor PTr and starting to conduct this transistor PTr. .

This ensures that the initial set pulse is generated again at time t4.

In other words, the time t in the conventional circuit.

-40 is the time t1'~t2 and the time t3''~t of the present invention.
4, which is the operating voltage V of the drive control circuit.

Pulses can be generated reliably even when the power is turned on and off in a higher voltage range.

As is clear from the above, according to the present invention, the Zener diode ZD and the photocoupler PC are used in combination, and the bias voltage of the photocoupler PC is maintained at a higher value than that of the Zener diode ZDK, thereby ensuring the initial set pulse. can be generated.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a conventional initial set pulse generation circuit, FIG. 2 is a waveform diagram for explaining its operation, FIG. 3 is a connection layout diagram showing the configuration of the initial set pulse generation circuit of the present invention, and FIG. The figure is a waveform diagram showing the voltage-current characteristics of a Zener diode, and FIG. 5 is a waveform diagram for explaining the operation of the initial set pulse generating circuit of the present invention. R1...Charge/discharge resistor, C□...Capacitor, D□...Diode, ZD...
Zener diode, LED...Light emitting diode, PTr...Phototransistor xR2...
...Output resistance, PC...Photocoupler.

Claims (1)

[Scope of utility model registration request] A discharging diode and a charging/discharging capacitor connected in series,
A parallel connection circuit with a series-connected resistor, a Zener diode, and a light emitting element is provided between a power supply positive terminal and a ground point, and a connection point of the discharge diode and charge/discharge capacitor and a connection point of the resistor and Zener diode are interconnected. In addition, a series connection circuit of a phototransistor and an output resistor which together with the light emitting element constitute a photocoupler is provided between another voltage source and a ground point, and the operating voltage level of the photocoupler is set to a Zener diode. An initial set pulse generation circuit characterized in that the initial set pulse is generated reliably by increasing the initial set pulse.