JPH0364973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an off-delay circuit, and more particularly to an improvement in the manner in which the off-delay circuit is reset and delayed by an external contact switch.

In the conventional type, as shown in Fig. 1, the power supply 1,
A comparator 10 is connected between the input voltage terminal 1 and the voltage dividing resistors 8 and 9 are connected to the reference voltage terminal 11.
2, connect one end of the time-limiting resistor 6, and form a discharge circuit with the time-limiting capacitor 5 and the time-limiting resistor 7,
It is connected to the power supply 1 through a resistor 4 and a contact switch 3, and a voltage dividing resistor 1 is connected to the output terminal of the comparator 10.
6 and 17 are connected to each other, and connected to the base of a transistor 18, and connected together with an output relay 19 between power supplies 1 and 2.

In the conventional delay circuit having such a configuration, when the power supplies 1 and 2 are applied, the voltage at the reference voltage terminal V ₁
>The voltage at the input voltage terminal is _V2 , so the output terminal 13 is at L level, so the output relay 19 does not operate. Next, turn on contact switch 3 to reset.
When the circuit is closed, the time-limiting capacitor 5 is charged via the resistor 4, and when the voltage V ₁ <voltage V ₂ is reached, the output terminal 13 of the comparator 10 is inverted to H level, the transistor 18 is turned on, and the output relay 19 is operated. . Then, when the contact switch 3 is opened to start the delay operation, the electric charge in the time-limiting capacitor 5 is charged by the time-limiting resistors 6 and 7 for a predetermined period of time, and the voltage increases again.
When V ₁ >voltage V ₂ , the output relay 19 performs a delayed recovery operation. By the way, this discharge time T ₁ is determined by the amount of charge at our facility, and the voltage curve A shown in Figure 2 shows the discharge time T ₁ obtained in a normal case. Since the switch is a contact point, its contact resistance is likely to fluctuate.In particular, the resistance value of the resistor 4 is set to a low value in order to quickly conduct electricity to the time-limited capacitor 5, so the contact resistance value of the contact switch 3 is The increase acts to reduce the initial charge amount of the time-limiting capacitor 5, and the voltage decreases as shown in the voltage curve B in Fig. 2, and the discharge time _T2 is also shortened. There was a drawback that delay time could not be obtained.

The present invention has been made in view of the above-mentioned conventional problems, and an embodiment of the present invention will be described below with reference to FIG.

A time-limiting resistor Rt and a time-limiting capacitor are connected between power supplies _E1 and _E2.
Ct are connected in series, and _the time-limiting capacitor Ct is connected to the input voltage terminal ₂ of a comparator _IC , which is a semiconductor integrated circuit for voltage comparison _. The point is connected to the reference voltage terminal 1, and the output terminal 3 of the comparator IC is connected to the power source _E1 via the output relay Ry.

A transistor Q ₂ that supplies sufficient charge to the time-limiting capacitor Ct and a resistor R ₆ are connected in parallel to the time-limiting resistor Rt, and the base of the transistor Q ₂ is connected to the resistor
It is connected to the power supply E ₁ through R ₅ and to the power supply E ₂ through a capacitor C ₁ , and is connected to a resistor for protecting the contact switch S (e.g. micro switch or other) for delayed reset and timed start. It is connected in parallel to the time-limiting capacitor Ct via _R7 .

The off-delay circuit configured in this way is first connected to the power supply.
A power supply is applied between E ₁ and E ₂ , and as the voltage V ₁ at the reference voltage terminal 1 of the comparator IC rises, the resistor R ₅ , the emitter of the transistor Q ₂ ,
Transistor Q ₂ through the base, capacitor C ₁
The base current flows through the resistor _R6 , _the emitter of transistor _Q2 ,
A charging current flows to the time-limited capacitor Ct through the collector, and the voltage V ₂ at the input voltage terminal 2 also rises, and the resistor R5 and capacitor C ₁ are connected so that sufficient charging is performed until the voltage V ₂ >voltage V ₁ . The value has been determined. Since the voltage _V2 is higher, the output terminal 3 of the comparator IC becomes H level, and the output relay Ry does not operate.

Next, in order to reset the output relay Ry to the closed state from the external terminal, when the contact switch S is closed, the charge of the time-limiting capacitor Ct is transferred to the contact switch via the low-resistance resistor _R7 since it is for protection. The voltage V ₂ becomes less than the voltage V ₁ , and as shown in the time chart of FIG. 4, the output terminal 3 of the comparator IC is inverted to the L level and the output relay Ry is activated. Here, even if the contact resistance of the contact switch S increases, the turn-on time of the output relay Ry may be delayed; There is no effect in applications where there is sufficient closing time.

Then, in order to start the time limit, the contact switch S
When the circuit is opened again, the base current of transistor Q ₂ does not flow because capacitor C ₁ has been fully charged, and transistor Q ₂ is in the off state, so the time-limiting capacitor Ct is charged only through the time-limiting resistor Rt.
After a predetermined period of time has elapsed, the voltage V ₂ becomes greater than the voltage V ₁ and the output relay Ry completes the off-delay operation and returns. In this way, the OFF delay time is completely unaffected by changes in the contact resistance of the contact switch S, and an accurate OFF delay time t can be obtained.

By having the configuration described above, the present invention has the following features:
Since the contact switch S is closed during the reset operation and opened when the time limit starts, even if the contact resistance of the contact switch S fluctuates,
Since the circuit is opened during the off-delay operation, it is completely irrelevant, so that an accurate off-delay time can always be obtained.

[Brief explanation of drawings]

1 and 2 show a conventional example, with FIG. 1 being a circuit diagram and FIG. 2 being a charge/discharge curve diagram. 3 and 4 show an embodiment of the present invention, with FIG. 3 being a circuit diagram and FIG. 4 being a time chart thereof. E ₁ , E ₂ ... power supply, Rt ... time limit resistor, Ct ... time limit capacitor, IC ... comparator, R ₁ , R ₂ ...
...Voltage dividing resistor, 1...Reference voltage terminal, 2...Input voltage terminal, 3...Output terminal, _R5 , _R6 , _R7 ...Resistor,
C ₁ ... Capacitor, S ... Contact switch, Q ₂
...transistor.

Claims (1)

[Claims] 1 Connect a time limit resistor and a time limit capacitor in series to the power supply, connect the time limit capacitor to the input voltage terminal of a comparator with a voltage dividing resistor connected to the reference voltage terminal, and create a contact switch that closes at reset and reopens at time limit start. A transistor is connected in parallel to the time-limiting capacitor and quickly charges the time-limiting capacitor to a voltage higher than the reference voltage of the comparator by short-circuiting the time-limiting resistor before closing the contact switch, and after the charging of the time-limiting capacitor is completed. is connected to the base of a capacitor that turns off the transistor, and an output relay is connected between the output terminal of the comparator and the power supply, and the contact switch is closed to quickly discharge the time-limited capacitor and reverse the comparator. The off-delay circuit is characterized in that the output relay is turned on and the output relay is returned with a delay by re-inverting the comparator upon completion of charging of the time-limited capacitor by restarting the circuit.