JPH0237241Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an accurate time-limited power supply circuit with time-limited operation.

Conventionally, as a time-limited power supply circuit, there is a time-limited power supply circuit that utilizes charging of a capacitor.

In such a time-limited power supply circuit, even if the switch is opened during time-limited operation or after the time-limited operation ends, it takes a very long time for the charge in the capacitor to be completely discharged. If you do so, the timed operation may end in a short period of time.

This invention aims to provide a time-limited power supply circuit that can always perform accurate time-limited operations.

This invention will be explained below based on an illustrated embodiment.

In the figure, 1 and 2 are input terminals, input terminal 1
is connected to an output terminal 5 via a normally open contact 4 of a relay 3, which will be described later, and the input terminal 2 is connected to an output terminal 6.

Input terminal 1 is diode 7, resistor 8, relay 3
It is connected to the input terminal 2 via a parallel circuit with an excitation winding 9 and a smoothing capacitor 10, a capacitor of a transistor 11, and an emitter.

The connection point between diode 7 and resistor 8 is resistor 1
2, diode 13, capacitor 14 and resistor 1
It is connected to the input terminal 2 through 5 parallel circuits. These constitute an operating current supply circuit.

Further, the connection point between the diode 7 and the resistor 8 is connected to the input terminal 2 through a parallel circuit of a resistor 16, a resistor 17, and a smoothing capacitor 18.
The connection point between and the resistor 17 is connected to the inverter 19. These resistors 16 and 17 constitute a power switch open detection circuit.

Inverter 19 is connected to inverters 20a and 20b connected in parallel, and inverter 20a
and 20b are resistor 21, diode 22, resistor 2
3. Inverters 24, 25 and 26 and resistor 2
7 to the base of the transistor 11. These constitute a closing signal supply circuit.

The connection point 28 between the diode 22 and the resistor 23 is
It is connected to the connection point between the diode 13 and the resistor 15 through a parallel circuit with a resistor 29 and a diode 30, and is connected to the input terminal 2 through a capacitor 31.
It is connected to the. This resistor 29 and capacitor 3
1 constitutes a time constant circuit.

Input terminals 1 and 2, switch 3 on either one
2 to a power line 33, and output terminals 5 and 6 are connected to a load such as a light bulb 34.

The resistance value of the resistor 29 and the capacitance of the capacitor 31 are determined to obtain a desired time limit, and the resistance value of the resistor 15 and the capacitance of the capacitor 14 are set such that each capacitor 31 has a sufficient time to completely discharge. The value is set so that the operating current can be supplied to the inverter.

The time-limited power supply circuit configured as described above operates as follows.

Now assume that switch 32 is opened and all capacitors 10, 14, 18 and 31 are in a discharged state.

When the switch 32 is closed in this state, a direct current is obtained in the diodes 7 and 13, and the capacitor 14
is charged, and each inverter 19, 20
Operating current is supplied to a, 20b, 24, 25, and 26. Also, the capacitor 31 is connected via the resistor 29.
Charging current also flows through the At this time, since the voltage at the connection point 28 is at a low level, the output of the inverter 26 becomes a high level, the transistor 11 becomes conductive, current flows through the excitation winding 9, and the normally open contact 4 closes and the light bulb 34
lights up.

At this time, since the input of the inverter 19 is at a high level higher than the potential of the input terminal 2, the outputs of the inverters 20a and 20b are at a high level, so that no charging current flows toward the diode 22.

Next, when the capacitor 31 is charged and the voltage at the connection point 28 becomes high level, the transistor 11 becomes non-conductive, and the normally open contact 4 opens and the light bulb 34 lights up.

When the switch 32 is opened in this state, the supply of current is stopped, but the discharge current of the capacitor 14 causes each inverter 19, 20a, 20b, 24, 2
5 and 26 work. Furthermore, since the input of the inverter 19 becomes a low level equal to the potential of the terminal 2 by opening the switch 32, the input of the inverter 19 becomes a low level equal to the potential of the terminal 2.
The outputs of a and 20b also become low level. Therefore, the charge accumulated in the capacitor 31 is rapidly discharged to the output side of the inverters 20a and 20b.
Further, the charge accumulated in the capacitor 31 is transferred to each inverter 19, 20a, 2 via the diode 30.
It is also discharged as operating currents 0b, 24, 25, and 26.

Therefore, even if the switch 32 is opened once and then closed again within a short period of time, the capacitor 31 has already completely discharged by the time it is closed again, so that accurate time-limited operation can be obtained.

As described above, according to this invention, a discharge circuit is provided that short-circuits a capacitor whose time limit is determined by the charging time to a low potential point when the power switch is opened. is rapidly discharged. Therefore, when the switch is closed again, no charge remains in the capacitor, so that accurate time-limited operation can be performed.

In the above embodiment, the relay 3 may be replaced by another relay element such as a triac.

[Brief explanation of drawings]

The figure is a circuit diagram of an embodiment based on this invention. 3...Relay, 4...Normally open contact, 11...Transistor, 14,31...Capacitor, 19,2
0a, 20b, 24, 25, 26... Inverter, 21, 29... Resistor, 32... Switch, 3
4...Light bulb.

Claims (1)

[Scope of utility model registration request] A first terminal into which current flows and a second terminal into which current flows, each connected to a power supply via a power switch, a normally open switch and a load connected in series between the first and second terminals. , a time constant circuit in which a first resistor connected to the first terminal side and a first capacitor connected to the second terminal side are connected in series, and the first resistor and the first capacitor. a closing signal supply connected to the interconnection point of the normally open switch and supplying a closing signal to close the normally open switch until charging of the first capacitor is completed by closing the power switch; a circuit, a first and a second
includes second and third resistors connected in series between the terminals of the power switch, and the potential at the interconnection point of the second and third resistors becomes lower than the second resistor when the power switch is open.
a power switch open detection circuit whose input side is connected to the interconnection point of the second and third resistors, and whose input side is connected to the interconnection point of the second and third resistors; side is first
When the potential at the interconnection point of the second and third resistors is higher than the potential at the second terminal, the potential at the output side is also at the second terminal. The potential of the second and third
a discharge circuit in which the potential at the output side is also equal to the potential at the second terminal when the potential at the interconnection point of the resistors is equal to the potential at the second terminal; 2 capacitor, the electrode on the first terminal side of this capacitor is connected to the power supply terminal of the closing signal generation circuit and the discharge circuit, respectively.
and an operating current supply circuit, wherein the capacitance of the capacitor is selected to a value that enables supply of operating current to the closing signal generating circuit and the discharging circuit for a predetermined period of time even after the power switch is opened. Power supply circuit.