JPS6349407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a delay circuit that inverts an output with a delay time after power is turned on.

(Problems with the Prior Art) In general, in this type of delay circuit, as shown in Figure 5, when a switch connected in series with a DC power supply A is turned on, a capacitor N is charged through a resistor C, and the voltage of this capacitor N is directly connected to the switching circuit H. There was one in which the output of comparator H was inverted when the voltage of power supply A exceeded a threshold value divided by resistor A and resistor G.

If the capacitor is as described above, there is a leakage current in the capacitor, so if the charging current is smaller than this leakage current, the voltage on the capacitor will not rise and this voltage will fall below the threshold of the switching circuit. If it is small, the output of comparator H in switching circuit E will not be reversed and a failure will occur, and this capacitor N must have a low leakage current, and the charging current must be reduced due to the leakage current of this capacitor N. Since the determined resistance C must be a small value, only a short delay time can be expected.

(Objective of the Invention) In view of the above-mentioned points, an object of the present invention is to provide a sufficient delay time without using a capacitor with low leakage current, and to eliminate the problem of the output not being reversed due to this leakage current. This is what I did.

(Embodiment) The present invention will be explained below based on FIGS. 1 and 2 showing an embodiment of the present invention. 1 is a DC power source having a positive electrode 1a and a negative electrode 1b, and 2 is a DC power source connected in series with the DC power source 1. The switch 3 on the positive electrode 1b side is a capacitor, and one end thereof is connected to the negative electrode 1b of the DC power supply 1. 4 is a second switching circuit (hereinafter simply referred to as a switching circuit), which connects the DC power supply 1
The voltage dividing resistors 5 and 6 and the power input of the comparator 7 are connected in parallel to the series circuit of the voltage dividing resistors 5 and 6, and the input (+) of the comparator 7 is connected to the voltage dividing point A of the voltage dividing resistors 5 and 6. In addition, the input (-) of the comparator 7 is connected to the other end B of the capacitor 3, and the output of the comparator 7 is used as the output 4a of the switching circuit 4. Note that the resistor 8 is connected in parallel with the capacitor 3 to discharge the charge of the capacitor 3, and is used as necessary. That is, this switching circuit 4 uses the voltage between the voltage dividing point A and the negative electrode 1b as a threshold value, and inverts the output 4a according to the voltage of the capacitor 3. Reference numeral 9 denotes a charging circuit, which includes a series circuit of the DC power supply 1 and the switch 2, a series circuit with a current-limiting resistor 11 in which a charging capacitor 10 is connected to the negative electrode 1b side, and a voltage dividing resistor 1.
2 and 13 and the power input of a comparator 14 as a first switching circuit are connected in parallel, and the input (+) of the comparator 14 is connected to the voltage dividing point C of the voltage dividing resistors 12 and 13. The input (-) of the comparator 14 is connected to the connection point D between the resistor 11 and the charging capacitor 10, and the output 14a of the comparator 14
A series circuit consisting of a reverse current prevention diode 15 and a current limiting resistor 16 is connected between the terminal B of the capacitor 3 and the other end B of the capacitor 3, and the comparator 14 thresholds the voltage between the voltage dividing point C and the negative electrode 1b. The output 14a is inverted according to the voltage of the charging capacitor 10. That is, the charging circuit 9 starts charging the capacitor 3 from the time the switch 2 is turned on.
The capacitor 3 is charged until the voltage becomes higher than the threshold voltage of the switching circuit 4, and then charging of the capacitor 3 is stopped. Note that when the potential of the input (+) is lower than the potential of the input (-), the comparators 7 and 14 make the output almost the same potential as the negative electrode 1b of the current power source 1, and the potential of the input (+) is input (-)
If the potential is higher than the positive 1 of DC power supply 1, the output is
The potential is approximately the same as that of a.

Furthermore, FIG. 2 shows the negative electrode 1b of the DC power supply 1 in FIG.
is an operating time characteristic diagram with reference potential as D, D is the voltage at connection point D, and 14a is the output 14 of the comparator
The voltage at a, B is the voltage at the other end B of capacitor 3, 4
a is the voltage of the output 4a of the switching circuit 4, Vl
is the voltage at voltage division point C (threshold value of comparator 14), V
2 indicates the voltage at the voltage dividing point A (threshold value of the switching circuit 4).

To explain the operation using the negative electrode 1b as a reference potential, when the switch 2 is open (before time a in FIG. 2), the voltage across the capacitor 3 is zero and the output 4a of the switching circuit 4 is is zero.

Furthermore, when the switch 2 is turned on (after time a in FIG. 2), the charging circuit 9 is connected to the charging capacitor 10.
is charged through the current limiting resistor 11, and the voltage at this connection point D becomes the voltage at the voltage dividing point C (threshold value of the comparator 14).
The voltage of the output 14a of the comparator 14 is set to approximately the same voltage as the positive electrode 1a of the DC power supply 1 until the output 1
4a, the capacitor 3 is charged through the reverse current prevention diode 15 and the current limiting resistor 16, and when the voltage at the connection point D becomes equal to or higher than the voltage at the voltage dividing point C (threshold value of the comparator 14), the output 14a of the comparator 14 is set to approximately the same voltage as the negative electrode 1b, and charging to the capacitor 3 is stopped. Furthermore, when the switch 2 is turned on (after time a in Fig. 2), the output of the switching circuit 4 remains unchanged until the voltage of the capacitor 3 reaches the voltage at the voltage division point A of the switching circuit 4 (threshold value of the switching circuit 4). 4a becomes the same voltage as the positive electrode 1a of the DC power supply 1, and when the voltage of the capacitor 3 is charged and exceeds the voltage at the voltage division point A of the switching circuit 4 (threshold value of the switching circuit 4), the output 4a becomes the negative electrode 1b. The voltage is almost the same. Furthermore, the voltage of the charged capacitor 3 is discharged by the resistor 8 or the leakage current of the capacitor 3 and decreases, and the voltage of the capacitor 3 becomes lower than the voltage of the voltage division point A of the switching circuit 4 (threshold value of the switching circuit 4). Then, the output 4a of the switching circuit 4 is inverted and becomes approximately the same voltage as the positive electrode 1a, and the output is inverted with a delay time from when the power is turned on. Furthermore, when the switch 2 is turned on, until the capacitor 3 is charged, an output of approximately the same voltage as the voltage of the positive electrode 1a is output to the output 4a of the switching circuit 4, but when this output is not needed, the output 4
An integral circuit may be added to a and eliminated. Furthermore, in order to shorten the rise time of the output voltage of the output 4a of the switching circuit 4, a switching circuit such as a Schmitt trigger circuit may be connected to this output 4a.

In addition, as shown in FIG. 3 of the drawings shown as another embodiment, the switching circuit 4 is connected in parallel to the capacitor 3 with voltage dividing resistors 17 and 18 that also serve as discharge, and the switching circuit 4 is connected to the voltage dividing point of the voltage dividing resistors 17 and 18. transistor 19
A voltage dividing resistor 1 corresponding to the operating voltage between the base and emitter of the transistor 19 is connected to the base of the transistor 19.
The voltage between 7 and 18 may be used as a threshold value to cause the transistor 19 to perform a switching operation, thereby inverting the output 4a deposited on the collector of the transistor 19. Note that the resistor 20 limits the current flowing to the collector of the transistor 19. Furthermore, when the switch 2 connecting the charging circuit 9 in series with the DC power source 1 is turned on, the charging capacitor 22 is charged through the current limiting resistor 21, and the charging capacitor 22 is charged through the current limiting resistor 21.
The voltage of the transistor 25 is divided by the voltage dividing resistors 23 and 24, and the base of the transistor 25 serving as the first switching circuit is connected to this voltage dividing point.
By switching the transistor 25 using the operating voltage between the base and emitter of the switching circuit 4 as a threshold, the capacitor 3 is charged through the current limiting resistor 26 and the reverse current prevention diode 27 to a voltage higher than the threshold of the switching circuit 4. It may also be possible to stop.

As shown in FIG. 4, which is shown as another embodiment, when the voltage of the capacitor 3 in the switching circuit 4 is discharged by the resistor 28 and the leakage current range of the capacitor 3 is lowered, this voltage becomes the threshold value of the inverting circuit 29. The output 4a connected to the output of the negative circuit 29 may be inverted based on the reference value. Furthermore, resistance 3
0 limits the current flowing to the input of the negative circuit 29. Furthermore, when the switch 2 connecting the charging circuit 9 in series with the DC power source 1 is turned on, the charging capacitor 32 is charged through the current limiting resistor 31, and the voltage of the charging capacitor 32 is transferred to the negative circuit 33 as the first switching circuit. The output of the negative circuit 33 may be inverted based on the threshold value of , and the voltage may be charged through the current-limiting resistor 34 and the backflow prevention diode 35 to a voltage higher than the threshold value of the switching circuit 4, and then stopped.
Note that the resistor 36 limits the current flowing to the input of the NOT circuit 33.

(Effects) As described above, the present invention includes a first capacitor and a second capacitor that start charging when the power is turned on, and is inverted when the voltage at one end of the first capacitor exceeds a threshold value. the voltage at one end of the first switching circuit that stops charging the second capacitor and the voltage at one end of the second capacitor that starts discharging due to the reversal operation of the first switching circuit does not fall below a threshold value. and the second output which is inverted and output.
Since the switching circuit is constructed with a switching circuit, a sufficient delay time can be obtained without using a capacitor with low leakage current, and the problem of the output not being reversed due to this leakage current can be avoided.

[Brief explanation of the drawing]

Figures 1 and 2 show one embodiment of the delay circuit of the present invention, Figure 1 is a circuit diagram, Figure 2 is an operating time characteristic diagram, and Figures 3 and 4 are diagrams of other delay circuits of the present invention. A circuit diagram showing an embodiment, FIG. 5 shows a circuit diagram of a conventional delay circuit. 1...DC power supply, 1a...Positive pole, 1b...Negative pole, 2...Switch, 3...Capacitor, 4...
Second switching circuit, 4a...output, 5, 6
...Voltage dividing resistor, 7... Comparator, 8... Resistor, 9...
...Charging circuit, 10...Charging capacitor, 11...
... Current limiting resistor, 12, 13... Voltage dividing resistor, 14...
... Comparator, 15 ... Backflow prevention diode, 16
... Current limiting resistor, 17, 18... Voltage dividing resistor, 19
... Transistor, 20 ... Resistor, 21 ... Current-limiting resistor, 22 ... Charging capacitor, 23, 24
...Voltage dividing resistor, 25...Transistor, 26...
Current-limiting resistor, 27...Reverse current prevention diode, 2
8...Resistance, 29...Negation circuit, 30...Resistance,
31... Current-limiting resistor, 32... Charging capacitor, 33... Inverting circuit, 34... Current-limiting resistor, 3
5... Capacitor for backflow prevention, 36... Resistor.

Claims (1)

[Claims] 1 having a first capacitor and a second capacitor that start charging when power is turned on;
a first switching circuit that inverts and stops charging the second capacitor when the voltage at one end of the capacitor exceeds a threshold; and a first switching circuit that starts discharging by the inverting operation of the first switching circuit. and a second switching circuit that inverts and outputs an output when the voltage at one end of the second capacitor falls below a threshold value.