JPH0334171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relay drive circuit that drives and controls a relay by controlling conduction of a transistor connected in series with the relay, and the relay drive circuit is unlikely to malfunction even in the event of a momentary power outage of an AC power source. This is what we are trying to provide.

Generally, momentary power outages of AC power often occur on product assembly and manufacturing lines. The duration of this instantaneous power outage is usually 0.1 seconds. For example, when controlling a relay with a control circuit that has a timer function, a 0.1 second power outage will cut off the power supply to the control circuit, reset the control circuit, and the timer will also be in the reset state. There was a problem in that it was not possible to perform the operation.

Therefore, in normal relay drive circuits, the control circuit is required not to reset even in the event of a momentary power outage of 0.2 seconds or more. In order to lengthen this moment, the capacitance of the smoothing capacitor could be increased, but this resulted in a considerably large capacitor, which had the disadvantage of being unsuitable for commercialization in terms of space and cost.

Since the current flowing through the relay coil is relatively large, in the event of a momentary power outage, the relay is forcibly cut off using a transistor and the relay coil is The current is passed through the control circuit to extend the control circuit's ability to withstand instantaneous power outages.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an AC power source, to which a series circuit of a resistor 2, a diode 3, and a capacitor 4 is connected. Note that the resistor 2 and diode 3 are
It constitutes a rectifier circuit 5 that rectifies the AC power supply voltage. A constant voltage power supply circuit 8 in which a resistor 6 and a constant voltage diode 7 are connected in series is connected to the capacitor 4 in parallel, and a capacitor 9 and a control circuit 10 are connected in parallel to the constant voltage diode 7. A series circuit of a relay coil 12, a control transistor 13, and a cutoff transistor 14 is connected in parallel to the capacitor 4, and the control transistor is connected to the output of the control circuit 10 via a resistor 11 to control the relay. This is done by controlling the energization of the control transistor 13.

On the other hand, as a cutoff circuit for relay coil cutoff,
In the AC power supply 1, a resistor 19, a diode 20, and a capacitor 17 are connected in parallel with the series circuit of the rectifier circuit and capacitor 4. ing. A constant voltage diode 18 and a resistor 16 are connected in parallel to the capacitor 17, and a constant voltage is supplied through a resistor 15 connected in series to the base of the cutoff transistor 14.

Next, the operation in the above configuration will be explained.
The AC power supply voltage is rectified by the rectifier circuit 5, smoothed by the capacitor 4, and made constant by the constant voltage power supply circuit 8. A constant voltage (FIG. 2b) is generated across the constant voltage diode 7, and the control circuit 10 supplied to The output of the control circuit 10 is reduced in pressure by the resistor 11 and becomes an input signal to the transistor 13, and this signal controls the conduction of the transistor 13.
A current is passed through the relay coil 9 to control the relay.

Further, as a cutoff signal, the AC power supply 1 is rectified by a rectifier circuit 21, smoothed by a capacitor 17, made constant by a voltage regulating diode 18, and supplied to the cutoff transistor 14 through a resistor 15. Resistor 16 is for discharging capacitor 17.

Under the above conditions, the power supply voltage is from time T ₁ to T ₄
When the capacitor 4 is turned off, the potential across the capacitor 4 (a in FIG. 2) is discharged with a slope of A.
At the same time, the input power supply voltage of the control circuit 10 (b in FIG. 2) also has a slope of D, and the voltage across the capacitor 17 (c in FIG. 2) also has a slope of F, and discharge starts. At this time, the resistance value of the equivalent resistance 22 seen from the capacitor 4 is R ₂₂ , the capacitance of the capacitor 4 is C ₄ , the resistance value of the resistor 16 is R ₁₆ , and the capacitor 1
Assuming that the capacitance of 7 is _C17 , each value is set so that the following formula holds true.

C ₄ R ₂₂ ≫C ₁₇ R ₁₆ In this way, if the discharge time constant of capacitor 17 is made smaller than the discharge time constant of capacitor 4,
The voltage across capacitor 4 is higher than that of capacitor 17.
The voltage across it decreases faster. And time
When T ₂ occurs and the voltage across the capacitor 17 decreases to V ₁ , the cutoff transistor 14 turns off and cuts off the current flowing through the relay coil 12 .

After time _T2 , since the voltage across the capacitor 4 is only passed to the control circuit, it is discharged even with a slope B that is gentler than the slope A, and the input voltage of the control circuit 10 is also discharged with a slope E that is gentler than the slope D. do.
That is, if the input voltage at which the control circuit 10 is reset is _V2 , the control circuit 10 will be reset after a power outage.
The time required for the input voltage of G to reach _V2 is the instantaneous power outage resistance time, so if the relay is not turned off before the control circuit 10 is reset, the control circuit input voltage will exceed G at b in Figure 2. However, in this embodiment, the slope decreases at a slope E that is gentler than G, so that the _slope continues until time _T4 .

As is clear from the above description, the present invention is very effective as a countermeasure against instantaneous power outages that occur on a manufacturing line, and if the capacitance of the capacitor is appropriately selected, a circuit that is highly resistant to instantaneous power outages can be created.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of a relay drive circuit showing one embodiment of the present invention, and FIGS. 2a, b, c, and d are signal waveform diagrams of main parts of the same electric circuit. 1... AC power supply, 2... Resistor, 3... Diode, 4... Capacitor, 8... Constant voltage power supply circuit,
12... Relay coil, 13... Relay control transistor, 14... Cutoff transistor, 10
...Control circuit, 16...Resistor, 17...Capacitor.

Claims (1)

[Claims] 1 A series circuit of a resistor, a diode, and a capacitor connected to an AC power supply, a constant voltage power supply circuit connected in parallel to the capacitor, a relay coil, a relay control transistor, and a cutoff transistor connected in parallel to the capacitor. and a series circuit of
a control circuit that is driven by the output of the constant voltage power supply circuit and controls conduction of the transistor for controlling the relay; and a control circuit that is driven by the output of the constant voltage power supply circuit and controls conduction of the transistor for controlling the relay; A relay drive circuit including a cutoff circuit that cuts off the cutoff transistor.