JPS6394522A - Driving circuit for electromagnetic relay - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention is electronic temperature! This invention relates to a drive circuit for an electromagnetic relay used in a 1lflff device, etc.

[Prior art and its problems]

In electronic automatic temperature control devices such as those used in electric carpets, an electronically controlled electromagnetic relay is connected to an AC power source, and the contacts of this electromagnetic relay open and close the current flowing through the heating wire to adjust the temperature. A conventional example of such an electronic automatic temperature control device is shown in FIG. 5. In FIG. is the thermistor 6 connected to the AC power supply 5
A series circuit of a diode 8 and a capacitor 9 is connected in parallel with the resistor 7 of the series circuit of the resistor 7 and the resistor 7, and the voltage across the resistor 7 is half-wave rectified by the diode 8 to charge the capacitor 9. The capacitor 9 is connected so that the voltage of the capacitor 9 is applied to the input terminal of the Schmitt circuit 100 of the discriminator 2. Output part 3 is DC power supply 11.1! Magnetic relay 12) consists of a series circuit of transistors 13, and the output end of the discriminator 2 is connected to the base of the transistors 13. The electric heat +41A14 of the load is connected to the AC power source 5 via the contact 12a of the electromagnetic relay 12. When the temperature of the temperature control device is low, the temperature of the thermistor 6 is also low, and the resistance value of the thermistor 6 is high, so the voltage shared by the resistor 7 is relatively low, and the charging voltage of the capacitor 9 is also low.
Therefore, the input voltage of the Schmitt circuit 10 is low, and the output signal is at a high level (hereinafter, this high level signal will be abbreviated as H, and the low level signal in contrast to this H will be abbreviated as L). Therefore, transistor 13 turns on, and! Since the Mi relay 12 operates to close the contact 12a and allow current to flow through the heating wire 14, the temperature of the entire device rises. This temperature rise also causes the temperature of the thermistor 6 to rise and its resistance value to gradually decrease, so that the voltage shared by the resistor 7 gradually increases. When the charging voltage of the capacitor 9 increases accordingly and exceeds a certain value, the Schmitt circuit 10 operates and its output signal drops to L. When the output signal drops to L, transistor 13 is turned off and electromagnetic relay 12 is released. As a result, the contact 12a opens and the current to the T4 hot wire 14 is cut off. Therefore, the temperature of the device starts to fall, and by repeating this process, automatic temperature adjustment is possible. The voltage of the voltage B5 of this device v, the voltage of the capacitor 9 ■5
, the output signal of the Schmitt circuit 10■. , a time chart of the current (2) of the heating wire 14 is shown in FIG. The voltage ■ of the AC power supply 5 is a sine wave, but the voltage of the capacitor 9 is 1! Voltage (2) is a DC pulsating wave, and the waveform of its maximum value is approximately in phase with the positive half-wave waveform of voltage (V). Set voltage V at which the Schmitt circuit 10 operates. The voltage v1 when it exceeds is the highest value of the pulsating wave,
The voltage (2) lower than the other set voltage v2 of the Schmitt circuit 10 is the lowest value of the pulsating wave. Therefore, the temperature of the device gradually rises and Schmitt circuit 1
The time t when 0 operates is when the pulsating wave of voltage 2 reaches its maximum value, and is approximately in phase with the maximum positive value of voltage V. Then, the relay 12 is released a time TI later than the time t1. Furthermore, the temperature of the device gradually decreases and the Schmitt circuit IO operates at time t3 when the pulsation of voltage v1 reaches its lowest value, and this time t□ is just before the maximum positive value of voltage ■. , the relay 12 performs the suction operation with a delay of time T8 from time t2. In this way, Relay 12 was released. Attraction, in other words, opening and closing of 12a is always at the power supply voltage V. is in the positive direction, and the current I at this time is the voltage ■1
This opening/closing phase is fixed. By the way, it is well known that the contacts that open and close direct current have a transfer phenomenon in which one contact melts or evaporates and moves to the other contact when opening and closing, such as in the drive circuit of the electromagnetic relay of the 6-piece device. Even when alternating current is passed through a load, if the direction of current flow is always constant when switching the load, the same effect as switching DC current will occur, and a contact transfer phenomenon will occur between the contacts that are in contact with each other. This has the disadvantage that the contact surface becomes uneven, the contact surface becomes rough, the contact resistance increases, and eventually the unevenness fits together and the contacts are locked in a closed state. In order to prevent this, contact materials that do not easily cause the transfer phenomenon are usually used, but this is not always sufficient, and even if the transfer phenomenon is reduced, there are still disadvantages such as an increase in contact resistance.

[Purpose of the invention]

The purpose of the present invention is to prevent the phenomenon of contact movement;
Another object of the present invention is to provide an electromagnetic relay drive circuit that has a simple configuration and is inexpensive.

[Key points of the invention]

The gist of the present invention is to include an input signal circuit section that half-wave rectifies the voltage of an AC i source, and a Schmitt circuit that determines the magnitude of the voltage of this input signal circuit section and outputs an output signal. In an electromagnetic relay drive circuit that drives an electromagnetic relay with an output signal, an oscillator that outputs a signal with a frequency lower than the frequency of the voltage of the AC power source is provided,
The electromagnetic relay is driven by the logic output of the oscillator signal and the Schmitt circuit output signal, and the electromagnetic relay is attracted by the logic output of the oscillator output signal and the Schmitt circuit output signal. An object of the present invention is to provide an electromagnetic relay drive circuit in which the contact opening/closing timing due to release is made random with respect to the phase of the voltage of an AC power supply, thereby preventing the phenomenon of contact transfer. Note that if a rectangular wave oscillator that outputs a rectangular wave is used as the oscillator, logic processing by an integrated circuit can be easily performed.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 4. Components that are the same as those shown in FIG. 5 are given the same reference numerals, and detailed explanation thereof will be omitted. 1st
In the figure, the input signal circuit section 1 and the output section 3 are exactly the same as those of the conventional ones, so the explanation of these structures will be omitted. The main difference is that a low frequency rectangular wave oscillator 15 and a D-type flip-flop (hereinafter simply referred to as FF) 16 are provided. That is, the output terminal of the input signal circuit section 1 is connected to the Schmitt circuit lO, the output terminal of this Schmitt circuit 10 is connected to the D terminal of the FF 16, and the rectangular wave oscillator 1 is connected to the T terminal of this FF 16.
5 is connected, and the Q output terminal of the FF 16 is connected to the base of the transistor 13 of the output section 3. Figure 2 shows a time chart of voltage and current waveforms for typical parts of the circuit in Figure 1.
1. Charging voltage Vb of capacitor 9, Schmitt circuit 10
The output signal V, is the same as that of the conventional device shown in FIGS. 5 and 6, and this explanation will be omitted.The output signal v4 of the oscillator 15 is a rectangular wave, and The current flowing through the hot wire]4 is indicated by I. The operation shown in FIG. 1 will be explained below with reference to this time chart. When the temperature of the thermistor 6 rises and the charging voltage (■) of the capacitor 9 reaches the operating voltage (■) of the Schmitt circuit 10 at time t, the Schmitt circuit 10 operates and its output signal becomes VC-/:+<H, and the FF16 is applied to the D terminal of At this time, the output signal V of the FF 16 is H. Thereafter, when the signal V of the rectangular wave oscillator 15 with a frequency lower than the frequency of the AC power source rises, the output signal V of the FF 16 changes to L and turns off the transistor 13. And time T. After a delay, the electromagnetic relay 12 operates to open the contact 12a and cut off the current I flowing through the heating wire 14. The delay time T3 of the output signal v4 of the rectangular oscillator 15 applied to the T terminal of the FF 16 with respect to the rise of the output signal vc of the Schmitt circuit 10 is determined by the voltage V of the AC power supply 5 and the output signal v4 of the rectangular wave oscillator 15. The period of the output signal V of the square wave oscillator 15 is longer than the period of the voltage V of the AC power source 5, that is, it is lower than the frequency of the AC ttat, so the delay time T is random. becomes. Next, the temperature of the thermistor 6 decreases, and at time 1t, the capacitor 9 is charged? When the 1ttli pressure v1 drops to the lower operating voltage v2 of the Schmitt circuit 10, the Schmitt circuit 10 operates and its output signal vc becomes L. The output signal V of the FF 16 is the output signal of the square wave oscillator 15 after the Schmitt circuit 10 output signal ■9 becomes L.
The signal changes from L to H after a delay of time T4 until signal 4 rises. This turns on the transistor 13, and after a delay of time T2 after the transistor 13 turns on, the relay 12 turns on.
operates and the contact 12a closes. The delay time T4 is determined by the voltage ■1 of the AC power supply 5 as described above.
On the other hand, since the frequency of the rectangular wave oscillator 15 is low, it is random. FIG. 3 shows an embodiment different from the embodiment of the first rgJ, in which the input signal circuit section 1 and the output section 3 are exactly the same as the embodiment in FIG. 1, but the discrimination section 2 is different from the embodiment in FIG. 1. . That is, the discriminator 2 includes a Schmitt circuit 10, a rectangular wave oscillator 15, and a NOR gate 17 and a NAND gate 1 instead of FFs.
8 is provided, and this rectangular wave oscillator 15 outputs an H signal width of AC voltage ■. It is longer than the period of The output terminal of this square wave oscillator 15 is connected to one input terminal of a NOR gate 17, and the output terminal of the NOR gate 17 is connected to a NAND gate 18.
The output terminal of the Schmitt circuit 10 is connected to the other input terminal of the NAND gate 18 . The output terminal of NAND gate 18 is transistor 1
3 and the other input terminal of the NOR gate 17. FIG. 4 shows a time chart of voltage and current waveforms of a typical portion of the circuit shown in FIG. 3. Here, the voltage v of the AC power supply 5,
, the charging voltage of the capacitor 9 ■−, and the output signal of the Schmitt circuit 10 ■. , the current I of the heating wire 14 is the same as in FIGS. 1 and 2, so this explanation will be omitted.As for the output signal v4 of the oscillator 15, as already stated, the width of H is AC ll5.
It is made longer than the period of the voltage V of s. In this circuit, the signal applied to the base of the transistor 13 is the output signal of the NAND gate 18, which is indicated by . The operation of this circuit will be explained below with reference to this time chart. The temperature of the thermistor 6 rises, and at time 1. When the charging voltage of the capacitor 9 reaches the set voltage v1 of the Schmitt circuit 10, the Schmitt circuit 10 operates and the output signal vc of the Schmitt circuit 10 changes from L to H and NA
applied to the ND gate 18. At this time, the square wave oscillator 1
If the output signal v4 of the transistor 5 is H, the output of the NOR gate 17 is L, and the output signal V of the NAND gate 18 continues to be H, so the transistor 13 is not turned off. Output signal ■ of Schmitt circuit 10. Time T after becomes H
Suppose that the output signal v4 of the square wave oscillator 15 falls after s, the output of the NOR gate 17 becomes H, the output signal of the NAND gate 18 changes to L, the transistor 13 is turned off, and the Ml magnetic relay 12 is activated with a delay of time T1. In this circuit, the delay time T from when the charging voltage ■b of the capacitor 9 reaches the set voltage v1 of the Schmitt circuit 10 until the output signal ■4 of the square wave oscillator 15 falls is rectangular. Since the period of the H period of the wave oscillator 15 is longer than the period of the voltage V of the AC power source 5, it becomes random and the release time of the electromagnetic relay 12 is determined by the voltage of the AC IT source 5.
, the temperature of the thermistor 6 decreases randomly at time 1. The charging voltage of capacitor 9 is ■, which is a Schmitt circuit. Set voltage V! When the voltage drops to , the Schmitt circuit IO operates and its output signal vc becomes L. At this time, regardless of the state of the output signal 1 of the rectangular wave oscillator 15, the output of the NOR gate 17 is high because the output of the NAND gate 18 has been applied, so the NAND gate 1
8 changes to H, the transistor 13 turns on, and after a delay of time T8, the electromagnetic relay 12 is attracted and the contact 12a is closed. In this embodiment, the electromagnetic relay can be operated randomly, regardless of the phase of the voltage of the AC power source, only when the electromagnetic relay is released.

【Effect of the invention】

According to the present invention, the contacts of the electromagnetic relay are randomly opened and closed with respect to the phase of the AC i'a by the logical operation of the Schmitt circuit and the square wave oscillator that outputs a rectangular wave with a frequency lower than the power frequency of the AC power source. As a result, it is possible to prevent the phenomenon of transfer of the contact point and increase the trustworthiness of the contact point. Further, since dislocation of the contacts can be prevented using a low-cost integrated circuit without using special and expensive contact materials, it has the advantage that it can be constructed at low cost.

[Brief explanation of the drawing]

1 and 2 show an embodiment of an electromagnetic relay drive circuit according to the present invention, FIG. 1 is a wiring diagram thereof, and FIG. 2 is a time chart showing changes in voltage and current at each part of FIG. FIG. 3 is a wiring diagram showing a different embodiment of the present invention, FIG. 4 is a time chart showing changes in voltage and current at each part of FIG. 3, and FIG. 5 is a conventional 1! A wiring diagram showing an example of a drive circuit of a magnetic relay, and FIG. 6 is a time chart showing changes in voltage and current at each part of FIG. 5. 1: Input signal circuit section, 10: Schmitt circuit, 12: f
it magnetic relay, 15: square wave oscillator.

Claims (1)

[Claims] 1) an input signal circuit section that half-wave rectifies the voltage of an AC power source;
The electromagnetic relay drive circuit includes a Schmitt circuit that determines the magnitude of the voltage of the input signal circuit section and outputs an output signal, and drives the electromagnetic relay using the output signal of the Schmitt circuit. 1. An electromagnetic relay drive circuit, comprising: an oscillator that outputs a signal of a lower frequency than the oscillator; the electromagnetic relay is driven by a logical output of a signal from the oscillator and an output signal from the Schmitt circuit. 2) The electromagnetic relay drive circuit according to claim 1, wherein the oscillator is a rectangular wave oscillator that outputs a rectangular wave.