JPS6362052B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention uses a normally open contact to supply power to a load, and when driving, applies a high voltage to a relay coil.
Regarding the improvement of a relay drive circuit configured to reduce the voltage applied to the relay coil after contact adsorption,
In particular, the present invention relates to a relay drive circuit that quickly returns even if the contacts are separated due to vibration, impact, etc., and does not cause the load to malfunction.

Relays are often used in equipment to perform amplification, switching, etc., but in such cases, a problem arises in that the relay coil generates heat.
This is not so much of a problem when used in equipment such as experimental equipment where the operating atmosphere is not too harsh, but for equipment used in places where both temperature and voltage can vary over a wide range, such as in vehicles,
There are few that are fully satisfactory, and even those that do exist are extremely expensive. In addition, the relay ambient temperature often does not match the air temperature, and if the relay is built into a device housing, no matter where you choose to install the housing, the relay coil will generate heat, and in extreme cases, the temperature inside the housing will be higher than the temperature outside the housing. The temperature will be 20-30℃ higher. It is necessary to suppress the heat generation of the relay coil as much as possible in order to ensure the reliability of not only the relay itself but also other parts used, and also to avoid sacrificing the maximum operating ambient temperature and maximum operating voltage of the device. Conventionally, when driving a relay coil, a high voltage equal to or higher than the rated voltage is applied to the relay coil to ensure that the contacts operate, and after the contacts are attracted, a reduced voltage is applied as a holding voltage to reduce the power output. Measures were taken to achieve savings and heat generation control. This will be explained according to the illustrated example. FIG. 1 shows a conventional relay drive circuit diagram. When switch 1 is turned on to operate the relay drive circuit, current I1 flows through the positive terminal of power supply 2 → switch 1 → capacitor 3 → resistor 4 → base of transistor 5 → emitter of transistor 5 → negative terminal of power supply 2, The collector and emitter of transistor 5 are made conductive. As a result, the current I2 flows from the positive terminal of the power supply 2 to the switch 1 to the coil 6a of the relay 6 to the collector of the transistor 5 to the emitter of the transistor 5 to the negative terminal of the power supply 2 to excite the coil 6a of the relay 6. The contact point 6b is quickly attracted to attract the contacts 6b and 6c, and power is supplied to the load 7. By the way, the current I1 becomes the maximum current when the switch 1 is turned on (ON) as shown in FIG. 2 due to the time constant circuit composed of the capacitor 3 and the resistor 4, and decreases as time t passes. Therefore, the current I2 saturates to a current determined by the voltage of the power source 1 and the resistance value of the coil 6a for a certain time t1 after the switch 1 is turned on, and the voltage _VRY applied to the coil 6a becomes the voltage of the power source 1. Thereafter, as the current 1 decreases, the transistor 5 enters the active region, the collector-emitter voltage V _CE increases, and the current I2 gradually decreases. As the voltage V _CE increases, the collector of transistor 5 -
A current I3 begins to flow through the resistor 8 connected between the emitters. When current I2 becomes zero, current I3
are the voltage of power supply 1, the resistance value of coil 6a, and resistance 8
The current is determined by the sum of the resistance values of the coil 6a.
A voltage obtained by subtracting the voltage drop across the resistor 8 from the voltage of the power source 1 is applied to the voltage. The relay When driving the coil 6, the voltage of the power supply 1 is directly applied to ensure that the contact 6b is attracted, and after the contact 6b is attracted, the voltage applied to the coil 6a is reduced by the resistor 8, and the voltage applied to the coil 6 is
In addition to suppressing the heat generation of a, it also aims to save power.

By the way, when the conventional relay drive circuit described above is used in a device that is constantly exposed to vibrations and shocks, such as an in-vehicle device, the holding voltage is reduced, so the suction force is weak, and the contacts may be damaged due to vibrations or shocks. This could cause chattering, and in the worst case scenario, the contacts could separate, causing the device to malfunction, which could lead to an extremely dangerous situation, especially if the device was an important device such as an engine control device. As a result, the voltage cannot be reduced much, so the effect is weak, and the maximum operating ambient temperature or maximum operating voltage of the device has to be sacrificed to some extent.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional type, an object of the present invention is to provide a relay drive circuit that sufficiently reduces power consumption at all times to suppress heat generation, and that quickly attracts contacts when they are separated to eliminate malfunctions of the device. It's about doing.

The gist of the present invention is that during normal operation, a resistor is connected in series to the relay coil to reduce the voltage applied to the relay coil and suppress heat generation, and when the relay coil is driven or when the contacts are separated due to vibration, shock, etc. The purpose of this method is to detect the voltage difference between the contacts, use the voltage difference to operate a switching circuit, and use the output of the switching circuit to apply a high voltage to the relay coil to quickly restore the contacts.

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 3 shows a block diagram of a relay drive circuit according to the invention. In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals. When the switch 1 is turned on, the contact 6b of the relay 6 is electrically connected to the power supply 2, so that a voltage difference is generated between the contacts 6b and 6c. This voltage difference is detected by the detection circuit 9 and a contact "open" signal is output to the switching circuit 10.
The switching circuit 10 is brought into conduction by the contact "open" signal, and both ends of the coil 6a are directly connected to the power source 2 and a high voltage is applied to quickly attract the contact 6b, and the contacts 6b and 6c are closed.
When both contacts 6b and 6c are closed, the voltage difference between both contacts disappears, and detection circuit 9 outputs a contact "close" signal to switching circuit 10. The switching circuit 10 becomes non-conductive due to the contact "close" signal, and the coil 6a is connected to the power supply 2 via the resistor 8, so that the voltage applied to the coil 6a is equal to or less than the power supply 2.
The voltage is reduced to the voltage obtained by subtracting the voltage drop caused by the resistor 8 from the voltage of the coil 6a, thereby suppressing heat generation in the coil 6a and reducing power consumption. Next, a case where the contacts 6b and 6c become separated due to vibration, impact, etc. will be described. In this case, a voltage difference occurs between the contacts 6b and 6c, and since the coil 6a is directly connected to the power source 2 in the same way as when the switch 1 is turned on, the contact 6b quickly returns to the attracted state.

FIG. 4 shows a more specific relay drive circuit diagram of the embodiment. In the figures, parts corresponding to those in FIGS. 1 and 3 are designated by the same reference numerals.
When the switch 1 is turned on, the contact 6b of the relay 6 becomes electrically connected to the positive side of the power supply 2. On the other hand, contact 6c has load 7
Since conduction is conducted to the negative electrode side of the power supply 2 through
A current I4 flows through the transistor 2, conduction occurs between the emitter and the collector of the transistor 11, and a high-level voltage, which is a contact "open" signal, appears at the collector of the transistor 11. This voltage causes the switching circuit 10
A current I5 flows through the resistor 13, the base and the emitter of the transistor 14, and the collector and emitter of the transistor 14 are electrically connected. As a result, the coil 6a
The voltage of the power supply 2 is directly applied to the coil 6a, the collector and the emitter of the transistor 14, and the current I6 quickly attracts the contact 6b, thereby closing the contacts 6b and 6c. When both contacts 6b and 6c are closed, the voltage difference between both contacts disappears, current I4 stops flowing, and the emitter of transistor 11
There is no conduction between the collectors. As a result, the collector of the transistor 11 loses the high-level contact "open" signal and becomes open, which causes the contact to "close".
Since the current I5 becomes a signal and stops flowing, the transistor 14 is turned off and the current I6 stops flowing, and the current I7 starts flowing through the resistor 8 instead. Therefore, the voltage applied to the coil 6a is reduced to a voltage obtained by subtracting the voltage drop due to the resistor 8 from the voltage of the power supply 2, and becomes the holding voltage of the contact 6b.

Next, a case where the contacts 6b and 6c become separated due to vibration, impact, etc. will be explained. In this case, a voltage difference is generated between both contacts, and since the coil 6a is directly connected to the power source 2, similar to when the switch 1 is turned on, the contact 6b is quickly attracted and returns to the attracted state.

FIG. 5 shows a circuit diagram of another embodiment of the invention. In the figures, parts corresponding to those in FIGS. 1, 3, and 4 are designated by the same reference numerals.

When the switch 1 is closed, the contact 6b of the relay 6 is electrically connected to the positive side of the power supply 2 via the load 7. On the other hand, since contact 6c is electrically connected to the negative pole side of power supply 2, a voltage difference occurs between contacts 6b and 6c, and a high level voltage, which is a contact "open" signal, is applied to terminal A of resistor 15, which is a detection circuit. appear. Due to this voltage, a current I8 flows through the base emitter of the transistor 16 constituting the switching circuit, and conduction is established between the collector and emitter of the transistor 16. As a result, the voltage of the power supply 2 is directly applied to the coil 6a,
Current I9 flows through the coil 6a, the collector and emitter of the transistor 16, and quickly attracts the contact 6b, closing the contacts 6b and 6c. When both contacts are closed, the voltage difference between both contacts disappears, and a low-level contact "close" signal appears at terminal A of resistor 15. This signal stops current I8 from flowing, turning off transistor 16, and current I9 flows. gone,
Instead, current I10 begins to flow through resistor 8. Therefore, the voltage applied to the coil 6a is reduced to a voltage obtained by subtracting the voltage drop due to the resistor 8 from the voltage of the power supply 2, and becomes a low voltage enough to hold the contact 6b.

Next, if the contacts 6b and 6c are separated due to vibration or shock, a voltage difference will be generated between the two contacts, and the coil 6a will be directly connected to the power source 2, just like when the switch 1 is turned on, as described above. The contact 6b is quickly attracted and returns to the suction state.

In this embodiment, a capacitor 17 is inserted in parallel with the resistor 15 to improve the responsiveness of the transistor 15 when the contacts 6b and 6c are separated.

As detailed above, according to the present invention, during normal operation of the relay, a resistor is connected in series with the relay coil to reduce the voltage applied to the relay coil, and when the contacts are separated, the voltage difference between both contacts is detected. The switching circuit is activated by the voltage difference, and the output of the switching circuit is used to apply high voltage to the relay coil.During normal operation, heat generation is suppressed and the relay and the equipment using it are It can raise the maximum working atmosphere temperature and maximum working voltage of the relay, and extend its life. Also, if the contacts come apart when driving the relay coil or due to vibrations, shocks, etc., the contacts can be quickly attracted to prevent equipment malfunction. It is very effective and can be prevented. In addition, since the voltage difference between relay contacts is used, the number of elements in the circuit configuration does not increase significantly compared to conventional circuits, and in some cases it may decrease, and it is also necessary to use large capacitors. It also has the excellent effect of being very inexpensive since there is no such thing.

[Brief explanation of drawings]

Fig. 1 is a conventional relay drive circuit diagram, Fig. 2 is a diagram of each current and voltage waveform shown in Fig. 1, Fig. 3 is a block diagram of a relay drive circuit according to the present invention, and Fig. 4 is an embodiment of the present invention. FIG. 5 shows a relay drive circuit diagram illustrating another embodiment of the present invention. 1: Switch, 2: Power supply, 3, 17: Capacitor, 4, 8, 12, 13, 15: Resistor, 5, 1
1, 14, 16: transistor, 6: relay, 6
a: Relay coil, 6b: Relay movable contact, 6
c: Relay fixed contact, 7: Load, 9: Detection circuit,
10: Switching circuit, I1 to I10: Current, V _CE : Voltage between collector and emitter of transistor.

Claims (1)

[Claims] 1 In a relay drive circuit configured to supply power to a load using normally open contacts, there is a detection circuit that detects the open/closed state of the contacts based on the voltage difference between the relay contacts, and an output from this detection circuit that turns ON. ，
It consists of a switching circuit that is turned off and a resistor connected in parallel to the switching circuit.
A relay drive circuit characterized in that a parallel circuit of the switching circuit and a resistor, and a relay coil are connected in series between both positive and negative terminals of a power source.