JPH10144195A - Relay drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the heating value of a relay coil efficiently by providing a reference voltage circuit supplying exciting current from a reference power source to the relay coil and a low voltage circuit supplying higher voltage than the return voltage of a relay, and supplying controlling for a predetermined time. SOLUTION: When a switch portion SW1 is turned on, the output voltage Vb of an on-vehicle battery 1 is applied to the coil RV1 of a relay RL1, and an applied voltage V1 to the coil RC1 becomes higher than an operating voltage Vs so that a relay contact RC1 is turned on. A base current is supplied through a resistor 11, and a transistor Q11 is turned on so that the anode voltage Vp of a diode 11 becomes equal to the output voltage Ve of a low voltage power source 3. After the relay contact is turned on by applying the output voltage Vb of the battery 1 to the coils of the respective relays, the output voltage Ve of the low voltage power source 3 is applied thereto so that the relay contact can be surely operated. A coil heating value is reduced comparing with a case. where the voltage Vb of the battery 1 is continuously applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay driving circuit for driving a relay for turning on / off a power supply from a power supply for outputting a constant voltage to a load.

[0002]

2. Description of the Related Art Conventionally, a circuit for driving various loads 2 of an automobile is configured by using a relay. This circuit is, for example, as shown in FIG.
One end of C is connected to the voltage output terminal of the vehicle-mounted battery 1, and the other end is grounded via the operation switch SW.
One of the relay contacts RS is connected to the voltage output terminal of the vehicle battery 1 and the other is grounded via the load 2.

When the operation switch SW is turned on and a voltage higher than the operating voltage required to operate the relay contact RS is applied to the coil RC, the relay contact R
S is activated to become conductive, while the operation switch SW
Is turned off, and when the voltage applied to the coil RC becomes equal to or lower than the reset voltage, the relay contact RS returns and returns to the non-conductive state.

In a motor vehicle, circuit components such as relays, fuses and connectors are mounted intensively in an electric junction box. However, since these circuit components generate heat, the heat resistance of each component and the electric junction box must not be exceeded. Had to be designed.

[0005]

However, in recent years, the number of relays has increased due to an increase in on-board electrical components, and the density of relays has been increased due to the miniaturization of relays. Therefore, it is necessary to suppress this heat generation. Generally, the operating voltage of the relay is about 7 to 8 V, the return voltage is about 2 to 3 V, and the power supply voltage of the on-vehicle battery is 12 V. Therefore, the relay is unnecessary only by the voltage difference between the power supply voltage of the battery and the operating voltage of the relay. It means that it is feverish.

An object of the present invention is to solve the above problem and to provide a relay drive circuit capable of efficiently reducing the heat generation of a coil.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an exciting current supplied to a coil of a relay having relay contacts interposed between a reference power supply outputting a constant voltage higher than the operating voltage of the relay and a plurality of loads. A low voltage power supply that outputs a voltage lower than the fixed voltage and higher than the reset voltage of each relay, and a relay from the reference power supply. A reference voltage circuit for supplying an exciting current to the coil of
A low-voltage circuit that supplies an exciting current to the coil of each relay from the low-voltage power supply; and a predetermined time elapses from a point in time when the exciting current is supplied from the reference power supply and the relay contact is activated. A stop control circuit for stopping the supply of the exciting current.

According to this configuration, when the exciting current is supplied from the reference power supply to the coil of each relay and a predetermined time elapses from the time when the relay contact is activated, the supply of the exciting current from the reference power supply is stopped. The excitation current is supplied from a low-voltage power supply that outputs a voltage lower than the constant voltage output from the reference power supply and higher than the reset voltage of the relay, so that the operation state of the relay contacts is reliably maintained, and The amount of heat generated from the coil is reduced as compared with the case where the exciting current is continuously supplied from the power supply.

The predetermined time is set to be a little longer than the time from the start of the supply of the exciting current to the coil to the activation of the relay contact, so that the relay contact operates reliably.

Further, in the relay driving circuit according to the first aspect, the low-voltage power supply outputs a voltage lower than the operating voltage of each of the relays.

According to this configuration, the amount of heat generated from the coil is further reduced by supplying the exciting current from the low-voltage power supply that outputs a voltage lower than the operating voltage of each relay.

Further, in the relay drive circuit according to claim 1 or 2, the stop control circuit includes a capacitor,
After being supplied with an exciting current by applying a voltage from the reference power supply to the coil, the applied voltage is reduced by a predetermined time constant. 3).

According to this configuration, the stop control circuit includes the capacitor and is incorporated in the reference voltage circuit. After the excitation current is supplied by applying a voltage from the reference power supply to the coil, the applied voltage decreases at a predetermined time constant. By doing so, a voltage higher than the operating voltage of the relay is applied to the coil for a predetermined time, so that the relay contacts operate reliably.

[0014]

FIG. 1 is a circuit diagram showing a first embodiment of a vehicle load control circuit to which the present invention is applied. This vehicle load control circuit includes an on-board battery (reference power source) 1
And loads 21, 22 such as lamps and door lock solenoids.
, And relays RL1, RL2,.
W1, SW2,..., Low-voltage power supply 3, and connection switching circuit 4
, 42,...
, 22, and so on.

Relays RL1, RL2,..., Low-voltage power supply 3
And the connection switching circuits 41, 42,... Are arranged inside an electric connection box (not shown) arranged at an appropriate place in the vehicle.

The relay RL1 comprises a relay contact RS1 provided between the vehicle-mounted battery 1 and the load 21, and a coil RC1 provided between the connection switching circuit 41 and the ground.

The operating voltage V _{S of} the relay, that is, the coil applied voltage at which the relay contact operates is about 7 to 8 V DC, and the return voltage V _{R of} the relay, that is, the coil applied voltage at which the relay contact returns to the original state is about 2 to 3 V DC. , The output voltage V _B of the vehicle-mounted battery 1 is higher than the operating voltage V _S (in this embodiment,
DC12V). In addition, connection switching circuits 41 and 4
2,... Have the same configuration.

The switch sections SW1 and SW2 are operation switches operated by the user of the vehicle, semiconductor switching elements which are turned on and off in accordance with the detection results of sensors (not shown), and one of the switch contacts is connected to the connection switching circuit 41, respectively.
The other is connected to the voltage output terminal of the vehicle-mounted battery 1.

The low-voltage power supply 3 is formed of switching power supply circuit comprising the DC-DC converter using an unillustrated switching transistor, the switching transistor the output voltage V _B of the in-vehicle battery 1 applied to the primary winding in switching, the voltage induced in the secondary winding is rectified, and outputs a voltage V _E is smoothed. In addition,
The output voltage V _E is set to _{(V B>) V S>} V E> V A _R, (5V in this embodiment) close to the release voltage V _R.

The connection switching circuit 41 includes a transistor Q11
, Diodes D11 and D12, and resistors R11 and R12
And a capacitor C11, and functions as a reference voltage circuit, a low voltage circuit, and a stop control circuit.

The collector of the transistor Q11 is connected to the voltage output terminal of the low-voltage power supply 3, and the base is connected to the resistor R11.
And the emitter is connected to the anode of the diode D11.

The cathode of the diode D11 is connected to a relay R
Connected to the coil RC1 of L1, connected to one contact of the switch SW1 via the capacitor C11, and further connected to the cathode of the diode D12.

The anode of the diode D12 is grounded, and one contact of the switch unit SW1 is connected to a resistor R1.
2 is grounded. Note that the diode D12
Is for bypassing the back electromotive force generated in the coil RC1 when the relay RL1 is turned off.

Next, the operation will be described with reference to FIG. FIG. 2 is a timing chart showing the state of each unit in the first embodiment. When the switch unit SW1 is turned on, firstly, the output voltage V _B of the in-vehicle battery 1 relay R
Since applied to the coil RC1 of L1, the applied voltage V _L to the coil RC1 becomes a voltage higher than the operating voltage V _S, the relay contacts RS1 is turned on.

[0025] At the same time, the base current is supplied to the transistor Q11 is turned on through the resistor R11, the anode voltage V _P of the diode D11 becomes equal to the output voltage V _E of the low-voltage power supply 3.

At this time, the inflow of current from the cathode side to the anode side of the diode D11 is prevented by the diode D11.

Next, the output voltage V _{B of the} vehicle battery 1
As the charging of the capacitor C11 proceeds, the voltage _VL applied to the coil RC1 decreases.
When 11 drops below the anode voltage V _P, the output voltage V _E of slightly higher than the release voltage V _R low-voltage power supply 3 is diode D1
1 will be applied to the coil RC1 via
The ON state of the relay contact RS1 is maintained.

When the switch SW1 is turned off,
By the charge stored in the capacitor C11 is charged voltage is discharged through the resistor R12 is decreased, when the transistor Q11 is applied voltage V _L of the coil RC1 is off falls below the return voltage V _R, Relay contact RS1
Turns off.

As described above, according to the first embodiment, in addition to the vehicle-mounted battery 1, the output voltage V
Less than _B, and includes a low voltage power supply 3 to output a slightly higher voltage V _E from the release voltage V _R of the relay, the coil of each relay, turns on the relay contact and applies the output voltage V _B of the in-vehicle battery 1 , The output voltage V _E of the low-voltage power supply 3
Since so as to apply a, it is possible to reliably operate the relay contacts, as compared to the case of continuing the application of the output voltage V _B of the in-vehicle battery 1, to reduce the amount of heat generated from the coil.

Further, by using a low-voltage power supply 3 having a small heat generation like a switching power supply circuit, the heat generation of the entire circuit can be reduced.

Further, by sharing a single low-voltage power supply 3 for driving a plurality of relays, the amount of heat generated can be reduced most.

FIG. 3 is a circuit diagram showing a second embodiment of a vehicle load control circuit to which the present invention is applied. The same components as those in the first embodiment are denoted by the same reference numerals. Second
In this embodiment, as shown in FIG. 3, the connection switching circuits 51, 5 are replaced with the connection switching circuits 41, 42,.
2, ... The connection switching circuits 51, 52,
... have a similar configuration.

The connection switching circuit 51 includes a transistor Q11
1, a diode D111, and resistors R111 to R113.
And a capacitor C111, and functions as a reference voltage circuit, a low voltage circuit, and a stop control circuit.

The collector of the transistor Q111 is connected to the voltage output terminal of the vehicle battery 1, the base is connected to the voltage output terminal of the vehicle battery 1 via the resistors R111 and R112, and the emitter is connected to the cathode of the diode D111. With the coil R of the relay RL1
It is connected to one end of C1. The anode of the diode D111 is connected to the voltage output terminal of the low-voltage power supply 3.

The connection point of the resistors R111 and R112 is connected to the other end of the coil RC1 of the relay RL1 and one contact of the switch SW1 via a resistor R113, and is grounded via a capacitor C111. The other contact of the switch section SW1 is grounded.

Next, the operation will be described with reference to FIG. FIG. 4 is a timing chart showing the state of each unit in the second embodiment. When the switch section SW1 is off, the transistor Q111 is connected to the resistors R112 and R111.
, And the base current is supplied to the capacitor C111, and the capacitor C111 is charged.

Therefore, one end of the coil RC1, ie, the emitter voltage V _{P of} the transistor Q111, the coil RC
As shown in FIG. 4, the voltage V _{Q at} the other end of the power supply 1 and the charging voltage V _C of the capacitor C 111 are all equal to the output voltage V _B of the vehicle-mounted battery 1, and therefore, are applied to the coil RC 1 of the relay RL 1. The voltage _VL is zero.

At this time, by the diode D111,
The inflow of current from the cathode side to the anode side of the diode D111 is prevented.

When the switch section SW1 is turned on, first,
Since the other end of the coil RC1 is grounded, the voltage V _Q drops to zero. On the other hand, the electric charge of the capacitor C111 is discharged through the resistor R113 and the switch unit SW1,
On between transistors Q111 charging voltage V _C decreases to a predetermined level continues.

Therefore, while the transistor Q111 is on, the voltage V _L applied to the coil RC1 of the relay RL1 is
By equal to the output voltage V _B is higher than the operating voltage V _S mounted battery 1, the relay contacts RS1 is turned on.

Next, when the charging voltage V _C decreases to a predetermined level and the transistor Q111 turns off, the relay R
Since the applied voltage V _L to L1 of the coil RC1 is equal to the output voltage V _E of the return voltage V slightly higher than _R low-voltage power supply 3, on the relay contacts RS1 is maintained.

[0042] When the switch unit SW1 is turned off, the voltage V _P, the voltage V _Q, the voltage V _C is the original level, that is, return the output voltage V _B of the in-vehicle battery 1, the relay contacts RS1 is turned off. At this time, the voltage is temporarily applied in the reverse direction by the back electromotive force generated in the coil RC1, as shown in FIG.

Note that the capacitance value of the capacitor C111 and the resistance value of the resistor R113 may be set so that the transistor Q111 is kept on only until the relay contact RS1 operates reliably.

As described above, according to the second embodiment, in addition to the vehicle-mounted battery 1, the output voltage V
Less than _B, and includes a low voltage power supply 3 to output a slightly higher voltage V _E from the release voltage V _R of the relay, the coil of the relay, the relay contacts on the applied output voltage V _B of the in-vehicle battery 1 after, since so as to apply the output voltage V _E of the low-voltage power supply 3, it is possible to obtain the same effect as the first embodiment.

The low-voltage power supply 3 may be provided inside a plurality of electric junction boxes in the vehicle and connected to a plurality of relays. Also, it may be arranged at one place in the vehicle and connected to all relays. In this case, the heat generation amount can be reduced most by sharing the single low-voltage power supply 3 for driving all the relays.

Further, the low-voltage power supply 3 may be shared as a power supply for 5 V system circuit components such as an electronic control unit. Thus, it is possible to suppress an increase in the number of components and to reduce the amount of heat generated.

The low-voltage power supply 3 outputs the output voltage V _E of 1
You may comprise using a secondary battery or a secondary battery. Also, 2
When a secondary battery is used, the secondary battery may be configured to be chargeable by the vehicle-mounted battery 1.

Although the present invention has been described in the embodiment applied to the vehicle load control circuit, the present invention is not limited to this.
The present invention may be applied to a general relay drive circuit.

[0049]

As described above, according to the present invention,
When a predetermined time elapses from the time when the relay contacts are activated by supplying the excitation current to the coil of each relay from the reference power supply that outputs a constant voltage higher than the operating voltage, the supply of the excitation current from the reference power supply is stopped, and then Since the excitation current is supplied from a low-voltage power supply that outputs a voltage lower than the constant voltage output from the reference power supply and higher than the return voltage of the relay, the operation state of the relay contacts can be reliably maintained. In addition, the amount of heat generated from the coil can be reduced as compared with the case where the excitation current is continuously supplied from the reference power supply.

Further, by supplying an exciting current from a low-voltage power supply that outputs a voltage lower than the operating voltage of each relay, the amount of heat generated from the coil can be further reduced.

The stop control circuit includes a capacitor and is incorporated in the reference voltage circuit. After the excitation current is supplied from the reference power supply to the coil by applying a voltage to the coil, the applied voltage is reduced by a predetermined time constant. With such a configuration, a voltage higher than the operating voltage of the relay is applied to the coil for a predetermined time, and the relay contact can be reliably operated.

[Brief description of the drawings]

FIG. 1 is a first view of a vehicle load control circuit to which the present invention is applied;
It is a circuit diagram showing an embodiment.

FIG. 2 is a timing chart showing a state of each unit in the first embodiment.

FIG. 3 is a second view of a vehicle load control circuit to which the present invention is applied;
It is a circuit diagram showing an embodiment.

FIG. 4 is a timing chart showing a state of each unit in the second embodiment.

FIG. 5 is a circuit diagram showing a conventional relay drive circuit.

[Explanation of symbols]

1 Battery (reference power supply) 21, 22, ... Load 3 Low voltage power supply 41, 42, ... Connection switching circuit (reference voltage circuit, low voltage circuit, stop control circuit) 51, 52, ... Connection switching circuit (reference voltage circuit, Low voltage circuit, stop control circuit) RL1, RL2, ... Relay RC1, RC2, ... Coil RS1, RS2, ... Relay contact SW1, SW2, ... Switch section

Claims (3)

[Claims] The relay contact is controlled by controlling an exciting current supplied to a coil of a relay having a relay contact between a reference power supply that outputs a constant voltage higher than an operation voltage of the relay and a plurality of loads. A low-voltage power supply that outputs a voltage lower than the fixed voltage and higher than the reset voltage of each relay, and supplies an exciting current to the coil of each relay from the reference power supply. A reference voltage circuit, a low-voltage circuit that supplies an exciting current to the coil of each relay from the low-voltage power supply, and a predetermined time that elapses from a point in time when the exciting current is supplied from the reference power supply and the relay contact is activated. And a stop control circuit for stopping the supply of the exciting current from a reference power supply. 2. The relay drive circuit according to claim 1, wherein said low-voltage power supply outputs a voltage lower than an operation voltage of each of said relays. 3. The relay drive circuit according to claim 1, wherein the stop control circuit includes a capacitor and is incorporated in the reference voltage circuit, and is configured to apply a voltage from the reference power supply to the coil. A relay drive circuit configured to reduce an applied voltage with a predetermined time constant after supplying an exciting current.