JPH1140028A - Relay driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of noise, and prevent generation of malfunction caused by an impact in a relay driving device to drive a relay for switching an electric circuit. SOLUTION: Generation of noise is restrained by connecting a fly wheel diode 11 of a short inverse recovery time in parallel with a relay coil 6b, and inserting a capacitor 13 between a base of a transistor and the ground. A relay driving device 5 having an excellent property against impact and short-circuit trouble is provided to prevent generation of malfunction caused by shock or the like by providing a full-ON period at the interval of fixed time to refresh a relay 6 in a PWM(pulse width modulation) circuit 7, conducting feedback control by a CPU 8 based on an output from the PWM circuit 7, and providing in two stages transistors 7a, 7b constituting the PWM circuit 7 in series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay driving apparatus for driving a relay for switching an electric circuit, and more particularly to a technique for suppressing the occurrence of noise and preventing the occurrence of a malfunction that may be caused by an impact.

[0002]

2. Description of the Related Art Heretofore, in a relay drive device which is built in an electric control unit (hereinafter referred to as an ECU) and drives a relay for switching various electric circuits, power is always supplied to a relay coil during driving.
For this reason, the heat generated in the relay coil is large, and there has been an inconvenience that peripheral elements of the relay are damaged by the heat generated. Also, it is necessary to avoid incorporating such a large heat-generating relay in a unit that is placed in a high-temperature environment and needs to suppress internal heat generation, such as an ECU mounted in an engine room of a vehicle. In addition, since the relay coil is always energized during driving, there is a problem that current consumption increases.

In order to solve these problems, pulse wide modulation (hereinafter, referred to as PWM) for controlling a relay by energizing a relay coil in a pulsed manner.
A controlled relay drive is provided. In this device, heat generation in the relay coil can be suppressed as compared with the above-described device in which the relay coil is always energized,
In addition, current consumption can be reduced.

[0004]

However, since the noise generated by the PWM control has a bad influence on the communication in the above-described conventional PWM control relay driving apparatus, the PWM control-based relay driving apparatus includes communication. It was difficult to use for the system. Also,
Since the relay coil is energized in pulses,
Since the contact pressure holding force of the coil is reduced and a malfunction such as a relay being turned off when subjected to an impact or the like may occur, the vibration may be applied to a unit such as an ECU mounted in an engine room of a vehicle. When this relay is built in, it has been difficult to ensure stable operation.

[0005] The present invention has been made to solve the above-mentioned problems, and suppresses heat generation from a relay coil.
By reducing current consumption and reducing noise, it can be used for systems including communication, and can prevent malfunction of relays that may occur due to impact, and is installed in the engine room of the vehicle. EC
It is an object of the present invention to provide a relay driving device capable of ensuring stable operation even in a unit to which vibration such as U is applied.

[0006]

In order to achieve the above object, the present invention relates to a relay driving device for driving a relay comprising a relay contact for switching an electric circuit and a relay coil, and a PWM for controlling energization of the relay coil. The flywheel diode includes a control circuit and a flywheel diode connected in parallel to a relay coil, and uses a flywheel diode having a short reverse recovery time. In this configuration, since the relay coil is energized by a pulse signal oscillated from the PWM control circuit, heat generation from the relay coil can be suppressed and current consumption can be reduced. Further, when the relay changes from the ON state to the OFF state, the time required for the reverse recovery current, which causes noise, to flow through the relay coil becomes shorter, so that noise can be reduced.

Further, the present invention provides a relay driving apparatus for driving a relay comprising a relay contact and a relay coil for switching an electric circuit, wherein a PWM control circuit for controlling energization of the relay coil and an output stage element of the PWM control circuit. It has a capacitor inserted between the base and the ground. In this configuration, since the relay coil is energized by a pulse signal oscillated from the PWM control circuit, heat generation from the relay coil can be suppressed and current consumption can be reduced. Further, noise generation is reduced by the capacitor.

The present invention also relates to a relay driving apparatus for driving a relay comprising a relay contact for switching an electric circuit and a relay coil, comprising a PWM control circuit for controlling energization of the relay coil, wherein the PWM control circuit is provided for a predetermined time. The relay is refreshed by providing a period during which the relay is turned on every time. In this configuration, since the relay coil is energized by a pulse signal oscillated from the PWM control circuit, heat generation from the relay coil can be suppressed and current consumption can be reduced. In addition, since the energization of the relay is turned on for a certain period of time at all times, the relay is refreshed and the contact pressure holding force of the relay coil is maintained. As a result, it is possible to prevent a malfunction such as a relay being turned off due to an impact.

Further, the present invention relates to a relay driving apparatus for driving a relay comprising a relay contact for switching an electric circuit and a relay coil, comprising a PWM control circuit for controlling energization of the relay coil, and a C control for controlling the PWM control circuit.
The output of the PWM control circuit is fed back to the PU. In this configuration, since the relay coil is energized by a pulse signal oscillated from the PWM control circuit, heat generation from the relay coil can be suppressed and current consumption can be reduced. Also, CPU
Performs feedback control while monitoring the output of the PWM control circuit, so that the output from the PWM control circuit can be stabilized and malfunction can be prevented.

According to the present invention, there is provided a relay driving device for driving a relay comprising a relay contact for switching an electric circuit and a relay coil, comprising a PWM control circuit for controlling energization of the relay coil, and an element constituting the PWM control circuit. Are provided in two stages in series for fail-safe. In this configuration, since the relay coil is energized by a pulse signal oscillated from the PWM control circuit, heat generation from the relay coil can be suppressed and current consumption can be reduced. Further, even if one of the elements constituting the PWM control circuit fails, the other element can control the energization of the relay coil.
This prevents a short circuit from occurring.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a processing system of a main part of a communication system of a vehicle including the relay drive device according to the present embodiment. The communication system of the vehicle 1 includes a column switch 2 disposed in a vehicle compartment and an ECU 3 disposed in an engine room. Further, in this communication system, the signal harness 4 between the column switch 2 and the ECU 3 is integrated into one, which is a communication system of a so-called single wire system (hereinafter, referred to as SWS). I have.

Output signals from a lamp switch, a wiper switch, a turn switch, and the like are converted into data by a communication IC in the column switch 2 and then transmitted to the ECU 3 via the signal harness 4 to be transmitted to the relay drive device 5 in the ECU 3. Drives the relay 6 based on the received signal, and performs ON / OFF operation of an electric circuit such as a lamp and a wiper.

FIG. 2 is a processing circuit diagram of the relay driving device built in the ECU 3. The relay driving device 5 includes a relay 6 including a relay contact 6a and a relay coil 6b for switching an electric circuit such as a lamp and a wiper, a PWM circuit 7 for controlling energization to the relay coil 6b, and a central processing unit 8 (hereinafter, CPU). ). Note that the PWM circuit 7 and the CPU 8 constitute a PWM control circuit of the present invention. A flywheel diode 11 having a short reverse recovery time is connected in parallel to the relay coil 6b, and a ground between a base of a transistor 12 (output stage element) for switching ON and OFF of the relay 6 and the ground. The capacitor 13 is inserted. In addition, PWM
The transistors (elements) 7a and 7b constituting the circuit 7
Two stages are provided in series. Further, the output value of the PWM circuit 7 is configured to be fed back to the CPU 8 via the check line 14, and the CPU 8 performs feedback control based on the output value. In addition, as shown in FIG. 3, the CPU 8 controls the PWM circuit 7 so that a pulse signal is output from the PWM circuit 7 at predetermined time intervals so that all the ON states continue for a predetermined time.

In the relay driving device 5 having the above-described configuration, the PWM circuit 7 outputs a PWM-controlled signal based on a command from the CPU 8 to turn on and off the transistor 12, thereby controlling the energization of the relay coil 6b. The contact 6a of the relay 6 switches the circuit. In this way, since the relay driving device 5 drives the relay 6 by PWM control, it is possible to suppress heat generation in the relay coil 6b as compared with the case where the relay coil 6b is always energized during driving.
As a result, adverse effects on peripheral elements are reduced, so that the relay driving device 5 can be built in a unit placed in a high-temperature environment such as the ECU 3 mounted in an engine room. Further, current consumption can be reduced as compared with the case where the relay coil 6b is always energized during driving. Further, the cost of the entire SWS system can be reduced.

In this relay driving device 5,
The flywheel diode 11 having a short reverse recovery time is connected in parallel to the relay coil 6b, so that when the relay changes from the ON state to the OFF state, the time required for the reverse recovery current, which causes noise, to flow through the relay coil 6b is short. And noise can be reduced. Further, since the capacitor 13 is inserted between the base of the transistor 12 and the ground, the noise voltage can be effectively released to the ground, and the noise can be reduced. As described above, by reducing the noise generated by the PWM control, it becomes possible to use the PWM-controlled relay driving device 5 in a system including communication.

Further, since the transistors (elements) 7a and 7b constituting the PWM circuit 7 are provided in two stages in series, for example, even if the transistor 7a fails, the transistor 7b controls the energization of the relay coil 6b. Can be done. As a result, it is possible to realize the relay driving device 5 that is strong against a short-circuit failure. Also, the CPU 8
Performs feedback control based on the output from the PWM circuit 7, so that the output from the PWM circuit 7 can be stabilized and malfunctions due to impact can be prevented. Further, a pulse signal is generated from the PWM circuit 7 such that the ON state continues for a predetermined period of time, so that the relay 6 is refreshed. Therefore, it is possible to prevent a reduction in the contact pressure holding force of the relay coil 6b. Thus, it is possible to prevent a malfunction that may occur due to an impact or the like. As described above, by realizing the relay driving device 5 that is strong against an impact or the like, the PW is mounted in a unit to which vibration is applied such as the ECU 3 mounted in the engine room of the vehicle.
Even in the case where the relay drive device 5 based on the M control is incorporated, stable operation can be ensured.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the relay driving device 5 described above, the CPU 8 and the transistors 7a, 7
b, etc., one relay 6
Is described, but a plurality of relays may be controlled simultaneously.

[0018]

As described above, according to the present invention, in the relay driving device for driving the relay, the energization of the relay coil is controlled by the PWM control circuit.
Heat generation from the relay coil can be suppressed. This makes it possible to incorporate the relay drive device in a unit placed in a high-temperature environment such as an ECU mounted in the engine room of the vehicle. In addition, current consumption can be reduced. Furthermore, since a flywheel diode having a short reverse recovery time is connected in parallel to the relay coil, it is possible to reduce the occurrence of noise that adversely affects communication, and it is possible to use this relay driving device in a system including communication.

Further, noise can be suppressed by inserting a capacitor between the base of the output stage element of the PWM control circuit and the ground.

In the PWM control circuit, the relay is refreshed by providing a period during which it is fully turned on at regular intervals, so that the contact pressure holding force of the relay coil can be maintained, and the relay is resistant to shocks and the like. A driving device can be realized. Thus, stable operation can be ensured even in a unit to which vibration is applied, such as an ECU mounted in the engine room of the vehicle.

Further, by performing feedback control of the output of the PWM control circuit, the output from the PWM control circuit can be stabilized, and a malfunction that can occur due to an impact or the like can be prevented. A stable operation can be ensured even in a unit to which vibration is applied such as an ECU.

Further, by providing two elements constituting the PWM control circuit in series, even if one element fails,
The energization control to the relay coil can be performed by the other element, and a relay driving device resistant to short-circuit failure can be realized. Thus, stable operation can be ensured even in a unit to which vibration is applied, such as an ECU mounted in the engine room of the vehicle.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a processing system of a main part of a communication system of a vehicle including a relay driving device according to an embodiment of the present invention.

FIG. 2 is a processing circuit diagram of a relay driving device built in an ECU.

FIG. 3 is a time chart showing a pulse signal output from a PWM circuit.

[Explanation of symbols]

 Reference Signs List 5 relay drive device 6 relay 6a relay contact 6b relay coil 7 PWM circuit (PWM control circuit) 7a, 7b transistor (element) 8 CPU 11 flywheel diode 12 transistor (output stage element) 13 capacitor

Claims (5)

[Claims] 1. A relay driving device for driving a relay comprising a relay contact and a relay coil for switching an electric circuit, a PWM control circuit for controlling energization of the relay coil, and a flywheel connected in parallel to the relay coil A relay driving device comprising: a diode having a short reverse recovery time as the flywheel diode. 2. A relay driving device for driving a relay including a relay contact and a relay coil for switching an electric circuit, comprising: a PWM control circuit for controlling energization of the relay coil; and a base of an output stage element of the PWM control circuit. A relay driving device comprising: a capacitor inserted between grounds. 3. A relay drive device for driving a relay comprising a relay contact and a relay coil for switching an electric circuit, comprising: a PWM control circuit for controlling energization of the relay coil, wherein the PWM control circuit is provided at regular intervals. A relay driving device characterized in that the relay is refreshed by providing a period during which all the relays are turned on. 4. A relay drive device for driving a relay comprising a relay contact and a relay coil for switching an electric circuit, comprising: a PWM control circuit for controlling energization of the relay coil; and a CPU for controlling the PWM control circuit. A relay driving device wherein an output of a control circuit is fed back. 5. A relay driving device for driving a relay comprising a relay contact for switching an electric circuit and a relay coil, comprising: a PWM control circuit for controlling energization of the relay coil, wherein an element constituting the PWM control circuit fails. A relay drive device comprising two stages provided in series for safety.