JP5799793B2 - Power relay circuit for vehicles - Google Patents

Description

  The present invention relates to a vehicle power relay circuit that reliably opens a relay contact provided between a battery and a load when the battery is removed.

  Conventionally, the connection from the battery of the vehicle to the load has been switched between current flow and interruption by a normally open relay. The normal open relay acts as a reverse connection protection element in which no current flows when a battery is connected in reverse, no matter what load is connected.

  Power consumption can be reduced by using a latching relay instead of the normally open relay for connection from the battery of the vehicle to the load. In Patent Document 1, when a battery is reversely connected, a current is passed through a contact-off coil, and a latching relay (relay contact) is turned off (opened) so that a latching relay is a reverse connection protection element. A connection prevention circuit is described.

  In the reverse connection prevention circuit described in Patent Document 1, two circuits are connected in parallel between the cathode of the first diode whose anode is connected to the battery and the ground. The first circuit is a series circuit of a contact-off coil, a second diode connected in series, and a contact-off switch (reset switch). The second circuit is a contact-on coil and a contact-on switch (set). Switch) series circuit. Further, a third diode is reversely connected between the battery and the anode of the second diode, and a fourth diode is reversely connected in parallel with the contact-on coil.

  In this reverse connection prevention circuit, when the battery is connected in reverse, the current flows through the path of the positive electrode of the battery, the parasitic diode of the switch for contact ON, the fourth diode, the coil for contact OFF, and the third diode. Turn off the contact.

  However, when the load is a motor or an inductance load, a flywheel diode is often set in the load circuit, and when a battery is reversely connected to such a circuit, a large current flows through the flywheel diode and is connected. There is a possibility that the load including the connected electric wire has a low resistance and the required voltage is not applied to the contact-off coil. For this reason, it is inevitable that the flywheel diode is not set in the load circuit.

JP 2011-135633 A

  When a latching relay is used instead of the normally open relay for connection from the vehicle battery to the load, the latching relay maintains the state when it is removed when the battery is removed. For this reason, if the relay contact is closed when the battery is removed, if the reverse connection is mistaken when connecting the battery again, the current will flow to the load, and even if the fuse is set, before the fuse blows There is a problem that the load or the like may be damaged. The reverse connection prevention circuit described in Patent Document 1 does not sufficiently solve this problem.

  The present invention has been made in view of such circumstances, and provides a vehicle power relay circuit that reliably opens a relay contact provided between a battery and a load when the battery is removed. For the purpose.

The vehicle power relay circuit according to the present invention includes a latching relay in which a relay contact is provided between a positive electrode of a battery and a load, and the latching relay has the relay contact opened when current is passed. In a vehicle power relay circuit comprising a semiconductor switch provided between a coil and the positive electrode, the positive electrode side terminal of the semiconductor switch, and a capacitor connected between a fixed potential lower than the potential of the positive electrode, The positive electrode and a diode connected in series between the positive electrode side terminal of the semiconductor switch, and provided between the positive electrode and the control terminal of the semiconductor switch, when the current from the battery is not flowing, and a switching circuit for switching the semiconductor switches closed, the semiconductor switch, one terminal of the coil connected to the drain A P-channel FET whose source is connected to the cathode of the diode and whose gate is supplied with the output voltage of the switching circuit. In the switching circuit, a diode and a resistor are connected in series between the positive electrode and a fixed potential. It is, the diode is forward connected, characterized that you have resistance between the gate of the cathode and the semiconductor switch of the diode is connected.

In the vehicle power relay circuit according to the present invention, when electric power is supplied from the battery to the load, the electric power of the battery is also supplied to the capacitor through the diode and stored. When the battery is removed, the switching circuit switches the semiconductor switch closed, the discharge current from the capacitor flows through the coil, and the relay contact is switched open. The discharge current from the capacitor does not flow to the load side by the diode.
In this vehicle power relay circuit, since the gate of the P-channel FET connected between the coil and the battery is grounded through two resistors, the P-channel FET is not connected when the battery is removed. Always be switched to closed. As a result, a discharge current flows from the capacitor to the coil through the P-channel FET, and the relay contact is switched to open.

  ADVANTAGE OF THE INVENTION According to this invention, the power supply relay circuit for vehicles which opens reliably the relay contact provided between the battery and load when a battery is removed is realizable.

1 is a circuit diagram showing an embodiment of a power relay circuit for a vehicle according to the present invention. It is explanatory drawing which shows the example of the operation | movement which the electric current from a battery flows into the coil for contact ON. It is explanatory drawing which shows the example of the operation | movement through which the electric current from a battery flows into the coil for contact OFF. It is explanatory drawing which shows the example of the operation | movement by which an electric current flows into the coil for a contact OFF when a battery is removed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a circuit diagram showing a configuration of an embodiment of a power relay circuit for a vehicle according to the present invention. 1 is connected to a battery 9 and a load group 8, and includes a latching relay 1, a capacitor 7, a switching circuit 6, a low-side driver 2, a contact-on switch 42, a resistor 62, and a contact-off switch. 43, a diode 52, and a diode 53.
The contact ON switch 42 and the contact OFF switch (semiconductor switch) 43 are P-channel FETs.

  The latching relay 1 includes a relay contact 11, a contact-on coil 12, and a contact-off coil 13. The switching circuit 6 includes a resistor 63, a resistor 64, and a diode 54. The load group 8 includes a plurality of loads 8a, 8b, and 8c. The low side driver 2 includes a CPU 21, a switch 22, and a switch 23. The switches 22 and 23 are N-channel FETs.

  The relay contact 11 is connected between the positive electrode of the battery 9 and each load included in the load group 8. One terminal of each of the contact-on coil 12 and the contact-off coil 13 is grounded.

The other terminal of the contact-on coil 12 is connected to the drain of the contact-on switch 42, and the gate of the contact-on switch 42 is connected to the drain of the switch 22. A diode 52 is connected in series between the source of the contact-on switch 42 and the positive electrode of the battery 9. A resistor 62 is connected between the source and gate of the contact-on switch 42.
The switch 22 has a source grounded and a gate connected to the contact-on output terminal of the CPU 21.

  The other terminal of the contact-off coil 13 is connected to the drain of the contact-off switch 43. A diode 53 is connected in series between the source of the contact-off switch 43 and the positive electrode of the battery 9. One terminal of the capacitor 7 is connected to the cathode of the diode 53, and the other terminal of the capacitor 7 is grounded.

The gate of the contact-off switch 43 is connected to one terminal of the resistor 63, and a diode 54 is connected in series between the other terminal of the resistor 63 and the positive electrode of the battery 9. The resistor 64 has one terminal connected to the cathode of the diode 54 and the other terminal grounded.
The switch 23 has a drain connected to the gate of the contact-off switch 43, a source grounded, and a gate connected to the contact-off output terminal of the CPU 21.

  The relay contact 11 is closed when a current flows through the contact-on coil 12 and is opened when a current flows through the contact-off coil 13. When the current flow from the battery 9 is stopped, the relay contact 11 is kept in the state when it is stopped.

  Below, the example of operation | movement of the power relay circuit for vehicles of such a structure is demonstrated.

  FIG. 2 is an explanatory diagram illustrating an example of an operation in which a current from the battery 9 flows through the contact-on coil 12. In FIG. 2, the CPU 21 closes the switch 22 for a short time, whereby the contact-on switch 42 is closed for a short time. As a result, as indicated by a thin broken line arrow in the figure, current flows for a short time from the battery 9 in the order of the diode 52, the contact-on switch 42, and the contact-on coil 12, and the relay contact 11 is closed. . When the relay contact 11 is switched to the closed state, a current flows from the battery 9 to the load group 8 as indicated by a thick broken line arrow in the figure.

  At this time, because the CPU 21 opens the switch 23, the contact-off switch 43 is opened, and the electric power supplied from the battery 9 through the diode 53 is stored in the capacitor 7.

  FIG. 3 is an explanatory diagram illustrating an example of an operation in which the current from the battery 9 flows through the contact-off coil 13. In FIG. 3, when the CPU 21 closes the switch 23 for a short time, the contact-off switch 43 is closed for a short time. On the other hand, since the switch 22 is open, the contact-on switch 42 is open. As a result, as indicated by the thin broken line arrow in the figure, the current flows for a short time from the battery 9 in the order of the diode 53, the contact-off switch 43, and the contact-off coil 13, and the relay contact 11 is opened. To do. By switching the relay contact 11 to open, the current from the battery 9 to the load group 8 is interrupted.

  At this time, similarly to FIG. 2, the power supplied from the battery 9 is stored in the capacitor 7.

  FIG. 4 is an explanatory diagram illustrating an example of an operation in which a current flows through the contact-off coil 13 when the battery 9 is removed. In FIG. 4, since the battery 9 is removed, no current flows through the contact-on coil 12. The switch 23 is open, but the gate of the contact-off switch 43 is grounded through the resistor 63 and the resistor 64. Therefore, while the electric power stored in the capacitor 7 is discharged, a potential difference is generated between the source and gate of the contact-off switch 43, and the contact-off switch 43 is closed. Thereby, as indicated by a thin broken line arrow in the figure, when the electric power stored in the capacitor 7 flows to the contact-off coil 13 through the contact-off switch 43 and the relay contact 11 is closed, Switch to open. If the relay contact 11 is open, it remains open.

  When the battery 9 is removed, the current always flows through the contact-off coil 13 and the relay contact 11 is opened. Therefore, even if the battery 9 is connected again, There is no possibility that a large current flows through the load group 8 and the short circuit including the load group 8.

  In the embodiment described above, the relay contact 11 is the a contact, the contact on coil 12 is the set coil, and the contact off coil is the reset coil. However, the relay contact 11 is the b contact. May be. In that case, the contact-on coil 12 is a reset coil, and the contact-off coil 13 is a set coil.

  As mentioned above, although the form for inventing was demonstrated, this invention is not limited to embodiment described in the form for implementing this invention. Modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Latching relay 2 Low side driver 6 Switching circuit 7 Capacitor 8 Load group 9 Battery 11 Relay contact 12 Contact-on coil 13 Contact-off coil 21 CPU
22, 23 Switch 42 Contact ON switch 43 Contact OFF switch (semiconductor switch)
52, 53, 54 Diode 62, 63, 64 Resistance 8a, 8b, 8c Load

Claims (1)

A latching relay provided with a relay contact between the positive electrode of the battery and a load, and a semiconductor provided between the positive electrode of the latch and the coil that opens the relay contact when current is passed and the positive electrode In a vehicle power relay circuit comprising a switch,
A capacitor connected between the positive terminal of the semiconductor switch and a fixed potential lower than the potential of the positive electrode;
A diode connected in series between the positive electrode and the positive terminal of the semiconductor switch ;
A switching circuit provided between the positive electrode and the control terminal of the semiconductor switch, and when the current from the battery is not flowing, the switching circuit for switching the semiconductor switch to close ;
The semiconductor switch is a P-channel FET in which one terminal of the coil is connected to the drain, the cathode of the diode is connected to the source, and the output voltage of the switching circuit is applied to the gate.
The switching circuit is
Wherein between the positive electrode and a fixed potential, the diode and the resistor are connected in series, the diode is forward connected, the vehicle characterized that you have resistance between the gate of the cathode and the semiconductor switch of the diode is connected Power supply relay circuit.

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