JP2013211959A - In-vehicle power-supply circuit and in-vehicle power-supply unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform appropriate circuit protection without reduction in power efficiency.SOLUTION: An in-vehicle power-supply circuit includes: a storage battery 6; a fuse 7 connected to the storage battery 6; a series connection body 11 connected to the fuse 7 and composed of a choke coil 9 and a switching element 10; a rectifier smoothing circuit 12 connected between the choke coil 9 and the switching element 10; an output terminal 13 connected to the rectifier smoothing circuit 12; and a control circuit 19 controlling the switching element 10. When a negative electrode of the storage battery 6 is connected to the fuse 7 side, the fuse 7 is disconnected by a diode 21, the choke coil 9, and the fuse 7 being energize by series connection, so that the choke coil 9, the switching element 10, and the control circuit 19, and a rectifier circuit are protected.

Description

  The present invention relates to an in-vehicle power supply circuit for protecting a circuit from reverse connection or erroneous connection of a storage battery in an in-vehicle power supply circuit, and an in-vehicle power supply unit using the same.

  As shown in the connection diagram of the electronic circuit in FIG. 3, the power supply circuit in the conventional in-vehicle application has a diode 3 connected between the storage battery 1 and the electronic control unit 2, for example, and a load 4 on the output side of the electronic control unit 2. And the anode side of the diode 3 is connected to the positive electrode side of the storage battery 1.

  In general, when the output of the storage battery 1 cannot be obtained sufficiently due to being used for a long period of time or the like, the normal operation of the electronic circuit 5 is maintained by replacing it with a new storage battery 1. To do. Therefore, when the storage battery 1 is replaced, the connection of the storage battery 1 to the electronic circuit 5 may be mistakenly connected in the reverse direction. The entire electronic circuit 5 or the electronic control unit 2 is protected by this operation of interrupting the current that flows in the direction opposite to the original direction of the current that flows when the normal polarity connection is performed.

  For example, Patent Document 1 is known as prior art document information relating to the invention of this application.

JP 2009-1000051 A

  However, in the conventional protection circuit, when power is supplied from the storage battery 1 in the forward direction, that is, when a normal polarity connection is made, power loss due to a potential drop of about 0.7 (V) is always caused in the diode 3. Therefore, particularly in the case of a device that requires a large current for in-vehicle use, a large current is required to be supplied, so that a reduction in power efficiency as a power source cannot be avoided.

  Accordingly, an object of the present invention is to provide appropriate circuit protection without reducing power efficiency.

  And in order to achieve this object, the in-vehicle power supply circuit of the present invention includes a storage battery, a fuse connected to the storage battery, a series connection body including a choke coil and a switching element connected to the fuse, A rectifying / smoothing circuit connected to a connection point between the choke coil and the switching element; an output terminal connected to the rectifying / smoothing circuit; and a control circuit for controlling the switching element. A diode connected between the drain and source of the element is formed with a connection side to the choke coil as a cathode side, and when the negative electrode of the storage battery is connected to the fuse side, the diode, the choke coil, The fuse is disconnected when the fuse and the energized state are connected in series, and the series connection is performed. Is obtained is characterized in that the body and the rectifying smoothing circuit and said control circuit is protected.

  According to the present invention, the power loss in the normal state of normal connection in which the positive electrode of the storage battery is connected to the fuse side is suppressed, and in particular, the reverse voltage of the power supply circuit when the storage battery is erroneously connected. This makes it possible to protect vulnerable control units and control elements.

The circuit block diagram of the vehicle-mounted power supply circuit of one Embodiment of this invention The block diagram of the vehicle-mounted power supply unit of one Embodiment of this invention Block diagram of a conventional power circuit

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a circuit block diagram showing a configuration of a power supply circuit according to an embodiment of the present invention. The electrode 6a on one side of the storage battery 6 is connected to one end side of the fuse 7. The other end side of the fuse 7 is connected to an electrolytic capacitor 8 and a choke coil 9 provided in parallel to the electrolytic capacitor 8 and switching. A series connection body 11 composed of the element 10 is connected. A rectifying / smoothing circuit 12 is connected to a connection point between the choke coil 9 and the switching element 10, and a DC voltage is applied from the output terminal 13 connected to the rectifying / smoothing circuit 12 to the load 14. It has become.

  Here, the rectifying / smoothing circuit 12 includes a rectifying diode 15 having an anode connected to a connection point between the choke coil 9 and the switching element 10, and a smoothing capacitor 16 provided in parallel with the load 14 on the cathode side of the rectifying diode 15. And is composed of.

  In addition, when this power supply circuit is applied to an on-vehicle application, a portion between the input terminal 17 and the output terminal 13 serving as a connection point between the fuse 7 and the electrolytic capacitor 8 performs a function corresponding to the power supply function unit 18. Become. Here, the supply of electric power to the load 14, that is, the connection between the output terminal 13 and the load 14 is appropriately performed as necessary.

  A control circuit 19 is connected to the switching element 10 and controls the output voltage or output current. Alternatively, the control circuit 19 may be controlled to be turned ON / OFF by giving an ON / OFF signal to the control terminal 20 provided in the power function unit 18.

  The switching element 10 is provided with a diode 21 connected between the drain and source of the switching element 10 with the connection side to the choke coil 9 on the drain side as the cathode side and the ground side on the source side as the anode side. . Alternatively, the switching element 10 having the diode 21 parasitic between the drain and the source is provided with the connection side to the choke coil 9 as the cathode side on the drain side and the ground side as the anode side on the source side. The diode 21 may be either a parasitic diode that is formed when a field effect transistor is used as the switching element 10 or one that is connected to the outside of the switching element 10.

  Next, the operation of this power supply circuit will be described. When the positive electrode of the storage battery 6 is connected to the electrode 6 a on one side of the storage battery 6, that is, when connection is made in a normal state, the energy supplied from the storage battery 6 is applied to the choke coil 9. The voltage is converted by the switching operation of the switching element 10, and when the output terminal 13 and the load 14 are connected, a DC voltage is applied to the load 14 through the rectifying and smoothing circuit 12.

  On the other hand, there is a possibility that the storage battery 6 is replaced relatively frequently as in a vehicle, and there is a possibility that the connection is mistaken at the time of replacement, and the connection of the storage battery 6 to the electrode 6a on one side of the storage battery 6 is erroneously made. The operation when the negative electrode is connected will be described. Here, when the negative electrode of the storage battery 6 is connected to the electrode 6a on one side of the storage battery 6, the direct current consisting of the storage battery 6, the fuse 7, the choke coil 9 and the diode 21 is closed as the current flowing through the entire power supply circuit. A circuit is formed, that is, when a forward bias is applied to the diode 21, a current flows from A → B → C → D → E → F → G → H from the direction of higher potential. Become. Since a large amount of energy is supplied from the storage battery 6 to this closed circuit that is in a short circuit state with respect to the direct current, a large current flows instantaneously. In response to this, the fuse 7 reacts to interrupt the circuit, thereby releasing the short circuit state.

  Even if the direction of the electrodes in the connection of the storage battery 6 is wrong due to the above configuration and the operation corresponding thereto, it is downstream from the fuse 7 including the electrolytic capacitor 8, the smoothing capacitor 16, the switching element 10, and the control circuit 19. A reverse voltage at a level that destroys these circuits or devices is not applied to the circuit or device connected to the side, and naturally the power does not leak to the outside through the control terminal 20. Therefore, the control circuit 19 of the power supply function unit 18 and the electrolytic capacitor 8 and the smoothing capacitor 16 having characteristics that are vulnerable to the reverse voltage are in a protected form even when the storage battery 6 is reversely connected. Can be maintained.

  This is because when a normal connection of the storage battery 6 is performed, it is possible to eliminate an element in which a diode or the like accompanied by a loss of power at all times is arranged in series, so that the loss can be suppressed. At the same time, even if the connection of the storage battery 6 is wrong, it is possible to cope with recovery by replacing the fuse 7 which can be easily replaced.

  In addition, as described above, the diode 21 may be a parasitic diode that is equivalently formed when a field effect transistor is used as the switching element 10 or is connected to the outside of the switching element 10. Any of them may be used. Whether to select the diode 21 as a parasitic diode or an external connection may be selected on the basis of the allowable amount for the current value that flows at the time of a short circuit, but when the parasitic diode of the switching element 10 is applied, There is no need to add countermeasure parts for reverse connection of the storage battery 6, which is effective in that the number of parts can be reduced and the cost can be reduced.

  Furthermore, when the diode 21, the choke coil 9, and the fuse 7 are connected in series, the current capacity of the conductor portions 22, 23, 24, 25, the current capacity of the diode 21, and the current capacity of the choke coil 9 It is desirable to make all of these larger than the current capacity of the fuse 7. Here, the current capacity refers to an allowable amount until a conductor or device is broken or melted due to its own heat generation or the like when a large value of current flows. As a result, even if the direction of the electrodes in the connection of the storage battery 6 is wrong, when an overcurrent occurs from A → B → C → D → E → F → G → H, individual devices or those The operation of cutting the fuse 7 is performed until the conductor connecting the two is damaged. That is, even if the connection of the storage battery 6 is wrong, the response associated with it can be dealt with only by replacing the fuse 7 that can be easily replaced.

  Here, the current limit value of the fuse 7 may be applied when the storage battery 6 is in a normal connection state. When the storage battery 6 is normally connected and the entire circuit functions as a normal operation, the operation is always performed with the load 14 connected. Therefore, the current flowing through the circuit, that is, the current passing through the fuse 7 is smaller during normal operation than during short-circuiting with the storage battery 6 connected in reverse polarity. If the current limit value of the fuse 7 is determined based on the normal operation, it is set in a safe direction. Therefore, the current limit value of the fuse 7 is based on the case where the storage battery 6 is in a normal connection state. This will not adversely affect other devices.

  The description so far has been limited to the power supply circuit. However, as a matter of course, the power supply circuit 26 and the electronic control unit 27 connected to the storage battery 6 and the load 14 are integrated as shown in the block diagram of the in-vehicle power supply unit in FIG. It may be used as a vehicle-mounted power supply unit 28. Here, the power supply circuit 26 includes the fuse 7 and the power supply function unit 18 shown in FIG. In FIG. 2, the electronic control unit 27 is mounted on the in-vehicle power supply unit 28. However, the electronic control unit 27 is not limited to the electronic control unit 27. It does not matter. Even when the storage battery 6 is reversely connected by connecting the electronic control unit 27 shown in FIG. 2 downstream of the fuse 7 to the downstream side of the power supply circuit 26, that is, the storage battery 6 shown in FIG. The influence on the electronic control unit 27 can be completely eliminated. Therefore, a protection device (not shown) against the reverse voltage is not required for the electronic control unit 27, and not only the size of the in-vehicle power supply unit 28 can be reduced but also the cost can be reduced. In this case, in addition to the electronic control unit 27, another electronic unit (not shown) or an electronic device (not shown) is mounted on the in-vehicle power supply unit 28. It is possible to provide a protection function for the constituent elements, and as described above, not only can the size be reduced by suppressing the number of parts, but also the effect of cost reduction can be further increased.

  At the same time, the above effect is the same for the load 14 connected to the downstream side of the fuse 7 shown in FIG. 1. Generally, a plurality of power supplies 26 are connected in parallel as shown in FIG. Since the load 14 connected to the power supply circuit 26 is also on the downstream side of the power supply circuit 26, a protection device (not shown) against the reverse voltage is not required, and not only miniaturization by suppressing the number of parts in each load 14 but also the cost is reduced. Reduction is also possible.

  The in-vehicle power supply circuit of the present invention and the in-vehicle power supply unit using the same have the effect of improving the power efficiency during normal operation and protecting the circuit elements even if the polarity during connection of the storage battery is incorrect. It is useful in the operation when mounted on.

DESCRIPTION OF SYMBOLS 6 Storage battery 6a Electrode 7 Fuse 8 Electrolytic capacitor 9 Choke coil 10 Switching element 11 Series connection body 12 Rectification smoothing circuit 13 Output terminal 14 Load 15 Rectification diode 16 Smoothing capacitor 17 Input terminal 18 Power supply function part 19 Control circuit 20 Control terminal 21 Diode 22 , 23, 24, 25 Conductor part 26 Power supply circuit 27 Electronic control unit 28 In-vehicle power supply unit

Claims (4)

A storage battery,
A fuse connected to this storage battery,
A series connection body composed of a choke coil and a switching element connected to the fuse,
A rectifying and smoothing circuit connected to a connection point between the choke coil and the switching element;
An output terminal connected to the rectifying and smoothing circuit;
A control circuit for controlling the switching element,
In the switching element, a diode connected between the drain and source of the switching element is formed with a connection side with the choke coil as a cathode side,
When the negative electrode of the storage battery is connected to the fuse side,
The fuse is cut by energizing the diode, the choke coil, and the fuse in series connection,
A vehicle-mounted power supply circuit in which the series connection body, the rectifying / smoothing circuit, and the control circuit are protected. The in-vehicle power supply circuit according to claim 1, wherein the diode is provided parasitic to the switching element. When a forward bias voltage is applied to the diode, when the diode, the choke coil, and the fuse are connected in series, the conductor portion that connects them, the diode, and the current capacity against the fusing of the choke coil are changed to the fuse. The in-vehicle power supply circuit according to claim 1, wherein the power supply circuit is larger than the in-vehicle power supply circuit. The in-vehicle power supply circuit according to any one of claims 1 to 3,
An in-vehicle power supply unit integrated with an electronic device to which power is supplied from the in-vehicle power supply circuit.

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