JPH10116552A - Switching device - Google Patents

Abstract

(57) [Problem] To provide a switching device capable of preventing a load from being damaged due to a short circuit of a semiconductor switch at the time of short circuit. When a current of a predetermined value or more flows in a conductor path electrically connecting a power supply unit and a semiconductor switch or a conductor path electrically connecting a semiconductor switch and a load. Is provided with a disconnecting means 21 for disconnecting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching device, and more particularly to an intelligent power switch (IPS).
The present invention can be applied to a switching device having an overcurrent or overheat protection function called a so-called overcurrent protection function.

[0002]

2. Description of the Related Art Conventionally, a vehicle is equipped with a large number of switching devices for selectively supplying power to loads such as lights and motors. This switching device is provided in an electric junction box generally called a junction box.

FIG. 4 shows a schematic configuration using an electromagnetic relay 1 of the switching device.
The power supply unit 2 and the load 3 (the lamp in the case of the figure) are electrically connected via the power supply unit 2. The electromagnetic relay 1 is controlled to be closed or opened in accordance with the on / off state of the operation switch 4. When the electromagnetic relay 1 is controlled to be closed, the power of the power supply unit 2 is supplied to the load 3.

Usually, a fuse 5 is provided between the power supply unit 2 and the electromagnetic relay 1. As a result, for example, when a load short circuit or the like occurs, the fuse 5 is blown, thereby preventing an overcurrent to the load 3 and preventing the load 3 from being damaged due to the short circuit.

[0005]

By the way, with the advance of semiconductor manufacturing technology in recent years, a semiconductor switch having good performance and low cost has been easily obtained, and thus the electromagnetic relay 1 has been replaced with the electromagnetic relay 1 described above. Thus, a switching device using a semiconductor switch has been proposed.

Among switching devices of this type, those having a self-protection function of protecting a semiconductor switch from overcurrent or overheating are intelligent power switches (IP).
This is called S), and when a current exceeding the rated current flows through the semiconductor switch or when the temperature of the semiconductor switch rises to a specified temperature or more, the semiconductor switch is forcibly turned off to prevent damage to the semiconductor switch. It has been made to be.

FIG. 5 shows a configuration of a general IPS. I
The PS10 has a one-chip configuration, and has a power input terminal T
1, a power supply output terminal T2, a ground terminal T3, a diagnostic terminal T4, and a control signal input terminal T5.

The IPS 10 is connected to a power supply 11 such as a battery and the drain of a power MOS FET 12 via a power supply input terminal T1, and the power MOS F
The source of the ET 12 is connected to the load 13 via the power output terminal T2.
It is connected to the. A very small resistance R1 having a very small resistance such as a shunt resistance is provided between the source of the power MOS FET 12 and the power supply output terminal T2, and the voltage across the very small resistance R1 is sent to the control unit 14.

The control section 14 comprises a comparator, a logic circuit and the like. That is, the control unit 14 provides the comparator with the voltage value across the minute resistor R1 and the power MOS FE
A reference voltage value corresponding to the rated current of T12 is input, and when the voltage value across the small resistor R1 is greater than the reference voltage value, a positive logic fault indicating that an overcurrent is flowing from the comparator to the power MOSFET 12 is output. Current detection signal S
2 is output. Then, the logic value of the overcurrent detection signal S2 from the comparator and the switching control signal S1 input via the control signal input terminal T5 is input to, for example, a logical AND circuit.

Accordingly, the control unit 14 indicates that the logic value of the switching control signal S1 controls the power MOSFET 12 to be turned on, and the overcurrent detection signal S2
The charge pump 15 is driven and the power MOS FE is driven only when the logical value of
A voltage necessary for the power MOSFET 12 to turn on is applied to the gate of T12. On the other hand, the logic value of the switching control signal S1 is the power MOS FET
Even if it indicates that the 12 is to be turned on,
When the logical value of the overcurrent detection signal S2 indicates an overcurrent, the charge pump 15 is not driven and the power M
The OS FET 12 is turned off.

Thus, in the IPS 10, for example, when a load short circuit or the like occurs, an overcurrent based on the short circuit can be detected and the power MOS FET 12 can be turned off, thereby preventing damage to the power MOS FET 12 and damage to the load 13. can do. Although the IPS 10 of FIG. 5 has been described as having only the overcurrent protection function, the IPS 10 may have the overheat protection function.

Incidentally, the overcurrent detection signal S2 is sent to the microcomputer 16 via the diagnosis terminal T4, and the microcomputer (microcomputer) 16 detects the overcurrent detection signal S2 if it is a signal indicating an overcurrent. Abnormal signal S shown
3 is sent to the abnormality display section. Also, an operation signal S1 from an operation unit corresponding to the load 13 is input to the microcomputer 16,
The operation signal S1 is provided to the control signal input terminal T5 as the switching control signal S1. 17 is power M
4 shows a parasitic diode capacitance of the OS FET 12.

In the IPS 10, the load 1
Depending on the three types (for example, those provided on a power supply line for supplying power to a power window motor), the power MOSFET 12 is frequently turned on and off, thereby deteriorating the power MOSFET 12 and, in the worst case, the power MOSFET 12. May be short-circuited. Here, in the IPS 10, in addition to the on / off by the switching control signal S1, the on / off by the overcurrent protection and the on / off by the overheat protection are added, so that the number of times of the on / off is further increased, and the danger of a short circuit is considered to increase.

If the power MOS FET 12 is short-circuited, not only is it impossible to supply desired power, but if the power MOS FET 12 is short-circuited when the load is short-circuited, a large current flows through the load 13 and the load 13 is damaged.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a switching device using a semiconductor switch, which can prevent a load from being damaged due to a short circuit of the semiconductor switch in the event of a short circuit. Is what you do.

[0016]

According to a first aspect of the present invention, there is provided a switching device comprising: a semiconductor switch provided between a power supply unit and a load; When the semiconductor switch is overheated and / or outputs a control signal for turning off the semiconductor switch to a control signal input terminal of the semiconductor switch, the semiconductor switch is prevented from overcurrent and / or overheating. In a switching device having a protection circuit for protecting, a current equal to or more than a predetermined value is supplied to a conductor path electrically connecting a power supply unit and a semiconductor switch or a conductor path electrically connecting a semiconductor switch to a load. Disconnection means for disconnecting when flowing is provided.

In the above configuration, if the semiconductor switch is short-circuited when the electric wire or the load is short-circuited, the overcurrent protection function of the protection circuit does not work, so that a current of a predetermined value or more flows through the conductor path. At this time, the disconnection of the disconnection means interrupts the overcurrent due to the short circuit. As a result, the overcurrent due to the short circuit is not supplied to the electric wire or the load, thereby preventing the smoke or the load from being damaged.

In the switching device according to the present invention, the breaking characteristic of the protection circuit is set smaller than the smoke emission characteristic of the electric wire connecting the switching device and the load, and the disconnection means is used as the disconnection means. The one whose characteristics are larger than the cutoff characteristics of the protection circuit and smaller than the smoke generation characteristics of the electric wire connecting the switching device and the load is selected.

In the above configuration, in a normal operation in which the semiconductor switch is not short-circuited due to breakage, when a current exceeding the cutoff characteristic flows, the semiconductor switch is controlled to be turned off by the protection circuit. At the same time, the disconnection means does not disconnect. On the other hand, if the semiconductor switch is short-circuited due to damage and an overcurrent flows, the disconnection means is disconnected before the electrical wire smokes, thereby preventing the electrical wire from emitting smoke.

Further, in the switching device according to the third aspect of the present invention, the semiconductor switch, the protection circuit, and the disconnection means are housed in one package.

In the above configuration, when the switching device is connected to a predetermined position in the electric connection box of the vehicle, the package may be connected to the predetermined position, so that the connection operation can be facilitated. In addition, since it is not necessary to provide components corresponding to the disconnection means in the electric connection box while considering the smoke emission characteristics of the electric wires and the cutoff characteristics of the protection circuit, it is possible to reduce the time and effort required to create the electric connection box.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 in which the same reference numerals are given to parts corresponding to those in FIG. 5, a switching device 20 of this embodiment includes a power input terminal T1 and a power MOS
A fuse 21 as a disconnection means is provided on a conductor path electrically connecting the FET 12. As a result, in the switching device 20, the power MOS FET 12
When the fuse 21 is damaged and short-circuited, the fuse 21 is blown and the conductor path is broken. As a result, it is possible to prevent the overcurrent from flowing out such that the load 13 is damaged.

In the case of the switching device 20, the overcurrent cut-off characteristic of the power MOS FET 12 by the control unit 14 is changed to the electric wire 22 (for example, a harness) connecting the power output terminal T2 and the load 13 as shown by L1 in FIG. ) Is set smaller than the smoke characteristic curve L2. This can be realized by appropriately setting the value of the reference voltage, which is provided in the control unit 14 and is input to the comparator that detects the overcurrent by comparing the voltage across the shunt resistor R1 with the reference voltage.

The fuse 21 of the switching device 20
The fusing characteristics of the control unit 1 as shown by the curve L0 in FIG.
4 is set to a value larger than the overcurrent cutoff characteristic L1 and smaller than the smoke emission characteristic L2 of the electric wire 22.

Thus, in the switching device 20, during normal operation, the overcurrent protection function of the control unit 14 prevents the power MOS FET 12 from being damaged by overcurrent and preventing the electric wire 22 from emitting smoke. On the other hand, power MOS
When the FET 12 is short-circuited, the fuse 21 is blown, thereby preventing the electric wire 22 from emitting smoke. Since the destruction curve of the load 13 is larger than the smoke characteristic curve L2 of the electric wire 22, the load 13 is not damaged by the overcurrent.

In practice, as shown in FIG. 3, the switching device 20 has a power MOS FET 12, a control unit 14, a charge pump 15 and a fuse 21 provided at predetermined positions on a ceramic substrate 23 on which a conductor pattern is formed. At the same time, the ceramic substrate 23 is molded with a resin 24 to form a single packaging structure. From the resin 24, a power input terminal T1, a power output terminal T
2, a ground terminal T3, a diagnostic terminal T4, and a control signal input terminal T5 are derived. The switching device 20 thus packaged is electrically connected to the corresponding connector provided in the electric connection box of the vehicle via the terminals T1 to T5.

As described above, in the switching device 20, since the fuse 21 is provided in the package, the switching device 20 can be connected to a corresponding connector without providing an overcurrent prevention fuse in the electric connection box. Power MOS FET as described above just by connecting
It is possible to easily prevent smoking of the electric wire 22 and damage of the load 13 due to the short circuit of the load 12.

In the above embodiment, the case where the fuse 21 is provided as the disconnection means has been described. However, the present invention is not limited to this. For example, the conductor path between the power input terminal T1 and the power MOSFET 12 is partially cut. If the number or thickness of the aluminum wire wires having the fusing characteristic L0 described above with reference to FIG. 2 is provided so as to span the cut portion, the same effect as provided by the fuse 21 can be obtained. Can be. Further, for example, by narrowing the width of the electric circuit pattern at the position corresponding to the fuse 21, the electric circuit pattern may have the fusing characteristics L0 of FIG. In short, any structure may be used as long as it breaks when a current of a predetermined value or more flows.

In the above-described embodiment, the case where the disconnection means is provided on the conductor path between the power input terminal T1 and the drain of the power MOSFET 12 has been described.
The present invention is not limited to this. For example, the power MOSFET 1
2 may be provided on a conductor path between the source 2 and the power output terminal T2.

In the above embodiment, the switching device 20 having the overcurrent protection function has been described. However, the present invention can be applied to a switching device having an overheat protection function. In this case, the power M
A temperature detection circuit that outputs a voltage proportional to the temperature is provided near the OS FET 12, and the output voltage is input to the control unit 14. Then, by performing a logical operation including the output voltage in the control unit 14, the power MOS FET 12 may be turned off when overcurrent or overheating occurs.

Further, in the above-described embodiment, the case where the power MOS FET 12 is used as the semiconductor switch has been described.
It is not limited to ET.

[0032]

As described above, according to the first aspect of the present invention, the conductor path electrically connecting the power supply unit and the semiconductor switch, or the semiconductor switch and the load are electrically connected. By providing a disconnection means for disconnecting when a current equal to or more than a predetermined value flows in the conductor path, even if the semiconductor switch is short-circuited due to breakage, an overcurrent due to the short-circuit is not supplied to the wire or load,
Thus, it is possible to realize a switching device that can prevent a load from being damaged due to a short circuit of a semiconductor switch at the time of a short circuit.

According to the second aspect of the present invention, the cutoff characteristic of the protection circuit is set smaller than the smoke characteristic of the electric wire connecting the switching device and the load, and the disconnection characteristic of the protection circuit is used as the disconnection means. By selecting a wire that is greater than the cutoff characteristics and smaller than the smoke emission characteristics of the wire connecting the switching device and the load, the smoke emission of the wires is effective without disconnection when the disconnection means is unnecessary. And a switching device that can be prevented from occurring.

According to the third aspect of the present invention, the semiconductor switch, the protection circuit, and the disconnection means are housed in one package, so that the work of connecting the switching device to the electric connection box can be simplified. In addition, it is possible to realize a switching device that can reduce the time and effort required to create an electric junction box.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating a configuration of a switching device according to an embodiment.

FIG. 2 is a characteristic curve diagram showing a relationship between a fusing characteristic of a fuse, an overcurrent interruption characteristic of a protection circuit, and a smoke characteristic of an electric wire.

FIG. 3 is a schematic perspective view showing a state of a switching device having a one-package configuration.

FIG. 4 is a connection diagram showing a switching device using a conventional electromagnetic relay.

FIG. 5 is a connection diagram showing a configuration of a conventional switching device having a self-protection function.

[Explanation of symbols]

11 Power Supply Unit 13 Load 12 Semiconductor Switch (Power MOS F
ET) 14 Protection circuit (control unit) 21 Disconnection means (fuse) L1 Protection circuit breaking characteristic L2 Electric wire smoke characteristic L0 Disconnection characteristic

Claims (3)

[Claims] A semiconductor switch provided between a power supply unit and a load; and a semiconductor switch connected to a control signal input terminal of the semiconductor switch when an overcurrent flows in the semiconductor switch and / or when the semiconductor switch is overheated. A protection circuit that protects the semiconductor switch from overcurrent and / or overheating by outputting a control signal for turning off the semiconductor switch, wherein the power supply unit and the semiconductor switch are electrically connected. A switching device characterized in that a disconnection means for disconnecting when a current of a predetermined value or more flows is provided in a conductor path or a conductor path electrically connecting the semiconductor switch and the load. 2. The disconnection characteristic of the protection circuit is set smaller than the smoke generation characteristic of an electric wire connecting the switching device and the load, and the disconnection characteristic of the disconnection unit is set to be smaller than that of the protection circuit. 2. The switching device according to claim 1, wherein the switching device is selected so as to be smaller than the smoke emission characteristic of an electric wire connecting the switching device and the load. 3. 3. The switching device according to claim 1, wherein the switching device includes the semiconductor switch, the protection circuit, and the disconnection unit housed in one package.