JP2890075B2 - Fail-safe semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fail-safe semiconductor device which performs a fail-safe process that does not generate an output when safety is not confirmed.

[0002]

2. Description of the Related Art Conventionally, fail-safe processing is required to ensure safety. Particularly in railways and the like, such fail-safe properties are required. As described above, in an output device in a field where the fail-safe property is required, a signal is output only when there is an output permission signal indicating that safety is ensured even if the actuator malfunctions, such as a power supply for the actuator. It is necessary to be configured as follows.

[0003]

Incidentally, conventional semiconductor elements such as transistors, discrete elements such as SSRs (solid state relays) and thyristors, hybrid ICs in which these are integrated, and other integrated circuits should be used. When a short-circuit fault occurs, an output may occur even though there is no output permission signal. Therefore, when such a semiconductor device is used in a fail-safe output device, an output permission signal and an output result are required. Is checked against. Furthermore, in the matching circuit having this check function, for example, a large number of semiconductor elements are required to constitute one AND gate in order to provide the fail-safe property, and the circuit configuration becomes complicated.
In the unlikely event that a short-circuit fault occurs in the output semiconductor element, the power supply to the output semiconductor element is eventually disconnected by a mechanical relay with fail-safe characteristics, and the energization is cut off to ensure fail-safe performance However, since such a mechanical relay is difficult to manufacture and difficult to mass-produce, it is expensive and may not be able to be miniaturized.

The present invention has been made in view of such conventional problems, and provides a fail-safe semiconductor device capable of forming a fail-safe circuit that can be simply and miniaturized without using a mechanical relay. The purpose is to:

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a heat absorbing means which is in close contact with a heat sink of a semiconductor element and which absorbs heat by applying electric energy with an output permission signal which is input only when safety is confirmed; And a disconnection means for disconnecting at a predetermined temperature, which is a current-carrying wire of the semiconductor element, which is lower than a normal operating temperature of the semiconductor element and higher than a temperature of the heat absorbing means during the heat absorbing operation.

[0006]

According to the above arrangement, when safety is confirmed, an output permission signal is input, electric energy is applied to the heat absorbing means, and the heat absorbing means absorbs heat from the semiconductor element through the heat sink. The temperature is lower than the normal operating temperature, that is, the heat generating temperature when power is supplied when heat is not absorbed, and the device operates normally. When the output permission signal is not input,
Electric energy is no longer applied to the heat absorbing means, the heat absorbing operation of the heat absorbing means stops, and the temperature of the semiconductor element becomes the normal operating temperature when the semiconductor element is energized. For this reason, the energizing line of the semiconductor element which is the disconnection means is disconnected, and the energization to the semiconductor element is cut off. As a result, an output can be generated from the semiconductor element only when there is an output permission signal.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a transistor 10 which is a fail-safe semiconductor device of the present embodiment.
The chip 1 is bonded on a heat sink 2 made of, for example, copper, and is bonded to a lead 4 made of, for example, copper by a thermal fuse 3 which is a disconnection means and a current supply line. The thermal fuse 3 is set so as to be blown below a normal operating temperature of the transistor 10 as described later. The Peltier element 5, which is a heat absorbing means, is an element in which dissimilar metals or semiconductors are joined and is energized to absorb or generate heat at the joining surface. In FIG. 1, the p-type semiconductor 5a and the n-type semiconductor 5b are used.
Are joined with the conductor as the joining surface 5c. In the p-type semiconductor 5a and the n-type semiconductor 5b, conductors 5d and 5e serving as electrodes are formed at opposite ends of the joint surface 5c, and wires 6 are respectively wired to the conductors 5d and 5e. The Peltier element 5 is connected to the transistor 10 via the insulator 7a on the side of the junction 5c.
The conductors 5d and 5e are in close contact with the radiator 8 via the insulator 7b. And when it ’s safe,
Electric energy is applied to the Peltier element 5 via the wire 6 with the n-type semiconductor 5b being on the positive side so that the heat of the transistor 10 is absorbed at the junction surface 5c based on the input output permission signal "1". . The resin 9 is a bonding portion of the chip 1, the heat sink 2, the thermal fuse 3, and the lead 4,
The Peltier element 5 is molded, and the radiator 8 is out of the resin 9 mold.
To dissipate heat.

Next, the fail-safe transistor 10
2 will be described with reference to FIG. In FIG. 2, the actuator 11 operates within a range A indicated by a broken line. The sensor 12 detects the presence or absence of, for example, a person or the like in the area A, and when there is no person, judges that the person is safe and outputs an output permission signal “1”. A using the aforementioned fail-safe transistor 10
The ND circuit 13 inputs the signal of the sensor 12 and the output signal output from the controller 14 and outputs the logical product of both signals. When the signal from the sensor 12 is the output permission signal “1”, Outputs the output signal of the controller 14 as it is, and shuts off the output signal to the actuator 11 when the output permission signal “1” is not output.
The actuator 11 outputs the output permission signal “1” from the sensor 12.
Is operated based on the output signal of the controller 14 output from the AND circuit 13.

Next, the operation will be described. When no person is present in the area A by the sensor 12, an output permission signal “1” is input to the Peltier element 5. When the output permission signal “1” is input, the Peltier element 5 absorbs the heat of the transistor 10 at the bonding surface 5 c that is in close contact with the heat sink 2.
Electricity is supplied through the wire 6. The heat of the Peltier element 5 is radiated through the radiator 8 or the outside air. As shown in FIG. 3, the setting of the fusing temperature t ₀ of the thermal fuse 3 is as follows.
The temperature t ₁ is a temperature of the transistor 10 when absorbing heat, and the temperature t ₂ is a normal operating temperature which is a heat generation temperature when the transistor 10 is energized when the Peltier element 5 does not absorb heat.
₁ <and t ₀ <t _2. When the output signal from the controller 14 is output transistor 10 generates heat, but the temperature of the chip 1 of the transistor 10 by the endothermic reaction of Peltier element 5 is maintained below a temperature t ₀ to blowing of the thermal fuse 3, the transistor 10 Works fine and the controller
The output signal "1" from 14 is output as it is.

When the presence of a person in the area A is detected by the sensor 12, the output permission signal "1" is not output from the sensor 12, and the power supply to the Peltier element 5 is stopped.
Endothermic operation has also stopped. This time mistakenly the controller
When the output signal "1" is output from the transistor 14, the transistor 10
Since the heat absorption operation of the chip 1 is stopped, the temperature of the chip 1 exceeds the temperature t _{0 at} which the temperature fuse 3 is blown by the heat generation, and becomes the normal operation temperature t ₂ . Therefore, the thermal fuse 3 is blown, and the transistor 10 is disconnected.
The energization to the ten chips 1 is stopped. Therefore, even if the output signal "1" is erroneously output from the controller 14 at this time, the energization of the transistor 10 is cut off, so that the output signal "1"
Is not output to the actuator 11, and the fail-safe property is maintained.

The transistor 10 has a structure in which if an output is erroneously generated when there is no output permission signal, the transistor 10 itself shuts off the output. The transistor 10 is an asymmetrical fault element in which only a disconnection fault mode exists and no short-circuit fault mode exists. Therefore, the fail-safe property can be further improved. According to this configuration, when the output permission signal is input, the Peltier element 5 absorbs the heat of the fail-safe transistor 10 and the like, and the output signal “1” is output from the controller 14 when the output permission signal is not input. In such a case, the temperature fuse 3 which is the current input / output wiring of the transistor 10 is blown at the normal operating temperature of the transistor 10, so that energization of the transistor 10 is permitted only when safety is confirmed. I can do it. Further, since the transistor 10 has a structure in which the output is cut off by itself and is an asymmetrical fault element in which only a disconnection fault exists, fail-safe performance is improved. Then, it can be replaced with an expensive mechanical relay having a fail-safe function which has been conventionally used, and such a function is simplified and stored in a package of a semiconductor chip. Is realized, and the cost can be further reduced. In particular, in a field where a fail-safe process is required, it can be used for replacing an existing system or constructing a new system, which is extremely useful.

In this embodiment, the Peltier element 5 is
However, as shown in FIG. 4, the Peltier element 5 may be closely adhered to the heat sink 2 of a resin-molded transistor which is a commercially available product via an insulator or the like. In this way, even if the transistor 10 is damaged and the transistor 10 is replaced, the very expensive Peltier element 5 can be used again.

Further, the Peltier element 5 may be configured as shown in FIG. The configuration of FIG. 5 is such that the Peltier element 5 is housed in a metal package 21 such as stainless steel.
Here, the metal package 21a is brought into close contact with the bonding surface 5c,
The metal package 21b is connected to the conductors 5d, 5
e, and the metal packages 21a and 21b are on the heat absorbing side and the heat generating side, respectively.
Then, the semiconductor 5a of the Peltier element 5 is
The wire 6 wired to 5b is penetrated. The metal package 21 is brought into close contact with the heat-absorbing side metal package 21a via an insulator or the like using the heat sink as the heat sink. With such a configuration, replacement of the Peltier element 5 becomes very easy.

[0014]

As described above, according to the present invention, when the safety is confirmed and the output permission signal is output, the semiconductor device absorbs heat, and when the output permission signal is not output,
The heat absorption operation is stopped, and if the semiconductor element is energized by mistake at this time, the energization line of the semiconductor element is disconnected, so that energization to the semiconductor element can be permitted only when safety is confirmed. Further, the fail-safe function can be enhanced by using an asymmetrical failure element in which only the disconnection failure mode exists in the semiconductor element, and the semiconductor element can be replaced with an element having a fail-safe function, which has conventionally been a complicated structure. As a semiconductor device having a fail-safe check function housed therein, downsizing can be realized and the price is further reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a sectional view showing the semiconductor device of FIG. 1;

FIG. 3 is an explanatory diagram of an operating temperature of the semiconductor of FIG. 2;

FIG. 4 is another configuration diagram of a fail-safe semiconductor device.

FIG. 5 is another configuration diagram of a fail-safe semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 chip 2 heat sink 3 thermal fuse 5 Peltier element 5a p-type semiconductor 5b n-type semiconductor 11 actuator 12 sensor 13 AND circuit 14 controller 21 metal package 22 heat insulating material

Claims (1)

(57) [Claims] A heat-absorbing means which is in close contact with a heat sink of a semiconductor element and absorbs heat by applying electric energy with an output permission signal which is input only when safety is confirmed; A fail-safe semiconductor device, comprising: disconnection means for disconnecting at a predetermined temperature lower than a normal operating temperature of the element and higher than a temperature of the heat absorbing means during the heat absorbing operation.