JPH0547996A - Fail-safe semiconductor element - Google Patents

Abstract

PURPOSE:To enhance fail safe properties, to reduce the cost and the size. CONSTITUTION:In the case where heat is absorbed by a Peltier element 5 when a fail-safe transistor 10, etc., inputs an output allowance signal and an output signal '1' is output from a controller when the transistor 10 does not input the signal, a temperature fuse 3 of a wiring for inputting/outputting a current of the transistor 10 is melted at a normal operating temperature of the transistor 10.

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 that performs fail-safe processing that does not generate output when safety is not confirmed.

[0002]

2. Description of the Related Art Conventionally, fail-safe processing is required to ensure safety. Especially in railways, such a fail-safe property is required. In the output device in the field where fail-safety 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 source for the actuator. Need to be configured.

[0003]

By the way, in the case of conventional semiconductor devices such as transistors, discrete devices such as SSRs (solid state relays) and thyristors, and hybrid ICs in which these are integrated, and other integrated circuits, by any chance. When a short-circuit fault occurs, an output may occur even if there is no output enable signal.Therefore, when using such a semiconductor device in a fail-safe output device, the output enable signal and output result Is checked by checking. Further, even in the collating circuit having the check function, a large number of semiconductor elements are required to configure, for example, one AND gate in order to provide fail-safe property, and the circuit configuration becomes complicated.
In the unlikely event that the output semiconductor element has a short circuit failure, the power supply to the output semiconductor element is finally cut off by a mechanical relay with fail-safe characteristics, and the power is cut off to guarantee fail-safety. However, since such a mechanical relay is not easy to manufacture and it is difficult to mass-produce it, it is expensive and may not be downsized.

The present invention has been made in view of the above conventional problems, and provides a fail-safe semiconductor element which can constitute a fail-safe circuit which is simple and can be miniaturized without using a mechanical relay. The purpose is to

[0005]

Therefore, according to the present invention, there is provided heat absorbing means which is in close contact with a heat sink of a semiconductor element and which absorbs heat when electric energy is applied by an output permission signal inputted 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 and which is lower than a normal operating temperature of the semiconductor element and higher than a temperature at the time of the heat absorbing operation of the heat absorbing means.

[0006]

According to the above structure, when safety is confirmed, the output permission signal is input and electric energy is applied to the heat absorbing means, and the semiconductor element absorbs heat through the heat sink by the heat absorbing means. The temperature becomes lower than the normal operating temperature, that is, the temperature at which heat is generated when electricity is applied when heat is not being absorbed, and normal operation is performed. When the output permission signal is not input,
The electric energy is not applied to the heat absorbing means, the heat absorbing operation of the heat absorbing means is stopped, and the temperature of the semiconductor element becomes a normal operating temperature when the semiconductor element is energized. Therefore, the current-carrying wire of the semiconductor element, which is the disconnection means, is broken, and the power supply to the semiconductor element is cut off. This allows the semiconductor device to generate an output only when there is an output enable signal.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1 showing the transistor 10 which is the fail-safe semiconductor element of the present embodiment, the transistor 10
The chip 1 is bonded to a heat sink 2 made of, for example, copper, and is also bonded to a lead 4 made of, for example, copper by a thermal fuse 3 which is a disconnecting means and a current-carrying wire. The thermal fuse 3 is set to blow at a temperature lower than the 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 bonded and which is energized to absorb or generate heat at the bonding surface. In FIG. 1, the p-type semiconductor 5a and the n-type semiconductor 5b are used.
Joins the conductor as the joining surface 5c. The p-type semiconductor 5a and the n-type semiconductor 5b have conductors 5d and 5e serving as electrodes respectively formed at the opposite ends of the joint surface 5c, and a wire 6 is wired to both conductors 5d and 5e. In addition, the Peltier element 5 has a transistor 10 on the joint surface 5c side through an insulator 7a.
The conductors 5d and 5e are in close contact with the radiator 8 via the insulator 7b. And when it is judged safe,
Electric energy is applied to the Peltier element 5 via the wire 6 with the n-type semiconductor 5b at the positive electrode side so that the heat of the transistor 10 is absorbed by the junction surface 5c based on the input output permission signal "1". .. The resin 9 is a chip 1, a heat sink 2, a thermal fuse 3, a bonding portion of the leads 4,
The Peltier element 5 is molded, the radiator 8 is outside the mold of the resin 9, and the heat absorbed by the Peltier element 5 is removed by the radiator 8
Dissipate heat with.

Next, this fail-safe transistor 10
The fail-safe circuit of FIG. 2 configured by using will be described. In FIG. 2, the actuator 11 operates within the area A indicated by the broken line. The sensor 12 detects the presence / absence of a person or the like in the area A, and when the person does not exist, determines that it is safe and outputs the output permission signal "1". A using the fail-safe transistor 10 described above
The ND circuit 13 inputs the signal of the sensor 12 and the output signal output from the controller 14 and outputs a 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 cuts 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 output, it operates 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, the output permission signal “1” is input to the Peltier element 5. When the output permission signal "1" is input, the Peltier element 5 absorbs heat from the transistor 10 at the joint surface 5c that is in close contact with the heat sink 2.
It is energized via 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
The temperature t ₁ is the temperature of the transistor 10 when absorbing heat, and the temperature t ₂ is the normal operating temperature that is the heat generation temperature when the transistor 10 is energized when the Peltier element 5 does not absorb heat.
₁ <t ₀ <t ₂ . When the output signal is output from the controller 14, the transistor 10 generates heat, but the endothermic reaction of the Peltier element 5 maintains the temperature of the chip 1 of the transistor 10 below the temperature t _{0 at which the} thermal fuse 3 melts. Is working fine, controller
The output signal "1" from 14 is output as it is.

When the sensor 12 detects the presence of a person in the area A, the sensor 12 does not output the output permission signal "1", and the energization to the Peltier element 5 is stopped, and the Peltier element 5 is stopped.
The heat absorption operation of is also stopped. At this time the controller
When the output signal “1” is output from 14, the transistor 10
Since the endothermic operation of the chip 1 is stopped, the temperature of the chip 1 exceeds the temperature t _{0 at} which the thermal fuse 3 melts due to heat generation and becomes the normal operating temperature t ₂ . Therefore, the thermal fuse 3 is blown and the transistor 10 is in a disconnection failure state.
Power supply to chip 1 of 10 stops. 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.
Is not output to the actuator 11, and the fail-safe property is maintained.

Further, the transistor 10 has a structure in which, when an output is erroneously generated when there is no output enable signal, the output is cut off by itself, and 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 enhanced. According to this configuration, the fail-safe transistor 10 or the like absorbs heat by the Peltier element 5 when the output permission signal is input, and outputs the output signal “1” 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 the transistor 10 can be energized only when safety is confirmed. You can Further, since the transistor 10 is a structure that cuts off the output by itself and is an asymmetrical fault element in which only a disconnection fault exists, fail-safe property is enhanced. In addition, it can be replaced with an expensive mechanical relay that has a fail-safe function that has been used in the past, and the function is simplified and stored in the package of the semiconductor chip. It is extremely useful because it can be used for replacing an existing system or constructing a new system, especially in a field where fail-safe processing is required.

In this embodiment, the Peltier element 5 is made of resin 7.
However, as shown in FIG. 4, the Peltier element 5 may be adhered to the heat sink 2 of a resin mold type transistor which is a commercially available product through an insulator or the like. By doing so, even if the transistor 10 is damaged and the transistor 10 is replaced, the very expensive Peltier element 5 can be used again.

The Peltier element 5 may be constructed as shown in FIG. In the configuration of FIG. 5, the Peltier element 5 is housed in a metal package 21 such as stainless steel.
Here, the metal package 21a is closely attached to the joint surface 5c,
The metal package 21b is connected to the conductors 5d, 5 via the insulator 7b.
Since the metal packages 21a and 21b are on the heat absorption side and the heat generation side, respectively, they are heat-insulated between them by the heat insulating material 22.
Then, in this heat insulating material 22, the semiconductor 5a of the Peltier element 5,
The wire 6 wired in 5b is penetrated. This metal package 21 is adhered to the metal package 21a on the heat absorption side with an insulator or the like as a heat sink. With this configuration, replacement of the Peltier element 5 becomes extremely easy.

[0014]

As described above, according to the present invention, when safety is confirmed and the output permission signal is output, the semiconductor element absorbs heat, and when the output permission signal is not output,
By stopping the heat absorption operation and disconnecting the conducting wire of the semiconductor element if the semiconductor element is energized by mistake at this time, energization of the semiconductor element can be permitted only when safety is confirmed. In addition, the semiconductor element can be improved to fail-safe by making it an asymmetrical failure element in which only the disconnection failure mode exists, and it can be replaced with one having a fail-safe function which was a complicated structure in the past. As a semiconductor device with a fail-safe check function stored in, it is possible to realize miniaturization and further reduce the price.

[Brief description of drawings]

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

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

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

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

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

[Explanation of symbols]

 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)

[Claims] 1. A heat absorbing means, which is in close contact with a heat sink of a semiconductor element and absorbs heat when electric energy is applied by an output permission signal input only when safety is confirmed; A fail-safe semiconductor device, comprising: a disconnecting device that disconnects at a predetermined temperature lower than a normal operating temperature of the device and higher than a temperature of the heat absorbing device during the heat absorbing operation.