JPH0234024A - Temperature protecting circuit for semiconductor device - Google Patents

Abstract

PURPOSE:To shut off an overcurrent effectively and to protect the semiconductor device against a high temperature by inserting a control characteristic change circuit between a temperature sensing circuit and a DC current control circuit, and devising the temperature sensing circuit to set a difference between a temperature of start of control and a restoration temperature variably. CONSTITUTION:Identical components are selected for all transistors(TRs) 21-24 in the temperature sensing circuit and resistive elements are selected as R1+R2=R3+R4 and 3XR4<R2. A temperature characteristic level (c) of a Schmitt trigger circuit has a hysteresis characteristic and the TRs 21-23 are turned of till a positive threshold level VTH of the said trigger circuit is reached. Moreover, the TR 24 ts turned on from the negative threshold level VTH of the said trigger circuit. Thus, the temperature difference between the restoring temperature (a) and a DC cut-off temperature (c) is made variable by adjusting the resistive elements R1, R2 so as to set the restoring temperature (a) higher or lower. Thus, an overcurrent is shut off effectively and the protection of the semiconductor device against a high temperature is strengthened.

Description

[Detailed Description of the Invention] Summary] The present invention relates to a temperature protection circuit that appropriately detects a high temperature state and protects the semiconductor device circuit in order to prevent it from being thermally destroyed due to the continuous flow of a large current to the semiconductor device circuit. , with the aim of providing a temperature protection circuit that can effectively cut off excessive current and strengthen protection against high temperatures with a relatively simple configuration. In a temperature protection circuit for a semiconductor device that includes a temperature detection circuit that detects the temperature of the circuit and a control circuit that controls a direct current passing through the output stage based on the output of the temperature detection circuit, the output terminal of the DC current control circuit of the output stage A control characteristic change circuit that changes the potential with hysteresis characteristics in response to input terminal potential changes is inserted between the temperature detection circuit and the DC current control circuit, and the temperature detection circuit controls the start and return of control of the control characteristic change circuit. It is configured by setting the temperature difference between the

[Industrial Field of Application] The present invention relates to a temperature protection circuit that appropriately detects a high temperature state and protects the semiconductor device circuit in order to prevent thermal damage due to continuous flow of a large current through the semiconductor device circuit.

Conventionally, a circuit called a thermal shutdown circuit using a temperature detection circuit shuts off the current circuit when it detects a high temperature in order to protect the temperature of the semiconductor element. There is no more passage, and the temperature immediately returns to normal for operation.

Therefore, the current circuit is turned on and a large current flows again. This operation is repeated because the temperature to be protected is quickly reached and the current circuit is turned off.

Therefore, unless the continued flow of large current due to abnormal operation is detected by other means and the state is removed, the high temperature of the semiconductor element will continue. Cutting off and restoring large currents is said to be an oscillation phenomenon, and there was a desire to develop technology to prevent this from occurring.

[Prior Art] When a high power circuit is put into practical use as a semiconductor device, some abnormality may occur in or around the device, causing a current even larger than the normal current to flow. At that time, the element and peripheral equipment generate heat, which may lead to abnormal operation or even destruction. Therefore, a temperature protection circuit having the configuration shown in FIG. 5 has been realized. In FIG. 5, 1 is a semiconductor signal amplification element;
2 is an output circuit, 3 is a DC power supply terminal, 4 is an impedance control circuit, and 5 is a temperature detection circuit. The temperature of the semiconductor element 1 is detected directly or the operating temperature of the circuit is detected in the vicinity of the element by a temperature detection circuit 5.

When it is detected that a predetermined high temperature has been reached, the output of the detection circuit 5 controls the elements in the impedance control circuit 4 to have a high impedance. Therefore, the DC current flowing from the DC power supply terminal 3 through the output circuit 2 to the ground is interrupted.

Also, at this time, since the output circuit 2 does not operate in a direct current manner,
No AC output occurs at the signal terminal. Since the direct current is cut off, the operation of the semiconductor element is stopped, and any abnormality in the circuit is interrupted. Further, the operation of the temperature detection circuit 5 causes the direct current to stop flowing, and the temperature of the element and the area around the element returns to the temperature before the current was cut off. When the temperature detection circuit 5 detects that the temperature has been restored, the control signal to the impedance control circuit 4 is removed, the application of the DC voltage is restarted, and the output circuit 2 is fully operated again.

However, at the same time, heat generation occurs again due to the large DC current.

[Problems to be Solved by the Invention] Control of the impedance control circuit 4 by the temperature detection circuit 5 is performed when there is a detection output of the temperature detection circuit 5, and immediately after impedance control is performed, the control of the impedance control circuit 4 is performed by the next temperature detection circuit 5. The DC current was cut off and restored in a regular manner, resulting in an output of . In other words, the high temperature state of the element will not change until the cause of the abnormal current is removed to cause an oscillation phenomenon, and the operational effect of inserting the impedance control circuit 4, which prevents thermal destruction, into the DC circuit of the output stage 2. There is almost no meaning.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks, and to provide a temperature protection circuit that can effectively cut off excessive current with a relatively simple configuration and strengthen protection against high temperatures.

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. In FIG. 1, ▪ indicates a semiconductor element circuit, 2 indicates an output stage, 3 indicates a DC power supply terminal, 4 indicates a DC current control circuit, 5 indicates a temperature detection circuit, and 6 indicates a control characteristic changing circuit.

An output stage circuit 2 driven by the semiconductor element circuit 1 and through which a large DC current flows, a temperature detection circuit 5 that detects the temperature of the semiconductor element circuit 1, and a DC current passing through the output stage 2 is controlled by the output of the temperature detection circuit 5. In the temperature protection circuit for a semiconductor device including the control circuit 4, the present invention has the following configuration. That is, the control for changing the output terminal potential of the DC current control circuit 4 of the output stage 2 with hysteresis characteristics with respect to changes in the input terminal potential is performed by controlling the characteristic change circuit 6 to the temperature detection circuit 5.
and the DC current control circuit 4, and the temperature detection circuit 5 is configured to variably set the temperature difference between the control start temperature and the return temperature of the control characteristic change circuit 4.

[Operation] The temperature detection circuit 5 detects the temperature of the semiconductor element circuit 1, and sends an output signal to the control characteristic change circuit 6 when the temperature rises to a predetermined temperature. The control characteristic change circuit 6 controls the control circuit 4 to cut off the direct current. The semiconductor element circuit 1 therefore remains in that state until the temperature decreases to a temperature considerably lower than the temperature at which the direct current was cut off. When the temperature detection circuit 5 detects that the temperature has become low, the control characteristic change circuit 6 is controlled to cause a direct current to flow through the output stage 2. The temperature difference between the operating temperature of the control characteristic change circuit 6 and the return temperature is variably set in the temperature detection circuit 5.

Therefore, the operating and recovery temperatures are set in consideration of the semiconductor element circuit I, the output stage 2, the expected DC current, etc.

[Embodiment] FIG. 2 is a circuit configuration diagram showing a case where a Schmitt trigger circuit is used as the control characteristic change circuit 6 and a circuit using a transistor is used as the temperature detection circuit 5, as an embodiment of the present invention. In FIG. 2, 1) indicates the first circuit in the temperature detection circuit 5, 12 indicates the second circuit, 21, 22, and 23 indicate transistors of the first circuit, and 24 indicates a transistor of the second circuit. fan, fb) represent voltages of a reference voltage generation circuit composed of transistors and resistive elements, each of which is a voltage at a stable level that is dependent on Vcc but less dependent on temperature. (a) is a level that determines the return temperature, which is determined by adjusting the resistance elements R1 and R2. fbl is determined by adjusting resistance elements R3 and R4 at a level that determines the operation start temperature.゛At room temperature, the transistors 21 to 24 are
is off, and transistors 21 to 24 are on at high temperatures. Now, assume that transistors 21 to 24 are all the same, and the resistance element is R1+R2=R3+R4, 3XR4<R2
When selecting (C1), the temperature characteristics at the level shown in FIG. 3 become as shown in FIG. , transistor 24
turns on from the value on one side of the threshold value ■F. Therefore, by adjusting the resistance elements R1 and R2 to set the return temperature shown in FIG. 3 lower or higher, the temperature difference from the DC cutoff temperature can be made variable. FIG. 4 is a diagram showing the level (d) of the output terminal of the Schmitt trigger circuit. The horizontal axis indicates the temperature corresponding to FIG. Therefore, it can be seen that a hysteresis characteristic is exhibited between the cut-off temperature and the return temperature shown in FIG. 3.

[Effects of the Invention] In this way, according to the present invention, after an abnormal state occurs and the current is cut off, the temperature of the semiconductor element circuit can be sufficiently lowered and then the state can be restored. Failures due to high temperatures will no longer occur.

Since the temperature drop until the state is restored can be adjusted, the abnormal state can be effectively and appropriately dealt with.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention, FIG. 2 is a diagram showing the circuit configuration of an embodiment of the present invention, and FIG.
FIG. 4 is an explanatory diagram of the operation of FIG. 2, and FIG. 5 is a diagram showing a conventional temperature protection circuit of a semiconductor device. 1...Semiconductor element circuit 2...-Output stage 3-DC power supply terminal 4...-DC current control circuit 5...Temperature detection circuit 6--Control characteristic change circuit Patent applicant Fujitsu Limited Agent Patent attorney Suzuki Eisuke Nao & his book is a clear book, police officer H month's 1st grade! Figure Temperature Figure 3 ', jjL degree hysteresis 1 life Figure 4

Claims (1)

[Claims] I. An output stage (2) driven by the semiconductor element circuit (1) through which a large DC current flows; a temperature detection circuit (5) that detects the temperature of the semiconductor element circuit (1); Detection circuit (5
) A temperature protection circuit for a semiconductor device comprising a control circuit (4) that controls the direct current passing through the output stage (2) by an output, wherein the output terminal potential of the direct current control circuit (4) of the output stage (2) is The temperature detection circuit (5) is a control characteristic change circuit (6) that changes the input terminal potential with hysteresis characteristics.
and a direct current control circuit (4), and the temperature detection circuit (5) is characterized in that the temperature difference between control start and return of the control characteristic change circuit (4) is variably set. Temperature protection circuit. II. The temperature detection circuit according to claim 1 comprises a first
and a second circuit in which the output terminal of one transistor is connected to the midpoint of the first circuit, and each circuit is applied with a DC voltage divided by resistance, and by changing each resistance value, A temperature protection circuit for a semiconductor device, characterized in that the output voltage of the first circuit is changed.