JPH0259630A - Temperature detection circuit - Google Patents

Abstract

PURPOSE:To obtain a specified temperature detection signal by impressing a voltage between the collector and the emitter of a transistor and detecting the leaked current in a thermal shutdown circuit which detects the abnormal rising of a temperature in an IC chip and stops the function of a circuit in the IC. CONSTITUTION:The thermal shutdown(heat shutdown circuit) circuit 1 is provided with PNP transistors Q1, Q2, Q3,... for detecting temperatures which are connected in parallel and the respective bases of the PNP transistors for detecting the temperatures are made in an open state. An NPN transistor Q10 is a transistor obtained by connecting the NPN transistor Q11 with a current mirror. It detects the leaked current between the collector and emitter of the PNP transistors Q1, Q2, Q3,... and drives the NPN transistor Q11, the generates a shutdown signal(temperature detection signal) on the collector side of the transistor Q11. When an output signal from an output terminal 1a is in a specified temperature state, it is outputted to a function circuit 2 which is the object of thermal shutdown.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a temperature detection circuit, and more specifically, to a thermal cutoff circuit that detects an abnormal rise in the temperature of an IC chip and stops the circuit function inside the IC. related to thermal shutdown circuits).

[Prior art] Conventional ICs, including drivers, etc., are susceptible to destruction of the IC due to an abnormal 1-0 rise in the temperature of the IC chip, generation of heat in the board on which the IC is mounted9, destruction of its peripheral circuits, and damage to the control target. In order to prevent damage to the mechanism, a thermal shutdown circuit is incorporated into the IC as one of the protection circuits.

This thermal shutdown circuit uses a transistor integrated at the same time as an IC driver, etc. as a temperature detection element, and detects a high temperature state because the voltage between its base and emitter depends on the temperature, and sends a cut-off signal. This is something that occurs.

FIG. 3 shows an example of such a conventional thermal shutdown circuit, in which the transistor Tr is an NPN transistor for two-degree detection, and the base-emitter of the transistor Tr is connected by bias resistors R1 and R2. The voltage between them is set, for example, to about 0.4V.

The temperature range in which the circuit normally operates, e.g. 0°C to 80°C
Since the base-emitter voltage for an NPN transistor Tr to operate is around 0.7V, the base-emitter voltage is 0.4V as mentioned above.
When the bias state is set to approximately
The transistor Tr is not in the "ON" state. However, when the temperature of the transistor Tr reaches about 150° C., the base-emitter voltage produced by the transistor Tr drops to around 0.4V.

Therefore, when the NPNI-transistor Tr reaches the temperature set as the detection temperature, for example, 180°C,
The transistor Tr becomes "ON", turning the emitter follower PNP l-transistor Trl "ON", and a temperature detection signal is obtained at the load resistor R3. This is the transistor Tr 2 .

It is output as a cutoff signal (output from OUTr, 0UT2) to each circuit whose function needs to be stopped via Tr3, etc., and is added to each functional circuit to stop the operation of that circuit.

[Problem to be solved] However, when a circuit that is subject to thermal shutdown control reaches the lPi temperature, leakage current occurs between the collector and emitter of the transistor in the circuit, and thermal shutdown occurs before the thermal shutdown circuit operates. There is a high risk that a circuit to be controlled will malfunction in a temperature range below a set temperature and cause an accident, and furthermore, the temperature at which such a malfunction occurs for each circuit varies.

In addition, such a thermal shutdown circuit must respond sensitively to the surrounding temperature environment and operate reliably, so a special circuit layout is required that prevents leakage current between the collector and emitter. Circuit design-
It is essential to take care that the thermal shield 7) down circuit is formed at a location from 11 to 7) that ensures operation at a predetermined high temperature.

Furthermore, in a thermal shutdown circuit that detects temperature by setting the bias between the base and emitter of a transistor, the thermal shutdown circuit is activated before the circuit starts operating, including variations in the characteristics of the circuit targeted for thermal shaft down control. Even if I try to make it work,
Because the bias settings themselves vary, detailed settings cannot be made, and it is difficult to absorb malfunctions by selecting the bias point.

The present invention solves the problems of the prior art. It is possible to generate a temperature detection signal before each circuit subject to thermal shutdown control malfunctions, and to improve the layout of the circuit. The purpose is to provide an easy temperature detection circuit.

[Means for Solving the Problems] To achieve such an object, the temperature detection circuit of the present invention is arranged at a place receiving heat from a heat generating part or in the vicinity of a heat generating part, and has a base side that is open or has a very high impedance. A temperature detection signal is generated in a predetermined temperature state by applying a voltage between the collector and emitter of a transistor connected to the sensor and detecting the leakage current between the collector and emitter.

[Function] In this way, a predetermined temperature detection signal is obtained by applying a voltage between the collector emitter of the transistor and detecting the leakage current, so that the collector emitter of each circuit that is subject to temperature control is This means that the malfunction condition due to the leakage current between the two and the condition for temperature detection of the temperature detection circuit are due to the same leakage current. Therefore, it is possible to generate a temperature detection signal within a leakage current range that does not cause malfunction in the circuit that is the subject of temperature control.

As a result, temperature can be detected before each circuit starts malfunctioning due to leakage current, and since temperature detection is based on collector-emitter leakage current, no matter where the temperature detection circuit is placed, Only heat transfer needs to be considered, and the layout can be done relatively freely.

Note that the leakage current value between the collector and emitter that is the target of temperature detection is determined by the heat receiving environment of the transistor that performs temperature detection and the temperature environment in which the circuit that is the target of temperature control is placed. If the heat receiving conditions of the transistors are made larger, the overall detected leakage current value can be increased, and if a plurality of temperature detection transistors are connected in parallel, a correspondingly larger leakage current can be obtained.

Therefore, temperature detection can be performed reliably.
In particular, if the type of transistor used to detect temperature for thermal shutdown (thermal shirt down) and the type of transistor that malfunctions in a functional circuit that is subject to thermal shutdown are of the same type, it is necessary to ensure that the Thermal shutdown can be activated.

[Example] Please refer to the drawings below for an example of this invention! ((This will be explained in detail.

FIG. 1 is a block diagram of one embodiment in which the temperature detection circuit of the present invention is applied to a thermal shutdown circuit, and FIG. 2 is a block diagram of another embodiment thereof.

In Fig. 1, ■ is a thermal shutdown circuit, which shuts off when the drive circuit that drives motors, actuators, etc. (function circuit 2, which includes dry nozzle) reaches a high temperature state above a predetermined level. It functions to send a signal to stop the operation of the functional circuit 2.

Thermal shutdown circuit 1 includes II! connected in parallel. PNP) transistor Qt for temperature detection.

Q2. The bases of the PNP transistors for temperature detection are not connected to other circuits and are in an open state.

Each emitter is commonly connected to the power supply voltage +VDD, and each collector is commonly connected to an NPN) transistor Q.
It is connected to the collector of lθ.

NPN transistor Qlθ is NPN) transistor Ql
A transistor connected in a current mirror with PN
P) Runstar Qr + Q2 + Qa.

Detect the leakage current between collector and emitter of N
The PN l-transistor Qll is driven to generate a cutoff signal (temperature detection signal) on its collector side, which is taken out from the output terminal 1a. Then, when this output signal reaches a predetermined temperature state, it is output to the functional circuit 2 that is subject to thermal shutdown.

Here, PNP) transistors Ql, Q2 . Q3゜...
・ is usually integrated around the functional circuit 2 that is subject to thermal shutdown, and is also integrated around the NPN transistor Q
Similarly, tθ and Qn are formed within the same chip as this functional circuit 2. Therefore, when the functional circuit 2 or the entire IC chip including this circuit reaches a high temperature, the PNP) transistor Qt.

Leakage current It, tz, I3+ ” between each collector emitter and rim of Q2 + Q3+ ・Φ・
occurs, which increases counternumerically as the temperature of the IC chip rises, causing each PNP transistor Ql to increase.

Sum of leakage currents I = ΣIl of Q2 + Qa, ...
+I2+I3+...The urn is further amplified by the current mirror circuit, turns on the NPN transistor Qll, and generates a cutoff signal at a predetermined level at the output terminal 1a.

In this case, for example, when a PNP transistor is used, even if the leakage current is on the order of several I゜ microamperes at about 180 degrees, it is necessary to arrange multiple transistors to generate leakage current for temperature detection. Therefore, it is possible to obtain up to about 100 microamperes, and by amplifying and detecting this with a current mirror circuit, a cutoff signal can be generated.

Here, it is assumed that the functional circuit 2 has a driving PNP transistor Q12 that constitutes a drive circuit therein, and that the current value of the zl operation due to the collector-emitter leakage current is Is. In case,
PNP transistor Q that detects temperature by leakage current
t, Q2 + Q3+·Φ, and in contrast to transistor Q/2 of functional circuit 2, PNP transistor Q1. Q2. Q3.・
Since the bases of the transistors are open, the average value of the current value of each transistor is also approximately 1- or less than Is. Therefore, the detected leakage current value I has the relationship I>nXl5 (where n is the number of transistors for leakage current detection), and a cutoff signal can be generated at a current value greater than Is, and the functional circuit 2 It is possible to stop the operation before it malfunctions.

In this case, a PNP that detects temperature by leakage current
l-transistor Q1. Q2. By connecting a plurality of transistors Q3t in parallel, variations in the leakage current of these transistors are absorbed, variations in the operating point of temperature detection are suppressed, and highly accurate temperature detection is possible.

Here, when detecting the temperature of the entire IC chip and generating a cutoff signal, each PNP transistor Qt
, Q2. Q3t Fist... can be distributed and provided in the center and periphery of the IC chip.

In this way, the entire IC chip can be made into a circuit with a temperature sensor, and it is also possible to use the output of the NPN transistor Qll as a temperature detection signal in an external circuit.

Figure 2 shows the leakage current of the temperature detection transistor in A
It receives the signal through an ND circuit and generates a cutoff signal. In FIG. 2, a plurality of thermal shutdown circuits 3 are arranged to operate only one transistor Q1 for temperature detection in FIG. 1, and their respective outputs are connected to A.
N f) Connected to circuit 4. Then, when the AND condition of the temperature detection outputs of these thermal shutdown circuits 3 is satisfied to 1, a cutoff signal is taken out from the AND circuit 4.

In this manner, the AND circuit 4 receives the temperature detection signal from each thermal shutdown circuit 3, and unless all the thermal shutdown circuits 1 have detected the temperature, the cutoff signal will not be generated. Therefore, this is a circuit that reliably detects that the temperature has exceeded a certain level, for example, it was set within the range of required operating specifications.
- Suitable for circuits that require thermal shutdown after the temperature limit has definitely been exceeded. On the other hand, the one shown in FIG. 1 is suitable for reliably operating at a temperature below a set upper limit temperature.

Note that the AND circuit 4 may be used instead of an OR circuit. In this case, the cutoff signal can be taken out when the logical sum condition of the temperature detection outputs of the plurality of thermal shutdown circuits 3 is satisfied. Note that the logical sum condition and the logical product condition are based on the temperature detection transistor Ql + Q2 . which generates a leak current as shown in FIG. It is also possible to connect the Q3% transistor. In FIG. 1, depending on the setting conditions of the operating points of transistors Qtθ and Q/l,
It can be a logical product or a logical sum.

The above embodiments mainly focus on thermal shutdown, but the embodiment shown in FIG. The case shown in FIG. 1 is suitable for use as a temperature sensor with stricter safety requirements.

As explained above, in the embodiment, an example of thermal shutdown of a drive circuit such as a motor or an actuator is given, but the present invention is not limited to the case of thermal shutdown of such a circuit. ,
It can also be used as a normal temperature sensor circuit equipped with various circuits. For example, it can be used as a discharge lamp ballast, its lighting circuit, and a temperature sensor circuit for household electrical equipment including heat sources such as kotatsu and coffee makers.
iJ Noh. In addition, the form of the transistor that detects leakage current between collector and emitter for temperature detection is
It may be a PNP) transistor or an NPN) transistor. Further, although the base of each transistor is in an open state, it may not be completely open (or may be connected at a very high impedance).

[Effects of the Invention] As can be understood from the following explanation, in this invention, a predetermined temperature detection signal is obtained by applying a voltage between the collector emitter of a transistor and detecting the leakage current. Therefore, the malfunction condition due to leakage current between the collector emitter of each circuit subject to temperature control and the condition for temperature detection of the temperature detection circuit are due to the same leakage current, so the circuit subject to temperature control A temperature detection signal can be generated within a leakage current range that does not cause malfunction.

As a result, each circuit starts the GL operation due to the leakage current.1) Temperature detection can be performed at II, and since temperature detection is performed by the leakage current between the collector and emitter, it is possible to place the temperature detection circuit at any position. Even if they are arranged in the same way, only heat transfer needs to be taken into account, and the layout can be done relatively freely.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment in which the temperature detection circuit of the present invention is applied to a thermal shutdown circuit, Fig. 2 is a block diagram of another embodiment thereof, and Fig. 3 is a block diagram of a conventional thermal shutdown circuit. FIG. 2 is a block diagram of a shutdown circuit. 1... Thermal shutdown circuit, 2... Functional circuit, 4... AND circuit, QIT Q2 + Q3+
Qno2... PNP transistor for temperature detection, Q10
．． Q//...NPN transistor.

Claims (2)

[Claims] (1) A voltage is applied between the collector-emitter of a transistor that is placed in a place that receives heat from a heat-generating part or near the heat-generating part, and whose base side is open or connected to a very high impedance, to reduce the leakage current between the collector-emitter. 1. A temperature detection circuit that generates a temperature detection signal in a predetermined temperature state by detecting the temperature. (2) The temperature detection signal is a cutoff signal for stopping the operation of other circuits, and a plurality of transistors are provided in the IC, and the leakage current of each transistor or its detection signal is detected by an AND circuit or an OR circuit. 2. The temperature detection circuit according to claim 1, wherein the cutoff signal is generated based on a logical product condition or a logical sum condition of the leakage currents.