JPH0260228A - Drive circuit having thermal shutdown circuit - Google Patents

Abstract

PURPOSE:To permit a drive circuit to attain thermal-shut down before it starts malfunction by applying a voltage between collector emitters of a transistor whose base side is connected to a considerably high impedance and detecting the leak current to obtain an interruption signal in a prescribed temperature. CONSTITUTION:A thermal shutdown circuit 1 has PNP transistors Q1, Q2, Q3,... for temperature detection connected in parallel and respective bases of respective transistors for temperature detection are in an open state. Respective collectors are connected in common to the emitter of an NPN transistor Q10. Q10 is a transistor which is current mirror-connected with an NPN transistor Q11, and the leak current between the collector emitters of Q1, Q2, Q3... are detected to drive Q11. The shutdown signal is generated on the side of the collector at the prescribed temperature, and the signal is fetched from an output terminal 1a, and outputted to the input terminal 2a of the drive circuit 2, whereby the operation of the drive circuit 2 is stopped. Here, Q1, Q2, Q3,...Q10, Q11 are formed in the same chip of the drive circuit 2.

Description

[Detailed Description of the Invention] [Industrial Application] The present invention relates to a drive circuit having a thermal shutdown circuit (hereinafter referred to as a thermal shutdown circuit). This invention relates to an improvement in a thermal shutdown circuit that stops the operation of a drive circuit inside an IC.

[Prior art] In conventional ICs including drive circuits, abnormal temperature L5'i' of the IC chip causes destruction of the IC, generation of heat in the board on which the IC is mounted, destruction of its peripheral circuits, and destruction of the controlled object. 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 drive circuit that is converted into a C, and a transistor that is integrated at the same time as the drive circuit, as a temperature detection element. It detects the condition and generates a shut-off signal.

FIG. 3 shows an example of such a conventional thermal shutdown circuit, in which the transistor Tr is an NPH transistor for temperature detection, and the bias resistor R
By t*R2, the voltage between the base and emitter of the transistor Tr is set to, for example, 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 DEG C., the base-emitter voltage at which it operates drops to around 0.4V.

Therefore, when the NPN transistor Tr reaches the temperature set as the detection temperature, for example, 180 degrees Celsius, the transistor Tr becomes "ON", and the emitter follower PNP) transistor Trl is turned "ON", and its load resistance R3 A temperature detection signal is obtained. This is output as a cutoff signal (output from OUTl, 0UT2) to the drive circuit whose function needs to be stopped via the transistors Tr2*Tr3, etc., and is applied to each drive circuit to stop the operation of that circuit (1).

[Problem to be solved] However, when the temperature of the drive circuit that is subject to thermal shutdown control becomes high, leakage current occurs between the collector and emitter of the transistor in that circuit, causing the drive circuit to shut down before the thermal shutdown circuit operates. There is a high risk that the circuit will malfunction within a range below the set temperature and cause an accident, but the temperature at which such a malfunction occurs for each drive 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 device is required that prevents leakage current between the collector and emitter. Therefore, it is essential to take into account the circuit design so that the thermal shutdown circuit is located at a location where it can operate reliably at a predetermined high temperature.

Furthermore, in a thermal shutdown circuit that relies on temperature detection based on the piezo setting between the base and emitter of a transistor, it is important to operate the thermal shutdown circuit before the circuit malfunctions due to variations in drive circuit characteristics. However, since 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, and is capable of generating a temperature detection signal before the drive circuit that is subject to thermal shirt I/down control malfunctions, and that L1 provides a drive circuit with a heat cutoff circuit that is easy to layout.
target

[Means for Solving the Problems] A drive circuit having a heat cutoff circuit according to the present invention for achieving object 1 is configured such that the drive circuit and the heat cutoff circuit are integrated into one chip, and the drive circuit has a heat cutoff circuit. The circuit applies a voltage between the collector and emitter of a transistor whose base side is open or connected to a very high impedance, and by detecting the leakage current between the collector and emitter, a cutoff signal is generated at a predetermined temperature state. , this cutoff signal is supplied to the drive circuit and its operation is stopped +L
It is something to do.

[Operation] In this way, by applying a voltage between the collector and emitter of the transistor and detecting the leakage current, a cutoff signal for thermal shutdown at a predetermined temperature is obtained. The malfunction condition due to leakage current between the collector and emitter of the drive circuit to be controlled and the temperature detection line P1 of the thermal shutdown detection circuit are caused by the same leakage current. Therefore, it is possible to cause the drive circuit to generate a thermal shutdown cutoff signal within a leakage current range that does not cause malfunction.

As a result, thermal shutdown can be performed before the drive circuit starts malfunctioning due to leakage current, and the temperature detection for thermal shutdown is
Since the thermal shutdown circuit is caused by leakage current between the emitters, no matter where the thermal shutdown 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, which is the object of temperature detection, is determined by the heat receiving environment of the transistor that performs temperature detection and the temperature environment in which the drive circuit, which is the object of temperature control, is placed. If the heat receiving conditions of the transistor for temperature detection are set large, the entire detected leakage current value can be increased, and if multiple transistors for temperature detection are connected in parallel, a correspondingly larger leakage current can be obtained. It will be done.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment in which a drive circuit having a heat cutoff circuit according to the present invention is applied, and FIG. 2 is a block diagram of another embodiment.

In FIG. 1, l is a thermal shutdown circuit which sends a shutdown signal to the drive circuit 2, which includes a driver stage for driving a motor and an actuator shade, when the temperature exceeds a predetermined level. It acts to stop the operation of the drive circuit 2 by sending out the signal.

The drive circuit 2 here is a circuit that drives the DC motor M, and includes a plurality of parallel-connected NPN transistors Q/21 Q/29 connected in series to the coil of the I)C motor M.・is acting as its driver. l depending on the driving operation of this driver.
) The current value of the C motor M is determined, and the rotation speed or torque thereof is controlled.

Multiple transistors Q/2°Q/2 connected in parallel
．． The base of ... is commonly the person of drive circuit 2,
It is connected to the power terminal 2a and is controlled by receiving the output of the motor drive control circuit 3.

The thermal shutdown circuit 1 includes parallel-connected temperature detection PNP transistors Q1, Q2, . Q3. @
..., and each base of each PNP transistor for temperature detection is in an open state without being connected to other circuits.

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

NPN) transistor Qlθ is an NPN transistor Q
A transistor connected in a current mirror with P
NP transistor Qt + Q2 + Q3.

- Detects the leakage current between the collector and emitter of N
The PN transistor QII is driven to generate a cutoff signal on its collector side, which is taken out from the output terminal 1a. When this output signal reaches a predetermined temperature state, it is output to the input terminal P2a of the drive circuit 2 to be thermally shut down, and the operation of the drive circuit 2 is stopped.

Here, PNP) transistor Qt + Q2t Q31
. . are usually integrated around the drive circuit 2 that is subject to thermal shutdown, and the NPN transistors Qto and Qtt are also formed in the same chip as the drive circuit 2. Therefore, when the drive circuit 2 or the entire IC chip including this circuit is 5 m long, the PNP) transistors Ql, Q2 . Q3. Leakage current 1l-I between the collector and emitter of each of...
2113, fist-... occurs, which increases exponentially as the temperature of the IC chip increases, and each PNP) transistor Ql, Q2. Q3. Sum of leakage currents I
=Σ11+12+13+... is further amplified by the current mirror circuit, and turns on the NPN) transistor Qll.
Let NPN transistor Q121Q 12 *
... is set to the "OFF" state.

In this case, for example, when a PNP transistor is used, even if the leakage current is about 180 degrees 1 and about several tens of microamperes, multiple transistors are arranged to generate leakage current for temperature detection. By doing this, it is possible to obtain up to about 100 microamperes, and furthermore, by amplifying and detecting this with a current mirror circuit, a cutoff signal can be generated.

Therefore, assuming that the current value of the malfunction due to the leakage current between the collector and emitter of the NPN transistor Q/2 for driving the drive circuit 2 is Is, the PNP transistor Q* * that detects the temperature based on the leakage current. Q
Since the base of 2t Qa* is open with respect to the driving transistor Q12 of the drive circuit 2, a cutoff signal can be generated with a current value of less than Is in the relationship llll5, and the drive circuit 2 It is possible to stop the operation before it malfunctions. Note that due to the structure of the transistor, the temperature at which leakage occurs is lower in a PNP type transistor than in an NPN type transistor, so it is easier to detect temperature when a PNP transistor is used as the transistor to be detected.

In the above case, a PNP that detects temperature by leakage current
) Transistor Q* * Q2 * Qa s...
By connecting multiple transistors in parallel, variations in the leakage current of these transistors are absorbed, and variations in the operating point of temperature detection are suppressed, allowing highly accurate temperature detection.

Here, when detecting the temperature of the entire IC chip and generating a cutoff signal, each PNP) transistor Ql,
Q2. Q3S... 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 the output of the NPN transistor Q// can be used as a temperature detection signal in an external circuit.
It is J-Noh.

FIG. 2 shows the operation-control terminal 3a of the motor drive control circuit 3.
This is an embodiment in which a cutoff signal is applied to the NPN transistor Qn, and the driving force of the NPN transistor Qn is small (although the operation of the drive circuit 2 can be easily stopped).

As explained above, in the embodiment, a plurality of transistors Ql, Q2*Qa, ... are connected in parallel, and the temperature is detected by the sum of their leakage current values. Transistor Qs to detect
Only one transistor may be used, or if a plurality of transistors are provided, either the logical sum condition or logical product condition of the leakage currents of each transistor may be adopted to generate the thermal shutdown cutoff signal. . Further, the logical sum condition and the logical product condition are based on the temperature detection transistor Q* * Q2. which generates the leakage current shown in FIG. This can be easily realized by changing the connection form of transistors such as Qa, and can be made into an AND or an OR depending on the setting conditions of the operating points of the transistors Qm* and Qn.

In the embodiment, a drive circuit for driving a motor is described, but the present invention is not limited to a drive circuit for driving a motor. Can be applied to many other drive circuits.

Further, the transistor for detecting leakage current between the collector and emitter for temperature detection may be a PNP transistor or an NPN transistor. moreover,
Although the base of each transistor is in an open state, it may not be completely open and may be connected at a very high impedance.

[Effects of the Invention] As can be understood from the explanation in J- below, in this invention, thermal shutdown at a predetermined temperature is achieved by applying a voltage between the collector and emitter of a transistor and detecting its leakage current. As a result, the malfunction condition due to leakage current between the collector and emitter of the drive circuit that is subject to thermal shutdown control and the temperature detection condition of the thermal shutdown detection circuit are the same due to leakage current. It turns out. Therefore, it is possible to generate a thermal shutdown cutoff signal within a leakage current range that does not cause malfunctions in the drive circuit.

As a result, thermal shutdown can be performed before the drive circuit starts malfunctioning due to leakage current, and the temperature detection for thermal shutdown is
Since the thermal shutdown circuit is caused by leakage current between the emitters, no matter where the thermal shutdown circuit is placed, only heat transfer needs to be considered, and the layout can be done relatively freely.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment in which a drive circuit having a heat cutoff circuit according to the present invention is applied, Fig. 2 is a block diagram of another embodiment thereof, and Fig. 3 is a block diagram of a conventional thermal cutoff circuit. FIG. 2 is a block diagram of a shutdown circuit. ■... Thermal shutdown circuit, 2... Drive circuit, 3... Motor drive control circuit, Ql, Q2.
Q3... PNP transistor for temperature detection, Qto,
Qtt, Ql2...-NPN) transistor.

Claims (2)

[Claims] (1) In a drive circuit having a heat cutoff circuit, the drive circuit and the heat cutoff circuit are integrated into one chip, and the heat cutoff circuit includes a transistor whose base side is open or connected to a very high impedance. By applying a voltage between the collector and emitter and detecting the leakage current between the collector and emitter, a cutoff signal is generated in a predetermined temperature state, and this cutoff signal is supplied to the drive circuit and the A drive circuit having a thermal cutoff circuit characterized in that the operation of the circuit is stopped. (2) In a drive circuit having a heat cutoff circuit, the drive circuit, a drive signal generation circuit that generates a signal for driving the drive circuit, and the heat cutoff circuit are integrated into one chip, and the heat cutoff circuit is integrated into one chip. , a voltage is applied between the collector and emitter of a transistor whose base side is open or connected to a very high impedance, and this collector
A cutoff signal is generated in a predetermined temperature state by detecting leakage current between emitters, and the cutoff signal is supplied to the drive signal generation circuit to stop the operation of the drive circuit. A drive circuit with a thermal cutoff circuit.