JP4920305B2 - Overheat detection circuit and semiconductor device and electronic apparatus incorporating the overheat detection circuit - Google Patents

Description

  The present invention relates to an overheat detection circuit for detecting the temperature of a semiconductor chip to perform overheat protection, in particular, an overheat detection circuit having high detection sensitivity and useful for a semiconductor device using a MOS transistor, and the overheat detection circuit The present invention relates to a semiconductor device incorporating a semiconductor device and an electronic apparatus incorporating the semiconductor device.

  In semiconductor devices with built-in power transistors used in constant voltage circuits, motor drive circuits, lighting control circuits, etc., there is a failure such as the generation of heat when a large current flows through the power transistors, destroying the power transistors May occur. Conventionally, a current limiting circuit is provided to limit the current flowing through the power transistor, thereby suppressing heat generation to a predetermined value or less.

  However, since the temperature of the semiconductor device is determined by the consumed power and the ambient temperature, for example, when the ambient temperature is low or when the voltage applied to the power transistor is low, a current of a predetermined value or more is passed through the current limiting circuit. Sometimes you can.

  Conversely, the temperature of the semiconductor device may exceed the maximum rating before the current limiting circuit operates. That is, the protection of the semiconductor device is insufficient with only the current limiting circuit.

  For this reason, conventionally, a temperature sensing element is arranged in the vicinity of the power transistor, and it is detected that the temperature in the vicinity of the power transistor has reached a predetermined temperature, and overcurrent protection is performed by limiting the current of the power transistor. It was.

  An example of a conventional overheat detection circuit for performing such overheat protection is disclosed in Japanese Patent Laid-Open No. 1-175615 (Patent Document 1). FIG. 4 is a block diagram summarized for easy explanation of the thermal protection circuit disclosed as FIG.

  As shown in FIG. 4, the conventional overprotection circuit disclosed in Patent Document 1 includes three constant current sources I11 to I13, a resistor R11, NPN transistors Q1 and Q2, a diode D1, and inverter circuits 11 and 12. Has been. In FIG. 4 of Patent Document 1, the constant current sources I11 to I13 are formed of a current mirror circuit using PNP transistors, and supply a proportional current value.

  The temperature detection of this thermal protection circuit utilizes the fact that the base-emitter voltage of the NPN transistor Q1 varies with temperature. In general, a base-emitter voltage of a transistor has a negative temperature characteristic of −2 mV to −3 mV / ° C.

  Since the constant current is supplied from the constant current source I11 to the resistor R11, the voltage VB across the resistor R11 is a constant voltage. Since the current source I11 and the resistor R11 do not have temperature characteristics, the voltage VB does not change with respect to temperature.

  The values of the current source I11 and the resistor R11 are appropriately selected, and the value of the voltage VB is set to a voltage slightly lower than the base-emitter voltage of the NPN transistor Q1 at normal temperature.

  In this configuration, as the temperature increases, the base-emitter voltage of the NPN transistor Q1 has a negative temperature characteristic (−2 mV to −3 mV / ° C.), and thus decreases.

  As a result, when the base-emitter voltage of the NPN transistor Q1 becomes lower than the voltage VB, the base current of the NPN transistor Q1 flows out and the NPN transistor Q1 is turned on. This signal is output to the output terminal Vo through the inverter circuits 11 and 12.

  Since the NPN transistor Q2 is on when the NPN transistor Q1 is off, the anode potential of the diode D11 is lowered to the ground potential GND. Since the voltage VB is connected to the cathode of the diode D11, the diode D11 is off.

  When the NPN transistor Q1 is turned on, the base potential of the NPN transistor Q2 is lowered and the NPN transistor Q2 is turned off. Therefore, the potential on the anode side of the diode D11 becomes equal to or higher than the voltage VB, and the diode D11 is turned on. Then, since the current of the current source I13 is supplied to the resistor R11, the voltage VB rises and promotes the turning on of the NPN transistor Q1.

  When the temperature drops from this state, the voltage VB is higher than before, so the NPN transistor Q1 cannot be turned off until the temperature becomes lower than the temperature when the NPN transistor Q1 is turned on. That is, the current source I13, the diode D11, and the NPN transistor Q2 function to provide hysteresis for temperature detection.

JP-A-1-175615

  However, the thermal protection circuit uses the voltage drop VB of the resistor R11 when the current of the current source I11 flows through the resistor R11 as the reference voltage of the detected temperature, and the temperature of the base-emitter voltage of the NPN transistor Q1 for temperature detection. Since the temperature rises and the base-emitter voltage of the NPN transistor Q1 decreases and approaches the voltage VB, a part of the current of the current source I11 becomes the base current of the NPN transistor Q1. As a result, the current flowing through the resistor R11 decreases.

  Then, since the voltage drop of the resistor R11 is reduced, the voltage VB is also reduced, so that the temperature at which the NPN transistor Q1 is reliably turned on varies due to a change in the current amplification factor of the NPN transistor Q1. .

  In other words, near the detection temperature, the reference voltage VB decreases due to the influence of the base current of the NPN transistor Q1, and therefore the temperature characteristic of the base-emitter voltage of the transistor changes from −2 mV to −3 mV / ° C. Since it becomes the same result as having become small, temperature detection sensitivity will fall.

  The present invention has been made in consideration of the above-described circumstances, and has an overheat detection circuit and a overheat detection circuit that have high temperature detection sensitivity, can reduce the number of elements, and can occupy a small area in a semiconductor chip. An object is to provide a built-in semiconductor device and electronic device.

  The present invention has the following configuration in order to solve the above-described problems. Hereinafter, the configuration and effects of each claim will be described. Reference numerals shown in parentheses are the references shown in FIG. 1 (first embodiment) and FIG. 3 (second embodiment) in order to clarify the correspondence between the structure of each claim and the embodiments. Although it is a code | symbol, it cannot be overemphasized that this invention is not limited to the structure of the Example described in this specification, and extends to the range which those skilled in the art can easily guess from a well-known technique.

a) In claim 1, in the overheat detection circuit for detecting the temperature of the semiconductor device and performing overheat protection, the resistor (R1) provided between the first voltage power supply and the second voltage power supply for applying a constant voltage , R2), a temperature detecting diode (D1) and a constant current source (I1), and a first MOS transistor (M1) provided between the first voltage power source and the second voltage power source. The voltage across the constant current source (I1) is the gate-source voltage of the first MOS transistor (M1) constituting the inverter. With this configuration, the temperature detection sensitivity is increased, and high-precision overheat detection is possible.

b) The invention according to claim 2 is the overheat detection circuit according to claim 1, wherein the resistor is composed of a plurality of resistors (R1, R2) connected in series, and at least one of the plurality of resistors. When the switching means (M3) is connected in parallel to (R1) and the first MOS transistor (M1) is turned on, the switching means (M3) is turned on and connected in parallel to the switching means (M3). It is characterized in that the resistor (R1) is short-circuited. With this configuration, it is possible to add hysteresis to the detected temperature, and stable operation is possible.

c) According to a third aspect of the present invention, in the overheat detection circuit according to the second aspect, at least one of the plurality of resistors (R2) is capable of adjusting a resistance value by trimming. With this configuration, variations in the manufacturing process can be corrected, and high-precision overheat detection can be performed.

d) The invention according to claim 4 is the overheat detection circuit according to any one of claims 1 to 3, wherein the load of the first MOS transistor (M1) constituting the inverter is a constant current load. According to a fifth aspect of the present invention, there is provided a constant voltage power supply circuit (R3 to which a constant voltage is applied) provided between the first voltage power supply (Vdd) and the second voltage power supply (GND). R4 resistance series circuit), and the constant current load includes a second MOS transistor (M2) to which a constant voltage obtained from the resistance series circuit (R3, R4) is applied to the gate. It is a feature. With this configuration, the gain of the inverter circuit can be increased and the detection sensitivity can be increased.

e) The invention according to claim 6 is a semiconductor device including the overheat detection circuit according to any one of claims 1 to 5, and the invention according to claim 7 includes the semiconductor device. Electronic equipment. The electronic device here is particularly effective when applied to a small electronic device such as a mobile phone, a video camera, a digital camera, or a portable audio device.

  To describe the general effect of the present invention, the present invention compares the voltage (V1) having a positive temperature characteristic with the threshold voltage (Vth) of a MOS transistor (M1) having a negative temperature characteristic. By doing so, the sensitivity of temperature detection became extremely high, and high-precision overheat detection became possible.

  Further, the inverter circuit is configured by the temperature detection MOS transistor (M1), and the current source (R3, R4, M2) is used as the load of the transistor, so that the gain of the inverter circuit can be increased, and the sensitivity is further increased. It became possible to improve.

  Furthermore, since a hysteresis width is provided for temperature detection by providing the switching element (M3), stable overheat detection can be performed.

  Furthermore, since all the active elements of the overheat detection circuit are composed of MOS transistors (M1, M2, M3), it is suitable for the MOS process which is the mainstream of the latest semiconductors.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an overheat detection circuit diagram showing a first embodiment of the present invention.

  As shown in the figure, the overheat detection circuit 10 according to this embodiment includes an NMOS transistor M1, PMOS transistors M2 and M3, a diode D1, a current source I1, resistors R1 to R4, and inverter circuits 11 and 12. A constant voltage Vdd (first voltage power supply) is used as a power supply other than at least the inverter circuits 11 and 12.

  The diode D1 is a temperature detection element. A resistor R1, a resistor R2, and a current source I1 are connected in series to the diode D1, and this series circuit is connected between a constant voltage Vdd (first voltage power supply) and a ground potential GND (second voltage power supply). ing.

  The source of the NMOS transistor M1 is connected to the ground potential GND (second voltage power supply), and the gate is connected to the intersection of the diode D1 and the current source I1. Further, since the other end of the current source I1 is connected to the ground potential GND (second voltage power supply), the voltage across the current source I1 is applied between the gate and source of the NMOS transistor M1. Become.

  The drain of the NMOS transistor M1 is connected to the constant voltage Vdd (first voltage power supply) via the PMOS transistor M2. The gate of the PMOS transistor M2 is connected in series to the intersection of a resistor R3 and a resistor R4 connected to a constant voltage Vdd (first voltage power supply) and a ground potential GND (second voltage power supply).

  The drain of the NMOS transistor M1 is further connected to the input of the inverter circuit 11, the output of the inverter circuit 11 is connected to the input of the inverter circuit 12, and the output of the inverter circuit 12 is the output Vo of the overheat detection circuit 10.

  The output of the inverter circuit 12 is further connected to the gate of the PMOS transistor M3. The source of the PMOS transistor M3 is connected to the constant voltage Vdd, and the drain is connected to the intersection of the resistors R1 and R2. That is, it is connected in parallel to the resistor R1.

  The resistor R2 has a configuration capable of trimming, and the variation in the detected temperature caused by the variation in the manufacturing process is corrected by changing the resistance value of the resistor R2.

  FIG. 2 is a timing chart for explaining the circuit operation of the first embodiment of the present invention, and shows the relationship between the threshold voltage (Vth) of the NMOS transistor M1 and the voltage V1 which is the gate voltage of the NMOS transistor M1. .

Next, the circuit operation of FIG. 1 will be described with reference to the timing chart of FIG.
Since the diode D1 has a negative temperature characteristic of −2 mV to −3 mV / ° C., the voltage V1 across the current source I1 increases as the temperature increases. That is, the voltage V1 has a positive temperature characteristic of +2 mV to +3 mV (see “V1 before detecting overheating” in FIG. 2).

  The values of the resistors R1 and R2 and the current value of the current source I1 are set so that the voltage V1 is lower than the threshold voltage (Vth) of the NMOS transistor M1 at room temperature.

  Since the temperature characteristic of the threshold voltage (Vth) of the NMOS transistor M1 also has a negative temperature characteristic of −several mV, the threshold voltage (Vth) of the NMOS transistor M1 decreases as the temperature rises (“Vth of M1” in FIG. 2). "reference).

  When the temperature rises and overheat detection is performed, the detected temperature is the point (point A) where the threshold voltage (Vth) of the NMOS transistor M1 crosses “V1 before overheat detection” shown by the solid line in FIG. .

  When the detection temperature is reached, the NMOS transistor M1 is turned on, so that the drain voltage decreases. The voltage is output from the output terminal Vo via the inverter circuits 11 and 12.

  When the drain voltage of the NMOS transistor M1 decreases and the output of the inverter circuit 12 decreases, the gate voltage of the PMOS transistor M3 decreases, so the PMOS transistor M3 is turned on and the resistor R1 is short-circuited. Then, the voltage V1 rises and jumps to the point B in FIG.

  When the temperature decreases, the voltage V1 moves from the upper right to the lower left on the “V1 after overheating detection” line indicated by a broken line in FIG. The threshold voltage (Vth) of the NMOS transistor M1 increases as the temperature decreases. When the temperature drops to a certain temperature, the voltage V1 and the threshold voltage (Vth) of the NMOS transistor M1 cross again at the point C. This temperature is the return temperature.

  Below this temperature, the NMOS transistor M1 is turned off and the drain voltage rises. The output is output from the output terminal Vo via the inverter circuits 11 and 12.

  When the drain voltage of the NMOS transistor M1 rises and the output of the inverter circuit 12 becomes high level, the PMOS transistor M3 is turned off and the short circuit of the resistor R1 is released, so that the voltage V1 is lowered and the point D in FIG. Jump to. In this way, the detected temperature is given hysteresis.

  Since the voltage obtained by dividing the constant voltage Vdd by the resistors R3 and R4 is applied to the gate of the PMOS transistor M2, the PMOS transistor M2 functions as a constant current load of the NMOS transistor M1. That is, the NMOS transistor M1 and the PMOS transistor M2 constitute an inverter circuit, and the NMOS transistor M1 obtains a high gain by using the PMOS transistor M2 as a constant current load.

  As described above, in the present invention, since the voltage V1 having the positive temperature characteristic and the threshold voltage (Vth) of the NMOS transistor M1 having the negative temperature characteristic are compared, the temperature detection is performed. The sensitivity of the sensor has become extremely high, and high-precision overheat detection has become possible.

  In addition, since the current load by the PMOS transistor M2 is configured as the load of the NMOS transistor M1, the gain of the inverter circuit configured by the NMOS transistor M1 and the PMOS transistor M2 can be increased, and the detection sensitivity can be further increased. It was.

  Further, since hysteresis is provided for temperature detection by the PMOS transistor M3, stable overheat detection can be performed.

  Furthermore, since all the active elements of the overheat detection circuit are composed of MOS transistors, the circuit is suitable for the latest semiconductor devices.

FIG. 3 is an overheat detection circuit diagram showing a second embodiment of the present invention.
The overheat detection circuit of FIG. 3 is different from the overheat detection circuit of FIG. 1 according to the first embodiment in that the circuit configuration is changed to the constant voltage Vdd side and the ground potential GND side by reversing the channel configuration of the MOS transistor. Are all reversed. The operation is the same as that described with reference to FIGS.

  In addition, by incorporating the overheat detection circuit according to the above-described embodiment into a semiconductor device or electronic device having a built-in power transistor, it is possible to prevent the semiconductor device or electronic device from being destroyed due to overheating.

It is a block diagram of the overheat detection circuit which shows the 1st Example of this invention. It is a figure for demonstrating the circuit operation | movement of 1st Example of this invention. It is a block diagram of the overheat detection circuit which shows the 2nd Example of this invention. It is a figure which shows the example of the overheat detection circuit for performing the conventional overheat protection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Overheat detection circuit 11,12: Inverter circuit M1: NMOS transistor M2, M3: PMOS transistor D1, D11: Diode R1-R4, R11: Resistor Q1, Q2: NPN transistor I1: Current source I11-I13: Constant current source Vdd: constant voltage (first voltage power supply)
GND: Ground potential (second voltage power supply)
V1, VA, VB: Voltage Vo: Output Vth: Threshold voltage

Claims (7)

In the overheat detection circuit to detect the temperature of the semiconductor device and perform overheat protection,
A series circuit of a resistor, a temperature detection diode, and a constant current source provided between a first voltage power source and a second voltage power source for applying a constant voltage ;
An inverter including a first MOS transistor provided between the first voltage power source and the second voltage power source;
The overheat detection circuit according to claim 1, wherein the voltage across the constant current source is a gate-source voltage of the first MOS transistor constituting the inverter. The overheat detection circuit according to claim 1,
The resistor is composed of a plurality of resistors connected in series,
Switching means is connected in parallel to at least one of the plurality of resistors,
An overheat detection circuit, wherein when the first MOS transistor is turned on, the switching means is turned on to short-circuit a resistor connected in parallel to the switching means. The overheat detection circuit according to claim 2,
An overheat detection circuit, wherein a resistance value of at least one of the plurality of resistors can be adjusted by trimming. In the overheat detection circuit in any one of Claim 1 to 3,
The overheat detection circuit, wherein the load of the first MOS transistor constituting the inverter is a constant current load. The overheat detection circuit according to claim 4,
A resistor series circuit provided between the first voltage power source and the second voltage power source to which the constant voltage is applied;
The overheat detection circuit according to claim 1, wherein the constant current load comprises a second MOS transistor to which a constant voltage obtained from the resistor series circuit is applied to a gate.   A semiconductor device comprising the overheat detection circuit according to claim 1.   An electronic apparatus comprising the semiconductor device according to claim 6.

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