JP2676762B2 - Power semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power semiconductor device having a function of protecting from an abnormal temperature, which controls a current supplied to a load used with high power, for example.

[Prior Art] A power semiconductor device includes a power element that controls a current supplied to a load, and a load current flows through the power element. Therefore, the power element generates heat corresponding to the amount of load current. And, for example, in the event of a failure such as a load short circuit,
A large current will flow through this power element, and the temperature of this power element will rise excessively.

If the temperature of the power element rises abnormally in this way, not only this power element but also other semiconductor elements integrally formed with this power element or peripheral devices will be destroyed. Therefore, in such a power element, it is necessary to have a protective function of interrupting the load current, for example, when the temperature rises abnormally.

The protection function of such a power element is conventionally set in a peripheral circuit, but recently, a circuit for detecting an abnormal state and a protection operation which is operated in response to the abnormal detection, etc. Is considered to be built in the same chip as the power element for electric power. The miniaturization, low cost, and further reliability are improved.

The power semiconductor device with such a protection function is
For example, it is configured as shown in FIG.
Power element 1 composed of channel power MOS
1, the current from the power source 12 is supplied to the load 13 via the power element 11.

The drive signal from the NAND circuit 14 is supplied to the gate of the power element 11, and the gate drive circuit 15 is supplied to the NAND circuit 14.
The pulse-shaped drive signal whose duty is controlled by the signal from the comparator and the signal from the comparison circuit 16 are supplied. That is,
When the output signal from the comparison circuit 16 is at a high level and the pulsed drive signal from the drive circuit 15 is inverted in polarity, it is supplied to the gate of the power element 11 to be on / off controlled. The comparison circuit 16 is supplied with the reference voltage signal at the point A divided by the resistance circuit and the voltage signal at the point B which is the terminal voltage of the temperature detecting diode 17.

Here, the temperature detection diode 17 is a power element.
It is formed on the same semiconductor chip as 11, and when a large current flows through the power element 11 and the power element 11 generates heat to heat the semiconductor chip, the point B corresponds to the temperature rise of the semiconductor chip. The potential of can be lowered.
Then, when the temperature of the semiconductor chip is in a normal state, the voltage at the point B is set higher than the voltage at the point A, the output signal from the comparison circuit 16 is set to the high level, and the gate drive circuit 15 The power element 11 is controlled by the output signal of, and the load 13 is controlled. On the other hand, when the temperature of the semiconductor chip rises, the voltage at the point B lowers as the temperature rises, and when the temperature of the chip becomes abnormal, the voltage at the point B becomes lower than the voltage at the point A. Then, the output signal from the comparison circuit 16 becomes low level.
Therefore, in this state, the output signal from the NAND circuit 14 is fixed to the high level, and the p-channel MOS
The power element 11 consisting of is turned off to cut off the load current, and this semiconductor element is protected from heat generation due to overcurrent.

However, in the semiconductor device configured as described above, the temperature of the heat generating portion and the temperature of the detecting portion do not always match due to the heat conduction relationship between the power element 11 and the temperature detecting element 17 which generate heat. For example, assuming that a short circuit occurs in the load 13 and a large current transiently flows in the power element 11 and the temperature of the power element 11 suddenly rises, it is formed at a position different from that of the power element 11. The temperature rise of the temperature detection element 17 that follows becomes impossible to follow. That is, there is a temperature difference of about 50 ° C. between the temperature of the power element 11 part and the temperature of the temperature detection element 17 part.
Therefore, even if the protection temperature is set to, for example, 150 ° C., the protection operation will be executed when the junction temperature of the power element 11 is 200 ° C., and the protection function of the element will not be surely exhibited. .

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and particularly in an operating state in which a current is flowing through a power element section for controlling a load current, the temperature of the power element section is reduced. A power semiconductor equipped with a protection function that ensures that the element can be protected from heating even if the temperature rises transiently due to a sudden increase in load current by performing a corresponding protection operation. It is intended to provide a device.

[Means for Solving the Problems] That is, in the power semiconductor device according to the present invention, it is controlled in common with the power element for controlling the load so that a current proportional to the current flowing through the power element flows. In addition to providing the control element, the temperature detection signal from the temperature detection element formed on the semiconductor chip common to the power element and the reference signal corresponding to the set reference temperature are compared, and the detected temperature is the reference temperature. The power element is controlled to be turned off in a state in which the power is exceeded. Then, at least one of the temperature detection signal and the reference signal is corrected by the amount of current flowing through the control element.

[Operation] In the power semiconductor device as described above, the power element is basically turned off when the temperature of the semiconductor chip on which the power element is set rises above the set reference temperature. So that the protection operation from overheating is performed. When such a protection operation is performed, a current proportional to the current flowing through the power element is detected by the control element, and the current obtained from this control element corrects, for example, the reference signal, The set reference temperature is increased. Therefore,
When the temperature of the power element section transiently rises when the load current flows through the power element, the temperature difference between the power element section and the temperature detection section is compensated, and the load current increases rapidly. At this time, the protection operation is performed by surely coping with this.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of a power semiconductor device having a protection function, which includes a power element 21 composed of a p-channel MOS. This power element 21 is
It is set between the power supply and the load 22, and supplies current to the load 22 in the ON state. Further, the control element 23 is provided on the same semiconductor chip by the same p-channel MOS as the power element 21, and the power element 21 and the control element 23 are gate-controlled by the output signal from the NAND circuit 24. When the output from the NAND circuit 24 is at low level, both are on-controlled.

The NAND circuit 24 is supplied with the output signal from the comparison circuit 25 and the drive signal from the gate drive circuit 26. From the gate drive circuit 26, for example, a duty-controlled pulsed signal is generated. I am trying to do it.
Therefore, when the output signal from the comparison circuit 25 is at a high level, the output pulse signal from the gate drive circuit 26 is inverted in polarity and output from the NAND circuit 24, and this signal is output from the power element 21 and the control element. It will be supplied to each of the 23 gates.

The negative terminal of the comparison circuit is connected to the resistance of the reference voltage setting unit 27 composed of a voltage divider circuit composed of resistors R1 and R2.
The reference voltage signal at the point A, which is the connection point between R1 and R2, is supplied via the resistor R3. Then, the control element 23
The current obtained when is on is supplied to the negative terminal of the comparison circuit 25 through the backflow prevention diode 28 as an element for correcting the reference voltage.

Further, the positive terminal of the comparison circuit 25 is adapted to be supplied with the terminal B terminal voltage of the temperature detecting element 29 constituted by connecting a plurality of diodes in series.
Is connected to the power supply line via a resistor R4. Here, the diode forming the temperature detecting element 29 is formed so as to be built in the semiconductor chip in which the power element 21 is formed, and a large current flows through the power element 21 to generate heat,
When the temperature of the semiconductor substrate rises due to this heat,
The temperature rise of this semiconductor substrate is detected. Since the diode which constitutes the temperature detecting element 29 has a negative temperature characteristic, when the temperature of the semiconductor chip rises, the point B corresponding to the temperature rises.
Voltage will be reduced.

That is, in the power semiconductor device configured as above, the temperature of the semiconductor chip on which the power element 21 is formed is detected by the voltage at the point B of the temperature detecting element 29,
The voltage at the point B corresponding to the detected temperature is compared by the comparison circuit 25 with the reference voltage set by the reference voltage setting unit 27 having no temperature characteristic.

Here, since the potential at the point B is set to be higher than the voltage at the point A when the temperature of the semiconductor chip is in a normal state, the comparator circuit 25 outputs a high level signal in the normal state of the temperature. Is output, and this high-level signal
It is adapted to be supplied to the NAND circuit 24 as a gate signal. Therefore, the pulsed drive signal from the gate drive circuit 26 is inverted in polarity and supplied to the power element 21, and the load 22 is controlled.

When the temperature of the semiconductor chip rises, the voltage at the point B decreases corresponding to this temperature, and when the voltage at the point B becomes lower than the voltage at the point A which is the reference voltage, the output of the comparison circuit 25 becomes high level. Changes to low level. That is,
The gate signal of the NAND circuit 24 is fixed at a low level, and the output signal from the NAND circuit 24 is fixed at a high level.
23 is turned off, the load current to the load 22 is cut off, and the abnormal temperature rise of the semiconductor chip due to the overcurrent is prevented.

That is, basically, the protection operation as described above is performed, but in the power semiconductor device shown in this embodiment, the control element 23 similar to the power element 21 is used. The gate of the control element 23 is commonly connected to the gate of the power element 21. Therefore, in the control element 23, the current flowing in the power element 21 is detected, a current proportional to the current flowing in the power element 21 flows in the control element 23, and this current passes through the diode 28. It flows into the potential portion of A.

Therefore, the current flowing through the control element 23 raises the voltage level at the point A, that is, the potential of the negative side input of the comparison circuit 25, and the temperature of the power element 21 portion of the semiconductor chip and the temperature detection element 29. The temperature difference from the temperature of the part will be corrected.

That is, in this power semiconductor device, the reference voltage supplied to the comparison circuit 25 that performs a protection operation from overheating in a state in which the load current flows through the power element 21,
The load current is changed according to the load current amount, and the temperature difference between the power element 21 section and the temperature detection element 29 section is canceled on the circuit.

Therefore, during the operation of the load 22, a failure such as a short circuit occurs in the load 22, the load current flowing through the power element 21 rises sharply, and the temperature of the semiconductor chip rises sharply. Sometimes the control element 23
The amount of current flowing through the circuit also rapidly increases, and the reference voltage value supplied to the comparison circuit 25 also increases. Therefore, when the temperature of the semiconductor chip in the power element 21 portion is increased to, for example, 150 ° C. due to the increase in the load current, the temperature of the set portion of the temperature detection element 29 of the semiconductor chip is, for example, 100 ° C.
Even if the temperature rises only up to, since the reference voltage supplied to the comparison circuit 25 is increased by the current from the control element 23, even if the temperature detection element 29 detects that the chip temperature is 100 ° C., The output from the comparison circuit 25 is inverted to low level. Therefore, when the temperature of the power element 21 portion of the semiconductor chip is substantially increased to 150 ° C.,
The current supplied to the load 22 is cut off, and a quick protection operation is executed.

Here, when the load is stopped, no current flows through the control element 23, so the reference voltage is not corrected. Further, in a normal operation state, the amount of current flowing through the control element 23 is limited, and therefore the correction amount of the reference voltage supplied to the comparison circuit 25 is small. Therefore, the normal protection operation is performed in a state close to the temperature of the set portion of the temperature detection element 29 of the semiconductor chip.

FIG. 2 shows another embodiment. In this embodiment, resistors R5 and R6 are connected in series with the control element 23 to correspond to the amount of current flowing from the point C to the control element 23. The voltage is taken out. Then, the voltage signal at the point C is supplied to the comparison circuit 30 to set the comparison voltage Re
Compared with f, the current flowing through the control element 23 increases and C
When the potential at the point starts to drop below the comparison voltage Ref, the comparison circuit 25 is passed through the backflow prevention diode 28.
The correction voltage of the reference voltage is supplied to the negative terminal of the. The other parts are the same as those in the embodiment shown in FIG. 1, and therefore the same reference numerals are given and the description thereof is omitted.

That is, in this embodiment, when the load current supplied to the load 23 is relatively small, the reference voltage of the comparison circuit 25 for protection operation is not corrected and the power element 21
The reference voltage value of the comparison circuit 25 is corrected only when the load current flowing in the circuit is abnormally increased.

In the above embodiment, the p-channel MOS is used as the power element 21,
This can be similarly implemented by using an n-channel MOS, and can be similarly implemented not only by the power MOS but also by a bipolar transistor.

Further, the temperature detecting element 29 part is configured by connecting a plurality of diodes having a temperature characteristic in series in the embodiment, but this can be appropriately configured by having a temperature characteristic. It can also be configured using different resistance ratios, potentials in the bandgap circuit, Zener diode voltage, and the like. Further, when a power element controlled by direct current drive is used, the temperature difference becomes considerably small, but in this case, only the excessive current was detected as shown in the embodiment of FIG. 2, and this excessive current was detected. Only at that time, the reference voltage of the comparison circuit 25 may be corrected.

In the embodiments so far, the signal corresponding to the current flowing through the control element element 24 is changed to the reference voltage setting section of the comparison circuit 25.
It was supplied to 27 and the reference voltage was corrected. However, the same effect can be obtained even if the object of this correction is the temperature detection signal.

FIG. 3 shows an embodiment thereof, which is basically the first
The configuration is similar to that of the embodiment shown in the figure, but the temperature detecting element 29 is connected to the power source, and the temperature detecting element 29 is connected to the resistor R7.
It is designed to be grounded via. The temperature detecting element 29, the resistor R7 and the connection point B are connected to the negative side input of the comparison circuit 25 via the resistor R8. And the control element
The current from 23 is supplied to the negative side input of the comparison circuit 25 via the diode 28 to correct the temperature detection signal.

That is, in this semiconductor device, the potential at the point B changes in accordance with the temperature of the semiconductor chip, and as the temperature of the semiconductor chip increases,
The electric potential at the point B comes to increase. When the temperature of the semiconductor chip is normal, the resistance R1 and
The reference potential at point A set by R2 is set to be lower than the potential at point B. Therefore, in this state, the output from the comparison circuit 25 is at a high level, the power element 21 is on / off controlled in accordance with the output of the gate drive circuit 26, and supplies power to the load 22. In this case, a current corresponding to the current flowing through the power element 23 flows through the control element 23 to correct the temperature detection signal.

When a large current flows in the load 22, a large current also flows in the control element 23, and a temperature detection signal higher than the temperature actually detected by the temperature detection element 29 is given to the comparison circuit 25. The operation of surely protecting the semiconductor chip from overheating is performed.

[Advantages of the Invention] As described above, in the power semiconductor device according to the present invention, particularly when a transient excessive current flows through the power element, that is, the temperature and temperature of the power element portion of the semiconductor chip. When there is a difference between the temperature of the detection element section and the temperature of the detection element section, the reference voltage of the protection function section that executes the temperature detection operation is corrected according to the amount of current flowing through the power element section. When the temperature of the power element suddenly rises due to the increase in the current, the temperature detecting operation of the semiconductor chip is properly performed. Therefore, this semiconductor device is effectively protected from thermal damage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a power semiconductor device according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing a circuit configuration of another embodiment of the present invention, and FIG. It is a figure which shows the circuit structure of the conventional power semiconductor device. 21 ... Power element, 22 ... Load, 23 ... Control element, 24 ...
… NAND circuit, 25 …… Comparison circuit, 27 …… Reference voltage setting section,
29 …… Temperature detection element.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H03K 17/08 9447-4M H01L 29/78 657G 17/14

Claims (1)

(57) [Claims] 1. A power element for supplying operating power to a load, and a temperature detecting element formed on the same semiconductor chip as the power element and generating an electric signal corresponding to the temperature of the semiconductor chip. A reference signal generating means for generating a reference signal corresponding to the reference temperature to be compared with the detection signal obtained from the temperature detection element and the reference signal, and the temperature of the semiconductor chip is higher than the reference temperature. The detection signal based on the comparison means for detecting, a control element that is commonly gate-controlled with the power element, and a current that flows through the control element in response to a load current flowing through the power element. And a means for correcting at least one of the reference signals, and the power output is off-controlled by the detection output from the comparing means. A power semiconductor device and butterflies.