JP5293083B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device provided with an overheat protection circuit.

An overheat protection circuit that protects semiconductor elements such as power transistors and power MOSFETs from an overheated state is used. The overheat protection device described in Patent Document 1 detects the temperature of the switching module, calculates the temperature change rate corresponding to the value of the current supplied to the load of the switching element built in the switching module, and these The internal temperature of the switching module is estimated based on the detected temperature and the calculated value of the temperature change rate. Then, the target current value used for the current control of the switching element is corrected based on the estimated value. Moreover, the inverter apparatus described in patent document 2 restrict | limits electricity supply of a switching element based on the temperature signal according to the temperature of the switching element of an inverter circuit, and the current signal according to a motor current.
Japanese Patent Laid-Open No. 10-337084 Japanese Patent Laid-Open No. 11-341884

  FIG. 6 shows a conventional configuration of the overheat detection circuit. The IC 1 is formed with a MOSFET 2 and a temperature detecting diode 3 located in the vicinity thereof. The constant current circuit 4 supplies a constant current to the diode 3, and the resistors 5 and 6 divide the reference voltage Vc between the pair of voltage lines 7 and 8 to generate a threshold voltage Vth. The comparator 9 compares the forward voltage Vf of the diode 3 with the threshold voltage Vth and outputs an overheat detection signal. The on / off command signal for the MOSFET 2 is gated by the overheat detection signal in the AND gate 10 and then given to the gate of the MOSFET 2.

  When the size of the protected element MOSFET 2 is large, even if the diode 3 is disposed adjacent to the MOSFET 2, it takes time for the heat generated in each part of the MOSFET 2 to propagate through the chip and reach the diode 3. Therefore, for example, even if the load RL is short-circuited and a large current flows and the temperature of the MOSFET 2 suddenly rises, the gate of the MOSFET 2 can be shut off only after the heat propagation delay time has elapsed.

  In particular, when the power supply voltage VB is high or the ambient environment temperature of the IC 1 is high, the time from the MOSFET 2 being overheated until it is thermally destroyed is further shortened, and the margin for thermal destruction is reduced. Furthermore, if a high heat dissipation package that escapes the heat generated by the IC 1 to the printed circuit board or the case is adopted, the propagation of heat from the MOSFET 2 to the diode 3 is further delayed. On the other hand, if the threshold voltage Vth is simply increased by a certain value, depending on the operating conditions, on the contrary, there will be too much room for thermal destruction, and load stoppage due to overheat detection will increase and the operating rate will increase. Will be reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor device including an overheat protection circuit that can reliably protect the protected transistor from thermal destruction while suppressing unnecessary overheat detection of the protected transistor. It is to provide.

  In the semiconductor device according to the first aspect, the temperature detection circuit is disposed in the vicinity of the protected transistor. The comparison circuit compares a temperature detection signal having a level corresponding to the temperature of the arrangement position with a threshold signal having a level corresponding to the start temperature of protection control, and the temperature detection signal exceeds the threshold signal. Output an overheat detection signal. The protection control circuit executes protection control of the protected transistor in response to the overheat detection signal.

This semiconductor device includes at least one type of threshold correction circuit that corrects the level of the threshold signal (that is, the start temperature of protection control) to a lower temperature as the protected transistor is more likely to be thermally destroyed . The second threshold correction circuit corrects the level of the threshold signal to a lower temperature as the voltage of the power supply that supplies current to the protected transistor increases. The third threshold value correction circuit corrects the level of the threshold signal to a lower temperature side as the ambient environment temperature becomes higher.

When provided with any one of the second and third threshold voltage compensation circuit, such as when the supply voltage or if ambient temperature low is low, from the occurrence of overheating for the protected transistor to thermal destruction If a relatively long time can be secured (when the thermal breakdown margin is large), keeping the threshold signal level at a relatively high temperature side will make the protected transistor unnecessarily overheated. Can be prevented. Conversely, when only a relatively short time can be secured from the occurrence of an overheating condition to thermal destruction (when the thermal destruction margin is small), the threshold signal level is corrected to a lower temperature and detected. Protection control of the protected transistor is started at an early point when the temperature starts to rise, and the protected transistor is reliably protected from thermal destruction.

  According to the means described in claim 2, the temperature detection circuit is configured to output the forward voltage of the diode, and the threshold value generation circuit divides the constant voltage and outputs the threshold voltage. The threshold correction circuit corrects the threshold voltage level by flowing a current through the voltage dividing resistor through the voltage dividing point of the threshold generating circuit.

According to the means described in claim 3, the first threshold value correction circuit corrects the level of the threshold signal to the lower temperature side as the current flowing through the protected transistor increases. The current detection circuit of the first threshold value correction circuit is configured by a sense transistor in which a protected transistor and a control terminal are connected to each other. When the current flowing through the protected transistor increases, the current output to the voltage dividing point of the threshold generation circuit also increases and the threshold voltage level is corrected.

According to the second threshold value correction circuit described in claim 4, when the power supply voltage for supplying a current to the protected transistor becomes high, the high potential side power supply line is connected to the first current mirror circuit via the resistor. As the flowing current increases, the current output from the second current mirror circuit to the voltage dividing point of the threshold value generation circuit also increases and the threshold voltage level is corrected.

According to the third threshold value correction circuit of the fifth aspect, when the ambient temperature of the semiconductor device rises, the base-emitter voltage of the input-side transistor of the third current mirror circuit is lowered. As the current flowing in the current mirror circuit increases, the current output from the fourth current mirror circuit to the voltage dividing point of the threshold value generation circuit also increases to correct the threshold voltage level.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows the configuration of an overheat detection circuit formed as an IC (semiconductor device), and the same parts as those in FIG. The IC 11 mounted on the electronic control unit of the vehicle incorporates an N-channel type power MOSFET 2 (protected transistor), and a load RL connected between the terminal 12 of the IC 11 and an in-vehicle battery (not shown). (Indicated by a symbol of resistance in the figure) is driven. The IC 11 includes various terminals in addition to the terminal 12 including a power supply terminal, which is omitted in FIG.

  As shown in FIG. 2 which is a partial element layout diagram of the IC 11, a diode 3 as a temperature detection circuit is formed adjacent to the MOSFET 2. The diode 3 is driven with a constant current by the constant current circuit 4 and outputs a temperature detection signal having a voltage level corresponding to the temperature of the arrangement position. As is well known, the forward voltage Vf of the diode 3 has a negative temperature coefficient of -2 mV / ° C. The pair of voltage lines 7 and 8 are supplied with a highly accurate reference voltage Vc having a very small temperature fluctuation rate from a band gap circuit (not shown).

  The threshold generation circuit 13 divides the reference voltage Vc by the voltage dividing resistors 5 and 6 to generate the threshold voltage Vth. The comparator 9 as a comparison circuit compares the forward voltage Vf (temperature detection signal) of the diode 3 with the threshold voltage Vth (threshold signal) and outputs an overheat detection signal. The on / off command signal and overheat detection signal for the MOSFET 2 are input to the AND gate 10, and the output signal is applied to the gate (control terminal) of the MOSFET 2. The protection control here is gate cutoff control for the MOSFET 2.

  The IC 11 further includes first, second, and third threshold correction circuits 14, 15, and 16. The first threshold value correction circuit 14 increases the threshold voltage Vth output from the threshold value generation circuit 13 as the current IL flowing through the MOSFET 2 increases, and corrects the threshold signal level to the low temperature side. It has become. Specifically, the MOSFET 2 is provided with a sense MOSFET 17 whose gate and drain are connected. The source of the MOSFET 17 is connected to a voltage dividing node 19 (voltage dividing point) of the threshold value generating circuit 13 through a backflow preventing diode 18.

  The second threshold correction circuit 15 increases the threshold voltage Vth output from the threshold generation circuit 13 as the power supply voltage VB of the in-vehicle battery that supplies current to the MOSFET 2 increases. The level is corrected to the low temperature side. The second threshold correction circuit 15 includes first and second current mirror circuits 20 and 21, a resistor 22, and a diode 23.

  The transistors 24 and 25 constituting the first current mirror circuit 20 are grounded to the power line 8 on the low potential side of the pair of power lines 26 and 8 having the power supply voltage VB, and the second current mirror circuit 21. Are grounded to the power line 26 on the high potential side. A resistor 22 is connected between the power supply line 26 and the transistor 24, and a collector of the transistor 28 is connected to the voltage dividing node 19 of the threshold value generation circuit 13 through a diode 23 for preventing backflow. .

  The third threshold correction circuit 16 increases the threshold voltage Vth output from the threshold generation circuit 13 as the ambient environment temperature (atmosphere temperature) of the IC 11 becomes higher, and the threshold signal level is lowered. It is supposed to be corrected. The third threshold value correction circuit 16 includes third and fourth current mirror circuits 29 and 30, a resistor 31, and a diode 32.

  The transistors 33 and 34 constituting the third current mirror circuit 29 are grounded to the voltage line 8 on the low potential side of the pair of voltage lines 7 and 8 having the reference voltage Vc, and the fourth current mirror circuit 30. Are grounded to the voltage line 7 on the high potential side. The resistor 31 is connected between the voltage line 7 and the transistor 33, and the collector of the transistor 36 is connected to the voltage dividing node 19 of the threshold value generation circuit 13 through the backflow preventing diode 32. .

Next, the operation and effect of this embodiment will be described with reference to FIGS.
When the temperature at the arrangement position of the diode 3 is lower than the start temperature of protection control, the forward voltage Vf of the diode 3 becomes higher than the threshold voltage Vth. At this time, the comparator 9 outputs an H level overheat detection signal indicating a non-overheat state, and the MOSFET 2 performs a normal on / off operation in accordance with the on / off command signal. On the other hand, when the temperature at the arrangement position of the diode 3 is higher than the start temperature of the protection control, the forward voltage Vf of the diode 3 becomes lower than the threshold voltage Vth. At this time, the comparator 9 outputs an L level overheat detection signal indicating an overheat state, and the MOSFET 2 is protected from the overheat state by entering a current interruption state.

  The threshold voltage Vth used for this overheat protection control is corrected by the first, second, and third threshold correction circuits 14, 15, and 16. (A), (b), and (c) of FIG. 3 show the correction characteristics of the threshold correction circuits 14, 15, and 16, respectively. The correction value on the vertical axis indicates the correction amount of the threshold voltage Vth. In the first threshold correction circuit 14, a current 1 / N times (N> 1) the current IL flowing through the MOSFET 2 flows through the sense MOSFET 17, and the current is used as a correction current I 1 for voltage division via the voltage dividing node 19. It flows through the resistor 6. As a result, the threshold voltage Vth increases in proportion to the current IL flowing through the MOSFET 2.

  In the second threshold correction circuit 15, a current proportional to the power supply voltage VB flows through the resistor 22. For example, when the mirror ratios of the first and second current mirror circuits 20 and 21 are both 1: 1, a correction current I2 equal to (VB−VBE) / R22 flows to the voltage dividing resistor 6 via the voltage dividing node 19. . As a result, the threshold voltage Vth increases in proportion to the power supply voltage VB.

  In the third threshold value correction circuit 16, the base-emitter voltage VBE of the transistor 33 has a temperature characteristic of −2 mV / ° C. For this reason, under the highly accurate reference voltage Vc, the current flowing through the transistor 33 increases in proportion to the temperature of the transistor 33 and flows to the voltage dividing resistor 6 via the voltage dividing node 19. The transistor 33 is arranged as far as possible from the MOSFET 2 so that the influence of heat generation of the MOSFET 2 is reduced. As a result, the temperature of the transistor 33 is close to the ambient temperature of the IC 11 (the ambient temperature of the IC 11), and the threshold voltage Vth increases in proportion to the ambient temperature of the IC 11.

  FIG. 4 shows the overheat detection characteristic of the overheat protection circuit. The horizontal axis represents the temperature related to the detection of the diode 3, and the vertical axis represents the threshold voltage Vth output from the threshold generation circuit 13. A solid line LA is a temperature characteristic of the forward voltage Vf of the diode 3, and a broken line LB indicates two levels having different threshold voltages Vth. As described above, the threshold voltage Vth increases as the current flowing through the MOSFET 2 increases, the power supply voltage VB increases, or the ambient environment temperature (ambient temperature) of the IC 11 increases. When the threshold voltage is changed from Vth1 to Vth2 due to such a change in the situation, the start temperature of the overheat protection control is lowered from T1 to T2, and the overheat protection control is started from a time point when the detected temperature is lower. That is, by providing the threshold correction circuits 14, 15 and 16, the level of the threshold voltage Vth (that is, the start temperature of overheat protection control) is corrected to a lower temperature so that the MOSFET 2 is more likely to be thermally destroyed. When the temperature rises, the control shifts to overheat protection control from an early point.

  According to the present embodiment described above, when the load current IL flowing through the MOSFET 2 is small, when the power supply voltage VB is low, or when the ambient environment temperature is low, the thermal stress of the MOSFET 2 is small, and the heat from the occurrence of the overheated state is reduced. In the case where a relatively long margin time can be secured until breakdown, the threshold voltage Vth can be kept at a relatively high temperature side to prevent the MOSFET 2 from being unnecessarily overheated. Thereby, electricity supply to load RL can be maintained as much as possible. On the other hand, when the thermal stress of the MOSFET 2 is large and only a relatively short margin time can be secured from the occurrence of the overheat state to the thermal breakdown, the threshold voltage Vth is corrected to a lower temperature side. The protection control of the MOSFET 2 is started at an early point when the detected temperature starts to rise. Thereby, MOSFET2 can be reliably protected from thermal destruction.

  The first, second, and third threshold value correction circuits 14, 15, and 16 are the magnitudes of the correction currents I1, I2, and I3 based on the load current IL, the power supply voltage VB, and the ambient environment temperature that are different from each other. To decide. Then, the level of the threshold voltage Vth is corrected by a combined current obtained by adding these correction currents I1, I2, and I3. Therefore, the MOSFET 2 can be widely protected from various factors.

  When the size of the MOSFET 2 is large or a high heat dissipation package is adopted, it takes time for the heat generated in each part of the MOSFET 2 to propagate through the chip and reach the diode 3. According to the present embodiment, the level of the threshold voltage Vth is corrected in accordance with the margin time based on the operation state at that time, thereby controlling the transition timing to the overheat protection control, thereby detecting delay due to propagation delay. Can be avoided in advance.

(Second Embodiment)
FIG. 5 shows a configuration of an overheat detection circuit according to the second embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and only different parts will be described below.
The IC 41 includes a first threshold value correction circuit 42 instead of the first threshold value correction circuit 14 shown in FIG. The first threshold correction circuit 42 includes a resistor 43 provided in series with the MOSFET 2, an amplifier circuit 44 that amplifies the voltage across the resistor 43, and a voltage − that converts the amplified voltage into a current − And a current conversion circuit 45. The voltage-current conversion circuit 45 outputs a current to the voltage dividing node 19 of the threshold value generation circuit 13 via the diode 18.

  The first threshold correction circuit 42 generates a correction current I1 proportional to the current IL flowing through the MOSFET 2 in accordance with the resistance value of the resistor 43, the amplification factor of the amplification circuit 44, and the conversion factor of the voltage-current conversion circuit 45. Output. As a result, the threshold voltage Vth increases in proportion to the current IL flowing through the MOSFET 2. According to this embodiment, the same effect as that of the first embodiment can be obtained. In addition, by adopting the first threshold value correction circuit 42, the proportional relationship between the current IL and the correction current I1 can be maintained with higher accuracy.

(Other embodiments)
The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified or expanded as follows, for example.
The second, third threshold correction circuits 1 5, 16 may be configured to include the two any one or any. Which threshold correction circuit is provided may be appropriately determined based on the power supply voltage VB, load current IL, temperature environment, and the like used in the ICs 11 and 41.

The protected transistor may be a semiconductor element such as a bipolar transistor or IGBT.
The temperature detection circuit is not limited to the one using the forward voltage Vf of the diode, and other temperature detection elements may be used.

The second and third threshold correction circuits 15 and 16 may be constituted by MOSFETs instead of bipolar transistors.
The first to third threshold correction circuits may be configured to correct the level of the threshold voltage Vth by changing the resistance values of the voltage dividing resistors 5 and 6. Alternatively, the first to third threshold correction circuits may be voltage output types, and the output voltages may be added and applied to the voltage dividing node 19 via a resistor. Further, the configuration of the threshold generation circuit is not limited to the resistance voltage dividing circuit.

The overheat protection control of the MOSFET 2 when the overheat detection signal is output is not limited to gate cutoff, and may be current suppression control by gate voltage reduction control.
Hysteresis may be applied to the comparator 9.

The block diagram of the overheat detection circuit which shows the 1st Embodiment of this invention IC partial device layout The figure which shows each correction characteristic of three types of threshold value correction circuits Diagram showing overheat detection characteristics of overheat protection circuit FIG. 1 equivalent diagram showing a second embodiment of the present invention 1 equivalent diagram showing the prior art

Explanation of symbols

  In the drawing, 2 is a MOSFET (protected transistor), 3 is a diode (temperature detection circuit), 5 and 6 are voltage dividing resistors, 7 is a voltage line (high potential side voltage line), 8 is a voltage line, and a power line (low) Potential side voltage line, low potential side power supply line), 9 is a comparator (comparison circuit), 10 is an AND gate (protection control circuit), 11 and 41 are ICs (semiconductor devices), 13 is a threshold generation circuit, 42 is a first threshold correction circuit, 15 is a second threshold correction circuit, 16 is a third threshold correction circuit, 17 is a sense MOSFET (current detection circuit, sense transistor), and 19 is a minute Pressure nodes (voltage dividing points), 20, 21 are first and second current mirror circuits, 22, 31, 43 are resistors, 24, 27, 33, 35 are transistors (input side transistors), 25, 28, 34. , 36 is a transistor (output side Transistor), 26 power supply line (high-potential-side power supply line), 29 and 30 the third, fourth current mirror circuit, 44 amplifier circuit, 45 is a voltage - a current conversion circuit.

Claims (5)

A protected transistor, a temperature detection circuit that is arranged in the vicinity of the protected transistor and outputs a temperature detection signal having a level corresponding to the temperature of the arrangement position, and a threshold having a level corresponding to the start temperature of protection control A threshold generation circuit that outputs a signal, a comparison circuit that outputs an overheat detection signal when the temperature detection signal exceeds the threshold signal, and an output of the protected transistor when the overheat detection signal is output In a semiconductor device including a protection control circuit that executes protection control,
A second threshold value correction circuit for correcting the level of the threshold signal to the low temperature side to higher the threshold generator circuit voltage increases the power supply for supplying current to the output for the previous SL protected transistors, ambient comprises at least one one threshold correcting circuit of the third threshold value correction circuit for correcting the level of the threshold signal output by about the threshold value generating circuit environment temperature becomes higher temperature side A semiconductor device. The temperature detection circuit is configured to output a forward voltage of a diode;
The threshold generation circuit includes a voltage dividing resistor connected between a pair of voltage lines for supplying a constant voltage, and is configured to output a threshold voltage from the voltage dividing point.
The second and third threshold correction circuits correct the threshold voltage level by flowing a current through the voltage dividing resistor through a voltage dividing point of the threshold generating circuit. The semiconductor device according to claim 1. A first threshold value correction circuit for correcting the level of the threshold signal output from the threshold value generation circuit to a low temperature side as the current flowing through the protected transistor increases;
3. The semiconductor device according to claim 2, wherein the current detection circuit of the first threshold value correction circuit includes a sense transistor in which the protected transistor and a control terminal are connected to each other. The second threshold value correction circuit includes:
A first current mirror circuit connected to a low-potential-side power supply line of a pair of power supply lines for supplying current to the protected transistor;
A resistor connected between the input-side transistor and the high-potential-side power line of the first current mirror circuit;
An input-side transistor is connected between the high-potential-side power supply line and the output-side transistor of the first current mirror circuit, and outputs a current to the voltage dividing point of the threshold value generation circuit through the output-side transistor. the semiconductor device according to claim 2 or 3 further characterized in that is composed of a current mirror circuit. The third threshold value correction circuit includes:
A third current mirror circuit connected to the low potential side voltage line of the pair of voltage lines;
A resistor connected between the input-side transistor of the third current mirror circuit and the high-potential-side voltage line;
An input-side transistor is connected between the high-potential-side voltage line and the output-side transistor of the third current mirror circuit, and outputs a current to the voltage dividing point of the threshold value generation circuit through the output-side transistor. 5. The semiconductor device according to claim 2, comprising: a current mirror circuit .

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