JP2002016219A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a semiconductor device by limiting a momentary overcurrent or cutting off a continuous overcurrent, when an instantaneous overcurrent flows. SOLUTION: This semiconductor device is equipped with an MOSFET-type output element 1, an MOSFET-detecting element 2 which is connected to the output element 1 in parallel, a current limitating control circuit 3 which operates to limit the conduction of the output element 1 to protect the output element 1, a current cutoff control circuit 10 which operates to shield the output element 1 to protect the output element 1, and a control switching circuit 20 which is connected to the detecting element 2 in series and switches the control circuit 10 operating, to protect the output element 1 to the current limitating control circuit 3 or the current cutoff control circuit 10, according to temperature nearby the output element 1, when a current larger than a specific current flows.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an MO with a protection function.
The present invention relates to an S-type semiconductor device.

[0002]

2. Description of the Related Art As a semiconductor device of this kind, the applicant of the present invention is studying a semiconductor device shown in FIGS.

A semiconductor device according to a first study example shown in FIG. 5 includes an output MOSFET 101, a detection MOSFET 102 connected in parallel to the output MOSFET 101, and a detection MO.
A detection resistor 103 connected in series to the SFET 102, a detection resistor 103 is connected between the gate and the source, and the drain is an output MOSFET 101 and a detection MOS.
A current limiting MOSFET 104 connected to the gate of the FET 102 is provided.

A drain terminal D as this semiconductor device
Is an output MOSFET 101 and a detection MOSFET
102 is connected to the drain. The source terminal S of the semiconductor device is an output MOSFET.
It is connected to the source of the MOSFET 101 for detection and via the resistor 103 for detection while being connected to the source of the MOSFET 101 and the current limiting MOSFET 104. Further, the gate terminal G as the semiconductor device is connected to an output M
It is connected to the gates of the OSFET 101 and the detection MOSFET 102 and to the drain of the current limiting resistor.

The operation of the above will be described. This one is
Since a current flows through the detection MOSFET 102 in proportion to a current flowing through the output MOSFET 101 from the drain terminal D to the source terminal S of the semiconductor device, if an overcurrent flows through the output MOSFET 101, A large amount of current also flows through the detection resistor 103.

Then, the voltage between both ends of the detection resistor 103 increases, and the current limiting MOSFET 104 connected between the gate and the source across both ends of the detection resistor 103 conducts, so that the output from the source terminal S as a semiconductor device is output. MOS for
A current to flow to the gates of the FET 101 and the detection MOSFET 102 flows through the current limiting MOSFET 104 to the source terminal S as a semiconductor device as it is.

As a result, the current limited from the drain terminal D toward the source terminal S is applied to the output MOSFET 101 and the detection M so that the voltage between both ends of the detection resistor 103 and the threshold of the current limiting MOSFET 104 are balanced.
It flows to the OSFET 102.

On the other hand, the semiconductor device shown in FIG.
OSFET 101, detection MOSFET 102 connected in parallel to output MOSFET 101, detection MOSFET
A detecting resistor 103 connected in series to T102, a detecting resistor 103 connected between the gate and the source, a drain directly connected to the output MOSFET 101, and a detecting resistor M
The drain terminal D as the semiconductor device having the current cutoff MOSFET 106 connected to the gate of the OSFET 102 via the bias resistor 105 has the output MOSFET 101 and the detection M
It is connected to the drain of OSFET 102. Further, the source terminal S as the semiconductor device is connected to a detection M
The output MOSFET 101 is connected to the source of the OSFET 102 and via the bias resistor 105.
And the drain of the current interrupting MOSFET 106.

The operation of this will be described. This one is
Similarly to the first study example, the output MOSFET 1 is connected from the drain terminal D as the semiconductor device to the source terminal S.
01 in proportion to the current flowing through
When an overcurrent flows through the output MOSFET 101, the detection resistor 103
A lot of current will flow.

Then, the voltage between both ends of the detection resistor 103 increases, and the current interruption MOSFET 106 connected between the gate and the source across both ends of the detection resistor 103 conducts, and the output from the source terminal S as a semiconductor device is output. MOS for
The current to flow to the gate of the FET 101 flows through the bias resistor 105 and the current limiting MOSFET 104 to the source terminal S as a semiconductor device as it is.

As a result, the detection MOSFET 1 having a higher gate potential corresponding to the voltage between both ends of the bias resistor 105.
02 is slightly conductive, the output MOSFET 101 is cut off, and the voltage across the detecting resistor 103 and the current limiting MO are passed through the slightly conductive detecting MOSFET 102.
A limited current flows from the drain terminal D to the source terminal S so that the threshold value of the SFET 104 is balanced.

[0012]

In the above-described semiconductor device of the first study example, when an overcurrent flows through the output MOSFET 101, the output MOSFET 101 and the output MOSFET 101 are moved from the drain terminal D toward the source terminal S. M for detection
Since a limited current flows through the OSFET 102, the output MOSFET 101 can be protected from overcurrent.

However, this is an output MOS.
Since the current still flows through the FET 101, when the load voltage between the drain terminal D and the source terminal S increases, the output MOS
There is a possibility that the temperature of the FET 101 itself rises and is thermally destroyed.

In the above-described semiconductor device of the second study example, when an overcurrent flows through the output MOSFET 101, the output MOSFET 101 is cut off and the drain MOSFET passes through the slightly conducting detection MOSFET 102. Since a limited current flows from the terminal D to the source terminal S, the output MOSFET 101 can be protected from overcurrent.

[0015] However, when an instantaneous overcurrent such as a sudden current flows, the output MO
Even when it is not necessary to shut off the SFET 101, there is a problem that it is shut off.

The present invention has been made in view of the above points. The purpose of the present invention is to limit the current when an instantaneous overcurrent flows, and to reduce the current when a continuous overcurrent flows. An object of the present invention is to provide a semiconductor device which is protected by interruption.

[0017]

According to a first aspect of the present invention, there is provided a semiconductor device comprising: a MOSFET-type output element; and a MOSF connected in parallel to the output element.
An ET-type detection element, a current limit control circuit that operates to limit conduction of the output element to protect the output element, and operates to shut off the output element to protect the output element A current cutoff control circuit, and a control circuit that is connected in series to the detection element and operates to protect the output element when a current equal to or more than a predetermined current flows, according to a temperature near the output element, And a control switching circuit for switching to a current cutoff control circuit.

According to a second aspect of the present invention, there is provided the semiconductor device according to the first aspect, wherein the current limiting control circuit conducts so as to limit both gate signals to the output element and the detection element. MOSFET for
The current cutoff control circuit includes a cutoff MOSFET that is turned on to cut off a gate signal to the output element, and a bias voltage that generates a bias voltage that maintains conduction of the detection element by a current that is turned on in the cutoff MOSFET. A resistor, and the control switching circuit includes a limiting MOSFET.
Limiting MOSFET connected to the gate of the MOSFET and the blocking MOSFET connected to the gate of the blocking MOSFET
An impedance variable element whose impedance decreases with an increase in environmental temperature is arranged so as to be in thermal contact with the output element so as to reverse the level of the potential with the T connection point.

According to a third aspect of the present invention, in the semiconductor device according to the second aspect, the control switching circuit is configured such that the variable impedance element and the variable impedance element are connected alternately to form an impedance forming a bridge circuit. Element, and a connection resistor for connecting between the one opposing connection points of the bridge circuit, and the one opposing connection point connecting the impedance element on the upstream side of the current becomes the limiting MOSFET connection point, and One of the opposite connection points to which the variable impedance element is connected on the side is the limiting MOSFET connection point, and the other pair of opposite connection points of the bridge circuit is connected in series to the detecting element.

According to a fourth aspect of the present invention, in the semiconductor device according to the third aspect, the variable impedance element is a thermistor whose impedance is lower than that of the impedance element when an environmental temperature is equal to or higher than a predetermined temperature. ing.

According to a fifth aspect of the present invention, in the semiconductor device according to the third aspect, the impedance element includes:
It is a diode, and the impedance variable element is configured to be a series circuit in which more diodes than the impedance element are connected in series.

According to a sixth aspect of the present invention, in the semiconductor device according to the third aspect, the impedance element includes:
The variable impedance element is a series circuit in which a diode and a resistor are connected in series.

According to a seventh aspect of the present invention, in the semiconductor device according to the fifth or sixth aspect, the impedance variable element, the impedance element, and the connection resistor are made of polysilicon. I have to.

According to an eighth aspect of the present invention, in the semiconductor device according to the fifth or sixth aspect, the diode of the impedance variable element and the diode of the impedance element are provided with the output element. The diode of the variable impedance element is provided on an insulating film of the chip, and is provided on a thinner insulating film than the diode of the impedance element, so that the diode is in thermal contact with the output element.

According to a ninth aspect of the present invention, in the semiconductor device according to the fifth or sixth aspect, the output element, the detection element, and the limiting MOSFET are provided.
T, the blocking MOSFET, the variable impedance element, the impedance element, and the connection resistor,
Both are configured on the same chip

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device according to a first embodiment of the present invention will be described below with reference to FIGS.

Reference numeral 1 denotes an output MOSFET (MOSFET type output element) having a drain connected to a drain terminal D as the present semiconductor device, a source connected to a source terminal S as the present semiconductor device, and a gate. Is connected to a gate terminal G as the present semiconductor device via a bias resistor 4 described later. This output MOSFET
1 conducts between the drain and source so as to supply power to a load (not shown) connected between the drain terminal D and the source terminal S.

Reference numeral 2 denotes a detection MOSFET (MOSFET-type detection element) which is connected in parallel to the output MOSFET 1 and whose drain is connected to a drain terminal D as the semiconductor device, and whose source is a control switching circuit to be described later. Is connected to a source terminal S as the semiconductor device through
The gate is connected to a gate terminal G as the semiconductor device.

Reference numeral 3 denotes a limiting MOSFET (current limiting control circuit) whose drain is connected via a biasing resistor 4 to
Connected to the gate of output MOSFET 1
It is connected to the gate of the detection MOSFET 2 and the gate terminal G as the present semiconductor device. In addition, this restriction M
The source of the OSFET 3 is connected to a source terminal S as the present semiconductor device, and the gate is connected to a control switching circuit described later.

Reference numeral 5 denotes a blocking MOSFET, which together with the biasing resistor 4 connected to its drain constitutes a current blocking control circuit 10. The cut-off MOSFET 5 has a drain directly connected to the gate of the output MOSFET 1 and a detection resistor M via the bias resistor 4.
It is connected to the gate of the OSFET 2 and the gate terminal G as the present semiconductor device. In addition, the MOSFET
T5 has a source connected to a source terminal S as the semiconductor device and a gate connected to a control switching circuit described later.

Reference numerals 6a and 6b denote thermistors constituting the impedance element 6. Reference numerals 7a and 7b denote thermistors 7a and 7b constituting the variable impedance element 7,
A bridge circuit is formed by being alternately connected to a and 6b. The thermistors 7a and 7b are different from the thermistors 6a and 6b, as shown in FIG.
The output MO is arranged so as to be located near the FET1.
Thermal contact is made with SFET1. These thermistors 7a and 7b are provided at normal temperature.
Although the impedance is larger than that of the thermistors 6a and 6b, when the temperature rises to a predetermined temperature or more,
The impedance is smaller than that of 6b.

These thermistors 6a, 6b, 7a, 7
In the bridge circuit composed of b, the one opposing connection point of the pair of one opposing connection points to which the thermistor 6a is connected on the upstream side of the current is the limiting MOSFET connection point P1 connected to the gate of the limiting MOSFET 3, The opposite connection point where the thermistor 7a is connected on the upstream side of the current is the interruption MOSFET connection point P2 connected to the interruption MOSFET 5. This bridge circuit is a MOSFE for detection.
It is connected in series between T2 and the source terminal S as the semiconductor element.

Reference numeral 8 denotes a connection resistor which connects between one pair of connection points of the bridge circuit composed of the thermistors 6a and 6b and the thermistors 7a and 7b, that is, between the connection point P1 for the limiting MOSFET and the connection point P2 for the cutoff MOSFET. Are connected to form a control switching circuit 20 together with the thermistors 6a and 6b and the thermistors 7a and 7b.

Next, the operation of this embodiment will be described. From the gate terminal G as this semiconductor device, an output MOSFET
In each gate of T1 and the detection MOSFET2,
When a gate signal is input, conduction is established between the drain and source of each of the output MOSFET 1 and the detection MOSFET 2.

At this time, when the current flowing between the drain and the source of the detection MOSFET 2 flows through the control switching circuit 20 to the source terminal S as a semiconductor device, at normal temperature, the impedance of the thermistor 6a changes to the impedance of the thermistor 7a. Since it is smaller than the impedance, the thermistor 6a-the limiting MOSFET connection point P1-the connection resistance 8-the blocking MOSFET connection point P2-thermistor 6b
Will flow in that order.

Therefore, the limiting MOSFET connection point P1
Has a higher potential than the blocking MOSFET connection point P2, and the limiting MOSFET 3 whose gate is connected to the limiting MOSFET connection point P1 is
MOSF for cut-off whose gate is connected to T connection point P2
Prior to ET5, conduction between the drain and source is enabled.

Here, the output MOS
When an excessive current flows between the drain and the source of the FET1 and the detecting MOSFET2, the limiting MOSFET connection point P
1 rises, the conduction between the drain and the source of the limiting MOSFET 3 whose gate is connected to the limiting MOSFET connection point P1 is conducted, and the gate signal from the gate terminal G is applied to the drain and the source of the conducted limiting MOSFET 3 The current flows to the source terminal S through the gap.

Then, gate signals input to the gates of the output MOSFET 1 and the detection MOSFET 2 are limited, and the output MOSFET 1 and the detection MOSFET 2
The current flowing between the drain and the source is limited. When the current flowing between the drain and source of the detection MOSFET 2 is limited, the potential of the connection point of the restriction MOSFET 3 decreases, and the drain and source of the restriction MOSFET 3 whose gate is connected to the connection point of the restriction MOSFET 3 conduct. Become like

As a result, when the threshold value of the limiting MOSFET 3 and the potential of the limiting MOSFET connection point P1 are balanced, the output MOSFET 1 and the detecting MOSFET 2
The current flowing between the drain and the source of the transistor is limited.

As described above, when the state in which the current flowing between the drain and source of the output MOSFET 1 and the detection MOSFET 2 is limited continues, the output MOSFET
When the ET1 generates heat, the environmental temperature of the thermistors 7a and 7b arranged so as to be in thermal contact with the output MOSFET 1 rises above a predetermined temperature. Then, thermistor 7
a, 7b becomes smaller than the impedance of the thermistors 6a, 6b.
The current flowing between the drain and the source of the ET2 flows through the control switching circuit 20 to the source terminal S as a semiconductor device.
Connection point P2-Connection resistance 8-Limiting MOSFET connection point P
It flows in the order of 1-thermistor 7b.

Accordingly, the cutoff MOSFET connection point P2
Is higher in potential than the limiting MOSFET connection point P1, and the blocking MOSFET 5 whose gate is connected to the blocking MOSFET connection point P2 is
Limiting MOSF whose gate is connected to T connection point P1
Prior to ET3, conduction between the drain and source is enabled.

In this state, if the potential of the cutoff MOSFET connection point P2 rises due to the current flowing between the drain and source of the output MOSFET 1 and the detection MOSFET 2, the cutoff with the gate connected to the cutoff MOSFET connection point P2 The connection between the drain and the source of the MOSFET 5 is conducted, and the gate signal from the gate terminal G flows to the source terminal S through the drain and the source of the MOSFET 3 and the bias resistor 4.

Then, the gate signals input to the gates of the output MOSFET 1 and the detection MOSFET 2 are cut off, and the output MOSFET 1 and the detection MOSFET 2
The current flowing between the drain and the source is cut off.

On the other hand, the detection MOSFET 2 has a higher gate potential than the output MOSFET 1 by an amount corresponding to the voltage between both ends of the bias resistor 4 due to the current flowing through the bias resistor 4, so that the drain-source slightly conducts. to continue.

As a result, the cutoff MOSFET connection point P2
Does not decrease and the state in which the blocking MOSFET 5 remains conductive continues, so that the output MOSFET
The cutoff state between the drain and the source of T1 will continue.

In such a semiconductor device, when an instantaneous overcurrent flows, the potential of the limiting MOSFET connection point P1 increases, so that the gate potential of the limiting MOSFET 3 increases, and the limiting MOSFET 3 Since the continuity is established, the gate signal of the output MOSFET 1 is limited, the current flowing through the output MOSFET 1 is limited, and the output MOSFET 1 can be protected. When a continuous overcurrent flows, the impedance variable element 7 arranged so as to be in thermal contact with the output MOSFET 1 in response to an increase in the environmental temperature caused by heat generation based on the continuous overcurrent. The impedance is reduced, and the MOS for blocking is more than the connecting point P1 for the limiting MOSFET.
As the potential of the FET connection point P2 increases, the gate potential of the blocking MOSFET 5 increases, and the blocking MOS
Since the FET 5 conducts, the gate current to the output MOSFET 1 is cut off, and the output MOSFET 1 is cut off.
1 can be cut off, and the output MOSFET 1 can be protected.

The impedance variable element 7 is a thermistor whose impedance becomes smaller than that of the impedance element 6 when the environmental temperature is equal to or higher than a predetermined temperature.
The configuration of the bridge can be simplified.

In this embodiment, the impedance element 6 is composed of the thermistors 6a and 6b. The impedance element 6 has a lower impedance value than the thermistors 7a and 7b at a normal temperature, and the thermistor 7a when the environmental temperature rises to a predetermined temperature or higher. , 7b can provide the same effect with a normal resistor having a larger impedance value.

Next, a semiconductor device according to a second embodiment of the present invention will be described below with reference to FIG. Elements that are substantially the same as those of the semiconductor device of the first embodiment are denoted by the same reference numerals, and only those parts that differ from the semiconductor device of the first embodiment are described. In the semiconductor device of the first embodiment, the variable impedance element 7 is thermistors 7a and 7b, and the impedance element 6 is thermistors 6a and 6b. In the semiconductor device of the present embodiment, the variable impedance element 7 includes two diodes. Serial circuits 7c and 7d connected in series,
The impedance element 6 has a configuration including diodes 6c and 6d.

The impedance variable element 7 of this
Since the number of diodes is larger than that of the impedance element 6, the impedance is larger than that of the impedance element 6 at normal temperature. However, because of the thermal contact with the output MOSFET 1, the environmental temperature rises with the heat generation of the output MOSFET 1. When the temperature exceeds a predetermined temperature, the impedance of the diode decreases.
The impedance is smaller than that of the impedance variable element 7 that is not in thermal contact with the ET1.

The impedance element 6, the variable impedance element 7, and the connection resistor 8 are made of polysilicon.

The diode of the variable impedance element 7 and the diode of the variable impedance element 6 are provided on an insulating film of the chip provided with the output MOSFET 1, and the diode of the variable impedance element 7 is larger than the diode of the variable impedance element 6. Even when provided on a thin insulating film, it is in thermal contact with the output MOSFET 1.

The output MOSFET 1 and the detection MO
SFET2, limiting MOSFET3, blocking MOSFET
T5, the impedance element 6, the impedance variable element 7, and the connection resistor 8 are all provided on the same chip.

Next, the operation of the semiconductor device different from the semiconductor device of the first embodiment will be described. MO for output
When the conduction between the respective drains of the SFET 1 and the detection MOSFET 2 is conducted, the detection MOSFET 2
The current flowing between the drain and source of the
At the normal temperature, the impedance of the impedance element 6 having a smaller number of diodes than the variable impedance element 7 is smaller than that of the impedance element 6 at normal temperature. -Connection resistance 8-Interruption MOS
The current flows in the order of the FET connection point P2 and the diode 6d. Therefore, the potential of the limiting MOSFET connection point P1 is higher than that of the blocking MOSFET connection point P2.

The output MOSFET 1 and the detection M
If the output MOSFET 1 generates heat while the current flowing between the drain and source of the OSFET 2 continues to be limited, the environmental temperature of the series circuits 7c and 7d arranged so as to make thermal contact with the output MOSFET 1 becomes a predetermined temperature. Rise above.

Then, since the impedance of the series circuits 7c and 7d becomes smaller than the impedance of the diodes 6c and 6d which are not in thermal contact with the output MOSFET 1, the current flowing between the drain and the source of the detection MOSFET 2 becomes When flowing through the control switching circuit 20 to the source terminal S as a semiconductor device, the series circuit 7c
The current flows in the order of: the cut-off MOSFET connection point P2-the connection resistance 8; the limiting MOSFET connection point P1-the series circuit 7d. Therefore, the shutoff MOSFET connection point P2 is
The potential is higher than the limit MOSFET connection point P1.

In this semiconductor device, similarly to the semiconductor device of the first embodiment, when an instantaneous overcurrent flows, the potential of the limiting MOSFET connection point P1 rises, so that the limiting MOSFET 3 Since the gate potential rises and the limiting MOSFET 3 conducts, the output MO
The gate signal of the SFET 1 is limited, and the current flowing through the output MOSFET 1 is limited.
FET1 can be protected. Further, when a continuous overcurrent flows, the output MOSFET is increased in accordance with an increase in the environmental temperature caused by heat generation based on the continuous overcurrent.
The impedance of the variable impedance element 7 arranged to be in thermal contact with the first
Since the potential of the shutoff MOSFET connection point P2 becomes higher than the ET connection point P1, the gate potential of the shutoff MOSFET 5 rises and the shutoff MOSFET 5 becomes conductive, so that the gate current to the output MOSFET 1 is cut off. As a result, the current flowing through the output MOSFET 1 is cut off, and the output MOSFET 1 can be protected.

Further, since the impedance element 6 is a diode whose impedance becomes smaller as the temperature rises, and the impedance variable element 7 is a series circuit in which more diodes than the impedance element 6 are connected in series, the impedance of the bridge is reduced. The configuration can be simplified.

The impedance element 6, the variable impedance element 7, and the connection resistor 8 are all M
Since polysilicon is used as the gate material of the OSFET, it is formed together with the MOSFET when it is formed, and the manufacturing process can be simplified.

Further, since the diode of the impedance variable element 7 is provided on an insulating film thinner than the diode of the impedance element 6, thermal contact with the output element can be easily obtained. Switching by the control switching circuit 20 can be performed quickly.

Further, an output element, a detection element, and a limiting element M
OSFET 3, blocking MOSFET 5, impedance element 6, impedance variable element 7, and connection resistor 8
Since both are provided on the same chip, downsizing can be achieved and the operating characteristics of each element can be made uniform.

Next, a semiconductor device according to a third embodiment of the present invention will be described below with reference to FIG. Elements that are substantially the same as those of the semiconductor device of the second embodiment are given the same reference numerals, and only those parts that are different from the semiconductor device of the second embodiment will be described. In the semiconductor device of the second embodiment, the variable impedance element 7 is a series circuit 7 in which two diodes are connected in series.
c and 7d, the semiconductor device of the present embodiment has a configuration including series circuits 7e and 7f in which diodes and resistors are connected.

The variable impedance element 7 is
At normal temperature, the impedance of the output element 1 is larger than that of the impedance element 6 due to the inclusion of the resistance.
When the ambient temperature rises with the heat generated by the OSFET 1, the impedance of the diode decreases.
The impedance is smaller than that of the variable impedance element 7 that is not in thermal contact with the FET 1.

Next, the operation of the semiconductor device different from that of the semiconductor device of the second embodiment will be described. MO for output
When the conduction between the respective drains of the SFET 1 and the detection MOSFET 2 is conducted, the detection MOSFET 2
The current flowing between the drain and source of the
Through the source terminal S as a semiconductor device, at normal temperature, the impedance element 6 that does not include the resistance is replaced by the impedance variable element 7 that includes the resistance.
The impedance of the diode 6
The current flows in the order of c-limit MOSFET connection point P1-connection resistance 8-blocking MOSFET connection point P2-diode 6d. Therefore, the limiting MOSFET connection point P1
Has a higher potential than the blocking MOSFET connection point P2.

The output MOSFET 1 and the detection M
If the output MOSFET 1 generates heat when the current flowing between the drain and source of the OSFET 2 continues to be limited, the environmental temperature of the series circuits 7 e and 7 f arranged to be in thermal contact with the output MOSFET 1 increases. .

Then, since the impedance of the series circuits 7c and 7d becomes smaller than the impedance of the diodes 6c and 6d which are not in thermal contact with the output MOSFET 1, the current flowing between the drain and the source of the detection MOSFET 2 becomes When the current flows to the source terminal S as a semiconductor device through the control switching circuit 20, the series circuit 7e
The current flows in the order of: the cut-off MOSFET connection point P2-the connection resistance 8; the limiting MOSFET connection point P1-the series circuit 7f. Therefore, the shutoff MOSFET connection point P2 is
The potential is higher than the limit MOSFET connection point P1.

In this semiconductor device, similarly to the semiconductor device of the second embodiment, when an instantaneous overcurrent flows, the potential of the limiting MOSFET connection point P1 rises, and the limiting MOSFET 3 Since the gate potential rises and the limiting MOSFET 3 conducts, the output MO
The gate signal of the SFET 1 is limited, and the current flowing through the output MOSFET 1 is limited.
FET1 can be protected. Further, when a continuous overcurrent flows, the output MOSFET is increased in accordance with an increase in the environmental temperature caused by heat generation based on the continuous overcurrent.
The impedance of the variable impedance element 7 arranged to be in thermal contact with the first
Since the potential of the shutoff MOSFET connection point P2 becomes higher than the ET connection point P1, the gate potential of the shutoff MOSFET 5 rises and the shutoff MOSFET 5 becomes conductive, so that the gate current to the output MOSFET 1 is cut off. As a result, the current flowing through the output MOSFET 1 is cut off, and the output MOSFET 1 can be protected.

The impedance element 6, the variable impedance element 7, and the connection resistor 8 are all M
Since the gate material of the OSFET is polysilicon, the manufacturing process can be simplified, and the diode of the impedance variable element 7 is replaced with the impedance element 6
Because it is provided on an insulating film thinner than the diode, thermal contact with the output element can be easily obtained,
As a result, switching by the control switching circuit 20 can be performed faster, and the output MOSFET 1 and the detection MOSFET
ET2, limiting MOSFET3, blocking MOSFET
5, impedance element 6, impedance variable element 7
Since the connection resistor 8 and the connection resistor 8 are both provided on the same chip, the size can be reduced and the operating characteristics of each element can be made uniform.

The impedance element 6 includes a diode 6c whose impedance decreases as the temperature rises.
6d, and the variable impedance element 7 is a series circuit 7e, 7f in which a diode and a resistor are connected in series, so that the configuration of the bridge can be simplified.

In the semiconductor devices of the first to third embodiments, the MOSFET-type output element and the MOSFET-type detection element are both MOSFETs.
Other MOSFET type devices such as GBT may be used.

In the semiconductor devices of the first and second embodiments, the output MOSFET 1, the detection MOSFET 2,
The limiting MOSFET 3, the blocking MOSFET 5, the impedance element 6, the impedance variable element 7, and the connection resistor 8 are all provided on the same chip.
However, the present invention is not limited to this, and may be configured by combining discrete components.

In the semiconductor devices of the first and second embodiments, the impedance variable element 7 is
1 and a configuration provided on an insulating film thinner than the impedance element 6 so as to make thermal contact with the output MOSFET 1. If contact is possible, only one of the configurations may be used.

[0073]

According to the first aspect of the present invention, when an instantaneous overcurrent flows, the current limiting control circuit is operated to limit the current flowing to the output element, thereby protecting the output element. can do. Further, when a continuous overcurrent flows, the control switching circuit operates to protect the output element in response to a rise in the nearby temperature accompanying heat generation based on the continuous overcurrent. Is switched from the current limit control circuit to the current cutoff control circuit 10, and the current cutoff control circuit is operated, whereby the output element can be cut off and the output element can be protected.

In the semiconductor device according to the second aspect, when an instantaneous overcurrent flows, the potential of the limiting MOSFET connection point rises, so that the gate potential of the limiting MOSFET rises, and the limiting MOSFET becomes Since the continuity is established, the gate signal of the output element is limited, the current flowing through the output element is limited, and the output element can be protected. Further, when a continuous overcurrent flows, the impedance of the variable impedance element arranged so as to be in thermal contact with the output element in accordance with an increase in the environmental temperature due to heat generation based on the continuous overcurrent. Is smaller than the limit MOSFET connection point.
As the potential at the T connection point increases, the MOSF
Since the gate potential of the ET rises and the blocking MOSFET conducts, the gate current to the output element is cut off, and the current flowing to the output element is cut off to protect the output element. it can.

According to a third aspect of the present invention, when the ambient temperature is a normal temperature, the impedance variable element having a smaller impedance than the impedance variable element is connected to the current upstream side while the variable impedance element is connected to the opposite connection point. Since the current flows through the opposing connection point connected to the upstream side of the current, the potential of the limiting MOSFET connection point becomes higher than that of the blocking MOSFET connection point, and when the environmental temperature rises above the normal temperature, Since the current flows from the opposed connection point where the impedance variable element having an impedance smaller than the impedance element is connected to the upstream side of the current through the opposed connection point where the impedance element is connected to the upstream side of the current, the MOSFET connection for interruption is used. The potential of the point becomes higher than the connection point of the MOSFET for restriction,
The effect of the semiconductor device according to claim 2 can be reliably achieved.

According to a fourth aspect of the present invention, in addition to the effect of the third aspect of the present invention, the impedance variable element is a thermistor whose impedance becomes smaller than the impedance element when the environmental temperature is equal to or higher than a predetermined temperature. Therefore, the configuration of the bridge can be simplified.

In the semiconductor device according to the fifth aspect, in addition to the effect of the semiconductor device according to the third aspect, the impedance element is a diode whose impedance decreases as the temperature rises, and the variable impedance element is smaller than the impedance element. Is a series circuit in which many diodes are connected in series, so that the configuration of the bridge can be simplified.

According to the semiconductor device of the sixth aspect, in addition to the effect of the semiconductor device of the third aspect, the impedance element is a diode whose impedance decreases as the temperature rises, and the impedance variable element is a diode and a resistor. Is a series circuit connected in series, so that the configuration of the bridge can be simplified.

According to a seventh aspect of the present invention, in addition to the effect of the semiconductor device according to the fifth or sixth aspect, all of the variable impedance element, the impedance element, and the connection resistance are the same as those of the MOSFET. Since polysilicon is used as the gate material, it is formed together with the MOSFET when it is formed, and the manufacturing process can be simplified.

In the semiconductor device according to the eighth aspect, in addition to the effects of the semiconductor device according to the fifth or sixth aspect, the diode of the variable impedance element is formed on an insulating film thinner than the diode of the impedance element. Therefore, thermal contact with the output element can be easily obtained, and switching by the control switching circuit can be performed more quickly.

According to a ninth aspect of the present invention, in addition to the effects of the semiconductor device according to the fifth or sixth aspect, an output element, a detection element, a limiting MOSFET, a blocking MOSFET, an impedance Since the variable element, the impedance element, and the connection resistor are all provided on the same chip, miniaturization can be achieved, and
The operating characteristics of each element can be made uniform.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a positional relationship between an impedance variable element of the control switching circuit and an output MOSFET.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a first study example.

FIG. 6 is a circuit diagram of a second study example.

[Explanation of symbols]

Reference Signs List 1 output MOSFET (MOSFET-type output element) 2 detection MOSFET (MOSFET-type detection element) 3 limiting MOSFET (current limit control circuit) 4 bias resistor 5 blocking MOSFET 6 impedance element 6c, 6d diode 7 Variable impedance element 7a, 7b Thermistor 7c, 7d Series circuit 7e, 7f Series circuit 8 Connection resistor 10 Current cutoff control circuit 20 Control switching circuit P1 Limiting MOSFET connection point P2 Blocking MOSFET connection point

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noriaki Furumoto 1048 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. Term (reference) 5F038 AV01 BH01 BH02 BH04 BH05 BH07 BH13 BH16 CA07 DF07 DF17 EZ04 EZ20

Claims (9)

[Claims] An output element of a MOSFET type; a detection element of a MOSFET type connected in parallel to the output element;
A current limit control circuit that operates to limit conduction of the output element to protect the output element, a current cutoff control circuit that operates to cut off the output element to protect the output element, and a detection circuit Control switching that switches the control circuit, which is connected in series with the element and operates to protect the output element when a current exceeding a predetermined current flows, to a current limit control circuit or a current cutoff control circuit according to the temperature near the output element A semiconductor device comprising: a circuit. 2. The current limiting control circuit includes a limiting MOSFET that conducts so as to limit both gate signals to the output element and the detecting element. MOSFET for interrupting to shut off gate signal to device and MO for interrupting the MOSFET
A bias resistor for generating a bias voltage for maintaining conduction of the detection element by a current conducted to the SFET, wherein the control switching circuit includes a limiting MOSFET connection point connected to the gate of the limiting MOSFET and MOS
An impedance variable element whose impedance is reduced in accordance with an increase in environmental temperature is arranged so as to be in thermal contact with the output element so as to reverse the level of the potential between the MOSFET and the shutoff MOSFET connected to the gate of the FET. The semiconductor device according to claim 1. 3. The control switching circuit for connection between the variable impedance element, an impedance element alternately connected to the variable impedance element to form a bridge circuit, and one connection point of the bridge circuit. And an opposite connection point where the impedance element is connected to the upstream side of the current and the limiting MOSF
ET connection point, and the opposite connection point connecting the variable impedance element upstream of the current is the limiting MOS
3. The semiconductor device according to claim 2, wherein the connection point is an FET connection point, and the pair of other connection points of the bridge circuit are connected in series to the detection element. 4. The semiconductor device according to claim 3, wherein said variable impedance element is a thermistor whose impedance becomes lower than that of said impedance element when an environmental temperature is equal to or higher than a predetermined temperature. 5. The semiconductor device according to claim 3, wherein said impedance element is a diode, and said impedance variable element is a series circuit in which more diodes than said impedance element are connected in series. 6. The semiconductor device according to claim 3, wherein said impedance element is a diode, and said impedance variable element is a series circuit in which a diode and a resistor are connected in series. 7. The semiconductor device according to claim 5, wherein the variable impedance element, the impedance element, and the connection resistor are made of polysilicon. 8. The diode of the impedance variable element and the diode of the impedance element are provided on an insulating film of a chip provided with the output element,
7. The semiconductor device according to claim 5, wherein the diode of the impedance variable element is provided on an insulating film thinner than the diode of the impedance element, and is in thermal contact with the output element. 8. 9. The output element, the detection element, the limiting MOSFET, the blocking MOSFET, the variable impedance element, the impedance element, and the connection resistor are all provided on the same chip. The semiconductor device according to claim 5.