JP2001235490A - Overcurrent detection circuit - Google Patents

Abstract

(57) [Problem] To provide an overcurrent detection circuit capable of accurately preventing an accelerated temperature rise in a protection target in an overcurrent state at a high temperature. SOLUTION: A comparator circuit 1 which compares a reference voltage V0 with a comparison voltage V0 'derived according to an output current, detects a current exceeding an overcurrent limit value, and makes an overcurrent determination,
An output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, and supplying a bias current to the comparator circuit to regulate fluctuations of the comparison voltage V0 'in the comparator circuit By
A constant current circuit 3 is provided for reducing the overcurrent limit value Ioc set by the reference voltage V0 and the comparison voltage V0 'as the temperature rises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent detection circuit for an object to be protected, such as a semiconductor integrated circuit, and more particularly to an overcurrent detection circuit for preventing an accelerated temperature rise in the object to be protected.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional overcurrent detection circuit. In the figure, 1 is a comparator circuit, 2 is an output stage circuit, VB is a power supply, Rext is a resistor, and Qext is an output transistor. Here, it is assumed that the power supply VB, the resistor Rext, and the output transistor Qext are externally mounted, and Rext uses a resistor having no temperature dependency. As the circuit configuration,
The circuit comprises a comparator circuit 1 for detecting an overcurrent, and an output stage circuit 2 for receiving / prohibiting a current from flowing to an output by receiving a signal from the comparator circuit 1 and turning on / off an output transistor Qext.

In a normal state (when no overcurrent flows in the output), the output current flowing through the resistor Rext is not so large, so that the voltage drop at the resistor Rext is small. Therefore, the reference voltage V0 and the comparison voltage V0 ', which are two input voltages in the comparator circuit 1, are higher in the comparison voltage V0', the transistor Q9 in the output stage is turned off, and the transistor Q11 is turned on. . As a result, the base of the external output transistor Qext is pulled by the transistor Q11 to be in the ON state, and the current continues to be supplied to the output.

However, as an output, a certain current limit value Ioc
When a current exceeding (oc = over current) flows, the voltage drop at the resistor Rext increases, and conversely, the potential of the comparison voltage V0 'becomes lower at the two input voltages in the comparator circuit 1. As a result, the transistor Q9 is turned on, the transistor Q11 is turned off, and the output transistor Qext is turned off, thereby preventing the output transistor Qext from flowing a current to the output.

As described above, the present circuit has a configuration in which the output transistor Qext is turned off at the moment when an overcurrent flows, thereby preventing the overcurrent from flowing to the output.
The overcurrent limit value Ioc is determined when the comparison voltage V0 'falls below the reference voltage V0 determined by the comparator circuit 1. Hereinafter, the overcurrent limit value Ioc is determined. V
BE1 to VBE4 are the base-emitter voltages of the transistors Q1 to Q4. In this circuit, VBE1 =... VBE4 =
It is assumed that VBE is set. Also, IBias1 and IBias1
Bias2 is a bias current supplied to the transistors Q4 and Q3, and these are also IBias1 = IBi
It is assumed that as2 = IBias is set.
At this time, if the base currents of the transistor Q5 and the transistor Q6 are neglected, the reference voltage V0 and the comparison voltage V0 'are V0 = VB-2VBE-R0 * IBias V0' = VB-Rext * Iext-2VBE (Iext: output Current). In a normal state, V0−V0 ′ = Iext × Rext−IBias × R0 <0. However, when the output current Iext exceeds the overcurrent limit value Ioc, V0−V0 ′> 0, and the output transistor is turned off. . The overcurrent limit value Ioc is obtained by setting V0 = V0 ', and is determined as follows: Ioc = IBias × R0 / Rext (1)

Consider the temperature dependence of the overcurrent limit value Ioc expressed by equation (1). As described above, the resistor Rext is external and has no temperature dependency. The resistance R0 has a positive temperature characteristic, and its resistance increases as the temperature rises. Here, if the temperature characteristic of IBias is not considered and a constant bias current is supplied with respect to a temperature change, when the temperature of the entire circuit rises, this overcurrent limit value I
oc will increase. As a result, the IC including this circuit
When the overcurrent flows in a state where the temperature is high, there arises a problem that the overcurrent is not restricted due to the increase of the limit value. Further, if the overcurrent continues to flow, the temperature rise due to the heat generation of the IC is promoted, so that the limit value further increases, and the temperature rise of the IC occurs at an accelerated rate.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to be used when an overcurrent flows through a protection target such as a semiconductor integrated circuit at a high temperature. An object of the present invention is to provide an overcurrent detection circuit that can prevent an overcurrent from continuing to flow to a protection target due to an increase in a current limit value, and can accurately prevent an accelerated temperature rise in the protection target.

[0008]

An overcurrent detection circuit according to a first aspect of the present invention compares a reference voltage with a comparison voltage derived according to an output current, and detects a current exceeding an overcurrent limit value. A comparator circuit for determining an overcurrent, and an output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, and regulating at least one of a reference voltage and a comparison voltage in the comparator circuit. This prevents an overcurrent limit value set by the reference voltage and the comparison voltage from increasing due to a rise in temperature.

In the overcurrent detection circuit according to the second invention, the reference voltage is compared with a comparison voltage derived in accordance with the output current, and a current exceeding the overcurrent limit value is detected to perform an overcurrent determination. A comparator circuit, comprising an output stage circuit for stopping the output current when an overcurrent is detected by the comparator circuit, and regulating at least one of the reference voltage and the comparison voltage in the comparator circuit to thereby control the reference voltage and The overcurrent limit value set by the comparison voltage is reduced as the temperature rises.

In the overcurrent detection circuit according to a third aspect of the present invention, the reference voltage is compared with a comparison voltage derived according to the output current, and a current exceeding an overcurrent limit value is detected to determine an overcurrent. A comparator circuit, an output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, and supplying a bias current to the comparator circuit; at least one of a reference voltage and a comparison voltage in the comparator circuit. And a constant current circuit for reducing the overcurrent limit value set by the reference voltage and the comparison voltage as the temperature rises.

An overcurrent detection circuit according to a fourth aspect of the present invention compares the reference voltage with a comparison voltage derived in accordance with the output current, detects a current exceeding an overcurrent limit value, and makes an overcurrent determination. A comparator circuit, comprising an output stage circuit for stopping the output current when an overcurrent is detected by the comparator circuit, and regulating at least one of the reference voltage and the comparison voltage in the comparator circuit to thereby control the reference voltage and The overcurrent limit value set by the comparison voltage is made constant regardless of the temperature rise.

In the overcurrent detection circuit according to a fifth aspect of the present invention, the reference voltage is compared with a comparison voltage derived according to the output current, and a current exceeding an overcurrent limit value is detected to perform an overcurrent determination. A comparator circuit, comprising an output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, wherein a reference voltage in the comparator circuit is set by a constant voltage source having no temperature dependency, and a variation thereof is set. By restricting, the overcurrent limit value set by the reference voltage and the comparison voltage is made constant regardless of the temperature rise.

In an overcurrent detection circuit according to a sixth aspect of the present invention, the reference voltage is compared with a comparison voltage derived in accordance with the output current, and a current exceeding an overcurrent limit value is detected to determine an overcurrent. A comparator circuit, an output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, wherein a reference voltage in the comparator circuit is set via an operational amplifier by a constant voltage source having no temperature dependency. By regulating the fluctuation, the overcurrent limit value set by the reference voltage and the comparison voltage is made constant regardless of the temperature rise.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an overcurrent detection circuit according to the present invention. In the figure, the same reference numerals as those in FIG. 4 showing the prior art indicate the same or corresponding parts. Hereinafter, the configuration of the circuit will be described with reference to FIG. In the figure, 1 is a comparator circuit, 2 is an output stage circuit, 3 is a constant current circuit, VB is a power supply, Rext is a resistor, Qext is an output transistor, Q1 to Q23 are transistors, and R0 and R1 to R10 are resistors.

This circuit is a circuit in which a constant current circuit 3 is newly added in order to generate a bias current of the conventional circuit shown in FIG. 4 (dotted line in FIG. 1). The current generated by the constant current circuit 3 is supplied to the current mirror by the current mirror.
A bias current consisting of Bias1 to IBias4 is supplied. Otherwise, the configuration is the same as that of the conventional circuit. Also in this circuit, the power supply VB, the resistor Rext, the output transistor Qext
Is external, and a resistor Rext having no temperature dependency is used.

First, when the power supply VB rises, a starting circuit composed of the transistor Q12 and the resistor R1 is switched to a constant current circuit 3
Start The activated constant current circuit 3 generates a current VBE13 / R2 determined by the base-emitter voltage VBE13 of the transistor Q13 and the resistor R2, and supplies each bias current composed of IBias1 to IBias4 by a current mirror. Here, for simplicity, R3 = R4
== …… = R9 At this time, IBias1 = IBias2 =... = IBias4 = VBE13 /
R2 and each bias current value are set.

Under the bias current determined as described above, the overcurrent detection circuit operates as in the conventional example. Also in this circuit, the current flowing through the resistor Rext has a certain limit value Ioc.
Is exceeded, that is, when the potential of V0 'is lower than the potential of V0 when the reference voltage V0 and the comparison voltage V0' are two input voltages of the comparator section 1, the output transistor Q11
Is turned off, the transistor Qext is turned off.
F to prevent current from flowing to the output.

The reference voltage V0 and the comparison voltage V0 'are the same as in the prior art, that is, the base-emitter voltages of the transistors Q1 to Q4 are equal to VBE, and the transistors Q5 and Q6
In addition to negligible base current, IBias1 = VBE
Considering that 13 / R2, V0 = VB-2VBE- (R0 / R2) .times.VBE13 V0 '= VB-Rext.times.Iext-2VBE (Iext: output current), and the output current when V0 = V0' Is Ioc, it is determined that Ioc = (1 / Rext) .times. (R0 / R2) .times.VBE13 (2).

Consider the temperature characteristic of the current limit value Ioc expressed by the equation (2). Rext is an external resistor and has no temperature dependency. The resistors R0 and R2 each have a positive temperature characteristic, but the temperature characteristics are offset by R0 / R2. As a result, the temperature characteristic of the current limit value Ioc depends on VBE13, and since the base-emitter voltage VBE has a negative temperature characteristic, the current limit value Ioc has a negative temperature characteristic. For this reason, in this circuit, since the overcurrent limit value decreases as the temperature rises, it is possible to solve the conventional problem that the overcurrent limit is not applied when the temperature rises. As a result, it is possible to prevent an accelerated temperature rise of the IC, which is generated because the overcurrent continues to flow.

According to the first embodiment of the present invention, the reference voltage V0 and the comparison voltage V derived according to the output current
0 ′, a comparator circuit 1 for detecting a current exceeding the overcurrent limit value and performing an overcurrent determination, and an output stage circuit 2 for stopping the output current when the overcurrent is detected by the comparator circuit 1. A bias current is supplied to the comparator circuit 1 to regulate the fluctuation of the comparison voltage V0 'in the comparator circuit 1 so that the overcurrent limit value Ioc set by the reference voltage V0 and the comparison voltage V0' is increased. Therefore, since the constant current circuit 3 for decreasing the current is provided, the overcurrent limit value Ioc is reduced by the constant current circuit 3 according to the temperature rise, so that an overcurrent flows to a protection target such as a semiconductor integrated circuit at a high temperature. Occasionally, an overcurrent detection circuit that can accurately prevent an accelerated temperature rise in the protection target can be obtained.

Embodiment 2 FIG. Second Embodiment A second embodiment according to the present invention will be described with reference to FIG. FIG. 2 is an overall configuration diagram of the overcurrent detection circuit according to the present invention. In the figure, the same reference numerals as those in the first embodiment indicate the same or corresponding parts. Hereinafter, the configuration of the circuit will be described with reference to FIG. In the figure, 1 is a comparator circuit, 2 is an output stage circuit, 3 is a constant current circuit, VB is a power supply, Rext is a resistor, Qext is an output transistor, Q1 to Q26 are transistors, and R1 to R12.
Is a resistor, and VREF is a constant voltage source voltage.

This circuit uses the temperature-independent voltage VREF in order to eliminate the temperature dependency of the input threshold voltage V0 as the reference voltage in the comparator circuit 1 in the circuit of the first embodiment shown in FIG. It is newly reconfigured. Otherwise, the circuit configuration is the same as that of the first embodiment. Also in this circuit, the power supply VB and the resistor R
ext and the output transistor Qext are externally connected, and the resistance R
ext shall not have temperature dependency.

As in the first embodiment, the power supply VB starts up a starting circuit including the transistor Q12 and the resistor R1,
This starting circuit starts the constant current circuit 3. The activated constant current circuit 3 supplies bias currents IBias1 to IBias5 by a current mirror. Under these bias currents, the overcurrent detection circuit operates. That is, also in this circuit, when the current flowing through the resistor Rext exceeds a certain limit value Ioc, the potential of the reference voltage V0 'and the reference voltage V0' as the two input voltages of the comparator unit 1 become the reference voltage Becomes lower than the potential of V0, turning off the output transistor Q11 and turning off the output transistor Qext.
To prevent current from flowing to the output.

Now, the reference voltage V0 and the comparison voltage V0 'will be obtained below. Taking into account that the base-emitter voltages of the transistors Q1 to Q4 are equal to VBE and that the base current of each transistor can be neglected,
As in the first embodiment, the comparison voltage V0 'is determined as follows: V0' = VB-Rext * Iext-2VBE (Iext: output current). Next, as for the reference voltage V0, the emitter potential V1 of the transistor Q25 in the figure is offset by the rise of the base-emitter voltage VBE of the transistor Q26 and the fall of the VBE of the transistor Q25. , Approximately equal to the constant voltage source voltage VREF. For this reason,
The emitter current of transistor Q25 is determined as VREF / R12. Assuming that the base current of the transistor Q25 can be neglected, the base potential V2 of the transistor Q2 becomes V2 = VB- (R11 / R12) .times.VREF, and the reference voltage V0 is V0 = VB- (R11 / R12) .times.VREF-2VBE. Is determined. The output current Iext = Ioc when the reference voltage V0 becomes equal to the comparison voltage V0 'is determined as follows: Ioc = (1 / Rext) .times. (R11 / R12) .times.VREF (3)

Consider the temperature characteristic of the current limit value Ioc expressed by the equation (3). Since the resistor Rext is an external resistor and has no temperature dependency, and R11 and R12 cancel each other's positive temperature characteristics, R11 / R12 also has no temperature dependency. Further, as described above, since the voltage VREF maintains a constant voltage with respect to a temperature change, as a result, the equation (3) has no temperature dependency. For this reason, this circuit can solve the problem that the overcurrent is not limited by the temperature rise in the conventional example, and can prevent the IC from generating heat due to the overcurrent flowing continuously. Further, unlike Embodiment 1, it is possible to always limit the current with a constant current value even when the temperature increases.

According to the second embodiment of the present invention, the reference voltage V0 and the comparison voltage V derived according to the output current
0 ′, a comparator circuit 1 for detecting a current exceeding the overcurrent limit value Ioc and performing an overcurrent determination, and an output stage circuit 2 for stopping the output current when the overcurrent is detected by the comparator circuit 1 And a constant current circuit 3 for supplying a bias current to the comparator circuit 1 to regulate the fluctuation of the comparison voltage V0 'in the comparator circuit 1 and for setting the reference voltage V0 in the comparator circuit 1 to a constant value having no temperature dependency. Set by the voltage source voltage VREF,
By regulating the fluctuation, the overcurrent limit value Ioc set by the reference voltage V0 and the comparison voltage V0 'is made constant regardless of the temperature rise. Overcurrent detection circuit that can accurately prevent accelerated temperature rise in the protection target when an overcurrent flows through the protection target such as a semiconductor integrated circuit at a high temperature by setting the constant voltage source voltage VREF that does not have Can be obtained.

Embodiment 3 Third Embodiment A third embodiment according to the present invention will be described with reference to FIG. FIG. 3 is an overall configuration diagram of the overcurrent detection circuit according to the present invention. In the figure, the second embodiment
The same reference numerals indicate the same or corresponding parts. Hereinafter, the configuration of the circuit will be described with reference to FIG. In the figure, 1 is a comparator circuit, 2 is an output stage circuit, 3 is a constant current circuit, VB is a power supply, Rext is a resistor, Qext is an output transistor, Q1 to Q25 are transistors, and R1 to R12.
Is a resistor, VREF is a constant voltage source voltage, and 4 is an operational amplifier.

This circuit is configured to provide the emitter voltage V1 of the transistor Q25 with a value closer to the temperature-independent voltage VREF in the circuit of the second embodiment shown in FIG. Otherwise, the circuit configuration is the same as that of the second embodiment. Also in this circuit, the power supply VB and the resistor Rex
t, the transistor Qext is externally attached, and the resistor Rext is not temperature-dependent.

The basic operation is exactly the same as in the second embodiment. That is, the power supply VB starts up a starting circuit including the transistor Q12 and the resistor R1, and the starting circuit starts the constant current circuit 3. The activated constant current circuit 3 generates bias currents IBias1 to IBias4 by a current mirror.
Supply. Under these bias currents, the overcurrent detection circuit operates. That is, when the current flowing through the resistor Rext exceeds a certain limit value Ioc, the potential of the comparison voltage V0 'becomes lower than the potential of V0 between the reference voltage V0 as the two input voltages of the comparator unit 1 and the comparison voltage V0', The output transistor Q11 is turned off, and the output transistor Qext is turned off to prevent a current from flowing to the output.

Also, regarding the reference voltage V0 and the comparison voltage V0 ', considering that the base-emitter voltage of Q25 becomes equal to VREF, V0' = VB-Rext * Iext-2VBE (Iext: output current) It is determined that V0 = VB-R11 / R12 * VREF-2VBE.

Here, in the second embodiment, the description has been made on the assumption that the emitter potential V1 of the transistor Q25 is equal to VREF. However, actually, the base-emitter voltage VBE26 of the PNP transistor Q26 and the base potential of the NPN transistor Q25 are Since the emitter-to-emitter voltage VBE25 does not always match, the difference between the constant voltage source voltage VREF and the base-emitter voltage VBE is | VBE25-VBE26 |.

Therefore, the present circuit is configured to minimize the deviation between the emitter potential V1 of the transistor Q25 and the constant voltage source voltage VREF. In this circuit, the operational amplifier 4 is used to apply a constant voltage source voltage VREF to one of the two input terminals.
A value closer to the constant voltage source voltage VREF can be supplied as the emitter potential V1 of the transistor Q25. As in the second embodiment, the overcurrent limit value Ioc is obtained as follows: Ioc = (1 / Rext) × (R11 / R12) × VREF (3)

As described above, since the emitter potential V1 of the transistor Q25 takes a value closer to the constant voltage source voltage VREF, in the case of the present embodiment, the expression (3) takes a more accurate value. As a result, the temperature dependence of the equation (3) takes a temperature dependence closer to the constant voltage source voltage VREF, and the temperature characteristic of the current limit value Ioc can be reduced as compared with the second embodiment. Therefore, even if the temperature changes, it is possible to obtain an overcurrent limit value with less variation than in the second embodiment.

According to the third embodiment of the present invention, the reference voltage V0 and the comparison voltage V derived according to the output current
0 ′, a comparator circuit 1 for detecting a current exceeding the overcurrent limit value Ioc and performing an overcurrent determination, and an output stage circuit 2 for stopping the output current when the overcurrent is detected by the comparator circuit 1 And a constant current circuit 3 for supplying a bias current to the comparator circuit 1 to regulate the fluctuation of the comparison voltage V0 'in the comparator circuit 1 and for setting the reference voltage V0 in the comparator circuit 1 to a constant value having no temperature dependency. The overcurrent limit value Ioc set by the reference voltage V0 and the comparison voltage V0 'is set to be constant irrespective of the temperature rise by setting the voltage source voltage VREF via the operational amplifier 4 and regulating the fluctuation. Therefore, the reference voltage V0 in the comparator circuit 1 is set via the operational amplifier 4 by the constant voltage source voltage VREF having no temperature dependency. Accordingly, when an overcurrent flows through the protected, such as a semiconductor integrated circuit at a high temperature, it is possible to obtain an overcurrent detection circuit capable of more accurately prevent accelerated temperature rise in the protected.

[0035]

According to the first aspect, the comparator circuit compares the reference voltage with the comparison voltage derived in accordance with the output current, detects a current exceeding the overcurrent limit value, and makes an overcurrent determination. An output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit,
By regulating at least one of the reference voltage and the comparison voltage in the comparator circuit, it is possible to prevent an overcurrent limit value set by the reference voltage and the comparison voltage from increasing due to a temperature rise. When an overcurrent flows through a protection target such as an integrated circuit, it is possible to obtain an overcurrent detection circuit that can accurately prevent an accelerated temperature rise in the protection target.

According to the second aspect of the invention, the comparator circuit compares the reference voltage with a comparison voltage derived according to the output current, detects a current exceeding the overcurrent limit value, and makes an overcurrent determination. An output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, and regulating at least one of a reference voltage and a comparison voltage in the comparator circuit, thereby setting the reference voltage and the comparison voltage. Since the overcurrent limit value is reduced as the temperature rises, at least one of the reference voltage and the comparison voltage in the comparator circuit regulates the fluctuation, so that an overcurrent flows to a protection target such as a semiconductor integrated circuit at a high temperature. Sometimes, it is possible to obtain an overcurrent detection circuit that can accurately prevent an accelerated temperature rise in the protection target.

According to the third aspect of the invention, a comparator circuit that compares a reference voltage with a comparison voltage derived according to an output current, detects a current exceeding an overcurrent limit value, and determines an overcurrent, An output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, and supplying a bias current to the comparator circuit to regulate a fluctuation of at least one of a reference voltage and a comparison voltage in the comparator circuit By providing a constant current circuit for reducing the overcurrent limit value set by the reference voltage and the comparison voltage as the temperature rises,
By providing a bias current to the comparator circuit and providing a constant current circuit that regulates fluctuations of the reference voltage and the comparison voltage in the comparator circuit, when an overcurrent flows to a protection target such as a semiconductor integrated circuit at a high temperature, In addition, it is possible to obtain an overcurrent detection circuit that can accurately prevent an accelerated temperature rise in the protection target.

According to the fourth invention, a comparator circuit for comparing a reference voltage with a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value, and performing an overcurrent determination, An output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit, and regulating at least one of a reference voltage and a comparison voltage in the comparator circuit, thereby setting the reference voltage and the comparison voltage. Since the overcurrent limit value set by the reference voltage and the comparison voltage is fixed regardless of the temperature rise, the overcurrent limit value is kept constant regardless of the temperature rise. Overcurrent detection circuit that can accurately prevent accelerated temperature rise in the protection target when an overcurrent flows to the protection target such as a circuit It is possible to obtain.

According to the fifth aspect, a comparator circuit that compares a reference voltage with a comparison voltage derived in accordance with an output current, detects a current exceeding an overcurrent limit value, and determines overcurrent, An output stage circuit for stopping an output current when an overcurrent is detected by a comparator circuit, and a reference voltage in the comparator circuit is set by a constant voltage source having no temperature dependency, thereby regulating the fluctuation. Since the overcurrent limit value set by the reference voltage and the comparison voltage is made constant regardless of the temperature rise, by setting the reference voltage in the comparator circuit by a constant voltage source having no temperature dependency,
When an overcurrent flows through a protection target such as a semiconductor integrated circuit at a high temperature, it is possible to obtain an overcurrent detection circuit that can accurately prevent an accelerated temperature rise in the protection target.

According to the sixth aspect, a comparator circuit that compares a reference voltage with a comparison voltage derived according to an output current, detects a current exceeding an overcurrent limit value, and makes an overcurrent determination, An output stage circuit for stopping an output current when an overcurrent is detected by the comparator circuit is provided, and a reference voltage in the comparator circuit is set via a operational amplifier by a constant voltage source having no temperature dependency, and a variation thereof is set. By regulating, the overcurrent limit value set by the reference voltage and the comparison voltage is kept constant regardless of the temperature rise.Therefore, the reference voltage in the comparator circuit is controlled by a constant voltage source that does not have temperature dependency. When an overcurrent flows through the protection target such as a semiconductor integrated circuit at a high temperature, the acceleration It is possible to obtain an overcurrent detection circuit for a such temperature increase can be more accurately prevented.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an overcurrent detection circuit having an overcurrent limit value having a negative temperature characteristic according to a first embodiment of the present invention.

FIG. 2 is a connection diagram showing an overcurrent detection circuit having an overcurrent limit value without temperature characteristics according to a second embodiment of the present invention.

FIG. 3 is a connection diagram showing an overcurrent detection circuit according to a third embodiment of the present invention.

FIG. 4 is a connection diagram showing a conventional overcurrent detection circuit.

[Explanation of symbols]

1 Comparator circuit, 2 output stage circuit, 3 constant current circuit, 4 operational amplifier, VB power supply, Rext resistor, Qex
t output transistor, Q1-Q26 transistor, R
1 to R12 resistance, VREF constant voltage source voltage.

Continued on the front page F term (reference) 2G035 AA03 AA06 AA16 AB02 AC02 AC16 AD02 AD10 AD23 AD56 5G004 AA04 AB02 BA03 BA04 DA02 DC04 DC12 EA01

Claims (6)

[Claims] 1. A comparator circuit for comparing a reference voltage with a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value and performing an overcurrent determination, wherein the overcurrent is detected by the comparator circuit. An output stage circuit for stopping an output current when detected, and regulating at least one of a reference voltage and a comparison voltage in the comparator circuit to thereby limit an overcurrent limit value set by the reference voltage and the comparison voltage An overcurrent detection circuit characterized by preventing an increase due to a temperature rise of the overcurrent detection circuit. 2. A comparator circuit for comparing a reference voltage with a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value and performing an overcurrent determination, wherein the overcurrent is detected by the comparator circuit. An output stage circuit for stopping an output current when detected, and regulating at least one of a reference voltage and a comparison voltage in the comparator circuit to thereby limit an overcurrent limit value set by the reference voltage and the comparison voltage Is reduced as the temperature rises. 3. A comparator circuit for comparing a reference voltage with a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value and performing an overcurrent determination, wherein the overcurrent is detected by the comparator circuit. An output stage circuit for stopping an output current when detected, and supplying a bias current to the comparator circuit to regulate at least one of a reference voltage and a comparison voltage in the comparator circuit, thereby providing a reference voltage. An overcurrent detection circuit provided with a constant current circuit for reducing an overcurrent limit value set by the comparison voltage with a rise in temperature. 4. A comparator circuit for comparing a reference voltage and a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value and performing an overcurrent determination, wherein the overcurrent is detected by the comparator circuit. An output stage circuit for stopping an output current when detected, and regulating at least one of a reference voltage and a comparison voltage in the comparator circuit to thereby limit an overcurrent limit value set by the reference voltage and the comparison voltage The overcurrent detection circuit is characterized in that the current is kept constant regardless of the temperature rise. 5. A comparator circuit for comparing a reference voltage with a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value and performing an overcurrent determination, wherein the overcurrent is detected by the comparator circuit. An output stage circuit for stopping an output current when detected, a reference voltage in the comparator circuit is set by a constant voltage source having no temperature dependency, and a variation thereof is regulated, whereby a reference voltage and a comparison voltage are set. An overcurrent detection circuit characterized in that an overcurrent limit value set by the above is made constant regardless of a temperature rise. 6. A comparator circuit for comparing a reference voltage with a comparison voltage derived according to an output current, detecting a current exceeding an overcurrent limit value and performing an overcurrent determination, wherein the overcurrent is detected by the comparator circuit. An output stage circuit for stopping an output current when detected is provided, a reference voltage in the comparator circuit is set via an operational amplifier by a constant voltage source having no temperature dependency, and a variation thereof is regulated, whereby a reference voltage is set. An overcurrent detection circuit characterized in that an overcurrent limit value set by a voltage and a comparison voltage is fixed regardless of a temperature rise.