JP3570338B2 - Power supply reverse connection protection circuit - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply reverse connection protection circuit that protects an electric circuit when a power supply is reversely connected.
[0002]
[Problems to be solved by the invention]
FIG. 9 shows an example in which this kind of power supply reverse connection protection circuit is applied to an IC (integrated circuit). In FIG. 9, a diode 3 and an electric circuit 4 to be protected are connected in series between a positive power supply terminal 1 and a negative power supply terminal 2. The electric circuit 4 includes a constant current circuit 5, a current mirror circuit 6, and functional circuits 7 and 8, which are load circuits of the current mirror circuit 6, and has a circuit configuration very generally used as an IC. Has become.
[0003]
When a power supply (not shown) is normally connected (sequentially connected) to the power supply terminals 1 and 2 and a power supply voltage of a normal polarity is applied between the power supply terminals 1 and 2, the power supply Supplies a current to the electric circuit 4. On the other hand, when the power supply is reversely connected and the potential of the power supply terminal 2 is higher than the potential of the power supply terminal 1, the current is blocked by the diode 3. Therefore, even if the electric circuit 4 has a circuit configuration capable of flowing a current from the power supply terminal 2 side to the cathode side of the diode 3, no current flows in the electric circuit 4, and the electric circuit 4 is protected against power supply reverse connection. Protected.
[0004]
However, the diode 3 constituting the power supply reverse connection protection circuit needs a large current capacity because the entire operation current must flow to the electric circuit 4 in a normal operation state in which the power supply is sequentially connected. Therefore, for example, in the case of a circuit formed into an IC, the chip area increases and the cost increases. Further, even if the power supply is connected in the forward direction and the diode 3 is turned on, a forward voltage (for example, 400 mV to 800 mV) remains between the anode and the cathode of the diode 3. 4 raises the minimum power supply voltage (low-voltage operation limit) at which operation can be maintained.
[0005]
On the other hand, a power supply reverse connection protection circuit with an improved low voltage operation limit is disclosed in Japanese Patent Application Laid-Open No. 5-260652. FIG. 10 shows an application example of the power supply reverse connection protection circuit. In FIG. 10, between the power supply terminal 1 and the electric circuit 4, an emitter-collector connection of a PNP transistor 9 is connected instead of the diode 3, and a connection between the base of the transistor 9 and the power supply terminal 2 is provided. Is connected to a resistor 10.
[0006]
In this configuration, when the power supply is connected in sequence, a base current flows through the transistor 9 via the resistor 10, the transistor 9 is turned on, and the current is supplied to the electric circuit 4. On the other hand, when the power supply is reversely connected, the potential of the power supply terminal 2 is applied to the base of the transistor 9 via the resistor 10, so that a reverse bias is applied between the base and the emitter. As a result, the transistor 9 is turned off, and the electric circuit 4 is protected.
[0007]
However, even in this circuit configuration, since the transistor 9 requires a large current capacity, the problem that the chip area increases and the cost increases remains. Further, at the time of power supply forward connection, at least a saturation voltage (for example, 50 mV to 200 mV) remains between the emitter and the collector of the transistor 9. Therefore, although the low-voltage operation limit is slightly improved with respect to the configuration shown in FIG. 9, the low-voltage operation limit is still raised.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to protect an electric circuit including a current mirror circuit and a load circuit thereof when a power supply is reversely connected, and to protect the electric circuit. An object of the present invention is to provide a power supply reverse connection protection circuit which can be configured simply and at low cost and does not raise the low voltage operation limit.
[0009]
[Means for Solving the Problems]
According to the means described in claim 1, when the power supply is reversely connected and a voltage of opposite polarity is applied to the first and second power supply lines, the connection is made between the common connection line and the second power supply line. The supplied one-way energizing circuit is energized, and a current flows through the one-way energizing circuit to a bias circuit connected between the first power supply line and the common connection line. As a result, a voltage is generated at both ends of the bias circuit, and the potential of the common connection line, that is, the potential of the control terminal of each transistor constituting the current mirror circuit approaches the potential of the second power supply line. As a result, the potential difference between the main terminal (for example, collector or drain) of the transistor connected to the load circuit and the control terminal (for example, base or gate) of the transistor becomes small, and the transistor is turned off.
[0010]
That is, when the power supply is reversely connected, each transistor constituting the current mirror circuit is turned off, and the current flowing in the reverse direction is cut off to protect the electric circuit. Therefore, unlike the conventional configuration, it is not necessary to add a new element for preventing the reverse voltage when the power supply is reversely connected, and the configuration is simplified and the cost is reduced. In addition, even when an IC is used, an increase in the chip area is small.
[0011]
On the other hand, when a voltage of a predetermined polarity is applied to the first and second power supply lines from the power supply, the one-way current supply circuit is turned off. Further, the bias circuit connected between the first power supply line and the common connection line does not adversely affect the operation of the current mirror circuit. Thus, an operating current is supplied from the first power supply line to the load circuit via the current mirror circuit.
[0012]
The power supply reverse connection protection circuit is provided not between the first and second power supply lines but between the first and second power supply lines. Therefore, when the power supply is normally connected, no operating current flows through the one-way energizing circuit, and no loss occurs there. In addition, since the power supply voltage applied to the electric circuit does not decrease even if the power supply reverse connection protection circuit is added, the low voltage operation limit of the electric circuit with respect to the power supply voltage is not raised.
[0013]
According to the means described in claim 2, the one-way energizing circuit is constituted by the diode, so that the circuit configuration is simplified.
According to the third aspect of the present invention, since the one-way energizing circuit is constituted by the Schottky barrier diode having a smaller forward voltage, the potential of the control terminal of each transistor constituting the current mirror circuit when the power supply is reversely connected. Are closer to the potential of the second power supply line. Thereby, each transistor is more reliably turned off, and application of a reverse voltage to the load circuit can be prevented.
[0014]
According to the fourth aspect, the one-way energizing circuit is constituted by the bipolar transistors connected so as to equivalently constitute a diode, so that the circuit configuration is simplified.
[0015]
According to the means described in claim 5, the one-way energizing circuit is a transistor, and its control terminal is connected to the first power supply line directly or via a resistor or the like. Then, a voltage is applied between the control terminal of the transistor and the main terminal (connected to the second power supply line), and the transistor is turned on. In this ON state, the voltage between the main terminals of the transistor (for example, the voltage between the collector and the emitter, the voltage between the drain and the source: corresponding to the voltage between both ends of the one-way conduction circuit) becomes very small, and thus each of the components constituting the current mirror circuit The potential of the control terminal of the transistor becomes closer to the potential of the second power supply line. Thereby, each transistor is more reliably turned off, and application of a reverse voltage to the load circuit can be prevented.
[0016]
According to the measure described in claim 6, since the voltage between the gate of the FET and the source (connected to the second power supply line) is 0, the FET is not energized when the power supply is normally connected. State. On the other hand, when the power supply is reversely connected, the relationship between the source and the drain of the FET is switched, so that the FET is energized.
[0017]
According to the means described in claim 7, since the bias circuit is a resistor, the circuit configuration is simplified.
According to the means described in claim 8, since the power supply reverse connection protection circuit is configured as an integrated circuit having an insulation separation structure, unlike a circuit having a junction separation structure, no parasitic transistor is formed and the power supply reverse connection protection circuit is not formed. At the time of connection, a through current can be prevented from flowing.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, a first embodiment in which the power supply reverse connection protection circuit of the present invention is configured as an IC (integrated circuit) will be described with reference to FIGS.
FIG. 1 schematically shows an electrical configuration inside the IC. In FIG. 1, a positive terminal and a negative terminal of a power supply (not shown) provided outside the IC 11 are connected to a positive power terminal 12 and a negative power terminal 13 of the IC 11, respectively (sequential connection). ), The IC 11 operates by receiving the supply of the power supply voltage VB from the power supply.
[0019]
A positive power supply line 14 (corresponding to a first power supply line) and a negative power supply line 15 for supplying a power supply voltage VB to each circuit inside the IC 11 are respectively connected to the positive power supply terminal 12 and the negative power supply terminal 13. (Corresponding to a second power supply line). The positive power supply line 14 is connected to a current mirror circuit 19 including PNP transistors 16, 17, and 18. That is, the emitters of the transistors 16, 17, and 18 are connected to the positive power supply line 14, and their bases (corresponding to control terminals) are connected to a common base line 20 (corresponding to a common connection line).
[0020]
A constant current circuit 21 is connected between the collector of the transistor 16 and the negative power supply line 15, and functional circuits 22 and 23 (load circuit) are connected between the collectors of the transistors 17 and 18 and the negative power supply line 15, respectively. Is connected). Such a circuit configuration is a circuit configuration often used in an electric circuit, and particularly a general circuit configuration in an IC.
[0021]
Further, as a feature of the present embodiment, a power supply reverse including a resistor 24 (corresponding to a bias circuit) and a diode 25 (corresponding to a one-way energizing circuit) is provided between the positive power supply line 14 and the negative power supply line 15. The connection protection circuit 26 is connected. Here, the resistor 24 is connected between the positive power supply line 14 and the base line 20, and the diode 25 is connected between the base line 20 and the negative power supply line 15 with the negative power supply line 15 side as an anode. Have been.
[0022]
FIG. 2 is an electrical configuration diagram specifically showing the constant current circuit 21 and the functional circuits 22 and 23 in FIG. The constant current circuit 21 is a constant current circuit using a well-known self-bias method. The transistor 16 has two collectors. The collector and the emitter of the NPN transistor 27 are connected between one collector and the negative power supply line 15, and between the other collector and the negative power supply line 15. Is connected between the collector and the emitter of the NPN transistor 28 and the resistor 29. The resistor 30 and the emitter and collector of the PNP transistor 31 are connected between the base line 20 and the negative power supply line 15. The bases of the transistors 27, 28, 31 are connected to the emitter of the transistor 28, the collector of the transistor 27, and the collector of the transistor 28, respectively. A starting resistor 32 is connected between the positive power supply line 14 and the collector of the transistor 27.
[0023]
The functional circuit 22 connected between the collector of the transistor 17 and the negative power supply line 15 is a comparison circuit section of the comparator, and includes a differential pair including transistors 33 and 34 and a current mirror-connected transistor 35. 36 active loads. The non-inverting input terminal 37 and the inverting input terminal 38 of the IC 11 are connected to the bases of the transistors 33 and 34 via resistors 39 and 40, respectively.
[0024]
The functional circuit 23 is an output circuit section of the comparator, and is connected between the collector and the emitter of the NPN transistor 41 and between the base and the emitter of the NPN transistor 42 between the collector of the transistor 18 and the negative power supply line 15. ing. The output node of the differential pair, that is, the collector of the transistor 34 is connected to the base of the transistor 41, and the collector of the transistor 42 is connected to the output terminal 43 of the IC 11.
[0025]
The IC 11 having the above-described circuit configuration has an insulating isolation structure formed on an SOI (Silicon On Insulator) substrate. FIGS. 3A and 3B are a plan view of a lateral PNP transistor formed on an SOI substrate and a perspective view schematically showing a vertical cross section thereof along line XX.
[0026]
In FIG. 3, the SOI substrate 44 has a structure in which a single crystal silicon layer 47 is provided on a main surface of a silicon substrate 45 via a silicon oxide film 46 as an insulating film. In the silicon layer 47, a trench 48 reaching the silicon oxide film 46 from the surface is formed, and a plurality of element-forming island regions insulated and separated from each other are formed.
[0027]
A P-type emitter region 49 and a rectangular closed-loop P-type collector region 50 surrounding the emitter region 49 are formed in the surface layer of the island region by diffusion. In this case, the silicon layer 47 serves as a base region, and the base contact region 51 is formed outside the collector region 50.
[0028]
Next, the operation of the present embodiment will be described.
First, the operation when the power supply is connected to the positive power supply terminal 12 and the negative power supply terminal 13 in order will be described with reference to FIG. In this case, when a starting current flows from the positive power supply line 14 via the starting resistor 32, the transistor 28, and the resistor 29, the constant current circuit 21 starts a constant current operation. The constant current value is determined by the base-emitter voltage of the transistor 27 and the value of the resistor 29. The current is supplied from the positive power supply line 14 to the negative power supply line 15 through the transistors 16, 28 and the resistor 29. Flows. The transistor 16 causes the same current to flow through the transistor 27 as a self-bias current. That is, since the collector current of the transistor 27 is constant and the collector potential of the transistor 27 is also constant, the constant current circuit 21 is hardly affected by the fluctuation of the power supply voltage VB. Note that the transistor 31 is for flowing a base current from the base line 20.
[0029]
The constant current generated by the constant current circuit 21 is supplied to the functional circuits 22 and 23 via the current mirror circuit 19. The functional circuits 22 and 23 constitute a comparator. When the input voltage to the non-inverting input terminal 37 is higher than the input voltage to the inverting input terminal 38, the transistor 41 is turned on and the transistor 42 is turned off. When the input voltage to the inverting input terminal 37 is lower than the input voltage to the inverting input terminal 38, the transistor 41 is turned off and the transistor 42 is turned on.
[0030]
In this case, the voltage of the base line 20 is substantially (VB−Vf), where Vf is the base-emitter voltage of the transistors 16, 17, and 18, and a reverse voltage is applied to the diode 25. Therefore, the diode 25 is in the off state (non-energized state) and does not affect the operation of the comparator. Also, the resistor 24 does not adversely affect the operation of the current mirror circuit 19.
[0031]
Subsequently, the negative terminal and the positive terminal of the power supply are connected to the positive power supply terminal 12 and the negative power supply terminal 13 of the IC 11 (reverse connection), respectively, and the power supply voltage (−VB) of the opposite polarity is applied to the IC 11 from the power supply. The case where the voltage is applied will be described below. Such a reverse connection occurs, for example, when the connection between a vehicle-mounted device (not shown) equipped with the IC 11 and a battery (power supply) is incorrect.
[0032]
In this case, since the negative power supply line 15 has a higher potential than the positive power supply line 14, a forward voltage is applied to the diode 25 via the resistor 24. As a result, the diode 25 is turned on (energized state), and the voltage of the base line 20 is lower than the voltage VB of the negative power supply line 15 by Vf (VB-Vf) with the potential of the positive power supply line 14 being 0 V. It becomes.
[0033]
The transistors 16, 17, and 18 constituting the current mirror circuit 19 are of PNP type, and when a reverse voltage is applied, their collector (P-type) and base (N-type) become forward. However, a voltage substantially equal to the above-described voltage Vf is required to make a current flow between the collector and the base. Therefore, when the diode 25 is on, almost no voltage is applied to the constant current circuit 21 and the functional circuits 22 and 23.
[0034]
In addition, generally, in order for the constant current circuit 21 and the functional circuits 22 and 23 to pass a current in the opposite direction (that is, the direction from the negative power supply line 15 to the collectors of the transistors 16, 17 and 18), a voltage corresponding to the circuit configuration is required. Is required. This voltage is the collector-base voltage Vf of the transistor 31 in the case of the constant current circuit 21. Therefore, when the diode 25 is turned on and the potential difference between the negative power supply line 15 and the base line 20 becomes Vf, no current flows through the constant current circuit 21 or the functional circuits 22 and 23. In the functional circuits 22 and 23 according to the present embodiment, since all the transistors 35, 36, 41 and 42 connected to the negative power supply line 15 are of the NPN type, the current is independent of the applied reverse voltage. Not flowing.
[0035]
As a result, most of the reverse-polarity voltage VB applied between the power supply lines 14 and 15 due to the power supply reverse connection is blocked between the base (N-type) and the emitter (P-type) of the transistors 16, 17 and 18. A voltage between the base and the emitter is sufficiently higher than the power supply voltage VB (for example, 12 V to 16 V) (for example, 30 V).
[0036]
By the way, as a main structure of an IC, there are a junction separation structure in which each element is electrically separated by a reverse-biased PN junction, and an insulation separation structure in which each element is separated by an insulating film or the like.
[0037]
A PNP transistor having a junction isolation structure is schematically shown in FIG. That is, an N-type epitaxial layer 54 is formed on a P-type silicon substrate 52 with a buried layer 53 interposed therebetween, and a P-type emitter region 55, a P-type collector region 56, A base contact region 57 is formed. A P-type isolation region 58 for isolation isolation is formed between each element. The lowest potential used in the IC is applied to the silicon substrate 52 and the isolation region 58.
[0038]
However, in this junction isolation structure, in addition to the original transistor including the emitter region 55, the collector region 56, and the epitaxial layer 54 (base region), the silicon substrate 52 is used as an emitter, the epitaxial layer 54 is used as a base, and the emitter region 55 is used as a collector. There is a parasitic transistor (shown in broken lines in FIG. 4). Therefore, when the junction isolation structure is used in the circuit configuration shown in FIG. 1, a through current flows from the negative power supply line 15 to the positive power supply line 14 via the parasitic transistor when the power supply is reversely connected.
[0039]
Therefore, the IC 11 of the present embodiment uses the latter insulation separation structure as described above and shown in FIG. Since no parasitic transistor is formed in the isolation structure, a through current does not flow due to the parasitic transistor when the power supply is reversely connected.
[0040]
As described above, in the IC 11 of the present embodiment, the current mirror circuit 19 is connected to the positive power supply line 14, and the constant current circuit 21 and the functional circuit 22 are connected between the current mirror circuit 19 and the negative power supply line 15. , 23 (here, comparators) are connected. This circuit form is a general one that is frequently used in ICs, in particular, in which transistors with uniform characteristics can be easily manufactured. As a characteristic of the IC 11, a power supply reverse connection protection circuit 26 including a resistor 24 and a diode 25 is connected between the positive power supply line 14 and the negative power supply line 15.
[0041]
In this configuration, when the power supply is reversely connected to the positive power supply terminal 12 and the negative power supply terminal 13 of the IC 11, the diode 25 is turned on and the potential of the baseline 20 becomes close to the potential of the negative power supply terminal 13. Will be raised. As a result, almost no voltage is applied to the constant current circuit 21 and the function circuits 22 and 23, and the applied reverse voltage is blocked between the base and the emitter of the transistors 16 to 18 constituting the current mirror circuit 19. You. Thus, the IC 11 is protected from the application of the reverse voltage due to the power supply reverse connection.
[0042]
According to the power supply reverse connection protection circuit 26, since the current mirror circuit 19 itself blocks the reverse voltage, it is not necessary to add a new element for blocking the reverse voltage. Further, since the resistor 24 and the diode 25 only need to fix the potential of the baseline 20 at the time of reverse connection of the power supply, a large current capacity is not required. Therefore, the configuration of the power supply reverse connection protection circuit 26 is simplified, and the configuration of the power supply reverse connection protection circuit 26 can be implemented at low cost with almost no increase in chip area.
[0043]
In the normal operation in which the power supply is connected to the IC 11 in the normal operation, the power supply reverse connection protection circuit 26 does not affect the original operation of the IC 11 because the diode 25 is turned off. In addition, since the power supply reverse connection protection circuit 26 is not interposed between the positive power supply line 14 and the negative power supply line 15, a voltage drop due to an operation current does not occur at the time of forward connection. Therefore, the low voltage operation limit of the IC 11 with respect to the power supply voltage is not raised, and no loss occurs.
[0044]
(Second embodiment)
FIG. 5 shows a second embodiment of the present invention. Hereinafter, portions different from the first embodiment will be described.
That is, the IC 59 shown in this embodiment has a configuration in which a power supply reverse connection protection circuit 60 is provided instead of the power supply reverse connection protection circuit 26 in the IC 11 described above. In the power supply reverse connection protection circuit 60, the collector and the emitter of the NPN transistor 61 are connected between the base line 20 and the negative power supply line 15 instead of the diode 25. The transistor 61 corresponding to the one-way conduction circuit has a base and an emitter connected (corresponding to a diode connection in the present invention), and equivalently functions as a diode having the negative power supply line 15 side as an anode. It has become.
[0045]
When the power supply is reversely connected to the IC 59 provided with the power supply reverse connection protection circuit 60, the transistor 61 is turned on in the direction from the emitter to the collector, and the voltage of the base line 20 is higher than the voltage VB of the negative power supply line 15 by Vf. Only lower voltage. Therefore, the same operation and effect as those of the IC 11 of the first embodiment can be obtained by the IC 59 of the present embodiment.
[0046]
(Third embodiment)
FIG. 6 shows a third embodiment of the present invention. Hereinafter, portions of the third embodiment different from the first embodiment will be described.
That is, the IC 62 shown in this embodiment has a configuration in which a power supply reverse connection protection circuit 63 is provided instead of the power supply reverse connection protection circuit 26 in the IC 11 described above. In the power supply reverse connection protection circuit 63, a collector and an emitter of a PNP transistor 64 are connected between the base line 20 and the negative power supply line 15 instead of the diode 25. The base of the transistor 64 is connected to the positive power supply line 14 via the resistor 65.
[0047]
When the power supply is connected to the IC 62 in order, the power supply voltage VB is applied to the base of the transistor 64 via the resistor 65. However, since the power supply voltage VB is a reverse voltage between the base and the emitter of the transistor 64, the transistor 64 is turned off.
[0048]
On the other hand, when the power supply is reversely connected to the IC 62, a forward voltage is applied between the base and the emitter of the transistor 64 via the resistor 65, so that the transistor 64 is turned on. In this case, the voltage of the base line 20 is lower than the voltage VB of the negative power supply line 15 by the saturation voltage Vsat of the transistor 64, with the potential of the positive power supply line 14 being 0V.
[0049]
Therefore, according to the present embodiment, since the transistor 64 operates as a one-way energizing circuit, the same operation and effect as those of the first embodiment can be obtained. According to the power supply reverse connection protection circuit 63, the potential difference between the base line 20 and the negative power supply line 15 becomes the saturation voltage Vsat (<Vf) at the time of the power supply reverse connection, so that the constant current circuit 21 and the functional circuit 22 , 23 can be almost completely prevented, and more reliable power supply reverse connection protection can be achieved.
[0050]
(Fourth embodiment)
FIG. 7 shows a fourth embodiment of the present invention. Hereinafter, portions of the fourth embodiment different from the first embodiment will be described.
That is, the IC 66 shown in this embodiment has a configuration in which a power supply reverse connection protection circuit 67 is provided instead of the power supply reverse connection protection circuit 26 in the IC 11 described above. In the power supply reverse connection protection circuit 67, the drain and source of an enhancement N-channel MOSFET 68 are connected between the base line 20 and the negative power supply line 15 instead of the diode 25. The gate of the MOSFET 68 is connected to the negative power supply line 15.
[0051]
When the power supply is connected to the IC 66 in order, the voltage (VB−Vf) of the baseline 20 is applied to the drain of the MOSFET 68 via the resistor 24. However, the MOSFET 68 is turned off because its gate and source are short-circuited.
[0052]
On the other hand, when the power supply is reversely connected to the IC 66, the source and the gate have a higher potential than the drain. Since the MOSFET 68 has a symmetric structure with respect to the drain and the source, a current flows from the source to the drain in this voltage applied state, and the voltage of the base line 20 is higher than the voltage VB of the negative power supply line 15 by the voltage VTH (MOSFET 68 Threshold voltage).
[0053]
As described above, according to the present embodiment, since the MOSFET 68 operates as a one-way energizing circuit, the same operation and effect as in the first embodiment can be obtained by setting the threshold voltage VTH low. it can.
[0054]
(Fifth embodiment)
FIG. 8 shows a fifth embodiment of the present invention. Hereinafter, a description will be given of portions different from the first embodiment.
The circuit configuration inside the IC 69 is the same as the above-described circuit configuration inside the IC 11, except that the connection form between the positive power supply line 14 and the negative power supply line 15 is reversed. That is, a current mirror circuit 73 including NPN transistors 70, 71 and 72 is connected to the negative power supply line 15 (corresponding to the first power supply line), and the current mirror circuit 73 is connected to the positive power supply line 14 (corresponding to the second power supply line). A constant current circuit 74 and functional circuits 75 and 76 (corresponding to load circuits) are connected between the collectors of the transistors 70, 71 and 72, respectively. Further, between the negative power supply line 15 and the base line 77 (corresponding to a common connection line) and between the base line 77 and the positive power supply line 14, a resistor 79 (which constitutes a power supply reverse connection protection circuit 78) is provided. And a diode 80 (corresponding to a one-way energizing circuit).
[0055]
According to this configuration, when the power supply is sequentially connected to the IC 69, the diode 80 is turned off, and when the power supply is reversely connected, the diode 80 is turned on to change the potential of the base line 77 to the positive power supply line. The potential is raised to a value close to 14. Therefore, also in the present embodiment, similarly to the first embodiment, the IC 69 is protected from application of a reverse voltage due to reverse connection of the power supply.
[0056]
(Other embodiments)
The present invention is not limited to the embodiments described above and shown in the drawings. For example, the present invention can be modified or expanded as follows.
The one-way energizing circuit is not limited to elements such as a diode, a transistor, and an FET. In short, a circuit that allows current to flow only in one direction may be used. . Further, the bias circuit is not limited to the resistors 24 and 79, and may have any circuit configuration that can bias the one-way energizing circuit to the energized state when the power supply is reversely connected.
[0057]
In each embodiment, a variable current circuit or another current source may be used instead of the constant current circuits 21 and 74. Further, the functional circuits 22 and 23 are not limited to comparators. The number of transistors constituting the current mirror circuits 19 and 73 is not limited to three. Further, the current mirror circuit may be constituted by an FET.
[0058]
In the first and fifth embodiments, Schottky barrier diodes are preferably used as the diodes 25 and 80. Thereby, the potential difference between the base line 20 and the negative power supply line 15 and the potential difference between the base line 77 and the positive power supply line 14 at the time of the power supply reverse connection are further reduced, and more reliable power supply reverse connection protection can be achieved.
[0059]
In the second embodiment, when a diode-connected transistor is used as the one-way current-carrying circuit, the diode connection may be in another connection form. For example, the emitter and collector of the NPN transistor may be connected between the base line 20 and the negative power supply line 15, and the base and the collector may be connected. Further, a PNP transistor may be used instead of the NPN transistor.
[0060]
In the fourth embodiment, a circuit configuration in which the source and the drain of the P-channel MOSFET are connected between the base line 20 and the negative power supply line 15 and the gate thereof is connected to the positive power supply line 14 or the base line 20 Is also good.
In the fifth embodiment, the same configuration as in the second to fourth embodiments is possible.
[Brief description of the drawings]
FIG. 1 is a schematic electrical configuration diagram showing the inside of an IC according to a first embodiment of the present invention;
FIG. 2 is a specific electrical configuration diagram inside the IC.
FIG. 3 is a diagram schematically showing an insulation separation structure.
FIG. 4 is a diagram schematically showing a junction separation structure.
FIG. 5 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;
FIG. 6 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.
FIG. 7 is a view corresponding to FIG. 1, showing a fourth embodiment of the present invention;
FIG. 8 is a view corresponding to FIG. 1, showing a fifth embodiment of the present invention;
FIG. 9 is a diagram corresponding to FIG. 1 showing a conventional technique.
FIG. 10 is a diagram corresponding to FIG. 1 showing another conventional technique.
[Explanation of symbols]
11, 59, 62, 66, and 69 are ICs (integrated circuits), 14 is a positive power supply line (first power supply line / second power supply line), and 15 is a negative power supply line (second power supply line / second power supply line). 1, 17, 18, 18, 70, 71, and 72 are transistors, 19 and 73 are current mirror circuits, 20 and 77 are base lines (common connection lines), 22, 23, 75, and 76 are functional circuits. (Load circuit), 24 and 79 are resistors (bias circuits), 25 and 80 are diodes (unidirectional conducting circuits), 26, 60, 63, 67 and 78 are power supply reverse connection protection circuits, and 61 and 64 are transistors ( Reference numeral 68 denotes a MOSFET (unidirectional energizing circuit).

Claims (8)

A first and a second power supply line to which a voltage of a predetermined polarity is applied from a power supply, a current mirror circuit including a plurality of transistors connected to the first power supply line, the transistors and the second power supply line A power supply reverse connection protection circuit that protects the electric circuit when the power supply is reversely connected,
A unidirectional current-carrying circuit connected between a common connection line between control terminals of the transistors and the second power line so as to be energized when the power is reversely connected;
A power supply reverse connection protection circuit, comprising: a bias circuit connected between the first power supply line and the common connection line. The power supply reverse connection protection circuit according to claim 1, wherein the one-way energization circuit is a diode. 3. The power supply reverse connection protection circuit according to claim 2, wherein the one-way energization circuit is a Schottky barrier diode. The power supply reverse connection protection circuit according to claim 1, wherein the one-way energization circuit is a diode-connected bipolar transistor. The power supply reverse connection protection circuit according to claim 1, wherein the one-way energization circuit is a transistor, and a control terminal thereof is connected to the first power supply line. 2. The power supply reverse connection protection circuit according to claim 1, wherein the one-way energization circuit is an FET, and a gate thereof is connected to the second power supply line. The power supply reverse connection protection circuit according to any one of claims 1 to 6, wherein the bias circuit is a resistor. 8. The power supply reverse connection protection circuit according to claim 1, wherein the protection circuit is configured as an integrated circuit having an insulation isolation structure.

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