JP2011259627A - Power supply reverse connection protective circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply reverse connection protective circuit which can recognize the reverse connection of an external DC power supply and the application of a negative surge and can surely prevent the generation of an overcurrent in an electronic control device.SOLUTION: The power supply reverse connection protective circuit includes a rectifier 12 connected to a low electrical potential side terminal 3 and a high electrical potential side terminal 2 of an external DC power supply. A high electrical potential side node 13 and a low electrical potential side node 14 of the rectifier 12 are connected to a reverse connection protection control circuit 11. Even when the polarity of the external DC power supply is reversed, the rectifier 12 generates a high electrical potential at the high electrical potential side node 13 and a low electrical potential at the low electrical potential side node 14. Accordingly, a comparator 15 of the reverse connection protection control circuit 11 determines whether the external DC power supply is reversely connected to a power supply terminal 3 and a ground terminal 5, and a reverse connection protective element drive circuit 16 surely turns off a reverse connection protective element 10. As a result, an overcurrent from the ground terminal 5 to the power supply terminal 3 is surely prevented.

Description

  The present invention relates to a power supply reverse connection protection circuit that detects when a power supply is reversely connected to an electronic control device in the reverse direction of an external DC power supply and protects the electronic control device from an overcurrent.

  In general, when an external DC power source such as a battery is connected to an electronic device such as an in-vehicle electronic control device, if the power source is connected in reverse polarity due to an incorrect connection or the like, an element mounted on the electronic device Overcurrent may occur and damage may occur. This is because, for example, when an electronic control device or the like configures a load drive circuit using a MOS transistor as a drive element, the MOS transistor has a parasitic diode due to its structure, and thus the forward bias is applied to the parasitic diode, This is because an overcurrent occurs.

  Therefore, conventionally, a protection circuit has been provided in order to protect the electronic control device when the external DC power source such as a battery is reversely connected.

  For example, a diode having a power supply terminal side of the DC power supply as an anode and a cathode as the electronic control device side is connected between the power supply terminal of the DC power supply and the electronic control device (ie, power supply wiring). When the polarity of the DC power source is connected in reverse, a reverse bias is applied to the diode to cut off the backflow of current and avoid destruction of the electronic control unit.

  In addition, a fuse is connected between the power supply terminal of the DC power supply and the electronic control device, a diode is connected between the fuse and the electronic control device as a cathode, and a ground terminal of the DC power supply is connected as an anode. Due to the connection, when the DC power source is connected in reverse, an overcurrent is generated from the ground terminal through the diode, the fuse is blown, the overcurrent is interrupted, and the electronic control It is done to avoid destruction of the device.

  However, in the conventional technique, in the method of cutting off the overcurrent by the diode, a current is always generated in the diode when the power supply is normally connected, so that a voltage drop occurs, and the operating voltage of the electronic control device decreases. There was a problem that the diode generated heat.

  Further, in the method of interrupting overcurrent with a fuse, there is a problem that even if the connection of the DC power supply is restored after the fuse is blown, the electronic control unit cannot be driven until the fuse is replaced.

  Therefore, conventionally, for example, in Patent Document 1, a reverse connection protection FET that protects the electronic control device from the reverse connection of the external DC power supply is connected in series to the electronic control device, and when the DC power supply is normally connected, A power supply reverse connection protection circuit is described in which the reverse connection protection FET is turned on and the reverse connection protection FET is turned off during reverse connection. In this power supply reverse connection protection circuit, specifically, when the external DC power supply is normally connected, the comparator recognizes that the connection is normal, boosts the potential by the charge pump circuit, and completes the reverse connection protection FET. By turning on, the resistance value in the reverse connection protection FET is limited to a very small value, and the power loss in the reverse connection protection FET is reduced. On the other hand, at the time of reverse connection, the charge pump circuit is stopped to prevent the electronic control device from generating an overcurrent in the direction opposite to that during normal operation without generating a signal to turn on the reverse connection protection FET. Is configured to do.

JP 2007-82374 A (page 13, FIG. 5, etc.)

  However, in the configuration of Patent Document 1, the charge pump circuit does not perform step-up operation when the power supply is reversely connected, but the reverse connection protection FET is not necessarily turned on. This is because the source terminal of the reverse connection protection FET is a power supply terminal of the electronic control device, and is a ground potential at the time of reverse connection. In order to prevent the reverse connection protection FET from being turned on, the control terminal needs to be lower than the threshold potential, but the power supply potential applied from the ground terminal of the electronic control device passes through the internal element to the control terminal. Since there is a possibility that the reverse connection protection FET is turned on, there is a problem that overcurrent cannot be reliably prevented.

  In the configuration of Patent Document 1, when a negative surge is applied to an external DC power source such as a battery during normal connection, the potential boosted by the charge pump circuit remains at the control terminal of the reverse connection protection FET. Therefore, there is a possibility that the reverse connection protection FET may be turned on.Therefore, as in the reverse connection, an overcurrent may occur from the ground terminal of the electronic control unit to the power supply terminal. It has a problem that it is impossible to reliably prevent the occurrence of.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a power supply reverse connection protection circuit that can reliably prevent the occurrence of overcurrent even when an external DC power supply is reversely connected or when a negative surge is applied. There is to do.

  In order to solve the above problems, in the present invention, in a power supply reverse connection protection circuit having a reverse connection protection element such as an FET, the operation of the comparator and reverse connection protection element control circuit provided is performed at the time of power supply reverse connection or negative surge. A configuration including a rectifier that rectifies the current from the external DC power supply is adopted for normal operation as in normal connection when applied.

  Specifically, the power supply reverse connection protection circuit according to the first aspect of the present invention is configured to connect a high potential side terminal and a low potential side terminal of an external DC power supply to a power supply terminal and a ground terminal, and the power supply terminal and the ground terminal. A power supply reverse connection protection circuit that protects against reverse connection of the external DC power supply to the power supply terminal and the ground terminal when power is supplied from an external DC power supply to a load connected to A reverse connection protection element connected in series with the load with respect to the external DC power supply, a rectifier connected to the power supply terminal and the ground terminal and rectified, and operated with a voltage rectified by the rectifier, and the external DC And a reverse connection protection element control circuit for recognizing a connection state of the power supply to the power supply terminal and the ground terminal and controlling an ON operation and an OFF operation of the reverse connection protection element.

  According to a second aspect of the present invention, in the power supply reverse connection protection circuit according to the first aspect, the rectifier is a diode bridge rectifier having four diodes, and two rectifiers connected to the power supply terminal and the ground terminal. A high potential side node for generating a high potential after rectification and a low potential side node for generating a low potential after rectification, wherein the high potential side node and the low potential side node are the reverse connection protection element It is connected to a control circuit.

  According to a third aspect of the present invention, in the power supply reverse connection protection circuit according to the second aspect, the reverse connection protection element includes an IGBT or a MOS transistor.

  According to a fourth aspect of the present invention, in the power supply reverse connection protection circuit according to the first aspect, the rectifier has only two diodes for generating a low potential and a low potential side node, and the reverse connection protection element Has a configuration in which the diode is connected in the reverse direction when the DC power supply is reversely connected, and the load has a configuration in which the diode is connected in the forward direction when the DC power supply is reversely connected. The component that becomes the diode connection in the reverse direction and the component that becomes the diode connection in the forward direction at the load function as two diodes for generating a high potential in the rectifier, and the reverse connection protection A connection point between an element and the load is connected to the reverse connection protection element control circuit as a high potential side node of the rectifier.

  According to a fifth aspect of the present invention, in the power supply reverse connection protection circuit according to the first aspect, the rectifier includes only two diodes for generating a high potential and a high potential side node, and the reverse connection protection element Has a configuration in which the diode is connected in the reverse direction when the DC power supply is reversely connected, and the load has a configuration in which the diode is connected in the forward direction when the DC power supply is reversely connected. The component that becomes the diode connection in the reverse direction and the component that becomes the diode connection in the forward direction at the load function as two diodes for generating a low potential in the rectifier, and the reverse connection protection A connection point between an element and the load is connected to the reverse connection protection element control circuit as a low potential side node of the rectifier.

  According to a sixth aspect of the present invention, in the power supply reverse connection protection circuit according to the fourth or fifth aspect, the reverse connection protection element includes an NMOS transistor or a PMOS transistor.

  The invention according to claim 7 is the power supply reverse connection protection circuit according to any one of the first to sixth aspects, wherein the reverse connection protection element control circuit includes a high potential side terminal and a low potential of the external DC power supply. A comparator connected to the side terminal for recognizing reverse connection of the external DC power supply, and controlling the voltage of the control terminal of the reverse connection protection element based on the output of the comparator, And a reverse connection protection element driving circuit for switching between an on operation and an off operation.

  According to an eighth aspect of the present invention, in the power supply reverse connection protection circuit according to any one of the first to seventh aspects, when the reverse connection element control circuit recognizes the reverse connection of the DC power supply, It further has a function of outputting.

  As described above, according to the first to eighth aspects of the present invention, when the external DC power supply is normally connected, the reverse connection protection element is controlled to be low resistance so as to suppress power loss while the external DC power supply is reversely connected. When a negative surge is applied, the output of the rectifier outputs the same voltage as when the power supply is normally connected, so the reverse connection protection element control circuit operates normally, and the reverse connection protection element is reliably turned off and overcurrent is supplied to the load. Does not occur. Therefore, it is surely protected against reverse connection of the external DC power supply and application of negative surge.

  In particular, in the inventions according to claims 4 and 5, the component part that is a diode connection between the reverse connection protection element and the load functions as two diodes for high potential generation or low potential generation of the rectifier to rectify. Therefore, two rectifier elements are not necessary, and the number of parts of the rectifier can be reduced.

  According to the sixth aspect of the invention, the N-channel MOS transistor is an element having a parasitic diode by connecting the back gate and the source terminal, and is an element having a relatively low ON resistance. In particular, power loss during normal connection can be reduced. On the other hand, the P-channel MOS transistor is an element having a parasitic diode by connecting the back gate terminal and the source terminal, and the P-channel MOS transistor is not more than the potential of the high potential side terminal of the external DC power supply as an ON control signal. Therefore, it is possible to reduce the area without requiring a circuit such as a booster circuit for the on-control.

  According to the seventh aspect of the invention, when the external DC power supply is normally connected, the comparator recognizes that the external DC power supply is normally connected, and the reverse connection protection element driving circuit controls the reverse connection protection element to be on. Therefore, while keeping power loss low, when the external DC power supply is reversely connected, the comparator correctly recognizes that the power supply is reversely connected, and the reverse connection protection element drive circuit ensures that the reverse connection protection element is securely connected. Since the off control is performed, it is possible to reliably prevent an overcurrent from occurring in the load.

  In addition, in the invention according to claim 8, when the external DC power supply is reversely connected, the warning signal is output to the other electronic control device, so that the other electronic control device can stop the operation. In this electronic control device, the number of circuits for recognizing reverse connection of the external DC power supply can be reduced, and the area can be saved.

  As described above, the power supply reverse connection protection circuit of the present invention turns on the reverse connection protection element when the power supply is normally connected to reduce power loss, and when the power supply reverse connection or negative surge is applied, Since the reverse connection protection element can be reliably controlled to be turned off, an overcurrent is not generated, and an effect of reliably protecting the electronic control device from destruction can be obtained.

It is a block block diagram which shows the whole structure of the power supply reverse connection protection circuit in Embodiment 1 of this invention. It is a figure which shows the detailed internal structure of the same power supply reverse connection protection circuit. It is a figure which shows the modification of the same power supply reverse connection protection circuit. It is a block block diagram which shows the whole structure of the power supply reverse connection protection circuit in Embodiment 2 of this invention. It is a figure which shows the detailed internal structure of the same power supply reverse connection protection circuit. It is a block block diagram which shows the whole structure of the power supply reverse connection protection circuit in Embodiment 3 of this invention. It is a figure which shows the detailed internal structure of the same power supply reverse connection protection circuit. It is a figure which shows the modification of the same power supply reverse connection protection circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, since the component which attached | subjected the same code | symbol in the following embodiment performs the same operation | movement, re-explanation may be abbreviate | omitted.

(Embodiment 1)
FIG. 1 is a block diagram of a power supply reverse connection protection circuit according to this embodiment.

  In the figure, reference numeral 7 denotes a power supply reverse connection protection circuit, and 1 denotes an electronic control device comprising a load 6 connected to the power supply reverse connection protection circuit 7. The electronic control device 1 includes a power supply terminal 3 connected to the high potential side terminal 2 of the external DC power supply B and a ground terminal 5 connected to the low potential side terminal 4 of the external DC power supply B.

  In the electronic control unit 1, one end of the load 6 is connected to the ground terminal 5, and the other end is connected to the output terminal 8 of the power supply reverse connection protection circuit 7. The input terminal 9 of the power supply reverse connection protection circuit 7 is connected to the power supply terminal 3. Therefore, in the electronic control unit 1, the high potential of the external DC power supply B is applied to the load 6 through the power supply terminal 3 and the power supply reverse connection protection circuit 7 to supply power.

  In the power supply reverse connection protection circuit 7, a reverse connection protection element 10 is connected between the input terminal 9 and the output terminal 8. The output terminal of the reverse connection protection element control circuit 11 is connected to the control terminal of the reverse connection protection element 10.

  The power supply reverse connection protection circuit 7 includes a rectifier 12. The rectifier 12 receives the voltage between the power supply terminal 3 and the ground terminal 5, its high potential side node 13 is connected to the power supply terminal of the reverse connection protection control circuit 11, and its low potential side node 14 is The reverse connection protection control circuit 11 is connected to the ground terminal.

  A detailed circuit configuration diagram of the power supply reverse connection protection circuit 7 is shown in FIG.

  In the figure, the reverse connection protection element control circuit 11 includes a comparator 15 and a reverse connection protection element drive circuit 16. Their power terminals are connected to the high potential side node 13 of the rectifier 12 and their ground terminals are connected to the low potential side node 14 of the rectifier 12.

  The comparator 15 is connected to the power supply terminal 3 and the ground terminal 5 on its input side, and outputs a voltage comparison result between the terminals 3 and 5 to the reverse connection protection element driving circuit 16. The reverse connection protection element driving circuit 16 drives the reverse connection protection element 10 in accordance with a signal from the comparator 15.

  In FIG. 2, the reverse connection protection element 10 is configured by an N-channel MOS transistor 17, and the rectifier 12 is configured as a diode bridge rectifier that has four diodes D1 to D4 and performs full-wave rectification. The N channel MOS transistor 17 as the reverse connection protection element 10 has a source terminal connected to the input terminal 9 of the power supply reverse connection protection circuit 7 so as to protect the parasitic diode PD having the structure from the reverse connection of the external DC power supply B. The drain terminal is connected to the output terminal 8 of the power supply reverse connection protection circuit 7. Further, although not shown, the reverse connection protection element control circuit 11 includes an oscillation circuit and a capacitor group charged and discharged by oscillation of the oscillation circuit. A boosted voltage having a higher potential than the high potential side terminal 2 of the DC power supply B is output, and this boosted voltage is applied to the control terminal (gate terminal) of the reverse connection protection element 10 (N-channel MOS transistor 17). The reverse connection protection element 10 is turned on. The reverse connection protection element control circuit 11 further includes a resistor (not shown) for connecting the gate and source of the reverse connection protection element 10 (N-channel MOS transistor 17), and its control terminal (gate The reverse charge protection element 10 is turned off in the initial state by causing the boosted charge remaining on the source terminal to flow through the resistor to the source terminal to make the gate-source equipotential, and to avoid unstable operation. Yes.

  The operation of the power supply reverse connection protection circuit 7 configured as described above will be described below.

  When the external DC power supply B is normally connected, that is, as indicated by a broken line in FIG. 1, the power supply terminal 3 is connected to the high potential power supply terminal 2 of the external DC power supply B, and the low potential power supply terminal 4 of the external DC power supply B is connected. When the ground terminal 5 is normally connected to the high potential side node 13 by the rectifier 12, the high potential is rectified to the high potential (this high potential is equal to the forward voltage of the diode D1 from the potential of the power supply terminal 3). Is output). Further, a low potential (a potential that is higher than the potential of the ground terminal 5 by the forward voltage of the diode D4) is output to the low potential side node 14 of the rectifier 12. As a result, the comparator 15 and the reverse connection protection element driving circuit 16 apply a high potential rectified by the rectifier 12 to their power supply terminals and apply a low potential rectified by the rectifier 12 to their ground terminals. Thus, a normal operation state is obtained.

  At this time, the comparator 15 compares the potentials of the power supply terminal 3 and the ground terminal 5 with each other. Since the power supply terminal 3 has a higher potential than the ground terminal 5 in the normal power supply connection state, the comparator 15 recognizes the normal power supply connection state and outputs an ON signal to the reverse connection protection element driving circuit 16.

  The reverse connection protection element drive circuit 16 receiving the ON signal from the comparator 15 outputs an ON drive signal in order to drive the reverse connection protection element 10 in the ON resistance region. This ON drive signal is a voltage obtained by boosting the source terminal voltage of the reverse connection protection element 10 (N-channel MOS transistor 17) (that is, the voltage of the input terminal 9 of the power supply reverse connection protection circuit 7) by the oscillation circuit and the capacitor group. Yes, and output to the control terminal of the reverse connection protection element 10. As a result, the reverse connection protection element 10 (N-channel MOS transistor 17) is turned on, and a potential equivalent to the potential of the high potential side terminal 2 of the external DC power supply B is output to the output terminal 8 of the power supply reverse connection protection circuit 7. Is done.

  As described above, when the external DC power supply B is normally connected, the reverse connection protection element control circuit 11 recognizes that the power supply is normally connected and generates a signal for turning on the reverse connection protection element 10. The connection protection element 10 is turned on.

  Next, when the external DC power supply B is reversely connected, that is, the low potential side terminal 4 of the external DC power supply B is connected to the power supply terminal 3, and the high potential side terminal 2 of the external DC power supply B is connected to the ground terminal 5. The reverse connection state will be described.

  The rectifier 12 outputs, as a rectified high potential, to the high potential side node 13, a potential that is a voltage drop from the potential of the ground terminal 5 by the forward voltage of the diode D 2, and is rectified to the low potential side node 14. As a low potential, a potential higher than the potential of the power supply terminal 3 by the forward voltage of the diode D3 is output. As a result, similarly to the normal connection of the external DC power supply B, the comparator 15 and the reverse connection protection element driving circuit 16 are applied with the high potential rectified by the rectifier 12 to their power supply terminals. A low potential rectified by the rectifier 12 is applied to the terminal, and a normal operation state is obtained.

  At this time, the comparator 15 compares both potentials of the power supply terminal 3 and the ground terminal 5. Since the power supply terminal 3 is at a lower potential than the ground terminal 5 in the reverse connection state of the external DC power supply B, the comparator 15 recognizes the reverse connection state of the external DC power supply B and turns off the off signal into the reverse connection protection element. Output to the drive circuit 16.

  In the reverse connection protection element drive circuit 16 that has received the off signal from the comparator 15, the reverse connection protection element 10 (N channel MOS) is operated in order to operate normally by the normal supply of the power supply voltage and to turn off the reverse connection protection element 10. The potential of the input terminal 9 of the power supply reverse connection protection circuit 7 which is the source terminal voltage of the transistor 17) is output to the control terminal of the reverse connection protection element 10, and the reverse connection protection element 10 is kept completely off. At this time, since the parasitic diode PD of the reverse connection protection element 10 is reverse-biased, no reverse current flows from the ground terminal 5 through the load 6 to the power supply terminal 3.

  Therefore, even when the external DC power supply B is reversely connected, the reverse connection protection element control circuit 11 recognizes the reverse connection state of the external DC power supply B normally and outputs a signal for turning off the reverse connection protection element 10. The connection protection element 10 is securely turned off.

  Next, a case will be described in which a negative surge is applied to the high potential side terminal 2 of the external DC power supply B in a normal connection state of the external DC power supply B, resulting in a power supply reverse connection state.

  In the normal connection state of the external DC power supply, as described above, the reverse connection protection element drive circuit 16 controls the reverse connection protection element 10 so that the boost voltage higher than the voltage of the high potential side terminal 2 of the external DC power supply B is controlled. Applied to the terminal.

  Here, when switching from the normal power supply state to the reverse power supply state by applying a negative surge, the voltage is accumulated in a boosting capacitor (not shown) in the reverse connection protection element driving circuit 16. In this case, the reverse connection protection element control circuit 11 recognizes the power supply reverse connection state and supplies the power to the control terminal of the reverse connection protection element 10 in the same way as the power supply reverse connection state described above. Since the potential of the input terminal 9 of the reverse connection protection circuit 7 is output and the gate-source voltage of the reverse connection protection element 10 (N-channel MOS transistor 17) is equalized, the reverse connection protection element 10 is switched off. Be controlled. Therefore, even when a negative surge is applied, the breakdown due to the generation of the reverse current can be reliably prevented.

  Further, if a configuration in which a signal that recognizes the reverse connection state of the power supply by the reverse connection protection element control circuit 11 is output as a warning signal 19 to another circuit, the other circuit recognizes that the electronic control unit 1 is in an abnormal state. It is possible to switch to the protection state in other circuits as well. For example, if a DC power source such as a battery is erroneously reversely connected to an electronic device such as an on-vehicle electronic control device and does not operate, the cause of non-operation by this warning signal 19 is determined to be due to reverse connection, It is also possible to reconnect to a normal connection.

  In addition, for example, when there are a plurality of electronic control units using the same DC power supply, the warning signal 19 is used to delete a component that recognizes reverse connection such as the comparator 15 from other electronic control units. It is possible to reduce the area.

  As described above, according to the present embodiment, the reverse connection protection element control circuit 11 can be operated normally by the rectifier 12 and the reverse connection can be recognized even when the external DC power supply B is reversely connected or when a negative surge is applied. Since it did in this way, the reverse connection protection element 10 can be reliably turned off, the occurrence of overcurrent can be prevented, and the electronic control device can be protected from destruction.

  In this embodiment, the comparator 15 recognizes the reverse connection of the external DC power supply B and outputs an OFF signal. However, the potential of the power supply terminal 3 and the potential of the ground terminal 5 are not always reversed. There is no need to provide such a configuration, and an off signal may be output when the potential difference between the terminals 3 and 5 becomes a predetermined potential difference.

  Further, according to the present embodiment, the N channel MOS transistor 17 is described as the reverse connection protection element 10, but the N channel MOS transistor 17 is not necessarily used. For example, as shown in FIG. Of course, other transistor elements such as a channel MOS transistor 18 or an IGBT without a parasitic diode may be used. Since the on-resistance value of the N-channel MOS transistor is generally smaller than the on-resistance value of the P-channel MOS transistor, it is possible to suppress power loss. However, when an N-channel MOS transistor is used, in order to turn it on, it is necessary to generate a voltage higher than the voltage of the high potential side terminal 2 of the external DC power supply B by a booster circuit or the like, which increases the circuit scale. However, when a P-channel MOS transistor is used, such a circuit is not necessary, and there is an advantage that it can be controlled to ON by, for example, resistance division.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.

  FIG. 4 is a block diagram of the power supply reverse connection protection circuit according to this embodiment.

  In the figure, reference numeral 7 denotes a power supply reverse connection protection circuit, and 21 denotes an electronic control device comprising a load 6 connected to the power supply reverse connection protection circuit 7.

  The power supply reverse connection protection circuit 7 in the figure is different from the power supply reverse connection protection circuit 7 shown in FIG. 1 as follows. That is, in FIG. 1, the high potential side node 13 that is the output of the rectifier 12 is connected to the power supply terminal of the reverse connection protection element control circuit 11, but in FIG. 4, the high potential side node 13 of the rectifier 12 is provided. The difference is that the output terminal 8 of the power supply reverse connection protection circuit 7 is connected to the power supply terminal of the reverse connection protection element control circuit 11. Further, as the load 6, for example, an H bridge circuit 22 for driving a motor is illustrated as shown in FIG. 5. MOS transistors are used as the driving elements of the H-bridge circuit 22, and generally two pairs of MOS transistors connected in series are prepared as shown in FIG. Each connection point of the MOS transistor series circuit is connected by an inductive load (motor M).

  Furthermore, the diode rectifier 12 is composed of only two diodes D3 and D4 for generating a low potential. That is, in the present embodiment, the two diodes for generating the high potential constituting the rectifier 12 are the parasitic diode PD of the reverse connection protection element 10 (N-channel MOS transistor 17) and the load 6 (H bridge for driving the motor). The circuit 22) is composed and shared by the parasitic diodes PD1 to PD4 of the four MOS transistors. Accordingly, the output terminal 8 of the power supply reverse connection protection circuit 7 functions as a high potential side node of the rectifier 12 and is connected to the power supply terminal of the reverse connection protection element control circuit 11.

  Next, the operation of this embodiment will be described.

  As described above, since the MOS transistor has a parasitic diode due to its structure, when a voltage higher than “the number of MOS transistor stages × the forward voltage of the diode (hereinafter referred to as Vf)” is applied due to reverse power connection. Overcurrent occurs. In the example of the H-bridge circuit 22, an overcurrent is generated when the voltage is 2 Vf or more.

  In the normal connection state of the external DC power supply in which the high potential side terminal 2 of the external DC power supply is connected to the power supply terminal 3 and the low potential side terminal 4 of the external DC power supply is connected to the ground terminal 5, the reverse connection protection element is connected from the power supply terminal 3 10 through the parasitic diode PD, and then from the output terminal (high potential side node of the rectifier 12) 8 of the power supply reverse connection protection circuit 7 through the reverse connection protection element control circuit 11 and from the low potential side node 14 of the rectifier 12 to the rectifier. The power is passed through the 12 low-potential generation diode D4 and the path to the ground terminal 5.

  Simultaneously with the energization, a high potential (specifically, a potential that drops by Vf from the potential of the power supply terminal 3) is generated at the output terminal (high potential side node of the rectifier 12) 8 of the power supply reverse connection protection circuit 7. . Further, a low potential (specifically, a potential that is higher than the potential of the ground terminal 5 by Vf) is output to the low potential side node 14 of the rectifier 12. Thereby, the comparator 15 and the reverse connection protection element driving circuit 16 are in a normal operation state.

  At this time, the comparator 15 compares the potential of the power supply terminal 3 with the potential of the ground terminal 5. Since the power supply terminal 3 has a higher potential than the ground terminal 5 in the normal power supply connection state, the comparator 15 recognizes the normal power supply connection state and outputs an ON signal to the reverse connection protection element drive circuit 16.

  The reverse connection protection element drive circuit 16 that has received the ON signal from the comparator 15 outputs an ON control signal in order to control the reverse connection protection element 10 in the ON resistance region. Since the reverse connection protection element 10 is an N channel MOS transistor 17, the reverse connection protection element driving circuit 16 boosts the voltage at the input terminal 9 of the power supply reverse connection protection circuit 7, which is the source terminal voltage of the N channel MOS transistor 17. , And output to the gate terminal (control terminal) of the N-channel MOS transistor 17. As a result, the reverse connection protection element 10 is turned on, and a potential equivalent to the potential of the high potential side terminal 2 of the external DC power supply is output to the output terminal 8 of the power supply reverse connection protection circuit 7.

  Therefore, when the power supply is normally connected, the reverse connection protection element control circuit 11 recognizes that the power supply is normally connected, generates a signal for turning on the reverse connection protection element 10, and controls the reverse connection protection element 10 to be on. .

  Next, a power reverse connection state in which the low potential side terminal 4 of the external DC power supply is mistakenly connected to the power supply terminal 3 and the high potential side terminal 2 of the external DC power supply is connected to the ground terminal 5 will be described.

  From the ground terminal 5 through the parasitic diodes PD1 to PD4 of the MOS transistor in the H-bridge circuit 22 of the load 6, and then from the output terminal (high potential side node of the rectifier 12) 8 of the power supply reverse connection protection circuit 7 The circuit 11 is energized through a path from the low voltage side node 14 of the rectifier 12 to the low potential generation diode D3 of the rectifier 12 to the power supply terminal 3.

  Simultaneously with this energization, a high potential (specifically, a potential dropped by 2 Vf from the potential of the ground terminal 5) is generated at the output terminal 8 of the power supply reverse connection protection circuit 7, and the low potential side node 14 of the rectifier 12. A low potential (specifically, a potential that is higher than the potential of the power supply terminal 3 by Vf) is output to be equal to the potential in the normal connection state. Thereby, the comparator 15 and the reverse connection protection element driving circuit 16 are in a normal operation state.

  At this time, the comparator 15 compares the potential of the power supply terminal 3 with the potential of the ground terminal 5. In the power supply reverse connection state, the power supply terminal 3 has a lower potential than the ground terminal 5, so the comparator 15 recognizes the power supply reverse connection state and outputs an off signal to the reverse connection protection element drive circuit 16.

  The reverse connection protection element drive circuit 16 that has received the OFF signal from the comparator 15 applies the voltage at the input terminal 9 of the power supply reverse connection protection circuit 7, which is the source terminal voltage of the N channel MOS transistor 17, to the N channel MOS transistor 17. Output to the gate terminal to keep the reverse connection protection element 10 completely in the OFF state. At this time, since the parasitic diode PD of the reverse connection protection element 10 is reverse biased, no reverse current is generated.

  Therefore, at the time of reverse connection of the power supply, the reverse connection protection element control circuit 11 surely recognizes that the power supply is reversely connected, and outputs a signal for turning off the reverse connection protection element 10, so that the reverse connection protection element 10 is reliably turned off.

  Subsequently, a case where a negative surge is applied to the high potential side terminal 2 of the DC power supply from the power supply normal connection state to cause a power supply reverse connection state will be described.

  In the normal power supply connection state, as described above, a voltage boosted from the potential of the high potential side terminal 2 of the external DC power supply is applied to the control terminal of the reverse connection protection element 10.

  Here, when switching from the normal power supply connection state to the reverse power supply state by applying a negative surge, the charge accumulated in the capacitor in the reverse connection protection element driving circuit 16 is retained. The connection protection element control circuit 11 operates normally in the same manner as the power supply reverse connection state, and the potential of the input terminal 9 of the power supply reverse connection protection circuit 7 (the source of the N-channel MOS transistor 17 is connected to the control terminal of the reverse connection protection element 10. Therefore, the reverse connection protection element 10 is surely controlled to be turned off. Therefore, even when a negative surge is applied, it is possible to prevent destruction due to the generation of reverse current.

  Furthermore, if the signal for recognizing the reverse power connection state by the reverse connection protection element control circuit 11 is output as a warning signal 19 to another circuit, the other circuit can recognize that the electronic control unit 1 is in an abnormal state. Other circuits can be similarly switched to the protection state. For example, when a DC power source such as a battery is reversely connected to an electronic device such as an in-vehicle electronic control device and does not operate, it is normal that the cause of non-operation by the warning signal 19 is due to the reverse connection. It is also possible to reconnect to the connection. Further, for example, when there are a plurality of electronic control devices using the same DC power supply, a configuration having a function of recognizing reverse connection such as the comparator 15 from other electronic control devices by using the warning signal 19. Since it can be deleted, the area can be saved.

  As described above, according to the present embodiment, the two high-potential generation diodes of the rectifier 12 include the diode-connected component part of the reverse connection protection element 10 and the diode-connected component part of the load 6. Since the output terminal 8 of the power supply reverse connection protection circuit 7 is used as a high potential side node of the rectifier 12, the reverse connection is made even when the power supply is reversely connected or when a negative surge is applied, as in the first embodiment. Since the protection element control circuit 11 can be operated normally and the reverse connection or the like can be recognized normally, the reverse connection protection element 10 can be reliably turned off to prevent the occurrence of overcurrent, and the electronic control device can be destroyed. It can be surely protected.

  The diode connection component included in the reverse connection protection element 10 and the diode connection component included in the load 6 may be any of the arranged diode itself or a parasitic diode.

  Furthermore, in this embodiment, compared with the first embodiment, two diodes (rectifier elements) for generating a high potential of the rectifier 12 are not required, and the number of components can be reduced.

  In this embodiment, the comparator 15 recognizes reverse connection and outputs an off signal. However, the potential of the power supply terminal 3 and the potential of the ground terminal 5 do not necessarily need to be reversed. A configuration may be adopted in which an off signal is output when the potential difference between the children reaches a predetermined potential difference.

  In the present embodiment, the H bridge circuit 22 is used as the load 6. However, the H bridge circuit 22 is not necessarily used, and a motor drive device having at least one pair of MOS transistor series circuits, a power source There is a path for diode connection in the forward direction when the power supply is reversely connected, such as a power supply circuit in which an inductive load is connected to the connection point of the device, buffer circuit, MOS transistor and diode. Any load can be applied.

  In the present embodiment, the N-channel MOS transistor 17 is used as the reverse connection protection element 10, but the N-channel MOS transistor 17 is not necessarily used. For example, a P-channel MOS transistor or a parasitic diode is used. Other transistor elements may be used. Since the on-resistance value of the N-channel MOS transistor is generally smaller than the on-resistance value of the P-channel MOS transistor, it is possible to suppress power loss. However, when an N-channel MOS transistor is used, the booster circuit It is necessary to generate a voltage equal to or higher than the voltage at the high potential side terminal 2 of the external DC power supply, etc., which leads to an increase in circuit scale, but such a booster circuit is necessary when using a P-channel MOS transistor. For example, it can be controlled to ON by resistance division or the like.

(Embodiment 3)
Subsequently, a third embodiment of the present invention will be described.

  As described above, N-channel MOS transistor elements generally have lower on-resistance than P-channel MOS transistors, but if a reverse connection protection element is provided on the power supply terminal side, a voltage generation circuit such as a booster circuit is required. It becomes. On the other hand, when a reverse connection protection element is provided on the ground terminal side, it is possible to control below the potential applied from the power supply terminal, so that a booster circuit is not required.

  In general, in an electronic control device, it is desirable to reduce the impedance of the ground wiring as much as possible for the purpose of improving noise resistance performance or matching input / output potentials with other devices. However, when the on-resistance is sufficiently small, the value of the current generated in the load is relatively small, and the voltage drop at the reverse connection protection element is negligibly small, the above problem does not pose a problem.

  That is, by providing the reverse connection protection element on the ground terminal side, it is possible to configure an electronic control device with low on-resistance and reduced parts.

  In the third embodiment, the case where the power supply reverse connection protection circuit is arranged on the ground terminal side in the electronic control device will be described.

  FIG. 6 is a block diagram of the power supply reverse connection protection circuit according to this embodiment. In the figure, reference numeral 7 denotes a power supply reverse connection protection circuit, and 31 denotes an electronic control device formed by connecting a load 6 to the power supply reverse connection protection circuit 7.

  The power supply reverse connection protection circuit 7 shown in the figure is different from the power supply reverse connection protection circuit 7 shown in FIG. 4 as follows. That is, as shown in FIG. 7, as the load 6, for example, an H bridge circuit 22 for driving a motor is illustrated as in FIG. 5, but one end of the load 6 is connected to the power supply terminal 3. The end is connected to the output terminal 8 of the power supply reverse connection protection circuit 7. The input terminal 9 of the reverse connection protection element control circuit 11 is connected to the ground terminal 5.

  In addition, the diode rectifier 12 includes only the high potential generation diodes D1 and D2 and the high potential side node 13, and the low potential generation diode and the low potential side node are not provided. The parasitic diode PD of the reverse connection protection element 10 (N channel MOS transistor 17) and the parasitic diodes PD1 to PD4 of the H bridge circuit 22 for driving the motor are used as low potential generating diodes of the rectifier 12, The output terminal 8 of the power supply reverse connection protection circuit 7 is connected to the ground terminal of the reverse connection protection element control circuit 11 as a low potential side node of the rectifier 12.

  The operation of the power supply reverse connection protection circuit of the present embodiment configured as described above will be described below with reference to FIG.

  In a normal power supply state in which the high potential side terminal 2 of the external DC power supply is connected to the power supply terminal 3 and the low potential side terminal 4 of the external DC power supply is connected to the ground terminal 5, the power supply terminal 3 passes through the diode D1 of the rectifier 12. The high-potential side node 13 passes through the reverse connection protection element control circuit 11, the output terminal 8 of the power supply reverse connection protection circuit 7, the parasitic diode PD of the reverse connection protection element 10, and the path to the ground terminal 5. Energize.

  Simultaneously with this energization, a high potential (specifically, a potential that is lower than the potential of the power supply terminal 3 by Vf) is output to the high potential side node 13 of the rectifier 12, and is output to the output terminal 8 of the power supply reverse connection protection circuit 7. Is output at a low potential (specifically, a potential higher by Vf than the potential of the ground terminal 5). As a result, the comparator 15 and the reverse connection protection drive circuit 16 are in a normal operation state.

  Since the operations of the comparator 15 and the reverse connection protection drive circuit 16 are the same as the operations of the power supply reverse connection protection drive circuit 16 of the second embodiment, description thereof is omitted. However, in the reverse connection protection drive circuit 16, the on-control voltage for driving the reverse connection protection element 10 is sufficient as the voltage of the external DC power supply, and therefore it is not necessary to boost and generate the voltage by a booster circuit or the like.

  Next, a power reverse connection state in which the low potential side terminal 4 of the external DC power supply is connected to the power supply terminal 3 and the high potential side terminal 2 of the external DC power supply is connected to the ground terminal 5 will be described.

  In this power supply reverse connection state, the ground terminal 5 passes through the diode D2 of the rectifier 12, the high potential side node 13 passes through the reverse connection protection element control circuit 11, the power supply reverse connection protection circuit 7 passes through the output terminal 8, and the load 6 The H bridge circuit 22 is energized through the MOS diode parasitic diodes PD1 to PD4 and the path to the power supply terminal 3.

  Simultaneously with this energization, a high potential (specifically, a potential lower than the potential of the ground terminal 5 by Vf) is output to the high potential side node 13 of the rectifier 12, and is output to the output terminal 8 of the power supply reverse connection protection circuit 7. Generates a low potential (specifically, a potential higher by 2 Vf than the potential of the ground terminal 3). Thereby, the comparator 15 and the reverse connection protection element driving circuit 16 are in a normal operation state. Since the normal operation of the comparator 15 and the reverse connection protection drive circuit 16 has already been described in the second embodiment, a description thereof will be omitted. In addition, since the operation at the time of reverse connection of the power source and the application of the negative surge is the same as that of the second embodiment, the description thereof is omitted.

  As described above, according to the present embodiment, it is possible to realize a power supply reverse connection protection circuit that uses an N-channel MOS transistor 17 as the reverse connection protection element 10 and eliminates the need for a circuit such as a booster circuit and reduces the number of components. .

  In the present embodiment, the ground terminal of the reverse connection protection element control circuit 11 is used as the output terminal 8 of the power supply reverse connection protection circuit 7. However, as shown in FIG. The low potential side node 14 may be the ground terminal of the reverse connection protection element control circuit 11.

  In this embodiment, the comparator 15 recognizes reverse connection and outputs an off signal. However, the potential of the power supply terminal 3 and the potential of the ground terminal 5 do not necessarily need to be reversed. A configuration may be adopted in which an off signal is output when the potential difference between the children reaches a predetermined potential difference.

  In the present embodiment, the H bridge circuit 22 is used as the load 6. However, the H bridge circuit 22 is not necessarily used, and a motor drive device having at least one pair of MOS transistor series circuits, a power source Forward diode connection when an external DC power supply is reversely connected, such as a power supply circuit where a device, buffer circuit, MOS transistor and the cathode side of a diode are connected and an inductive load is connected to the connection point It is possible to apply any load that generates a route.

  In the present embodiment, the N-channel MOS transistor 17 is used as the reverse connection protection element 10. However, the N-channel MOS transistor 17 is not necessarily used. For example, a P-channel MOS transistor or a parasitic diode may be used. Of course, these transistor elements may be used.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above embodiment, A various change is possible and they are also included in the scope of the present invention. Needless to say.

  As described above, the power supply reverse connection protection circuit according to the present invention can protect the device from destruction due to overcurrent at the time of reverse power connection of the electronic control device that drives the load or when a negative surge is applied. Therefore, it is particularly useful as a protection circuit for a driving device having a load such as a power supply device and a motor driving device in the in-vehicle field.

1, 21, 31 Electronic controller 2 High potential side terminal 3 of external DC power supply 3 Power supply terminal 4 Low potential side terminal of external DC power supply 5 Ground terminal 6 Load 7 Power supply reverse connection protection circuit 8 Output terminal 9 of power supply reverse connection protection circuit Input terminal 10 of power supply reverse connection protection circuit Reverse connection protection element PD Parasitic diode 11 Reverse connection protection element control circuit 12 Rectifier D1-D4 Diode 13 High potential side node 14 Low potential side node 15 Comparator 16 Reverse connection protection element drive circuit 17 N channel MOS transistor 18 P channel MOS transistor 19 Warning signal 22 H bridge circuit PD1 to PD4 Parasitic diode

Claims (8)

When the high potential side terminal and low potential side terminal of the external DC power supply are connected to the power supply terminal and the ground terminal, and power is supplied from the external DC power supply to the load connected to the power supply terminal and the ground terminal. And a power supply reverse connection protection circuit for protecting against reverse connection of the external DC power supply to the power supply terminal and the ground terminal,
A reverse connection protection element connected in series with the load with respect to the external DC power supply;
A rectifier connected to the power supply terminal and the ground terminal for rectification;
A reverse connection protection element control circuit that operates with the voltage rectified by the rectifier, recognizes the connection state of the external DC power supply to the power supply terminal and the ground terminal, and controls the on / off operation of the reverse connection protection element And a power reverse connection protection circuit. In the power supply reverse connection protection circuit according to claim 1,
The rectifier is
A diode bridge rectifier having four diodes;
Two terminals connected to the power supply terminal and the ground terminal;
A high potential side node that generates a high potential after rectification and a low potential side node that generates a low potential after rectification;
The power supply reverse connection protection circuit, wherein the high potential side node and the low potential side node are connected to the reverse connection protection element control circuit. In the power supply reverse connection protection circuit according to claim 2,
The power supply reverse connection protection circuit, wherein the reverse connection protection element is composed of an IGBT or a MOS transistor. In the power supply reverse connection protection circuit according to claim 1,
The rectifier has only two diodes for generating a low potential and a low potential side node,
The reverse connection protection element has a configuration to be diode connection in the reverse direction when the DC power supply is reversely connected,
The load has a configuration that becomes a diode connection in a forward direction when the DC power supply is reversely connected,
The component part which becomes the diode connection in the reverse direction in the reverse connection protection element and the component part which becomes the diode connection in the forward direction at the load function as two diodes for generating a high potential in the rectifier. And
A connection point between the reverse connection protection element and the load is connected to the reverse connection protection element control circuit as a high potential side node of the rectifier. In the power supply reverse connection protection circuit according to claim 1,
The rectifier has only two diodes for generating a high potential and a high potential side node,
The reverse connection protection element has a configuration to be diode connection in the reverse direction when the DC power supply is reversely connected,
The load has a configuration that becomes a diode connection in a forward direction when the DC power supply is reversely connected,
The component part which becomes the diode connection in the reverse direction in the reverse connection protection element and the component part which becomes the diode connection in the forward direction at the load function as two diodes for generating a low potential in the rectifier. And
A connection point between the reverse connection protection element and the load is connected to the reverse connection protection element control circuit as a low potential side node of the rectifier. In the power supply reverse connection protection circuit according to claim 4 or 5,
The power supply reverse connection protection circuit, wherein the reverse connection protection element includes an NMOS transistor or a PMOS transistor. In the power supply reverse connection protection circuit according to any one of claims 1 to 6,
The reverse connection protection element control circuit,
A comparator that is connected to a high potential side terminal and a low potential side terminal of the external DC power supply to recognize reverse connection of the external DC power supply;
A reverse connection protection element driving circuit that controls a voltage of a control terminal of the reverse connection protection element based on an output of the comparator and performs switching between an ON operation and an OFF operation of the reverse connection protection element. Power supply reverse connection protection circuit. In the power supply reverse connection protection circuit according to any one of claims 1 to 7,
The reverse connection element control circuit further has a function of outputting a warning signal when recognizing reverse connection of the DC power supply.

Images