An electronic device having a reverse polarity protection circuit.

Abstract

To provide an electronic device having a reverse polarity protection circuit capable of preventing damage of a circuit element in advance.SOLUTION: An electronic device having a reverse polarity protection circuit includes: an ideal diode circuit I that has a driver transistor Q1 connected in the middle of a first power supply line 1 from an input terminal IN to an output terminal OUT, and supplies a current from a power source to a load when the driver transistor Q1 is turned on when an input voltage Vin is compared with an output voltage Vout and the input voltage Vin>the output voltage Vout; a second power supply line 2 connected to a ground terminal GND; a third power supply line 3 in which a diode D is connected between the first power supply line 1 and the substrate sub; a first switching element SW1 connected between the second power supply line 2 and the third power supply line 3; and a polarity determination unit for performing control to conduct between the second power supply line 2 and the third power supply line 3 by the first switching element SW1 when an input terminal IN has a positive polarity and to cut off between the second power supply line 2 and the third power supply line 3 by the first switching element SW1 when the input terminal IN becomes a negative polarity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic device having a reverse polarity protection circuit, and is particularly useful for applying reverse polarity protection to an ideal diode circuit. [Background technology]

[0002] Figure 6 is a circuit diagram showing an example of an ideal diode circuit (IC). Here, an ideal diode circuit is a diode that can operate at a forward voltage of 0V. With a normal diode, current does not flow unless the forward voltage reaches about 0.6V. As a result, power is consumed as the product of the forward voltage and the load current. An ideal diode circuit uses an operational amplifier and transistor to create an ideal diode that minimizes this power loss and prevents reverse current.

[0003] 6, the ideal diode circuit 0I includes a driver transistor Q01 connected midway along a power supply line 01 extending from an input terminal IN to an output terminal OUT, and is configured to compare an input voltage Vin at the input terminal IN with an output voltage (Vout) at the output terminal OUT, and when the input voltage (Vin) is greater than the output voltage (Vout), the driver transistor Q01 turns on, supplying current from a power supply (not shown) connected to the input terminal IN to a load (not shown) connected to the output terminal OUT. A diode D02, acting as an ESD protection element and parasitic diode, is connected between a node P01 between the power supply line 01 and the driver transistor Q01, which is closer to the input terminal IN than the driver transistor Q01, and the ground terminal GND.

[0004] In this ideal diode circuit 01, if the input terminal IN has reverse polarity due to a mistake such as incorrect power supply polarity, a large current will flow from the ground terminal GND to the input terminal IN via the diode D02, resulting in problems such as damage to circuit elements.

[0005] On the other hand, to avoid the problem of circuit element destruction due to the current caused by the application of reverse voltage, a configuration has been proposed in which an external diode D02, with its cathode connected to the ground terminal GND, is connected between the ground terminal GND of the ideal diode circuit 0I and ground, as shown in Figure 7. However, in this case, a voltage drop occurs due to the forward resistance of diode D02 when a positive voltage is applied. This results in a new problem: the minimum operating voltage increases.

[0006] Patent Document 1 is known as a conventional technique that discloses a reverse connection protection circuit that protects circuit elements when a reverse connection potential is applied to a power supply line. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-143024 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-described conventional technology, an object of the present invention is to provide an electronic device having a reverse polarity protection circuit that can block the flow of harmful current into the device and prevent damage to circuit elements when the input terminal has a reverse polarity opposite to normal. [Means for solving the problem]

[0009] The first aspect of the present invention that achieves the above object is: an ideal diode circuit including a driver transistor connected midway through a first power supply line extending from an input terminal to an output terminal, which compares an input voltage, which is the voltage of the input terminal, with an output voltage, which is the voltage of the output terminal, and when the input voltage is greater than the output voltage, the driver transistor is turned on to supply a current from a power supply connected to the input terminal to a load connected to the output terminal; a second power line connected to the ground terminal; a third power supply line having a diode connected midway, the diode having a cathode connected to the first power supply line and an anode connected to a substrate, connecting the first power supply line and the substrate; a first switching element connected between the second power supply line and the third power supply line; a polarity determination unit that controls the first switching element to connect the second power supply line and the third power supply line when the input terminal has a positive polarity, and to cut off the second power supply line and the third power supply line when the input terminal has a negative polarity; The present invention is characterized by having the following.

[0010] A second aspect of the present invention is In the electronic device having the reverse polarity protection circuit according to the first aspect, The polarity determination unit a first resistor and a first constant voltage clamp element connected in series between the input terminal and a ground terminal; a second constant voltage clamp element and a second resistor connected in series between the third power supply line and the second power supply line on the anode side of the diode; a control line having one end connected between the first resistor and the first constant voltage clamp element and the other end connected to the first switching element via a resistive element therebetween, for switching the first switching element to an off state when the potential of a node formed by the connection changes from a predetermined positive potential to the potential of the ground terminal; a second switching element connected between the third power supply line and the second power supply line, which is turned on when the potential of a node between the second constant voltage clamp element and the second resistor changes from a predetermined positive potential to a negative potential, thereby conducting electricity between the third power supply line and the control line; The present invention is characterized by having the following.

[0011] A third aspect of the present invention is In an electronic device having a reverse polarity protection circuit according to the first or second aspect, a driver transistor cutoff circuit for forcibly turning off the driver transistor when the input terminal has reversed polarity; The interruption circuit includes: a third switching element connected between the first power supply line and the base of the driver transistor; The input terminal has a third constant voltage clamp element and a third resistor connected in series, the cathode side of the third constant voltage clamp element is connected to the first power supply line, and the third resistor is connected to the ground terminal, and when the input terminal becomes negative potential, the potential between the third constant voltage clamp element and the third resistor becomes negative potential, causing the third switching element to switch to an ON state and turning the driver transistor to an OFF state.

[0012] A fourth aspect of the present invention is No. In two aspects In an electronic device having the reverse polarity protection circuit described, The resistive element is characterized in that it is formed of back-to-back connected PMOS transistors, each gate of which is connected to the second power supply line.

[0013] A fifth aspect of the present invention is No. In two aspects In an electronic device having the reverse polarity protection circuit described, The resistive element is characterized in that it is formed of a resistor interposed midway along the control line.

[0014] A sixth aspect of the present invention is a method for manufacturing a semiconductor device comprising: No. In three aspects In an electronic device having the reverse polarity protection circuit described, The first, second and third constant voltage clamp elements are characterized by being formed of diodes or MOS transistors.

[0015] A seventh aspect of the present invention is No. In three aspects In an electronic device having the reverse polarity protection circuit described, The first, second and third constant voltage clamp elements are characterized in that they are formed of Zener diodes. [Effects of the Invention]

[0016] According to the present invention, when the input terminal has reverse polarity, the second power line connected to the ground terminal and the third power line are disconnected by turning off the first switching element, thereby preventing harmful current from flowing into the circuit from the ground terminal via the parasitic diode. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a circuit diagram showing an entire electronic device having a reverse polarity protection circuit according to an embodiment of the present invention; [Figure 2] FIG. 4 is a circuit diagram showing a normal state of a polarity determination unit of the electronic device according to the embodiment. [Figure 3] FIG. 10 is a circuit diagram showing a state of the polarity determination unit of the electronic device in the embodiment when polarity is reversed. [Figure 4] FIG. 2 is a circuit diagram illustrating an interruption circuit of the electronic device according to the embodiment. [Figure 5] FIG. 10 is a circuit diagram showing the entirety of an electronic device having a reverse polarity protection circuit according to another embodiment of the present invention. [Figure 6] FIG. 1 is a circuit diagram showing an example of an ideal diode circuit according to the prior art. [Figure 7] FIG. 1 is a circuit diagram showing another example of an ideal diode circuit according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] 1 is a circuit diagram showing the entire electronic device including a reverse polarity protection circuit according to an embodiment of the present invention. As shown in the figure, an ideal diode circuit I includes a driver transistor Q1 connected midway along a first power supply line 1 extending from an input terminal IN to an output terminal OUT. A comparator Comp compares an input voltage Vin at the input terminal IN with an output voltage Vout at the output terminal OUT. When the input voltage Vin is greater than the output voltage Vout, the driver transistor Q1 is turned on to supply current from the power supply connected to the input terminal IN to a load connected to the output terminal OUT.

[0020] The second power supply line 2 is connected to the ground terminal GND. The third power supply line 3 is connected between the first power supply line 1 and the board sub, and a diode D2 is connected midway between the first power supply line 1 and the board sub. The diode D2 is a parasitic diode that functions as an ESD (Electro-Static Discharge) protection element for the electronic device.

[0021] The first switching element SW1 is an nMOS transistor connected between the second power supply line 2 and the third power supply line 3, and when on, connects the second power supply line 2 and the third power supply line 3, and when off, disconnects the second power supply line 2 and the third power supply line 3.

[0022] The polarity determination unit II turns on the first switching element SW1 when the input terminal IN has a positive polarity (normal), and turns off the first switching element SW1 when the input terminal IN has a reverse polarity (abnormal).

[0023] More specifically, the polarity determination unit II in this embodiment has a first resistor R1 and a first Zener diode ZD1, which is a first constant voltage clamp element, connected in series between the input terminal IN and the ground terminal GND. Also, a second Zener diode ZD2, which is a second constant voltage clamp element, and a second resistor R2 are connected in series between the third power supply line 3 and the second power supply line 2 on the anode side of the diode D2.

[0024] A control line CL is connected to the gate of the first switching element SW1 via a resistor element Q in between, and connected to a node P1, which is the connection point between the first resistor R1 and the first Zener diode ZD1. In this embodiment, the resistor element Q is formed of back-to-back connected pMOS transistors, each gate of which is connected to the second power supply line 2. This resistor element Q can also be formed of a normal resistor, but in this embodiment, the current consumption in the resistor element Q can be suppressed.

[0025] The second switching means SW2 formed by an nMOS transistor is connected between the third power supply line 3 and the control line CL, and is turned on or off depending on the potential of a node P2, which is the connection point between the second Zener diode ZD2 and the second resistor R2, to connect or disconnect the third power supply line 3 and the control line CL.

[0026] The operation of this embodiment will be described with reference to FIG. 2, a circuit diagram showing the normal state of the polarity determination unit II, and FIG. 3, a circuit diagram showing the reverse polarity state. As shown in FIG. 2, when the input terminal IN is positive (the voltage at this time is assumed to be 10 V; the same applies below), the potential of the ground terminal GND is 0 V, and the potential of the node P1, determined by the characteristics of the first Zener diode ZD1, is 5 V. As a result, the pMOS transistor of the resistance element Q is turned on, and the gate potential of the nMOS transistor serving as the first switching element SW1 is set to 5 V, so that the first switching element SW1 is turned on, and the potential of the substrate sub becomes 0 V. Furthermore, since the potential of the node P2 is 0 V, the second switching element SW2 is turned off.

[0027] In this state, the diode D2 functions as an ESD protection element via the first switching element SW1.

[0028] On the other hand, as shown in Figure 3, when the input terminal IN has reverse polarity (the voltage at this time is -10V, the same applies below), the potential of the substrate sub drops to near the potential of the input terminal IN (for example, about -9.4V) due to diode D2. At the same time, the potential of the ground terminal GND is 0V, and the potential of node P1, which is determined by the characteristics of the first Zener diode ZD1, is 0V. As a result, the pMOS transistor of resistor Q is turned off.

[0029] Meanwhile, the potential of node P2 becomes -5V due to the characteristics of Zener diode ZD2, so the nMOS transistor serving as second switching element SW2 turns on. As a result, the gate of nMOS transistor SW1 serving as first switching element becomes -10V, and first switching element SW1 cuts off the connection between second power line 2 and third power line. As a result, it is possible to prevent reverse current from flowing in via ground terminal GND.

[0030] By providing the polarity determination unit II as described above, it is possible to basically eliminate the inconvenience that occurs when the polarity of the input terminal IN is reversed, but this is not sufficient. This is because the operating state of the ideal diode circuit I is unknown when the polarity of the input terminal IN is reversed. It is desirable to ensure that the ideal diode circuit I is stopped when the polarity of the input terminal IN is reversed. This is because it ensures that the driver transistor Q1 is turned off, and the cut-off state between the input terminal IN side and the output terminal OUT side by the driver transistor Q1 is guaranteed.

[0031] Therefore, this embodiment provides a shutoff circuit III that forcibly turns off the driver transistor Q1 when the input terminal IN has reverse polarity. As shown in detail in Figures 1 and 4, the shutoff circuit III includes a third switching element SW3 connected between the first power supply line 1 and the gate of the driver transistor Q1, and a third Zener diode ZD3 and a third resistor R3 connected in series as a third constant-voltage clamp element. The anode of the third Zener diode ZD3 is connected to the first power supply line 1, and the third resistor R3 is connected to the ground terminal GND. When the input terminal IN has a negative potential, the potential at a node P3 between the third Zener diode ZD3 and the third resistor R3 becomes negative, switching the third switching element SW3 to the ON state and reliably turning off the driver transistor Q1.

[0032] As described above, the polarity determination unit II only needs to turn on the first switching element SW1 when the input terminal IN has positive polarity (normal), and turn off the first switching element SW1 when the input terminal IN has reverse polarity (abnormal). Therefore, as shown in FIG. 5, the polarity determination unit IIA is basically formed by a comparator CompIIA, which compares the potential of the input terminal IN with the potential of the ground terminal GND, and switches the first switching element to the off state via the control line CL when the voltage Vin of the input terminal IN becomes less than 0. This is because the second power supply line 2 and the third power supply line 3 are thereby disconnected.

[0033] Although the configuration of the present invention has been described above in conjunction with the embodiments, the technical concept of the present invention is not limited to these. For example, the first to third constant voltage clamp elements can also be formed of diodes or MOS transistors. [Explanation of symbols]

[0034] I Ideal diode circuit II Polarity judgment section III. Breaking circuit 1 First power line 2 Second power line 3 Third power line IN input terminal OUT output terminal GND Ground terminal sub board CL control line

Claims

1. an ideal diode circuit including a driver transistor connected midway through a first power supply line extending from an input terminal to an output terminal, which compares an input voltage, which is the voltage of the input terminal, with an output voltage, which is the voltage of the output terminal, and when the input voltage is greater than the output voltage, the driver transistor is turned on to supply a current from a power supply connected to the input terminal to a load connected to the output terminal; a second power supply line connected to the ground terminal; a third power supply line having a diode connected midway, the diode having a cathode connected to the first power supply line and an anode connected to a substrate, connecting the first power supply line and the substrate; a first switching element connected between the second power supply line and the third power supply line; a polarity determination unit that controls the first switching element to connect the second power supply line and the third power supply line when the input terminal has a positive polarity, and to disconnect the second power supply line and the third power supply line when the input terminal has a negative polarity; 1. An electronic device having a reverse polarity protection circuit, comprising:

2. 2. An electronic device having a polarity protection circuit according to claim 1, The polarity determination unit a first resistor and a first constant voltage clamp element connected in series between the input terminal and a ground terminal; a second constant voltage clamp element and a second resistor connected in series between the third power supply line and the second power supply line on the anode side of the diode; a control line having one end connected between the first resistor and the first constant voltage clamp element and the other end connected to the first switching element via a resistive element therebetween, for switching the first switching element to an OFF state when the potential of a node formed by the connection changes from a predetermined positive potential to the potential of the ground terminal; a second switching element connected between the third power supply line and the second power supply line, which is turned on when a potential at a node between the second constant voltage clamp element and the second resistor changes from a predetermined positive potential to a negative potential, thereby conducting electricity between the third power supply line and the control line; 1. An electronic device having a reverse polarity protection circuit, comprising:

3. 3. An electronic device having a reverse polarity protection circuit according to claim 1, a driver transistor cutoff circuit for forcibly turning off the driver transistor when the input terminal has reversed polarity; The interruption circuit includes: a third switching element connected between the first power supply line and the base of the driver transistor; an anode side of the third constant voltage clamp element and a third resistor connected in series, the anode side of the third constant voltage clamp element being connected to the first power supply line and the third resistor being connected to the ground terminal, and when the input terminal becomes negative potential, the potential between the third constant voltage clamp element and the third resistor becomes negative potential, causing a third switching element to switch to an ON state and turning the driver transistor to an OFF state.

4. 3. An electronic device having a reverse polarity protection circuit according to claim 2, The electronic device having a reverse polarity protection circuit is characterized in that the resistive element is formed of back-to-back connected PMOS transistors, each gate of which is connected to the second power supply line.

5. 3. An electronic device having a reverse polarity protection circuit according to claim 2, 10. An electronic device having a reverse polarity protection circuit, wherein the resistive element is formed by a resistor interposed midway along the control line.

6. 4. An electronic device having a reverse polarity protection circuit according to claim 3, 1. An electronic device having a reverse polarity protection circuit, wherein the first, second and third constant voltage clamp elements are formed of diodes or MOS transistors.

7. 4. An electronic device having a reverse polarity protection circuit according to claim 3, 1. An electronic device having a reverse polarity protection circuit, wherein the first, second and third constant voltage clamp elements are formed of Zener diodes.

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