JPH04321773A - Power integrated circuit for automobile - Google Patents

Abstract

PURPOSE:To prevent the damage of a battery by allowing a current to flow from an earth terminal to an adjunct circuit in the case of the high side switch of an intelligent semi-conductor and allowing the current to flow out from the adjunct circuit to an electric power supply terminal in the case of a low side switch when a battery is put in reverse connection. CONSTITUTION:By providing connection of the surface of a semi-conductor base plate on which a MOS type switching element is formed to a diode formed on a semi-conductor layer through an insulating film between an adjunct circuit and an earth terminal in the case of an intelligent semi-conductor high side switch and between the adjunct circuit and an electric power supply terminal in the case of a low side switch, the reverse connection of a battery can be protected without the necessity of the outside attaching of the diode and without forming a parasitic transistor in the base plate.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a power integrated circuit for an automobile in which a power semiconductor switching element for switching dielectric loads of an automobile, a control circuit thereof, a driving circuit, etc. are constructed in and on a single semiconductor substrate. Regarding.

0002

2. Description of the Related Art Various electrical devices installed in automobiles use batteries as a power source. A semiconductor switching element is connected between the battery and the electrical device that is the load. FIG. 2 shows an example using an intelligent power semiconductor switch in which a control circuit, a drive circuit, etc. are integrated in and on the same semiconductor substrate as a semiconductor switching element. The intelligent power semiconductor high-side switch 21 is connected between the load 3 and the intelligent power semiconductor low-side switch 22 is connected to the other terminal of the load 3 whose one terminal is connected to the positive terminal of the battery 20. be.

FIG. 3 shows an intelligent power semiconductor high-side switch, which includes ancillary circuits 11 such as a drive circuit and a control circuit, and a MOS connected to the gate of a power MOSFET 1 as a switching element via a resistor Rg.
A FET 12, a Zener diode 13, etc. are provided on the same semiconductor substrate. In particular, when switching is performed by connecting an inductive load to the output terminal (OUT) connected to the source of the power MOSFET, when the OUT terminal becomes a large negative potential at turn-off, that potential is transferred to the connection point. When the potential of the zener diode 13 exceeds the zener voltage of the zener diode 13 and becomes deeply negative, the MO from the connection point 14
A current flows through SFET 12, and by applying a gate voltage to power MOSFET 1 via Rg, power MOSFET 1 itself turns on its output and absorbs the energy at turn-off. Figure 4 shows an intelligent power semiconductor low-side switch, power MOSFE
The drain terminal of T1 becomes the output terminal (OUT),
The attached circuit 15 including MOSFET 12 etc. is connected to MOSFET.
It is provided on the same semiconductor substrate as , and is connected to the gate of MOSFET 1 via a resistor Rg.

0004

[Problem to be Solved by the Invention] When the battery is accidentally reversely connected, current I1 flows from the ground terminal (GND) to the attached circuit 11 in the high-side switch of FIG. 3, and the low-side switch of FIG. As the current I2 flows out from the attached circuit 15 toward the battery,
The attached circuit 11 or 15 will be destroyed. In order to prevent this, the high side switch 2
1 has a current inflow limiting diode 4 in series with the GND terminal.
1, and the low side switch 22 has a power supply terminal (Vcc
) It is necessary to connect a current outflow limiting diode 42 in series. Conventionally, such diodes have been connected externally, but it is desirable to be able to omit such external connections. However, there are also problems when a power MOSFET and a diode are fabricated on the same substrate using self-separation technology, as shown in FIG. The right side of the diagram is the power MOSFE
At the T portion, the n− layered on the n+ silicon substrate 51
A p+ region 53 is selectively formed in the surface layer of silicon layer 52, and an n+ source region 54 is further selectively formed in the surface layer of p+ region 53. p+ region 53
The part sandwiched between the n- layer 52 and the n+ region 54 is the channel part, which is made of low-resistance n+ polycrystalline Si and is connected to the gate terminal G via a silicon oxide film 55 that becomes a gate oxide film. A source electrode 58 made of an Al-Si alloy is insulated from the gate electrode 56 by a PSG film 57, and connected to the source terminal S. A source electrode 58 made of an Al-Si alloy is in common contact with the p+ region 53 and the n+ region 54. ing. On the other hand, the n+ layer 51 has a drain electrode 5
9 are in contact. On the left side of the figure is an integrated diode separated from the power MOSFET, which has a p+ anode region 61 selectively formed in the surface layer of the n- layer 52 and an n+ cathode region 62 selectively formed in the surface layer. An anode electrode 63 connected to an anode terminal A is in contact with the anode region 61, and a cathode electrode 64 connected to a cathode terminal K is in contact with the cathode region 62.

In a semiconductor element as shown in FIG.
Since a pn transistor structure is generated, when this parasitic transistor is turned on, a large current flows, which tends to lead to destruction. Therefore, there is a drawback that it is impossible to increase the reverse withstand voltage of the diode, which would increase the current amplification factor of the parasitic transistor.

An object of the present invention is to provide a power integrated circuit in which the reverse withstand voltage of series-connected diodes can be freely selected in order to prevent damage to attached circuits when a battery is reversely connected.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the power integrated circuit for an automobile of the present invention includes a MOS type switching element and its auxiliary circuit formed in one semiconductor element, and the semiconductor element. A P region and an N region are formed adjacent to each other in a semiconductor layer provided on the surface of the body via an insulating film, and the P region is a diode connected to the auxiliary circuit and one main switching element. It includes an output terminal connected to an electrode, a power terminal connected to another main electrode, and a ground terminal connected to the N region of the diode. Then, a load whose one side is grounded is connected to the output terminal, the positive terminal of the battery is connected to the power supply terminal, and the ground terminal is grounded. Furthermore, it is also effective to connect a constant current source between the power supply terminal and the P region of the diode. Another automotive power integrated circuit of the present invention includes a MOS switching element and its auxiliary circuit formed on one semiconductor body, and a semiconductor provided on the surface of the semiconductor body with an insulating film interposed therebetween. A layer has a P region and an N region formed adjacent to each other, and the N region is connected to a diode connected to the auxiliary circuit, an output terminal connected to one main electrode of the switching element, and a P region of the diode. It shall have a power terminal connected to it and a ground terminal connected to an attached circuit. Then, a load is connected between the output terminal and the positive terminal of the battery, the positive terminal of the battery is connected to the power supply terminal, and the ground terminal is grounded.

[0008]

[Operation] A diode is installed insulated on the surface of the semiconductor body that forms the MOS switching element and its auxiliary circuit, between the auxiliary circuit and the ground terminal for high-side switches, and between the auxiliary circuit and the power supply for low-side switches. By inserting it between the terminals, when the battery is reversely connected, it prevents current from flowing into or out of the accessory circuit to the battery, thereby preventing damage to the accessory circuit. Since this diode is located outside the semiconductor body, no parasitic effects occur. In addition, when a diode is connected between the grounding terminal of the attached circuit and the grounding terminal, malfunctions caused by the grounding terminal of the attached circuit becoming negative with respect to the ground potential will occur due to the constant current flowing towards the diode. This can be prevented by providing a source.

[0009]

Embodiment FIG. 1 shows an automotive power integrated circuit according to an embodiment of the present invention, in which a diode 4 is connected to the GND terminal side of the intelligent power semiconductor high-side switch shown in FIG.
As shown in FIG. 7, in which parts common to those in FIG. 6 are denoted by the same reference numerals, this diode 4 has an n+ layer 51, an n- layer forming a power MOSFET as in FIG.
Silicon oxide film 5 on the surface of the semiconductor substrate consisting of layer 52
p+ region 71 of polycrystalline silicon layer 2 deposited on 5
and n+ region 72. That is, after depositing a p+ polycrystalline silicon layer, impurities are diffused into a part of it to form an n+ region 72, and an anode electrode 63 is connected to the p+ region 71 through a contact hole opened in the PSG film 57.
Cathode electrode 64 is brought into contact with n+ region 72. This diode is 16-2V higher than the battery voltage 12V.
It should have a reverse breakdown voltage of 0V. When such a breakdown voltage cannot be obtained with one diode, a plurality of diodes are formed on the oxide film 55 and connected in series. This makes it possible to prevent the current I1 from flowing into the attached circuit 11 from the GND terminal as shown in FIG. 3 when the battery is reversely connected.

The power IC shown in FIG. 1 has problems as shown in FIG. FIG. 8 shows a case where an inductive load 8 is connected to the OUT terminal of the IC shown in FIG. 1, and by connecting the polycrystalline silicon diode 4, the OUT terminal potential exceeds the Zener potential of the clamping Zener diode 13 at turn-off. Zener diode 1 becomes negative potential
The current I4 flowing from 3 to the MOSFET is connected to the attached circuit 11.
When the current I5 flowing through the diode 4 becomes larger than the current I3 flowing from the connection point 14, the current I5 flowing through the diode 4 becomes negative, and the current I5 flowing through the diode 4 becomes negative.
A situation occurs in which the potential of is lower than the ground potential. This may cause the drive circuit and control circuit of the attached circuit 11 to malfunction. Therefore, a restriction is imposed that current I4 must not exceed current I3 under any operating conditions.

FIG. 9 shows an embodiment in which a countermeasure against this problem is taken into consideration. A constant current source 16 is connected between the power supply terminal (Vcc) and the connection point 14, and a current I6 such that I4 < I3 + I6 is always caused to flow. Therefore, I5>0 is maintained, the connection point 14 does not become a negative potential, and malfunctions can be prevented.

FIG. 10 shows an embodiment of a power integrated circuit including an intelligent power semiconductor low-side switch, in which the polycrystalline silicon diode 4 shown in FIG. 7 is inserted on the power supply terminal side of the low-side switch. This makes it possible to prevent the current I2 from flowing from the attached circuit 15 to the Vcc terminal as shown in FIG. 4 when the battery is reversely connected.

[0013]

According to the present invention, a protective diode that blocks current flowing into the attached circuit in the case of a high-side switch and current flowing out from the attached circuit in the case of a low-side switch when a battery is reversely connected is installed in the substrate rather than in the semiconductor substrate. By forming an insulating film on the surface, there is no risk of damage caused by the driving of parasitic transistors, and there is no need to add external diodes, increasing the reliability and added value of automotive power integrated circuits including semiconductor switches. was able to improve. Even in the case of a high-side switch where connection of a protective diode may cause malfunction, malfunction can be avoided by arranging a constant current source and adding an appropriate current.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an automotive power integrated circuit including a high-side switch according to an embodiment of the present invention.

[Figure 2] Circuit diagram when battery is positively connected to intelligent power semiconductor high-side and low-side switches

[
Figure 3: Circuit diagram of intelligent power semiconductor high-side switch

[Figure 4] Circuit diagram of intelligent power semiconductor low-side switch

[Figure 5] Circuit diagram when the intelligent power semiconductor switch is equipped with a protection function against reverse battery connection.

[Figure 6] Cross-sectional view when a diode is integrated on the semiconductor substrate of a power MOSFET

FIG. 7 is a cross-sectional view of a power MOSFET semiconductor substrate with a polycrystalline silicon diode according to the present invention.

[Figure 8] Figure 1
A circuit diagram illustrating malfunctions in the integrated circuit shown in

FIG. 9 is a circuit diagram of an automotive power integrated circuit according to an embodiment of the present invention that takes measures against the malfunction shown in FIG.

[Figure 10
]Circuit diagram of an automotive power integrated circuit including a low-side switch according to another embodiment of the present invention.

[Explanation of symbols]

1 Power MOSFET 2 Polycrystalline silicon layer 3 Load 4 Diode 11 Attached circuit 15 Attached circuit 16 Constant current source 20 Battery 51 n+ silicon substrate 52 n- silicon layer 58 Source electrode 59 Drain electrode 63 Anode electrode 64 Cathode electrode 71 p+ area 72 n+ area

Claims (5)

[Claims] Claim 1: A MOS type switching element and its auxiliary circuit formed in one semiconductor body, and a P region and an N region adjacent to a semiconductor layer provided on the surface of the semiconductor body with an insulating film interposed therebetween. a diode whose P region is connected to the auxiliary circuit; an output terminal connected to one main electrode of the switching element; a power supply terminal connected to the other main electrode; A power integrated circuit for an automobile, comprising a ground terminal connected to an N region. 2. The power integrated circuit for an automobile according to claim 1, wherein the output terminal is connected to a load having one end grounded, the power supply terminal is connected to a positive terminal of a battery, and the ground terminal is grounded. 3. The automotive power integrated circuit according to claim 1, wherein a constant current source is connected between the power supply terminal and the P region of the diode. 4. A MOS type switching element and its auxiliary circuit formed in one semiconductor body, and a P region and an N region adjacent to a semiconductor layer provided on the surface of the semiconductor body with an insulating film interposed therebetween. a diode whose N region is connected to the auxiliary circuit, an output terminal connected to one main electrode of the switching element, a power supply terminal connected to the P region of the diode, and the auxiliary circuit. An automotive power integrated circuit characterized by comprising a ground terminal connected to a ground terminal. 5. The automotive power integrated circuit according to claim 4, wherein a load is connected between the output terminal and the positive terminal of the battery, the positive terminal of the battery is connected to the power supply terminal, and the ground terminal is grounded.