JP2005093763A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device which prevents lowering of the input voltage for a drive circuit due to the operation of a protective circuit and which is high in reliability, in a power semiconductor device accommodating the protective circuit. <P>SOLUTION: The driving circuit is connected to the IN terminal of the semiconductor device 1, a "high" signal is applied on the IN terminal of the semiconductor device 1, and the signal is transmitted to a power switching element 2, while passing through an n-type diffusion resistor 11 connected to an aluminum wiring 8 via a contact 9. An MOS structure is formed of polysilicon 10 and the n-type diffusion resistor 11, as a variable resistor 5 between the IN terminal and the power switch element 2 for the semiconductor device 1. At normal operation times, a gate intercepting MOS 4, connected between the gate of power switch element 2 and a grounding potential, is set to OFF state, whereby the MOS structure goes to ON state. At detection of abnormalities, the gate intercepting MOS 4 is set to ON state, and the MOS structure goes to OFF state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power switch element that drives a load such as a lamp, an LED, and an inductor.

  Conventionally, as a method for driving a load such as a lamp or a coil, a method of driving a load by providing a semiconductor device on the low potential side of the load and turning on or off the semiconductor device is generally used. This semiconductor device generally has various protection functions.

  A circuit diagram of a conventional semiconductor device is shown in FIG.

  A semiconductor device 1 serving as a switch is connected to a low potential side of a load 6 such as a lamp or a coil connected to a power source 7.

  The semiconductor device 1 includes an abnormality detection circuit 3. When an overcurrent flows through the load 6, the semiconductor device 1 detects a change in the potential of the drain terminal (D terminal) of the power switch element 2 according to the current and detects a gate cutoff MOS 4. Send an ON signal to the gate. As a result, the gate cut-off MOS 4 is turned on, and the potential of the gate of the power switch element 2 connected to the drain terminal and the drain terminal is close to 0 V. Therefore, the power switch element 2 is turned off and is protected from destruction due to overcurrent. (See, for example, Patent Document 1).

  In addition, even if the current continues to flow for a long time or overcurrent protection is applied to the extent that the overcurrent protection does not act on the load 6, the abnormality detection circuit is also activated when the state continues for a long time and the temperature of the semiconductor device rises excessively. 3 works to send an ON signal to the gate of the gate cut-off MOS 4 and the drain terminal of the gate cut-off MOS becomes close to 0V to turn off the power switch element 2 to protect it from destruction.

  Next, FIG. 4 shows a cross-sectional structure diagram of the conventional semiconductor device.

  A drive circuit such as a microcomputer is connected to the IN terminal of the semiconductor device 1 to control the semiconductor device 1 and when various protections are activated, an ON signal is sent to the gate of the gate cutoff MOS 4 and the drain terminal of the gate cutoff MOS 4 Is close to 0 V, so that a current flows from a control element such as a microcomputer into the resistor 12 connected between the IN terminal of the semiconductor device 1 and the gate G of the power switch element 2.

  The resistor 12 is generally a polysilicon resistor, but is set to a low resistance in order to increase the switching speed of the power switch element 2. In this case, when various protections are applied against current abnormality, temperature abnormality, etc., the input current of the semiconductor device 1 is large, so that a control element such as a microcomputer cannot maintain the input voltage.

In recent years, the current capability in a drive circuit such as a microcomputer has been lowered particularly in order to save energy of a power supply device. In such a case, the protection function of the circuit is activated by an abnormal current or the like, and the power switch element is turned off. Will not work. In the abnormality detection circuit block 3, a lateral MOS, a resistor, a diode, a Zener diode, etc. are formed in or on the P-type diffusion layer to constitute a circuit. Since the power switch element 2 is turned on even at a low voltage, the abnormality detection circuit 3 does not function even though an abnormal current flows, and the power switch element 2 is destroyed.
Japanese Patent Laid-Open No. 2002-1000097 (FIG. 4)

  When the above conventional technique is used, in order to reduce the current flowing from the input terminal and reliably continue the operation of the abnormality detection circuit 3 with the voltage of the control element such as a microcomputer, the power from the input terminal of the semiconductor device 1 is used. There is a method of increasing the resistance value connected between the gates of the switch elements. In this case, the delay of the switching speed of the power switch element 2 becomes large, and the switching operation of the load on / off can be accurately controlled without delay. I can't. If the resistance value connected between the IN terminal of the semiconductor device 1 and the gate of the power switch element 2 is reduced, if the abnormal state is prolonged as described in the prior art, the input voltage of the drive circuit is lowered and the abnormality detection circuit 3 is activated. The power switch element 2 is turned on, leading to destruction.

  In order to solve the above-described problems, a semiconductor device of the present invention is a semiconductor device including a power element and a control circuit for the power element, and the control circuit detects an abnormality in current or temperature flowing through the power element. A circuit, a switch element that cuts off an input to the power element in accordance with an output signal from the abnormality detection circuit, and a resistance value that is connected to an input terminal of the power element and in accordance with an output signal from the abnormality detection circuit And a variable resistor that changes.

  In the semiconductor device, when the switch element is turned on by an output signal from the abnormality detection circuit, the variable resistor has a high resistance value, and the switch element is turned on by an output signal from the abnormality detection circuit. When in the off state, the variable resistor has a low resistance value.

  Further, the variable resistor comprises a parallel resistance of a MOS structure and a high resistor, and when the switch element is in an off state, the MOS structure is in an on state and has a low resistance value, and the switch element is on. When it is in a state, the MOS structure is turned off and has a high resistance.

  It is preferable to use a diffusion resistance of a semiconductor substrate on which the MOS structure is formed as the high resistance body.

  The power element is preferably composed of an N-type MOSFET, but may be composed of an IGBT or a bipolar transistor.

  In the semiconductor device of the present invention, it is preferable that the power element is connected to a power source through a load, and a drive circuit for driving the power element is connected to an input terminal of the power element.

  According to the present invention, a drive circuit such as a microcomputer connected to the IN terminal can be used even if the current capability is low, and loads such as lamps, LEDs, and inductors are driven without reducing the switching speed of the power switch element 2. When an overcurrent or a short-circuit current flows or the power switch element 2 generates heat due to the current, the input of the power switch element 2 is set to a low potential and the power switch element 2 is turned off to be destroyed. Protect from and improve reliability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of a semiconductor device according to an embodiment of the present invention, and differs from FIG. 3 in that the resistor connected between the IN terminal and the gate of the power switch element 2 is a variable resistor 5. The rest of the configuration is the same.

  A schematic diagram of the structure of the variable resistor is shown in FIG. (A) is a top view, (b) is sectional drawing of the A-A 'direction shown to Fig.2 (a).

  As shown in FIG. 2A, a drive circuit (not shown) such as a microcomputer is connected to the IN terminal of the semiconductor device 1 (not shown) to control the semiconductor device 1 and is high during normal operation. A signal (for example, 5 V) is applied to the IN terminal of the semiconductor device 1, and the signal is transmitted to the gate of the power switch element 2 through the N-type diffusion resistor 11 connected to the aluminum wiring 8 through the contact 9.

  Further, as shown in FIG. 2B, a MOS structure is formed by the polysilicon 10 and the N-type diffused resistor 11, and a voltage is applied to the polysilicon 10 formed on the gate oxide film (not shown). When added, a passage (hereinafter referred to as a channel) through which the carrier flows is formed immediately below, and a signal from the IN terminal flows as shown by an arrow.

  The operation of the semiconductor device 1 will be described in detail below. First, during normal operation, since a voltage signal of 0 V is sent from the abnormality detection circuit 3 to the gate of the gate cutoff MOS 4, the gate cutoff MOS 4 is in an off state and its drain potential is kept at a high potential. Since this drain is connected to the gate of the power switch element 2, the power switch element 2 is turned on. In this case, a signal equal to or higher than the threshold voltage of the MOS structure is applied from the abnormality detection circuit 3 to the polysilicon 10 through the aluminum wiring 8 and the contact 9. The polysilicon 10 overlaps with the N-type diffused resistor 11.

  In this case, since the MOS structure is turned on and a channel is formed immediately below the polysilicon 10, the resistance between the IN terminal of the semiconductor device 1 and the power switch element 2 is kept low.

  On the other hand, when the protection circuit operates due to an overcurrent flowing through the load or the like, an ON signal is input from the abnormality detection circuit 3 to the gate of the gate cutoff MOS4, the power cutoff MOS4 becomes conductive, and the drain potential is the source potential, That is, since the potential is substantially the same as the ground potential, the drain terminal of the gate cutoff MOS 4 is close to 0V. At the same time as the ON signal is sent to the gate of the gate cutoff MOS 4, a voltage signal of 0V is sent from the abnormality detection circuit 3 to the polysilicon 10 through the aluminum wiring 8 and the contact 9. As a result, the channel formed immediately below the polysilicon 10 is closed, and the signal from the IN terminal passes through the N-type diffused resistor 11 and passes through the contact 9 to the power switch element 2 connected by the aluminum wiring 8. A signal is sent to the gate. In this case, the resistance value of the N-type diffusion resistor 11 is a product of the sheet resistance and the distance between the U-shaped portions, and becomes a sufficiently high resistance value as compared with the channel resistance of the MOS structure. For this reason, the current flowing through the resistor becomes sufficiently small and the input voltage of the drive circuit hardly decreases, so that the abnormality detection circuit 3 continues to operate and the power switch element 2 is kept in the OFF state and is not destroyed.

  As described above, according to the present embodiment, the MOS structure variable resistor is arranged between the gate of the power switch element and the input terminal to which the drive circuit is connected, so that the MOS structure can be obtained during normal operation. When conducting, the low resistance is maintained, and during abnormal operation, the MOS structure is cut off and the high resistance is maintained. Therefore, it is possible to accurately control the on / off switching operation of the load without delay without reducing the switching speed, and at the same time, it is possible to reliably protect the circuit in the event of an abnormality.

  In the present embodiment, polysilicon is used as the gate electrode material of the MOS structure forming the variable resistor, but other metal materials such as aluminum wiring may be used. Moreover, although the NMOS structure is shown as the variable resistor, a structure in which a PMOS is formed on an N-type substrate may be used.

  In the present embodiment, an example in which the power switch element 2 is configured by an N-type MOSFET has been described. However, the power switch element 2 may be configured by an IGBT or a bipolar transistor.

  The semiconductor device according to the present invention is useful as a power semiconductor device having a circuit protection function, particularly a semiconductor device using a control element driven at a low voltage.

Circuit diagram of a semiconductor device in an embodiment of the present invention It is a structure schematic diagram of the variable resistor in embodiment of this invention, (a) is a top view, (b) is sectional drawing of the A-A 'direction shown to Fig.2 (a). Circuit diagram of conventional semiconductor device Cross-sectional structure diagram of conventional semiconductor device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Power switch element 3 Abnormality detection circuit 4 Gate interruption | blocking MOS
5 Variable Resistor 6 Load 7 Power Supply 8 Aluminum Wiring 9 Contact 10 Polysilicon 11 N-type Diffusion Resistance 12 Resistance

Claims (8)

A semiconductor device comprising a power element and its control circuit,
The control circuit includes:
An abnormality detection circuit for detecting an abnormality in current or temperature flowing in the power element;
A switch element that cuts off the input to the power element in response to an output signal from the abnormality detection circuit and an input terminal of the power element, and a resistance value changes in accordance with an output signal from the abnormality detection circuit. A semiconductor device comprising a variable resistor. When the switch element is turned on by an output signal from the abnormality detection circuit, the variable resistor has a high resistance value,
2. The semiconductor device according to claim 1, wherein the variable resistor has a low resistance value when the switch element is in an OFF state by an output signal from the abnormality detection circuit. The variable resistor comprises a parallel resistance of a MOS structure and a high resistor, and when the switch element is in an off state, the MOS structure is in an on state and has a low resistance value.
3. The semiconductor device according to claim 2, wherein when the switch element is in an on state, the MOS structure is in an off state and has a high resistance. 4. The semiconductor device according to claim 3, wherein a diffusion resistance of a semiconductor substrate on which the MOS structure is formed is used as the high resistance body. The semiconductor device according to claim 1, wherein the power element is formed of an N-type MOSFET. The semiconductor device according to claim 1, wherein the power element is formed of an IGBT. 5. The semiconductor device according to claim 1, wherein the power element is a bipolar transistor. 8. The power element is connected to a power source via a load, and a drive circuit for driving the power element is connected to an input terminal of the power element. Semiconductor device.

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