JP3475546B2 - MOSFET drive circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a high breakdown voltage, the driving circuit of the MOSFET is et used to control the high current.

[0002]

2. Description of the Related Art Recently, high breakdown voltage, there is provided a semiconductor device capable of controlling a large current, typically that have called power element semiconductor device of this kind. A drive circuit using a MOSFET as a power element has a structure as shown in FIG. 4 (Japanese Patent Application No. 6-143664, Japanese Patent Application No. 6-143664).
Japanese Patent Application No. 6-267251) . The circuit shown in FIG.
MOS inserted between drain and source between load and load Z
A driving circuit 1 for driving the FET Q _1, MOSF
The ET Q ₁ is driven according to the control signal from the control signal source 2.

That is, in this drive circuit 1, the MOSF
It has a parallel circuit of a Zener diode ZD ₁ connected between the source and gate of ET Q ₁ and a resistor R ₁ for voltage division, and one end of the resistor R ₁ is connected to the gate of the MOSFET Q _1. The resistor R ₂ for pressure is connected in series. A series circuit of both resistors R ₁ and R ₂ is connected in parallel between the emitter and collector of a pnp type transistor Q ₂ . Here, the emitter of the transistor Q ₂ is connected to the gate of the MOSFET Q ₁ via the resistor R ₂ . The emitter and base of the transistor Q ₂ is connected to the control signal source 2 through respective resistors R _3, R _4. The collector of the transistor Q ₂ is MOSFET Q
₁ is connected to the ground side of the control signal source 2.

Assuming that a rectangular wave having two levels of H level (positive potential) and L level (0 V) is inputted as a control signal from the control signal source 2, the drive circuit 1 is as follows. Operate. First, the control signal is H
When the level, the transistor Q ₂ from a difference between the base potential and the emitter potential of the transistor Q ₂ does not occur
Is kept off. As a result, the control signal is the resistance R ₁ ,
Is divided by R ₂ minute is applied to the gate of MOSFET Q _1, MOSFET Q ₁ is turned on. On the other hand, when the control signal is at the L level, the voltage according to the control signal is not applied to the gate of the MOSFET Q ₁ ,
The MOSFET Q ₁ will be controlled in the off direction. Further, at this time, a voltage is applied between the emitter and collector of the transistor Q ₂ by the residual charge due to the capacitance between the gate and the source, so that the transistor Q ₂ is turned on, and the residual charge is discharged through the transistor Q ₂ and M
OSFET Q ₁ is rapidly turned off. The Zener diode ZD ₁ has a function of clamping the gate-source voltage of the MOSFET Q ₁ .

[0005]

By the way, in the drive circuit 1 described above, a short circuit may occur between the drain and the gate when the MOSFET Q ₁ is destroyed. In this case, M
The high voltage on the drain side of the OSFET Q ₁ is applied to the gate side, causing abrupt voltage fluctuations or excessive current flow in the drive circuit 1 and the control signal source 2, which causes the drive circuit 1 and the control circuit to control. The signal source 2 may be destroyed.

The present invention has been made in view of the above circumstances, and an object thereof is to drive a MOSFET having a function of protecting the drive circuit and the control signal source from being destroyed when the MOSFET is destroyed. To provide a circuit.

[0007]

According to a first aspect of the present invention, a MOSFET is inserted between a power source and a load, and the MOSFET is inserted between a gate of a MOSFET and a control signal source for generating a control signal. a driving circuit for controlling the MOSFET, M
When the drain and gate of the OSFET are short-circuited, the MOSFE
When a current flows from the gate of T toward the control signal source, the capacitor is charged through the diode, the first switching element that is turned on when the voltage across the capacitor becomes equal to or higher than a predetermined voltage, and one of the control signal source It is characterized by including a current limiting resistor in which a series circuit of the first switching element is inserted between the source and the gate of the MOSFET commonly connected to one end of the power supply together with the output terminal.

According to a second aspect of the present invention, the MOSF is inserted between the gate of the MOSFET inserted between the power supply and the load and the control signal source for generating the control signal, and the MOSF is supplied in response to the control signal.
A driving circuit for controlling the ET, MOSFET of drain
A capacitor that is charged via a diode when a current flows from the gate of the MOSFET toward the control signal source when the IN and the gate are short-circuited, and a first switching element that is turned on when the voltage across the capacitor exceeds a predetermined voltage. And a second switching element connected between the output terminals of the control signal source so that the first switching element is turned on when the first switching element is turned on, and the first switching element is connected to the gate through a current limiting resistor. Is characterized by.

According to a third aspect of the invention, the MOSFET is inserted between the gate of the MOSFET inserted between the power supply and the load and the control signal source for generating the control signal, and the MOSF is supplied in response to the control signal.
A driving circuit for controlling the ET, MOSFET of drain
A capacitor that is charged via a diode when a current flows from the gate of the MOSFET toward the control signal source when the IN and the gate are short-circuited, and a first switching element that is turned on when the voltage across the capacitor exceeds a predetermined voltage. A second switching element connected between the output terminals of the control signal source so that the first switching element is turned on when the first switching element is turned on, and the first switching element is connected to the gate via a current limiting resistor; Source and MOSFET game
Characterized in that it comprises a third switching element inserted between the bets turned off during on of the second switching element.

According to a fourth aspect of the present invention, a pair of voltage dividing resistors in which series circuits connected in series with each other are connected between the output terminals of the control signal source are provided, and one of the voltage dividing resistors is a MOSFET .
It is connected between the gate and the source , the other voltage dividing resistor is inserted between the control signal source and the gate of the MOSFET , and the series circuit of the diode and the capacitor is connected in parallel to the other voltage dividing resistor. The first switching element is a pnp type transistor, an emitter is connected to a connection point between the cathode of the diode and one end of the capacitor, a base is connected to the other end of the capacitor, and a collector is connected to one end of the current limiting resistor. Is characterized by being connected.

[0011]

According to the structure of the invention of claim 1, MOSFET
When the drain and the gate are short-circuited due to the destruction of the current and the current from the power source tries to flow from the gate toward the control signal source, the first switching element is turned on by charging the capacitor through the diode. As a result, M is passed through the first switching element and the current limiting resistor.
The gate and source of the OSFET are connected, and the MOS
The current that is about to flow from the gate of the FET to the control signal source is bypassed, and it is possible to prevent the control signal source from being destroyed by the overcurrent flowing into the control signal source. Further, the gate potential tends to fluctuate immediately after the MOSFET is destroyed, but since it is absorbed to some extent by the capacitor, the destruction of the control signal source due to this kind of variation can be prevented. Moreover, the MOSFET game
Since the gate and the source are connected via a current limiting resistor, it is possible to prevent the first switching element from being destroyed by an overcurrent.

According to the second aspect of the present invention, when the first switching element is turned on, the second switching element is turned on, so that the output terminals of the control signal source are short-circuited and the gate of the MOSFET is removed. Both the current to the control signal source and the control signal output from the control signal source are bypassed through the second switching element, and as a result, the MOSFET side and the control signal source side do not affect each other. In other words, it is possible to prevent destruction of the control signal source according to inflow of the overcurrent from the gate of the MOSFET to the control signal source and MO of the control signal in this state
The flow into the SFET will also stop. Moreover,
Like the invention of claim 1, gate immediately after breakdown of the MOSFET
Potential of over preparative attempts vary abruptly but, since to some extent absorbed by the capacitor, breakdown of the control signal source due to the variation of this type can also be prevented.

According to the configuration of the invention of claim 3, the third switching element which is turned off when the second switching element is turned on is inserted between the control signal source and the gate of the MOSFET. In addition to the effect of the second aspect of the invention, the control signal source and the MOSFET can be completely separated by the third switching element at the time of abnormality, and the control signal source can be reliably protected.

The structure of the invention of claim 4 is a preferred embodiment of the invention of claims 1 to 3.

[0015]

EXAMPLE 1 In this example, as shown in FIG. 1, in addition to the conventional configuration shown in FIG. 4, a protection function against an overcurrent generated when the MOSFET Q1 is short-circuited is added. That is, a pnp in which a series circuit of a diode D ₁ and a capacitor C ₁ is connected in parallel to a voltage dividing resistor R ₂ in the drive circuit 1 and a base-emitter is connected to both ends of the capacitor C _1.
A transistor Q ₃ of the shape is provided as a first switching element, and the collector of the transistor Q ₃ is connected to the collector of the transistor Q ₂ via a current limiting resistor R ₅ . The diode D ₁ has an anode connected to the gate of the MOSFET Q ₁ , and the emitter of the transistor Q ₃ is connected to the connection point between the cathode of the diode D ₁ and the capacitor C ₁ .

Next, the operation of this embodiment will be described. Since the operation of the drive circuit 1 is the same as the conventional configuration shown in FIG. 4,
Only the protection function against overcurrent will be described. First,
When the control signal is at the H level in a normal state, the diode D ₁ is connected in the reverse direction, so that the capacitor C ₁ is not charged and the transistor Q ₃ is also kept off. When the control signal is at L level, M
The residual charge due to the gate-source capacitance of the OSFET Q ₁ is released through the transistor Q ₂ . At this time, the circuit constant is set so that the transistor Q ₃ is kept off.

The drain Disruption of MOSFET Q ₁ - the gate is short-circuited, because a high voltage is applied to the gate of MOSFET Q ₁ through <br/> load Z from the power source E, power E → load Z → MOSFET Q ₁ → diode D ₁ → capacitor C _{1 in} the path of capacitor C
₁ is charged and the voltage across capacitor C ₁ rises, turning on transistor Q ₃ . As a result, the excessive current flowing through the gate of the MOSFET Q ₁ is diode D ₁ → transistor Q ₃ → resistance R ₅
Will be bypassed through. Like this, MO
Even if an excessive current flows to the control signal source 2 due to the destruction of the SFET Q ₁ , the current is absorbed by the capacitor C ₁ and then bypassed in a state of being limited by the resistor R ₅ by turning on the transistor Q _3. Therefore, as a result, the drive circuit 1 and the control signal source 2 are protected.

As described above, the MOSFET Q ₁
Of the normal behaves like a conventional configuration shown in FIG. 4, M
When the drain-gate is short-circuited due to the destruction of the OSFET Q _1, the capacitor C ₁ absorbs the abrupt change of the voltage and the sudden current, and
Immediately after that, the transistor Q ₃ is turned on and the resistor R ₅ for current limiting is inserted between the gate and the source, whereby an excessive current can be suppressed. That is, it is possible to prevent an excessive current from flowing through the drive circuit 1 and the control signal source 2.

Second Embodiment In this embodiment, as shown in FIG. 2, in the configuration of the first embodiment, instead of connecting _one end of the resistor R ₅ to the source of the MOSFET Q ₁ , a second addition is added. It has a configuration connected in turn parallel to the emitter - connected to the base of the transistor Q ₄ of npn type, further the collector of the transistor Q ₄ as a switching element - the emitter-collector of the transistor Q _2. The transistor Q ₄ provided in this embodiment short-circuits both ends of the transistor Q ₂ when it is turned on, thereby short-circuiting the output terminals of the control signal source 2 and bypassing the overcurrent from the MOSFET Q ₁ .

More specifically, in the present embodiment as well, similar to the configuration of the first embodiment, in the normal condition, the control signal is generated in response to the control signal.
MOSFET Q ₁ is turned on and off while transistor Q ₃ is kept off. That is, the transistor Q ₃ is because it is off, the transistor Q ₄ are kept turned off not applied bias. On the other hand, MOSFET Q
_{When an} excessive current flows from the gate due to the destruction of transistor 1, the transistor Q ₃ is operated by the same operation as in the first embodiment.
Turns on. Therefore, the transistor Q ₄ is biased and turned on, and the current flowing from the gate passes through the resistor R ₂ and the transistor Q ₄ ,
The flow to the control signal source 2 is prevented. Further, in this configuration, the control signal from the control signal source 2 is also cut off by the transistor Q ₄ , so that protection against overcurrent can be performed more reliably. In addition, in this embodiment, immediately after the destruction of the MOSFET Q ₁ , the capacitor C
₁ suppresses a rapid change in voltage, and a part of the excessive current also flows through the path of diode D ₁ → transistor Q ₂ → resistor R ₅ → transistor Q ₄ until just before transistor Q ₅ is turned on. Other configurations and operations are similar to those of the first embodiment.

(Embodiment 3) In this embodiment, as shown in FIG. 3, in addition to the configuration of Embodiment ₂ , a pnp-type transistor Q as a third switching element is provided between resistors R ₂ and R _{3. 5} of emitter - insert the collector, the collector of the transistor Q ₅ - as well as connecting a resistor between the base R _6, has a structure in which the base of the transistor Q ₅ is connected to the collector of the transistor Q _4. That is, the collector of the transistor Q ₅ is connected to the resistor R ₃ , and the emitter of the transistor Q ₅ is the resistor R _2.
Connected to. Transistor Q ₅ is MOS when off
It has a function of completely separating the FET Q ₁ and the control signal source 2.

The basic operation of this embodiment is similar to that of the first embodiment. However, the residual charge of the MOSFET Q ₁ is discharged only through the resistor R ₁ and is not discharged through the transistor Q ₂ . That is, when the control signal is at the H level, the transistor Q ₅ functions as a diode to turn on the MOSFET Q ₁ , and when the control signal is at the L level, the transistor Q ₂
Is cut off.

On the other hand, if the MOSFET Q ₁ is destroyed and the drain-source is short-circuited, the capacitor C ₁ is charged through the diode D ₁ as in the first embodiment, and the voltage across the capacitor C ₁ rises, causing the transistor Q _{3 to} rise. Turns on. If the transistor _{Q 3} is turned on, the transistor _{Q 4} is turned on, to turn off the transistor _{Q 5.} In other words, MOSFET Q ₁
It is possible to prevent an overcurrent from the drain of the control signal source 2 from flowing into the control signal source 2. Further, when the transistor Q ₄ is turned on, the resistor R ₃ and the resistor R ₃ are placed between the output terminals of the control signal source 2.
It will be short-circuited via ₆ . Furthermore, MOSF
A rapid change in the voltage immediately after the ET Q ₁ is destroyed is absorbed by the capacitor C ₁ , and the overcurrent flows in a state of being current-limited through the diode D ₁ → transistor Q ₃ → resistor R ₅ → transistor Q ₄ . Rapid changes in current are also suppressed. Other configurations and operations are similar to those of the first embodiment.

[0024] The door of the embodiments described above transistors _Q 2 ~
Q ₅ can be replaced with a FET or the like.

[0025]

According to the present invention as described above, when a drain and a gate by the destruction of the MOSFET current from the power source shorted tends to flow toward the control signal source from the gate, the capacitor is charged through the diode it makes the first switching element turns on, MOSF
Even if the potential of the gate suddenly fluctuates immediately after the breakdown of ET , it is absorbed to some extent by the capacitor, and it is possible to prevent the control signal source from being destroyed due to this type of fluctuation.

Further, as in the first aspect of the invention, the series circuit of the first switching element and the current limiting resistor, which is turned on when the voltage across the capacitor becomes a predetermined voltage or more, is a MOSF.
By adopting the configuration connected between the ET gate and the source of, between the first switch element and the MOSFET gate and source through the current limiting resistor is connected to the MOSFET when the abnormality, the control signal from the gate of the MOSFET There is an advantage that the current that is about to flow into the source is bypassed, and it is possible to prevent the control signal source from being destroyed due to an overcurrent flowing into the control signal source. Moreover, the MOSFET
Since the gate and the source are connected via the current limiting resistor, there is an advantage that the first switching element can be prevented from being destroyed by an overcurrent.

According to a second aspect of the present invention, the second switching element which is turned on when the first switching element which is turned on when the voltage across the capacitor is equal to or higher than a predetermined voltage is provided between the output terminals of the control signal source. When the first switching element is turned on, the second switching element is turned on, so that the output terminals of the control signal source are short-circuited, and the current and control from the gate of the MOSFET to the control signal source are controlled. The control signals output from the signal source are both bypassed through the second switching element, and as a result, the MOSFET side and the control signal source side do not affect each other, and the control signal from the gate of the MOSFET <br />. It is possible to prevent the control signal source from being destroyed by the overcurrent flowing into the source, and in this state, the control signal MOSFE There is an advantage that the flow into T is also stopped.

According to the third aspect of the present invention, the third switching element which is turned off when the second switching element is turned on is inserted between the control signal source and the gate of the MOSFET. There is an advantage that the signal source and the MOSFET can be completely separated by the third switching element, and the control signal source can be surely protected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

[Explanation of symbols]

1 Drive Circuit 2 Control Signal Source C ₁ Capacitor D ₁ Diode E Power Supply Q ₁ MOSFET Q ₃ Transistor (First Switching Element) Q ₄ Transistor (Second Switching Element) Q ₅ Transistor (Third Switching Element) R ₁ Resistance (first voltage dividing resistance) R ₂ resistance (second voltage dividing resistance) R ₅ resistance (current limiting resistance) Z load

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-2-266614 (JP, A) JP-A-5-343972 (JP, A) JP-A-7-236285 (JP, A) JP-A-7- 297697 (JP, A) JP 7-297700 (JP, A) JP 7-322641 (JP, A) JP 8-18417 (JP, A) JP 8-130453 (JP, A) Actual Kaihei 6-59909 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02H 7/20 H03K 17/08

Claims (4)

(57) [Claims] 1. A MOSF inserted between a power supply and a load.
Is inserted between the control signal source for generating a gate control signal ET, a driving circuit for controlling the MOSFET in accordance with the control signal, the control signal source from the gate of the MOSFET during a short circuit of the MOSFET drain and gate When a current flows toward the capacitor, the capacitor is charged through the diode, the first switching element that turns on when the voltage across the capacitor exceeds a predetermined voltage, and one output terminal of the control signal source M commonly connected
A MOSFET drive circuit comprising a current limiting resistor having a series circuit of a first switching element inserted between the source and gate of the OSFET . 2. A MOSF inserted between a power supply and a load.
Is inserted between the control signal source for generating a gate control signal ET, a driving circuit for controlling the MOSFET in accordance with the control signal, the control signal source from the gate of the MOSFET during a short circuit of the MOSFET drain and gate Connected between the output terminal of the control signal source and the first switching element that is turned on when the voltage across the capacitor becomes equal to or higher than the predetermined voltage when the current flows toward the A drive circuit for a MOSFET , comprising: a second switching element in which a first switching element is connected to a gate via a current limiting resistor so that the switching element turns on when the switching element turns on. 3. A MOSF inserted between a power supply and a load.
Is inserted between the control signal source for generating a gate control signal ET, a driving circuit for controlling the MOSFET in accordance with the control signal, the control signal source from the gate of the MOSFET during a short circuit of the MOSFET drain and gate Connected between the output terminal of the control signal source and the first switching element that is turned on when the voltage across the capacitor becomes equal to or higher than the predetermined voltage when the current flows toward the A second switching element in which the first switching element is connected to the gate via a current limiting resistor so that the switching element is turned on when the switching element is turned on, and a second switching element inserted between the control signal source and the gate of the MOSFET . MOSF characterized in that it comprises a third switching element turns off when the switching element
ET drive circuit. 4. A pair of voltage dividing resistors connected between output terminals of a control signal source in a series circuit connected in series with each other, one voltage dividing resistor between the gate and the source of the MOSFET. To the control signal source and MO
It is inserted between the gate of the SFET and the series circuit of the diode and the capacitor is connected in parallel to the other voltage dividing resistor, and the first switching element is a pnp type transistor, and is connected to the cathode of the diode. An emitter is connected to a connection point with one end of the capacitor, a base is connected to the other end of the capacitor, and a collector is connected to one end of the current limiting resistor.
A drive circuit for a MOSFET according to any one of 1.