JP5733627B2 - Gate drive circuit - Google Patents

Gate drive circuit Download PDF

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JP5733627B2
JP5733627B2 JP2011161330A JP2011161330A JP5733627B2 JP 5733627 B2 JP5733627 B2 JP 5733627B2 JP 2011161330 A JP2011161330 A JP 2011161330A JP 2011161330 A JP2011161330 A JP 2011161330A JP 5733627 B2 JP5733627 B2 JP 5733627B2
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switching element
gate
capacitor
drive circuit
voltage
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JP2013026924A (en
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町田 修
修 町田
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サンケン電気株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion
    • Y02B70/14Reduction of losses in power supplies
    • Y02B70/1483Reduction of losses in power supplies by using wide band gap based power semiconductors, i.e. power converters integrating silicon carbide [SiC], gallium nitride [GaN], gallium arsenide [GaAs] or diamond power switches

Description

  The present invention relates to a gate drive circuit that drives a gate of a switching element.

  Since the GaN device has a potential far surpassing that of the existing Si device, its practical application is awaited. However, since a normal GaNFET is normally on, a negative power source is required.

  On the other hand, normally-off type GaNFETs are very difficult to manufacture. Further, the normally-off GaNFET has a threshold voltage of about +1 to 3 V, and the threshold voltage is much lower than that of the existing SiMOSFET (Problem 1).

  Also, normally-off GaNFETs have a diode characteristic in which a large current flows when a large voltage is applied, instead of an insulating structure like a SiMOSFET between the gate and the source. For this reason, when a large voltage is applied to the gate, the normally-off GaNFET is easily broken (Problem 2).

  That is, normally-off GaNFETs cannot use the existing gate drive circuit for SiMOSFET (IGBT (Insulated Gate Bipolar Transistor)) as they are, and need a drive circuit dedicated to normally-off GaNFETs.

  As for problem 1, it is necessary to apply a voltage sufficiently lower than the threshold voltage in order to shorten the turn-off time. It is necessary to apply a voltage sufficiently lower than the threshold voltage (+1 V), that is, a negative voltage of 0 V or less. For this reason, even if the device can be normally off, it is not preferable that a negative power source is required.

  In order to shorten the turn-on time for Problem 2, it is necessary to apply a voltage sufficiently higher than the threshold voltage (essentially, an instantaneous large current is required instead of a voltage value. It ’s better to have a higher voltage to earn). However, a high voltage of 10 V or more like SiMOSFET cannot be applied to the gate of normally-off GaNFET.

  Therefore, as a proposal for simultaneously solving the problem 1 and the problem 2, as shown in FIGS. 3A to 3C, a capacitor is inserted at a place where a gate resistance in a normal MOSFET drive circuit is inserted. There is a method of applying a CR parallel circuit of C1 and resistor R1.

2010-511165

  However, in this method, as shown in FIG. 4, when the switching frequency and duty ratio change, the negative voltage values P1, P2, and P3 immediately before the switching element is turned on also change at the same time. Switching time) will fluctuate.

  Further, if the frequency and duty can be limited within a certain range, the above two problems can be avoided by selecting the values of the resistor and the capacitor well, returning the gate voltage to zero volts, and performing the regenerative operation or turn-on. However, the conditions are limited and the device is vulnerable to malfunction caused by noise due to the low threshold voltage.

  An object of the present invention is to provide a gate drive circuit in which switching characteristics at the time of turn-on do not vary and a switching element can be stably turned off.

  A gate drive circuit for driving on and off the first switching element by applying a control signal from the control circuit to the gate of the first switching element having a drain, a source and a gate and made of a wide band gap semiconductor. A parallel circuit including a first capacitor and a first resistor connected between the control circuit and the gate of the first switching element; and a second capacitor in parallel with the parallel circuit. And a second circuit connected between the main electrodes of the second switching element are connected in series, and the gate of the switching element of the second switching element is the source terminal of the first switching element To the first capacitor through the anode of the first diode from the connection point between the second capacitor and the main electrode of the second switching element. Is connected to the source terminal of the switching element, characterized in that it comprises a means for biasing the gate to the negative potential of the first switching element relative to the off signal of the control signal.

According to the present invention, after the charge stored in the first capacitor is discharged through the resistor R1 in response to the OFF signal of the control signal, the voltage of the second capacitor having a large charge capacity is changed to the second switching. Since the gate of the first switching element is biased to a negative potential via the element, a stable bias voltage can be applied regardless of the off period, switching characteristics at the time of turn-on do not fluctuate, and switching without generating power loss The element can be turned on stably.
Further, since the gate signal of the second switching element is given by the on / off signal of the control signal and the voltage of the second capacitor, a complicated drive circuit is unnecessary.

2 is a circuit configuration diagram and a sequence diagram of a gate drive circuit according to Embodiment 1. FIG. FIG. 6 is a circuit configuration diagram and a sequence diagram of a gate drive circuit according to a second embodiment. It is a circuit block diagram of the conventional gate drive circuit. It is a figure which shows a mode that turn-on characteristics are fluctuate | varied by the change of the frequency of a conventional gate drive circuit, or a duty.

  The gate drive circuit according to the embodiment of the present invention will be described below.

  1 is a circuit configuration diagram and a sequence diagram of a gate drive circuit according to a first embodiment of the present invention. In the gate drive circuit shown in FIG. 1A, a pulse signal Sig is generated from a pulse generator Pu1. The pulse generator Pu1 corresponds to a control circuit, and the pulse signal Sig corresponds to a control signal.

The switching element Q1 is made of a GaN FET, and has a gate, a drain, and a source. A CR parallel circuit of a capacitor C1 and a resistor R1 is connected between the gate of the switching element Q1 and the connection point of the pulse generator Pu1.
The pulse signal Sig is applied to the gate of the switching element Q1 through a CR parallel circuit of a capacitor C1 and a resistor R1.

The CR parallel circuit is connected in parallel to a series circuit in which a second resistor and a second resistor are connected in series via a source and drain of a second switching element made of a MOSFET or the like. The switching element gate of the first switching element is connected to the source terminal of the first switching element, and is connected to the first capacitor via the anode of the first diode from the connection point between the second capacitor and the source of the second switching element. Connected to the source terminal of the switching element.
Note that when the gate-source capacitances of the first switching element and the second switching element are Cg1 and Cg2, respectively, the capacitances of the first capacitor and the second capacitor are C2 >>C1> Cg1 >> The relationship of Cg2 is preferable.

  According to the above configuration, when the switching element Q1 is turned on, high-speed switching is realized by the effect of the CR parallel circuit. When the switching element Q1 is in an on-steady state, the capacitor C1 receives from the pulse generator Pu1 an H level pulse signal Sig and a gate-source voltage Vg1 of the switching element Q1 (= forward voltage drop of the gate-source equivalent diode). ) And the difference voltage is charged.

In the gate drive circuit of the first embodiment, when the H level pulse signal Sig is input from the pulse generator Pu1, the path for charging the CR parallel circuit of the capacitor C1 and the resistor R1 is simultaneously passed through the diode D1. There is a path through which the capacitor C2 is charged.
Here, in the CR parallel circuit, a series circuit in which a second resistor R2 and a second resistor R2 are connected in series via the main electrode of the second capacitor C2 and the second switching element Q2 is connected in parallel. A reverse bias voltage due to the forward voltage of the diode D1 is applied to the source-gate voltage of the second switching element, so that Q2 is turned OFF. There is no path for current to flow from the series circuit to the gate of the first switching element Q1.
The forward voltage VF of the diode D1 is preferably selected to be smaller than the forward voltage of the body diode of Q2.

  When the switching element Q1 is turned off, a negative voltage due to the charge (voltage) stored in the capacitor C1 is applied to the gate of the switching element Q1, thereby realizing a fast turn-off of the switching element Q1.

  During the OFF period of the switching element Q1, the capacitor C1 is discharged with a time constant determined by the first capacitor C1 and the first resistor R1 of the CR parallel circuit.

As the CR parallel circuit starts discharging, the connection voltage of the second capacitor C2, the diode D1, and the source of the second switching element Q2 in the series circuit becomes a negative potential with respect to the source potential of the first switching element Q1. Become.
Since the gate of the second switching element Q2 is connected to the source of the first switching element Q1, the charging voltage of the second capacitor C2 is applied between the gate and the source to be turned on. Therefore, the charging voltage of the capacitor C2 forms a discharging circuit of the capacitor C2, the CR parallel circuit, the resistor R2, the second switching element Q2, and the capacitor C2. After the CR parallel circuit is discharged, a voltage determined by the voltage division ratio between the resistor R1 and the resistor R2 is applied to the gate of the switching element Q1 as a negative potential due to the discharge of the capacitor C2 in the series circuit.

  If the capacitor C1 has a sufficiently small capacity compared to the capacitor C2, the charge of the capacitor C1 during the extremely short time during the turn-off period is equal to the resistance ratio of the resistor R1 and the resistor R2 with respect to the charging voltage of the capacitor C2. Discharged. Further, by setting the charge capacity of the capacitor C2 to be sufficiently large compared to the capacitor C1, and by increasing the discharge time constant of the capacitor C2, the resistor R1, and the resistor R2, the switching element can be used regardless of the frequency and the duty ratio. Q1 can be stably biased to a negative potential.

  Therefore, as shown in FIG. 1B, by setting the gate-source voltage of the switching element Q1 in the switching-off state to a stable negative potential, it is resistant to noise and can realize a stable switching on / off operation. .

FIG. 2 is a circuit configuration diagram and a sequence diagram of the gate drive circuit according to the second embodiment. In the second embodiment shown in FIG. 2A, a Zener diode ZD1 is added between the connection of the second capacitor C2 and the diode D1 in the first embodiment. Specifically, a Zener diode ZD1 is connected in series in a direction that increases the forward voltage of the diode D1, and the source of the second switching element Q2 is connected to a connection point between the second capacitor C2 and the cathode of the Zener diode ZD1. The
In Example 2, it is preferable to use a normally-off GaN FET made of a wide band gap semiconductor as the second switching element Q2.
Further, by configuring the first switching element Q1 and the second switching element Q2 on the same substrate, it is possible to reduce the number of components and the component mounting.

  Also in the configuration of the second embodiment, when an H level pulse signal Sig is input from the pulse generator Pu1 as in the first embodiment, a Zener diode is simultaneously formed along with a path for charging the CR parallel circuit of the capacitor C1 and the resistor R1. There is a path through which capacitor C2 is charged via ZD1 and diode D1.

  Here, as shown in FIG. 2B, the charging voltage of the capacitor C2 decreases by the Zener voltage Vz of the Zener diode ZD1, and the negative voltage of the gate-source voltage of the switching element Q1 in the switching-off state also decreases. .

  According to such a configuration, the negative voltage bias of the gate-source voltage of the switching element Q1 in the switching-off state can be adjusted by adjusting the Zener voltage Vz of the Zener diode ZD1.

  Further, the switching element applied to the present invention is not limited to GaNFET, but may be Si or SiC. The present invention is also applicable to a device having a low threshold voltage and a JFET (junction FET) behavior that is not an insulated gate.

Q1, Q2 Switching element C1, C2 Capacitor D1 Diode ZD1 Zener diode R1, R2 Resistance

Claims (5)

  1. By applying a control signal from a control circuit to the gate of the first switching element having a drain, a source, and a gate and made of a wide band gap semiconductor, the first switching element is formed.
    A gate drive circuit for driving on and off the switching element of
    A parallel circuit connected between the control circuit and the gate of the first switching element and comprising a first capacitor and a first resistor;
    In parallel with the parallel circuit, a second capacitor and a second band gap semiconductor are formed.
    A series circuit in which the second resistor is connected in series via the main electrodes of the switching element is connected,
    A gate of the switching element of the second switching element is connected to a source terminal of the first switching element;
    A connection point between the second capacitor and the main electrode of the second switching element is connected to the source terminal of the first switching element via the anode of the first diode;
    Means for biasing the gate of the first switching element to a negative potential in response to an off signal of the control signal.
  2. The capacity of the first capacitor is smaller than the capacity of the second capacitor, and the first capacitor
    2. The gate drive circuit according to claim 1, wherein the switching element is larger than a gate-source capacitance.
  3. The connection between the connection point between the second capacitor and the main electrode of the second switching element and the anode of the first diode is connected via a first Zener diode. Item 3. The gate drive circuit according to Item 1 or 2.
  4. 4. The gate drive circuit according to claim 1, wherein the second switching element has a drain, a source, and a gate and is made of a wide band gap semiconductor.
  5. The gate drive circuit according to claim 4, wherein the first switching element and the second switching element are formed of a wide band gap semiconductor configured on the same substrate.
JP2011161330A 2011-07-22 2011-07-22 Gate drive circuit Active JP5733627B2 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10263538B2 (en) 2016-07-12 2019-04-16 Kabushiki Kaisha Toshiba Semiconductor device and power conversion device

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Publication number Priority date Publication date Assignee Title
JP5780489B2 (en) * 2011-09-08 2015-09-16 サンケン電気株式会社 gate drive circuit
JP6110161B2 (en) * 2013-03-01 2017-04-05 田淵電機株式会社 Switching power supply circuit
JP2016167498A (en) * 2015-03-09 2016-09-15 株式会社東芝 Semiconductor device
WO2018047689A1 (en) * 2016-09-08 2018-03-15 株式会社村田製作所 Switching circuit
US10374591B2 (en) * 2017-01-03 2019-08-06 General Electric Company Systems and methods for a gate drive circuit

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JP4456569B2 (en) * 2006-02-21 2010-04-28 株式会社デンソー Power switching element drive circuit
JP2008235952A (en) * 2007-03-16 2008-10-02 Furukawa Electric Co Ltd:The Driving circuit for depletion type switching element
JP4858318B2 (en) * 2007-06-06 2012-01-18 株式会社デンソー Vehicle control device
JP2010051165A (en) * 2008-07-24 2010-03-04 Panasonic Corp Gate drive circuit of semiconductor apparatus and power conversion apparatus using the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10263538B2 (en) 2016-07-12 2019-04-16 Kabushiki Kaisha Toshiba Semiconductor device and power conversion device

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