JP5563050B2 - Gate drive circuit and power semiconductor module - Google Patents

Description

Embodiments described herein relate generally to a gate drive circuit and a power semiconductor module for a voltage-controlled switching element.

  A power converter represented by an inverter is used in an electric vehicle, a solar power generation system, and the like, and it is required to reduce the loss of the power converter in order to improve the efficiency of the entire system.

  About 50% of the loss of the power conversion device is the loss of the semiconductor switching element, and the reduction of the loss of the semiconductor switching element is an important technology.

In recent years, MOSFETs (Metal Oxide Semiconductor Field Effect), which are voltage controlled transistors, are used as power switching devices in semiconductor switching devices.
Transistor) and IGBT (Insulated)
Gate Bipolar Transistor) is widely used.

  These switching elements apply a voltage of about +15 V from the gate drive circuit between the gate and the source (or between the gate and the emitter), so that the voltage between the gate and the source (or between the gate and the emitter) exceeds the threshold, The drain-source (or collector-emitter) becomes conductive and is turned on.

  When the switching element is turned off, the voltage between the gate and the source (or between the gate and the emitter) is set to a threshold value or less by setting the output voltage of the gate driving circuit to a voltage of about 0V or −15V.

  The gate electrodes of the MOSFET and IGBT are structured to be covered with an oxide film, the gate-source capacitance (or gate-emitter capacitance) between the gate electrode and the source electrode (or emitter electrode), and the gate electrode and drain. A gate-drain capacitance (or gate-collector capacitance) between the electrodes (or collector electrodes) is formed.

  Therefore, an equivalent circuit on the gate side of the switching element is a parallel connection of a gate-source capacitance (or gate-emitter capacitance) and a gate-drain capacitor (or gate-collector capacitance).

  Usually, a gate resistor is connected between the gate drive circuit and the gate electrode of the switching element. Therefore, when a voltage of about +15 V is applied from the gate drive circuit to turn on the switching element, the gate-source capacitance (or gate-emitter capacitance) and the gate-drain capacitance (or gate-collector) via the gate resistance. Will be charged).

  In a standard hard switching circuit, the capacitance charging time is changed by changing the value of the gate circuit, and the switching time of the switching element is adjusted.

Since the switching loss can be reduced by shortening the switching time, in order to reduce the loss of the switching element, a method of reducing the gate resistance value and shortening the switching time is used.

JP 2009-290287 A

  In the inverter circuit shown in FIG. 1, the upper and lower arms are configured by installing switching elements on the high side and the low side. When the high side switching element is on, the low side switching element is off and the high side switching element is off. The low-side switching element is controlled to be in the on state when in the state, and the other is in the off state when either one is on. Also, if both switching elements are turned on simultaneously, a short-circuit current greater than the rated current of the switching element flows in the upper and lower arms, and the switching element may be destroyed. Therefore, a period (dead time) in which both elements are simultaneously turned off is provided so as not to be turned on at the same time.

  Here, as shown in FIG. 2, when one switching element is turned on from the off state, the drain-source (or collector-emitter) voltage of the other switching element is automatically changed from 0 V to the input DC voltage. To change. Accordingly, the capacitance between the gate and the drain (or between the gate and the collector) is charged to almost the same value as the input DC voltage.

  At this time, displacement current flows through the gate-drain (or gate-collector) capacitance, and this current charges the gate-source (or gate-emitter) capacitance, causing the gate voltage to exceed the threshold and switching. The element may be turned on.

  Since the peak value of the displacement current is proportional to the time change rate (dV / dt) of the drain-source voltage (or collector-emitter) of the switching element, the switching time is shortened to reduce the switching loss of the switching element. Then, the peak value of the displacement current increases, and the switching element is easily turned on by the principle described above.

  In view of this, a gate drive circuit that prevents the gate voltage from exceeding a threshold value by short-circuiting the gate-source (or gate-emitter) with a semiconductor switching element has been studied.

  However, in such a circuit, it is necessary to add at least an element such as two diodes, one resistor, and one switching element in addition to the components that normally constitute the gate drive circuit. Further, the switching element needs to be operated in synchronization with a control signal of a normal gate drive circuit, so that a control device for generating the synchronization signal is required and the design of the entire circuit becomes complicated. .

Embodiments of the present invention are for solving such problems, and realize a gate drive circuit capable of high-speed and low-loss operation without causing malfunction of a switching element with a simple circuit configuration with a small number of components. For the purpose.

A gate driving circuit according to a first embodiment for achieving the above object includes two switching elements connected in series, a high-side switching element at a higher potential side than a connection point, and a low-side switching element at a low potential side. When a positive voltage is output from the low side gate drive circuit, the high side gate drive circuit maintains 0V or outputs a negative voltage, and the output from the low side gate drive circuit outputs 0V or a negative voltage. In the power conversion circuit where the high-side and low-side gate drive circuits are controlled so that a positive voltage is output from the high-side gate drive circuit, the Nch node is not connected between the gate and source of the high-side and low-side switching elements. Connect the drain and source of a Marie-on type auxiliary switching element and drive the primary side of the transformer to the gate When the positive gate drive voltage is output from the gate drive circuit, the transformer secondary is applied so that a negative voltage pulse is applied between the gate and source of the Nch normally-on switching element. The side is connected between the gate and source of an Nch normally-on switching element.

It is an equivalent circuit diagram which shows one leg part of the conventional inverter circuit. It is a gate voltage waveform diagram generated between the gate and source of a switching element in a conventional inverter circuit. FIG. 3 is an equivalent circuit diagram of the gate drive circuit according to the first embodiment. 2 is a simulation waveform diagram of Example 1. FIG. 6 is an equivalent circuit diagram of a gate drive circuit according to Embodiment 2. FIG. 6 is an equivalent circuit diagram of a gate drive circuit according to Embodiment 3. FIG.

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

[First Embodiment]
First, the gate drive circuit according to the first embodiment will be described.
FIG. 3 is an equivalent circuit of the gate drive circuit according to the embodiment of the present invention. The primary side of the transformer 15 is connected to the output terminal of the low side gate drive circuit 2, and a voltage having a polarity opposite to the primary side voltage of the transformer is generated between the gate and source of the high side switching element 5. The secondary side is connected.

  When a positive gate drive voltage is output from the low side gate drive circuit 2, a negative voltage pulse is applied between the gate and source of the high side switching element 5 via the transformer 15, and the gate-source voltage is below a threshold value. When the low-side switching element 6 is turned on, the high-side switching element 5 maintains the off state.

  FIG. 4 shows a circuit simulation result of the gate drive circuit according to the first embodiment. It can be confirmed that a negative pulse voltage is applied to the high-side gate-emitter voltage during the period in which the low-side gate-emitter voltage changes from 0V to + 15V. In addition, since no high-side collector current flows, it can be confirmed that the high-side switching element maintains an off state.

  According to this embodiment, the state of various voltages and currents of the switching element on the turn-on side is detected, automatically without adding an external control circuit for feeding back the state to the gate drive side, A favorable effect is obtained in that the switching element on the non-turned-on side can be maintained in the off state.

  As the transformer in the first embodiment, an air-core transformer is preferably used. This is because a transformer having a magnetic core generates hysteresis loss and does not contribute to loss reduction. Use of an air core transformer is advantageous in terms of cost.

In this embodiment, the gate driving circuit preferably outputs a voltage of 0 V when the switching element is in the off state and a positive voltage when the switching element is in the on state.
The reason is as follows. In other words, the problem to be solved in the present embodiment is to eliminate the possibility that the gate-source capacitance is charged by the displacement current and the voltage exceeds the threshold value between the gate and the source, resulting in malfunction. . As a simple method for preventing this phenomenon, there is a method in which the charging voltage does not exceed the threshold value by applying a negative bias (a negative voltage is applied) between the gate and the source when the switching element is in the OFF state. . In this case, since a negative power source is separately required, there is a drawback that the cost of the gate circuit increases. According to the present embodiment, since a negative power source is not necessary, the cost of the power conversion device can be reduced.

[Second Embodiment]
FIG. 5 is an equivalent circuit of the gate drive circuit according to the second embodiment. The drain and source of the Nch normally-on type switching element 13 are connected between the gate and source of the high side switching element 5, the primary side of the transformer 15 is connected to the output of the high side gate driving circuit 1, and high side gate driving is performed. When a positive gate drive voltage is output from the circuit 1, the secondary side of the transformer 15 is Nch normally on so that a negative voltage pulse is applied between the gate and source of the Nch normally on switching element 13. It connects between the gate and source of the type switching element 13. Since the low side has the same configuration and operation principle as the high side, description thereof is omitted.

  When a positive voltage is output from the low side gate driving circuit 2, the high side gate driving circuit 1 maintains 0V or outputs a negative voltage, and the output from the low side gate driving circuit 2 outputs 0V or a negative voltage. When outputting, the high side gate driving circuit 1 and the low side gate driving circuit 2 control so that a positive voltage is output from the high side gate driving circuit 1.

  When a positive voltage is output from the low-side gate drive circuit 2 and the low-side switching element 6 is turned on, the gate-source voltage of the Nch normally-on type switching element 13 becomes 0 V or positive and becomes an on state, and the high-side switching is performed. The gate and the source of the element 5 are short-circuited, and the high-side switching element 5 is kept off.

  According to this embodiment, in particular, the state of various voltages and currents of the switching element on the turn-on side is detected, and it is automatically performed without adding an external control circuit for feeding back the state to the gate driving side. A favorable effect is obtained in that the off state of the switching element on the non-turned-on side can be maintained. Further, since the gate and the source of the high side switching element 5 are short-circuited even after the turn-on operation of the low side switching element 6 is completed, the high side switching element 5 maintains the off state even when some noise enters from the outside. A favorable effect is acquired at the point which can be performed.

  As the transformer in the first embodiment, an air-core transformer is preferably used. This is because a transformer having a magnetic core generates hysteresis loss and does not contribute to loss reduction.

Also in this embodiment, it is preferable that the gate drive circuit outputs a voltage of 0 V when the switching element is in the off state and a positive voltage when in the on state, as in the first embodiment.

[Third Embodiment]
FIG. 6 is an equivalent circuit of a gate drive circuit according to the third embodiment of the present invention. The drain and source of the Pch normally-on type switching element 14 are connected between the gate and source of the high-side switching element 5, and the gate of the Pch normally-on type switching element 14 is driven by the high-side gate drive circuit 1. Since the low side has the same configuration and operation principle as the high side, description thereof is omitted.

  When a positive voltage is output from the low side gate driving circuit 2, the high side gate driving circuit 1 maintains 0V or outputs a negative voltage, and the output from the low side gate driving circuit 2 outputs 0V or a negative voltage. When outputting, the high side gate driving circuit 1 and the low side gate driving circuit 2 are controlled so that a positive voltage is output from the high side gate driving circuit 1.

  When a positive voltage is output from the low-side gate drive circuit 2 and the low-side switching element 6 is turned on, the gate-source voltage of the Pch normally-on type switching element 14 becomes 0 V or positive and becomes an on state, and the high side The gate and the source of the switching element 5 are short-circuited, and the high-side switching element 5 is kept off.

  According to this embodiment, in particular, the state of various voltages and currents of the switching element on the turn-on side is detected, and it is automatically performed without adding an external control circuit for feeding back the state to the gate driving side. A favorable effect is obtained in that the off state of the switching element on the non-turned-on side can be maintained. Further, since the gate and the source of the high side switching element 5 are short-circuited even after the turn-on operation of the low side switching element 6 is completed, the high side switching element 5 maintains the off state even when some noise enters from the outside. A favorable effect is acquired at the point which can be performed.

  As the transformer in the first embodiment, an air-core transformer is preferably used. This is because a transformer having a magnetic core generates hysteresis loss and does not contribute to loss reduction.

Also in this embodiment, it is preferable that the gate drive circuit outputs a voltage of 0 V when the switching element is in the off state and a positive voltage when in the on state, as in the first embodiment.

As described above, the three embodiments have been described. According to these configurations, the gate driving circuit to which the circuit for holding the gate-source voltage (or the gate-emitter) voltage of the switching element below the threshold is added. This can be realized with a simple circuit configuration with a small number of parts.

[Semiconductor chip, module, package]
In each of the above embodiments, the drive circuit has been described as an embodiment of the present invention. However, the drive circuit of this embodiment is for preventing delay in pulse output, waveform dullness, increase in wiring resistance, and the like. It is preferable that the wiring length is as short as possible. Elements that can be formed on the same semiconductor chip are preferably assembled and formed on the same IC chip. Moreover, it is preferable to enclose the same package as a package to form a module.

  More specifically, in the gate drive circuit described above, the transformer is enclosed in the same package as the low-side gate drive circuit, the high-side gate drive circuit, the Nch normally-on switching element, or the Pch normally-on switching element. Thus, a gate driving IC can be obtained. Further, the Nch-type normally-on type switching element and the Pch-type normally-on type switching element can be integrated on the same semiconductor chip as the main switching element to form a switching element.

Furthermore, a high-side gate driving circuit, a low-side gate driving circuit, a transformer, a high-side domain switching element, and a low-side domain switching element can be enclosed in the same package to form a power semiconductor module.
Alternatively, a high-side gate drive circuit, a low-side gate drive circuit, a transformer, an Nch normally-on type switching element, a high-side domain switching element, and a low-side domain switching element can be enclosed in the same package to form a power semiconductor module.
In addition, a high-side gate driving circuit, a low-side gate driving circuit, a Pch normally-on type switching element, a high-side domain switching element, and a low-side domain switching element can be enclosed in the same package to form a power semiconductor module.

The following effects are expected by the modularization and the same packaging. That is, (1) for the circuit engineer, the connection work of the air core transformer becomes unnecessary. (2) By combining an air core transformer having an optimum parameter in accordance with parameters of various power semiconductors (switching elements), a circuit engineer can employ components such as a power semiconductor module whose characteristics are optimized. (3) The characteristics of the power semiconductor chip and the air core transformer are improved.

As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... High side gate drive circuit 2 ... Low side gate drive circuit 3, 4, 14 ... Resistance 5 ... High side switching element 6 ... Low side switching element 7, 8 ... Diode 9, 10, 11, 12 ... Capacitor 13 ... Nch normally ON type switching element 14 ... Pch normally on type switching element 15 ... Transformer

Claims (4)

  Two switching elements are connected in series, and a high-side gate drive when a positive voltage is output from the low-side gate drive circuit, with the high-side switching element as the high-side switching element and the low-potential side as the low-side switching element. The circuit maintains 0V or outputs a negative voltage, and when the output from the low-side gate drive circuit outputs 0V or a negative voltage, the high-side gate drive circuit outputs a positive voltage. In the power conversion circuit where the side and low side gate drive circuits are controlled, connect the drain and source of the Nch normally-on auxiliary switching element between the gate and source of the high side and low side switching elements, and connect the primary side of the transformer Connected to the output of the gate drive circuit, a positive gate drive voltage is output from the gate drive circuit. The secondary side of the transformer should be connected between the gate and source of the Nch normally-on switching element so that a negative voltage pulse is applied between the gate and source of the Nch normally-on switching element. A characteristic gate drive circuit.   The gate drive circuit according to claim 1, wherein the transformer is an air-core transformer.   The gate drive circuit according to claim 1 or 2, wherein the gate drive circuit outputs a positive voltage of 0V. The high side gate driving circuit, the low side gate driving circuit, the transformer, the Nch normally-on type auxiliary switching element , the high side switching element , and the low side switching element in the gate driving circuit according to any one of claims 1 to 3 are the same. A power semiconductor module characterized by being enclosed in a package.