JP5299062B2 - Method for simulating transient characteristics of IGBT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple IGBT (Insulated Gate Bipolar Transistor) transient characteristics simulation circuit that accurately simulates the transient characteristics of an IGBT. <P>SOLUTION: The IGBT transient characteristics simulation circuit comprises an Nch MOSFET model 11, a PNP BJT model 12, and a current-controlled current source F1 (13). The current-controlled current source F1 (13) receives the input of a current flowing in a collector electrode C2 of the PNP BJT model 12 and simulates a tail current by outputting a certain current between the drain electrode D1 and the source electrode S1 of the Nch MOSFET model 11, thereby providing simulation effects on the basis of actual measurement results. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention is based on a simulator such as a SPICE (Simulation Program with Integrated Circuit Emphasis) of a semiconductor element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor). The present invention relates to a simple IGBT transient characteristic simulation circuit (IGBT model) that can simulate suitable transient characteristics in simulation.

FIG. 4 is a diagram showing a basic structure of the IGBT. FIG. 5 is a diagram showing a circuit configuration of a commonly used IGBT equivalent circuit. As shown in FIG. 4, the IGBT is a composite element of an Nch type MOSFET 41 and a PNP type BJT (Bipolar Junction Transistor) 42. In the Nch-type MOSFET 41, the drain is connected to the base of the PNP-type BJT42 in the N-layer, the source is connected to the emitter terminal E of the IGBT in the N + layer, and the gate is connected to the gate terminal G of the IGBT. The layer is connected to the collector terminal C of the IGBT, the collector is connected to the emitter terminal E of the IGBT in the P layer, and the base is connected to the drain of the Nch-type MOSFET in the N− layer. This is shown by an equivalent circuit in FIG.

  In the circuit configuration of the equivalent circuit shown in FIG. 5, when the transient characteristics of the IGBT are simulated, the turn-on characteristics can be expressed, but the turn-off characteristics cannot be expressed. This is because the tail current, which is a characteristic unique to IGBTs, cannot be expressed.

  FIG. 6 is a diagram showing an IGBT turn-off waveform. As shown in FIG. 6, the simulation waveform (broken line shown in FIG. 6) of the model consisting of MOSFET + BJT shown in FIG. 5 does not take into account the tail current in contrast to the actually measured waveform of IGBT (solid line shown in FIG. 6). Only the waveforms are different.

  As will be described in FIG. 7, the N-layer is filled with excess carriers when the IGBT is turned on (high injection state), and the accumulated minority carriers are swept away from the N-layer when the turn is turned off. Or it is thought to recombine with the electron pair and disappear. FIG. 7 is a diagram showing the operation of the carriers inside the IGBT when the turn is ON and OFF. That is, FIG. 7 (a) shows a turn-on state, and FIG. 7 (b) shows a state immediately after the turn-off. In the turn-off process, the current that flows for hole processing is called tail current.

  In order to solve the problem that the tail current of the MOSFET + BJT model shown in FIG. 5 cannot be expressed, various models have been proposed. Among the models proposed so far, the model disclosed in the following Patent Document 1 is obtained by adding a tail current generating circuit 80 between the base and collector of the BJT 42 in the IGBT as shown in FIG. Express an OFF waveform. This tail current generation circuit 80 is composed of four blocks: a current detection circuit (block A) 81, a temporal change detection circuit (block B) 82, a time width control circuit (block C) 83, and an amplification circuit (block D) 84. Is done. The current detection circuit (block A) 81 is the current detection voltage source V1 and the current control type voltage source E1, and the aging detection circuit (block B) 82 is the capacitor C3, the resistor R1, the detection diode D1, and the time width. The control circuit (block C) 83 includes a resistor R2 and a capacitor C4, and the amplifier circuit (block D) 84 includes a voltage control type voltage source E2, resistors R3 and R4, and an NPN type BJT Q1. By adjusting the parameters of the elements in each of these circuit blocks, a tail current that simulates actual measurement is generated, and an IGBT turn-off waveform is expressed.

JP-A-8-137978 (see paragraphs 0026-0030, FIG. 2)

  In the general IGBT model (IGBT transient characteristics simulation circuit) shown in FIG. 5, when the transient characteristics are simulated, the turn-on characteristics can be expressed, but the turn-off characteristics cannot reproduce the tail current, which is a characteristic peculiar to IGBTs. There was a problem that actual characteristics could not be expressed.

In order to solve this problem, the IGBT model (IGBT transient characteristics simulation circuit) shown in FIG. 8 disclosed in Patent Document 1 adds a tail current generation circuit 80 between the base and collector of the PNP type BJT 42 in the IGBT. The tail current at turn-off is expressed. The tail current generating circuit 80 is composed of four blocks: a current detecting circuit 81, a time-dependent change detecting circuit 82, a time width control circuit 83, and an amplifier circuit 84. When an IGBT model is actually created, element parameters in each circuit block in the tail current generation circuit 80 are determined from the IGBT measurement results. Since the number of elements is large, it takes a lot of time to determine the parameters of the elements in each circuit block in the tail current generating circuit. In other words, because the tail current generation circuit is complex and the number of elements in the circuit is large, the conventional IGBT model can represent the tail current at turn-off, but in order to determine each parameter and create a practical model There was a problem that it took a lot of time.

  Therefore, an object of the present invention is to provide a simple IGBT transient characteristic simulation circuit capable of accurately simulating the transient characteristic of an IGBT.

The invention according to claim 1 is a method of simulating the transient characteristics of an IGBT having a gate terminal, an emitter terminal, and a collector terminal, wherein the source electrode and the bulk electrode are the emitter terminal, the gate electrode is the gate terminal, and the drain electrode is Nch type MOSFET model connected to base electrode of PNP type BJT model, PNP type BJT model with collector electrode connected to the emitter terminal, emitter electrode connected to the collector terminal, and collector terminal of PNP type BJT model A current-controlled current source that simulates a tail current by outputting a predetermined current between the drain electrode and the source electrode of the Nch-type MOSFET model, and the current-controlled current source has a resistance , A capacitor, a first current-controlled current source that causes the same current as that flowing through the collector electrode of the PNP-type BJT model to flow across the resistor, And a second current control type current source for passing the same current as the current flowing through the capacitor between the drain electrode and the source electrode of the Nch type MOSFET model, the first current control type current source, and the resistor In addition, the transient characteristics of the IGBT are simulated using an IGBT transient characteristics simulation circuit in which the capacitor is connected in parallel .

The invention according to claim 2 is the method of simulating the transient characteristics of the IGBT according to claim 1, wherein the transient characteristics simulation circuit of the IGBT further calculates a voltage between the gate electrode and the drain electrode of the Nch MOSFET model. the gate electrode of the voltage-controlled current source the Nch-type MOSFET model as input - Bei example between the drain electrode, a gate electrode of the Nch-type MOSFET model - is characterized that you control the drain electrode capacitance.

  According to the present invention, the tail current can be expressed by adding a current control type current source between the drain electrode and the source electrode of the Nch type MOSFET model in the IGBT model, and the operation at the time of turn-off can be realized by simulation.

In addition, a first current-controlled current source that causes the same current as the current flowing through the resistor, the capacitor, and the collector electrode of the PNP-type BJT model to flow across the resistor, and the same current as the current that flows through the capacitor as the Nch-type MOSFET model A second current-controlled current source that flows between the drain electrode and the source electrode of the first current-controlled current source, the resistor, and the capacitor connected in parallel , can simulate the tail current in charging and discharging Denden flow of charge stored, it is possible in a short time by determining the parameters of easily IGBT model.

  In addition, by adding a voltage-controlled current source between the gate electrode and drain electrode of the Nch MOSFET model, it is possible to adjust the capacitance between the gate electrode and drain electrode, which has a large effect when switching MOSFETs and IGBTs. It is possible to reduce the difference from the result.

It is a figure which shows the circuit structure of the IGBT model concerning the 1st Embodiment of this invention. It is a figure which shows the circuit structure of the IGBT model concerning the 2nd Embodiment of this invention. It is a figure which shows the circuit structure of the IGBT model concerning the 3rd Embodiment of this invention. It is a figure which shows the basic structure of IGBT. It is a figure which shows the circuit structure of a general IGBT model. It is a figure which shows the turn-off waveform of IGBT. It is a figure which shows the operation | movement of the carrier inside IGBT at the time of turn ON and OFF. It is a figure which shows the circuit structure of the conventional IGBT model.

Hereinafter, embodiments of the present invention will be described in detail.
[Embodiment 1]
FIG. 1 is a diagram showing a circuit configuration of an IGBT model (an IGBT transient characteristic simulation circuit) according to the first embodiment of the present invention. The IGBT model shown in FIG. 1A has a gate terminal G, an emitter terminal E, and a collector terminal C in order to simulate operation as an IGBT.

  In the Nch MOSFET model 11, the source electrode S1 and the bulk electrode B1 are connected to the emitter terminal E, the drain electrode D1 is connected to the base electrode B2 of the PNP BJT model 12, and the gate electrode G1 is connected to the gate terminal G. Yes.

  In the PNP type BJT model 12, the collector electrode C2 is connected to the emitter terminal E, the emitter electrode E2 is connected to the collector terminal C, and the base electrode B2 is connected to the drain electrode D1 of the Nch type MOSFET model 11.

The current control type current source F1 (13) is connected between the drain electrode D1 and the source electrode S1 of the Nch type MOSFET model 11. The current-controlled current source F1 (13) receives the current flowing through the collector electrode C2 of the PNP-type BJT model 12 as input, detects the turn-on / turn-off state of the IGBT, and receives it, the Nch-type MOSFET model The tail current can be simulated by outputting a predetermined current between the eleven drain electrodes D1 and the source electrode S1, and the simulation result can be matched with the actual measurement with high accuracy as shown in FIG. In FIG. 1 (b), the measured waveform of the IGBT is shown by a thick solid line, the simulation waveform of the IGBT model according to the first embodiment of the present invention is shown by a thin solid line, and the first embodiment of the present invention The simulation waveform of the IGBT model in which the above-described current control type current source F1 (13) is omitted from the IGBT model according to FIG.

As described above, in the IGBT model according to the first embodiment of the present invention, the current control type current source 13 that outputs a predetermined current for simulating the tail current between the drain electrode and the source electrode of the Nch type MOSFET model 11 is used. By making the input current the current value that flows through the collector terminal of the BJT model 12 in the IGBT, it is possible to accurately determine the turn-on and turn-off states of the IGBT and express the state of excess carriers accumulated in the N-layer It is a thing.
[Embodiment 2]
FIG. 2 is a diagram showing a circuit configuration of an IGBT model (an IGBT transient characteristic simulation circuit) according to the second embodiment of the present invention. This IGBT model has a gate terminal G, an emitter terminal E, and a collector terminal C as shown in FIG.

  In the Nch MOSFET model 11, the source electrode S1 and the bulk electrode B1 are connected to the emitter terminal E, the drain electrode D1 is connected to the base electrode B2 of the PNP BJT model 12, and the gate electrode G1 is connected to the gate terminal G. .

  In the PNP type BJT model 12, the collector electrode C2 is connected to the emitter terminal E, the emitter electrode E2 is connected to the collector terminal C, and the base electrode B2 is connected to the drain electrode D1 of the Nch type MOSFET model 11.

As a specific configuration of the current control type current source F1 shown in FIG. 1, the first current control type current source F2 (14), the second current control type current source F3 (17), and the first A circuit is provided in which a current-controlled current source F2 (14), a resistor R5 (15), and a capacitor C5 (16) are connected in parallel. The input current of the first current control type current source F2 (14) is a current flowing through the collector electrode C2 of the PNP type BJT model 12. As current flows from the first current control type current source F2 (14), electric charge is accumulated in the capacitor C5 (16), and the charge / discharge current is supplied by the second current control type current source F3 (17). The tail current is simulated by flowing between the drain electrode D1 and the source electrode S1 of the Nch MOSFET model 11. By adjusting the parameters of the resistor R5 (15) and the capacitor C5 (16), the tail current can be simulated in a short time, and the simulation result can be matched with the actual measurement with high accuracy.
[Embodiment 3]
FIG. 3 is a diagram showing a circuit configuration of an IGBT model (an IGBT transient characteristic simulation circuit) according to the third embodiment of the present invention. The IGBT model according to the third embodiment of the present invention has the circuit configuration of the IGBT model according to the second embodiment shown in FIG. 2, and controls the voltage between the gate electrode G1 and the drain electrode D1 of the Nch type MOSFET model 11. This is a model to which a current source GV1 (18) is added. The IGBT model according to the third embodiment of the present invention is basically the same as the circuit configuration of the IGBT model according to the second embodiment shown in FIG. Only explained.

  The IGBT model according to the third embodiment of the present invention is a voltage control type current source GV1 (18) added to the circuit configuration of the IGBT model according to the second embodiment shown in FIG. By controlling the current flowing through the electrode D1, the capacitance between the gate electrode G1 and the drain electrode D1, which greatly affects the transient characteristics, is controlled. As a result, when the tail current is simulated, the difference from the actual measurement result can be further reduced, that is, the fitting accuracy can be improved.

11 Nch type MOSFET model
12 PNP BJT (Bipolar Junction Transistor) model
13 Current-controlled current source (F1)
14 First current-controlled current source (F2)
15 Resistance (R5)
16 capacity (C5)
17 Second current-controlled current source (F3)
18 Voltage controlled current source (GV1)
G Gate terminal
C Collector terminal
E Emitter terminal
G1 gate electrode
D1 Drain electrode
S1 Source electrode
B1 Bulk electrode
B2 Base electrode
C2 collector electrode
E2 Emitter electrode

Claims (2)

In a method of simulating the transient characteristics of an IGBT having a gate terminal, an emitter terminal, and a collector terminal,
An Nch type MOSFET model in which a source electrode and a bulk electrode are connected to the emitter terminal, a gate electrode is connected to the gate terminal, and a drain electrode is connected to a base electrode of a PNP type BJT model;
PNP type BJT model in which a collector electrode is connected to the emitter terminal, and an emitter electrode is connected to the collector terminal;
As an input the current flowing through the collector electrode of the PNP-type BJT model, the drain electrode of the Nch-type MOSFET model a predetermined current - e Bei and a current-controlled current source which simulates the tail current and output between the source electrode ,
The current-controlled current source is
A resistor, a capacitor, a first current-controlled current source that causes the same current as the current flowing through the collector electrode of the PNP-type BJT model to flow across the resistor, and the same current as the current that flows through the capacitor are the Nch-type MOSFET model A transient current simulation of an IGBT having a second current control type current source that flows between the drain electrode and the source electrode of the first current control type current source, the resistor, and the capacitor connected in parallel A method of simulating the transient characteristics of an IGBT using a circuit . The method of simulating the transient characteristics of the IGBT according to claim 1,
The IGBT transient characteristics simulation circuit further includes:
A voltage-controlled current source having a voltage between a gate electrode and a drain electrode of the Nch type MOSFET model as an input is provided between the gate electrode and the drain electrode of the Nch type MOSFET model, and the gate electrode and the drain electrode of the Nch type MOSFET model A method for simulating the transient characteristics of an IGBT, characterized by controlling the capacitance between the electrodes.