JPH07222460A - Motor driving igbt module - Google Patents

Abstract

PURPOSE:To protect an IGBT module by a method wherein the IGBT module is composed of an FRD and an IGBT which has a larger energy strength for a unit area than the FRD and an energy produced by a sharp overvoltage caused by an avalanche breakdown is consumed by the IGBT. CONSTITUTION:A power supplied from a 3-phase or single-phase power supply 1 is converted into a DC power by a converter unit 2 and, further, inverted into an AC power by an inverter unit 3 to control a motor 4. An overvoltage protective circuit 5 detects the output voltage of the converter unit 2 and, if the detected voltage exceeds a specified value, stops the operation of the inverter unit 3 for protection. However, as the operation voltage of the overvoltage protective circuit 5 is set taking a surge voltage into consideration, there is a possibility of the overvoltage breakdown of a power device caused by an avalanche drop. Therefore, an IGBT module is composed of an FRD and an IGBT which has a lower breakdown strength than FRD and whose n<->-type layer has a larger thickness to obtain a power module whose heat radiation properties are improved and whose possibility of the breakdown is substantially reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IGBT which is a power element used in an inverter section of a motor control device, and an I.
An IG that creates a circuit that allows the current of an inductive load to flow when the GBT is off
IG composed of FRD added in anti-parallel to BT
It relates to a BT module.

[0002]

2. Description of the Related Art In recent years, the demand for inverter devices has been increasing with the development of power electronics technology. In the motor drive inverter device, an overvoltage is applied to the power element due to a sudden change in the rotation speed of the motor,
When the switching of the power element is suddenly turned off due to a short circuit on the load side of the inverter device, an excessive current with a steep rise is applied, and due to the current and wiring inductance, a voltage exceeding the withstand voltage is applied to the element and the power element is destroyed. There are various types of protection that are used to prevent this.

A conventional inverter circuit will be described below. FIG. 1 shows a conventional inverter circuit. 1 of FIG.
Is a three-phase or single-phase power source, 2 is a converter unit, 3 is an inverse conversion unit (hereinafter referred to as an inverter unit), and 4 is a motor. Here, the power switching elements forming the inverter unit 3 are transistors, MOSFETs (Meta).
l Oxide Semiconductor Fie
ld Effect Transistor), IGB
T (Insulated Gate Bipolar)
Transistor) and the like. Normal motor control is
The inverter unit is composed of two phases or three phases, and the unit in which the power switching element and the FRD are arranged in anti-parallel for each phase is connected in two series. And these elements are put together as one part. If the switching element is an IGBT, the one that combines it is IG
We call it BT module. Reference numeral 5 is an overvoltage protection circuit, which is a circuit for detecting the voltage across the converter section 2
It is a circuit that stops the inverter operation and protects it as soon as it exceeds the specified value.

[0004] Here, when the power supply input voltage is taken as an example an inverter device of AC200V, the converter unit 2 is converted into a DC voltage of 282V for 2 ^0.5 times the peak voltage. + And-side lines of the electrolytic capacitor of the converter unit 2,
That is, 282 V is applied to the line to the inverter section, and the power element is switching within that voltage. In the case of motor control, for example, during a rapid stop, a regenerative operation mode is entered, and the motor 4 acts as a generator to return electric power to the inverter unit 3, so that the line voltage of the inverter unit rises. When this line voltage exceeds the breakdown voltage of the power element (usually avalanche breakdown), the power element is destroyed.
In order to prevent this, the overvoltage protection circuit 5 is provided, and the AC20
About DC400V at 0V input, about DC at AC100V input
In many cases, overvoltage protection is set for the purpose of suspending the operation of the inverter when the voltage reaches 200V, but the withstand voltage of the element used at this time is 450 to 600V for 200V input,
In the case of 100V input, 250 to 300V is normally used. Here, there is a large difference between the breakdown voltage (for example, 600V) of the element and the overvoltage protection 400V, because the inductance l such as wiring is provided between the voltage detection point of the overvoltage protection circuit 5 and the element in the power module of the inverter unit 3. Existing and its rate of change of the current flowing in the module (dI
/ Dt), that is, a voltage of l × (dI / dt) is superimposed and applied to the power element, so that the inductance l
It is set in consideration of surge voltage caused by. Especially when the load short-circuit or when output short circuit is significant current flows, there is an example of protected all-off when it is detected the power element in overcurrent protection circuit, this time the motor from the current I _L and the motor controller Energy (1/2 × L × I _L ² ) determined by the inductance L of the wiring up to is returned to the inverter unit,
An excessive voltage is superimposed on the power element.

Taking an example of using an IGBT as a power element, the IGBT has a large short circuit current as compared with a conventional power transistor, and the surge voltage applied to the power element at the time of overcurrent protection is correspondingly large. Was higher, and overvoltage breakdown due to avalanche breakdown was more frequent.

Further, power transistors and MOSFETs
In itself, diodes can be configured in anti-parallel on the same chip, and the breakdown voltage of each element is the same in the power element section and the diode section. On the other hand, the IGBT cannot add a diode on another chip in anti-parallel because it cannot structurally form a diode by itself. Therefore, they have the degree of freedom to build up each other's pressure resistance separately.

Next, the current flowing through the power module used in the motor controller is the power switching element and the FR.
The probability of flowing to D is about the same, which is about 50%. In the case of one phase of the power module, since it is composed of two IGBTs and two FRDs, an average current of 25% flows through each element. When flowing to the FRD, the voltage drop in the forward direction is about 1 to 2V. On the other hand, IGBT
The voltage drop when ON is about 2 to 4V, and the loss generated in the FRD is half that of the IGBT with the same current. Further, the IGBT mostly bears the switching loss at the time of ON / OFF switching. Motor control devices that use IGBTs often use switching speeds of 10 KHz or higher due to their high-speed switching characteristics.
When switching at 0 KHz, the loss generated by the switching is about the same as the loss determined by the product of the voltage and the current. Here, if the loss generated by the product of the FRD current and voltage is 1, the loss of the IGBT is 2, and
The switching loss of BT is 3. Therefore, the IGBT
The total loss is about 5 times the loss of FRD. Therefore, in consideration of heat dissipation, the chip size of the element is required to be several times larger in the IGBT than in the FRD. Here, when the power element absorbs the energy due to the breakdown voltage overshoot due to avalanche breakdown, the IGBT has a larger chip size and a larger energy tolerance per unit area.
It can be seen that the probability of GBT breakdown is several times lower than that of FRD breakdown breakdown.

[0008]

As described above, when an excessive voltage is applied to the IGBT during load short-circuit protection or the like, which of the two will be destroyed if the withstand voltage of the IGBT and the withstand voltage of the FRD are not managed? Not sure, especially the FRD withstand voltage is I
If the breakdown voltage of the IGBT is higher than that, the voltage breakdown of the IGBT is likely to occur.

An object of the present invention is to solve the above problems and to provide a safe motor drive IGBT module which protects from load short-circuit breakdown, surge voltage breakdown and latch-up breakdown.

[0010]

In order to achieve the above object, the IGBT module of the present invention comprises an FRD and an IGBT having a larger energy withstanding capacity per unit area than the FRD.

[0011]

With this module configuration, the IGBT module is protected by consuming energy due to a steep overvoltage due to avalanche breakdown in the IGBT.

[0012]

EXAMPLES An example of the present invention will be described below.

Since the IGBT itself cannot structurally form a diode, the FRD of another chip is added in antiparallel. However, the IGBT has a breakdown voltage lower than that of the FRD, and the IGBT has an n-phase thickness. Thickened IGBT
By constructing the module, it is possible to supply a power module with less damage by improving heat dissipation.

[0014]

As described above, according to the IGBT module of the present invention, it is possible to reduce the frequency of element breakdown of the IGBT due to the breakdown voltage being exceeded, and it is possible to supply a stable inverter unit in motor control products.

[Brief description of drawings]

FIG. 1 is an inverter circuit diagram in the present invention and a conventional example.

[Explanation of symbols]

 1 Three-phase or single-phase power supply 2 Converter part 3 Inverter part 4 Motor 5 Overvoltage protection circuit

Claims (1)

[Claims] 1. A motor control device comprising: a switching element of an inverter section; and a flywheel diode (FRD) which forms a feedback circuit for the stored energy of an inductive load during switching, which is added in antiparallel to the switching element. An IGBT module for driving a motor, wherein the flywheel diode (FRD) has a withstand voltage higher than that of the IGBT.