What is the EVAL-ADUM4135EBZ that improves the reliability of industrial motor control?

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Important things to improve the reliability of industrial motors

Control circuits that drive industrial motors must operate with high reliability even in harsh electrical environments. On the other hand, the voltage of controller-side ICs is becoming lower and lower, requiring a design that is more sensitive to electrical noise.

Here, we will mainly explain the functions of Analog Devices' ADUM4135 that improve the reliability of industrial motor control, so you can understand what kind of design philosophy is important. We will also introduce an environment for quickly evaluating the ADUM4135.

especially

I want to improve the reliability of motor control
I am designing an IGBT inverter circuit.
I am currently considering motor control design.
IGBT周辺回路について調査している

といった方にとって重要な情報です。

Harsh environment surrounding industrial motor control

Due to the demand for reducing the power consumption of industrial motors and the realization of lower costs around power switches, switching policies have become the mainstream solution for power inverters. On the other hand, high-power switching circuits generate noise, and the challenge is how to improve noise resistance without compromising switching speed.

In addition, in order to control the motor with high precision, it is necessary to send feedback signals from the motor to the circuit to the controller side.
However, due to the miniaturization of semiconductor processes, the voltage of the IC on the controller side is becoming lower, and the core voltage of the microprocessor that controls it is increasing to 3.3V.

For this reason, it is common to isolate the power inverter circuit and control circuit with an isolator.

The commonly employed isolator is an optocoupler, but it also has its problems.
A standard photocoupler is

数ms程度の伝搬遅延
温度条件に依存
使用年数による変化

I also have other problems.

Three points to improve motor control reliability

1. Insulation measures on the motor driver side and control circuit side

The inverters that drive industrial motors generate noise and place a heavy load on the microcontrollers in the control circuits, which are becoming increasingly low-voltage. In particular, the reliability of feedback signals is important for driving motors with high performance.

Therefore, as a noise countermeasure, it is necessary to insulate the inverter side and the control circuit side. Traditionally, photocouplers have been used as a safe isolation method. However, the performance of photocouplers at the system level is affected by propagation delay, temperature conditions, and age of use, so countermeasures are required.

Analog Devices' ADUM4135 is a digital isolator featuring iCoupler® technology.

iCoupler® technology uses a chip-scale transformer to achieve high insulation performance and high speed, rather than using LEDs or photodiodes like photocouplers.

As a result, we have achieved low cost and high-speed operation that cannot be covered by standard photocouplers.

Chip-scale transformers also enable isolated communication of control information between high-voltage and low-voltage regions of the chip. Information about the state of the chip can be read out from a dedicated output, allowing the microprocessor in the control circuit to check the status on the inverter side.

2. 寄生素子にる誤動作対策

When driving an IGBT with an isolator, it is generally connected to the gates of two IGBTs on the high side and low side.

When the high-side IGBT is turned on, the gate voltage of the low-side IGBT increases through parasitic capacitance and gate resistance due to the emitter potential of the low-side IGBT and the collector gate of the low-side IGBT, and when it exceeds the threshold of the low-side IGBT, it causes an arm short circuit. A malfunction will occur.

The measures to prevent this malfunction are as follows:

ミラー容量が小さい素子を選択する
ハイドパワー素子のゲート抵抗を大きくし、dv/dtを小さくする
ローサイドパワー素子のゲート抵抗を小さくする

It is necessary to devise countermeasures such as these, but it also takes time to evaluate.

Analog Devices' ADUM4135 is equipped with an internal Miller clamp circuit as a countermeasure against parasitic elements.
Therefore, arm short circuits caused by parasitic elements can be avoided.

3. 短絡による不具合対策

When using IGBTs, you also need to pay attention to their short-circuit tolerance. If a short circuit occurs on the output side, there is a risk of damage to the IGBT. This is because IGBTs have low on-resistance, so excessive current flows even for a short time.

For example, if there is a short circuit to the inductor, motor windings, power supply, or ground bus, excessive current can flow into the IGBT and damage it.

Therefore, measures such as load circuits are required to protect IGBTs.

Analog Devices' digital isolator "ADUM4135" is equipped with an internal circuit that detects non-saturation conditions.

If the IGBT is short-circuited and becomes unsaturated, the ADUM4135 detects the unsaturated state in less than 2 μs and turns off the IGBT.

At this time, the ADUM4135 can notify the microprocessor of the situation through the RESET pin, allowing system-wide control.

The above three measures are important, but next we will introduce a solution provided by Analog Devices.

ADUM4135をすぐに評価できるボード「EVAL-ADuM4135EBZ」とは？

If you would like to evaluate Analog Devices' digital isolator "ADUM4135", an evaluation board "EVAL-ADuM4135EBZ" is available for immediate evaluation.

The EVAL-ADuM4135EBZ has a fit print on the board so that you can immediately evaluate your IGBTs and MOSFETs.

アイソレーター、IGBTドライブ確認
不飽和検出
ミラークランプの動作確認

This makes it easy to evaluate.

This evaluation board "EVAL-ADuM4135EBZ" can be evaluated by connecting it to Analog Devices' microprocessor evaluation board "ADSP-CM408F EZ-Board".