How to Check an IGBT Using a Multimeter

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Have you heard of Insulated Gate Bipolar Transistor or IGBT? 

It is a 3-terminal semiconductor switching device utilized for fast switching with high efficiency in most electronic devices. Such tools are widely seen in amplifiers for processing or switching complicated wave patterns with pulse width modulation or PWM. 

It combines the simple gate-drive qualities of the MOSFET and the low-saturation and high-current voltage capability of the bipolar transistor in one device. You see, certain IGBT datasheets and application notes from company manufacturers offer plenty of practical details. However, navigating this topic on your own could be frustrating and complicated, especially for beginner circuit designers.

To make it simple for you, an IGBT is a component utilized to power most vehicles and home appliances. Do you believe your appliance is short-circuiting? It will help if you do a test to identify if the IGBT is the culprit to that issue.

The question now is: how do you test your IGBT? What is the best tool you can use? 

If done successfully and correctly, that could save you from buying a new appliance and replacing the malfunctioning IGBT. 

Before we dig deeper into that topic, let’s first understand how IGBT works and its structure.

Where Do You Normally Use an IGBT? 

The IGBT is ideal for many different purposes in power electronics, particularly in PWM servo and three-phase drives that need high dynamic range control and low noise. Did you know it can also be utilized in UPS (Uninterruptible Power Supplies), SMPS (Switched-Mode Power Supplies), and other power circuits that need high switch repetition rates? 

In short, IGBT accelerated efficiency and dynamic performance and lowered the level of audible noise. It’s similarly suitable in resonant-mode converter circuits. Augmented IGBT is also accessible for both low switching loss and low conduction loss. 

What are the Benefits of Using IGBT? 

You will find a few reasons why using IGBT is much more desirable instead of a BJT and Power MOSFET. 

  • It has a wide SOA. IGBT has excellent current conduction capability, unlike a bipolar transistor. It also has top-notch forward and reverses blocking skills.
  • IGBT has low driving power and a straightforward drive circuit because of its input MOS structure. Hence, it can be effortlessly regulated, unlike current control devices (such as BJT, thyristor) in high current and high voltage applications.
  • Ultimately, an IGBT has a low on-state voltage drop because of its conductivity modulation and has excellent on-state current density. Therefore, a smaller chip size is most likely possible, and the cost can be drastically lowered. 

You see, the IGBT is ideal for scaling up the blocking voltage capability. When we talk about Power MOSFET, the on-resistance accelerates suddenly with the breakdown voltage. That is because of the rise in the resistivity and thickness of the drift area needed to support the high operating voltage.

With that being said, the expansion of high current Power MOSFET with a high-blocking voltage rating is typically prevented. On the contrary, for the IGBT, the drift region resistance is substantially lowered by the high concentration of injected minority carriers throughout on-state current conduction. 

Moreover, the forward drop from the drift region becomes reliant upon its thickness and autonomous of its initial resistivity.  

The Importance of Testing an IGBT

You must pay very close attention and care when you are doing a test with your IGBT. Remember that applying too much voltage or heat to this component could pose a big risk and cause permanent damage to the appliance. 

To guide you in testing your IGBT accurately and correctly, just follow these steps below: 

  1. Unplug your appliance first. The last thing you’d like is to be electrocuted, right? 
  1. Find the IGBT in the circuitry. Take this step very seriously and always be careful. The IGBT is a white or black circuit brick with two to six connections on top and two connections on the side. Remember that the location on the circuit board will differ by the appliance.
  1. Detach the IGBT from your appliance. You can do that by removing the four screws at the corners. To guarantee safety, do not execute any test actions until all electronic connections have been removed from the IGBT. 
  1. Always check the connection of the protection diode using your multimeter in diode test mode. 
  1. Grab the red lead of the meter and plug it to the black lead of your IGBT. That’s the emitter terminal. The IGBT terminal features a functional protection diode if the reading on the DVM is between .2 and .8. 
  1. Grab your multimeter and set it in resistance mode. Plug it to the IGBT’s emitter (the black lead). Does your device show anything but an infinite reading? It’s a clear sign you may have a shorted IGBT. That’s also referred to as a gate-oxide test. 
  1. Take the IGBT tester to test its functionality by attaching it to the IGBT’s collector, gate, and emitter terminals. The gate is located on the side of the device, close to the emitter. Meanwhile, the collection is located on the opposite side. That should be all three leads on your device.
  1. Hit the test button on your digital multimeter and see if the conduction light is turned on. If it does not have light, your IGBT might be defective. 
  1. You can switch the emitter and collector leads to be certain the protection diode is not obstructing. But we recommend that you don’t hit the test button. The IGBT has a functional production diode if converting the leads causes the conduction light to turn on. 

Final Thoughts

As you can see, checking and testing an IGBT with a digital multimeter does not need to be complicated and challenging, especially for a beginner like you. Just follow the essential steps mentioned in this post, and you are good to go.

We hope you learn something useful and informative in this post. Feel free to share this to others who are having the same concern as you.

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