Is it possible to make an IGBT to work at duty cycles up to 100%?

Thread Starter

yogece

Joined May 26, 2013
9
I am designing an IGBT based chopper with single Low side switching IGBT (chosen low side switching because ease of driving the IGBT.)
IGBT chopper.jpg
There are plenty of resources available for SMPS (buck, boost, buck-boost,) PFC chopper, inverters, welding power sources, UPS and motor control applications. I presume all those applications work under duty cycles up to 50% and for motor applications it may go up to 95% (only during the peak of the SPWM signal) but none of the applications mentioned made it to work continuously in the duty cycle range of 90% or above.

I googled a lot and read the application notes, datasheets and reference designs of various IGBT/MOSFET manufacturers such as Infineon, ST, Semikron, Vishay, ROHM, Fuji, Mitubhishi, Hitachi, Toshiba, IXYS, ABB, Renesas, TI, NXP, Nexperia.

Some of the applications listed below which uses IGBT close to 100% duty cycle operation.

1. HVDC circuit breaker uses a hybrid approach. During operation the current will always flow through the bypass branch which has a mechanical circuit breaker and during the interruption of the current it will be allowed to pass through the IGBT, this application doesn’t help me to understand about the 100% operation of the IGBT.

2. Another application which uses the duty cycle up to 100% is separately excited DC motor which can use IGBT, but I couldn’t find any reference for the implementation using IGBT and there are plenty of resources available for thyristor based choppers and simulation of the same.

3. The DC electronic load which uses the MOSFET in DC operation and couldn’t find reference for high power electronics load using IGBT. Many of the manufacturers of IGBT mentioned not to operate the devices in the linear region.

I am designing an IGBT based chopper with single Low side switching IGBT (chosen low side switching because ease of driving the IGBT.)

There are plenty of resources available for SMPS (buck, boost, buck-boost,) PFC chopper, inverters, welding power sources, UPS and motor control applications. I presume all those applications work under duty cycles up to 50% and for motor applications it may go up to 95% (only during the peak of the SPWM signal) but none of the applications mentioned made it to work continuously in the duty cycle range of 90% or above.

I googled a lot and read the application notes, datasheets and reference designs of various IGBT/MOSFET manufacturers such as Infineon, ST, Semikron, Vishay, ROHM, Fuji, Mitubhishi, Hitachi, Toshiba, IXYS, ABB, Renesas, TI, NXP, Nexperia.

Some of the applications listed below which uses IGBT close to 100% duty cycle operation.

1. HVDC circuit breaker uses a hybrid approach. During operation the current will always flow through the bypass branch which has a mechanical circuit breaker and during the interruption of the current it will be allowed to pass through the IGBT, this application doesn’t help me to understand about the 100% operation of the IGBT.

2. Another application which uses the duty cycle up to 100% is separately excited DC motor which can use IGBT, but I couldn’t find any reference for the implementation using IGBT and there are plenty of resources available for thyristor based choppers and simulation of the same.

3. The DC electronic load which uses the MOSFET in DC operation and couldn’t find reference for high power electronics load using IGBT. Many of the manufacturers of IGBT mentioned not to operate the devices in the linear region.

I am intending to use IGBT modules of 1200V/400A (semikron SKM400GB125D half bridge module.) For the proof of concept I used discrete IGBT (IRFGP50B60PD) and drove it up to dutycycle of 50% @ 490Hz and it worked perfectly. The high power IGBT modules the manufacturer doesn’t provide FBSOA but they provide RBSOA and SCSOA details alone. For the short overload conditions recommend to refer the transient thermal impedance characteristics and for the steady state pulsing operations recommends to look at RthJ-C of IGBT & diode.

Many manufacturers have simulators which allows to simulate the electrical and thermal details of our circuit, but for which I couldn’t get some pointers regarding how far the simulation and bench test correlates (correlation of simulation Vs implementation) Semikron Semisel, Infineon (uses PLECS,) Fuji electric. By the simulator, we can estimate the losses of the switch (switching loss and conduction loss) and junction temperatures.

For the following questions I am expecting some inputs from the community:

1. Is it possible to operate IGBT up to 100% duty cycle? I couldn’t find many application references for IGBTs, which works in the duty cycle close to 100%. The question is similar to https://www.researchgate.net/post/Can_the_IGBT_MOSFET_turn_on_all_time_long_just_as_a_diode

2. Need some information regarding how far the simulation and bench test correlates (correlation of simulation Vs implementation.)

3. Reference designs or some resources for DC chopper using IGBT/MOSFET.

4. Suggest me some technical forum and resources dedicated to power electronics.
 

jpanhalt

Joined Jan 18, 2008
7,887
@yogece , Welcome to AAC.

Yes, it is possible to operate IGBT and mosfets at 100%. The limitation you may face is with your driver. Will your driver produce DC at the required voltage?

BTW, it seems a large portion of your post is duplicated. Did you accidentally paste twice?
 

Thread Starter

yogece

Joined May 26, 2013
9
@yogece , Welcome to AAC.



Yes, it is possible to operate IGBT and mosfets at 100%. The limitation you may face is with your driver. Will your driver produce DC at the required voltage?

BTW, it seems a large portion of your post is duplicated. Did you accidentally paste twice?
Thanks for your Reply!!

I don't have any problem with the gate driver.It is not boot strapped type driver such as IR2110 its having a dedicated isolated power for driver.
I use Semikron Skyper 32 R the problem is only with the IGBT; no manufacturer suggests to use IGBT/MOSFET for longer time with duty cycle close to 100%. If you can provide some resources regarding this would be more helpful to me. Because i have been looking at various resources for a month.

yeah i have wrongly pasted twice and i don't find option to edit the thread, but i could edit this particular reply
 
Last edited:

jpanhalt

Joined Jan 18, 2008
7,887
...no manufacturer suggests to use IGBT/MOSFET for longer time with duty cycle close to 100%.
That is not true. While such devices are often used for control using PWM or similar, they are also used for on/off applications. Here is one example: https://www.onsemi.com/pub/Collateral/AND9093-D.PDF

Of course, an on/off switch for a load may use a P-channel device for convenience, but that doesn't change the basic idea. You do need to heed the continuous ratings, including limitations on the package. That is, the device's junction may have a much higher current rating and produce more heat then the device's package will allow in continuous operation.
 

Thread Starter

yogece

Joined May 26, 2013
9
That is not true. While such devices are often used for control using PWM or similar, they are also used for on/off applications. Here is one example: https://www.onsemi.com/pub/Collateral/AND9093-D.PDF

Of course, an on/off switch for a load may use a P-channel device for convenience, but that doesn't change the basic idea. You do need to heed the continuous ratings, including limitations on the package. That is, the device's junction may have a much higher current rating and produce more heat then the device's package will allow in continuous operation.
I didn't say 100% duty cycle operation(Continuous) of MOSFET not at all possible because very few manufacturer have mentioned SOA for DC operation of MOSFET but that allows very low power dissipation on the MOSFET. The linear mode of operation is also limited by the Tj of MOSFET and spirito effect.If the SOA for DC operation of MOSFET isnt mentioned in the data sheet means we can interpolate it and find the DC SOA.

As you have mentioned many references are available for DC load switch (Which uses P-MOSFET in high side).

As i mentioned in the detailed introduction to my problem in the high power IGBT modules such as Semikron SKM400GB125D which doesn't have FBSOA characteristics in terms of various duty Vs current. The manufacturer don't say anything about the duty cycle limitation but they suggest me to have an eye on Tj of IGBT and diode.

I am looking some pointers for high power IGBT modules which works in the duty cycles close to 100% or it would be fine if it is up to 98%
 
Last edited:

TeeKay6

Joined Apr 20, 2019
382
yeah that means DC.
It would be fine for me duty up to 98%
@yogece
It's easy to achieve ~100% duty-cycle. For example, let "on" time be 1hour and "off" time be 0.001s. (That is a joke.) My point is, at what frequency must you operate in your application? What min "off" time must you use? What max "on" time must you use? Will your load be resistive or complex?
 

Thread Starter

yogece

Joined May 26, 2013
9
@yogece
It's easy to achieve ~100% duty-cycle. For example, let "on" time be 1hour and "off" time be 0.001s. (That is a joke.) My point is, at what frequency must you operate in your application? What min "off" time must you use? What max "on" time must you use? Will your load be resistive or complex?
Thanks for the Joke:)
"on time" 30 minutes "off time" 1 minute
Load is purely resistive.
I am looking for some resources for example Design Considerations for using IGBT modules in Inverters and Drives(http://www.irf.com/technical-info/appnotes/an-1202.pdf)
 

Thread Starter

yogece

Joined May 26, 2013
9
You can Operate MOSFETs and IGBT at 100%. The only limitation you face is with your driver.
Hi thanks for the Reply!!
I don't have any issues with the driver.I have isolated supply IGBT driver Semikron SKYPER 32R.
The issue is only with the IGBT module.

I couldn't find application notes or some resources of High power IGBT module which is used for the applications duty cycle close to 100%.
it would be helpful if you could share links of resources.
 

jpanhalt

Joined Jan 18, 2008
7,887
Hi thanks for the Reply!!
I don't have any issues with the driver.I have isolated supply IGBT driver Semikron SKYPER 32R.
The issue is only with the IGBT module.

I couldn't find application notes or some resources of High power IGBT module which is used for the applications duty cycle close to 100%.
it would be helpful if you could share links of resources.
We seem to be going in a circle. Your initial question asks, "Is it possible to make an IGBT to work at duty cycles up to 100%?" That has been answered, but it seems that what you really want is a SOA (safe operating area) graph for a particular device. While some manufacturers , including Semikron provide such charts, in this instance, that apparently is not the case. However, apropos your original question, Semikron AN1501 (about water cooled heatsink) describes testing under continuous on conditions.

1) Have you found SOA charts that go to >90% on? If so, what happens when you extrapolate them to 100%?
2) Can you calculate points on the SOA charts using the data in the datasheet? I suspect the upper limits are mostly thermal.


 

Thread Starter

yogece

Joined May 26, 2013
9
We seem to be going in a circle. Your initial question asks, "Is it possible to make an IGBT to work at duty cycles up to 100%?" That has been answered, but it seems that what you really want is a SOA (safe operating area) graph for a particular device. While some manufacturers , including Semikron provide such charts, in this instance, that apparently is not the case. However, apropos your original question, Semikron AN1501 (about water cooled heatsink) describes testing under continuous on conditions.

1) Have you found SOA charts that go to >90% on? If so, what happens when you extrapolate them to 100%?
2) Can you calculate points on the SOA charts using the data in the datasheet? I suspect the upper limits are mostly thermal.

answer to your questions
1)SOA isn't available in for IGBT modules(I confirmed by the manufacturer Semikron and Infineon) for your reference i am attaching a clip from Semikron Applications Manual (Page number:181)
upload_2019-9-13_15-13-42.png

2) Yeah. As you rightly said the upper limit is thermal.

But my requirements are,

1. Is it possible to operate IGBT up to 100% duty cycle? I couldn’t find many application references for IGBTs but many resources are available for MOSFETs DC and linear Mode operation , which works in the duty cycle close to 100%. The question is similar to https://www.researchgate.net/post/Can_the_IGBT_MOSFET_turn_on_all_time_long_just_as_a_diode

2. Need some information regarding how far the simulation and bench test correlates (correlation of simulation Vs implementation.)

3. Reference designs or some resources for DC chopper using IGBT/MOSFET.

4. Suggest me some technical forum and resources dedicated to power electronics.
 

Uilnaydar

Joined Jan 30, 2008
118
100% PWM is DC. Just look at the RDSon of the device (max value), apply I^2R and ensure you don't dissipate too much power....

For 98% duty cycle, you just need to make sure the driver can turn the IGBT completely off and on or you are operating in the linear region.

If your period is minutes, like I saw in a post, then you are basically operating DC.
 

Thread Starter

yogece

Joined May 26, 2013
9
Doesn't that make your need of 100% null? Don't choppers have both on and off times?
choppers does have on and off. The output voltage of chopper is Vo=D*Vin i.e (Duty cycle)*(Vin)
if we want V0=Vin then D=1
if we need V0=Vin*0.5 then D=0.5
if i need to change the output voltage then the D should be changed
 

Thread Starter

yogece

Joined May 26, 2013
9
100% PWM is DC. Just look at the RDSon of the device (max value), apply I^2R and ensure you don't dissipate too much power....

For 98% duty cycle, you just need to make sure the driver can turn the IGBT completely off and on or you are operating in the linear region.

If your period is minutes, like I saw in a post, then you are basically operating DC.
As you rightly mentioned have to look at the turn-on&turn-off waveform if those over laps each other then IGBT would operate in linear mode.

The period of the switching frequency isn't in minutes(if the duty cycle is exactly 100% then the period will be in minutes). In H-bridge configuration the polarity changing time will be in minutes
 

BobTPH

Joined Jun 5, 2013
2,023
I really cannot imagine what your confusion is. The IGBT can be used at 100% duty cycle, as long as max power dissipation is not exceeded. That is all there is to it.

I think you are talking about the fact that you cannot have 100% duty cycle in a high side driver using bootstrapping. But that does not apply to your use case.

Bob
 

Alec_t

Joined Sep 17, 2013
10,359
Is your IGBT a high-side switch or a low-side one? A common driver arrangement for high-side switching involves a bootstrap circuit. Such a circuit would not operate properly with a 30 min on / 1 min off duty cycle.
 
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