# IGBT Power Supply..



## electrotech (Mar 11, 2013)

Hello all, new here. This place is full of amazing information, thanks for letter me lurk for a bit 

So while I have been dreaming of doing an electric car, at the moment I need some of the experts help with an IGBT(CM600HA) in a power supply, and this place seems to know their IGBTs. I have tried a few different ways to drive it with no luck. I have 24Volts on the Collector and am looking to regulate 12-21Volts on the Emitter, out. Are there any drive circuits out there worth taking a look at or building? Thanks all for the assistance, and an awesome forum..


----------



## Siwastaja (Aug 1, 2012)

For such low voltage, absolutely use MOSFETS. IGBTs are usable from about 100-200 volts and up. Otherwise, you will have horrible efficiency.

Google for switch mode power supply design. For non-isolating, you want to make a buck converter. You need an inductor, a diode, the switch (MOSFET) and a PWM controller chip. It can be a microcontroller and a simple piece of software, or a ready-made chip (for example, TL494 is a traditional one).


----------



## PStechPaul (May 1, 2012)

It appears that you may be using the IGBT as a linear emitter follower, which is quite unusual. You need to supply a voltage to the gate which is several volts above the emitter. I found one data sheet that showed the threshold to be about 7 or 8 volts. So to get 21 volts out you will need at least 28 volts to drive the gate. I looked for application notes using IGBTs in linear circuits, and I found very little. The following is an amplifier using complementary NPN and PNP IGBTs, but it is unclear how they might be able to approach the supply rails:
http://www.analog.com/static/import...tes/58052492001115525484056221917334AN211.pdf

You could use a DC-DC converter with a 9VDC output connected to the gate, and drive the 0V side. The output would start at about 2 volts and with a 24 VDC signal could be driven to at least 21 VDC. For a "poor man's gate drive" you could use a 9 VDC battery. The gate drive current is negligible for DC and low frequencies.

If you could put the load on the collector side to 24V you could easily adjust the output from zero to about 2 volts below the 24V rail due to VceSat. But you would need to use feedback and an active gate drive using several transistors or an op-amp and a reference.


----------



## electrotech (Mar 11, 2013)

Thank you for the help, I knew this forum was the place to go. I'd better get to the electric motorcycle I have been dreaming of soon..

You both are right, the IGBT is inefficient at that voltage, and using it as a linear voltage supply is quite unusual, but as is the application of same. I got the idea from a local CB guy who uses this odd power supply in his truck. It is quite the unusual device for sure, bridging 2 12 volt batteries via solenoids to make 24volts, then regulate the voltage out in a variable fashion to run crazy stupid powerful CB Amps. When you key up it disconnects these batteries from the vehicle charging system, then unkey it disconnects the amp, and reconnects the batteries for vehicle charging. Defiantly not my thing, but anything electronic fascinates me, so he let me run some tests on this thing today and it gave me ideas for an unnecessarily powerful power supply...

Here is a pic of the control board, and it appears you guys are hitting the nail on the head after I took some measurements today, and that rectangle device with its number scratched off on the bottom right has in the the area of 50volts DC coming out of it, with a 7805 voltage in. The gate drive voltage output is 26 volts, again nail on the head. The 8pin DIP IC also has numbers taken off, but is probably a generic IGBT driver. All very silly, but still cool.. Thanks again for the help..


----------



## Siwastaja (Aug 1, 2012)

AFAIK, most IGBT's are for switching. You need to at least derate it a lot.

So, use mosfets or BJTs, maybe driven by LM317 or similar, to make a linear PSU. But making a switch mode supply is not that difficult. If you plan to take more than maybe 10-20 watts out of it, go for switch mode (buck converter). You can easily achieve 95% efficiency.


----------



## PStechPaul (May 1, 2012)

You can get buck converter modules on eBay for pretty cheap, and you may be able to add external MOSFETs or IGBTs and larger inductors to get a lot more current:

http://www.ebay.com/itm/180954053737

http://www.ebay.com/itm/1pcs-DC-DC-...6-Power-Supply-Output-1-23V-30V-/251066005460

http://www.ebay.com/itm/8-40V-to-3-...008-Switching-High-Power-Supply-/390546298680

http://www.ebay.com/itm/DC-to-DC-Bu...-Power-Supply-Voltage-Regulator-/390546308136


----------



## subcooledheatpump (Mar 5, 2012)

Yeah IGBTs are completely useless for linear operation of any kind. Even at low voltages, they will just waste hundreds of watts. Get a PWM circuit, and a diode (since you are using CM600HA-24H which is a single module) and an inductor, make a buck converter. 

If you use a low switching frequency, even small gate drivers will work like HCPL-3120


----------



## electrotech (Mar 11, 2013)

Thank you all for the replys. 

I read over the spec sheet for the IC you suggested and also searched around. Just so we are thinking the same thing, do you have any example circuits you are thinking? What would be a good way to provide the PWM to this chip? Thanks again for the help..


----------



## PStechPaul (May 1, 2012)

I would use a PIC or maybe an Arduino to implement a simple buck converter. But you can also use switchmode power supply ICs to get the PWM. The tricky part will be sizing the inductor and closing the loop so that the PWM will adjust the output under a wide range of load conditions without oscillating or surging. The modules I listed from eBay already have most of what you need to implement this, so you just need to change the power components to suit your needs. You should also read some of the tutorials and other information that is available, such as:
http://www.smpstech.com/tutorial/t03top.htm
http://s4wsbox.com/?q=node/40
http://web.ing.puc.cl/~power/paperspdf/dixon/42a.pdf (more for EV regen braking with ultracaps)
http://www.semikron.com/skcompub/en/AN-8005_Techning_System.pdf (a bit technical, but good info on IGBTs)
http://www.denizyildirim.org/ee432/exp4.pdf (a simple experiment)
http://www.absoluteastronomy.com/topics/Buck_converter

The LM2596 is a good IC for this purpose, and you can get a complete unit for under $7:
http://www.amazon.com/Retailstore-LM2596-Adjustable-Supply-Converter/dp/B009HPB1OI/ref=sr_1_2

Here is a list of many converters including the LM2596:
http://www.onsemi.com/PowerSolutions/supportDoc.do?type=datasheets&category=149

Here is a datasheet. It shows a complete schematic and board layout for an adjustable 3A buck regulator. You can probably use the output to provide a PWM signal to the IGBT through an IGBT driver, but you will lose the current limiting of the IC:
http://www.onsemi.com/pub_link/Collateral/LM2596-D.PDF


----------



## electrotech (Mar 11, 2013)

Thank you again for the assistance, this is a cool learning project even though it's kinda pointless in nature.

So I managed to buy one of the circuits like you mentioned from ebay, it has the 2577 and the 2596 on one board with both sides being adjustable. I also got a used IGBT module like the one referenced above. I drove the gate with the 2577/2596 directly and it surprisingly worked like that odd power supply thing my buddy had. 

The gate was being driven with 28 Volts(Like you said...) and I was getting 21 Volts out, and was able to variable it down to about 13 volts. I threw a load tester on and it surprisingly worked well into the few hundred amp range. There was a large variance in the voltage however under load. I assume because the regulator circuit doesn't really know what the collector side is doing through the high impedance of the gate, and all the losses itself. 

I am wondering if an actual IGBT driver circuit would do better..

Still fun to play with even though I have no practical use for this. Just a fun cool project for the scrap pile later..lol..


----------



## JoeG (Jul 18, 2010)

Thanks for taking the time and posting those great educational links PStechPaul. This type of knowlege sharing is one of the things that I really like about this forum.
Joe


----------



## electrotech (Mar 11, 2013)

^ Agreed. Those were excellent links and I appreciate the help, even though the initial topic I brought up is just weird to build..


----------



## PStechPaul (May 1, 2012)

You're welcome 

I like to help, and I almost always learn something when I answer questions and provide advice. This is a great forum


----------



## electrotech (Mar 11, 2013)

I have been playing more with this module, really cool mess with. Like I stated before the circuit I am using drives it well, and I get a nice variable voltage with it. 

I am curious though as to the feedback pin of the LM2596. The impedance is so high and the current draw is so low on the gate of the IGBT, that there is no way for the LM2596 to know what the output voltage is doing on the collector. There simply isn't a voltage drop on the gate so it can compensate when the voltage starts to drop under heavy current on the collector side of the IGBT. Any ideas on how I can incorporate some sort of feedback into the LM2596 so it better controls everyting?..

Thanks again all for the assistance, it's a cool project to learn from..


----------



## PStechPaul (May 1, 2012)

One way might be to put a 12V zener across the gate to emitter, but I'm not sure that will work. But you might be able to make a driver from two transistors so that there will be only a single B-E junction voltage for the emitter follower, and the output voltage should be just 0.7 volts less than the voltage on the base.

But you seem to have the load on the collector to V+. And you are using the LM2596, which is a switching regulator with a built-in MOSFET to GND. If you are using the output of the module, you are using DC, so the IGBT is still operating in linear mode. You can make a linear driver using a circuit as shown here:










You can use the two transistor and 3 resistor level shifter and connect the GND to the load on the emitter of the IGBT, for a gate driver with a constant 0.6-0.7V drop to the load. For a linear drive, you don't need the LM2596 module. You can just use a pot across the supply, or maybe add a zener or a regulator. An LM317 makes a nice adjustable supply.


----------



## electrotech (Mar 11, 2013)

Thanks for the tips, much appreciated.

Yeah you are right, everything is running in the linear form at the moment, and the reason I am using the LM2596 is because it was one of those cheaper to buy than build dual LM2577/LM2596 boards from ebay. The first stage is the LM2577, I cranked the voltage to about 29 volts, then it goes into the 2596 to "regulate" the IGBT. Which as you stated needed the 26-29 volts to get 21 volts out on the collector of the IGBT. Works well for an experiment. lol

But as you said maybe a true PWM IGBT driver IC would work better with this. I assume that's what they did in that circuit pictured on page 1. The rectangle part next to the 7805 is a DC-DC Boost module of some sort. The the gate is driven by the unknown IC.


----------

