# Recommended MOSFET Gate Driver and MOSFETs for H-Bridge Motor Controller



## Siwastaja (Aug 1, 2012)

I'd start with a lot higher voltage leeway. Your 60V pack (when full) may barely be OK with a 100V MOSFET, but that would require very careful freewheeling, snubber and DC bus design. The inductive spikes can be huge and it's easier to start with a device that won't blow up right away. Get a 200V MOSFETs and ramp up the voltage while scoping for voltage transients.

MOSFETs parallel easily, but make sure your DC link has low inductance, the + and - planes need to be physically close to each other.


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## cts_casemod (Aug 23, 2012)

I think your pack is just right. I don't see, however why lipos on this day and age. Unless you want the project to be very lightweight I would choose LiFEPO4 for several reasons.

As with the mosfet:

First I guess that is a brushed DC motor right? If so, my personal advice is go with a single switch and use a contactor for reversing. Efficiency will be higher and complexity will be smaller. Messing arround with high side switches is no beginners job.

No, that Mosfet is not suitable on its own. You'll need at least 4 of them paralleled to be safe. If you want to use the H bridge you'll need 4*4 = 16.

For the gate drivers you need one 15V Power supply(isolated or not) for the low side switches and two Isolated 15V power supplies one for each high side mosfet. A 1W 15V DC-DC converter should do the trick.

Take a look at any high power DC Inverter (1000W or more) and learn from that design

Save yourself the hassle, I've been there. You need to use a brick IGBT or mosfet and build a driver for such. IRL 2110 is a good start, altough simplier drivers exits if you follow my advice and use a contactor to reverse, since you will only need a low side mosfet driver.

Brick IGBTs (600V) or mosfets (100V) will take care of your problems and you can get a 400Amp IGBT for $100 or a 200Amp for $50.

Here is a good example for a H bridge using brick IGBTs









Source 

http://commons.wikimedia.org/wiki/File:IGBT_H-bridge.JPG

Also, if you can bare with the noise, efficiency gains will be archieved with the use of smaller carrier frequencies of about 2 to 5KHz.

--------------------------------------------

If you find this useful please add to my reputation


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## jegues (Aug 5, 2013)

cts_casemod said:


> First I guess that is a brushed DC motor right? If so, my personal advice is go with a single switch and use a contactor for reversing. Efficiency will be higher and complexity will be smaller. Messing arround with high side switches is no beginners job.


Yes it is a brushed DC motor. Will reversing the direction of motor with the contactor be an issue if we plan to implement regenerative breaking into the motor controller?



cts_casemod said:


> Save yourself the hassle, I've been there. You need to use a brick IGBT or mosfet and build a driver for such. IRL 2110 is a good start, altough simplier drivers exits if you follow my advice and use a contactor to reverse, since you will only need a low side mosfet driver.
> 
> Brick IGBTs (600V) or mosfets (100V) will take care of your problems and you can get a 400Amp IGBT for $100 or a 200Amp for $50.


Can you tell me more about these "brick" IGBTs/MOSFETs? I've tried googling around but I haven't found very good information about them.

Are they simply multiple IGBTs or MOSFETS paralleled and packaged together in a single brick?

Thanks again for all your help!


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## subcooledheatpump (Mar 5, 2012)

IGBT module is the correct term, and yes they are multiple parallel IGBTs packaged together for you by the manufacture. 



> Large IGBT modules typically consist of many devices in parallel and can have very high current handling capabilities in the order of hundreds of amperes with blocking voltages of 6000 V


 That's from Wikipedia. 


Just personally I would use an IGBT module rather than trying to parallel single MOSFETs or IGBTs together. Paralleling MOSFETs does work but requires careful design of the physical layout. As it's already been stated you must minimize the inductance as much as possible, it will be easier to blow parallel MOSFETs than it will to be to blow a module unless you are very good a designing and implementing a good low inductance layout. A module already has a very good internal low inductance bus so you will save time and probably an explosion or two by just using a pre packaged module.


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## cts_casemod (Aug 23, 2012)

jegues said:


> Yes it is a brushed DC motor. Will reversing the direction of motor with the contactor be an issue if we plan to implement regenerative breaking into the motor controller?


No, it wont have any effect, providing you have the contactor on the right direction (Not trying to stop a foward mooving car with the contactor in reverse direction). But I doubt you have much regeneration from that motor. Shunt motors are preferred for this because you can adjust the field, a bit like you do on an old generator (Dynamo) to keep the voltage at a level that your battery can receive - Not too high and not too low.




jegues said:


> Can you tell me more about these "brick" IGBTs/MOSFETs? I've tried googling around but I haven't found very good information about them.
> 
> Are they simply multiple IGBTs or MOSFETS paralleled and packaged together in a single brick?


They might have one, two, six or seven IGBTs inside a case. They are NOT paralleled. Each device works independently. It is commonly called a brick IGBT for a single IGBT or a module if you have more than one inside the pack. That being said you font have to worry about equally sharing currents if paralleling devices, because there is only one, with the specified rating

There are also Intelligent Power modules - These have the gate driving circuitry inside, all you need to do is supply these drivers with the respective power supplies and signals and the module will also provide a fault signal if something goes wrong. An optoisolator is used between the micro controller outputs and the IPM gate terminals.

For any decent IGBT/Gate driver always think 15V supply


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## jegues (Aug 5, 2013)

Can you explain in greater detail how the motor will work with the contactor implementation as opposed to the H-Bridge design? (Maybe you can sketch out a shitty hand drawn schematic for me!)

Is it simply a contactor upstream of the motor with a low side switches downstream of the motor? What are the disadvantages/advantages of this scheme compared to the more traditional H-Bridge schem?

Thanks again!


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## cts_casemod (Aug 23, 2012)

jegues said:


> Can you explain in greater detail how the motor will work with the contactor implementation as opposed to the H-Bridge design? (Maybe you can sketch out a shitty hand drawn schematic for me!)
> 
> Is it simply a contactor upstream of the motor with a low side switches downstream of the motor? What are the disadvantages/advantages of this scheme compared to the more traditional H-Bridge schem?
> 
> Thanks again!


From the principle that you want the H bridge to be able to reverse the motor:

On a H bridge only two transistors work at a time to provide the motor with a working current. The other two do jut the same, but with a reversed polarity. you can also add your modulating signal to one or both the transistors to control the speed of the motor.

The contactor should last for the life of the vehicle if you wait untill the car is stopped to engage reverse.

http://www.kellycontroller.com/reversing-contactor-c-32_48.html

Just pick one and wire it as per manufacturer instructions between the motor and the controller.

Advantages: Using a contactor means you just need a single swith (IGBT/Mosfet) to control the motor speed/torque. Less electronic components, easier controller design, probably cheaper.


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## jegues (Aug 5, 2013)

cts_casemod said:


> From the principle that you want the H bridge to be able to reverse the motor:
> 
> On a H bridge only two transistors work at a time to provide the motor with a working current. The other two do jut the same, but with a reversed polarity. you can also add your modulating signal to one or both the transistors to control the speed of the motor.
> 
> ...


So why isn't everyone doing this? All the designs I've seen so far have been H-Bridges with 4 switches.(where each switch is a pair of transistors)


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## cts_casemod (Aug 23, 2012)

jegues said:


> So why isn't everyone doing this? All the designs I've seen so far have been H-Bridges with 4 switches.(where each switch is a pair of transistors)


"Everyone" is a very vague statement. References?
I used to do it with an H bridge at college, but that was with robot toys drawing only a few mA

Forklifts have used reversing contractors for a long time. They were used in trains long before high power semiconductors were available. The list goes on.

At the end of the day, you can do it with both ways, I am just pointing you the easiest way.


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## Siwastaja (Aug 1, 2012)

jegues said:


> So why isn't everyone doing this? All the designs I've seen so far have been H-Bridges with 4 switches.(where each switch is a pair of transistors)


AFAIK, all EV DC motor controllers use a reversing contactor instead of a H bridge for the reasons stated above. Sometimes it's optional - there are vehicles with no reverse, and many DIY EV conversions use the original transmission for reverse gear.

You need semiconductors to switch things quickly, but you should never want to reverse the direction quickly.


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## major (Apr 4, 2008)

Siwastaja said:


> AFAIK, all EV DC motor controllers use a reversing contactor instead of a H bridge for the reasons stated above. Sometimes it's optional - there are vehicles with no reverse, and many DIY EV conversions use the original transmission for reverse gear.
> 
> You need semiconductors to switch things quickly, but you should never want to reverse the direction quickly.


The SepEx drives use an H bridge for the field and contactorless reversing. Also, in non passenger car applications, quick reverse or plug reversal is quite common.

I agree that H-bridge is seldom used in the armature circuits for large DC drives.


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## Tesseract (Sep 27, 2008)

jegues said:


> So why isn't everyone doing this? All the designs I've seen so far have been H-Bridges with 4 switches.(where each switch is a pair of transistors)


Because an H-bridge has double the switching and conduction losses over a chopper and a reversing contactor, is why.


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## jegues (Aug 5, 2013)

I had a schematic drawn up previously, but here's my attempt at modifying it in order to incorporate the reversible contactor idea.

The actual parts (i.e. MOSFETS, Gate Driver etc...) within the schematic will likely change, but does the general layout seem reasonable? In other words, does it look like it will work?

Is there any flaws or design issues that jump out at first glance?

Thanks again!


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## major (Apr 4, 2008)

jegues said:


> Is there any flaws or design issues that jump out at first glance?


Remove the battery negative ground otherwise it shorts out when switched to reverse.


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## jegues (Aug 5, 2013)

major said:


> Remove the battery negative ground otherwise it shorts out when switched to reverse.


Oops 

Anything else? Is that the basic idea behind how the reversible contactor is suppose to work?


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## cts_casemod (Aug 23, 2012)

jegues said:


> Is there any flaws or design issues that jump out at first glance?


The contactor is in the wrong place and backwards. 

The diodes will short when you reverse the polarity and as major pointed you have a short circuit to ground

It is very clear why that schematic wont work, so for your own safety I would do something small first to get to know the basics. 

Good luck


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## jegues (Aug 5, 2013)

cts_casemod said:


> The contactor is in the wrong place and backwards.
> 
> The diodes will short when you reverse the polarity and as major pointed you have a short circuit to ground
> 
> ...


Is there any other schematics I can reference in order to get a better picture of how things should be hooked up?

I've never seen schematics for DC motor control with a reversible contactor, so this is new to me. Oh, and I'm not trying to build anything at the moment, I'm just trying to understand how the circuit works.

Where should the contactor be placed? And how is it backwards? Can you explain?

I thought the role of the reversible contactor is to simply flip the connections of the battery to the motor.

I've removed the ground at the negative lead of the battery, and attached the revised version of the schematic.

Thanks again!


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## cts_casemod (Aug 23, 2012)

jegues said:


> Is there any other schematics I can reference in order to get a better picture of how things should be hooked up?
> 
> Thanks again!


I wont give you a fish for you to eat, I'll tell you how to catch a fish.

The issue here is a bit of common sense, you clearly are not looking into the components. You place them there, but have no idea what they are doing. Google is your friend. Search for reversing a DC motor with a contactor or relay.

The four diodes, do you know why they are there for?
The contactor is shorting itself. Its backwards. The part with the four poles goes to the battery in a - + + - configuration and the two wires output is for the motor and diodes.

The minus on the contactor doesn't go to GND, goes to the output of the mosfets.

GND is connected the battery negative and the mosfets ONLY.


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## cts_casemod (Aug 23, 2012)

The forum is your friend. Here are the contactor connections:










http://www.diyelectriccar.com/forums/showthread.php/1997-ford-ranger-direct-drive-52099.html


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## jegues (Aug 5, 2013)

Hi cts_casemode! First of, thanks for all your help!



cts_casemod said:


> I wont give you a fish for you to eat, I'll tell you how to catch a fish.


Lets go fishing! 



cts_casemod said:


> The issue here is a bit of common sense, you clearly are not looking into the components. You place them there, but have no idea what they are doing. Google is your friend. Search for reversing a DC motor with a contactor or relay.


Sorry about that, I tried to quickly modify my previous schematic to incorporate the reversing contactor idea at work and didn't even check it over. 

I realize now the schematic I gave was pretty ridiculous, hopefully I can redeem myself a little bit!



cts_casemod said:


> The four diodes, do you know why they are there for?
> The contactor is shorting itself. Its backwards. The part with the four poles goes to the battery in a - + + - configuration and the two wires output is for the motor and diodes.
> 
> The minus on the contactor doesn't go to GND, goes to the output of the mosfets.
> ...


I scribbled down some stuff about the reversing contactor setup, and what I thought the diodes were for, my scribbles are attached below.

I figured the diodes were freewheeling diodes. That is, diodes that allow the current in the motor to slowly die down while the MOSFET or IGBT switch is open. These diodes are necessary to dissipate the stored energy in the inductance of the motor by bleeding it off through its own resistance. 

If you were to suddenly interrupt the current on the voltage, the voltage would spike dramatically.

One thing I noted when I was scribbling around on paper about the reversible contactor, is that everytime you throw the switches, the current flows into a different terminal on the motor. 

That means if you want the free wheeling diodes to work as intended, you'd have to reverse the connections on the diodes every time you throw the switch, otherwise the diode will short around the motor.

Is there a simple solution to this kind of problem?

Also I was reading more about DPDT switches for motor control and they seem to mention the following issues,

"The biggest limitation will be finding a physical switch that can handle enough current and voltage."

"Over time, a switch connected to a large motor or power source will burn out due to electrical arcs when making or breaking electrical connections."

Source: http://www.robotroom.com/DPDT-Bidirectional-Motor-Switch.html

I want to make sure I consider all my options for motor control schemes (i.e. H-Bridge, Reversing Contactor etc...) before I decide which scheme to pursue and design around.

I looked at the schematic you posted for the contactor connections, and I'm a little confused. 

First off, A1 and A2 must be for the field winding on the motor right? My motor is a permanent magnet brushed DC motor, so it's like my field winding has a constant current source flowing through it. In other words, I can't access the terminals of my field winding, it's fixed.

On the 4 terminal side of the reversing contactor, note that the outer most terminals are connected to B+, while the two inner most terminals connect to A1.

I figured the two inner most terminals should be connected to B-, no?

Any advice/suggestions/recommendations you have for me would be greatly appreciated!

Thanks again!

*EDIT:

*Previously you mentioned,



> If so, my personal advice is go with a single switch and use a contactor for reversing. Efficiency will be higher and complexity will be smaller. Messing arround with high side switches is no beginners job.


What makes implementing high side switches that much more difficult than low side switches?

Thanks again!


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## major (Apr 4, 2008)

jegues said:


> That means if you want the free wheeling diodes to work as intended, you'd have to reverse the connections on the diodes every time you throw the switch, otherwise the diode will short around the motor.
> 
> Is there a simple solution to this kind of problem?


Yes. Look at the diagram casey posted (#20). The FWD is in the controller between terminal B+ and M-.

What type a EV are you building that you need motor reverse?


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## jegues (Aug 5, 2013)

major said:


> Yes. Look at the diagram casey posted (#20). The FWD is in the controller between terminal B+ and M-.


Hi major!

Ah I see now! This not only answers my questions about the FWD, but also clarifies my confusion about the field winding and the inner terminals on the 4 terminal side of the contactor!

The inner terminals on the four terminal side of the contactor are simply M-, right? Are A2 and A1 just windings made up of that same M- wire?



major said:


> What type a EV are you building that you need motor reverse?


The application is for an electrical motorcycle with components from MotEnergy.

Here are some of our components:

Battery Package (60Ah package): http://www.electricmotorsport.com/store/ems_ev_parts_batteries_lpf_gbs_kit48.php

Motor: ME0708 (See specs on post #1)

Throttle: http://www.electricmotorsport.com/store/ems_ev_parts_throttles_magura_twist-grip.php

I understand that most motorcycles typically don't have a reverse gear, but we want to implement regenerative breaking so we need to be able to reverse the connections to the motor. That way, when the motor is decelerating from say full throttle in the forward direction, we can flip the terminals and dump the motors stored energy back into the battery.

Thanks again for all your help!


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## major (Apr 4, 2008)

jegues said:


> I understand that most motorcycles typically don't have a reverse gear, but we want to implement regenerative breaking so we need to be able to reverse the connections to the motor. That way, when the motor is decelerating from say full throttle in the forward direction, we can flip the terminals and dump the motors stored energy back into the battery.


A common misconception. You do not reverse the motor polarity for regeneration. That would be a plug reversal and put you over the handlebars as it vaporized the brushes.* So it turns out you don't need reversing contactors afterall. But if you're serious about regeneration, you'd need a half bridge. Better study up on that.

*Actually it would just lock the rear and spill you. Regeneration on a motorcycle is not super effective due to the weight transfer forward. That's why you see large brakes on the front and a smaller brake on the rear. Mild or subtle regen on a 2-wheeler is manageable but unlikely to to be noticed in range unless you negotiate many hills. And then may present motor heating problems. I'd put regen on the back burner until you do version 2.


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## cts_casemod (Aug 23, 2012)

Hi,

Lets start with this: 

NEVER, EVER 

reverse the contactor with the motor still spinning. This is the same as connecting two batteries with opposite polarity against each other. 

Even to engage reverse gear you have to wait for the motor to come to a stop. Your confusion may come from the induction motor theory. Here you command a negative slip. But a negative slip is not backwards, its simply slower that the actual motor speed. 

Forget that for DC. 

DC acts as a generator when the power is removed (when you release the throttle), although as I said before you wont get much regeneration, simply because the motor will stop acting as a generator as soon as its output voltage is lower than the battery. With this being said, if you only want to regenerate to stop (and not to recover usefull energy to the batteries) you can attach another contactor to some kind of resistor bank and here you can regenerate down to zero, altought as you know power in a resistor is dependant to the voltage, so it will become weaker and weaker as you reduce speed.

Back to your questions:

Yes, you are right in regards to the diodes. And a mistake on my last post, they need to be before the contactor, otherwise they would short the output when you reverse.



> Also I was reading more about DPDT switches for motor control and they seem to mention the following issues,
> 
> "The biggest limitation will be finding a physical switch that can handle enough current and voltage."
> 
> "Over time, a switch connected to a large motor or power source will burn out due to electrical arcs when making or breaking electrical connections."


It is not an issue to find such contactor. They are on the market, you simply buy what you need. Period.

You will not use the contactor to engage/disengage the motor. The switching, as said above, is done at ZERO speed, hence no current and no arcing to wear out the contacts. The contacts will still have mechanical wear and will last for about one or two milion cycles. How long will you take to engage reverse two million times? 



> I looked at the schematic you posted for the contactor connections, and I'm a little confused.


In shunt wound motors there is much less current flowing trough the field coild that there is flowing trough the armature. As such it is advantageous to reverse the field instead of the armature because the cotactor can be physically smaller and cheaper.

Series wound motor share the same current across both the armature and the field, so you usually do both as they work together.

On PM motors you can only invert the armature, because, as you say, your field is provided by permanent magnets.



> On the 4 terminal side of the reversing contactor, note that the outer most terminals are connected to B+, while the two inner most terminals connect to A1.
> 
> I figured the two inner most terminals should be connected to B-, no?


Correct. He has a series wound DC. In my opinion he overcomplicated without reason, maybe the contactor wasn't rated for the full voltage. Notice that even tough the current is the same, on a SW the field has only a small percentage of the total voltage, so it might be that he used a 48V contactor in a 144V system for economical reasons, hence the wiring method. I do not advise this and the way you say is the most correct, with a contactor rated for the pack voltage



> What makes implementing high side switches that much more difficult than low side switches?


You have four times the complexity and 2x more losses. The actual losses will depend on the IGBT/MOSFET that you use. For an IGBT at 300Amp a rough value will be 200Watt per device, so with a bridge a total of 400Watt loss, since two switches are active at the same time. A contactor uses 10Watt, does not need heatsink and will not break if you dont abuse it (Yes, by engaging reverse at 120MPH the contactor would blow). Do your maths.

You also need a heatsink and fans to take this heat away for the additional semiconductor device.

You need isolated DC-DC converters and drivers to feed the high side switches. They are very prone to fail if not done properly and should be left to experienced designers. On small motors is easy because you can use a PNP and an NPN transitor. Power devices are NPN only. I keep saying teachers should prepare students for REAL life, not just to make toys in a way they cannot be done in real life, but unfortunately we all have to learn for ourselves at some point in life.

Search Google for the theory behind N channel/PNP high side switches. This will be something very useful


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## PStechPaul (May 1, 2012)

It is possible to use a bootstrap circuit for the high side drives, and there are some drivers that do not need optoisolators. The HIP4081 is a complete H-bridge controller which works up to 80V:
http://www.intersil.com/content/dam/Intersil/documents/an93/an9325.pdf

You can also get half-bridge drivers that work on 600/1200V:
http://www.irf.com/product-info/datasheets/data/ir2114ss.pdf

And three-phase drivers:
http://www.irf.com/product-info/datasheets/data/ir2136.pdf

I agree that a reversing contactor can be more efficient than a full H-bridge, but for regeneration and dynamic braking I think it is the way to go. Here is a tutorial on using the HIP4081:
http://www.hvlabs.com/hbridge.html

This describes regenerative braking with a full H-bridge:
http://www.4qdtec.com/bridge.html

And the patent may be worth reading:
http://www.google.com/patents/US6518723

This is also good:
http://www.controleng.com/single-ar...braking/6ff87f94ef12313dc983ac33fd29a7ba.html


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## jegues (Aug 5, 2013)

major said:


> A common misconception. You do not reverse the motor polarity for regeneration. That would be a plug reversal and put you over the handlebars as it vaporized the brushes.* So it turns out you don't need reversing contactors afterall. But if you're serious about regeneration, you'd need a half bridge. Better study up on that.
> 
> *Actually it would just lock the rear and spill you. Regeneration on a motorcycle is not super effective due to the weight transfer forward. That's why you see large brakes on the front and a smaller brake on the rear. Mild or subtle regen on a 2-wheeler is manageable but unlikely to to be noticed in range unless you negotiate many hills. And then may present motor heating problems. I'd put regen on the back burner until you do version 2.


Hi major! 

I did some studying on half bridge motor control, and scribbled some stuff down, so I thought I'd go over it here. (See figure attached below)

I decided to do a mental run through of the operation of the half bridge circuit in 3 different stages: 1) Accelerating up to desired speed, 2) Maintaining desired speed, 3) Decelerating from desired speed.

Let's start with the accelerating scenario.

1) As we apply throttle there will be a PWM waveform fed to the drive MOSFET and an inverse of the same PWM waveform fed to the flywheel MOSFET.

As the average voltage that motor sees increases up to its steady state value necessary to eventually achieve the desired speed, the back EMF in the motor increases thus causing a decrease in the current supplied from the battery to the terminals of the motor.

Whenever the drive MOSFET switch is closed throughout this stage (flywheel MOSFET switch open), the current will flow in path 'A', and when the flywheel MOSFET switch is closed (drive MOSFET switch open) the current will 'freewheel' in path 'B'.

When the flywheel MOSFET switch is closed (drive MOSFET switch open) and the motor is freewheeling, the current from the battery will be suddenly interrupted and the inductance from the battery will try to maintain the current by drastically increasing its voltage. However, since we have a large capacitor across the terminals of our battery,(Main cap.) and we know that capacitors resist sudden changes in voltage, the batteries attempt cause a voltage spike is effectively suppressed.

2) Once the motor reaches its steady state speed, the back EMF in the motor will be approximately equal to that of average voltage seen at the terminals of the motor, and hence little to no current is drawn into or out of the terminals of the motor. 

3) If we wish to decelerate the motor from its steady state speed, we're going to reduce the throttle, reducing the duty cycle of the PWM waveform thus reducing the average voltage seen at the terminals of the motor.

As we reduce the throttle, there will be a period of time in which the back EMF in the motor is larger than the average voltage seen at the terminals of the motor. When this happens, the current will flow through either paths 'C' or 'D' depending on which MOSFET switch is closed at any given time.

When the flywheel MOSFET switch is closed (drive MOSFET switch open) the motor is shorted (current flowing in path 'D') and the 'braking current' increases.

Once the drive MOSFET switch is closed (flywheel MOSFET switch open) this increased current will be forced to flow down path 'C' and back into the battery, achieving our desired regenerative breaking!

Again, the large capacitor across the terminals of our battery ensures that each time the current flowing into (or out of) the battery is interrupted by the drive MOSFET opening, the impending voltage spike is suppressed.

Any flaws in my understanding so far?

Hi cts_casemode! 



> if you only want to regenerate to stop (and not to recover usefull energy to the batteries) you can attach another contactor to some kind of resistor bank and here you can regenerate down to zero, altought as you know power in a resistor is dependant to the voltage, so it will become weaker and weaker as you reduce speed.


Ah I see, so another contactor is needed accomodate this regenerative for braking purposes! Makes sense!

Hi PStechPaul! 



> It is possible to use a bootstrap circuit for the high side drives, and there are some drivers that do not need optoisolators. The HIP4081 is a complete H-bridge controller which works up to 80V:
> http://www.intersil.com/content/dam/...n93/an9325.pdf
> 
> You can also get half-bridge drivers that work on 600/1200V:
> ...


Wow! Thanks for the excellent references and resources!

Please give me some time to read through and study some of the material you've listed here, and hopefully I can come back with some interesting points to discuss, or perhaps even some questions.

I always like to double check to ensure that I am understanding things correctly.

Thanks again for all your help!


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## cts_casemod (Aug 23, 2012)

> It is possible to use a bootstrap circuit for the high side drives, and there are some drivers that do not need optoisolators. The HIP4081 is a complete H-bridge controller which works up to 80V:
> http://www.intersil.com/content/dam/...n93/an9325.pdf


On a bootstrap driver, both mosfets are switching, hence switching losses are added to the equation. Depending on the carrier frequency they might be higer than the conduction losses. Using a dedicated driver with isolated power supplies for each mosfet ensures each device can be on/off independently increasing efficiency. It is also advantageous to keep the main supply isolated from your 6/12V Auxiliary battery.

To clarify, only two switches are used for regeneration so you don't need an H bridge unless you need reverse.

Here is a quick link to help you understand the concept of regeneration on a DC motor:

http://electronics.stackexchange.co...-implement-regenerative-braking-of-a-dc-motor


The other two are optional: you only need them for reverse. Here you might choose to use a contactor for simplicity (gives you reverse and regen in reverse by inverting the polarity of the motor) or two aditional IGBT's/Mosfets or even no reverse at all. 

Again, by not using the full bridge, the main current path only travels trough one side switch, reducing wasted energy.

If you are looking to start playing here is a single IGBT for 300Amp with driver, very reasonably priced.

http://www.ebay.co.uk/itm/Eupec-IGB...009?pt=LH_DefaultDomain_0&hash=item2ec5e137a1

Or you can use one of these drivers with your chosen device:

http://www.ebay.co.uk/itm/Igbt-Driv...ial_Automation_Control_ET&hash=item5aee2ca63f


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## PStechPaul (May 1, 2012)

The stack exchange link was very helpful in describing regeneration with a half bridge. The intrinsic antiparallel diodes as shown in the devices (MOSFETs or IGBTs) are helpful and should be shown on the schematic. Actually, the regeneration should occur even if the high side is not energized, as the current will flow through the freewheeling diode, but if the high side is a MOSFET, there may be less losses if it is turned on. Also, the example shows the motor connected to ground, while most EVs have it connected to battery (+). Thanks for the additional information. 

I also agree that it may be better to use DC-DC converters to provide gate drive through optoisolators and gate drivers, especially for IGBTs where a negative drive voltage is recommended for faster turn-off. It is a good idea to keep the signal and logic circuitry isolated from the high currents and voltages on the power devices.


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## jegues (Aug 5, 2013)

PStechPaul said:


> I also agree that it may be better to use DC-DC converters to provide gate drive through optoisolators and gate drivers, especially for IGBTs where a negative drive voltage is recommended for faster turn-off. It is a good idea to keep the signal and logic circuitry isolated from the high currents and voltages on the power devices.


Sorry to resurrect this thread, but we are currently trying to select a suitable gate driver for our application.

I've seen gate drive chips with bootstrap and charge pump circuitry surrounding it in order to drive the high side switch, but I've also been told it can be done by using a DC-DC converter.

Can someone explain to me how this is done? Maybe a diagram or application note would make things more clear.

Thanks again!


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