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Author Topic: Reliable and Flexible Switching System  (Read 53197 times)

EMJunkie

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Reliable and Flexible Switching System
« on: April 25, 2014, 08:28:38 AM »
Hi Everyone,

I have been around for a long time in different FE Community's. Mostly collecting information.

The biggest problem with Building and Testing Devices that I have seen, is a Reliable and Flexible Switching System. We should all work together and bring the best of us in to go from Step one to actually selling the kits to those that want them.


I propose a collaboration of users to work on a better more Reliable and Flexible Switching System!

Some initial requirements:
1: Microcontroller Controlled with a Client so as can be controlled from ones Laptop/PC.
2: Capable of fine adjustments for fine tuning of frequency's.
3: Capable of reasonable Voltages and Currents.
4: Capable of a large range of Frequencies.
5: Wide range of Switching Capabilities, Single H-Bridge, Dual H-Bridge, Single Switching mode...
6: Plenty of Circuit Protection/Isolation for the Microcontroller and also the User, fused etc...
7: Clean Slim and cost efficient for all.

I have a friend 'Selfonlypath' that is no longer online that did something similar. To give him and Dan, his friend, credit, they did a very good job but not all is still available. See attached Picture below. A few problems I had found with this circuit, supply current was not high enough from the RK-0515s at high frequency and the Fetts would not switch properly.

Some Recommendations for Microcontrollers:

1: FEZ Hydra Mainboard (Medium Speed reasonable price)
2: FEZ Raptor Mainboard (Fast 400MHz but expensive)
3: Arduino Mega 2560 (Slow 16MHz)

Personally I like the GHI Boards.

I can do the programming of the board and the Windows Client. Can someone do the Circuit Design and source cheap Chinese Manufacture? I already have a similar unit to SelfOnlyPath running and it is worth its weight in Gold. I will admit, if it can be improved on it would be great and if the entire Community can benefit and have the same access to it then it would help immensely!

I have attached some pictures of my unit so others can see the clunker I use.

All the Best

  Chris

« Last Edit: April 25, 2014, 02:21:29 PM by EMJunkie »

lost_bro

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Re: Reliable and Flexible Switching System
« Reply #1 on: April 27, 2014, 12:02:04 AM »
Good day EMJunkie

I've been thinking along the same lines for a while also:

Found this about a year ago and saved it:

http://www.source-for-innovations.com/pgen.htm

Seems like it will do PLL also and can program from LCD or laptop.

take care, peace.
lost_bro


MarkE

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Re: Reliable and Flexible Switching System
« Reply #2 on: April 27, 2014, 12:40:08 AM »
There are several considerations and they are unlikely to be met by a single solution.  For the control side considerations include:

1. Frequency capability.
2. Synchronization capability.
3. Power topologies supported.
4. Fault handling.  This is really important because it means the difference between constantly frying the power section, or just gracefully losing function.

On the power side:

5. Single ended, or half bridge.
6. Number of sections:  1, 2, 3, 4, or 6 being the most common. 1, 2, 3 for half bridges, and 1, 2, 4, and 6 for single ended.
7. Type of conduction:  continuous, discontinuous, critical conduction.
8. Trapezoidal, Quasi-resonant, or fully resonant.
9. DC or AC output
10. Voltage capability
11. Current capability


For any combinations there are a number of solutions that would work.  My recommendation is that rather than try and find a one size fits all, start with at least one class of machine, and then work on meeting your goals of low cost and flexibility within that framework.  For high power switches, Avageo has some really great isolated IGBT drivers that include lots of housekeeping functions that make it a lot easier to drive the devices reliably and survive faults.

EMJunkie

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Re: Reliable and Flexible Switching System
« Reply #3 on: April 27, 2014, 12:44:18 AM »
Good day EMJunkie

I've been thinking along the same lines for a while also:

Found this about a year ago and saved it:

http://www.source-for-innovations.com/pgen.htm

Seems like it will do PLL also and can program from LCD or laptop.

take care, peace.
lost_bro

Hey Lost_Bro,

I like it! Problem is its only good to 100KHz.

All the Best

  Chris

EMJunkie

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Re: Reliable and Flexible Switching System
« Reply #4 on: April 27, 2014, 12:51:30 AM »
There are several considerations and they are unlikely to be met by a single solution.  /...

Hi MarkE,

Agreed! Its going to be hard to do a single unit that will do it all!

My unit is good from about 0.04 to 7MHz for switched DC in either H-Bridge Mode or Single Switched Mode.

I think if we think broadly and then expandable after that then we can move forward with units like the Arduino Shield concept! I think there is sufficient technology out there now that this is a very achievable task and at low cost.

All the Best

  Chris

P.S: Anyone willing to do some Circuit Re-Design and throw it out there? Even if its based on the Above design!


TinselKoala

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Re: Reliable and Flexible Switching System
« Reply #5 on: April 27, 2014, 12:52:11 AM »
Fault Handling! Housekeeping! What a concept....

 :'(
 ;D

MarkE

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Re: Reliable and Flexible Switching System
« Reply #6 on: April 27, 2014, 03:08:08 AM »
Hi MarkE,

Agreed! Its going to be hard to do a single unit that will do it all!

My unit is good from about 0.04 to 7MHz for switched DC in either H-Bridge Mode or Single Switched Mode.

I think if we think broadly and then expandable after that then we can move forward with units like the Arduino Shield concept! I think there is sufficient technology out there now that this is a very achievable task and at low cost.

All the Best

  Chris

P.S: Anyone willing to do some Circuit Re-Design and throw it out there? Even if its based on the Above design!
7MHz is way beyond the regime of hard switching topologies.  You are going to have to go quasi-resonant or fully resonant in order to manage the switching losses.  Otherwise you are just going to burn your power output stage and probably the driver stage as well.

lost_bro

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Re: Reliable and Flexible Switching System
« Reply #7 on: April 27, 2014, 03:18:13 AM »
..... A few problems I had found with this circuit, supply current was not high enough from the RK-0515s at high frequency and the Fetts would not switch properly.

 Chris

Hello All:


Please see the attached Isolated gate drive schematic:
This has a max Vcc of 35VDC and can source 9amps for fast switching... its a design that Cree is using in the SiC MOSFET demo boards.

This can be modified to suite the need. 
If you are not a fan of Avago optoisolators, then Silicon Labs has the LED emulator that uses proprietary technology to emulate the LED opto, but with a type of RF on chip Tx/Rx for really fast communication.
I'm a fan of GDTs, but the design of these is frequency dependent and having to wind a new one for each experiment can be tedious.

take care, peace
lost_bro



EMJunkie

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Re: Reliable and Flexible Switching System
« Reply #8 on: April 27, 2014, 09:02:48 AM »
7MHz is way beyond the regime of hard switching topologies.

Hey MarkE,

Mine works without doing any Burn Outs! I do have issues beyond 7MHz however. Heating and so on. The 47uH Inductor does a pretty good job at keeping the RF out of the isolated 15v supply.

I guess this is why we need to think outside the box!

All the Best

  Chris

EMJunkie

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Re: Reliable and Flexible Switching System
« Reply #9 on: April 27, 2014, 09:05:11 AM »
Hello All:


Please see the attached Isolated gate drive schematic:
This has a max Vcc of 35VDC and can source 9amps for fast switching... its a design that Cree is using in the SiC MOSFET demo boards.

This can be modified to suite the need. 
If you are not a fan of Avago optoisolators, then Silicon Labs has the LED emulator that uses proprietary technology to emulate the LED opto, but with a type of RF on chip Tx/Rx for really fast communication.
I'm a fan of GDTs, but the design of these is frequency dependent and having to wind a new one for each experiment can be tedious.

take care, peace
lost_bro

Thanks Lost_Bro! We will need to do some changes to go to the next step! Electronics Gurus! Anyone keen to participate?

All the Best

  Chris

Farmhand

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Re: Reliable and Flexible Switching System
« Reply #10 on: April 27, 2014, 10:46:00 AM »
Good idea, Why not go to a modular design, as in we could have the control board and several switching boards that will accept the signal from the control board with different switching boards for different applications, voltages - frequencies - current levels ect.

eg. a switching board would hold, the caps/regulator, mosfet drivers or switch drivers of whatever kind and all associated protections for the switching and driver solution, isolation ect.

The control board could be either Arduino or picaxe or whatever then and the user can still use the different switching boards. The switching boards could simply have a connector with the signal and power jacks so that one board plugs into the other without any wires to keep the signal traces short. Plug and play kinda. Most of us can manage to make a PCB, or we could get them made in bulk if a few of us chip in some money.

Cheers

EMJunkie

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Re: Reliable and Flexible Switching System
« Reply #11 on: April 27, 2014, 10:53:50 AM »
Good idea, Why not go to a modular design, as in we could have the control board and several switching boards that will accept the signal from the control board with different switching boards for different applications, voltages - frequencies - current levels ect.

eg. a switching board would hold, the caps/regulator, mosfet drivers or switch drivers of whatever kind and all associated protections for the switching and driver solution, isolation ect.

The control board could be either Arduino or picaxe or whatever then and the user can still use the different switching boards. The switching boards could simply have a connector with the signal and power jacks so that one board plugs into the other without any wires to keep the signal traces short. Plug and play kinda. Most of us can manage to make a PCB, or we could get them made in bulk if a few of us chip in some money.

Cheers

Hey Farmhand! Long time since we spoke!

Yes I agree! It only makes sense that the design stays in a modular form! Also it is critical to keep the signal traces short like you have pointed out! Also just as critical to keep Low Power Logic Circuitry well away from the High Voltage/Current Switching Circuitry!

The Circuit I posted is a very good circuit! Maybe if we could have someone start there and work on the component update to some better high speed smaller components?

I don't think anyone is keen to draw up the files? I know there are a few Electronics Guru's out there! Maybe they just have not yet had the need to check this thread out?

All the Best

  Chris

Farmhand

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Re: Reliable and Flexible Switching System
« Reply #12 on: April 27, 2014, 11:55:53 AM »
Might be a good idea to have voltage and current sense provisions to feedback to inputs on the micro processor so that we can use them for more control of the circuit. Over voltage or current protections ect. can be written into the code then.


Cheers

MarkE

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Re: Reliable and Flexible Switching System
« Reply #13 on: April 27, 2014, 01:00:16 PM »
Hey MarkE,

Mine works without doing any Burn Outs! I do have issues beyond 7MHz however. Heating and so on. The 47uH Inductor does a pretty good job at keeping the RF out of the isolated 15v supply.

I guess this is why we need to think outside the box!

All the Best

  Chris
An IGBT with a 1us turn off time isn't going to do very well hard switching at 7MHz.

EMJunkie

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Re: Reliable and Flexible Switching System
« Reply #14 on: April 28, 2014, 01:15:42 AM »
An IGBT with a 1us turn off time isn't going to do very well hard switching at 7MHz.

Hi MarkE,

I agree! Choosing the best components for the job is essential!

I have used: 5N3003
Turn-On Delay Time: 60ns
Turn-Off Delay Time: 220ns

So far this is one of my favourite N Channel MOSFET's!

All the Best

  Chris