30 kHz / 3 Phase signal
30 kHz / 3 Phase signal
(OP)
Hi, I'm trying to generate 3 x 30kHz signal each phase seperated by 120 degrees. These 3 phase will be used to turn On/Off FETs that will power some high frequency transformers.
What I'm looking for is the lowest cost effective solution to generate the signals. I was thinking of using 3 Op-Amps but I'm a bit worried about the reliability/accuracy for a production product. I'm sure there are plenny of cheap PWM ICs that could do this more effectively, I just don't know them.
Here are my specs:
3 phase 30 kHz signals, seperated by 120 degrees
Accuracy of ±5%
Supply voltage 10V
Waveform: Square, Triangle or Sin, I just want the reference
Power Output: Very small as it will trigger FETs.
Anybody had anything to suggest?
What I'm looking for is the lowest cost effective solution to generate the signals. I was thinking of using 3 Op-Amps but I'm a bit worried about the reliability/accuracy for a production product. I'm sure there are plenny of cheap PWM ICs that could do this more effectively, I just don't know them.
Here are my specs:
3 phase 30 kHz signals, seperated by 120 degrees
Accuracy of ±5%
Supply voltage 10V
Waveform: Square, Triangle or Sin, I just want the reference
Power Output: Very small as it will trigger FETs.
Anybody had anything to suggest?





RE: 30 kHz / 3 Phase signal
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If we learn from our mistakes I'm getting a great education!
RE: 30 kHz / 3 Phase signal
Will post more recent efforts soon, but there are
some old reference drawings at:
htt
<als>
RE: 30 kHz / 3 Phase signal
Some gates need lots of charge and that translates into a high load if you run at 30 kHz. It depends on your FETs.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 30 kHz / 3 Phase signal
Glenn
RE: 30 kHz / 3 Phase signal
How about a low end PIC microcontroller ?
One chip, low cost and simple.
And you could do neat things, like building in dead time.
RE: 30 kHz / 3 Phase signal
However, I do agree that if you need things like deadtime, using an MCU would give much more flexibility.
Glenn
RE: 30 kHz / 3 Phase signal
Ph3 Ph2 Ph1
1 0 1
0 0 1
0 1 1
0 1 0
1 1 0
1 0 0
RE: 30 kHz / 3 Phase signal
A uC would have been neat too but since it's a volume item I would have had to make a mask on the IC... which I try to avoid.
Anybody has recommendations on a cheap CMOS gate that could do the job?
BeerBaron
RE: 30 kHz / 3 Phase signal
A best way to build a state machine is to use either an EPROM or a programmable logic array chip, (or use a microcontroller). All of which will require individual programming.
RE: 30 kHz / 3 Phase signal
Glenn
RE: 30 kHz / 3 Phase signal
http://www.altera.com/
RE: 30 kHz / 3 Phase signal
RE: 30 kHz / 3 Phase signal
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: 30 kHz / 3 Phase signal
TTL counter is the simplest way to go. Or just do PLD if you know how to program.
Yes, "dead" time is very important.
From TTL to 10V FET gate - use any low side FET driver from IXYS or Micrel. Do not use IXYS "4 series"!!!!
They have "5" now - improved.
Depending how big is your FET - need to use "big" gate driver.
For 30kHz and average 50A FET - 2 A driver should be OK.
"dead time" - start in 100nS-200ns range.
If you don't know what "dead time" is - Google.
"dead time" can be easy done with 1R, 1C, and diode.
This whole design is kind of strange- you will be driving 3 phase SQUARE(???) signals into one transformer? Or few transformers?
Are you sure you don't need 3 sine signals 120deg shifted? then PWM them with some higher frequency?
RE: 30 kHz / 3 Phase signal
Saturated switching of the driver is also going to be a lot more efficient than some kind of linear power amplifier.