SMPS inverter voltage feedback methods

[Joerg]

MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:

[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,

[....]

I cant quite picture it, would you care to cough up an ascii
schematic?
didnt unitrode make a chipset that did prettty much this?

Here's what was rattling through my mind while I was thinking
about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- ! ---------+--/\/\/----
+Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- ! --+-----------
-Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.

Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but it
is 90
degrees out of phase with the input AC signal, and also very low
amplitude. Any ideas how to get the output phase to match the
AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie

Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it is
AC, at
the same freqency as V2, but the amplitude is Vout*R2/(R2+R3)
(roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066, or
Joergs
suggestion which is even simpler.

Ok I hooked it up right now I think, I am not sure if the waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1 side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the "demodulation"?
Also what
about FM would that work too, or is this AM method the way to go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...


V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near squarewave
on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the spikes.

Checked V2, it is a squarewave, gives similar results whether it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.

Those currents look not too far from right. Carefully recheck stuff
including the dots on the inductors. Try dropping the K value of the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.

I checked the coupling, and changed the L5 and L6 coil winding (dots)
to have both dots on the centertap,


Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are

hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie

operator error.

to think of it another way: its a very low power push-pull converter.
being very low power, you can feed the center-tap of the "primary" via a
voltage divider. if you get no secondary voltage, your sim is wrong.

to start with, throw away L1 - L3, and just drive ideal switches with a
complementary square wave. all L1-L3 does is allow the non-isolated
primary to provide the drive signals to the isolated voltage sampling
circuit (Qn, L4-L6). this is only necessary so you can then easily
synchronously rectify the output of L4.

personally, I like to use ideal components in my sims, to get the basic
concepts up and running. once you have proved the concept, *then* toss
in FETs/bipolars/leakage inductance etc. until you become an expert at
your particular sim package, this is a good approach.

Or just grab a few Mini-Circuits transformers and built it. A computer
may need 30 seconds to boot but my Weller heats up in 15 seconds

 

[Terry Given]

MooseFET wrote:


MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:


[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,


[....]

I cant quite picture it, would you care to cough up an
ascii schematic?
didnt unitrode make a chipset that did prettty much this?


Here's what was rattling through my mind while I was
thinking about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- ! ---------+--/\/\/----
+Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- ! --+-----------
-Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.


Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but it
is 90
degrees out of phase with the input AC signal, and also very low
amplitude. Any ideas how to get the output phase to match
the AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie


Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it
is AC, at
the same freqency as V2, but the amplitude is Vout*R2/(R2+R3)
(roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066, or
Joergs
suggestion which is even simpler.


Ok I hooked it up right now I think, I am not sure if the
waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1
side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the "demodulation"?
Also what
about FM would that work too, or is this AM method the way to go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...



V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near squarewave
on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the spikes.


Checked V2, it is a squarewave, gives similar results whether it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.


Those currents look not too far from right. Carefully recheck stuff
including the dots on the inductors. Try dropping the K value of the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.


I checked the coupling, and changed the L5 and L6 coil winding (dots)
to have both dots on the centertap,



Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are



hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie

operator error.

to think of it another way: its a very low power push-pull converter.
being very low power, you can feed the center-tap of the "primary" via
a voltage divider. if you get no secondary voltage, your sim is wrong.

to start with, throw away L1 - L3, and just drive ideal switches with
a complementary square wave. all L1-L3 does is allow the non-isolated
primary to provide the drive signals to the isolated voltage sampling
circuit (Qn, L4-L6). this is only necessary so you can then easily
synchronously rectify the output of L4.

personally, I like to use ideal components in my sims, to get the
basic concepts up and running. once you have proved the concept,
*then* toss in FETs/bipolars/leakage inductance etc. until you become
an expert at your particular sim package, this is a good approach.

Or just grab a few Mini-Circuits transformers and built it. A computer
may need 30 seconds to boot but my Weller heats up in 15 seconds

LOL

my little PFC is almost up and running. I have to seriously hobble the
loop gain to force PFC action though - at present its trying to regulate
out the 100Hz ripple

Still, it pretty much fired up first time, so I am happy. And I got a
nice sine-looking input current. shame about the bodged up (kludged to
you americans) tranformer though - I got my guys in SF to send me some
PQ26/20 core sets, and thats exactly what I got. A bobbin, a bobbin, my
kingdom for a bobbin. So I went and designed a monstrosity in an ETD34,
which was nearby. If I had a reasonably large 60u koolmu toroid I would
have used that, but mine are all 125u, so the core losses are too high,
and more turns gives me too much L. Oh well, hexafilar windings are fun.

As an aside, anyone know where i can get one of those cute little boxes
Jim Williams talks about (AN47 et al) with a male BNC at one side, a
female at the other? yes I know I can make such a thing with a diecast
box, but it only needs to contain 2 diodes, so I wanted a little pre-fab
box.....

Cheers
Terry

 

[Joerg]

Jamie Morken wrote:

MooseFET wrote:


MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:


[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,


[....]

I cant quite picture it, would you care to cough up an
ascii schematic?
didnt unitrode make a chipset that did prettty much this?


Here's what was rattling through my mind while I was
thinking about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- !
---------+--/\/\/---- +Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- !
--+----------- -Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.


Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but it
is 90
degrees out of phase with the input AC signal, and also very
low
amplitude. Any ideas how to get the output phase to match
the AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie


Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it
is AC, at
the same freqency as V2, but the amplitude is Vout*R2/(R2+R3)
(roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066,
or Joergs
suggestion which is even simpler.


Ok I hooked it up right now I think, I am not sure if the
waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1
side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the "demodulation"?
Also what
about FM would that work too, or is this AM method the way to go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...



V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near squarewave
on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the spikes.


Checked V2, it is a squarewave, gives similar results whether it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.


Those currents look not too far from right. Carefully recheck stuff
including the dots on the inductors. Try dropping the K value of
the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.


I checked the coupling, and changed the L5 and L6 coil winding (dots)
to have both dots on the centertap,



Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are



hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie


operator error.

to think of it another way: its a very low power push-pull converter.
being very low power, you can feed the center-tap of the "primary"
via a voltage divider. if you get no secondary voltage, your sim is
wrong.

to start with, throw away L1 - L3, and just drive ideal switches with
a complementary square wave. all L1-L3 does is allow the non-isolated
primary to provide the drive signals to the isolated voltage sampling
circuit (Qn, L4-L6). this is only necessary so you can then easily
synchronously rectify the output of L4.

personally, I like to use ideal components in my sims, to get the
basic concepts up and running. once you have proved the concept,
*then* toss in FETs/bipolars/leakage inductance etc. until you become
an expert at your particular sim package, this is a good approach.

Or just grab a few Mini-Circuits transformers and built it. A
computer may need 30 seconds to boot but my Weller heats up in 15
seconds

LOL

my little PFC is almost up and running. I have to seriously hobble the
loop gain to force PFC action though - at present its trying to regulate
out the 100Hz ripple

Still, it pretty much fired up first time, so I am happy. And I got a
nice sine-looking input current. shame about the bodged up (kludged to
you americans) tranformer though - I got my guys in SF to send me some
PQ26/20 core sets, and thats exactly what I got. A bobbin, a bobbin, my
kingdom for a bobbin. So I went and designed a monstrosity in an ETD34,
which was nearby. If I had a reasonably large 60u koolmu toroid I would
have used that, but mine are all 125u, so the core losses are too high,
and more turns gives me too much L. Oh well, hexafilar windings are fun.

In a pinch I made my own bobbin out of a Ferrero Rocher box. Of course,
prior to that all those bonbons in there had to be consumed ...

As an aside, anyone know where i can get one of those cute little boxes
Jim Williams talks about (AN47 et al) with a male BNC at one side, a
female at the other? yes I know I can make such a thing with a diecast
box, but it only needs to contain 2 diodes, so I wanted a little pre-fab
box.....

I just use the little blue Pomona boxes but some of those T-connectors
can be hacked by wacking off one of the female ports with an angle
grinder. Then you end up with an angled piece but if that's not a
concern why not try it? Soldering to the outside (if you have to) is a
bear though.

Right now I am looking for something similar but SMA. All it has to do
is contain anti-parallel diodes to ground, as a limiter.

 

[Terry Given]

Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:



[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,



[....]

I cant quite picture it, would you care to cough up an
ascii schematic?
didnt unitrode make a chipset that did prettty much this?



Here's what was rattling through my mind while I was
thinking about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- !
---------+--/\/\/---- +Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- !
--+----------- -Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.



Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but
it is 90
degrees out of phase with the input AC signal, and also
very low
amplitude. Any ideas how to get the output phase to match
the AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie



Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it
is AC, at
the same freqency as V2, but the amplitude is
Vout*R2/(R2+R3) (roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066,
or Joergs
suggestion which is even simpler.



Ok I hooked it up right now I think, I am not sure if the
waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1
side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the
"demodulation"? Also what
about FM would that work too, or is this AM method the way to
go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...




V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near
squarewave on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the
spikes.



Checked V2, it is a squarewave, gives similar results whether
it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.



Those currents look not too far from right. Carefully recheck
stuff
including the dots on the inductors. Try dropping the K value
of the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.



I checked the coupling, and changed the L5 and L6 coil winding
(dots)
to have both dots on the centertap,




Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are




hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie


operator error.

to think of it another way: its a very low power push-pull
converter. being very low power, you can feed the center-tap of the
"primary" via a voltage divider. if you get no secondary voltage,
your sim is wrong.

to start with, throw away L1 - L3, and just drive ideal switches
with a complementary square wave. all L1-L3 does is allow the
non-isolated primary to provide the drive signals to the isolated
voltage sampling circuit (Qn, L4-L6). this is only necessary so you
can then easily synchronously rectify the output of L4.

personally, I like to use ideal components in my sims, to get the
basic concepts up and running. once you have proved the concept,
*then* toss in FETs/bipolars/leakage inductance etc. until you
become an expert at your particular sim package, this is a good
approach.


Or just grab a few Mini-Circuits transformers and built it. A
computer may need 30 seconds to boot but my Weller heats up in 15
seconds

LOL

my little PFC is almost up and running. I have to seriously hobble the
loop gain to force PFC action though - at present its trying to
regulate out the 100Hz ripple

Still, it pretty much fired up first time, so I am happy. And I got a
nice sine-looking input current. shame about the bodged up (kludged to
you americans) tranformer though - I got my guys in SF to send me some
PQ26/20 core sets, and thats exactly what I got. A bobbin, a bobbin,
my kingdom for a bobbin. So I went and designed a monstrosity in an
ETD34, which was nearby. If I had a reasonably large 60u koolmu toroid
I would have used that, but mine are all 125u, so the core losses are
too high, and more turns gives me too much L. Oh well, hexafilar
windings are fun.

In a pinch I made my own bobbin out of a Ferrero Rocher box. Of course,
prior to that all those bonbons in there had to be consumed ...

LOL

I just use the little blue Pomona boxes but some of those T-connectors
can be hacked by wacking off one of the female ports with an angle
grinder. Then you end up with an angled piece but if that's not a
concern why not try it? Soldering to the outside (if you have to) is a
bear though.

duh. I just made one. Thanks Joerg!

Right now I am looking for something similar but SMA. All it has to do
is contain anti-parallel diodes to ground, as a limiter.

egg zackerly!

Cheers
Terry

 

[Jamie Morken]

MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:

[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,

[....]

I cant quite picture it, would you care to cough up an ascii
schematic?
didnt unitrode make a chipset that did prettty much this?

Here's what was rattling through my mind while I was thinking
about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- ! ---------+--/\/\/----
+Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- ! --+-----------
-Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.

Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but it
is 90
degrees out of phase with the input AC signal, and also very low
amplitude. Any ideas how to get the output phase to match the
AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie

Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it is
AC, at
the same freqency as V2, but the amplitude is Vout*R2/(R2+R3)
(roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066, or
Joergs
suggestion which is even simpler.

Ok I hooked it up right now I think, I am not sure if the waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1 side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the "demodulation"?
Also what
about FM would that work too, or is this AM method the way to go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...


V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near squarewave
on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the spikes.

Checked V2, it is a squarewave, gives similar results whether it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.

Those currents look not too far from right. Carefully recheck stuff
including the dots on the inductors. Try dropping the K value of the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.

I checked the coupling, and changed the L5 and L6 coil winding (dots)
to have both dots on the centertap,


Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are

hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie

operator error.

Yep, there can be no flux in the K2 transformer since the two primary
coils have mirror image currents and are wound the same direction,
heres their waveforms:

http://rocketresearch.nekrom.com/new/transformer chopper voltage measurement/waveform4-noflux.jpg

http://rocketresearch.nekrom.com/new/transformer chopper voltage measurement/circuit4-noflux.jpg

cheers,
Jamie

 

[Jamie Morken]

MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:

[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,

[....]

I cant quite picture it, would you care to cough up an ascii
schematic?
didnt unitrode make a chipset that did prettty much this?

Here's what was rattling through my mind while I was thinking
about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- ! ---------+--/\/\/----
+Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- ! --+-----------
-Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.

Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but it
is 90
degrees out of phase with the input AC signal, and also very low
amplitude. Any ideas how to get the output phase to match the
AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie

Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it is
AC, at
the same freqency as V2, but the amplitude is Vout*R2/(R2+R3)
(roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066, or
Joergs
suggestion which is even simpler.

Ok I hooked it up right now I think, I am not sure if the waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1 side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the "demodulation"?
Also what
about FM would that work too, or is this AM method the way to go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...


V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near squarewave
on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the spikes.

Checked V2, it is a squarewave, gives similar results whether it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.

Those currents look not too far from right. Carefully recheck stuff
including the dots on the inductors. Try dropping the K value of the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.

I checked the coupling, and changed the L5 and L6 coil winding (dots)
to have both dots on the centertap,


Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are

hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie

operator error.

to think of it another way: its a very low power push-pull converter.
being very low power, you can feed the center-tap of the "primary" via a
voltage divider. if you get no secondary voltage, your sim is wrong.

to start with, throw away L1 - L3, and just drive ideal switches with a
complementary square wave. all L1-L3 does is allow the non-isolated
primary to provide the drive signals to the isolated voltage sampling
circuit (Qn, L4-L6). this is only necessary so you can then easily
synchronously rectify the output of L4.

Ok thanks, will try a square wave drive

cheers,
Jamie

 

[Jamie Morken]

MooseFET wrote:


MooseFET wrote:


Terry Given wrote:

Jamie Morken wrote:

MooseFET wrote:


Joerg wrote:

MooseFET wrote:

[...]

To monitor the waveform? Why not just sample it? Send
sampling
pulse
through toroid xfmr,

[....]

I cant quite picture it, would you care to cough up an ascii
schematic?
didnt unitrode make a chipset that did prettty much this?

Here's what was rattling through my mind while I was thinking
about
how to do this.
ACFB+ ! ! ACFB-
+-/\/\--+
! !
(((((((
=======
(((((((
! ! !
! -- ! ---------+--/\/\/----
+Vout
! ! !
!/ \! \
!! ----------! !---- /
Drive ---- !! ( !\e e/! ! \
) !! ( ! ! ! !
) !! ------------+-------+----- ! --+-----------
-Vout
) !! ( !
GND ------ !! ( !
!! ---------------------------
This works even in the AC case if the resistors bring the
voltage low
enough that the EB junctions aren't breaking down while the
transistors trade off conducting.

Hi,
I put this schematic into ltspice and it seems to kind of
work, the AC
voltage is being chopped by the Drive signal to Vout, but it
is 90
degrees out of phase with the input AC signal, and also very low
amplitude. Any ideas how to get the output phase to match the
AC input?
Heres the circuit and waveform:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice file:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

cheers,
Jamie

Hi Jamie,
Vout is the DC output voltage to be sensed.
V2 is the drive to the AM chopper transistors
where you have V1 is actually the output of the circuit - it is
AC, at
the same freqency as V2, but the amplitude is Vout*R2/(R2+R3)
(roughly).
What Joerg & MooseFET are talking about is then using V2 to
synchronously demodulate this AC output - e.g. with a 4066, or
Joergs
suggestion which is even simpler.

Ok I hooked it up right now I think, I am not sure if the waveforms
are correct, it looks like it would be pretty hard to sample the
voltages as the peaks are very fast.
http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

V(n001) the green trace is the output voltage of L4 on the R1 side,
and V(n003) is the voltage at the common node of R3 and R2 (the
divided voltage from 120VAC.
So do these traces look correct for doing the "demodulation"?
Also what
about FM would that work too, or is this AM method the way to go?
here's the corrected
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

ltspice
file:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...


V2 should be a square wave.
The L4, L5, L6 transformer should end up with a near squarewave
on it
That is V2 times the voltage from V1
The L4, L5, L6 transformer may need a load resistance on the L4
section. A small capacitor may also be needed to kill the spikes.

Checked V2, it is a squarewave, gives similar results whether it is
AC or DC squarewave current.
Here are the L4, L5 and L6 waveforms:
http://rocketresearch.nekrom.com/new/transformer chopper voltage%......

The overall
circuit:http://rocketresearch.nekrom.com/new/transformer chopper voltage%...

I changed the V1 source to DC and got the same output spikes in
L4 as when it is AC.

Those currents look not too far from right. Carefully recheck stuff
including the dots on the inductors. Try dropping the K value of the
coupling to perhaps 0.25 to see that the inductors work right when
they are not coupled.

I checked the coupling, and changed the L5 and L6 coil winding (dots)
to have both dots on the centertap,


Both transformers should look like this:

0
))))))
==============
))))) ))))
0 0

Note where the dots are

hmm, the two primary coils are 180 degrees out of phase, with nice
looking waveforms but the secondary has just a few fA and pV on it
now!

cheers,
Jamie

operator error.

to think of it another way: its a very low power push-pull converter.
being very low power, you can feed the center-tap of the "primary" via a
voltage divider. if you get no secondary voltage, your sim is wrong.

to start with, throw away L1 - L3, and just drive ideal switches with a
complementary square wave. all L1-L3 does is allow the non-isolated
primary to provide the drive signals to the isolated voltage sampling
circuit (Qn, L4-L6). this is only necessary so you can then easily
synchronously rectify the output of L4.

personally, I like to use ideal components in my sims, to get the basic
concepts up and running. once you have proved the concept, *then* toss
in FETs/bipolars/leakage inductance etc. until you become an expert at
your particular sim package, this is a good approach.

Hi,

Removed the L1-L3 and added ideal switches to operate the two
transistors as push pull, output of L4 is still just AM modulated
peaks, think I will have to use a peak detector circuit, like
one of these puppies:

http://en.wikipedia.org/wiki/Peak_detector

I think maybe this is what was the idea from the start but I am
a bit thick headed

cheers,
Jamie

 

[MooseFET]

http://en.wikipedia.org/wiki/Peak_detector

I think maybe this is what was the idea from the start but I am
a bit thick headed

Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------

 

[Jamie Morken]

Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------

For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

I would like to have 12bits of voltage measurement resolution,
over the whole AC input range.

Also is there a way to decrease the AC voltage divider so that
there is higher amplitude feeding into the push pull transformer?
As MooseFet said the EB junction breakdowns are the limit to this,
I tried using back to back fets to allow for AC blocking here, but
didn't work to well. The benefit of higher amplitude is more current
in the push pull transformer and higher signal coming out.

cheers,
Jamie

 

[MooseFET]

For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.

You want to be sure to keep the chopping frequency far away from any
other frequency or harmonic in the design.

The performance of the chopper transistors needs a bit of optimizing
to make sure that the transistor parameters don't come into the
issue. You need to provide more than enough base drive for the lowest
HFE transistor. You can change to JFET or MOSFET switching if the
numbers come out better for you.

JFETs: Don't forward bias the gate enough to cause conduction.

MOSFETS: Beware of the capacitive coupling of the gate drive.

 

[Joerg]

[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------

For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.

Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference on the
isolated side. For 12 bit accuracy that won't exactly be a cheap one or
has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates the
influence of the leakage inductance.

 

[Jamie Morken]

MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.

Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference on the
isolated side. For 12 bit accuracy that won't exactly be a cheap one or
has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates the
influence of the leakage inductance.

What would an FM method look like for this application?

cheers,
Jamie

 

[Joerg]

MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.

Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference on
the isolated side. For 12 bit accuracy that won't exactly be a cheap
one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates the
influence of the leakage inductance.

What would an FM method look like for this application?

Two methods come to mind:

One would be a simple voltage to frequency conversion. Unfortunately the
old standby LM331 only goes to 100kHz and you want more BW so you'd have
to roll your own. It also doesn't come in SMT which can be a drag. Now
this gets transferred across a toroid and on the other side you
translate the frequency back into a voltage which can often be done
using the same chip. Or a micro just counts the pulses against its timer
which is pretty easy. For some reason I always run out of timers :-(

Method two would be a PLL where the voltage you want to log modulates
the loop. On the other side you place a detector. Remember AFC? That
used a detector scheme that measures the DC a station created at the end
of the IF chain. The DC was an indicator how far your radio was out of
tune and its oscillator was regulated to a point where it's right on. So
you need the first part of the AGC, sans loop.

[...]

 

[Jamie Morken]

MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference on
the isolated side. For 12 bit accuracy that won't exactly be a cheap
one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates the
influence of the leakage inductance.

What would an FM method look like for this application?

Two methods come to mind:

One would be a simple voltage to frequency conversion. Unfortunately the
old standby LM331 only goes to 100kHz and you want more BW so you'd have
to roll your own. It also doesn't come in SMT which can be a drag. Now
this gets transferred across a toroid and on the other side you
translate the frequency back into a voltage which can often be done
using the same chip. Or a micro just counts the pulses against its timer
which is pretty easy. For some reason I always run out of timers :-(

Method two would be a PLL where the voltage you want to log modulates
the loop. On the other side you place a detector. Remember AFC? That
used a detector scheme that measures the DC a station created at the end
of the IF chain. The DC was an indicator how far your radio was out of
tune and its oscillator was regulated to a point where it's right on. So
you need the first part of the AGC, sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses would be
a perfect application for that, the tricky part is getting the primary
side voltage to frequency, it might require its own clean power supply
for that section I think, like if using the PLL to generate the
frequency.

cheers,
Jamie

[...]

 

[Joerg]

Joerg wrote:
MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference on
the isolated side. For 12 bit accuracy that won't exactly be a cheap
one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates the
influence of the leakage inductance.

What would an FM method look like for this application?

Two methods come to mind:

One would be a simple voltage to frequency conversion. Unfortunately
the old standby LM331 only goes to 100kHz and you want more BW so
you'd have to roll your own. It also doesn't come in SMT which can be
a drag. Now this gets transferred across a toroid and on the other
side you translate the frequency back into a voltage which can often
be done using the same chip. Or a micro just counts the pulses against
its timer which is pretty easy. For some reason I always run out of
timers :-(

Method two would be a PLL where the voltage you want to log modulates
the loop. On the other side you place a detector. Remember AFC? That
used a detector scheme that measures the DC a station created at the
end of the IF chain. The DC was an indicator how far your radio was
out of tune and its oscillator was regulated to a point where it's
right on. So you need the first part of the AGC, sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses would be
a perfect application for that, the tricky part is getting the primary
side voltage to frequency, it might require its own clean power supply
for that section I think, like if using the PLL to generate the
frequency.

Well, yeah, but that's just a matter of a TLV431 or TL431. Under 10c a pop.

 

[Jamie Morken]

Jamie Morken wrote:
Joerg wrote:
MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference
on the isolated side. For 12 bit accuracy that won't exactly be a
cheap one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates
the influence of the leakage inductance.

What would an FM method look like for this application?


Two methods come to mind:

One would be a simple voltage to frequency conversion. Unfortunately
the old standby LM331 only goes to 100kHz and you want more BW so
you'd have to roll your own. It also doesn't come in SMT which can be
a drag. Now this gets transferred across a toroid and on the other
side you translate the frequency back into a voltage which can often
be done using the same chip. Or a micro just counts the pulses
against its timer which is pretty easy. For some reason I always run
out of timers :-(

Method two would be a PLL where the voltage you want to log modulates
the loop. On the other side you place a detector. Remember AFC? That
used a detector scheme that measures the DC a station created at the
end of the IF chain. The DC was an indicator how far your radio was
out of tune and its oscillator was regulated to a point where it's
right on. So you need the first part of the AGC, sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses would be
a perfect application for that, the tricky part is getting the primary
side voltage to frequency, it might require its own clean power supply
for that section I think, like if using the PLL to generate the
frequency.

Well, yeah, but that's just a matter of a TLV431 or TL431. Under 10c a pop.

For using a PLL, would the 74HCT4046 work for this 200kHz bandwidth or
is there another PLL that would be better to use? I've never used a PLL
directly so am not sure the best way to implement the voltage to
frequency generation for feeding the transformer the FM signal.

cheers,
Jamie

 

[Joerg]

Joerg wrote:
Jamie Morken wrote:
Joerg wrote:
MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference
on the isolated side. For 12 bit accuracy that won't exactly be a
cheap one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates
the influence of the leakage inductance.

What would an FM method look like for this application?


Two methods come to mind:

One would be a simple voltage to frequency conversion. Unfortunately
the old standby LM331 only goes to 100kHz and you want more BW so
you'd have to roll your own. It also doesn't come in SMT which can
be a drag. Now this gets transferred across a toroid and on the
other side you translate the frequency back into a voltage which can
often be done using the same chip. Or a micro just counts the pulses
against its timer which is pretty easy. For some reason I always run
out of timers :-(

Method two would be a PLL where the voltage you want to log
modulates the loop. On the other side you place a detector. Remember
AFC? That used a detector scheme that measures the DC a station
created at the end of the IF chain. The DC was an indicator how far
your radio was out of tune and its oscillator was regulated to a
point where it's right on. So you need the first part of the AGC,
sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses would be
a perfect application for that, the tricky part is getting the primary
side voltage to frequency, it might require its own clean power supply
for that section I think, like if using the PLL to generate the
frequency.

Well, yeah, but that's just a matter of a TLV431 or TL431. Under 10c a
pop.

For using a PLL, would the 74HCT4046 work for this 200kHz bandwidth or
is there another PLL that would be better to use? I've never used a PLL
directly so am not sure the best way to implement the voltage to
frequency generation for feeding the transformer the FM signal.

Yes, the 4046 would be able to do that. However, in order to obtain a
reasonable conversion factor precision and linearity you may have to
servo it. That gets old pretty quickly. IMHO a pulse modulation scheme
with DC restore on the system side is more economical.

 

[Jamie Morken]

Jamie Morken wrote:
Joerg wrote:
Jamie Morken wrote:
Joerg wrote:
MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So
long as
it is small and the transformer is well manufactured, the errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a reference
on the isolated side. For 12 bit accuracy that won't exactly be a
cheap one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates
the influence of the leakage inductance.

What would an FM method look like for this application?


Two methods come to mind:

One would be a simple voltage to frequency conversion.
Unfortunately the old standby LM331 only goes to 100kHz and you
want more BW so you'd have to roll your own. It also doesn't come
in SMT which can be a drag. Now this gets transferred across a
toroid and on the other side you translate the frequency back into
a voltage which can often be done using the same chip. Or a micro
just counts the pulses against its timer which is pretty easy. For
some reason I always run out of timers :-(

Method two would be a PLL where the voltage you want to log
modulates the loop. On the other side you place a detector.
Remember AFC? That used a detector scheme that measures the DC a
station created at the end of the IF chain. The DC was an indicator
how far your radio was out of tune and its oscillator was regulated
to a point where it's right on. So you need the first part of the
AGC, sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses
would be
a perfect application for that, the tricky part is getting the primary
side voltage to frequency, it might require its own clean power supply
for that section I think, like if using the PLL to generate the
frequency.


Well, yeah, but that's just a matter of a TLV431 or TL431. Under 10c
a pop.

For using a PLL, would the 74HCT4046 work for this 200kHz bandwidth or
is there another PLL that would be better to use? I've never used a PLL
directly so am not sure the best way to implement the voltage to
frequency generation for feeding the transformer the FM signal.

Yes, the 4046 would be able to do that. However, in order to obtain a
reasonable conversion factor precision and linearity you may have to
servo it. That gets old pretty quickly. IMHO a pulse modulation scheme
with DC restore on the system side is more economical.

Which form of pulse modulation would be good to implement to convert a
120VAC signal for this and then send it over the isolation transformer
or perhaps opto?

http://en.wikipedia.org/wiki/Pulse_modulation

That link shows 5 different pulse modulation methods, PAM, PWM, PCM,
PPM, PDM

cheers,
Jamie

 

[Joerg]

Joerg wrote:
Jamie Morken wrote:
Joerg wrote:
Jamie Morken wrote:
Joerg wrote:
MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So
long as
it is small and the transformer is well manufactured, the
errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a
reference on the isolated side. For 12 bit accuracy that won't
exactly be a cheap one or has to be calibrated.

b. Use an FM scheme to transfer the information. That eliminates
the influence of the leakage inductance.

What would an FM method look like for this application?


Two methods come to mind:

One would be a simple voltage to frequency conversion.
Unfortunately the old standby LM331 only goes to 100kHz and you
want more BW so you'd have to roll your own. It also doesn't come
in SMT which can be a drag. Now this gets transferred across a
toroid and on the other side you translate the frequency back into
a voltage which can often be done using the same chip. Or a micro
just counts the pulses against its timer which is pretty easy. For
some reason I always run out of timers :-(

Method two would be a PLL where the voltage you want to log
modulates the loop. On the other side you place a detector.
Remember AFC? That used a detector scheme that measures the DC a
station created at the end of the IF chain. The DC was an
indicator how far your radio was out of tune and its oscillator
was regulated to a point where it's right on. So you need the
first part of the AGC, sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses
would be
a perfect application for that, the tricky part is getting the primary
side voltage to frequency, it might require its own clean power supply
for that section I think, like if using the PLL to generate the
frequency.


Well, yeah, but that's just a matter of a TLV431 or TL431. Under 10c
a pop.

For using a PLL, would the 74HCT4046 work for this 200kHz bandwidth or
is there another PLL that would be better to use? I've never used a PLL
directly so am not sure the best way to implement the voltage to
frequency generation for feeding the transformer the FM signal.

Yes, the 4046 would be able to do that. However, in order to obtain a
reasonable conversion factor precision and linearity you may have to
servo it. That gets old pretty quickly. IMHO a pulse modulation scheme
with DC restore on the system side is more economical.

Which form of pulse modulation would be good to implement to convert a
120VAC signal for this and then send it over the isolation transformer
or perhaps opto?

http://en.wikipedia.org/wiki/Pulse_modulation

That link shows 5 different pulse modulation methods, PAM, PWM, PCM,
PPM, PDM

This one is easiest:
http://en.wikipedia.org/wiki/Pulse_amplitude_modulation

 

[Jamie Morken]

Jamie Morken wrote:
Joerg wrote:
Jamie Morken wrote:
Joerg wrote:
Jamie Morken wrote:
Joerg wrote:
MooseFET wrote:
MooseFET wrote:
[....]
http://en.wikipedia.org/wiki/Peak_detector
I think maybe this is what was the idea from the start but
I am
a bit thick headed
Also consider:
+12V
!
!VCC\ LM339 ---/\/\---+12V
IN ----!+ \ !
! >---+----+
--!- / ! !
! !VSS/ ! ===
! ! ! !
! -12V ! GND
------------
For the accuracy of this transformer chopped voltage
measurement,
what are some techniques to improve accuracy, or does it require
per unit calibration because of the variances in components?

The leakage inductance of the transformer is your enemy. So
long as
it is small and the transformer is well manufactured, the
errors in
the transformer will repeat nearly exactly.


Two ways to deal with this:

a. Switch to a known voltage once in a while. Such as a
reference on the isolated side. For 12 bit accuracy that won't
exactly be a cheap one or has to be calibrated.

b. Use an FM scheme to transfer the information. That
eliminates the influence of the leakage inductance.

What would an FM method look like for this application?


Two methods come to mind:

One would be a simple voltage to frequency conversion.
Unfortunately the old standby LM331 only goes to 100kHz and you
want more BW so you'd have to roll your own. It also doesn't come
in SMT which can be a drag. Now this gets transferred across a
toroid and on the other side you translate the frequency back
into a voltage which can often be done using the same chip. Or a
micro just counts the pulses against its timer which is pretty
easy. For some reason I always run out of timers :-(

Method two would be a PLL where the voltage you want to log
modulates the loop. On the other side you place a detector.
Remember AFC? That used a detector scheme that measures the DC a
station created at the end of the IF chain. The DC was an
indicator how far your radio was out of tune and its oscillator
was regulated to a point where it's right on. So you need the
first part of the AGC, sans loop.

Thanks, I have an FPGA on the secondary side so counting pulses
would be
a perfect application for that, the tricky part is getting the
primary
side voltage to frequency, it might require its own clean power
supply
for that section I think, like if using the PLL to generate the
frequency.


Well, yeah, but that's just a matter of a TLV431 or TL431. Under
10c a pop.

For using a PLL, would the 74HCT4046 work for this 200kHz bandwidth or
is there another PLL that would be better to use? I've never used a
PLL
directly so am not sure the best way to implement the voltage to
frequency generation for feeding the transformer the FM signal.


Yes, the 4046 would be able to do that. However, in order to obtain a
reasonable conversion factor precision and linearity you may have to
servo it. That gets old pretty quickly. IMHO a pulse modulation
scheme with DC restore on the system side is more economical.

Which form of pulse modulation would be good to implement to convert a
120VAC signal for this and then send it over the isolation transformer
or perhaps opto?

http://en.wikipedia.org/wiki/Pulse_modulation

That link shows 5 different pulse modulation methods, PAM, PWM, PCM,
PPM, PDM

This one is easiest:
http://en.wikipedia.org/wiki/Pulse_amplitude_modulation

Back to this one then I think?

http://rocketresearch.nekrom.com/new/transformer chopper voltage measurement/circuit2.jpg

cheers,
Jamie