On Mon, 25 May 2015 17:55:30 -0400 (EDT), bitrex
<bitrex@de.lete.earthlink.net> wrote:
>Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com>
> Wrote in message:
>> On Mon, 25 May 2015 16:47:00 -0400 (EDT), bitrex
>> <bitrex@de.lete.earthlink.net> wrote:
>>
>>>Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com>
>>> Wrote in message:
[snip]
>>>> That ought to work for bitrex.
>>>>
>>>> ...Jim Thompson
>>>> --
>>>
>>>Yes, that should. I was experimenting with also isolating the
>>> feedback loop with PWM and an optocoupler for total galvanic
>>> isolation, but cannot seem to pull it off.
>>
>> What's the frequency of your signal? If it's essentially DC, PWM
>> should be relatively easy... ramp and dump?
>>
>> ...Jim Thompson
>> --
>
>No more than about 5khz. The PWM chip takes an input voltage
> between 0 and 1 volt, so the idea was to float the PWM IC so its
> rails ride up and down on top of the output voltage and divide
> the modulation input down from the output, referred to the
> floating "ground" so as not to lose resolution.
>
>But the LT chip doesn't seem to cooperate with the idea.
I'm not following what you mean. What's the definition of _common_ on
the load side
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Reply by bitrex●May 25, 20152015-05-25
Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com>
Wrote in message:
> On Mon, 25 May 2015 16:47:00 -0400 (EDT), bitrex
> <bitrex@de.lete.earthlink.net> wrote:
>
>>Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com>
>> Wrote in message:
>>> On Mon, 25 May 2015 08:38:31 -0700, John Larkin
>>> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>On 25 May 2015 07:52:50 -0700, Winfield Hill
>>>><hill@rowland.harvard.edu> wrote:
>>>>
>>>>>John Larkin wrote...
>>>>>>
>>>>>> bitrex wrote:
>>>>>>>
>>>>>>> So I have a need for an analog isolation amplifier
>>>>>>> thing into a HV section at low audio frequencies. ...
>>>>>>
>>>>>> I tweaked the basic HV opamp circuit a little...
>>>>>>
>>>>>> Version 4 [snip]
>>>>>
>>>>> Fairchild's MOC207 is rated at 70V, whereas their
>>>>> MOC8204 is rated at 400V. The CTR is much lower.
>>>>> Watch out for the class-A current * 400 volts.
>>>>
>>>>That's my original circuit, from 2005 I think.
>>>>
>>>>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG
>>>>
>>>>I used it to bias the collection electrodes in a 2D delay-line
>>>>detector, behind a microchannel plate. Didn't make any money, but it
>>>>was fun.
>>>>
>>>
>>> That ought to work for bitrex.
>>>
>>> ...Jim Thompson
>>> --
>>
>>Yes, that should. I was experimenting with also isolating the
>> feedback loop with PWM and an optocoupler for total galvanic
>> isolation, but cannot seem to pull it off.
>
> What's the frequency of your signal? If it's essentially DC, PWM
> should be relatively easy... ramp and dump?
>
> ...Jim Thompson
> --
No more than about 5khz. The PWM chip takes an input voltage
between 0 and 1 volt, so the idea was to float the PWM IC so its
rails ride up and down on top of the output voltage and divide
the modulation input down from the output, referred to the
floating "ground" so as not to lose resolution.
But the LT chip doesn't seem to cooperate with the idea.
--
----Android NewsGroup Reader----
http://usenet.sinaapp.com/
Reply by Jim Thompson●May 25, 20152015-05-25
On Mon, 25 May 2015 16:47:00 -0400 (EDT), bitrex
<bitrex@de.lete.earthlink.net> wrote:
>Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com>
> Wrote in message:
>> On Mon, 25 May 2015 08:38:31 -0700, John Larkin
>> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On 25 May 2015 07:52:50 -0700, Winfield Hill
>>><hill@rowland.harvard.edu> wrote:
>>>
>>>>John Larkin wrote...
>>>>>
>>>>> bitrex wrote:
>>>>>>
>>>>>> So I have a need for an analog isolation amplifier
>>>>>> thing into a HV section at low audio frequencies. ...
>>>>>
>>>>> I tweaked the basic HV opamp circuit a little...
>>>>>
>>>>> Version 4 [snip]
>>>>
>>>> Fairchild's MOC207 is rated at 70V, whereas their
>>>> MOC8204 is rated at 400V. The CTR is much lower.
>>>> Watch out for the class-A current * 400 volts.
>>>
>>>That's my original circuit, from 2005 I think.
>>>
>>>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG
>>>
>>>I used it to bias the collection electrodes in a 2D delay-line
>>>detector, behind a microchannel plate. Didn't make any money, but it
>>>was fun.
>>>
>>
>> That ought to work for bitrex.
>>
>> ...Jim Thompson
>> --
>
>Yes, that should. I was experimenting with also isolating the
> feedback loop with PWM and an optocoupler for total galvanic
> isolation, but cannot seem to pull it off.
What's the frequency of your signal? If it's essentially DC, PWM
should be relatively easy... ramp and dump?
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Reply by bitrex●May 25, 20152015-05-25
Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com>
Wrote in message:
> On Mon, 25 May 2015 08:38:31 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On 25 May 2015 07:52:50 -0700, Winfield Hill
>><hill@rowland.harvard.edu> wrote:
>>
>>>John Larkin wrote...
>>>>
>>>> bitrex wrote:
>>>>>
>>>>> So I have a need for an analog isolation amplifier
>>>>> thing into a HV section at low audio frequencies. ...
>>>>
>>>> I tweaked the basic HV opamp circuit a little...
>>>>
>>>> Version 4 [snip]
>>>
>>> Fairchild's MOC207 is rated at 70V, whereas their
>>> MOC8204 is rated at 400V. The CTR is much lower.
>>> Watch out for the class-A current * 400 volts.
>>
>>That's my original circuit, from 2005 I think.
>>
>>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG
>>
>>I used it to bias the collection electrodes in a 2D delay-line
>>detector, behind a microchannel plate. Didn't make any money, but it
>>was fun.
>>
>
> That ought to work for bitrex.
>
> ...Jim Thompson
> --
Yes, that should. I was experimenting with also isolating the
feedback loop with PWM and an optocoupler for total galvanic
isolation, but cannot seem to pull it off.
--
----Android NewsGroup Reader----
http://usenet.sinaapp.com/
Reply by bitrex●May 25, 20152015-05-25
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> Wrote in
message:
> On Mon, 25 May 2015 08:14:15 -0500, John S <Sophi.2@invalid.org>
> wrote:
>
>>On 5/24/2015 4:08 PM, John Larkin wrote:
>>> On Sun, 24 May 2015 15:36:43 -0400 (EDT), bitrex
>>> <bitrex@de.lete.earthlink.net> wrote:
>>>
>>>>
>>>> So I have a need for an analog isolation amplifier thing into a HV
>>>> section at low audio frequencies. I remembered the "HV opamp"
>>>> thing that John Larkin posted a while back and that seems to work
>>>> well, but I'd like to isolate the feedback via pwming it and
>>>> sending it back across the barrier via an optocoupler and
>>>> integrating. I dont really want to chop it first and have more
>>>> LV electronics on the HV side than necessary.
>>>>
>>>> Instead of having to pick a resistor divider for the largest
>>>> possible output signal and lose resolution on the PWM I thought
>>>> I'd bootstrap the PWM IC from the output like so:
>>>>
>>>> http://pastebin.com/1Ud9R9nM
>>>>
>>>> The components are all just representative and probably not what
>>>> I'd actually use. It seems like this test circuit should work
>>>> (the full loop hasn't been closed) but it doesn't appear to sim
>>>> properly.
>>>>
>>>> Any ideas?
>>>
>>>
>>> I tweaked the basic HV opamp circuit a little...
>>
>>Looks good but I guess we need to know how much isolation he needs.
>>Yours is 1Meg out-to-in, yes? Also, the 1Meg has a voltage limit as
>>discussed in another thread.
>>
>>Have I overlooked something?
>
> The ones we drew aren't isolated at all; the power supplies are all
> grounded.
>
> I guess the idea of the deleted PWM box is to measure some voltage and
> opto-couple it back to the grounded side, which would allow shuffling
> grounds to give full isolation. I'm not sure.
>
On Mon, 25 May 2015 08:58:48 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:
>On Mon, 25 May 2015 08:38:31 -0700, John Larkin
><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On 25 May 2015 07:52:50 -0700, Winfield Hill
>><hill@rowland.harvard.edu> wrote:
>>
>>>John Larkin wrote...
>>>>
>>>> bitrex wrote:
>>>>>
>>>>> So I have a need for an analog isolation amplifier
>>>>> thing into a HV section at low audio frequencies. ...
>>>>
>>>> I tweaked the basic HV opamp circuit a little...
>>>>
>>>> Version 4 [snip]
>>>
>>> Fairchild's MOC207 is rated at 70V, whereas their
>>> MOC8204 is rated at 400V. The CTR is much lower.
>>> Watch out for the class-A current * 400 volts.
>>
>>That's my original circuit, from 2005 I think.
>>
>>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG
>>
>>I used it to bias the collection electrodes in a 2D delay-line
>>detector, behind a microchannel plate. Didn't make any money, but it
>>was fun.
>>
>
>That ought to work for bitrex.
>
> ...Jim Thompson
Since Spice usually ignores breakdown voltages, you may as well
simulate with some part that's in the standard library.
Reply by Jim Thompson●May 25, 20152015-05-25
On Mon, 25 May 2015 08:38:31 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>On 25 May 2015 07:52:50 -0700, Winfield Hill
><hill@rowland.harvard.edu> wrote:
>
>>John Larkin wrote...
>>>
>>> bitrex wrote:
>>>>
>>>> So I have a need for an analog isolation amplifier
>>>> thing into a HV section at low audio frequencies. ...
>>>
>>> I tweaked the basic HV opamp circuit a little...
>>>
>>> Version 4 [snip]
>>
>> Fairchild's MOC207 is rated at 70V, whereas their
>> MOC8204 is rated at 400V. The CTR is much lower.
>> Watch out for the class-A current * 400 volts.
>
>That's my original circuit, from 2005 I think.
>
>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG
>
>I used it to bias the collection electrodes in a 2D delay-line
>detector, behind a microchannel plate. Didn't make any money, but it
>was fun.
>
That ought to work for bitrex.
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Reply by John Larkin●May 25, 20152015-05-25
On 25 May 2015 07:52:50 -0700, Winfield Hill
<hill@rowland.harvard.edu> wrote:
>John Larkin wrote...
>>
>> bitrex wrote:
>>>
>>> So I have a need for an analog isolation amplifier
>>> thing into a HV section at low audio frequencies. ...
>>
>> I tweaked the basic HV opamp circuit a little...
>>
>> Version 4 [snip]
>
> Fairchild's MOC207 is rated at 70V, whereas their
> MOC8204 is rated at 400V. The CTR is much lower.
> Watch out for the class-A current * 400 volts.
That's my original circuit, from 2005 I think.
https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG
I used it to bias the collection electrodes in a 2D delay-line
detector, behind a microchannel plate. Didn't make any money, but it
was fun.
Reply by John Larkin●May 25, 20152015-05-25
On Mon, 25 May 2015 10:09:27 -0400 (EDT), bitrex
<bitrex@de.lete.earthlink.net> wrote:
>John S <Sophi.2@invalid.org> Wrote in message:
>> On 5/24/2015 4:08 PM, John Larkin wrote:
>>> On Sun, 24 May 2015 15:36:43 -0400 (EDT), bitrex
>>> <bitrex@de.lete.earthlink.net> wrote:
>>>
>>>>
>>>> So I have a need for an analog isolation amplifier thing into a HV
>>>> section at low audio frequencies. I remembered the "HV opamp"
>>>> thing that John Larkin posted a while back and that seems to work
>>>> well, but I'd like to isolate the feedback via pwming it and
>>>> sending it back across the barrier via an optocoupler and
>>>> integrating. I dont really want to chop it first and have more
>>>> LV electronics on the HV side than necessary.
>>>>
>>>> Instead of having to pick a resistor divider for the largest
>>>> possible output signal and lose resolution on the PWM I thought
>>>> I'd bootstrap the PWM IC from the output like so:
>>>>
>>>> http://pastebin.com/1Ud9R9nM
>>>>
>>>> The components are all just representative and probably not what
>>>> I'd actually use. It seems like this test circuit should work
>>>> (the full loop hasn't been closed) but it doesn't appear to sim
>>>> properly.
>>>>
>>>> Any ideas?
>>>
>>>
>>> I tweaked the basic HV opamp circuit a little...
>>
>> Looks good but I guess we need to know how much isolation he needs.
>> Yours is 1Meg out-to-in, yes? Also, the 1Meg has a voltage limit as
>> discussed in another thread.
>>
>> Have I overlooked something?
>>
>>
>
>At the moment the +150 -150 volts is sufficient, but I was also
> interested in developing a topology that would work for
> significantly higher voltages...like a thousand or more plus to
> minus. I don't thinka resistor from output to input would be
> appropriate in that case. Hence the PWM idea.
Unless you plan to float the +-HV supplies, to get true isolation, a
feedback sense resistor will work fine. 100 Meg, 1 G, something like
that.
Powering a PWM circuit from kilovolt supplies will be inefficient.
To push my circuit past the voltage rating of the MOC8204s, you can
cascode better, low voltage optocouplers into depletion fets.
Or use photovoltaic optocouplers into conventional high voltage
mosfets. Easy but slow.
Reply by John Larkin●May 25, 20152015-05-25
On Mon, 25 May 2015 08:14:15 -0500, John S <Sophi.2@invalid.org>
wrote:
>On 5/24/2015 4:08 PM, John Larkin wrote:
>> On Sun, 24 May 2015 15:36:43 -0400 (EDT), bitrex
>> <bitrex@de.lete.earthlink.net> wrote:
>>
>>>
>>> So I have a need for an analog isolation amplifier thing into a HV
>>> section at low audio frequencies. I remembered the "HV opamp"
>>> thing that John Larkin posted a while back and that seems to work
>>> well, but I'd like to isolate the feedback via pwming it and
>>> sending it back across the barrier via an optocoupler and
>>> integrating. I dont really want to chop it first and have more
>>> LV electronics on the HV side than necessary.
>>>
>>> Instead of having to pick a resistor divider for the largest
>>> possible output signal and lose resolution on the PWM I thought
>>> I'd bootstrap the PWM IC from the output like so:
>>>
>>> http://pastebin.com/1Ud9R9nM
>>>
>>> The components are all just representative and probably not what
>>> I'd actually use. It seems like this test circuit should work
>>> (the full loop hasn't been closed) but it doesn't appear to sim
>>> properly.
>>>
>>> Any ideas?
>>
>>
>> I tweaked the basic HV opamp circuit a little...
>
>Looks good but I guess we need to know how much isolation he needs.
>Yours is 1Meg out-to-in, yes? Also, the 1Meg has a voltage limit as
>discussed in another thread.
>
>Have I overlooked something?
The ones we drew aren't isolated at all; the power supplies are all
grounded.
I guess the idea of the deleted PWM box is to measure some voltage and
opto-couple it back to the grounded side, which would allow shuffling
grounds to give full isolation. I'm not sure.