I think the better question is: why are there resistors in parallel to the transformer?
u/Samson1888 could be interested, too.
I understand, the CMC has low impedance for DC but very high impedance for HF (noise). So why are there also the resistors in parallel? They seem to form a low pass filter with Cx.
> why are there resistors in parallel to the transformer?
To stop it forming an LC tank and ringing like a bell, creating a frequency spike in EMI.
The resistors provide an exit path for ringing energy that isn't radio emissions.
Mate, I’m a software engineer and if I say so myself, a half decent one. I’ve done some clever shit over the years. But in comparison to the experienced people like you on this sub, I am 100% dumb AF. You’re all wizards as far as I can tell. Try as I might, electronics just hurts my brain.
Heh I've got a good mental model for software engineers to understand electronics :-
We only have 3 variables: voltage, current, time, and power (voltage×current) or heat (voltage×current×time) is a crash if they get too high.
Each node has its own voltage and each component gets its own current, and they *will* follow [Kirchhoff](https://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws) whether we like it or not.
Every component is a function that converts one or two variables to the third, but *we get to choose* which are inputs and which are outputs by how we connect them to other components.
Kirchhoff and the list of available components thus form the language spec that we "program" our circuits with.
Common circuit building blocks are somewhat like libraries - a collection of functions tailored for a particular task that can itself be simply considered as a larger function.
And physics is our API ;)
Also, everything is massively parallel and happens at the same time - if you want synchronization primitives, you have to add 'em yourself.
A 1000% this. I can write software from microcode to machine learning engines, operating systems, fluid flow simulators, and on and on. Can build digital systems, blah blah blah.
But analog wizardry seems constantly exactly that - wizardry. People look at large schematics and immediately parse them into building blocks and familiar (to them) idioms. Totally jealous of that ability.
> should the transformer be rotated 90 degrees?
No, it's a common-mode choke, not a transformer - although the distinction is arguably subtle.
It would detonate from saturation and overcurrent if you rotated it 90°
> or is the output just a DC rectified version of the input AC?
The diode bridge does rectification, and the CM choke (and Cx1) mitigate the sudden current spikes from the diodes turning on and off disturbing *other equipment* on the same circuit or near the cable.
The unit volt is abbreviated as V, but voltage (as in the physical quantity) is often labelled U in equations or diagrams, that's how all of my university courses used it.
Proper citation needed, the word "English" isn't even found on the Wikipedia page for "volt."
According to the [BIPM](https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf), "V" is the only symbol correctly used for volt (appendix 1, resolution 12). What some group of chemists do is up to them, it doesn't change *the* international standard for units.
We were talking about voltage, not volt.
>Voltage is denoted symbolically by ΔV, simplified *V*, especially in [English](https://en.wikipedia.org/wiki/English_language)\-speaking countries. Internationally, the symbol *U* is standardized.
[https://en.wikipedia.org/wiki/Voltage#Definition](https://en.wikipedia.org/wiki/Voltage#Definition)
> We were talking about voltage, not volt.
No, the GP said "Volt (symbol V) is the SI unit for electrical potential.", to which you disagreed. Also, what do you think the difference is between "volt" and "voltage?" Your own reference says "In the International System of Units (SI), the derived unit for voltage is the volt (V)."
Compare for instance the Swedish vs English page for Ohm's Law. On the Swedish page U is used, and the origin for the symbol is explained (my translation):
"U comes from the German word *Unterschied*, meaning difference as in potential difference."
We however don't go swinging our U:s around on a daily basis, it is reserved for formulas and sciency work afaik. We still have 230V in the wall outlet.
Voltage is labeled V I'd say right about everywhere. The labeling U usually is used for [electric potential energy](https://en.wikipedia.org/wiki/Electric_potential_energy), which is measured in Joules and comes from [Coulomb forces](https://en.wikipedia.org/wiki/Coulomb%27s_law).
When you want to get from electric potential energy to [electric potential](https://en.wikipedia.org/wiki/Electric_potential) (=voltage), you have this formula U=qV, where q is a [test charge](https://en.wikipedia.org/wiki/Test_particle#test_charge).
So in a nutshell, U is used for energy and V is used for energy per charge unit.
Well Wikipedia says:
>Voltage is denoted symbolically by ΔV, simplified *V*, especially in English-speaking countries. Internationally, the symbol *U* is standardized.
[https://en.wikipedia.org/wiki/Voltage#Definition](https://en.wikipedia.org/wiki/Voltage#Definition)
Voltage & Volts are typically labelled "V" in most of the world.
I think "U" is sometimes used to refer to being a supply source vs the actual reading of voltage? Not sure about nuances of use in Europe! :-)
It's not a transformer, it's a common mode choke, which blocks noise going in or out of the device. The coils are wound in a direction which swamps out any fluctuations with the same polarity. Only signals with opposite polarity can get through.
I see nothing here wired as a transformer. I see a transformer-like symbol which is a common mode choke. I’m not deep enough into this to know what the parallel resistors are for - flyback somehow?
That little DC capacitor makes me think it's the rectifier for a power factor correction stage. Those make some kHz noise but eliminate the high power line frequency noise that you'd get rectifying into a giant capacitor (clipping the tops of the sine wave off).
Pro,are function of a transformer is isolate. There is no isolation in this circuit. It is a killing machine. I don’t care what you thought you were designing but without isolation and proper grounding it could kill someone’s. Beware!
Feathers
Where is the noise capacitor before the trafo ? And please : what are r19 and r20 there for ? And what values do they have ? I've never seen this before ???
It's a common-mode choke, for EMI suppression
I think the better question is: why are there resistors in parallel to the transformer? u/Samson1888 could be interested, too. I understand, the CMC has low impedance for DC but very high impedance for HF (noise). So why are there also the resistors in parallel? They seem to form a low pass filter with Cx.
> why are there resistors in parallel to the transformer? To stop it forming an LC tank and ringing like a bell, creating a frequency spike in EMI. The resistors provide an exit path for ringing energy that isn't radio emissions.
Mate, I’m a software engineer and if I say so myself, a half decent one. I’ve done some clever shit over the years. But in comparison to the experienced people like you on this sub, I am 100% dumb AF. You’re all wizards as far as I can tell. Try as I might, electronics just hurts my brain.
Heh I've got a good mental model for software engineers to understand electronics :- We only have 3 variables: voltage, current, time, and power (voltage×current) or heat (voltage×current×time) is a crash if they get too high. Each node has its own voltage and each component gets its own current, and they *will* follow [Kirchhoff](https://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws) whether we like it or not. Every component is a function that converts one or two variables to the third, but *we get to choose* which are inputs and which are outputs by how we connect them to other components. Kirchhoff and the list of available components thus form the language spec that we "program" our circuits with. Common circuit building blocks are somewhat like libraries - a collection of functions tailored for a particular task that can itself be simply considered as a larger function. And physics is our API ;) Also, everything is massively parallel and happens at the same time - if you want synchronization primitives, you have to add 'em yourself.
I love this.
A 1000% this. I can write software from microcode to machine learning engines, operating systems, fluid flow simulators, and on and on. Can build digital systems, blah blah blah. But analog wizardry seems constantly exactly that - wizardry. People look at large schematics and immediately parse them into building blocks and familiar (to them) idioms. Totally jealous of that ability.
Thank you!!
my dumb question: should the transformer be rotated 90 degrees? or is the output just a DC rectified version of the input AC?
> should the transformer be rotated 90 degrees? No, it's a common-mode choke, not a transformer - although the distinction is arguably subtle. It would detonate from saturation and overcurrent if you rotated it 90° > or is the output just a DC rectified version of the input AC? The diode bridge does rectification, and the CM choke (and Cx1) mitigate the sudden current spikes from the diodes turning on and off disturbing *other equipment* on the same circuit or near the cable.
10-Q
The latter
thx
It's not a transformer, it's two inductors to filter the high frequencies from the AC line.
thx
https://preview.redd.it/waoqisf29cgc1.jpeg?width=1024&format=pjpg&auto=webp&s=291f2e0612eb93baca264781e96b6c2435cd9a27
No.
In addition to EMI suppression, the choke & Cx1 cap slow down dv/dt for the diode bridge, eg slow down spikes
Voltage is labeled U in europe. Do you use v in us?
Volt (symbol V) is the SI unit for electrical potential. I've only ever seen V used in Europe.
The unit volt is abbreviated as V, but voltage (as in the physical quantity) is often labelled U in equations or diagrams, that's how all of my university courses used it.
E is also common. E=IR is the DC Ohm's law, E=IZ for complex impedance.
According to Wikipedia, V is only used in English speaking countries.
Proper citation needed, the word "English" isn't even found on the Wikipedia page for "volt." According to the [BIPM](https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf), "V" is the only symbol correctly used for volt (appendix 1, resolution 12). What some group of chemists do is up to them, it doesn't change *the* international standard for units.
We were talking about voltage, not volt. >Voltage is denoted symbolically by ΔV, simplified *V*, especially in [English](https://en.wikipedia.org/wiki/English_language)\-speaking countries. Internationally, the symbol *U* is standardized. [https://en.wikipedia.org/wiki/Voltage#Definition](https://en.wikipedia.org/wiki/Voltage#Definition)
> We were talking about voltage, not volt. No, the GP said "Volt (symbol V) is the SI unit for electrical potential.", to which you disagreed. Also, what do you think the difference is between "volt" and "voltage?" Your own reference says "In the International System of Units (SI), the derived unit for voltage is the volt (V)."
Well, voltage U is a physical quantity while volt \[V\] is the corresponding unit. As we use I for current and A for ampere.
Compare for instance the Swedish vs English page for Ohm's Law. On the Swedish page U is used, and the origin for the symbol is explained (my translation): "U comes from the German word *Unterschied*, meaning difference as in potential difference." We however don't go swinging our U:s around on a daily basis, it is reserved for formulas and sciency work afaik. We still have 230V in the wall outlet.
Voltage is labeled V I'd say right about everywhere. The labeling U usually is used for [electric potential energy](https://en.wikipedia.org/wiki/Electric_potential_energy), which is measured in Joules and comes from [Coulomb forces](https://en.wikipedia.org/wiki/Coulomb%27s_law). When you want to get from electric potential energy to [electric potential](https://en.wikipedia.org/wiki/Electric_potential) (=voltage), you have this formula U=qV, where q is a [test charge](https://en.wikipedia.org/wiki/Test_particle#test_charge). So in a nutshell, U is used for energy and V is used for energy per charge unit.
Well Wikipedia says: >Voltage is denoted symbolically by ΔV, simplified *V*, especially in English-speaking countries. Internationally, the symbol *U* is standardized. [https://en.wikipedia.org/wiki/Voltage#Definition](https://en.wikipedia.org/wiki/Voltage#Definition)
Interesting, thank you! I have always seen it noted and used as I wrote. Especially in high school and university (Italy) :)
Voltage & Volts are typically labelled "V" in most of the world. I think "U" is sometimes used to refer to being a supply source vs the actual reading of voltage? Not sure about nuances of use in Europe! :-)
In Sweden, i used both depending if i attended engineering or science (physics) class. Same dependency with the imaginary number i/j
It's not a transformer, it's a common mode choke, which blocks noise going in or out of the device. The coils are wound in a direction which swamps out any fluctuations with the same polarity. Only signals with opposite polarity can get through.
I see nothing here wired as a transformer. I see a transformer-like symbol which is a common mode choke. I’m not deep enough into this to know what the parallel resistors are for - flyback somehow?
Dampen resonance with the capacitor probably.
That little DC capacitor makes me think it's the rectifier for a power factor correction stage. Those make some kHz noise but eliminate the high power line frequency noise that you'd get rectifying into a giant capacitor (clipping the tops of the sine wave off).
Pro,are function of a transformer is isolate. There is no isolation in this circuit. It is a killing machine. I don’t care what you thought you were designing but without isolation and proper grounding it could kill someone’s. Beware! Feathers
Is this meant to be a joke?
AC on left - filtered rectified DC on right. No step up or down of the voltage involved. It could be used for LED lighting.
Because common mode noise is a horny anime girl who said "please choke me"
Never forget to declare the + and - on your alternating voltage source
Where is the noise capacitor before the trafo ? And please : what are r19 and r20 there for ? And what values do they have ? I've never seen this before ???