Singapore Expats Forum

Challenge of Voltage/Digital standards differences between USA and Singapore

Discuss about computers & Internet. Including mobile phones, home appliances & other gadgets. Read about Windows security risks or virus updates.
bgd
Editor
Editor
Posts: 1427
Joined: Wed, 25 Jul 2007

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby bgd » Tue, 04 Sep 2018 12:42 pm

So these are used to step down from say 240 to 120.

What about phone chargers? Are they step down transformers with an inverter? Given the number of stories about phone and charger fires, are we looking at auto transformers as being the likely cause?

I see the problem with the design. Can good quality materials get around the inherent problems, or would the cost increase negate the advantage (cost) of an auto transformer?

And thanks for the very clear explanation.

User avatar
Strong Eagle
Moderator
Moderator
Posts: 11172
Joined: Sat, 10 Jul 2004
Location: Off The Red Dot
Contact:

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby Strong Eagle » Tue, 04 Sep 2018 8:09 pm

bgd wrote:So these are used to step down from say 240 to 120.

What about phone chargers? Are they step down transformers with an inverter? Given the number of stories about phone and charger fires, are we looking at auto transformers as being the likely cause?

I see the problem with the design. Can good quality materials get around the inherent problems, or would the cost increase negate the advantage (cost) of an auto transformer?

And thanks for the very clear explanation.


Modern phone chargers (and most low voltage power packs these days) no longer use a transformer. Instead, they use circuits containing zener diodes, a curious electronic component which allows the designer to take just a slice of the input AC sine wave and output it as a low voltage for USB, etc.

Like all electronic components, zener diodes (and the associated circuit components) have maximum working values, and they produce heat. Cheaply made devices, with insufficient provision for cooling components, or use of components that run close to their maximum capabilities, increase the risk of fire, shorts, and meltdowns.

You are correct, use properly sized materials, of good construction, with appropriate heat sinks. Of course, this costs money and takes up more space.

User avatar
PNGMK
Governor
Governor
Posts: 5824
Joined: Thu, 21 Mar 2013
Location: Sinkapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby PNGMK » Tue, 04 Sep 2018 10:58 pm

Actually they are switched PSUs I think. Extremely high frequency down verters. AC rectified to DC and then switched into a extremely high frequency wave form and transformed down to a voltage and then rectified again. The extremely high switching frequency allows for a tiny transformer and full isolation.
IANAL. IANACPA. IANA Teacher.
Arrested? Lawyer Up
International School job? School website or http://www.ISS.edu
School advice? Avoid for profit schools
Tax advice? CPA
Pay me $5k for 100% success filling in PR form!

User avatar
Strong Eagle
Moderator
Moderator
Posts: 11172
Joined: Sat, 10 Jul 2004
Location: Off The Red Dot
Contact:

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby Strong Eagle » Wed, 05 Sep 2018 2:42 am

PNGMK wrote:Actually they are switched PSUs I think. Extremely high frequency down verters. AC rectified to DC and then switched into a extremely high frequency wave form and transformed down to a voltage and then rectified again. The extremely high switching frequency allows for a tiny transformer and full isolation.


I learn something new everyday. Thank you. DC to DC converters (variations of the buck circuit) are used for high efficiency voltage changes (high to low).

I see that non-isolated converters are used for small voltage changes while large voltage changes use an isolation transformer. I also see that DC to DC converters are tricky in that overall circuit capacitance and inductance can affect the performance of the device.

This means I now need to go break open a couple of old chargers to see what is inside them. For example, I bought a cheap replacement charger for an old HP laptop. The old charger weighed in a a couple of pounds, clearly a traditional transformer. The new one (same wattage) weighs in at a few ounces.

I thought it was simply a transformerless full wave rectified, zener diode voltage controlled device, as below. It would be cheaper but could certainly lead to some shocking conclusions if the zener diode were to fail. Now I need to see if it at least has a transformer of some sort in it.

Image

User avatar
PNGMK
Governor
Governor
Posts: 5824
Joined: Thu, 21 Mar 2013
Location: Sinkapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby PNGMK » Wed, 05 Sep 2018 6:46 am

That's why people die when their cheap Chinese knock off apple charge for their phone dies. No isolation and the ground of the case and ear buds goes high potential to earth. There are cases where their ears are burned from the shock as the common audio ground goes high voltage.
IANAL. IANACPA. IANA Teacher.
Arrested? Lawyer Up
International School job? School website or http://www.ISS.edu
School advice? Avoid for profit schools
Tax advice? CPA
Pay me $5k for 100% success filling in PR form!

User avatar
Strong Eagle
Moderator
Moderator
Posts: 11172
Joined: Sat, 10 Jul 2004
Location: Off The Red Dot
Contact:

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby Strong Eagle » Wed, 05 Sep 2018 10:00 am

Totally off topic, and... since you mentioned high frequency switching... the class D amplifier is quite a cool beast... a non-linear amplifier that creates a pulse waveform, whose length is proportional to the voltage of the input signal. Non-intuitive to me but pretty slick.

User avatar
PNGMK
Governor
Governor
Posts: 5824
Joined: Thu, 21 Mar 2013
Location: Sinkapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby PNGMK » Wed, 05 Sep 2018 10:52 am

I've never been much of an amp / audiophile guy. Bad hearing etc...
IANAL. IANACPA. IANA Teacher.
Arrested? Lawyer Up
International School job? School website or http://www.ISS.edu
School advice? Avoid for profit schools
Tax advice? CPA
Pay me $5k for 100% success filling in PR form!

User avatar
Strong Eagle
Moderator
Moderator
Posts: 11172
Joined: Sat, 10 Jul 2004
Location: Off The Red Dot
Contact:

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby Strong Eagle » Wed, 05 Sep 2018 11:36 am

PNGMK wrote:I've never been much of an amp / audiophile guy. Bad hearing etc...


I have CHS syndrome myself... but I do like a sound system that puts out the bass. 44 Hz is the lowest note on a bass guitar. I've got a woofer that will make 32 Hz at 3 dB rolloff... amazing how much more expensive things get to get down even a few more Hz.

User avatar
x9200
Moderator
Moderator
Posts: 9331
Joined: Mon, 07 Sep 2009
Location: Singapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby x9200 » Fri, 28 Sep 2018 9:16 pm

I am thinking of buying an isolation transformer but looking for a cheaper alternatives to what PNGMK recommended earlier.
I found this one which seems the right thing (except for no stock and I see no drawing) but would appreciate your opinion:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/

And then, there is this one (a few of this type):
https://docs-apac.rs-online.com/webdocs ... 51be93.pdf
even cheaper, but I sort of don't follow the idea of having the output winding split and grounded in the middle. What is this 55V about? Safety related to limit max voltage to 55?

And another one:
https://sg.rs-online.com/web/product/sa ... s/2604272/

User avatar
PNGMK
Governor
Governor
Posts: 5824
Joined: Thu, 21 Mar 2013
Location: Sinkapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby PNGMK » Fri, 28 Sep 2018 11:56 pm

x9200 wrote:I am thinking of buying an isolation transformer but looking for a cheaper alternatives to what PNGMK recommended earlier.
I found this one which seems the right thing (except for no stock and I see no drawing) but would appreciate your opinion:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/

And then, there is this one (a few of this type):
https://docs-apac.rs-online.com/webdocs ... 51be93.pdf
even cheaper, but I sort of don't follow the idea of having the output winding split and grounded in the middle. What is this 55V about? Safety related to limit max voltage to 55?

And another one:
https://sg.rs-online.com/web/product/sa ... s/2604272/


What are you trying to do here? These are isolation for safety (but do not transform the voltage up or down). You use these on wet or dangerous sites where there is a risk of electrocution.
IANAL. IANACPA. IANA Teacher.
Arrested? Lawyer Up
International School job? School website or http://www.ISS.edu
School advice? Avoid for profit schools
Tax advice? CPA
Pay me $5k for 100% success filling in PR form!

User avatar
x9200
Moderator
Moderator
Posts: 9331
Joined: Mon, 07 Sep 2009
Location: Singapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby x9200 » Sat, 29 Sep 2018 5:50 am

PNGMK wrote:
x9200 wrote:I am thinking of buying an isolation transformer but looking for a cheaper alternatives to what PNGMK recommended earlier.
I found this one which seems the right thing (except for no stock and I see no drawing) but would appreciate your opinion:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/

And then, there is this one (a few of this type):
https://docs-apac.rs-online.com/webdocs ... 51be93.pdf
even cheaper, but I sort of don't follow the idea of having the output winding split and grounded in the middle. What is this 55V about? Safety related to limit max voltage to 55?

And another one:
https://sg.rs-online.com/web/product/sa ... s/2604272/


What are you trying to do here? These are isolation for safety (but do not transform the voltage up or down). You use these on wet or dangerous sites where there is a risk of electrocution.

Why do you say they don't transform down if the spec says they all do? Did you read the linked information and looked at the diagram in the brochure?

User avatar
Strong Eagle
Moderator
Moderator
Posts: 11172
Joined: Sat, 10 Jul 2004
Location: Off The Red Dot
Contact:

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby Strong Eagle » Sat, 29 Sep 2018 11:57 am

x9200 wrote:I am thinking of buying an isolation transformer but looking for a cheaper alternatives to what PNGMK recommended earlier.
I found this one which seems the right thing (except for no stock and I see no drawing) but would appreciate your opinion:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/

And then, there is this one (a few of this type):
https://docs-apac.rs-online.com/webdocs ... 51be93.pdf
even cheaper, but I sort of don't follow the idea of having the output winding split and grounded in the middle. What is this 55V about? Safety related to limit max voltage to 55?

And another one:
https://sg.rs-online.com/web/product/sa ... s/2604272/


Any or all of those transformers appear to be center tap to earth. No issue there. That is a design which enables the secondary winding to be grounded because the exact middle of the coil is 0 volts, relative to the ends. You get 110 volts across the ends because when one side is +55 volts, the other side is -55 volts.

All of them are step down transformers. It seems like two of them have continuous power ratings while the PDF one is designed for higher draw, intermittent use.

If you're not planning on being in damp areas, you don't need the center tap transformer but it doesn't hurt anything. What are you planning on running on the other end?

User avatar
x9200
Moderator
Moderator
Posts: 9331
Joined: Mon, 07 Sep 2009
Location: Singapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby x9200 » Sat, 29 Sep 2018 12:22 pm

Thanks SE.
~120W self-freezing ice cream making machine. It's TEC (Peltier) based so no compressor/electric motor except perhaps a cooling fan to remove the heat.

Nb. I don't understand why this one:
https://sg.rs-online.com/web/p/safety-s ... s/1226711/

is so cheap. It's rated 2k2W and it is cheaper than the 750W one:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/

User avatar
PNGMK
Governor
Governor
Posts: 5824
Joined: Thu, 21 Mar 2013
Location: Sinkapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby PNGMK » Sun, 30 Sep 2018 8:49 am

x9200 wrote:
PNGMK wrote:
x9200 wrote:I am thinking of buying an isolation transformer but looking for a cheaper alternatives to what PNGMK recommended earlier.
I found this one which seems the right thing (except for no stock and I see no drawing) but would appreciate your opinion:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/

And then, there is this one (a few of this type):
https://docs-apac.rs-online.com/webdocs ... 51be93.pdf
even cheaper, but I sort of don't follow the idea of having the output winding split and grounded in the middle. What is this 55V about? Safety related to limit max voltage to 55?

And another one:
https://sg.rs-online.com/web/product/sa ... s/2604272/


What are you trying to do here? These are isolation for safety (but do not transform the voltage up or down). You use these on wet or dangerous sites where there is a risk of electrocution.

Why do you say they don't transform down if the spec says they all do? Did you read the linked information and looked at the diagram in the brochure?


I missed the step down part (it's at the bottom). Apologies.
IANAL. IANACPA. IANA Teacher.
Arrested? Lawyer Up
International School job? School website or http://www.ISS.edu
School advice? Avoid for profit schools
Tax advice? CPA
Pay me $5k for 100% success filling in PR form!

User avatar
PNGMK
Governor
Governor
Posts: 5824
Joined: Thu, 21 Mar 2013
Location: Sinkapore

Re: Challenge of Voltage/Digital standards differences between USA and Singapore

Postby PNGMK » Sun, 30 Sep 2018 8:52 am

x9200 wrote:Thanks SE.
~120W self-freezing ice cream making machine. It's TEC (Peltier) based so no compressor/electric motor except perhaps a cooling fan to remove the heat.

Nb. I don't understand why this one:
https://sg.rs-online.com/web/p/safety-s ... s/1226711/

is so cheap. It's rated 2k2W and it is cheaper than the 750W one:
https://sg.rs-online.com/web/p/safety-s ... s/1237376/


No idea. Maybe a more popular model and made in volume hence cheaper? There's no apparent difference in the specs (apart from load rating) or safety standards it meets.
IANAL. IANACPA. IANA Teacher.
Arrested? Lawyer Up
International School job? School website or http://www.ISS.edu
School advice? Avoid for profit schools
Tax advice? CPA
Pay me $5k for 100% success filling in PR form!


  • Similar Topics
    Replies
    Views
    Last post

Return to “Computer, Internet, Phone & Electronics”

Who is online

Users browsing this forum: No registered users and 2 guests