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I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
On Friday, April 14, 2023 at 9:59:07â¯AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
On Friday, April 14, 2023 at 9:04:12â¯AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07â¯AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
Mikek
On Friday, April 14, 2023 at 9:04:12â¯AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07â¯AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
On Friday, April 14, 2023 at 10:07:39â¯AM UTC-4, Lamont Cranston wrote:
On Friday, April 14, 2023 at 9:04:12â¯AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07â¯AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
Yeah- the controller chip usually has a reference in it, and the output voltage is scaled up from that via a resistor voltage divider. You want to change that voltage divider. But there could be hazards, your feeding more output into the error amplifier feedback loop and it may become unstable, and some of the other performance characteristics may degrade. You may lose various kinds of protections against destruction too. 12/19 is a pretty big reduction, it may not be enough to operate the externals to the regulator, things like biases. Save yourself the headache and buy a 12V supply.
Mikek
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
On Friday, April 14, 2023 at 9:04:12â¯AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07â¯AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
I power all sorts of stuff off random laptop bricks, mostly the
old-fashioned ones with the 5/2.5 mm coaxial connections.
One good approach for light-duty use is to buy an eBay buck module rated
at about three times your expected maximum current. (Chinese amps are
on the small size.)
On Friday, April 14, 2023 at 10:07:39?AM UTC-4, Lamont Cranston wrote:
On Friday, April 14, 2023 at 9:04:12?AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07?AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
The whole of the power supply is designed for providing 19V. If you try to change that to 12V, you would need to go through the design process again, to assure it will work correctly.
To answer your question, there is typically a resistor divider that feeds a portion of the output voltage to the controller chip. This is compared to an internal reference (or it could be a separate reference, but that\'s not important). To change the output voltage, you change one or both of those resistors. If the circuit has capacitors in parallel with the resistors, make sure you get the data sheet for the controller part and adjust the capacitors if required.
Why not just buy a 12V supply (there\'s plenty of them around)? If you buy off eBay or Alibaba, be sure to derate the power output by 2 or 3 or 4x.
On Fri, 14 Apr 2023 08:41:38 -0700 (PDT), Ricky
gnuarm.del...@gmail.com> wrote:
On Friday, April 14, 2023 at 10:07:39?AM UTC-4, Lamont Cranston wrote:
On Friday, April 14, 2023 at 9:04:12?AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07?AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
The whole of the power supply is designed for providing 19V. If you try to change that to 12V, you would need to go through the design process again, to assure it will work correctly.
To answer your question, there is typically a resistor divider that feeds a portion of the output voltage to the controller chip. This is compared to an internal reference (or it could be a separate reference, but that\'s not important). To change the output voltage, you change one or both of those resistors. If the circuit has capacitors in parallel with the resistors, make sure you get the data sheet for the controller part and adjust the capacitors if required.
Why not just buy a 12V supply (there\'s plenty of them around)? If you buy off eBay or Alibaba, be sure to derate the power output by 2 or 3 or 4x.
I highly doubt that a 19V laptop is going to run at 12V.
You MIGHT get lucky ?
I would bet it won\'t work.
On Fri, 14 Apr 2023 08:41:38 -0700 (PDT), Ricky
gnuarm.del...@gmail.com> wrote:
On Friday, April 14, 2023 at 10:07:39?AM UTC-4, Lamont Cranston wrote:
On Friday, April 14, 2023 at 9:04:12?AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07?AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
The whole of the power supply is designed for providing 19V. If you try to change that to 12V, you would need to go through the design process again, to assure it will work correctly.
To answer your question, there is typically a resistor divider that feeds a portion of the output voltage to the controller chip. This is compared to an internal reference (or it could be a separate reference, but that\'s not important). To change the output voltage, you change one or both of those resistors. If the circuit has capacitors in parallel with the resistors, make sure you get the data sheet for the controller part and adjust the capacitors if required.
Why not just buy a 12V supply (there\'s plenty of them around)? If you buy off eBay or Alibaba, be sure to derate the power output by 2 or 3 or 4x.
I highly doubt that a 19V laptop is going to run at 12V.
You MIGHT get lucky ?
I would bet it won\'t work.
On Friday, April 14, 2023 at 9:04:12â¯AM UTC-5, Fred Bloggs wrote:
On Friday, April 14, 2023 at 9:59:07â¯AM UTC-4, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
No. That question is beyond unbelievable.
Well not really unbelievable.
Is there reference against which the output voltage is compared to in a switching power supply?
Mikek
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
On 14/04/2023 14:59, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
Given that 19V is a *very* common laptop supply voltage, I wouldn\'t be
surprised if they used a fixed 19V supply chip.
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
On 14/04/2023 14:59, Lamont Cranston wrote:
I have a Toshiba 3.4A, 19V laptop power supply that I want to reduce to 12V.
Is it as simple as finding a 19V zener and changing it to a 12v zener?
Thanks, Mikek
Given that 19V is a *very* common laptop supply voltage, I wouldn\'t be
surprised if they used a fixed 19V supply chip.
I\'m just going to use the 19V to run the heaters, and add a 12V regulator to power the Arduino and the 12V relays I have.
I have tested with all 5 heaters in series on 19V (6 Watts) it is not enough heat, so I\'ll probably go with the 30 Watt configuration using four heat strips.
Although if I parallel two and parallel 3, then put those in series, it is 31 watts and I can have a little better heat distribution. ( I have 5 heat strips)
Mikek