Switch mode power supply w/ Voltage divider

argonrepublic · 2nd August 2011, 03:17 AM

I have a power supply (ac adapter) It is 19 Volts and I need 16 Volts. I don't fully understand voltage dividers. I could make a voltage divider but the power supply is 90 Watts. I am assuming the a 1 watt resistor won't work or is the resisto wattage base on the wattage of the resistance?

sawreyrw · 2nd August 2011, 03:32 AM

No, using a voltage divider would not be very practical. However, a simple series pass regulator would be a good solution and the losses wouldn't be too bad.

geraldfryjr · 2nd August 2011, 03:36 AM

It depends on how much current draw is required that detrimines resistor disiapation in watts. jer

gootee · 2nd August 2011, 03:42 AM

Yeah, 90 Watts is the maximum it should put out, if you let it. Your total resistance value would determine the current, and thus the power ratings required for the resistors. If you only need a watt or so, it could be done that way. But check out the LM3xx (and other) linear three-terminal regulators, at national.com (and others). It is a much easier and better way.

2nd August 2011, 03:17 AM	#1
argonrepublic diyAudio Member Join Date: Apr 2005 Location: Simcoe Ont	Switch mode power supply w/ Voltage divider I have a power supply (ac adapter) It is 19 Volts and I need 16 Volts. I don't fully understand voltage dividers. I could make a voltage divider but the power supply is 90 Watts. I am assuming the a 1 watt resistor won't work or is the resisto wattage base on the wattage of the resistance?

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2nd August 2011, 03:32 AM	#2
sawreyrw diyAudio Member Join Date: Apr 2006 Location: Minnesota	No, using a voltage divider would not be very practical. However, a simple series pass regulator would be a good solution and the losses wouldn't be too bad.

2nd August 2011, 03:36 AM	#3
geraldfryjr diyAudio Member Join Date: Feb 2008 Location: Jackson,michigan	It depends on how much current draw is required that detrimines resistor disiapation in watts. jer

2nd August 2011, 03:42 AM	#4
gootee diyAudio Member Join Date: Nov 2006 Location: Indiana Blog Entries: 1	Yeah, 90 Watts is the maximum it should put out, if you let it. Your total resistance value would determine the current, and thus the power ratings required for the resistors. If you only need a watt or so, it could be done that way. But check out the LM3xx (and other) linear three-terminal regulators, at national.com (and others). It is a much easier and better way.

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