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There are many ICs that are designed to regulator a switching power supply. LT (linear Tech) and AD (Analog Devices) both makes a number of them. Check their web sites for data sheets and app notes. The most difficult part of the switching power supply design is the transformer. There are also adjustable linear regulators. The LM317 is the most common but can only supply 1A. However, there is a higher current version or a pass transistor can be added to the LM317 to supply higher current. Google the data sheet for details.
I want to build a adjustable power supply system that can adjust output voltage using a pwm channel of a micro-controller.
output requirement is 0-15v and about maximum 3A.
and should be a linear regulator (as I'm still learning switching regulators and have no good idea about them)
basic idea is adjust the output by varying pulse width and feedback output voltage to the same micro-controller to keep output constant.
Any idea how to achieve this? any regulator IC I can use for this?
Hi,It can be done with a suitable high PWM frequency and an integrator (plus glue), but it's much easier with a D/A-C.
PWM controling a LM317 http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=33798DAC control adjustable power supplyhttp://www.linuxfocus.org/English/June2005/article379.shtmlhttp://www.linuxfocus.org/English/September2005/article389.shtmlhttp://www.electro-tech-online.com/microcontrollers/96957-digital-control-voltage-using-lm317.htmlhttp://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1277815328
In operation, the LM317 develops a nominal 1.25V reference voltage, VREF, between the output and adjustment terminal. The reference voltage is impressed across on the current set resistor R1 connected between the adjustment terminal and the output terminal (usually 240 ohms) and, since the voltage across R1 is constant and the current also constant, the output voltage will be voltage divider between the R1 and the output set resistor R2 or Radj.If you simply give a reference voltage to adjustment pin, there will be no error voltage feed back from the output pin then the internal comparator will not able to function as the current follow through R1 will not be constant.
would this work? the idea is the higher the pwm frequency the closer the Transistor's IN voltage would get to 0V. Thus decreasing the current through the resistor and increasing the transistors resistance
That circuit will just cause the LM317 to go between 1.2V and the maximum voltage. You need to add an integrator and then use a FET as a variable resistor.The circuit is rather simple so do wire it up and give it a try. Just use an O'scope the monitor the input and output and use a load resistor instead of an expensive processor during testing. If nothing else you'll learn something.
Yes, I am replying to the last circuit posted (WhomBom's).
That circuit will just cause the LM317 to go between 1.2V and the maximum voltage. You need to add an integrator and then use a FET as a variable resistor.
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