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Variable current power supply with varying duty cycle

Raiyan

Apr 4, 2018
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I need to build a power supply whose voltage having limits 6v-45v and current ranging from 0.5- 5 amp can be changed according the need.
Plus it can also provide varying duty cycle
For example i want the power to be on for 23ms nd off for 2 ms , or on for 12ms nd off for 13ms and so , as per the testing requirement . How can i accomplish that? Any suggestions?
Can i use a solid state relay with any microcontroller to serve the latter part? By just just giving the on nd off commands in a loop after a certain delay in ms ?
 

ramussons

Jun 10, 2014
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I think these are 2 different projects.

The power supply is one and the "duty cycle" will be an oscillator with adjustable duty cycle, which in turn drives a "driver" or "bridge".
Is your "power supply" to give a fixed power pulses or free running ?
 

Raiyan

Apr 4, 2018
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I think these are 2 different projects.

The power supply is one and the "duty cycle" will be an oscillator with adjustable duty cycle, which in turn drives a "driver" or "bridge".
Is your "power supply" to give a fixed power pulses or free running ?

Yes, they are two different parts , u got that right . Once set the duty cycle it should be free running!
i have tried using LM317 as a voltage and current regulator , but not being able to incorporate the second part . Or i am trying to look for a single circuit that can do both the parts !
Please suggest something if you have an idea. How can i do it easily and efficiently
 

duke37

Jan 9, 2011
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I bought a dual power supply at a junk sale in 2009. This is analog and uses a pair of L200C chips, it controls voltage and current.
The L200C could perhaps be a basis of a switched mode supply
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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An LM317 is not going to do the job for you. It has a maximum input voltage less than your choice of output voltage (let alone the higher input voltage which would probably have to be 50V or so).

In addition, an LM317 had a maximum output current of 1A.

Even if you found a 5A adjustable regulator, at 6V at 5A the regulator would be dissipating more than 200W.

For the power supply itself, you would need a transformer rated at around 40V at 7A.

Then you would want to look at one of the many designs for current boost circuits for 3 terminal regulators. (Or better, roll your own with an op-amp, a voltage reference, and pass transistors).

Then you would want to add a circuit to provide a variable current limit (this is easier with a regulator not based on a 3 terminal regulator.

After you have that working, a circuit based on a 555, and a P channel mosfet can easily be designed to chop the output the way you want.
 

Raiyan

Apr 4, 2018
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An LM317 is not going to do the job for you. It has a maximum input voltage less than your choice of output voltage (let alone the higher input voltage which would probably have to be 50V or so).

In addition, an LM317 had a maximum output current of 1A.

Even if you found a 5A adjustable regulator, at 6V at 5A the regulator would be dissipating more than 200W.

For the power supply itself, you would need a transformer rated at around 40V at 7A.

Then you would want to look at one of the many designs for current boost circuits for 3 terminal regulators. (Or better, roll your own with an op-amp, a voltage reference, and pass transistors).

Then you would want to add a circuit to provide a variable current limit (this is easier with a regulator not based on a 3 terminal regulator.

After you have that working, a circuit based on a 555, and a P channel mosfet can easily be designed to chop the output the way you want.
I mistakenly mentioned LM317 actually it was LM138 because even 30V was enough for me and current specification was more crucial .
I calculated the max power dissipation would be 100W according to my usage limits and can use a heat sink for that.
I got most of the things you mentioned, i just need more elaboration and help in the last 555 timer part .
even if i got a controlled DC voltage and current supply , how can i turn it into a square wave supply with adjustable on and off time ??
 

Raiyan

Apr 4, 2018
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I bought a dual power supply at a junk sale in 2009. This is analog and uses a pair of L200C chips, it controls voltage and current.
The L200C could perhaps be a basis of a switched mode supply
I checked L200C but it doesn't meet my power requirements! Outputs upto 2Amps only
 

Hopup

Jul 5, 2015
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What kind of application are you going to use this power supply for?
 

Raiyan

Apr 4, 2018
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What kind of application are you going to use this power supply for?
Basically it is needed to power the Electromagnet . Its actually a research topic and we need to test different readings on different current and duty cycle
 
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