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How to design a power supply that change current and voltage using comparators?

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wolf12

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How to design a power supply that change current and voltage using comparators? About 0 to 50 volts and 0 to 3 Amperes.
I dont know how you use comparators either. A big explanation will be very helpful.
 

Referring to your previous thread https://www.edaboard.com/threads/212949/, you have been asking how to design a power supply. Why do you think, that comparators should be used for it? They may be possibly used for special purposes, e.g. overcurrent shutdown. But they are not substantial for power supply design.
 

Referring to your previous thread https://www.edaboard.com/threads/212949/, you have been asking how to design a power supply. Why do you think, that comparators should be used for it? They may be possibly used for special purposes, e.g. overcurrent shutdown. But they are not substantial for power supply design.

I've heard about a feedback system, I want to make one. You monitor the output of the powersupply with a comparator, if the voltage is 5.2V and when we have adjusted it to 5V, it sees the additional 0.2V and adjusts a resistance or something to make it 5V. This is power electronics right? Can you suggest me a book or a website to learn how to do this.
 

Your description is of an error amplifier, an opamp (or a discrete circuit) can do a better job than a comparator because the output can have different levels to drive the control element (transistor), a comparator can only have the output on or off.

Take a look at these

**broken link removed**

On Semiconductors Linear & Switching Voltage Regulator Handbook. HB206/D

Alex
 

I have seen comparators used in motor control circuits for PWM power control, might be what you are thinking of for big DC supplies.
In some integrated chips I've been looking at recently, the comparators are a big part of the internal circuit diagram. In these, if the load current goes over a certain ammount and causes the voltage over a low resistance sense-resistor to go above a (set-able normally) reference voltage it will cut the current off completely until a small capacitor (value sets speed) has discharged, giving the current time to drop and then it'll try full whack again, over and over and over, kHz. They are so efficient in power electronics because the quick switching times mean there is rarely any voltage or current across the chip, just one or the other, so little power is wasted....

If you aren't worried about noise and a bit of a ripple on the output they're a good idea , they are available in various power levels depending on what you buy, all having similar characteristics. It would probably be possible do a similar idea with voltage if you can build it but I'm not 100% on the use of it that way..

Neal:)
 

I have seen comparators used in motor control circuits for PWM power control, might be what you are thinking of for big DC supplies.
The original poster has clarified in his second post, that he's looking for a basic regulated power supply. Suggesting switching mode circuits or particularly self-oscillating "hysteretic" switchers effectively means trying to run before one can walk. Don't forget, that switching mode circuits also implement a feedback structure, that can (and should) be analyzed in terms of linear control theory in a first order. You can derive important parameters like loop bandwith, characteristic frequency, phase margin, stability and transient response from a time continuous representation of the switcher circuit. Understanding the theory is however complex enough for a linear controller, I think.

The literature suggested by Alex has some good material to understand the linear regulator basics.
 

Sorry, I was looking at the question of why they'd thought a comparator may be used, no realising I was on completely the wrong tack. Appologies the [q]I've heard about a feedback system, I want to make one.[/q] made me think was walking already, sorry.
NEal
:)

although i did think
[q] You can derive important parameters like loop bandwith, characteristic frequency, phase margin, stabilty and transient response from a time discrete representation of the switcher circuit. Understanding the theory is however complex enough for a linear controller, I think.[/q]
may be a bit forward for a "walker".
 
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For designing power supply with voltage and current control you can use TOP switch with feedback system. The feedback system will give control signal to the control pin of top switch by which the output voltage and current is limited to set value. this page will be helpful i think http://www.powerint.com/sites/default/files/PDFFiles/der227.pdf
 

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