Voltage Regulator question.

[mazur50]

My question is with a LM317 no matter what the voltage it will output what ever it is set at as long as it is higher then the set voltage. My question is how can i do this I need to be able to handle like 10 amps. but dont want to piggiy back them. Will PWM do the same thing the out put stay the same voltage no matter what the AMPs are.

let me know thanks.

Mike

[BushmanLA]

Yes, a PWM type regulator also known as 'switch mode power supply' will take some high voltage source and drop it to the voltage you need. There are some limitations of course. The regulator manufacturer will tell you what the acceptable input voltage range is, how many amps it can sustain, etc.

In general there are two types of voltage regulators; switch mode and linear.
Linear regulators use semiconductors in a feedback system to regulate the voltage output.
Switch mode regulators use a variety of methods but they pretty boil down to switching the input voltage on and off really fast, and varying the duty cycle so that the desired output voltage is achieved.

Linear regulators are usually smaller and cheaper. (although this becoming less true these days)
Linear regulators are usually much much less efficient and the higher the input voltage is from the desired output, the worse it is. Thus they generally have low amp output, 2 Amps and then you better have a heat sink on it.

Switch modes are much more efficient, but they are noisy compared to a linear type. This is because they are turning the output on and off constantly and you can never filter this out 100%. 20mV of noise is usually what you can expect from a decent one.

Head on over to dimension engineering and check out their regulators, I never used one myself but every one else says they do well.

Edit: I don't think they have any 10Amp jobs there. What is your application? Maybe we could give you some suggestions.

[Chippie]

Will PWM do the same thing the out put stay the same voltage no matter what the AMPs are.

let me know thanks.

Mike

The output will remain fairly constant to a point....If you hit the max duty cycle of the pwm and increase the load, ultimately the output voltage will fall, hopefully the psu will have some form of protection ....and shutdown...

[mazur50]

So what your saying is if i have a PWM circuit set to give me lets say 5volts out. then if i Feed 10 in or 12 or 15 in. it should still be 5 volts out no matter what input voltage is.

[mazur50]

I have a tire truer that i want to keep at 5 volts no matter the amps. i have seen a peak of about 8amps.

[BushmanLA]

So what your saying is if i have a PWM circuit set to give me lets say 5volts out. then if i Feed 10 in or 12 or 15 in. it should still be 5 volts out no matter what input voltage is.


Thats pretty much the idea. Basically if you can find an 8 Amp BEC you will be good to go.

[Almaz]

Sometimes it is cheaper to buy one instead of making one. 8amp-15amp voltage regulator UBEC $20 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6233

[TMorita]

So what your saying is if i have a PWM circuit set to give me lets say 5volts out. then if i Feed 10 in or 12 or 15 in. it should still be 5 volts out no matter what input voltage is.

No. If you have fixed duty cycle PWM generator, then the output voltage will not be constant if the input voltage changes.

Toshi

[mazur50]

I have a pot to change my duty cycle it is a basic 555 timer setup. will that work or what kind of changes do i need to make.

[TMorita]

I have a pot to change my duty cycle it is a basic 555 timer setup. will that work or what kind of changes do i need to make.

You probably need to hire someone to change the potentiometer setting every time the input voltage changes.

Toshi

[mazur50]

what can i use to monitor the duty cycle and the input voltage.

[TMorita]

what can i use to monitor the duty cycle and the input voltage.

Your real question is actually: "How do a I design a switching power supply?"

There are many textbooks on switching power supply design available. Try checking Amazon.

Toshi

[Chippie]

Have a look at the application circuits for the TL494....That is used in many computer power supplies...


Essentially the pwm is changed by sampling the output voltage...

[mazur50]

Do you have any circuits on how i might be able to add it to my circuit.