Voltage value of digital pwm

Status
Not open for further replies.
S

spartekus

Member level 5
Joined
May 27, 2010
Messages
81
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Location
Duisburg, Germany
Visit site
Activity points
1,918
Hi all,

there is something i am curious about. i couldnt find it.
does anyone know, which values can a digital pwm signal have? just 0-5?

how can i creat 7 or 7.5 volt pwm signal?

when we prefer analog pwm and when we choose digital pwm?

thanks in advance
regards
 

0 to 5 is nothing, but just the voltage your microcontroller is working on. You can use 3 volt. Then your pwm will be 0 to 3.

You can use microcontroller with any voltage and drive a transistor with source of 7 or 7.5 volt, or any voltage you like.

Analog can be used for sine wave inverters, audio signals, RF, etc. Digital pwm are generally used for digital communication, but also can be used in inverters, RFs, etc. It is completely depends on your requirements....
 

hi
thanks for your asnwer,
what about if i want to give 7 volt pwm from gate of mosfet, how can i make 5 volt pwm signal to 7 or 4 volt pwm signal?
thanks
 

You can't make 7 volt pwm directly from the controller. It is only possible if the controller can work on such a high voltage.
However, you can drive a mosfet or any other transistor with its source voltage of 7 volt. You will get the same pwm in high voltage. Refer to this diagram.....

 

PWM means pulse width modulation
what you are getting in a given time or frequency.
Mark and space ratio.
duty cycle.
percentage of on time and off time of any high frequency.
consider I khz frequency, one cycle time is 1/1000 means 1 msec or 1000 usec.
if in its time signal is on for 100 usec and off 900 usec you will gett less power as it is only 100 duty cycle and
vise vers if on time is 900 usec and off time is 100 usec it is 900 duty cycle is 90% more power.
 

thanks for your asnwers,
according to mosfet characteristic, if we make gate voltage higer, than more current can pass throug the mosfet. thats way i asked if we can make 7 volt pwm.
on converter design, it says about inductor value, duty cycle etc. but how can we arrange the power that we want to supply to our load? i thought it is by changing pwm voltage.

thanks
 

according to mosfet characteristic, if we make gate voltage higer, than more current can pass throug the mosfet.
Click to expand...
Yes. You can control the supply through gate, but remember, gate is highly sensitive to control. This is why PWM is used with different dutycycle.

The maximum power to your load completely depends on the power supply of your mosfet. You have to see if the supply can give the required current with required voltage. Now if you want to reduce the current supply, then you have to provide PWM with low duty cycle to the gate. You no need to change the PWM "voltage", rather change the PWM "duty cycle" for the mosfet gate. This way you can control the power supply to the load.


What exactly do you want to achieve????
 

thanks, i got it,
i just had thought, we have to change current to make power of load higher or lower, and i thought to do it by changing gate voltage.
but i see we do it by changing voltage of current. no need to have more current, it wouldnt be healty for circuit anyway.

thanks a lot.
 

but i see we do it by changing voltage of current.
Click to expand...

I didn't understood that. Voltage & current are different entities. You are not exactly changing the voltage to the gate. You are changing the pulse duration to keep the gate on for a certain time. Do you know how PWM works???
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…