HELP with PWM(pulse width modulator)

[tech_vaibhav_eee]

whats the diff. btw the following
variable duty cycle pwm...
variable frequency pwm...
variable frequency and duty cycle pwm...????

also,what r high side and low side pwm used in psoc???

 

[audioguru]

PWM is the duty-cycle changing. The frequency might also change but it does not need to change. Changing the frequency without changing the duty-cycle is not PWM.

I don't know what is high side and low side PWM. An h-bridge has a high side and a low side.
I don't know what is PSOC. The letters could be anything.

 

[tech_vaibhav_eee]

thnks....
psoc(program system on chip) is a product of cypress semiconductors which has a microcontroller together with many other evices like adc , comparators, sensors ,...
what is the difference with/without variable frequency???

 

[audioguru]

Most PWM systems do not change the frequency because a low frequency is bad and a high frequency is bad.

 

[tech_vaibhav_eee]

hi,
so , if i hav to run a dc motor of certain voltage , say 12v , i can take analog voltage which averages to 12volt , connect it to a pwm and the output may b connected to the motor....will it work????
eliminators available in the market does the same thing...do they work on same principle???

 

[audioguru]

With a 12V supply and a 12V motor then 100% duty-cycle from PWM will result in full power. But the PWM circuit might have some loss.
50% duty-cycle will result in almost half power but good torque.
10% duty cycle will result in low power and not bad torque.

 

[Miles Prower]

whats the diff. btw the following
variable duty cycle pwm...

This is the true PWM. Consider it FM with a square wave carrier as opposed to a sinusoidal carrier.

variable frequency pwm...

This would be more appropriately referred to as "pulse position modulation". It's derived from PWM.

 

[sniper007]

Most PWM systems do not change the frequency because a low frequency is bad and a high frequency is bad.

Why high frequency is not appropriate ?

 

[audioguru]

High frequency reduces the current in an inductive motor.
The switching device gets hot at high frequency.