Currrent calculation formula for pwm signal

[er.rajar]

Hello,

What is formula for calculating the current for PWM signal?

input parameters:

PWM frequency : 45 KHz ( Duty cycle : 50 %)
Amplitude : 24 V
Load : Inductive ( Resistance value : 7 ohm)

kindly help me for the above question

 

[BradtheRad]

The charging curve is governed by the L/R inductive time constant.

Current will reach its maximum Amperage after 5 time constants (customary figure). It will reach 63% of maximum after 1 time constant.

In your example... Maximum Amperage is equal to 24 V divided by 7 ohms (3.43 A). Voltage is applied for 1/90,000 of a second. (11 uSec)

In 11 uSec, current will reach a proportionate fraction of 3.43A, as 11 uSec is in ratio to the inductive time constant. Although the curve is not straight, we pretend it is for the sake of ease.

 

[FvM]

The specification doesn't talk about inductance respectively time constant. It also doesn't describe the PWM circuit exactly.

So you can only calculate average current under the assumption that the load voltage is switched between 24 V and 0 V, e.g. by a synchronous switching half bridge. Under this assumption, the average voltage across the load is 12V and thus the average current 12/7 A.