Question

1. What is needed for providing an inductor at the output of a SMPS? List out the important requirements of the inductor at the output of a SMPS power supply.

2. Analogue PWM wave form can be created by combining which of the following:

1. A saw- tooth waveform and a square wave form
2. A saw- tooth waveform and a sinusoidal wave form
3. A saw- tooth waveform and a rectangular wave form
4. A sinusoidal wave form and a rectangular wave form
5. A sinusoidal wave form and a square wave form

Answer 1

1)

Whenever we need a constant output voltage.. even in a varying input, by fluctuating the duty cycle.. we use inductors in SMPS. The the inductor character, which is current flow through an inductor cannot be changed simultaneously.. so in order to get stabilized output current, we made usage of inductors in switching mode power regulators.

Important requirements of inductor at the output of a SMPS power supply are..

**I(sat), that is current rate at which core get saturated, should be higher than the peak current rate of load connected.
ie...I(pk)= (Iout + I(ripple)/2)

**Ripple current value between 10 % to 30% of maximum load should be provided..in order to keep smooth functioning between inductor and capacitor size in SMPS.

**For ensuring the continuous mode of operation, ripple current value of inductor should be less than twice the maximum load.

**Higher current level operations will result in the quick low level fall of inductance.

**Maximum permissible temperature of inductor should be maintained.

**Core loss should be reduced in inductor.,in order to keep the temperature level.

**Higher efficiency inductor should be placed.

**Low electromagnetic interference (EMI), should be maintained.

**Cost effective inductor should be considered.

**Power dissipation should be less.

2)

Analogue PWM waveform can be generated by combining, a saw-tooth waveform and a square waveform...

for creating an analogue pwm..we need triangle waveform..by integrating squares waves..we get same triangle waveform

Thankyou sir/madam..hope this helped you.