Question

What is the voltage across the load when the SW is first closed and then opened?

(a) Vs

(b) duty cycle x Vs

(c) Vs + L (di/dt)

(d) zero

The question was posed to me in homework.

My doubt is from Choppers-2 topic in chapter Choppers of Power Electronics

Answer 1

The correct answer is (c) Vs + L (di/dt)

Easy explanation: When the switch is off, the inductor is has stored energy from the earlier chopper on operation. The current starts to flow from Vs-L-D-Load-Vs, hence current is decaying as the inductor is discharging and the load voltage is Vs + Vl (inductor voltage)

Vl = L(di/dt)

Vo = Vs + L(di/dt).