Type A chopper

We all know that a chopper can operate in any of the four quadrants by an appropriate arrangement of semiconductor devices. This characteristic of their operation in any four quadrants form the basis of their classification as class A, class B, class C, Class D, class E etc.

It is observed that the chopper circuit of the figure also types A chopper. 
  • When chopper is on V= Vand current iflows from in the arrow direction shown. 
  • When chopper is in off  V0=0 and i0 in the load continues flowing in the same direction through freewheeling diode FD, shown in the figure. 
  • It is thus seen that the average values of both load voltage and current  V0 and Iare always positive.
  • And this shown by the second figure by the hatched area in the first quadrant of  V0 - Iplane in figure.
  • The power flow in type A chopper is always from the source side to load side. This chopper is also known as the step-down chopper as average output voltage V0 is always less than the input dc voltage Vs.