![]() In this mode, the inductor releases the energy which is stored in the previous mode of operation. So, as we have discussed that the inductor in the circuit will store the energy so, once S 1 will get open the inductor in the circuit will start acting as the source. However, you must be thinking about how automatically, the switch S 2 will be closed. Now, the second mode of operation takes place when switch S 2 is closed and S 1 gets open. The above equation represents the change in current through the circuit when switch S1 is closed. When S1 is in closed condition then T on = DT thus Δt = DT. On applying KVL, in the above-given circuit, Here the total time period is a combination of T on and T off time. However, due to Lenz’s law, the energy stored within the inductor will oppose the cause which has produced it and so an induced current will get generated and the polarity across the inductor will get reversed. ![]() Also, there is a capacitor in the circuit and current flows through it also, therefore, it will store the charge and the voltage across it will appear across the load. Due to this flowing current, the inductor in the path stores energy in the form of a magnetic field. Initially when a fixed dc voltage is applied across the input terminal of the circuit then in the closed condition of switch S 1 current flows in the circuit in the manner shown above. In this mode of operation, switch S 1 is in closed condition thus allows the flow of current to take place through it. The first mode is the one when the power MOSFET i.e., switch S 1 is closed. The whole operation of the circuit takes place in two modes. A pure resistor is connected across this whole arrangement that acts as a load of the circuit. This helps in generating regulated dc output. The combination of these two switches forms a connection with a low-pass LC filter in order to reduce current or voltage ripples. In the above figure, it is clearly shown that along with the power electronics solid-state device which acts as a switch for the circuit, there is another switch in the circuit which is a freewheeling diode. ![]() The figure given below shows the circuit representation of Buck Converter: A buck converter is a type of chopper which is designed to generate a lower value at its output from the fixed dc input signal. We have mentioned in the beginning itself that choppers are designed to produce such a dc signal at the output which is more or less than that of the applied input signal. While power MOSFET or IGBT can be turned off by maintaining zero potential between the gate to source terminal for MOSFET or gate to collector terminal for IGBT. The use of thyristor is generally prohibited in chopper circuits and the reason behind the same is that in order to commutate a thyristor, an external commutation circuit is required. that acts as a switch in the chopper circuits. There are various power semiconductor devices such as power BJT, power MOSFET, IGBT, GTO, etc. It is mainly designed to increase or decrease the voltage level of the signal applied at its terminals. ![]() ![]() We have already discussed in our previous content that choppers are the circuits that are designed to perform the conversion of a fixed dc signal into an adjustable dc signal. ![]()
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