A step-down chopper is also called as a

Question

Examoogle · Accepted Answer

first-quadrant chopper

Explanation: A step-down chopper, also known as a Buck converter or Type-A chopper, operates in the first quadrant because both the output voltage and output current are always positive. It converts a fixed DC input voltage into a lower, variable DC output voltage by rapidly switching the source on and off.

Working Principle: When the chopper (switch) is ON, the source voltage $V_s$ is applied to the load, allowing current to flow from the source. When the chopper is OFF, the load current freewheels through the freewheeling diode, maintaining a positive current flow while the output voltage drops to zero. Since power always flows from the source to the load, the operation is strictly confined to the first quadrant of the $V_o-I_o$ plane.

Key Formulas: $V_o = D \cdot V_s$ — The output voltage depends on duty cycle $D$ and input voltage $V_s$; $D = \frac{T_{on}}{T_{on} + T_{off}}$ — Definition of duty cycle ratio

Key Points: Input and output voltages are both positive ($V_o > 0$).; Load current is unidirectional and positive ($I_o > 0$).; Power flow is always from source to load.; A freewheeling diode is essential to provide a path for inductive load current when the switch is off.

Advantages: High efficiency in power conversion; Simple control circuit implementation; Compact and lightweight for high-frequency switching

Disadvantages: Input current is discontinuous, requiring input filtering; Switching losses increase with frequency; Electromagnetic Interference (EMI) generation

Applications: Electric traction and DC motor control; Switch-mode power supplies (SMPS); Battery charging circuits

Additional Info: The duty cycle $D$ is the ratio of switch ON-time to the total switching period $T$.. Option B (second-quadrant) refers to a step-up chopper where power flows from load to source (regenerative braking).

Answer: A is correct — A step-down chopper is classified as a first-quadrant chopper because it maintains positive output voltage and current.

Exam Tip: Always relate chopper quadrants to power flow; if current and voltage polarities are both positive, the converter is a first-quadrant device (Source to Load).

Related Questions

Discussion (0)