GATE Electrical Engineering - Complete Master Library

 

 Page 23 – Step Up Chopper (Boost Converter)

                                          

1️⃣ What is a Step Up Chopper?

A Step Up Chopper (Boost Converter) is a DC-DC converter that produces an output voltage greater than the input voltage.

✔ Output Voltage > Input Voltage
✔ Used in EVs, UPS, renewable systems
✔ High efficiency voltage boosting

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2️⃣ Circuit Operation

🔹 Switch ON (T_ON)

• Inductor stores energy
• Diode is reverse biased
• Load supplied by capacitor

🔹 Switch OFF (T_OFF)

• Inductor releases stored energy
• Diode conducts
• Energy adds to input → Output increases

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3️⃣ Output Voltage Derivation (CCM)

Using volt-second balance on inductor:

V_in × T_ON = (V_o − V_in) × T_OFF

Since,

T = T_ON + T_OFF

After simplification:

V_o = V_in / (1 − D)

Where,

D = T_ON / T

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4️⃣ Important Characteristics

• 0 ≤ D < 1
• As D → 1, V_o increases rapidly
• Inductor is mandatory
• Output ripple depends on L, C, and frequency

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 GATE Important Points

• Derivation of V_o = V_in / (1 − D)
• Inductor volt-second balance
• Waveform understanding
• Continuous vs Discontinuous mode
• Comparison with Buck converter

Very Important: Boost converter increases voltage by storing energy in inductor during ON time.