The document describes the operation of a buck-boost converter. It discusses how the buck-boost converter can operate in both buck and boost modes depending on the duty ratio of the control signal. It also explains the control circuit design using op-amps, the transistor switch, and how the frequency and duty ratio can be controlled. Finally, it discusses the power circuit operation in three steps and how the output voltage is determined based on the duty ratio and input voltage.

1. BUCK-BOOST
CONVERTER
Prepared by- Shubham Yadav
16BSCSC010

2. INTRODUCTION
• Buck-boost converter operates dc supply
• Buck operation
• Boost operation
• Duty ratio of control signal defines its operation

3. OPERATION OF CONTROL CIRCUIT
• To drive the mosfet op-amp based circuit is designed
• Op-amp(A) is used as an integrator
• Op-amp(B) and Op-amp(C) is used as a comparator
• Transistor 2N5294 is used as a switch to provide
control signal
• Frequency and duty ratio of output signal can be
controlled by using potentiometer in this circuit

4. • Output waveform of Op-amp(A)
• Output waveform of Op-amp(B)
• Output waveform of control circuit

5. POWER CIRCUIT

6. OPERATION OF POWER CIRCUIT
• Step 1: when mosfet is ON
• Voltage across inductor L is equal to V (source voltage)

7. • Step 2: When mofset is OFF
• Voltage across inductor L is equal to Vo (in reverse
direction)
• Here output voltage developed across load is Vo

8. • Step 3: when mosfet is ON in next cycle
Load is isolated from voltage source
In this case charged capacitor across load will
maintain voltage across load

9. DUTY RATIO
• Duty ratio D is defined as Ton/T
Here, Ton=ON time
T= time period of gate signal
• D= Ton/T
Ton=DT
• T=Ton+Toff
Toff=(1-D)T

10. VOLTAGE ACROSS INDUCTOR
• When mosfet is ON, voltage across inductor is equal to source
voltage (V)
• When mosfet is OFF, voltage across inductor is equal to output
voltage (V)
• As average voltage across inductor is zero
Hence,
V*D*T=Vo*(1-D)*T
Vo=V* D/1-D

11. • This equation shows that output voltage depends on
duty ratio(D)
• For buck operation
D=0 to 0.5
• For boost operation
D=0.5 to 1

13. APPLICATION
• Used in many industrial applications such as subway
cars, trolly buses, battery operated vehicles, battery
charging etc.
• To provide smooth control on output, high efficiency,
fast response and regeneration.
• To provide efficient control on dc motor operation
• To provide long life and less maintenance due to
absence of moving parts.

14. THANK YOU