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Monday, June 27, 2011

EC 2404 ELECTRONIC SYSTEM DESIGN LAB REGULATION CHARACTERISTICS OF BUCK-BOOST CONVERTER


REGULATION CHARACTERISTICS OF BUCK-BOOST CONVERTER

AIM:

To determine the closed loop response of the Buck-Boost converter and plot the regulation characteristics.

APPARATUS REQUIRED:

1.      VSMPS-07A Trainer
2.      Pulse patch chords
3.      (0-30V) DC supply
4.      CRO

FORMULA:
           

Output voltage V= (-D / 1-D) Vs Volts

                        Where V0 = Converter Output Voltage, Volts
                                    Vs = Converter input voltage, volts
                                    D = Duty Cycle (ton / T)

THEORY:

The Buck Boost is a popular non-isolated, inverting power stage topology, sometimes called a step up/down power stage. The Buck boost power stage is chosen because the output voltage is inverted from the input voltage and the output voltage can be either higher or lower than the input voltage. However the output voltage is opposite in polarity from the input voltage. The Buck Boost converter circuit consist of MOSFET switch Q, inductor L, diode D, filter capacitor C and load resistor R.

CONNECTION PROCEDURE:

·         Connect P8 of PWM generator to PWM input of Buck-Boost converter circuit.
·         Connect P4 of Buck-Boost converter circuit to P7 of PWM generator.
·         Set switch SW1 to downward direction to select the closed loop operation.
·         Connect (0-30V) DC regulated power supply across P1 and P2 terminals of the trainer module and set the voltage at 15 V.



CIRCUIT DIAGRAM:




                                            Buck –Boost Converter


Model  Graph :



                                                                       
                                                                                                                                                                                                                                                          
                                                                                               





           Line Regulation                                                          Load Regulation






EXPERIMENTAL PROCEDURE:

A) Line Regulation:
           
·         Switch ON the AC power supply and the power ON/OFF switch of the trainer kit.
·         View the carrier signal in CRO at T3.
·         Set the switch SW1 in downward direction.
·         Set the switch SW2 in downward direction.
·         View the PWM signal in CRO at T1.
·         Vary the Set voltage adjust POT from minimum to maximum and note down the ton and T values.
·         Set the PWM signal at desired duty cycle ratio (maximum 50%).
·         Switch ON the variable DC supply.
·         Vary the input voltage from (0-15) V and note down the corresponding output voltage across P5 and P6.
·         For each input voltage value tabulate the measured output voltage values.


Set the switch SW2 in upward direction and repeat the same procedure for Buck converter.























TABULATION (BUCK MODE):

A) Line Regulation:


                       
S.No
Input Voltage (Volts)
Output Voltage (Volts)












B) Load Regulation:

S.No
Load Resistor (W)
Load Current (mA)
Output Voltage (Volts)


























TABULATION (BOOST MODE):

A) Line Regulation:


                       
S.No
Input Voltage (Volts)
Output Voltage (Volts)












B) Load Regulation:

S.No
Load Resistor (W)
Load Current (mA)
Output Voltage (Volts)

























b) Load Regulation:

·         Switch ON the AC power supply and the power ON/OFF switch of the trainer kit.
·         View the carrier signal in CRO at T3.
·         Set the switch SW1 in downward direction.
·         Set the switch SW2 in downward direction.
·         View the PWM signal in CRO at T1.
·         Vary the Set voltage adjust POT from minimum to maximum and note down the ton and T values.
·         Set the PWM signal at desired duty cycle ratio (maximum 50%).
·         Switch ON the variable DC supply.
·         Set the input to a constant value and vary the load resistor value, note down the corresponding output voltage across P5 and P6 output terminals of trainer module..
·         For each load resistor value tabulate the measured output voltage values.
·         Set the switch SW2 in upward direction and repeat the same procedure for Buck converter.


RESULT:

Thus the closed loop response for Boost/Buck operation of Buck-Boost converter of Line/Load regulation was determined.
1. The output voltage is maintained at ------ V with the input voltage from     ------- V to ---------- V for boost mode of operation.
2. The output voltage is maintained at ------ V with the input voltage from ------- V to ---------- V for buck mode of operation.

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