EXPERIMENT No. 5
STUDY OF BOOST CONVERTER
Name
ID No.
Sec.No
Batch No.
Date
Marks obtained
Instructor’s signature
OBJECTIVES
a. To Study the PWM generation Circuit for Boost converter.
b. Study the performance of the Boost converter for different values of L,C and load
EQUIPMENTS NEEDED
1. Oscilloscope
2. Digital Multimeter
3. BNC to Test Probe
4. Techbook Scientech 2727 and power supply.
5. Patch Cords & Operating manual
CIRCUIT DIAGRAM:
Figure 5.1 Power circuit for Boost converter
PROCEDURE FOR STUDYING THE PWM CIRCUIT.
Make sure that there is no connection on the board initially.
1. Connect the Power supply (SMPS) to Techbook Scientech 2727.
2.
Switch on the instrument.
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3. Observe the output of PWM Generation block at TP1 with respect to GND on oscilloscope.
4.
Observe the output of optical isolation block at TP2 with respect to ISO_GND on oscilloscope.
5.
Observe the Gate pulse at TP3 with respect Vs.
6.
Vary the frequency control potentiometer to observe frequency variation on the oscilloscope.
7.
Vary the Duty Cycle control potentiometer to observe the duty cycle variation on the
oscilloscope.
8. Switch OFF the Power supply Unit. Remove the test probes from ST 2729.
OBSERVATION TABLE 5.1:
Minimum
Frequency
(Hz)
Maximum
Frequency
(Hz)
Minimum Pulse
Width
(%)
Maximum Pulse
Width
(%)
PROCEDURE FOR STUDYING THE BOOST CONVERTER
Make sure that there is no connection on the board initially.
1. Switch ON the Power supply unit.
2. Set the chopping frequency at 20 KHz by the frequency potentiometer.
3. Set the PWM duty cycle at minimum by varying Duty cycle control potentiometer.
4. Switch OFF the Power supply unit.
5. Connect one end of inductor L1 to the diode D1 & the other end of inductor L1 to positive terminal of
capacitor C1.
6. Connect the one end of the RL1 to the one end of the load terminal & other terminal of the RL1 to
the other end of the load.
7. Connect the GATE pulse to the gate of the T1 (IGBT).
8. Connect +24V and ISO_GND to the boost configuration.
9. Switch on the instrument.
10.Vary the PWM control potentiometer at different pulse width. Observe the variable DC voltage acrossthe
load.
11. Verify the output DC voltage with the theoretical value.
12. Connect the multimeter in DC mode and vary the PWM control potentiometer and observe the output
voltage across the load, switch and diode.
13. Connect the oscilloscope and vary the PWM control potentiometer & observe the waveforms of
inductor current, diode current, output capacitor ripple voltage, and capacitor current. (For output ripple
voltage, measure Vo in ac coupling.)
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14. Switch ‘Off’ the power supply.
15. Repeat the experiment for different values of L, C and load.
16. Disconnect all the connections from the board.
OBSERVATION TABLE 5.2
Frequency f = 20 kHz
Input Voltage = 𝑉i𝑛
Output Voltage = 𝑉0
Duty ratio = 𝐷
1
𝑉0 =
S.
No.
Inductor
value
(µH)
Capacitor
(µF)
1
L1
C1
20%
2
L1
C1
30%
3
L1+L2
C1
20%
4
L1+L2
C1
30%
PWM (%)
1−𝐷
Measured
Output
Voltage
(V)
𝑉i𝑛
Theoretica
l Output
Voltage (V)
Measured
voltage across
the switch
(V)
Measured
voltage
across the
diode (V)
GRAPHS
1. Draw the graphs of PWM output, inductor current, diode current and capacitor current for duty
ratio of 0.3 for the values of L1+L2 and C1 for Boost converter.
2. Draw the graphs of PWM output, inductor current, diode current and capacitor current for duty ratio of 0.2
for the values of L1+L2 and C1 for Boost converter.
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Specification for the ST2727 Boost converter
SMPS : +/- 12V@ 500mA, +5V@250mA SMPS :
+/- 12V@ 500mA, +5V@250mA SMPS : +/15V@1A
SMPS : +24 V@1A for DC rail
Input DC Voltage
: 24V/1A
PWM Frequency Variation
: 1 KHz to 22 KHz
Duty Cycle Variation
: 10% to 45%
Power Isolation Section
: Single channel, 10x
Power device
: IGBT TOSHIBA 20JT101
Diode
: UF4007
MOSFET/ IGBT Driver
: MC33153
Rsense
: 0.1Ω
Turn off Snubber
: 100E 1W & 0.1µF 250V
Dimensions (mm)
: W 326 x D 252 x H 52
Power Supply
: 110V - 260V AC, 50/60Hz
Weight
: 1.5Kg (approximately)
Operating Conditions
: 0-400 C, 85% RH
L1
L2
L3
C1
C2
C3
RL1
RL2
1.5mH
404uH
User
1000uF/63V
470uF/63V
220uF/63V
75Ω/ 25W
75Ω/ 25W
Please use external load for observing output power more than 15W. The maximum output power should not
exceed 20W.
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