Power Electronics Project: ±15V SMPS Design using Boost and Buck-Boost

This project report focuses on the design and analysis of a ±15V regulated symmetrical power supply (SMPS) using boost and buck-boost converters. The report begins with an overview of SMPS, highlighting its efficiency, advantages, and various applications. It explains the fundamental concepts of switch mode power supplies, including different configurations like AC to DC, DC to DC, DC to AC, and AC to AC converters, along with their key components such as transformers, rectifiers, and feedback circuits. The report then details the design of a ±15V DC power supply from a 9V DC battery, utilizing a boost converter to step up the voltage and a buck-boost converter to achieve the desired output voltage. The design includes circuit diagrams, component lists, and formulas for calculating ripple factors and peak-to-peak ripple current. The report also presents the results of the design, including RMS and average values for boost and buck-boost converters, and discusses the circuit's construction and testing, including PCB layout considerations. The project aims to provide a practical understanding of power electronics concepts and the application of SMPS in real-world scenarios.

POWER ELECTRONICS
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A switch mode power supply defines an electronic circuit which changes power with the use of
switching devices which are switched on and off at frequencies that are relatively high and
storage parts for instance capacitor or inductors in supplying power when the device for
switching is in a non-conduction state. A switch mode power supply is as well called a switch
mode power supply or even switching mode power supply. Switch mode power supplies are
grouped as per the kind of output or input voltages resulting into four groups:
 AC to DC
 DC to DC
 DC to AC
 AC to AC
An ideal AC to DC switch mode power supply is composed of:
 Transformer
 Input filter and rectifier
 Feedback & control circuit
 Inverter composed of switching devices for instance MOSFETs
A rectifier of batter input DC supply is directed into the inverter in which it is switched on and
off at relatively high frequencies that are in the range of between 20 and 200 KHz with the use of
the power transistors or switching MOSFET [2]. The voltage pulses that are at high frequencies
from the inverter are directed into the primary winding of the transformer with the secondary
output undergoing rectification and smoothening to generate the needed voltages of DC. A
feedback circuit is used in checking the output voltage as well as giving instructions to the

control circuit to make adjustments to the duty cycles to keep the output at the levels that are
desired.
The various types of switch mode power supplies include:
Forward converter, in which, the current is carried by the choker when transistor is under
conduction and when it is not. The current is carried by the diode during the period of an off in
the transistor hence the flow of energy into the load during the two periods.
Fly back converter involves the inductor magnetic field storing the energy in the on period of
switch. The energy is drained into output voltage circuit in an open state of the switch. The
output voltage is determined by the duty cycle.
DC to DC converter: The reception of the primary power from AC main undergoes rectification
as well as filtration in the nature of high voltage DC which is thereafter switched at a very high
speed and channelled into the primary divide of a step-down transformer. The step down
transformer is just but an inch of the size of a 50 Hz unit that may be used for comparison hence
sorting the problems of size and weight. It is thereafter channelled to power supply output and a
sample of the output is resent to the switch to regulate the voltage of the output.
Self-oscillating fly back converter works on the principle of fly back such that during the time of
connection of switching transistor, the current via the primary of the transformer begins ramping
up in a linear manner during the slope is equivalent to Vin/Lp. The induced voltage in secondary
winding and feedback winding result in fast recovery rectifier reverse biased and keep the
conducting resistor in an on state. When a peak value Ip is attained by the primary current in
which the core starts saturating, there tends to be a sharp rise in the current. The sharp rise is the

current may not be supported through the fixed based offered by the feedback winding hence
switching starts to be released out of saturation.
Cooling power initially adheres to circuits and a line procedure. By then it is reviewed by a full-
wave associate rectifier [1]. The changed voltage is next applied to the power factor amendment
(PFC) pre-controller sought after by the downstream DC-DC converter(s). Most PCs and little
devices use the International Electrotechnical Commission (IEC) style input connector. As for
yield connectors and pin outs, beside specific endeavor, for instance, PC and littler PCI, all
around, they are not organized and are given up over to the producer [2].
Switch mode power supplies are often applied in an avalanche of applications as an efficient as
well as effective power source and this is mainly owed to their efficiency.
+/- 15 VDC Design
Operational amps need dual polarity supply for appropriate activity. When working with battery
supply, it ends up hard getting double power supply for the operation amps. Exhibited here is a
basic circuit that gives ±15V from a 9V battery.
Circuit and working
The circuit outline for the ±15V supply from a 9V battery is appeared in diagram 1. It is worked
around 9V battery (BATT.1), voltage controller IC 78L05 (IC1), CMOS voltage converter
ICL7660 (IC2) and a couple of different parts.

Figure 1: Schematic diagram of Boost and Buck-Boost Chopper Converter
Voltage controller IC1 changes over 9V battery contribution to directed 15V. This 15V output
from IC1 is given to stick 8 of IC2. IC2 and capacitors C3 and C4 structure the voltage inverter
segment that changes over +15V to - 15V. Changed over - 15V supply is accessible at stick 5 of
IC2. Changed over ±15V supply is in this manner accessible at connector CON1.

Figure 2: Waveform of Boost and Buck-Boost Chopper Converter
Components list of 9v dc to plus/minus 15v dc converter
Capacitors
 C1 = 470 μF, 25V (Electrolytic Capacitor)
 C2 = 2.2 μF, 16V (Electrolytic Capacitor)
 C3, C4 = 10 μF, 16V (Electrolytic Capacitor)
Semiconductors
 IC1 = LM7805 (+5V arrangement fixed voltage controller)
 IC2 = ICL 7660 (voltage converter IC)
9V battery
Development and testing
Diagram 2: Layout of PCB actual size of +/-15 V supply from 9V battery

Collect the circuit on the PCB and wall it in a water-confirmation box. Battery BATT.1 ought to
be encased in the container. Fix CON1 on the front or back side of bureau, with the goal that you
can utilize the ±5V effectively. Prior to utilizing the circuit, confirm the test focuses given in the
table to guarantee appropriate working of circuit [3].
Boost Converter
RMS Average
15.193279 15.1932208
Buck-Boost Converter
RMS Average Maximum Minimum
15.43231 15.432116 15.280038 15.579924
Formulae
Form Factor of Boost
FF= VRMS
VO
FF= 1.000004979
For Buck-Boost
FF= VRMS
VO
FF= 1.000013321
Ripple factor of Output voltage for boost
RF= 1.000005179 v
For buck-boost
RF= 1.000014299 v
The Peak to peak ripple current (I) of boost
Ip-p=IMAX - IMIN
= 0.181004
For buck-boost

Ip-p= IMIN - IMAX
= 0.0119652
Devise or Component Figure 1:
No Description Unit Value Quantity
1 MOSFET Pcs IRF740 4
2 Diode Pcs 40esps08 4
3 Voltage source Ps 9 volts 2
4 Capacitor Pcs 4.7 mill farad 4
5 Inductor Pcs 10 millinery 4
6 Place voltage
source Pcs None 4
7 Resistor Pcs 15 ohms 4

References
[1] Marston RM. 110 integrated circuit projects for the home constructor. Elsevier; 2016
May 13
[2] Newman Jr RC, Carmen DF, Salvestrini CJ, Harte MV, inventors; Lutron Electronics Co
Inc, assignee. Load Control Device for High-Efficiency Loads. United States patent
application US 15/947,216. 2018 Aug 16
[3] Newman Jr RC, Salvestrini CJ, Harte MV, inventors; Lutron Electronics Co Inc,
assignee. Load Control Device for High-Efficiency Loads. United States patent
application US 15/852,328. 2018 May 10