ELEX_4420_-_Lab_08_-_Switch_Mode_Power_Supply_SMPS

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British Columbia Institute of Technology *

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4420

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Electrical Engineering

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May 6, 2024

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BCIT ELEX 4420 1 ELEX 4420 – Power Elec & Renew Energy App Lab 8: Switch Mode Power Supply Lab Report Marcel Moreno A01267227 April 1, 2024

BCIT ELEX 4420 2 Lab 8 – Switch Mode Power Supply Objective To build and test boost, buck-boost, and buck converters. Equipment IRF840 - Transistor (N-channel Power MOSFET) 1N5819 - Schottky Diode 1N5254B - Zener Diode 27 V 1/2W 2x1000 μ F polarized capacitors 0.1 Ω (±1%), 2W current sensing resistor 1 kΩ resistor 470 μ H, 3 A inductor (not in the kit, will be provided) Rheostat (not in the kit, will be provided)

BCIT ELEX 4420 3 A – Boost Converter [3 marks] When building your circuit, aim to keep the leads/paths conducting large currents as short as you reasonably can. Failure to do so will result in difficulties or large deviations in expected measurements as well as difficulty in making measurements for the remainder of the laboratory. To get rid of extra noise on the scope: • Please use the ACQUIRE AVERAGE option. • Also, on CH1 and CH2 turn the BW option ON. 1. Set the function generator to output a 0 V to 10 V (5 V DC offset) pulse with a frequency of 20 kHz and 50% duty cycle. Your load resistance (Rheostat) should be set to 50 Ω . 2. Set the DC power supply’s voltage to 5 V and its current limit to 1 A . 3. Connect the DMM to the output load to measure the DC voltage. 4. Build the circuit. Show it to the instructor. Include a picture of the circuit in your report. 1000μF 1 k 1000μF 5 V R L =50 470 μH D1 27V Zener Q1 V s (t) R s Function Generator + V gs - + V ds - 1N5819 IRF840 V CH2 CH1 0 10 0.1 i=v/R i in Note 1: This circuit includes a gradual overvoltage protection using a 27 V Zener diode. If the output voltage exceeds 27 V, it will begin to conduct and load down your boost converter. This prevents accidental overvoltage should you remove the load. Note 2: your variable resistor at the output is the power rheostat (which will be provided to you by your lab instructor). Note 3: Your current sampling resistor is used to measure the inductor current and is placed on the low potential side (return path) of your circuit so that you do not have to tie your scope common to a high potential. This reduces the risk of creating a short circuit through the scope probe common connectors (bad!). Note that the two sides of the sampling resistor should not be in the same breadboard rail.

BCIT ELEX 4420 4 Transistor’s pin map is provided. Show your circuit to the lab instructor. Helpful wiring tip for this circuit: Sampling resistor will be placed between the two rails. 1. For three different loads (50 Ω, 150 Ω, and 250 Ω) , find the values asked in the table: R (Ω) V o (DC) DMM V o (AC) DMM ∆ V o Scope ∆ i L =∆V CH2 /0.1 Scope P in DC Supply P out = 𝑉 ? 2 /𝑅 𝜂 = 𝑃 ? 𝑃 𝑖? 50 7.96V 0.8mV 480mV 0.48A 1.579W 1.267W 0.80 150 8.68 0.4mV 320mV 0.40A 0.930 0.753W 0.81 250 10.14 0.3mV 300mV 0.28A 0.503 0.411W 0.82 2. The following pictures show how inductor current change as R increases (or as D decreases). The circuit transition from Continuous Conduction Mode (CCM) to Boundary Conduction Mode (BCM) and then Discontinuous Conduction Mode (DCM). For what value of R, the circuit transitions from CCM to DCM? For this resistance, inductor current starts from 0 A and ends at 0 A within one cycle. Note 1: To measure P in , read the DC source’s supply power: Note 2: To read the ∆ V o and ∆i L from the oscilloscope, use AC coupling to observe and capture the voltage ripples.

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