5V Regulator Design Tutorial: Switching Regulators & Calculation Guide

Switching Regulator Design Calculator Overview

Aichiplink Electronic has developed several online calculation tools for electrical designers, including a Switching Regulator Design Calculator. This tool helps calculate the output voltage of a switching regulator to create an ideal switching circuit.

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Introduction to Switching Regulators

What is a Switching Regulator?

Unlike a Linear Regulator, a [Switching Regulator] (also known as a Switched Mode Power Supply or SMPS) acts as a DC-to-DC converter. It utilizes a power switch, diode, and inductor to efficiently transfer energy from the source to the output.

Types of Switching Regulators

There are three main types of switching regulators available in the marketplace:

1. Buck Regulator (Step-Down)

A Buck regulator is used to step down a higher input voltage to a lower output voltage.

• Example: The MC34063 DC-DC converter IC can be used in Buck mode to convert 12V to 5V.
• DIY: You can also create a simple Buck regulator circuit using an N-Channel MOSFET and an Arduino.

2. Boost Regulator (Step-Up)

A Boost converter generates a voltage at the output that is higher than the input voltage.

• Example: Boosting a single 3.7V lithium-ion battery to produce 5V or 12V.
• Popular ICs: TPS61022, TPS61088, LM5150, and TPS61023.

3. Inverter

Used to reverse the polarity of the input voltage (e.g., generating -5V from +5V).

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Core Components of a Switching Regulator

A switch-mode converter typically relies on four main electronic components:

1. Switches / Transistors: These control the voltage flow and are the reason these devices are called "Switching Regulators."
2. Inductors: A passive component used to store energy in its magnetic field during the switching cycle.
3. Capacitors: A 2-terminal passive device used to store energy in an electric field and filter the output voltage.
4. Diodes: Function as a one-way switch for current, permitting flow in one direction while blocking it in the other.

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Design Examples: Switching vs. Linear

1. Switching Example: LM3671 Buck Converter

The LM3671 is a step-down DC-DC converter IC designed for high efficiency. Designing a switching regulator like this is generally more complex than a linear regulator due to the requirement of external inductors and filter capacitors.

• Key Design Elements: Inductor selection, Input/Output Capacitor selection.
• Resource: Download LM3671 Datasheet.

2. Linear Example: LM317 Voltage Regulator

The LM317 is a classic 3-terminal positive adjustable voltage regulator. Unlike switching regulators, it dissipates excess power as heat but is much simpler to use.

• Related ICs: LM350, LM338 (High current versions), and LM337 (Negative regulator).
• Calculation: You can use an LM317 calculator to determine the values of R1 (Program Resistor) and R2 (Set Resistor) to achieve the desired output voltage.

!LM317 Pinout Diagram

Key Features of LM317:

• Adjustable Output-voltage range: 1.25 V to 37 V
• Output current greater than 1.5 A
• Internal short-circuit current limiting
• Thermal overload protection
• Output safe-area compensation

Applications:

• Desktop PCs, DVS, and DVRs
• Digital Signage and Cameras
• Energy Harvesting and Optical Networking