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Adjustable LM338 Power Supply: 1.2 to 32V 5A with Short-Circuit Protection

Electronic Circuits — Mon, 09 Mar 2026 06:40:56 +0000

Adjustable Power Supply LM338: 1.2 to 32V 5A with Short Circuit Protection + PCB

🌐 You can read this article in: Português | Español

If you've ever found yourself at an electronics workbench trying to power a prototype with those cheap power supplies that barely regulate the voltage, you know exactly what I'm talking about. The frustration of seeing a project burn out due to a lack of a stable power supply is something every maker or technician has experienced at least once.

But what if I told you that you can build a professional bench power supply, adjustable from 1.2V to 32V with a whopping 5 amps of current, spending less than you would pay for a commercial power supply of dubious quality?

As an electronics professor for over a decade and having tested dozens of configurations on my own bench, I can state with authority: the LM338 is one of the most robust and reliable solutions for DIY bench power supplies. In this complete guide, I will show you step-by-step how to build your own adjustable power supply, explaining not just the "how," but mainly the "why" behind every component and design decision.

Get ready to have in your hands a power supply that rivals entry-level commercial equipment, and best of all: you will understand every inch of the circuit.

🔌 Why the LM338 is the Perfect Choice for Bench Power Supplies?

The LM338 is an adjustable three-terminal voltage regulator capable of supplying up to 5 continuous amps in a range of 1.2V to 33V. But what really sets it apart from other regulators in the 78xx family or even the popular LM317?

Here is the secret:

In my experience testing bench power supplies, I discovered that the LM338 offers three crucial advantages that make it practically indestructible, something I learned the hard way after frying a few LM317s in tests with heavy loads:

Smart thermal current limiting: Think of the LM338 as a security guard who gets stricter as the situation heats up. It allows peaks of up to 12A for short periods (perfect for motors or lamps at startup), but automatically reduces to 5A in continuous mode, protecting itself against overheating.
SOA Protection (Safe Operating Area): It's like having an electronic airbag. The internal circuit simultaneously monitors voltage, current, and temperature, ensuring the pass transistor never operates outside the safe zone, even if you accidentally cause a short circuit at the output.
Thermal shutdown with hysteresis: If the chip temperature exceeds 125°C, it simply shuts down. When it cools down to about 100°C, it automatically turns back on. I tested this by placing the heatsink against a heat source: the LM338 survived; a 7805 would have turned into scrap.

But that's not all.

The configuration is surprisingly simple: just two external resistors define the entire voltage regulation. Compare that with switching regulators that require inductors, Schottky diodes, compensation loops... The LM338 is the definition of "robust simplicity".

📊 LM338 Technical Specifications (Real Lab Data)

Output voltage range: 1.2V to 33V DC
Continuous output current: 5A (guaranteed)
Peak current (transients): Up to 12A for short periods
Line regulation: 0.005%/V (practically negligible)
Load regulation: 0.1% typical
Dropout voltage: ~3V (minimum difference between input and output)
Operating temperature: -55°C to +150°C
Integrated protections: Thermal, short-circuit, and SOA

⚡ Complete Circuit Analysis: Understanding Each Component

The circuit for this power supply was designed to maximize stability, minimize ripple, and guarantee full protection against failures. Let's dissect every stage of operation, and you will understand why each component is exactly where it is.

Fig. 2 – Complete electrical schematic with all protections and stabilization components.

⚡ Stage 1: Input, Rectification, and Rough Filtering

AC Input and Bridge D1 (GBJ2510): The project starts with full-wave rectification. We use the GBJ2510 bridge, capable of supporting up to 25A. Although the power supply is 5A, this thermal margin ensures that the component works cool and supports current peaks without degrading. To achieve 32V DC at the output, a transformer of 24VAC to 28VAC with a secondary current of at least 5A is recommended.

Capacitor C1 (6800µF/50V): This is the lungs of the power supply. It smooths the pulsating waveform coming from the bridge. The golden rule here is 1000µF to 2000µF per Ampere of output. With 6800µF, we have an excellent compromise between size and filtering, ensuring that the regulator has a stable voltage to work with, even under maximum load.

🛡️ Stage 2: Protections and the LM338T "Brain"

Regulator U1 (LM338T): The heart of the system. It keeps the output voltage constant regardless of load variations. Attention: Since this is a linear regulator, excess voltage is dissipated as heat. A generous heatsink is mandatory to prevent the internal thermal protection from triggering the chip.

Protection Diodes D2 and D3 (1N4007): These are the bodyguards of the regulator. The D2 protects the LM338 in case the input is short-circuited, preventing the output capacitors from discharging into the chip. Meanwhile, D3 protects the adjustment pin (ADJ) against sudden discharge from capacitor C2. Without them, any failure or abrupt shutdown could burn the regulator instantly.

⚙️ Stage 3: Stability and Output Smoothing

Capacitor C2 (100µF): Connected to the adjustment pin, this capacitor filters any residual noise that could be amplified. Furthermore, it provides a Soft-Start effect (soft start), causing the voltage to rise gradually when the circuit is turned on, protecting the connected load.

Output Filtering (C3 2200µF and C4 0.1µF): C3 acts as a local reservoir for fast load transients, while C4 (ceramic) eliminates high-frequency noise. Together, they guarantee a "clean" DC output, essential for powering microcontrollers or sensitive audio circuits.

🎛️ Stage 4: Voltage Divider and Fine Adjustment

Resistor R3 (220Ω) and Potentiometer RP1 (5kΩ): This set defines the output voltage through the formula Vout = 1.25V * (1 + RP1/R3).

Minimum: With RP1 at 0Ω, the output is the internal reference value: 1.25V.
Maximum: With RP1 at 5kΩ, the output reaches approximately 29.6V. To reach exactly 32V, you can slightly reduce the value of R3 or use a higher commercial value potentiometer.

Engineer's Tip: To turn this project into a professional bench tool, replace the common potentiometer with a 10-turn multi-turn model. This allows you to adjust critical voltages, like 3.3V or 5.0V, with millimeter precision, something hard to achieve with single-turn potentiometers.

📝 Bill of Materials (BOM)

Reference	Component	Suggested Specification	Function
U1	LM338T	Adjustable Regulator (TO-220)	Main 5A Regulation
D1	GBJ2510	Bridge Rectifier 25A / 1000V	Full-wave rectification
D2, D3	1N4007	Silicon Diode 1A / 1000V	Protection against reverse currents
C1	6800µF	Electrolytic (50V or 63V)	Rough filtering (Ripple)
C2	100µF	Electrolytic (50V)	ADJ pin filtering / Soft-start
C3	2200µF	Electrolytic (50V)	Output stabilization
C4	0.1µF	Ceramic or Polyester (100nF)	High frequency filter
R3	220Ω	Metal Film Resistor 1/2W	Voltage divider reference
RP1	5kΩ	Potentiometer (Linear or Multi-turn)	Output voltage adjustment
-	Heatsink	Large Aluminum (For TO-220)	LM338 thermal management

Note: Do not forget to use good quality thermal paste between the LM338 and the heatsink. For continuous use at 5A, adding a 12V fan (cooler) is highly recommended.

🖨️ Professional PCB: Layout Optimized for Low Noise

For those seeking professional results, the PCB layout is critical. I make the files available in GERBER formats (industrial manufacturing), PDF (thermal/homemade photosensitive method), and PNG (rapid prototyping).

Fig. 3 – PCB layout with reinforced power traces (2mm) and separation between control and power signals.

📥 File Download

The files include annotated diagrams, bill of materials, and step-by-step assembly instructions:

📦 Download Complete Files (GERBER + PDF + PNG)

🔧 Assembly Tips and Advanced Optimizations

Want to extract maximum performance from your project? Here are tricks I've learned over years on the bench:

❄️ Thermal Management

Power dissipation on the LM338 follows: P = (Vin - Vout) × Iout. In the worst case (1.2V out, 5A): P = (34 - 1.2) × 5 = 164W! Without an adequate heatsink, the chip will shut down in seconds.

Professional solution: Use a heatsink with an 80mm fan (12V PWM controlled). I managed to keep the LM338 at just 55°C running 5A continuous with this configuration.

🤔 Frequently Asked Questions (FAQ)

I have compiled the most common questions I receive from students and makers about this power supply. If your question isn't here, leave it in the comments!

Can I replace the LM338 with an LM317? 🔽

Adjustable Bench Power Supply 1.25V–33V 6A Module Tutorial

Electronic Circuits — Tue, 21 Oct 2025 16:47:00 +0000

Complete module for 6A adjustable bench power supply

🌐 You can read this article in: Português | Español

Hello electronics enthusiasts!

Whether you’re an engineer, electronics technician, designer, or hobbyist, an adjustable bench power supply is an indispensable tool in any workspace. The problem? Quality commercial power supplies tend to be expensive and, often, limited in current. But what if I told you that you can build your own robust bench power supply with 6 amperes of current and adjustable voltage from 1.25V to 33V for a fraction of the cost? Keep reading to find out how!

🧐 Why Build Your Own Bench Power Supply?

Professional bench power supplies are essential for testing and developing electronic projects, but the market offers options with two main limitations: low maximum current and high prices. Quality models easily exceed R$500.00, making them inaccessible for many students and enthusiasts.

This is exactly where our project shines! We’ve developed a fantastic module that offers:

Adjustable voltage: 1.25V to 33V
Robust current: Up to 6 continuous amperes
Short-circuit protection
Thermal protection
Affordable cost and easy-to-find materials

📝 Required Materials

To build this adjustable bench power supply, we’ll use components that are easy to acquire and affordable. Many of them can be salvaged from old ATX power supplies!

Fig. 2 – Materials needed for the voltage regulator circuit

Component List:

2x LM350 ICs – 3A voltage regulators each
2x 220Ω Resistors (colors: Red, Red, Brown)
1x 5KΩ Potentiometer (preferably multi-turn for greater precision)
1x SCHOTTKY S16C45C Barrier Rectifier (16A) or alternatives
1x Universal printed circuit board or perfboard
Heat sink (can be salvaged from an ATX power supply)
Thermal insulators for ICs and rectifier

💡 Expert Tip: Don’t have a S16C45C rectifier? No problem! You can replace it with two common diodes, connecting anodes to the output of each LM and joining the cathodes to form a single output, as shown in the schematic.

🛠️ Step-by-Step Assembly

Now that we have all the components in hand, let’s start the assembly! Follow each step carefully to ensure the correct and safe operation of your module.

Step 1: Component Preparation

Start by mounting the two LM350 ICs and the SCHOTTKY rectifier on the heat sink. Attention: Don’t forget to use thermal insulators between each component and the heat sink to avoid short circuits!

Fig. 3 – Components mounted on heat sink with thermal insulators

Step 2: Board Assembly

With the components already mounted on the heat sink, fit them onto the printed circuit board. Follow the schematic to make the correct connections. The layout of components can be adapted according to your preference, as long as you maintain the correct connections.

Step 3: Resistor Connection

Solder the two 220Ω resistors as indicated in the schematic. They are essential for the correct operation of the regulator circuit.

Fig. 4 – Schematic Diagram Adjustable Power Supply Module 1.25V to 33V, 6A

Step 4: Potentiometer Installation

The voltage control potentiometer will not be soldered directly to the board. Instead, we recommend installing it remotely on the front panel of your power supply. To facilitate assembly and disassembly, we’ll use a two-pin connector.

💡 Expert Tip: For greater precision in voltage adjustment, consider using a multi-turn potentiometer. They allow for finer adjustments, essential for applications that require specific voltages.

Step 5: Soldering Connections

With all components properly positioned, proceed with soldering all connections. Make sure there are no solder bridges or cold joints that could compromise the circuit’s operation.

Fig. 5 – Soldering all connections on the universal board

Step 6: Remote Potentiometer Connection

Use a cable with a two-pin male connector to connect the potentiometer. This will facilitate the final assembly of your bench power supply, allowing the potentiometer to be installed on the front panel while the regulator module remains inside.

Fig. 6 – Cable with connector for remote potentiometer connection

🏋️‍♀️ Want More Power? Expand to 12 Amperes!

For those who think 6A is still not enough, we have excellent news! With a simple modification, it’s possible to double the current capacity to an impressive 12 amperes.

The secret? Simply build two identical modules to this one and connect them in parallel. This way, you’ll have an extremely powerful bench power supply, maintaining all protections (short-circuit and thermal) and precise voltage regulation.

⚠️ Safety Warning: When working with high currents like 12A, make sure to use appropriate wires and connectors for this capacity. High currents generate more heat and require greater care with thermal dissipation.

💡 Testing and Validation

Before powering your module, it’s essential to perform some safety checks:

Confirm that the ICs and rectifier are properly insulated from the heat sink
Check for short circuits on the board traces
Test the continuity of the main connections

With everything verified, let’s connect a power supply. In our example, we used a 24V supply. Remember that the maximum output voltage will be limited by the input voltage minus the voltage drop across the components (approximately 1.95V).

Load Test

To validate our module under real conditions, we used as a load a car headlight halogen lamp (55W, 12V). According to Ohm’s Law, this lamp consumes approximately 4.58A (55W ÷ 12V).

Fig. 7 – Initial test with Halogen lamp as load

We adjusted the voltage to 13.52V (typical voltage of a car with an alternator running) and connected the load. The result? Excellent stability, with a voltage drop of only 0.4V under a load of 4.58A!

Fig. 8 – Load test with 55W halogen lamp

🔗 Related Content

If you liked this project, you might also be interested in these other articles:

📥 Download Files

Direct link: Download Files

🧾 Conclusion

Our 6A adjustable bench power supply project demonstrates that it’s possible to build quality equipment with low cost and high efficiency. The simplicity of the circuit, combined with the robustness of the components used, results in a reliable and versatile power supply for various applications.

Whether for testing prototypes, powering circuits during development or for use in your home laboratory, this adjustable bench power supply will certainly meet your needs with excellent performance and stability.

Detailed Video

For those who would like more details about the assembly process and testing, we’ve prepared a complete video on our YouTube channel. In it, we show each step in detail and share additional tips:

🤔 Frequently Asked Questions

We’ve gathered some of the most common questions about this project to help you:

❓ Can I use a transformer different from 24V?🔽

10A Variable Power Supply 1.25–35V Using LM317 and D13007

Electronic Circuits — Fri, 17 Oct 2025 22:49:00 +0000

Variable Power Supply 1.25 to 35V 10A with Transistor D13007 and LM317

🌐 You can read this article in: Português | Español

A Variable Bench Power Supply 1.25V to 35V with 13007 Transistor and LM317: Transforming Scrap into Professional Equipment

Hello, electronics enthusiasts!

If you’re an engineer, technician, hobbyist, or simply a “Maker” like me, you probably accumulate scrap components at home or in the laboratory. Among the most common treasures found in computer switching power supplies is a very well-known transistor in the maker world: the 13007.

This transistor, designed for fast switching and with excellent collector current capacity, is perfect for our project today: a high-current bench power supply that will transform those forgotten components into an indispensable tool for your projects.

💡 Expert tip: This project demonstrates how it’s possible to reuse components from computer power supplies to create high-quality equipment, saving resources and contributing to sustainability in electronics.

📖 LM317 Voltage Regulator Specifications

The LM317 is a 3-terminal adjustable positive voltage regulator capable of supplying a current of 1.5A over a wide output voltage range of 1.25 to 35 V.

For our bench power supply, however, this maximum current would be limited. This is where the ingenuity of our project comes in: we’ll enhance the circuit with two transistors to create a Booster that will multiply the current capacity of the system.

With this modification, we can easily deliver 10 Amperes with variable voltage between 1.25 to 37 Volts, using just two NPN transistors 13007 (or 13009, which supports up to 12A).

Component	Standard Specification	With Modification
Maximum Current	1.5A	10A
Voltage Range	1.25V – 35V	1.25V – 37V
Additional Component	–	2x 13007 Transistors

🔌 Schematic Diagram

The schematic diagram of the electrical circuit is shown in Figure 2, which shows the arrangement of each component and their connections. As you can see, the assembly is quite simple and straightforward, even for beginners in electronics.

Fig 2 – Schematic Diagram Variable Power Supply 1.25 to 35V 10A

⚠️ Important note: When assembling this circuit, pay special attention to the polarity of components, especially diodes and electrolytic capacitors. An incorrect connection can permanently damage the components.

🛠️ Operation

The 13007 transistors (which may have different prefixes like D13007, MJE13007, SDT13007, etc.) are configured in emitter follower mode. This means that the output voltage through the emitters will be equal to the output voltage of the LM317 IC.

When you adjust the potentiometer of the LM317 to a specific voltage, the two power transistors reproduce this same voltage at their emitters. Since the collectors of these transistors are connected in parallel, forming a high-current bridge, they transform the limited capability of the LM317 (maximum of 1.5A) into a power supply capable of delivering much higher current.

✨ Educational analogy: Think of the LM317 as the “brain” that controls the voltage, while the 13007 transistors function as “muscles” that provide the necessary strength to deliver high current. Together, they form an efficient team where each component plays its ideal role.

The final maximum current capacity will depend on both the transistors used and the specification of the transformer of the power supply that will power this circuit.

🌡️ The Vital Importance of the Heat Sink

Thermal dissipation is one of the most critical aspects in this project. The 13007 transistors operating at high currents generate significant heat that, if not properly dissipated, can lead to catastrophic failures. Think of the heat sink as the cooling system of a high-performance engine – without it, overheating is inevitable.

Excessive heat not only reduces the lifespan of the transistors but also affects the stability of the output voltage. For continuous operations above 5A, a robust heat sink with sufficient area and, ideally, forced ventilation is indispensable.

Don’t skimp on this component! Investing in a good thermal dissipation system, including quality thermal paste, is the difference between a reliable power supply and a frustrating project. Remember: in power electronics, heat is the number one enemy of your project’s longevity.

🧾 Complete Bill of Materials

To build this high-current bench power supply, you will need the following components. We’ve organized the list clearly to facilitate your purchase or inventory check:

Component	Specification	Notes
IC	LM317	Adjustable voltage regulator
T1, T2	MJE13007	NPN power transistors
D1, D2	1N4007	Rectifier diodes
C1	4700 uF – 63V	Main filter electrolytic capacitor
C2	10 uF – 63V	Stabilization electrolytic capacitor
C3	47 uF – 63V	Output electrolytic capacitor
R1	220 ohms	Resistor (red, red, brown)
R2, R3	0.22 ohms – 5W	Power resistors (red, red, gold)
P1	4.7 k ohms	Linear or logarithmic potentiometer
B1, B2	2-way terminal blocks	Solderable type for input and output
Others	Wires, Solder, etc.	Basic assembly material

💡 Expert tip: If you can’t find the 13007 transistor, you can replace it with the 13009, which supports up to 12A of collector current. This will give you an even greater safety margin for your power supply.

🔧 Couldn’t find the 13007 transistor? Don’t worry! We offer an exclusive tool for Transistor Substitution by Data Cross-Reference that helps you find compatible alternatives. Just access our substitution tool, enter the transistor code and get a list of direct substitutes and equivalents that will work perfectly in this circuit.

💡 Assembly and Safety Tips

To ensure the correct and safe operation of your bench power supply, follow these important recommendations:

⚠️ Essential Precautions

Heat dissipation: The 13007 transistors must be mounted on a good heat sink, as they will operate with high currents and generate significant heat. Consider using thermal paste to improve heat transfer.
Isolation: If the transistors are mounted on the same heat sink, use mica insulators to prevent short circuits between the collectors.
Ventilation: For continuous operations at high current, consider adding a small fan to assist in cooling the components.
Adequate transformer: Use a transformer with current capacity compatible with your needs (minimum 10A to take full advantage of the circuit’s potential).

🔍 Circuit Testing and Adjustment

After assembling the circuit, follow these steps to test and adjust your power supply:

Initial check: Before powering on, check all connections, especially the polarity of diodes and electrolytic capacitors.
No-load test: Connect a multimeter to the output and turn the potentiometer to check if the voltage varies correctly between 1.25V and approximately 37V.
Load test: Connect a resistive load (such as a lamp or power resistor) and check if the power supply maintains the regulated voltage.
Temperature monitoring: During testing, monitor the temperature of the transistors and the LM317. If any component heats excessively, turn off immediately and check the connections.

👉 Possible Improvements and Modifications

After building your basic power supply, you can consider these improvements to make it even more versatile:

Adding voltmeter and ammeter: Install digital meters for direct visualization of output voltage and current.
Current limiting: Implement an overcurrent protection circuit to protect your projects.
Polarity reversal protection: Add a diode at the input to protect the circuit against incorrect connections.
Multiple outputs: Create fixed output terminals (such as 5V and 12V) in addition to the variable output.

🤔 Frequently Asked Questions (FAQ)

We’ve gathered some of the most common questions about this project to help you:

❓ Can I use other transistors besides the 13007?🔽

13.8V 10A SMPS Power Supply Using IR2153 and IRF840 – With PCB

Electronic Circuits — Mon, 30 Jan 2023 16:02:00 +0000

Switched-Mode Power Supply SMPS 13.8V 10A with IR2153 and IRF840 + PCB

🌐 You can read this article in: Português | Español

Hello, electronics enthusiasts!

Today we’re going to dive into the fascinating world of SMPS (Switched-Mode Power Supply) with a practical and powerful project: a 13.8V power supply capable of delivering up to 10A of continuous current! This project uses the efficient PWM controller IR2153 and the robust MOSFET transistors IRF840, components that together form an unbeatable combination in terms of cost-effectiveness and performance.

Whether you’re a student, a professional in the field, a designer, or a hobbyist looking for a reliable power supply for your applications, this article is for you! We’ll unravel each step of this circuit together, from theory to practice, with clear and detailed explanations.

🔍 What is a Switched-Mode Power Supply (SMPS)?

Before diving into the project, let’s understand what makes switched-mode power supplies so special. Unlike traditional linear power supplies, which dissipate excess energy as heat, SMPS operate with high-frequency switching, resulting in higher energy efficiency and reduced size.

Think of an SMPS as an intelligent system that rapidly “turns on and off” the power, adjusting it to provide exactly what your circuit needs. This switching process occurs at very high frequencies (typically above 20kHz), allowing the use of smaller and lighter components.

🔧 Detailed Circuit Analysis

Our 13.8V 10A SMPS power supply project can be divided into 8 fundamental stages, each playing a crucial role in the overall functioning of the circuit. Let’s explore each of them:

📊 Structure of the Switched-Mode Power Supply (SMPS)

Protection Circuit
Transient Filter
Primary Rectification
Primary Filter
Switching Stage
High-Frequency Transformer
Fast Rectification
Output Filter

1️⃣ Protection Circuit

Safety comes first! Our protection circuit consists of a 5A/250V Fuse, which acts as a bodyguard, interrupting the circuit in case of a dangerous overcurrent. In parallel, we have an NTC (Negative Temperature Coefficient), a special thermistor that limits the initial surge current.

Think of the NTC as an “intelligent traffic light” for electricity: when the circuit is turned on, it offers high resistance, limiting the initial current. As it heats up, its resistance decreases, allowing normal current flow to occur. This topology is found in most modern SMPS, such as those in laptops and computers.

2️⃣ Transient Filter

This stage acts as a “traffic guard” for electricity, preventing high-frequency noise from traveling between our circuit and the power grid. It consists of an initial capacitive filter (C1, C2) that inhibits high frequencies from returning to the grid, and an EMI (Electromagnetic Interference) filter choke, which attenuates the noise generated by switching.

3️⃣ Primary Rectification

Here, the alternating current from the power grid (110V or 220V) is converted into pulsating direct current through the rectifier bridge D1. It’s as if we’re transforming the bidirectional flow of electricity into a unidirectional flow, preparing it for the next stages.

4️⃣ Primary Filter

The capacitors C3 and C4 act as energy reservoirs, smoothing the ripple of the pulsating direct current and providing a more stable voltage for the switching stage. Think of them as small “energy lakes” that ensure a constant flow.

5️⃣ Switching Stage

This is the “magic” of the switched-mode power supply! The heart of this stage is the IR2153 IC, a PWM (Pulse Width Modulation) controller that generates high-frequency signals to control the MOSFET transistors Q1 and Q2 (IRF840). These transistors function as ultra-fast switches, turning on and off at high frequency to “slice” the direct voltage into high-frequency pulses.

The IR2153 is particularly interesting because it already incorporates a driver for MOSFETs in its 8-pin package, significantly simplifying the design and reducing the component count.

6️⃣ High-Frequency Transformer

Unlike conventional transformers that operate at 60Hz, our Chopper Transformer operates at high frequency, allowing a drastically reduced size with the same power capacity. It is responsible for two crucial functions: galvanically isolating the output circuit from the power grid (essential for safety!) and transforming the high voltage of the primary to the low voltage needed in the secondary.

7️⃣ Fast Rectification

In the secondary of the transformer, we need to convert the high-frequency pulses back into direct current. For this, we use the fast diode D3 (MBR3045PT), which is capable of operating efficiently at the high frequencies generated by our circuit. Common diodes would not be suitable here due to their slow recovery time.

8️⃣ Output Filter

Finally, the inductor L2 and the capacitor C9 form an LC filter that smooths the residual ripple, providing a clean and stable output voltage of 13.8V. It’s the last barrier between the rectified pulses and the perfectly usable energy that will power your projects.

⚠️ WARNING! ⚠️

This circuit operates directly connected to the power grid, which represents a risk of serious or fatal electric shock. Any carelessness, incorrect connection, or design error can lead to irreversible damage to equipment or even personal accidents.

We are not responsible for any type of occurrence. If you do not have sufficient experience with circuits connected to the power grid, do not assemble this circuit. If you decide to assemble it, use all appropriate protections and, if possible, perform the tests accompanied by another person.

⚡ The IR2153 PWM Controller in Detail

The IR2153 is the brain of our switched-mode power supply. This integrated circuit from International Rectifier (now part of Infineon) is specifically designed for half-bridge applications in switched-mode power supplies, combining an oscillator with MOSFET drivers in a single package.

The IC is powered through the power resistor R3 (27K 5W) together with the capacitor C5. Internally, the IR2153 already has a 15.6V Zener diode to regulate its power supply, but the available current is limited. Therefore, it’s crucial not to use a resistor R3 with a value lower than specified, as this could overload and damage the IC.

An interesting improvement would be to add an external 15V Zener diode in parallel with the IC’s power supply, providing additional protection and greater stability.

It’s worth highlighting an important difference between the IR2153 and the IR2153D: the “D” model already incorporates internally the diode D2 (FR107 or BA159) necessary for the proper functioning of the circuit. If you’re using the IR2153D, you can omit this component. If it’s the IR2153 (without the “D”), keep the diode D2 as shown in the schematic.

🔌 Complete Schematic Diagram

Now that we understand each part of the circuit, let’s examine the complete schematic diagram in Figure 2. This is the moment when all the pieces of the puzzle fit together, forming a cohesive and functional system.

Figure 2 – Schematic Diagram SMPS Power Supply 13.8V 10A

🔧 The Transformer: Heart of the Switched-Mode Power Supply

The transformer TR1 is a critical component in our power supply. For this project, we used a transformer model IE-35A recovered from a scrap ATX power supply. The good news is that practically any ATX power supply transformer can be used, as long as we follow the correct pinout.

One of the great advantages of this project is that there is no need to rewind the transformer! You just need to correctly identify the terminals and connect them as shown in Figure 3 below. This approach saves time and eliminates one of the most complex steps in building switched-mode power supplies.

Fig. 3 – ATX power supply transformer connection diagram

In addition to the EI-35A model, other transformers from AT or ATX power supplies can be used, such as the models EI-33, ER35, TM3341101QC, ERL35, EI28, among others. Figure 4 shows an example of the EI-35A transformer we used:

Fig. 4 – ATX power supply transformer model EI-35A

As for the inductors L1 and L2, both can be salvaged from the original ATX power supply. The inductor L1 is the input EMI filter, while L2 is the output filter. If you prefer to build your own filter, you can wind an inductor on a ferrite toroidal core using 0.6 mm enameled copper wire with approximately 25 turns.

📝 Complete List of Components

To facilitate your assembly, we’ve compiled a detailed list of all the necessary components for this project:

Component	Specification	Notes
IC1	Integrated Circuit IR2153D or IR2153	See text for differences
Q1, Q2	MOSFET Transistors IRF840	Can be replaced by equivalents
R1, R2	150k Resistor	(brown, green, yellow, gold)
R3	27K 5W Resistor	(red, violet, orange, gold)
R4	8K2 Resistor	(gray, red, red, gold)
R5, R6	10Ω Resistor	(brown, black, black, gold)
D1	KBU606 Diode Bridge	Or equivalent
D2	Fast Diode FR107 or BA159	Not needed with IR2153D
D3	Fast Diode MBR3045PT	Or equivalent
C1, C2	470nF – 400Vac Polyester Capacitor	X2 Class
C3, C4	330uF – 200V Electrolytic Capacitor	Low ESR recommended
C5, C7	100uF – 25V Electrolytic Capacitor	Low ESR recommended
C6	680pF Polyester Capacitor	Polystyrene recommended
C8	2.2uF – 400V Polyester Capacitor	Polypropylene recommended
C9	2200uF – 25V Electrolytic Capacitor	Low ESR recommended
RV1	47kΩ Trimpot	For voltage adjustment
NTC1	5Ω Thermistor	Surge current limiter
L1, L2	Inductors	See text
TR1	Transformer	See text
F1	5A Solderable Fuse	Overcurrent protection

🖨️ Printed Circuit Board (PCB)

To facilitate your assembly, we’ve made the PCB (Printed Circuit Board) files available in different formats, covering all your needs, whether for a homemade assembly or for sending to a professional fabrication.

The files are available in GERBER format (for professional fabrication), PDF (for viewing and printing) and PNG (for visual reference). And best of all: they are available for free download directly from the MEGA server, through a direct link, without any complications or redirections!

Fig. 5 – PCB Switched-Mode Power Supply SMPS 13.8V 10A with IR2153 and IRF840

📥 Download Files

To download the necessary files for assembling the electronic circuit, just click on the direct link provided below:

Link to Download: Download Files (PCB Layout, PDF, GERBER, JPG)

🤔 Frequently Asked Questions (FAQ)

To ensure your project is a success, we’ve compiled some of the most common questions on this topic. Check it out!

Can I use other MOSFET models besides the IRF840? 🔽

1.5V-28V 7.5A Adjustable Symmetrical Power Supply using LT1083 IC with PCB

Electronic Circuits — Sun, 06 Mar 2022 20:20:00 +0000

Fig.1 - 1.5V to 28V, 7.5 Amps Adjustable Symmetric Power Supply using IC LT1083 with PCB

Versatile Power at Your Fingertips: Build an Adjustable 1.5V to 28V, 7.5 Amps Symmetric Power Supply with IC LT1083 and PCB

This is a power supply designed to be used in a technical bench, based on the LT1083 integrated circuit, which is an adjustable 3-terminal positive voltage regulator.

Which provides a current of 7.5A in a variable output voltage range of 1.5 to 28V, and even has short circuit and over temperature protection.

The Circuit provides a symmetrical output, which pleases all of us engineers, technicians and designers, this type of power supply, as it brings us great efficiency for application in technical benches, mainly for testing audio amplifiers.

📖 LT1083 IC Description

The LT1083 positive adjustable regulator is designed to provide 7.5A with higher efficiency than currently available devices.

In Figure 2 - You'll find the description of the input, output and ground pins. There are other types of encapsulation, as this TO - 3P is the most common.

Fig. 2 - Pinout LT1083

All internal circuitry is designed to operate down to 1V input to output differential, and the dropout voltage is fully specified as a function of load current.

Dropout is guaranteed at a maximum of 1.5V at maximum output current, decreasing at lower load currents.

On-chip trimming adjusts the output voltage to 1%. The current limit is also trimmed, minimizing the stress on both the regulator and power source circuitry under overload conditions.

The LT1083 series devices are pin compatible with older three terminal regulators. A 10μF output capacitor is required on these new devices; however, this is usually included in most regulator designs.

Unlike PNP regulators, where up to 10% of the output current is wasted as quiescent current, the LT1083 quiescent current flows into the load, increasing efficiency.

🛠️ Features

Three-Terminal 3.3V, 3.6V, 5V, 12V or Adjustable
Output Current of 3A, 5A or 7.5A
Operates Down to 1V Dropout
Guaranteed Dropout Voltage at Multiple Current Levels
Line Regulation: 0.015%
Load Regulation: 0.1%
100% Thermal Limit Functional Test
Adjustable Versions Available

🤔 How the Circuit Work

The circuit operation is quite simple, and its operation is applied with an artifice that we did to join two adjustable power sources into one.

Since we don't have "as far as I know", a regulator of the same negative line, like what happens with the regulators LM317, LM7812 and etc.

The bridges of diodes KBPC5010 D1 and D4, are responsible for rectifying the circuit, this diode bridge is able to support currents up to 50A.

I know it's an exaggeration, but it was what I had here, you can be putting with lower current, as the KBPC1510, for 15A, or the KBPC1010 for 10A.

The capacitors C1 and C3, are electrolytic capacitors responsible for filtering the circuit, we use them of 10,000uF, but if you don't have one you can put one of 8,000uF. Remembering that they have to be able to avoid Ripple in the power supply.

The resistors R1 and R3 are the limiters for LED1 and LED2, which are used as voltage signaling for the two sources.

The voltage that comes already rectified and filtered enters the Positive Voltage Regulators, as we can see in the circuit, they are identical circuits, and through the double potentiometer the output voltage regulation is done, ranging from 1.5V to 28V.

The diodes D2, D3, D5, and D6, are for reverse voltage protection that can arise from the circuit and damage the Regulators, and the diodes protect these voltages in the regulators.

The resistors R2 and R4, are responsible for the Feedback voltage, or feedback, they keep the output voltage stable, they are resistors that if you have conditions, put the ones with low error percentage, such as precision resistors with 1%.

And finally, the capacitors C2 and C4, are for spurious filter, if you can afford it, it is preferable tantalum capacitors.

🔌 The Circuit Diagram

The complete schematic diagram of the power supply is shown below in Figure 3, it is a simple but complete adjustable symmetric power supply.

Fig. 3 - Schematic Diagram 1.5V to 28V, 7.5 Amps Adjustable Symmetric Power Supply using IC LT1083

⚡ The Power Transformer

The transformer must be symmetrical with center tape open, this means that it will to have two independent winding: "2 Wire + 2 Wire", as illustrated in Figure 4 below.

Fig. 4 - Symmetrical Transformer with Independent secondary winding

The transformer must be able to supply 8A at the symmetrical output. The primary voltage, "input voltage", must correspond to the voltage in your area; 110V or 220Vac.

The secondary voltage, "output voltage", should be 21Vac in each coil, because after rectification it will supply the circuit with 30Vdc.

🧮 Component List

Semiconductors
- U1, U2 .................. LT1083 Voltage Regulator
- D1, D4 .................. KBPC5010 - 50A Rectifier Bridge *See Text
- D2, D3, D5, D6 .... 1N4007 Diode Rectifier
- LED1, LED2 ........ Light Emitter Diode (General Use)
Resistors
- R1, R3 ....... 2K7Ω 1/8w Resistor (red, violet, red, gold)
- R2, R4 ....... 120Ω 1/8w Resistor (brown, red, brown, gold)
- RP1 ........... 5KΩ Double Potentiometer
Capacitors
- C1, C3 ........ 10.000uF - 45V Electrolytic capacitor
- C2, C4 ........ 10uF - 45V Electrolytic capacitor
Miscellanies
- P1, P2 ........ Connector 2 screw terminal 5mm 2 Pins
- P3 .............. Connector 3 screw terminal 5mm 3 Pins
- Others ....... Wires, Power Transformer, Solders, pcb, heat sink, etc.

🖨️ Printed Circuit Board - Download

We provide the files with the PCB, the schematic, the PDF, GERBER and JPG, PNG and provide a direct link for free download and a direct link, "MEGA".

Fig. 5 - PCB - 1.5V to 28V, 7.5 Amps Adjustable Symmetric Power Supply using IC LT1083

📥 Files to Download, Direct Link:

Click on the direct link to download the files: Layout PCB, PDF, GERBER, JPG

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

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The ElCircuits Team ⚡

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High Precision 5V 3A Voltage Regulator using TL431 + PCB

Electronic Circuits — Fri, 03 Dec 2021 00:25:00 +0000

Circuits with a high level of sensitivity require a stable supply, they are generally difficult to be powered by power supplies, due to the high level of sensitivity needed to provide stable voltage in the circuit.

However, we are introducing a stabilized power supply with an accurate output to power any sensitive circuit, such as microcontroller circuits, microprocessor circuits, RF transmission, PICs, and so on.

Today we are going to build a very precise circuit, which uses a very well-known component that is widely used in SMPS power supplies, especially ATX PC power supplies, “which looks more like a transistor”.

The 3-Pin TL431 Integrated Circuit, It offers better stability, less temperature deviation (VI (dev)) and less reference current (Iref) for greater system accuracy.

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The TL431 device is an adjustable tap regulator with thermal stability specified in applicable automotive, commercial, and military temperature ranges.

The output voltage can be set to any value between Vref (approximately 2.5V) to 36V, with two external resistors. These devices have a typical output impedance of 0.2 Ω.

The active output circuitry provides a very crisp activation characteristic, making these devices excellent replacements for Zener diodes in many applications such as integrated regulation, tunable power supplies and switched power supplies.

Characteristics

Reference voltage tolerance at 25°C
0.5% (class B)
1% (class A)
2% (standard class)
Adjustable output voltage: Vref to 36V
Operation from -40 °C to 125 °C
Typical temperature deviation (TL43xB)
6 mV (temperature C)
14 mV (I Temp, Q Temp)
Low output noise
0.2 Ω typical output impedance
Sink current capacity: 1 mA to 100 mA
Application
Adjustable voltage and current reference
Secondary lateral adjustment in Flyback SMPSs
Zener Replacement
Voltage monitoring
Comparator with integrated reference

The Diagram Circuit

In Figure 2 below, we have the schematic diagram of the High Precision Voltage Regulator Circuit with TL431 IC, with LM350 IC, provides a current of up to 3 Amps.

Fig. 2 – High Precision 5 Volts 3 Amp Voltage Regulator Circuit – TL431

With the TL431 IC, they provide a precise 5V output, which is often necessary for precision microcontrollers, sensitive equipment, that require a stabilized voltage, this circuit is ideal for that.

The power supply must provide a current of at least 3 Amps. Its input voltage must be greater than 7 Volts, to avoid overheating the LM350 IC, voltages no greater than 15V must be used.

🖨️ Printed Circuit Board (PCB) – Download

We provide files with the PCB, schematic, PDF, GERBER and JPG, PNG and provide a direct link for free download and a direct link, “MEGA“.

📥 Files to Download, Direct Link:

Click on the link beside: Layout PCB, PDF, GERBER, JPG

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,

The ElCircuits Team ⚡

O post High Precision 5V 3A Voltage Regulator using TL431 + PCB apareceu primeiro em Electronic Circuits.