Product Overview
The AC-DC 5V 700mA Power Supply Buck Converter is a compact, high-efficiency switch-mode power supply (SMPS) module designed to convert high-voltage AC mains power (85V–265V AC) into a stable, low-voltage DC output suitable for powering microcontrollers, sensors, LED strips, and other 5V electronic devices . Rated at 3.5 Watts (5V @ 700mA), this industrial-grade module eliminates the need for bulky traditional transformers, providing a safe, reliable, and space-saving power solution for embedded projects and consumer electronics.
Unlike simple linear regulators that waste energy as heat, this module uses advanced switching technology to achieve up to 85% efficiency while running cool . Its built-in isolation transformer ensures that the low-voltage DC output is completely isolated from the hazardous AC input, protecting your sensitive circuits and improving user safety .
This “New” version is built with modern protection features including overcurrent protection (OCP), short-circuit protection (SCP), and over-temperature protection (OTP) , ensuring automatic shutdown under fault conditions to prevent damage to the module and your connected devices . Measuring only about 30x20x18mm, its tiny footprint makes it perfect for embedding into IoT devices, Arduino projects, LED drivers, and smart home systems where space is at a premium .
Key Features
-
Compact High-Power Density: Converts 220V wall power directly to 5V DC in a module the size of a postage stamp (approx. 30x20x18mm), replacing bulky traditional power supplies .
-
Industrial-Grade Safety: Features high and low voltage isolation, built-in temperature protection, overcurrent protection, and short circuit protection for reliable operation in DIY and commercial settings .
-
Wide Input Voltage Range: Accepts global mains voltage from 85V to 265V AC (50/60Hz), making it compatible with any standard household outlet worldwide .
-
Stable Regulated 5V Output: Provides a clean, stable 5V DC output (±0.2V accuracy) thanks to the built-in 431 precision voltage reference circuit .
-
High Efficiency and Low Heat: With an efficiency rating of up to 85% (typical) , it minimizes energy waste and heat generation, allowing for longer operation in enclosed spaces .
-
Multiple Protections: Fully protected against short circuits, overloads, and over-temperature events. The output automatically recovers once the fault is resolved or the device cools down .
-
Low Ripple and Noise: Engineered for stable DC power with a ripple and noise specification of 60mV, ensuring clean power for sensitive electronics .
-
Easy PCB Mount Integration: Designed with standard pin headers, it can be soldered directly onto a PCB or fixed with glue for permanent installation in appliances and automation systems .
Technical Specifications
Pinout & Connection Guide
The module uses a standard 4-pin configuration (2 for AC Input, 2 for DC Output) with a 2.54mm pin pitch for easy breadboard or PCB mounting.
Input Terminals (AC High Voltage Side)
Output Terminals (DC Low Voltage Side)
Wiring Warning: Ensure the AC wiring is properly insulated and kept separate from the DC output side to maintain safety isolation. Always connect AC power through a switch and fuse for permanent installations.
Usage Guide
Step 1: Safety First
IMPORTANT: This module deals with potentially lethal high voltage. Ensure all AC wiring is done with the device unplugged. Use appropriate wire gauges (20-24 AWG is sufficient) and ensure good insulation to prevent short circuits.
Step 2: Connect AC Input
Step 3: Connect DC Load
-
Connect your 5V device (Arduino, ESP32, Relay module, LEDs) to the DC+ (5V) and DC- (GND) terminals.
Step 4: Power On
-
Plug the device into a standard AC outlet (110V or 220V).
-
Do not touch any part of the AC side once powered.
-
The module will instantly provide regulated 5V DC power up to 700mA.
Application Note
Because this module operates at high frequency (switching), it is much more efficient than a standard 50/60Hz linear transformer. However, it may introduce high-frequency noise (ripple) into the DC output. For powering sensitive analog circuits (like audio preamps), adding a low-ESR filter capacitor (e.g., 100µF or 470µF electrolytic) on the 5V output can help reduce ripple.
Q: Can I use this module to power an Arduino Uno or Nano?
Yes, absolutely. This module is an excellent way to power an Arduino directly from a wall outlet. Simply connect the 5V output to the Arduino’s 5V pin (not the VIN pin) and the GND to GND. It provides a clean, regulated 5V without the need for an external USB adapter.
Q: What is the difference between this "Switch Mode" module and a traditional transformer?
Traditional transformers are heavy, large, and inefficient (often running hot). This is a Switch Mode Power Supply (SMPS) . It uses high-frequency switching to convert power, making it significantly smaller, lighter, and more efficient (up to 85%) . It also includes isolation for safety.
Q: Is this module truly isolated?
Yes. The module uses a built-in high-frequency transformer to provide galvanic isolation between the high-voltage AC input and the low-voltage DC output. This means there is no direct electrical path between the AC mains and your device, making it safer .
Q: What happens if I accidentally short the 5V output?
The module features Short Circuit Protection (SCP) . If the output is shorted, the module will automatically shut down to protect itself from damage. Once the short is removed and the module is power-cycled (or in some cases, recovers automatically), it will resume normal operation.
Q: Can I use a 5V 700mA module to power a device that draws only 200mA?
Yes. The device will only draw the current it needs (200mA). The 700mA rating is the maximum capacity the power supply can safely provide. Running a lower load is perfectly safe and often increases the lifespan of the power supply.
Q: Why does the low-voltage DC output not reach a full 5.00V?
The module has a tolerance of ±0.2V, meaning the output can range between 4.80V and 5.20V . This slight variation is within standard USB specifications and will run virtually all 5V electronics perfectly. If you require extremely precise voltage, consider using a buck converter with a feedback trimmer.
Q: Can I use 12V DC as an input to this "AC-DC" module?
While the datasheet mentions a DC input range (100-370V DC) , the module is optimized for AC. You can technically use high-voltage DC, but 12V is far too low to power a 5V AC-DC converter designed for mains voltage. For 12V input, you need a separate DC-DC buck converter.
Q: Is there a risk of electric shock from the output side?
No, not under normal conditions. The 5V output is considered Safety Extra Low Voltage (SELV). Because the module is isolated, you cannot get a shock from touching the 5V wires (though you should never touch the AC input side).
Q: Can I use this module to charge a Lithium-Ion battery (3.7V)?
No, not directly. This is a Constant Voltage (CV) power supply. A Li-Ion battery requires a Constant Current/Constant Voltage (CC/CV) charging profile. Using this directly could over-current and damage the battery. You must use a dedicated TP4056 or similar charging module between this power supply and your battery.
Q: My module is getting warm. Is this normal?
Yes, at near maximum load (700mA), the module will generate some heat due to the 15-20% inefficiency (resulting in about 0.5-0.7W of heat). This is normal. However, if it is too hot to touch, ensure there is adequate airflow and that you are not exceeding the 700mA limit. The module also includes over-temperature protection to shut down if it gets dangerously hot .
