Inside a Power Supply: Key Components and How They Work
Power supplies are an integral part of a wide range of electronic devices. From simple household appliances to complex industrial systems, power supplies are everywhere. While they may differ in design, they share one common purpose: to convert electrical energy from a source into a form suitable for individual electronic systems. In this article, we’ll take a closer look at transformer and switching power supplies, and discuss their key components and safety features in detail.
Transformer and Switching Power Supplies
Transformer Power Supplies
Transformer power supplies are one of the oldest and simplest types of power supplies. Their main component is a transformer, which reduces the mains voltage to a level suitable for the devices. These power supplies feature simple construction, high output voltage stability, but are lower in efficiency and larger in size compared to switching power supplies.
Key components:
Transformer: Steps down the mains voltage from AC to a lower level required for further conversion.
Rectifier: Most often a bridge, converts the voltage from AC to DC.
Filter: Capacitors smooth the voltage, eliminating ripple.
Voltage regulator: Maintains a constant voltage despite fluctuations in the load and input voltage.
Operation:
The transformer steps down the voltage, and the rectifier converts the AC to DC. The capacitors then capture voltage noise, providing a stable power supply for connected devices. The stabilizer ensures that the output voltage remains constant despite fluctuations.
Switching Mode Power Supplies (SMPS)
Switching Mode Power Supplies (SMPS) are more energy efficient and smaller than linear power supplies. Their operating principle is based on high-frequency conversion, which allows the use of smaller and lighter transformers.
Key components:
Converter: Converts the DC voltage and operates at high frequency.
HF transformer: Small size due to high-frequency operation.
Rectifier: A second DC rectifier provides back conversion to DC after the transformation.
Capacitors and inductors: Filter and smooth the voltage, similar to linear power supplies.
Control circuit: Manages the operation of the transistor switches and voltage stabilization.
Operation:
Switching power supplies convert the mains voltage to DC, convert it to an HF signal through a converter, transform it to the desired voltage level, and then rectify it back to DC. High operating frequency allows the use of smaller passive components and minimizes energy losses.
Protections in power supplies
Power supplies are equipped with a number of protections that protect both the power supply itself and the devices connected to it from various types of damage.
Overload protection
These protections prevent overloads that can damage the power supply. By detecting excessive current flow, the power supply can reduce output power or completely cut off the power supply, thus protecting other circuit elements.
Operation: Uses mechanisms to measure the current intensity at the output. When a safe threshold is exceeded, protection is activated, cutting off or releasing the current.
Short-circuit protections
Protects against short circuits at the PSU output, which could lead to serious damage to both the PSU and connected devices.
Operation: During reconnaissance, the PSU automatically shuts down or enters protected mode to reduce current flow.
Thermal protections
These protections prevent the PSU from overheating due to excessive load or inappropriate external conditions.
Operation: Detects temperature using thermal sensors. When temperatures approach dangerous levels, the power supply may reduce power or shut down.
Surge Protection
These protections protect the power supply and connected devices from sudden voltage spikes that can damage sensitive electronics.
Operation: Monitors voltage and isolates components when anomalies are detected. This is done using devices such as surge arresters or varistors.
Key Components in Power Supplies
Transformer
Function and Design
The transformer in a power supply is designed to reduce the voltage from AC line voltage to a lower level required for further conversion and use. The transformer accomplishes this through the principle of electromagnetic induction, using a pair of windings (primary and secondary)