How Does a 24V Switching Power Supply Work?

Understanding the inner workings of a 24V switching power supply is crucial for anyone who designs and operates electronic systems. This article will explore the operation of a switching power supply and specifically how it achieves a stable 24V output.

Block Diagram Overview

A 24V switching power supply, whether AC-DC or DC-DC, operates on the principle of converting the input power source to a stable output voltage, typically 24V. The block diagram of such a power supply is representative of many AC-DC or DC-DC power supplies. The key differentiator between an AC-DC and a DC-DC power supply is the presence of a diode bridge rectifier in AC-DC power supplies. This rectifier is not present in DC-DC power supplies as they already receive a DC input.

Simplified Block Diagram of AC-DC Switching Power Supply

Operation of a Switching Power Supply

A switch mode power supply (SMPS) works by converting the input power source - typically mains voltage - to DC, then switching at high frequencies to process the DC, which creates high-voltage, high-frequency pulsating DC signals. These signals are then stepped down using a small power transformer to a voltage level appropriate for the output, which is rectified and filtered to achieve a steady, constant voltage output of 24V.

Simplified Explanation

Here's a simplified explanation of the operation of an SMPS, independent of the specific voltage input:

**Input Conversion**: The first step is the conversion of the input AC or DC power to DC.

**Frequency Switching**: The DC is then switched on and off at high frequencies.

**Transformer Action**: A small power transformer is used to step down the high-voltage, high-frequency signals to a voltage level suitable for the desired output (24V in this case).

**Rectification and Filtering**: The transformer's output is rectified and filtered to produce a stable, regulated 24V DC output.

**Control Circuitry**: Additional control circuitry monitors the output voltage and adjusts the high-frequency switching as required to maintain stability.

Advantages and Disadvantages of SMPS

The primary advantage of an SMPS over a simple linear power supply is its efficiency. An SMPS can use relatively small and light transformers, making it cost-effective and suitable for portable or low-power applications. However, SMPSs also come with certain challenges:

Efficiency**: High efficiency, especially for low loads, where linear supplies would otherwise waste power as heat.