XP Power Technical Guide: In Depth Analysis of AC/DC Conversion, System Topology, and High Reliability Design

XP Power Technical Guide: In Depth Analysis of AC/DC Conversion, System Topology, and High Reliability Design

Introduction

Virtually every piece of electronic equipment is powered from a low voltage DC supply. This source will be either a battery, a combination of battery and DC/DC converter or a power supply converting AC mains into one or more low voltage DC supplies, suitable for electronic components. Electronic components require a DC supply that is well regulated, has low noise characteristics and provides a fast response to load changes. AC power supplies, and most DC/DC converters, also provide isolation from the input to the output for safety, noise reduction and transient protection.

As electronic equipment has become smaller, the market has demanded that power converters do the same. Since the introduction of switch mode techniques, this has been an evolutionary rather than a revolutionary process. Conversion efficiency has increased, materials and components allowing higher switching frequencies have become available and packaging techniques have advanced. At the same time, unit cost has fallen as volumes have increased. With the global market for electronics becoming a reality, power supply systems operate from wide input ranges to cover worldwide AC mains supply variations.

There are a number of basic topologies used in power converters, which are suited to various power levels, cost criteria and performance levels. These are briefly discussed below.

1、 Fundamentals of Power Conversion: Linear and Switching Mode (SMPS)

Almost all electronic devices require a low-voltage direct current (DC) power supply. The ideal DC power supply should have good voltage stability, low noise characteristics, and fast response to load changes.

1.1 Linear Power Supplies

Advantages: Extremely low noise, high reliability, low, commonly used in low-power applications such as audio that are sensitive to cost noise.

Disadvantages: Large size, heavy weight, low efficiency, limited input voltage range.

1.2 Switch Mode Power Supply (SMPS)

To significantly reduce size and improve efficiency, most applications use switch mode power supplies (SMPS). SMPS increases the operating frequency, reduces the physical size of transformers, inductors, and capacitors, and uses "on or off" switching elements to improve efficiency. The trade-off point of using this technology increases the ripple and noise of the output DC power supply, as well as the need to manage the emergence of radiated electromagnetic interference (EMI).

2、 Analysis of Core Switching Power Supply Topology Structure

Different power levels, costs, and performance requirements determine the selected power topology.

Topology structure, typical power range, key characteristics

Isolated flyback converter (isolated flyback converter), up to 150W, with the lowest cost and simple structure, using only one unstable component (connection interference).

Forward type (forward type), 100-300 watts, using inferior components (transformer and output components), energy is transmitted during the conduction period of the switching element.

Half bridge and full bridge (half bridge and full bridge)+1150 watts -1000 watts, with higher utilization of transformer cores, commonly used in AC input power supplies, and full bridge can provide twice the output power.

Boost Converter and PFC, above 100W, are used to boost input voltage and are most commonly used in AC input power supplies. They are configured with Active Power Factor Correction (PFC).

3、 System reliability, thermal management, and regulatory compliance

The long-term operation of the system relies on comprehensive thermal management and strict compliance with industry regulations.

3.1 Impact of Thermal Management on Reliability

MTBF (Mean Time Between Failures): Experience has shown that for every 10 ° C increase in temperature, MTBF decreases by half.

Design objective: The goal is to maintain the temperature of key components inside the power supply below the safe operating temperature to ensure sufficient capture life. In the absence of improving Atlanta's capacity through the Atlanta area, mandatory windproof cooling is a necessary measure.

Power module: For the power module, it is necessary to use the previously designed heat sink and bottom plate (bottom plate) to dissipate the remaining heat to the maximum extent possible.

3.2 Key Regulations and Energy Efficiency Trends

Power safety standards: Power supplies must comply with relevant safety standards, such as information technology equipment standards (IEC 60950), medical equipment standards (IEC 60601), or measurement and control equipment standards.

Electromagnetic compatibility (EMC): covers compliance with radiation, immunity, and CE marking.

No load power consumption: One of the latest legislative trends in the power industry is the requirement for no-load power consumption and efficiency of external power sources.

4、 Technological Frontier: Configurable Power Supply and Efficient Design

In order to quickly meet market demand and highly customized requirements, configurable power solutions are becoming increasingly important.