AC-DC|Basic
Transformer vs Switching
2015.09.03
Points of this article
・Although the switching system is now becoming the mainstream method for power conversion, we need a solid understanding of issues particular to the switching system.
In the previous sections we provided an overview of transformer and switching system-based AC-DC conversion in terms of operation and circuits. In this section we attempt to summarize their pros and cons.
In terms of circuit configuration, due to differences in the conversion methods employed, the switching system is more complicated. In addition, the switching system requires a control circuit (basically an IC).
Although the two systems are similar in the components used, the switching system requires some higher voltage tolerant parts, with some cost implications, as would be expected.
Nevertheless, the most significant difference lies in efficiency, and in terms of volume/weight the switching system is considered more advantageous.
As an example, have you noticed that charging wall adapters for portable devices have recently become smaller and lighter? Figure 11 illustrates commonly available wall adapters. The left unit is a transformer system while the right unit is a switching system. In terms of specifications, the right unit, smaller in size, features an output value that is greater by as much as 1W.
In the switching system, the AC input (50/60Hz) which has been converted to DC is converted back to high-frequency AC, permitting the use of smaller transformers and output capacitors, thus substantially reducing the form factor. In the section on basic operations we stated that “the switching system, after rectifying and smoothing of the input AC, operates in the same manner as a DC-DC converter,” and this is also precisely true for the switching wall adapter. In terms of efficiency also, the switching permits the extraction exclusively of the required power, for improved efficiency, and obviously, reduced heat dissipation.
In any design process, a tradeoff between efficiency, size, and cost must be taken into consideration. With a solid understanding of the differences and pros and cons of these systems, we believe that optimal choices can be made. Recently, the issue of power consumed by AC adapters during their standby status has been noted. A solution may be at hand in the adoption of the switching system.
【Download Documents】Basics of AC-DC Converter and Design Procedures
A hand book for beginners to AC-DC converter design, covering the basics of AC-DC conversion and various conversion methods, as well as the procedures and issues involved in designing an AC-DC converter.
AC-DC
Basic
- AC-DC Basics
- DC-DC Conversion (Regulated) System after Smoothing
- Design Procedure for AC-DC Conversion Circuits (Overview)
- Issues and considerations in AC-DC Conversion Circuit Design
- Summary
Design
- Overview of Design Method of PWM AC-DC Flyback Converters
- Want are Isolated Flyhback Convertors?
- Isolated Flyback Converter Basics: What is Switching AC-DC Conversion?
- Isolated Flyback Converter Basics: What are Characteristics of Flyback Converter?
- Isolated Flyback Converter Basics: Flyback Converter Operation and Snubber
- Isolated Flyback Converter Basics: What are Discontinuous Mode and Continuous Mode?
- Design Procedure
- Determining Power Supply Specifications
- Choosing an IC for Design
- Designing Isolated Flyback Converter Circuits
- Designing Isolated Flyback Converter Circuits: Transformer Design (Calculating numerical values)
- Designing Isolated Flyback Converter Circuits: Transformer Design (Structural Design) – 1
- Designing Isolated Flyback Converter Circuits: Transformer Design (Structural Design) – 2
- Designing Isolated Flyback Converter Circuits: Selecting Critical Components ? MOSFET related – 1
- Designing Isolated Flyback Converter Circuits: Selecting Critical Components ? MOSFET related – 2
- Designing Isolated Flyback Converter Circuits: Selecting Critical Components ? CIN and Snubber
- Designing Isolated Flyback Converter Circuits: Selecting Critical Components ? Output Rectifier and Cout
- Designing Isolated Flyback Converter Circuits: Selecting Critical Components ? VCC of IC
- Designing Isolated Flyback Converter Circuits: Selecting Critical Components – IC Settings Etc.
- Designing Isolated Flyback Converter Circuits: Addressing EMI and Output Noise
- Example Board Layout
- Summary
- Overview of Design Examples of AC-DC Non-isolated Buck Converters
- What are Buck Converters? – Basic Operation and Discontinuous Mode vs. Continuous Mode
- Selection of Power Supply ICs and Design Examples
- Selecting Critical Components: Input Capacitor C1 and VCC Capacitor C2
- Selecting Critical Components: Inductor L1
- Selecting Critical Components: Current Sense Resistor R1
- Selecting Critical Components: Output Capacitor C5
- Selecting Critical Components: Output Rectifying Diode D4
- EMI Countermeasures
- Board Layout and Summary
- Introduction
- Design Procedure
- IC Used in Design
- Power Supply Specifications and Replacement Circuit
- Synchronous Rectifying Circuit Section: Selection of Synchronous Rectifying MOSFET
- Synchronous Rectification Circuit Section: Power Supply IC Selection
- Synchronous Rectification Circuit Section: Selection of Peripheral Circuit Components-C1, R3 at MAX_TON Pin, and VCC Pin
- Synchronous Rectification Circuit Section: Selection of Peripheral Circuit Components-D1, R1, R2 at DRAIN Pin
- Shunt Regulator Circuit Section: Selection of Peripheral Circuit Components
- Troubleshooting ①: Case When Secondary-Side MOSFET Suddenly Turns OFF
- Troubleshooting ②: Case When Secondary-Side MOSFET Turns On Due to Resonance Under Light Loading
- Troubleshooting ③: Case When, Due to Surge, VDS2 Rises to Above Secondary-Side MOSFET VDS Voltage
- Comparison of Efficiency of Diode Rectification and Synchronous Rectification
- Points to Note Relating to PCB Layout
- Summary
- Introduction
- Power Supply ICs Used in Design: Optimized for SiC MOSFETs
- Design Example Circuit
- Transformer T1 Design – 1
- Transformer T1 Design – 2
- Selecting Critical Components: MOSFET Q1
- Selecting Critical Components: Input Capacitor and Balancing Resistor
- Selecting Critical Components: Switch Setting Resistors for Overload Protection Points
- Selecting Critical Components: VCC-Related Components of Power Supply ICs
- Selecting Critical Components: Components Related to Power Supply IC BO (Brownout) Pins
- Selecting Critical Components: Components Related to Snubber Circuits
- Selecting Critical Components: MOSFET Gate Drive Adjustment Circuit
- Selecting Critical Components: Output Rectifying Diode
- Selecting Critical Components: Output Capacitors, Output Setting and Control Components
- Selecting Critical Components: Current Sense Resistors and Components Related to Detection Pins
- Selecting Critical Components: Components for Dealing with EMI and Output Noise
- PCB Layout Example
- Example Circuit and Component List
- Evaluation Results: Efficiency and Switching Waveform
- Summary
Evaluation
- What are Isolated Flyback Converters Performance Evaluation and Checkpoints?
- Overview and important features of a power supply IC used in example performance evaluation
- Design goals and circuits in performance evaluation
- Performance evaluation using an evaluation board: Measurement method and results
- Critical checkpoint: Output transient response and rising output voltage waveform
- Critical checkpoint: Transformer saturation
- Critical checkpoint: MOSFET VDS and IDS, and rated voltage of output rectifier diode
- Critical checkpoint: Vcc voltage
- Critical checkpoint: Measuring temperature and loss
- Critical checkpoint: Aluminum electrolytic capacitors
- Summary
Product Information
FAQ