AC-DC｜Design
Introduction
2018.05.10
Points of this article
・Design example of a quasi-resonant isolated AC-DC converter
・A SiC MOSFET is used as a power switch.
We begin a new chapter in the edition on AC-DC converter design, “Design Example of Isolated Quasi-Resonant Converters Using SiC MOSFET”. In this chapter, in succession to the previously discussed flyback design and forward design, we shall describe in detail an isolated AC-DC converter design that uses a “quasi-resonant” type power supply IC.
Further, SiC (silicon carbide) MOSFETs are used as power switches. SiC is a next-generation semiconductor material with lower losses and superior operating characteristics at elevated temperatures compared with Si semiconductors. Upon hearing SiC semiconductors mentioned, the reader may assume some special applications that handle large amounts of power, but they can also contribute to energy efficiency and miniaturization in many ordinary applications as well. SiC semiconductors have already reached the stage of commercialization, and are even being adopted in automotive equipment, where strict demands are made regarding quality and reliability. Detailed information on SiC power devices is also provided on the Tech Web website for basic knowledge, and the reader is encouraged to read the relevant information on that site.
In this chapter, we plan to address the following issues.
＜Design Example of Isolated Quasi-Resonant Converters Using SiC MOSFET＞
- Power supply ICs used in design
- Transformer design
- Selecting critical components
- Addressing EMI
- Addressing output noise
- Example board layout
- Evaluation
Below is an AC-DC converter obtained from this design case study. It should be noted that the power supply IC is mounted at the position of the red circle on the rear surface, and the SiC MOSFET is mounted in the orange circle on the top surface.
Example of an isolated quasi-resonant AC-DC converter using as a power supply IC the BD7682FJ,
and as a SiC MOSFET the SCT2H12NZ
Next time, we will be explaining the power IC used in the design and quasi-resonant devices.
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
- Extra Plus Basic Knowledge
Design
-
Overview of Design Method of PWM AC-DC Flyback Converters
- Isolated Flyback Converter Basics: Flyback Converter Operation and Snubber
- Isolated Flyback Converter Basics: What are Discontinuous Mode and Continuous Mode?
- Want are Isolated Flyhback Convertors?
- Design Procedure
- Isolated Flyback Converter Basics: What is Switching AC-DC Conversion?
- Determining Power Supply Specifications
- Designing Isolated Flyback Converter Circuits
- Isolated Flyback Converter Basics: What are Characteristics of Flyback Converter?
- Designing Isolated Flyback Converter Circuits: Transformer Design (Calculating numerical values)
- Choosing an IC for Design
- 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
- Troubleshooting ①： Case When Secondary-Side MOSFET Suddenly Turns OFF
- Synchronous Rectification Circuit Section: Selection of Peripheral Circuit Components－C1, R3 at MAX_TON Pin, and VCC Pin
- 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
- Synchronous Rectification Circuit Section: Selection of Peripheral Circuit Components－D1, R1, R2 at DRAIN Pin
- Shunt Regulator Circuit Section: Selection of Peripheral Circuit Components
-
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: Measuring temperature and loss
- Critical checkpoint: Aluminum electrolytic capacitors
- Summary
- Critical checkpoint: Transformer saturation
- Critical checkpoint: MOSFET VDS and IDS, and rated voltage of output rectifier diode
- Critical checkpoint: Vcc voltage
Product Information
FAQ