What are Isolated Flyback Converters Performance Evaluation and Checkpoints?

This section begins a new “Evaluation Edition” relating to AC-DC converters. Under the title “Isolated Flyback Converters Performance Evaluation and Checkpoints”, the section describes measurement method for evaluating isolated flyback AC-DC converter circuit performance and shows examples of measurement data. In addition, for evaluation, beyond the performance aspects we will discuss critical checkpoints for the verification of whether the circuits are operating successfully.

In the performance evaluation process, the first step would be to understand the features of the power supply IC with which the circuit to be evaluated is constructed. As was explained in the “Design Method of PWM AC-DC Flyback Converters” part of the “Design Edition”, in newer power supply designs an adequate understanding of the power supply IC is an essential requirement.

In succession, we make decisions on design goals for a power supply unit, such as the accuracy of output voltage, and perform a circuit design to achieve those goals. Since the objective of this chapter is to make sure that the reader learns something about evaluation methods, we will skip a discussion of the design itself; nevertheless, we will check out the power supply circuits on which evaluations are to be conducted.

Finally, using the power supply IC evaluation board using that circuit, we will verify whether the design goals have been attained.

In the next section, we explain the checkpoints to ascertain whether the designed circuit is operating correctly and methods that are employed to measure the performance. Although mostly there are no problems if the design goals are attained, mass production cannot be justified and the product cannot be shipped unless margins and potential issues are properly identified. These checkpoints represent the type of experience and skills that goes with the production of a product. The checkpoints make it possible to accurately and quickly uncover potential issues, based upon experience and actual past performance.

• ・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

• AC-DC converter