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AC/DC

Isolated Flyback Converters: Performance Evaluation and Check Points

Design goals and circuits in performance evaluation

The previous section provided a verification of the power supply IC used for an isolated flyback converter on which performance evaluations were to be conducted. This section provides a verification on the specifications for the power supply circuit to be designed, or on the design goals and the circuit to achieve those goals. For further details on design, see the “Design Edition”. The Evaluation section focuses on the verification of the power supply circuit as a prerequisite to the evaluation process.

Design Goals (Power Supply Specifications)
As a necessary process, before commencing the design of a power supply unit (though not limited to power supplies), we need to establish specifications, or design goals, for the power supply unit to be designed. Obviously the specifications are based upon the requirements imposed by the receiver of power. In this subsection, let us assume that we set the following design goals:

Parameter Min Typ. Max Unit Conditions
Input voltage 90 - 264 VAC -
No load input power - - 50 mW Input:100VAC/230VAC
Output voltage 11.4 12 12.6 V -
Output current 1.5 - - A -
Output ripple voltage - - 100 mV Bandwidth:20MHz
Efficiency 80 - - % Output:12V/1.5A

The input voltage represents specifications that are compatible with the power supply requirements, referred to as “universal input”, prevalent in most countries of the world. A ±10% margin is provided.

The no-load input power means the standby power requirement. In Energy Star, stringent target values are set. In this subsection, we set a sufficiently small value even though it may be outside the range required by Energy Star.

The maximum value of output ripple voltage is set to 100mV, which is deemed low for these types of specifications.

The minimum efficiency is set to 80%, with the goal of creating a high efficiency AC/DC converter.

Design Circuits and Components
For an evaluation circuit, we use the following circuit which is expected to satisfy the design goals; for reference, a list of required components is also provided:


The transformer employed is the YPP1183, details of which are shown below:

Actual PCB
Photographic images of the actual circuit board created using the above circuit and components are shown below. Because the circuit is an AC/DC converter, it contains high-voltage components. Though projecting an image slightly different from newer fully surface-mounted DC/DC converters, it is an extremely compact unit as may be appreciated from the photos.


We conduct an evaluation using this circuit board and determine whether the circuit satisfies the design goals.

Key Points:

・In the actual design process, we evaluate the created circuit to confirm whether the design goals are satisfied.


Power Supply Design Technical Materials Free Download

Power Supply Design Technical Materials Free Download

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