How to Design a Simple Isolated Power Supply

Isolated power supplies are needed in a wide variety of applications. Galvanic isolation is achieved by isolating two or more circuits using a transformer or optocoupler, and is desirable for many reasons: safety, noise immunity, circuit protection, etc.

Traditionally, isolated power supplies use an optocoupler to transfer regulation information across the isolation barrier. An optocoupler’s gain characteristic varies widely over temperature and over lifetime and since it appears in the feedback loop, it presents significant challenges with regards to the loop compensation of the power supply. Linear Technology’s LT3573 uses innovative internal circuitry to obsolete the optocoupler, greatly simplifying the design of an isolated flyback converter.

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