Multi-Output Flyback Power Supply Design

Multiple Outputs – Multiple Options

Half of the power supplies being shipped worldwide are chargers and adapters, among the other half, there’s one thing in common for almost all of them – they are used in electronics systems that require multiple output voltages. Multi-output power supplies are a great way to provide cost-effective, efficient, and flexible solutions for these end customers. Power Integrations offers different multi-output flyback design options to meet different customer needs, ranging from 20W to 244W. This includes the revolutionary single stage InnoMux-2 product family, which >90% overall system efficiency and better than 3% accuracy on all outputs without compromise.

InnoMux-2 - Revolutionary Single-Stage Multi-Output Flyback

Compared to the traditional two-stage architecture for multi-output power supplies, InnoMux-2 simplifies the system into single-stage power conversion. This unique power architecture allows efficiency improvement by 5% to 10% by eliminating the need for any downstream DC/DC converters.

InnoMux-2 offers up to three CV/CC outputs with accurate regulation (+/- 3%) on all output channels, while reducing power subsystem component count by 50%.

InnoMux-2 dramatically improves efficiency by removing downstream DC/DC converters

InnoMux-2 offers accurate regulation on all outputs

InnoMux-2 Power System Overview

Output cross regulation accuracy for a dual-output constant voltage design CV1 (5 V, 1A) & CV2 (12 V, 2.5 A) Test condition: mains input 90 Vrms ~ 265 Vrms, 0% ~ 100% load on CV1 & CV2

Multi-Winding Flyback

The simplest multi-output solution. Designers can easily obtain multiple outputs by having multiple secondary windings on the transformer. Feedback is sensed primarily from one output that can be regulated relatively accurately. The other outputs are regulated through magnetic coupling.

This solution is great for applications where only one output requires accurate regulation.

• Pros: Circuit simplicity, Low cost
• Cons: Less accurate output regulation

Flyback plus DC/DC Post-Regulators

If accurate regulation is required for each of the multiple outputs, downstream DC/DC converters can be introduced.

The additional DC/DC converters ensure accurate output regulation, but come at a cost to efficiency, due to the two-stage power conversion.

• Pros: Accurate regulation on multiple outputs
• Cons: Lower efficiency, extra DC/DC cost, PCB size, Part count