Dual isolated output bias power supply with low standby consumption
This reference design from Texas Instruments is a 15W bias power supply with two isolated outputs (12 V/1.125A and 3.3 V/0.3A) and a total standby power consumption of 4mW under a 220V AC input. The controller uses primary-side regulation (PSR) and detects a wake-up signal from the UCC24650 secondary-side voltage-droop monitor for improved transient response to large load steps.
This reference design demonstrates how the UCC28730 can provide ultra-low standby power without sacrificing start-up time or output transient response with an internal 700-V start-up switch, dynamically controlled operating states, and a tailored modulation profile.
The UCC28730 uses frequency modulation, peak primary current modulation, valley switching, and valley skipping in its control algorithm to maximise efficiency over the entire operating range.
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