This reference design is a 15-W bias power supply with two isolated outputs (12 V/1.125A and 3.3 V/0.3A) and a total standby power consumption of 4 mW under a 220-V 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 maximize efficiency over the entire operating range.
Features
- Enables zero-power standby consumption:
- 3.1 mW at 115-V AC Input
- 4.2 mW at 220-V AC Input
- Average efficiency >84%, exceeds DoE VI and CoC tier 2 specifications
- Primary-side regulation (PSR) eliminates optocoupler and increase reliability of bias power supply
- Resonant-ring valley-switching operation for highest overall efficiency
- Universal input voltage range (85V to 270V AC) to address customer needs across all regions
- Dual isolated outputs of 12V and 3.3V is suitable for most industry applications
- Frequency-dither to ease EMI compliance