UCC1889 is a switch-mode power supply controller that can be used in transformerless off-line applications and provides ideal primary-side bias supply. It features an efficient BiCMOS design, wide input range and adjustable low voltage output. This device can use low cost SMD inductors and has short circuit protection and optional isolation capability.
The document describes the UCC 1889 family of controllers (UCC1889, UCC2889, UCC3889), which are optimized for use as off-line, low power, low voltage regulated bias supplies. The unique circuit topology utilizes two cascaded flyback converters driven from a single external power switch to achieve voltage conversion ratios of 400V to 12V without a transformer.
| Input Voltage Range | 100-400V DC |
|---|---|
| Output Voltage (Fixed) | 12V or 18V |
| Operating Temperature Range (UCC1889) | -55°C to +125°C |
| Operating Temperature Range (UCC2889) | -40°C to +85°C |
| Operating Temperature Range (UCC3889) | 0°C to 70°C |
It is optimized for use as an off-line, low power, low voltage regulated bias supply.
No, it achieves voltage conversion ratios of 400V to 12V with no transformer.
It offers inherent short circuit protection because as the output voltage falls to zero, the switch off time approaches infinity.