Stepdown-omvandlare med låg tomgångsförlust

Sammanfattning: A power supply unit with very low standby losses has been constructed. A reference design from Texas Instrument was used as a comparison and starting point. A choice between optimizing the existing reference design or creating a new power supply was made. The losses in the reference design was located to be due to high switching frequency. This also led to losses in the snubber circuit. Because the reference design has an inefficient external start-up circuit and does not allow load dependent switching frequency without an complicated modification, a new power supply was decided to be constructed. The fly- back controller used was the integrated circuit UCC28730, which has a built-in start-up circuit and a load dependent switching frequency function. To implement faster commu- nication between the output and the flyback controller the integrated circuit UCC24650 was added to the design. This allows the UCC24650 to send wake-up signals when a volt- age droop is detected on the secondary side. The new power supply has a built-in under voltage protection to protect the batteries which is the power source. Although the new power supply seems to regulate the desired output voltage during no load, it does seem to have issues with faults during both no load and load.