Circuit Design of 33W (60 W Peak) Set Top Box / PVR Power Supply

MOS power IC full range

Single chip microcomputer STM32L151CCU6

Summary:

Way of working

The flyback converter shown in the figure uses a device in the PeakSwitch family (U1, PKS606P) to provide 33 W continuous and 60 W peak power.

The U6 internal controller receives the feedback signal from the secondary through U5 and turns on or off the internal integrated MOSFET to maintain regulation according to the feedback signal. A portion of 3.3 V and 5 V is fed into the TL431 (U2), which controls the current flowing through the U5 internal LED. When the output voltage rises above their set threshold, U2 pulls more current from the U5's LED, which increases the base drive of Q1 and increases the current drawn from the U6's EN/UV pin. Once the EN/UV turn-off threshold current is exceeded, the switching cycle is skipped. When the current flowing out of the EN/UV pin is below the threshold current of the shutdown, the switching cycle will start again.

design feature

• Output 60 W peak power using a small, low-cost EF25 core
• Small number of components: only 47
• High efficiency: ≥76% at 33 W
• No-load loss <140 mW
• Meet EN55022 B Conducted EMI Limit

See the PDF document for details (click on the PDF file to download)