35W switching power supply circuit having a set-top box output is shown in Figure 5. The five-way voltage respectively: Uo1 (+ 30V, 100mA), Uo2 (+ 18V, 550mA), Uo3 (+ 5V, 2.5A)
, Uo4 (+ 3.3V, 3A), Uo5 (-5V, 100mA). Wherein, + 5V and + 3.3V as the main output, the rest are supplemented by output from various quarters. When the AC input voltage u 220 (1 15%) V, the switching power supply total output power of 38.5W, the use of a wide range of input voltage (u 85 ~ 265V), the total output power is reduced 25W. Can be used as set-top boxes (Set Top Box), video recorder (VCR), camcorder (CVCR) and DVD player in the switching power supply. The set-top boxes switching power supply efficiency above 77%, with under-voltage and over-voltage protection.