MOS power IC full range

inductance

SMD aluminum electrolytic capacitor

Bring back a desktop computer from abroad. In use, it is damaged due to overvoltage in the city. Check the power supply and find that there are 115V and 230V two-way mains voltage selection switch. The circuit schematic is shown in the drawing.
When the SI is disconnected, the mains supply 220V is selected. Select the mains 110V when closed. The circuit is very simple.

When the SI is disconnected, it is suitable for 220V of the mains. Bridge rectification is filtered by CI and C2 in series, and the equivalent capacitance is 680uF/2=340uF. If the two capacitors have the same capacity. Then each capacitor is subjected to Um/2=155V DC voltage. The RL terminal voltage is 310V.

'SI is applied to the mains IIOV when it is connected. It is from L to Dl, CI, SI to N. Charging CI can be charged to about 155V: one channel in the positive half cycle: from L through DI, RL, C2, S1 to N. Power the RL.

Negative half cycle from N through C2, D4 to L. Charging C2 can also be charged to about 155V; there is also a path in the negative half cycle: from N through S1, C1, RL, D4 to L, to supply power to the RL.
The voltage across the load RL is the voltage after the CI and C2 terminals are connected in series, about 310V. It can be seen that the mains electricity is 220V or IIOV. After the correct switching of the switch S, the voltage across the load is approximately 310V.

When SI is closed, we call it voltage doubler rectification. D2 and D3 withstand a back pressure of about 155V, always in the off state, and they are not involved in the work.