There are many ways to build the Dual DC power supply rectifier from a transformer that has one secondary coil.This good way as Figure 1 use two bridge diodes. The first section is normally working, others section (D1-D4) will work by AC signal from C1 and C2. To filter DC voltage of out others bridge diode of transformer. It cause we can connect directly the positive of to the 0 volts. Thus, the output will be symmetric both positive and negative. And since C3 is charged by impedance higher than C4. Because value of C1 and C2. Thus value of …
This is Multi voltage power supply circuit  as electrical circuit to supply DC power positive and negative. It also has multiple power levels as well. The equipment it easy to buy and affordable. Operation of this circuit, when T1 was to convert the AC voltage from 220 volts down to 15 volts, and D1-D4 connected to circuit Direct Contact bridge rectifier . Will act as a rectifier AC DC Then C1, C2, C5 and C6 serve filtered flows smooth and then, through to the leg 1 (Vin) of IC1 and IC2. By IC1 (LM7812) acts Direct loans isolate pressure for …