Dual Power Supply circuit using Transformers
This is dual power supply using voltage regulator BC547B and Dioda. It’s the best and simplest choice for most non-critical applications. The 3 terminals are input, ground and output. The Dioda can provide up to 1A load current and it have onchip circuitry to prevent damage in the event of over heating or excessive current.
This dual power supply project provides a dual power supply. With the appropriate choice of transformer and 3-terminal voltage regulator pairs you can easily build a small power supply delivering up to one amp at +/- 5V, +/- 9V, +/- 12V, +/- 15V or +/-18V. You have to provide the centre tapped transformer and the 3-terminal pair of regulators you want: 7805 & 7905, 7809 & 7909, 7812 & 7912, 7815 & 7915or 7818 & 7918.
Note that the + and – regulators do not have to be matched: you can for example, use a +5v and -9V pair. However, the positive regulator must be a 78xx regulator, and the negative a 79xx one. We have built in plenty of safety into this project so it should give many years of continuous service.
These protect mainly against any back emf which may come back into the power supply when it supplies power to inductive loads. They also provide additional short circuit protection in the case that the positive output is connected by accident to the negative output. If this happened the usual current limiting shutdown in each regulator may not work as intended. The diodes will short circuit in this case and protect the 2 regulators.